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Publisher: Center odličnosti NAMASTE, zavod za raziskave in razvoj naprednih nekovinskih materialov s tehnologijami prihodnosti Centre of Excellence NAMASTE, Advanced Materials for the Future Jamova cesta 39 SI - 1000 Ljubljana SLOVENIA T: +386 (0)590 54 356 F: +386 (0)590 54 355 www.coNAMASTE.si Editor: Janez Štrancar Design: Janez Štrancar Lecturing: Paul McGuiness Print: Infokart d.o.o. December 2012

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ACKNOWLEDGMENTS

This booklet was the idea of Centre of Excellence NAMASTE Director, Prof. Dr. Marija Kosec. The project leaders and their teams created the materials presented on the following pages, telling the story of a successful collaboration between interdisciplinary teams connecting the research, development and industrial worlds. CoE NAMASTE would like to thank the project leaders and their teams, and the Centre’s management team, who all contributed to the creation of this publication, and whose assistance was crucial to the preparation of this document. We are especially grateful to Prof. Dr. Janez Štrancar for all his efforts in editing and designing.

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TABLE OF CONTENTS

PREFACE PREDGOVOR PREDSTAVITEV CENTRA ODLIČNOSTI NAMASTE INTRODUCTION TO THE CoE NAMASTE CENTER ODLIČNOSTI V ŠTEVILKAH CoE IN NUMBERS EVALVACIJA CENTRA ODLIČNOSTI NAMASTE EVALUATION OF CoE NAMASTE ZNANSTEVENE IN TEHNOLOŠKE POVEZAVE SCIENTIFIC & TECHNOLOGICAL RELATIONS PRENOS ZNANJA IN TEHNOLOGIJ DISSEMINATION OF KNOWLEDGE

CERAMIC 2D & 3D STRUCTURES LTCC MATERIALS AND TECHNOLOGY FUNCTIONAL MATERIALS LTCC-BASED CERAMIC PIEZORESISTIVE PRESSURE SENSORS CERAMIC MICRO REACTORS

OVERVOLTAGE AND EM PROTECTION LOW-DOPED ZNO-BASED VARISTOR CERAMICS THERMAL CHARACTERIZATION OF VARISTORS AND THE DEVELOPMENT OF VARISTORS FOR “DC” APPLICATIONS GAS-DISCHARGE TUBES ELECTROMAGNETIC WAVE ABSORPTION OF POLYMER NANOCOMPOSITES BASED ON FERRITE NANOFLUIDS FOR APPLICATIONS IN MAGNETIC HYPERTHERMIA

ADVANCED SENSING

6 7 8 9 10 11 12 13 14 15 16 17

19 22 24 26 28

31 34 36 38 40 42

45

INTEGRATED POLYMER-BASED CAPACITIVE AND LOW-POWER GAS SENSOR FOR REMOTE SENSING OF CHEMICAL AGENTS FABRICATION OF SILICON MICROSTRUCTURES BY DRIE SENSOR SYSTEM FOR VAPOR TRACE DETECTION OF EXPLOSIVES PRECISION ELECTRONIC WATT-HOUR ENERGY METER WITH BIST THz SYSTEM / CAMERA DEMONSTRATOR

4

48 50 52 54 56


SOFT COMPOSITES

59

NEMATIC COLLOIDS: ASSEMBLING TOPOLOGICAL SOFT MATTER NEMATIC DROPLETS AS TUNABLE OPTICAL MICRORESONATORS LIQUID CRYSTAL MICROLASERS LASER-INDUCED PRINTING OF NEMATIC DEFECTS COLLOIDAL AND CONFINED BLUE PHASES ACTUATION OF LIQUID CRYSTAL ELASTOMERS MOLYBDENUM AND TUNGSTEN BASED NANOMATERIALS LIQUID CRYSTAL LIGHT SHUTTERS FOR PERSONAL PROTECTION

BIOACTIVITY, BIOCOMPATIBILITY

79

NANOPARTICLES AND FOTOEXCITATION TO FIGHT AGAINST BACTERIA MICROSPECTROSCOPIES FOR NANOPARTICLE IN-CELL TRACKING CELLULAR INTERNALISATION OF NANOPARTICLES NANOPARTICLES IN THE ENVIRONMENT BIOMATERIALS: CERAMICS FOR DENTAL APPLICATIONS POLYMER SCAFFOLDS FOR TISSUE ENGINEERING

NEW OPPORTUNITIES

62 64 66 68 70 72 74 76

82 83 86 88 90 92

95

THE INFLUENCE OF PARTICLE SIZE AND OTHER CERAMIC RAW MATERIALS AND CERAMIC SUSPENSIONS ON SINTERED CORDIERITE MATERIALS VIRTUAL LABORATORY FOR MEASUREMENTS OF ELECTROMAGNETIC COMPATIBILITY ELECTROCALORIC MATERIALS

APPENDICES

98 100 102

105

APPENDIX 1 - ORGANIZATION APPENDIX 2 - EQUIPMENT

106 108

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PREFACE Centre of Excellence: Advanced Materials and Technologies for the Future (CoE NAMASTE) is a multi-disciplinary and trans-disciplinary consortium of research institutions and industry, who have decided to merge academic, technological and business expertise, skills, and equipment in order to foster crucial technological progress in selected areas, relating to inorganic nonmetallic materials and their applications in the electronics, optoelectronics, photonics and medical fields. Our strategic goals are: continuity in research excellence, multidisciplinary interconnection, knowledge dissemination and technology transfer. In CoE NAMASTE the research and industrial organizations jointly strive for the creation of new knowledge and its transfer into practice. This should lead to a substantial increase in the added value, research relevance and scientific excellence. The active collaboration of research and industrial partners enables a better flow of information and fosters the exchange of ideas, resulting in faster and more effective problem solving in industry and enabling the research community to learn what is important for industry. These processes help business partners deepen the basic knowledge and give access to the newly acquired equipment to all of the partners involved. Enriching new knowledge, the development of new technologies and their successful transfer to products contribute to the retention of existing and the creation of new jobs, higher value added and increased competitiveness. The management of CoE NAMASTE is aware that new knowledge can be created in the close collaboration of research, development and technology, by highly skilled and motivated people, dedicated to research and development excellence. Until now, the activities in CoE NAMASTE had proven that the active involvement of high-tech companies from all over Slovenia contributes to progress in the development of the regions. CoE NAMASTE is an incubator for the development, characterization and implementation of advanced materials. By using intense knowledge transfer between industry and research partners the CoE has promoted technological transfer and innovation, thus enhancing the quality of research and development. The most important strategic goal achieved so far is beyond doubt the strong bond created between the industrial and R&D communities at the institutes and universities. The best researchers and the best companies entered the process of jointly creating new interdisciplinary knowledge, also with the aid of the best infrastructure available. The performance of the CoE, in terms of research results and in terms of organization, has been evaluated as excellent. The CoE brought together a unique combination of research and industrial partners who are in the process of creating important added value for the economy and the country. Prof. Dr. Marija Kosec Director

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PREDGOVOR CoE NAMASTE (NApredni nekovinski MAteriali S TEhnologijami prihodnosti) je multidisciplinarni in transdisciplinarni konzorcij raziskovalnih institucij in industrije. Povezuje akademsko, tehnološko in poslovno znanje ter opremo z namenom doseči ključni tehnološki napredek na področjih anorganskih nekovinskih materialov in njihovo uporabo v elektroniki, optoelektroniki, fotoniki in zdravstvu. Naši strateški cilji so ohranjanje odličnosti na raziskovalnem področju, multidisciplinarno povezovanje, širjenje znanja in prenos tehnologij. CoE NAMASTE povezuje raziskovalne institucije in gospodarske družbe v skupnem prizadevanju po ustvarjanju novih znanj in prenosu znanja v prakso. Namen sodelovanja je ohranjanje in nadgradnja znanstvene, tehnološke in poslovne odličnosti. Intenzivno sodelovanje med raziskovalnimi in industrijskimi partnerji omogoča pretok informacij in idej, s čimer pripomore k hitremu in učinkovitemu reševanje problemov v industriji na eni strani, na drugi strani pa raziskovalci spoznavajo, kaj je za industrijo pomembno. Podjetja pridobivajo temeljna znanja. V okviru CO so industrijski in raziskovalni partnerji dobili novo opremo, ki je dostopna vsem članom konzorcija. Hitro pridobivanje novih znanj, razvoj novih tehnologij in njihov uspešni prenos v gospodarstvo prispevajo k ohranjanju obstoječih in odpiranju novih delovnih mest, večji dodani vrednosti in krepitvi konkurenčnosti. Vodstvo CoE NAMASTE se zaveda, da je ustvarjanje novega znanja mogoče doseči samo s sodelovanjem raziskovalcev, razvojnikov in strokovnih sodelavcev, ki so usposobljeni in motivirani za izvajanje vrhunskega raziskovalnega in razvojnega dela. V dosedanjem delovanju Centra odličnosti NAMASTE se je izkazalo, da povezovanje visokotehnoloških podjetij iz celotne Slovenije zelo pozitivno učinkuje na regionalni razvoj. CoE NAMASTE deluje kot pravi inkubator razvoja, karakterizacije ter uporabe naprednih materialov. Z intenzivnim prenosom znanja med industrijskimi partnerji in raziskovalnim okoljem smo spodbudili tehnološki razvoj in inovativnost, ter povečali kvaliteto raziskovalno-razvojne dejavnosti. Najpomembnejši strateški cilj, ki ga je CoE NAMASTE nedvomno dosegel, je stkana vez med gospodarstvom in raziskovalno-razvojno sfero na fakultetah in institutih. V Centru sodelujejo najboljši raziskovalci in najboljši gospodarski subjekti, uporabljajo vrhunsko raziskovalno opremo, in ustvarjajo nova interdisciplinarna znanja. Po mnenju sodelujočih Center deluje v organizacijskem in raziskovalnem smislu odlično. Je izjemna kombinacija raziskovalnih in industrijskih partnerjev in pomembna dodana vrednost za gospodarstvo in državo. Prof. dr. Marija Kosec Direktorica

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PREDSTAVITEV CENTRA ODLIČNOSTI NAMASTE CoE NAMASTE raziskovalci delujejo na naslednjih področjih:             

Fizika trdne snovi Teoretična fizika Biofizika Zoologija in zoofiziologija Kemija Biokemija in molekularna kemijska tehnologija Materiali Anorganski nekovinski materiali Elektronske komponente in tehnologije Elektronske komponente in materiali za elektronske komponente Karakterizacija elektronskih komponent in materialov Tekstilna in tehnična vlakna Mikrobiologija in imunologija

Nekateri znanstveni dosežki:  381 znanstevenih člankov (103 z afiliacijo CoE NAMASTE),  25 patentnih prijav (5 z afiliacijo CoE NAMASTE)  856 prispevkov na konferencah in objavljenih povzetkov na konferencah (229 z afiliacijo CoE NAMASTE)

Center odličnosti NAMASTE je zasebni raziskovalni zavod, ki je bil ustanovljen 15. 12. 2009 na osnovi Javnega razpisa za razvoj centrov odličnosti v obdobju 2009-2013 s sklepom Ministrstva za visoko šolstvo, znanost in tehnologijo št.430-36/2009/292 z dne 18. 09. 2009.

zaposlen je zagovarjal magistrsko delo, 4 zaposleni so diplomirali.

Program centra odličnosti je sofinaciran v okviru razvojne prioritete 1. Konkurenčnost podjetij in raziskovalna odličnost in prednostne usmeritve 1.1. Izboljšanje konkurenčnih sposobnosti podjetij in raziskovalna odličnost v okviru Operativnega programa krepitve regionalnih razvojnih potencialov 20072013.

magister znanosti

Izobrazbena struktura zaposlenih doktor znanosti univ. dipl. inž. tehnik Število redno zaposlenih

54 4 23 1 82

*podatki za oktober 2012

Vizija Centra odličnosti NAMASTE je: Postati prepoznavna mednarodno odlična, interdisciplinarna skupina, ki gradi na strateškem partnerstvu med akademsko in gospodarsko sfero in izvaja raziskave, razvoj, izobraževanje ter prenos znanja in tehnologij na prioritetnem področju nekovinski materiali, ki je odprta za povezovanje z ostalimi centri in drugimi. Temelji delovanja so znanstvena, poslovna in raziskovalna odličnost.

V letu 2012 je bilo do konca oktobra opravljenih 27.846 raziskovalnih ur, kar predstavlja 16,38 FTE. Finance Za štiriletno delovanje operacije Centra odličnosti NAMASTE je bilo na podlagi javnega razpisa za razvoj centrov odličnosti dodeljenih 9.417.264 Eur finančnih sredstev. Do novembra 2012 smo v centru dosegli 82,67 % realizacijo, od tega je bilo 52,51 % od celotnih sredstev porabljenih za investicije v raziskovalno opremo.

Zaposleni Center odličnosti NAMASTE zaposluje 82 raziskovalcev, ki svoje znanje in izkušnje iz delovanja na univerzah, institutih in v industriji na različnih raziskovalnih področjih uspešno izmenjujejo in nadgrajujejo v mešanih skupinah.

Znanstveni in tehnološki dosežki Znanstveno in tehnološko odličnost delovanja Centra potrjuje veliko število inovacij in patentov, število prototipov in demonstracijskih projektov. Center ima izjemno število objav v prestižnih tujih revijah kot so Proc. Nat. Acad. Sci. USA, Nature Comm., Phys. Rev. Lett., or Chem. Comm.

Center odličnosti NAMASTE igra pomembno vlogo pri izobraževanju novih kadrov, kar dokazujejo naslednji podatki:

O rezultatih in dosežkih obveščamo tako znanstveno kot širšo javnost v obliki seminarjev, predavanj, delavnic, javnih predstavitev.

Sodelavci centra so bili mentorji pri 13 magistrskih delih in 26 doktorskih disertacijah. V času delovanja centra je 5 zaposlenih uspešno doktoriralo, 1

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INTRODUCTION TO THE CoE NAMASTE The Centre of Excellence NAMASTE was founded as a private research institution on 15 December 2009 as a result of a public tender for centres of excellence for the period 2009-2013 by the decree of the Ministry for Higher Education, Science and Technology, No. 430-36/2009/292 dated 18 September 2009.

In CoE 13 Master’s degrees and 26 Ph.D. theses were defended. This number includes all the works where CoE members were mentors. Among the members of the CoE 5 Ph.D. studies, 1 Master’s and 4 bachelor’s degrees were defended. Educational Structure of the Employees

The program of the Centre of Excellence is co-financed in the frame of development priority 1: Business competitiveness and research excellence, and priority 1.1. Improvement of competitiveness of the enterprises and research excellence in the framework of Operational program for enhancing regional development potential 2007-2013.

Ph. D.

54

M. Sc.

4

B. Sc.

23

Technician Employees Total

1 82

Researchers represent the following areas:                

Solid State Physics Theoretical Physics Biophysics Zoology and Zoophysiology Chemistry Biochemistry and Molecular Chemical Engineering Materials Inorganic non-metal Materials Electronic Components&Technologies Materials for Electronic Components Electronic Components Elect. Comp.& Technol./ME Charact. of electronic comp.& mat. Textile and Technical Fibers Microbiology and Immunology

*Data for October 2012

The vision of the CoE NAMASTE is to become an outstanding, internationally recognized excellent interdisciplinary group that builds on the strategic partnerships of the academic and business sphere, conducting research, development, education and the transfer of knowledge and technology in the priority field of non-metallic materials, being opened for further collaboration with other centres and other interested parties. Maintaining and constantly upgrading our excellence in research, technology and business are the important guidelines.

Up until the end of October 2012, 27,846 research hours have been conducted, that is 16,38 FTE.

Personnel

The technological excellence of this CoE NAMASTE is demonstrated by the number of innovations and patents achieved so far, as well as by the number of prototypes and demonstration projects. The number of publications is remarkable, and so is the ranking of the journals which have been chosen for publication, including Proc. Nat. Acad. Sci. USA, Nature Comm., Phys. Rev. Lett., and Chem. Comm.

Budget CoE NAMASTE was granted financing for 4 years of operation, based on a public tender for the development of centres of excellence, in the amount of €9,417,264. Up until November 2012, 82.67% was realized, of which 52.51 % was investments in research equipment. Scientific and technological results

The CoE NAMASTE is the employer of 82 researchers, who in mixed teams successfully share and exchange their knowledge and best practices from their work at the universities, institutes or industry from various research areas. Within the CoE a great deal of attention is paid to the education of new coworkers, and also to the dissemination of the results and achievements within and outside of the scientific community.

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Some Scientific Achievements:  381 scientific papers (103 with CoE NAMASTE affiliation),  25 patent applications (5 with CoE NAMASTE affiliation),  856 conference contributions and abstracts (229 with CoE NAMASTE affiliation)


CENTER ODLIČNOSTI V ŠTEVILKAH

Struktura po spolu Ž 29%

M 71%

*podatki za oktober 2012

80,00 70,73 70,00 60,00

%

50,00 40,00 28,05

30,00 20,00 10,00

1,22

0,00 Dr., Mag.

Univ. dipl.

Izobrazbena struktura *podatki za oktober 2012

10

Tehniki


CoE IN NUMBERS

Structure by gender F 29%

M 71%

*October 2012

80,00

70,73

70,00

60,00

%

50,00 40,00

28,05

30,00 20,00 10,00

1,22

0,00

PhD, MSc.

B.Sc.

College

Educational structure *October 2012

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EVALVACIJA CENTRA ODLIČNOSTI NAMASTE Evalvacija Centra odličnosti NAMASTE je potekala 20. julija 2011 na Odseku za elektronsko keramiko (K5) Instituta »Jožef Stefan« v Ljubljani. Direktorica Centra prof. dr. Marija Kosec in vodje projektov so evalvatorju v uvodnem predavanju predstavili center in njegovo delovanje. V nadaljevanju je evalvator obiskal več laboratorijev na lokacijah.

Izjava tujega recenzenta: 1. Iz predstavitve v vmesnem poročilu, kot tudi iz številnih skupnih publikacij je jasno vidno, da je sodelovanje industrijskih partnerjev in akademskih partnerjev v tem Centru močno in uspešno, čeprav včasih le dvostransko. Zdi se, da je mogoče številne tehnologije in proizvode, razvite pri raziskovalnih organizacijah v okviru tega Cetra uspešno prenesti industrijskim partnerjem. Tehnološka odličnost tega Centra je jasno razvidna iz dosedanjih dosežkov kot so število inovacij in patentov, število prototipov in demonstracijskih projektov. Število objav je izjemna, kakor tudi njihova uvrstitev v revijah kot so: Proc. Nat. Acad. Sci. USA, Nature Comm., Phys. Rev. Lett., or Chem. Comm.

Evalvator je na Institutu »Jožef Stefan« v Ljubljani obiskal laboratorije na Odseku za elektronsko keramiko, na Odseku za fiziko trdne snovi je obiskal Laboratorij za mehke snovi in AFM, Laboratorij za biofiziko ter Laboratorij za sintezo anorganskih nanocevk in vrvi. Na Fakulteti za elektrotehniko je obiskal Laboratorij za mikrosenzorske strukture in elektroniko ter Laboratorij za mikroelektroniko.

2. CoE NAMASTE je v prvem obdobju pokazal resnično odlično delovanje. Organizacijska struktura, ki je bila vzpostavljena in se izvaja, omogoča učinkovito delovanje tega centra odličnosti.

Evalvatorju je Center odličnosti NAMASTE pred obiskom poslal standardiziran obrazec za samooceno, ki je bil evalviran že pred obiskom evalvatorja. Ministrstvo za visoko šolstvo, znanost in tehnologijo je za vmesno evalvacijo poslalo v pregled evalvatorju številčne kazalnike.

3. Center odličnosti NAMASTE ima odlično ravnovesje med temeljnimi in aplikativnimi raziskavami, kar mu daje posebno moč. Medtem, ko aplikativne raziskave prinašajo rešitve, ki jih je mogoče prenesti v tehnične proizvode ali storitev v razmeroma kratkem času, so temeljne raziskave podlaga za tehnologije prihodnosti.

Na podlagi pregleda vseh indikatorjev, razgovorov z vodji in raziskovalci, ogledov laboratorijev in nazornih prikazov rezultatov je evalvator podal priporočilo za nadaljnje financiranje in delovanje Centra odličnosti NAMASTE, kar je veliko priznanje zaposlenim v Centru in njihovemu delovanju.

Slika 0.1:

Uvodni sestanek ob evalvaciji Centra odličnosti NAMASTE // Introductory meeting at the evalvation of CoE NAMASTE

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EVALUATION OF CoE NAMASTE The evaluation of CoE NAMASTE took place on 20 July 2011 at the Electronic Ceramics Department (K5) at the Jo탑ef Stefan Institute in Ljubljana. The Director of CoE Prof. Dr. Marija Kosec and the project leaders gave an introductory lecture to the evaluator and presented CoE NAMASTE and its operation. The evaluation continued with several extended site visits to the laboratories. At the Jo탑ef Stefan Institute, Ljubljana the evaluator visited laboratories at the Electronic Ceramics Department, Atomic Force and Soft Matter Laboratory, Laboratory for Biophysics, and Laboratory for Synthesis of Inorganic Nanotubes and Ropes at Department of Solid State Physics. At the University of Ljubljana he visited the Faculty of Electrical Engineering (Laboratory for Microsensor Structures and Electronics and Laboratory for Microelectronics).

Foreign reviewer statements: 1. From the presentations during the midterm evaluation, as well as from the numerous joint publications it becomes clear that the cooperation of industrial partners and academic partners within this CoE is strong and successful even if often only in a bilateral way. It appears that many of the technologies and products developed at the research partners within this CoE can be transferred successfully to the commercial (industrial) partners. The technological excellence of this CoE NAMASTE is clearly demonstrated by the number of innovations and patents achieved so far as well as by the number of prototypes and demonstration projects. The number of publications is remarkable and so is the rank of the journals which have been chosen for publication, including Proc. Nat. Acad. Sci. USA, Nature Comm., Phys. Rev. Lett., or Chem. Comm. 2. CoE NAMASTE has demonstrated during the first period of operation a truly excellent performance. The organisational structure was established and implemented, and allowed for the frictionless and efficient operation of this Centre of Excellence.

A standardised, self-assessment form was prepared and distributed by the evaluator before the site visit, and the answers to this self-assessment were prepared in advance of the site visit. Also, an overview of the numerical indicators for the mid-term assessment of the CoEs was provided by the Ministry of Higher Education, Science and Sport of the Republic of Slovenia, supporting the evaluators in their work.

3. It is a particular strength of this CoE that it has an excellent balance between fundamental and applied research. While the applied research delivers solutions that can be transformed into technical products or services on a relatively short timescale, fundamental research will provide the basis for future technologies which not necessarily can already be anticipated at the current time.

Based on all the indicators of the performance of the CoE, interviews of the evaluator with the project leaders and researchers, site visits and results demonstration, a recommendation for continuing of the funding of the operation of CoE NAMASTE was given by the evaluator, which is valuable recognition for the employees in the Centre and their functioning.

Slika 0.2:

Obiski na lokacijah: IJS, Odsek za fiziko trdne snovi (levo); UL, Fakulteta za elektrotehniko (v sredini); IJS, Laboratorij za biofiziko (desno) // Visiting locations at IJS: Condensed matter physics department (left); UL; Faculty of electrical engineering (in the middle); IJS: Laboratory of Biophysics

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ZNANSTVENE IN TEHNOLOŠKE POVEZAVE tehnologij in izdelkov, nastalih v okviru centra mogoče uspešno prenesti na industrijske partnerje.

Sinergije Partnerji: RAZISKOVALNE INSTITUCIJE:  Institut »Jožef Stefan« o Odsek za elektronsko keramiko (IJS-K5) o Odsek za nanostrukturne materiale (IJS-K7) o Odsek za fiziko trdne snovi (IJS-F5) o Odsek za inženirsko keramiko (IJSK6)  Univerza v Ljubljani o Fakulteta za elektrotehniko o Fakulteta za matematiko in fiziko o Biotehniška fakulteta o Veterinarska fakulteta o Medicinska fakulteta o Fakulteta za kemijo in kemijsko tehnologijo  Univerza v Mariboru o Fakulteta za kemijo in kemijsko tehnologijo NEPROFITNE RAZVOJNORAZISKOVALNE ORGANIZACIJE:  HIPOT-RR, d.o.o.  ZAVOD TC SEMTO  NANOTESLA INSTITUT PODJETJA IN USTANOVE:              

ISKRA AVTOELEKTRIKA d.d. TELA MERILNI SISTEMI d.o.o. ISKRAEMECO d.d. ETI Elektroelement d.d. HYB d.o.o. KEKON d.o.o. KEKO – OPREMA d.o.o. VARSI d.o.o. ISKRA ZAŠČITE d.o.o. KOLEKTOR MAGMA d.o.o. BALDER d.o.o. NANOTUL d.o.o. SKUPINA PANVITA OBRTNO-PODJETNIŠKA ZBORNICA SLOVENIJE

Uspešno sodelovanje z večino naših industrijskih partnerjev je potekalo že pred ustanovitvijo centra. Novi projekti so bili oblikovani na podlagi dobrih izkušenj in dobre eksterne ocene tujega recenzenta (nekdanji Center odličnosti za materiale in elektroniko prihodnjih generacij je bil ocenjen med 5 % najboljših centrov v Evropi).

Projekti V centru smo poskrbeli za posodobitev raziskovalne infrastrukture. Do sedaj smo kandidirali za en nov projekt v okviru 7. okvirnega programa EU in en projekt v okviru Javne agencije RS za raziskovalno dejavnost. V okviru projekta projekta RRP6 – projekt novih možnosti, ki omogoča vključevanje novih partnerjev, poteka projekt s partnerjem Zavodom TC SEMTO imenovan "Virtualni EMC laboratorij". Cilj tega projekta je izboljšati pogoje za meritve, testiranja in s pomočjo povezovanja znanja, opreme in postopkov poskušati rešiti razvojno-raziskovalne probleme na področju EMC.

Glavni kriterijii pri izbiri naših partnerjev so bili povezovanje različnih raziskovalnih področij, podjetij, regij in nenazadnje znanstvena, tehnološka in poslovna odličnost. Vsi projekti se izvajajo skupaj v sinergiji s partnerji iz poslovnega, zasebnega sektorja. V nadaljevanju predstavljamo povezave med raziskovalnimi projekti in industrijskimi partnerji: - Hyb d.o.o., HIPOT-RR d.o.o., Kekon d.o.o., KEKO-OPREMA d.o.o. (RRP1)  Varsi d.o.o., Iskra Zaščite d.o.o., Kolektor Magma d.o.o., Nanotesla Institut (RRP2)  Iskra Avtoelektrika d.d., TELA Merilni instrumenti d.o.o., Iskraemeco d.d. (RRP3)  Balder d.o.o., Nanotul d.o.o. (RRP4)  Skupina Panvita (RRP5)  ETI Elektroelement d.d., Zavod TC SEMTO (RRP6)

Poleg zgoraj naštetih zaposleni in partnerji v Centru sodelujemo ali koordiniramo veliko mednarodnih projektov, kar kaže na močne mednarodne vezi, ki jih ima naš konzorcij.

V Centru odličnosti NAMASTE je sodelovanje industrijskih in akademskih partnerjev močno in uspešno, kar je razvidno iz številnih objavljenih, skupnih publikacij, zato je veliko

Slika 0.3:

Partnerji CoE NAMASTE so iz različnih delov Slovenije, kot je prikazano na zemljevidu.

Slika 0.4: 2. redna seja Sveta zavoda in 2. redna seja ustanoviteljev CoE NAMASTE.

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SCIENTIFIC & TECHNOLOGICAL RELATIONS and products developed at the research partners within CoE can be transferred successfully to the industrial partners.

Partners and synergies There is a history of successful collaboration between most partners and various research groups. The new projects were, therefore, designed on the basis of good experience and confidence (the former CoE Materials for Electronics of Future Generations and Other Emerging Technologies was ranked among the top 5 % in Europe, as recognized by the foreign reviewer).

Domestic and International Projects At present the CoE is the partner in one project funded by the Slovenian research agency, while CoE has submitted a proposal for a new EU project within the 7th Framework Programme and one project for the Slovenian research agency.

The main criteria in selecting our partners were connecting various research fields, companies, regions and scientific-technological-business excellence. All of the projects are carried out with partners from the business/private sector. The relations between research projects and industrial partners are presented as follows:

Within the Project RRP6, the project of new opportunities, which allows the inclusion of new partners, one project is running with TC SEMTO called “Virtual EMC Lab". The main goal is to improve the conditions for measurements, testing and solving research and development problems in the field of EMC by connecting knowledge, equipment and procedures.

 Hyb d.o.o., HIPOT-RR d.o.o., Kekon d.o.o., KEKO-EQUIPMENT d.o.o. (RRP1)  Varsi d.o.o., Iskra Zaščite d.o.o., Kolektor Magma d.o.o., Nanotesla Institut (RRP2)  Iskra Avtoelektrika d.d., TELA Merilni instrumenti d.o.o., Iskraemeco d.d. (RRP3)  Balder d.o.o., Nanotul d.o.o. (RRP4)  Panvita (RRP5)  ETI Elektroelement d.d., TC SEMTO Institution (RRP6)

It is important to notice that CoE employees and partners are participating or coordinating several international projects. This indicates the strong international relations of the CoE project consortium.

The cooperation of industrial partners and academic partners within CoE is strong and successful, as can be seen from numerous joint publications. It is evident that many of the technologies Figure 0.5: The locations of the partners of CoE NAMASTE are shown on the map of Slovenia.

Figure 0.6: 2nd meeting of CoE Council and 2nd meeting of representatives of the research institutions and industrial partners.

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Partners: RESEARCH INSTITUTIONS:  Jožef Stefan Institute o Department of Electronic Ceramics (JSI-K5) o Department of Nanostructured Materials (JSI-K7) o Department of Solid State Physics (JSI-F5) o Department of Engineering Ceramics (JSI-K6)  University of Ljubljana o Faculty of electrical Engineering o Faculty of Mathematics and Physics o Faculty of Biotechnics o Veterinary Faculty o Medical Faculty o Faculty of Chemistry and Chemical Technology  University of Maribor o Faculty of Chemistry and Chemical Technology NON-PROFIT R & D ORGANIZATIONS:  HIPOT-RR, d.o.o.  INSTITUTE TC SEMTO  NANOTESLA INSTITUTE COMPANIES AND ORGANIZATIONS:              

ISKRA AVTOELEKTRIKA d.d. TELA MERILNI SISTEMI d.o.o. ISKRAEMECO d.d. ETI Elektroelement d.d. HYB d.o.o. KEKON d.o.o. KEKO – EQUIPMENT d.o.o. VARSI d.o.o. ISKRA ZAŠČITE d.o.o. KOLEKTOR MAGMA d.o.o. BALDER d.o.o. NANOTUL d.o.o. GROUP PANVITA THE CHAMBER OF CRAFT AND SMALL BUSINESS OF SLOVENIA


PRENOS ZNANJA IN TEHNOLOGIJ tesno sodelovanje s člani konzorcija kot tudi z drugimi centri odličnosti pri spodbujanju in izmenjavi dobrih praks, oblikovanju in prenosu novega znanja na področju znanstvenih raziskav in tehnologije. Verjamemo, da je ohranjanje in izboljšanje raziskovalne, tehnološke in poslovne odličnosti ključ do večjih prebojev in ustvarjanju večje dodane vrednostje za uspešno gospodarstvo v prihodnosti.

CoE NAMASTE je (so)organiziral naslednje dogodke:  2 strateški konferenci (80 udeležencev),  1 planska konferenca (69 udeležencev: člani in partnerji),  2 sestanka z ministrom za visoko šolstvo in znanost (preko 200 udeležencev)  3 mednarodne konference Confined Liquid Crystals, Rare-Earth Permanent Magnets and their Applications – and MIDEM (preko 350 udeležencev)  3 konference: Senzorji in aktuatorji, Raziskovanje interakcij med celicami in materiali (3 tuji udeleženci), študentska konferenca Mednarodne podiplomske šole Jožefa Stefana  1 delavnica o karakterizaciji materialov na Rogli (105 udeležencev)  Konferenca v Iskra TELA – raziskovanje novih idej za razvoj (30 udeležencev)  Vabljeno predavanje direktorice CoE NAMASTE prof. dr. Marije Kosec v Državnem zboru Republike Slovenije  CoE NAMASTE je bil član Slovenske delegacije v Braziliji  3 člani CoE NAMASTE so bili člani Slovenske delegacije v Izraelu in so sodelovali na konferenci NANOISRAEL 2010 v Tel Avivu  CoE NAMASTE industrijski partner Nanotesla Institut je bil nagrajen na 5. slovenskem forumu inovacij  20 predavanj tujih vabljenih profesorjev in raziskovalcev (preko 400 udeležencev)  1 seminar Moderne termo-analitske tehnike in njihova uporaba (45 udeležencev)  3 predavanja na mednarodni konferenci Innovation 2011 (slovensko-izraelsko sodelovanje)  4 predstavitve CoE NAMASTE na razstavnih prostorih: Konferenca Inovativnost 2011, Mednarodni obrtni sejem v Celju (2011, 2012), Ljubljanski obrtni sejem (2011)  soorganizacija 9. nanotehnološkega dne skupaj z Obrtno podjetniško zbornico Slovenije in centrom odličnosti NANOCENTER

Slika 0.8:

Slika 0.7:

Vabljeno predavanje direktorice Centra odličnosti NAMASTE prof. dr. Marije Kosec v Državnem zboru Republike Slovenije

Smo ekološko ozaveščeni

Prenos znanja, med drugim tudi predavanja in poučevanje, so v Centru zelo pomembna dejavnost. Center je organiziral in soorganiziral številne dogodke: strateške konference, seminarje, domače in mednarodne konference, različne predstavitve za industrijske partnerje za raziskovanje novih idej za razvoj, vabljena predavanja ipd. Direktorica Centra odličnosti NAMASTE je imela vabljeno predavanje v Državnem zboru Republike Slovenije. V novembru 2011 smo organizirali delavnico Karakterizacija materialov na Rogli. Predstavljenih je bilo veliko zanimivih tem: optična mikroskopija, SEM, TEM, XRD, AFM in laserska pinceta, detektor nanodelcev, Kelvinova sonda, FMS, IR in Ramanska spektroskopija in EPR. Delavnice se je udeležilo 105 udeležencev (67 udeležencev iz raziskovalnih organizacij, 25 udeležencev iz industrije, 9 dodiplomskih študentov in 4 podiplomski študentje, skupno več kot 50 % mlajše generacije udeležencev. Naš ključ do uspeha je predanost partnerjev k doseganju strateških ciljev. Dobre rezultate pa prinaša tako

Delavnica raziskovanje interakcij celice in materiala, Brje pri Komnu

Z razvojem novih tehnologij v Centru odličnosti NAMASTE prispevamo delež k manjši porabi energije in čistejšemu okolju. V nadaljevanju navajamo samo nekaj primerov: LTCC keramični materiali omogočajo žganje na precej nižjih temperaturah, kar posledično pripomore k zmanjšanju emisij toplogrednih plinov, uporaba mehkih kompozitnih materialov zmanjšuje količino potrebne energije za delovanje novih naprav, razvijamo varistorsko keramiko in varistorje za DC aplikacije za prenapetostno zaščito energetskih sistemov, ki delujejo na osnovi obnovljivih virov (fotovoltaični sistemi, sončne elektrarne, vetrni turbinski generatorji). Tudi potencialna uporaba elektrokaloričnih materialov v hladilnih sistemih, ki temeljijo na elektrokaloričnem pojavu bo imela veliko prednosti pred sedanjimi hladilnimi sistemi, ki uporabljajo ozonu škodljive pline. Uporaba ne bi samo zmanjšala problema emisij toplogrednih plinov, ampak tudi porabo energije. Dejstvo, da je delovni medij v teh hladilnikih trden, in da ga je mogoče izolirati iz okolice, ga preoblikovati ali reciklirati, je prednost hladilnega sistema, ki temelji na elektrokaloričnem pojavu.

Slika 0.9: CoE NAMASTE je organiziral delavnico Karakterizacija materialov na Rogli.

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DISSEMINATION OF KNOWLEDGE

Figure 0.10: Invited lecture of CoE NAMASTE director Prof. Dr. Marija Kosec in the Slovenian Parliament

The dissemination of knowledge, in particular teaching and lecturing, is an important activity. CoE NAMASTE has organized or coorganized numerous events, such as strategic conferences, seminars, international and domestic conferences, presentation conferences for partners exploring new ideas for development, an invited lecture at the Slovenian Parliament by the CoE Director. In November 2011 CoE NAMASTE organized the workshop entitled Characterization of Materials on Rogla. There were several interesting topics presented: optical microscopy, SEM, TEM, XRD, AFM and laser tweezer, detector of nanoparticles, Kelvin probe, FMS, IR and Raman spectroscopy and EPR. The workshop was attended by 105 participants (67 participants from research organizations, 25 participants from industry, 9 graduate students and 4 postgraduate students), altogether more than 50 % of the young generation. The key to success is a strong commitment of the partners to achieve the strategic goals of CoE NAMASTE. Working closely with the

consortium members and also with other CoEs in order to promote the sharing of good practices, creating and transferring new knowledge in scientific research as well as in technology, shows excellent results. We believe that the maintaining and upgrading of research–technology– business excellence is the key to major breakthroughs in creating highvalue-added products for the economy to be successful in the future. Ecology By developing new technologies the CoE contributes to the reduced consumption of energy and a less polluted environment. For example, LTCC ceramic materials enable firing at substantially lower temperatures, which helps to reduce greenhousegas emissions, the use of soft composite materials will use less energy for the operation of new devices, the development of varistor ceramics and varistors for dc applications in the surge protection of energy systems based on renewable sources (photovoltaic systems, solar power plants, wind turbine generators). The potential use of electrocaloric materials in cooling systems based on electrocaloric phenomenon would have some indisputable advantages over today's cooling systems that use ozone-depleting gases. It would not only reduce the problem of greenhouse-gas emissions but also reduce the energy consumed. The fact that the working media in such refrigerators is solid, which is easily isolated from the environment, reshaped and recycled, is the advantage of a cooling system based on the electrocaloric phenomenon.

Figure 0.11: CoE NAMASTE organized workshop Characterization of materials on Rogla.

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CoE NAMASTE organized or coorganized events:  2 strategic conferences (80 participants),  1 annual planning conference (69 participants: members and partners),  2 meetings with the minister for higher education (over 200 participants)  3 international conferences Confined Liquid Crystals, Rare-Earth Permanent Magnets and their Applications – and MIDEM (over 350 participants)  3 domestic conferences Sensors and Actuators, Exploring Material-Cell Interaction (3 intnl. participants), student conference of Jozef Stefan International Postgraduate School  1 workshop on Characterizion of materials in Rogla (105 participants)  conference at partner Iskra TELA exploring on new ideas for development (30 participants)  invited lecture of director Prof. Dr. Marija Kosec in the Slovenian Parliament  1 member was part of Slovene delegation to Brazilia  3 members were part of Slovene delegation to Israel and participated at NANOISRAEL 2010 conference in Tel Aviv  on 5th Slovene Innovation Forum the member Nanotesla Institute was awarded  20 lectures of international professors and researchers (over 400 participants)  1 seminar Modern thermo-analytical techniques and their applications (45 participants)  3 lectures given at the international conference Innovation 2011 (SLOIsraeli collaboration)  4 exhibitions of CoE: Innovation 2011, International trade fair in Celje (2011, 2012), Trade fair in Ljubljana (2011).

Figure 0.12: Workshop Exploring cell-material interactions, Brje pri Komnu


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LTCC Pressure sensors Functional materials Ceramic micro-reactors

Ceramic 2D & 3D structures 19


RRP1

Two- and three-dimensional ceramic structures Motivation

Hana Uršič Nemevšek 2005: Graduate in physics (University of Ljubljana, Slovenia) with a thesis: Optical holographic gratings on the base of polymers and liquid crystals 2005–2010: Employed at Jožef Stefan Institute as a young researcher 2010: Ph. D. in nanoscience and nanotechnologies (Jožef Stefan International Postgraduate School) with a thesis: Structural and electrical properties of 0.65PMN-0.35PT thick films on different substrates 2010–2011: Postdoctoral associate at Instituto de Ciencia de Materials de Madrid, Madrid, Spain 2011: Researcher at Institute Jožef Stefan, Electronic Ceramics Department and CoE NAMASTE 2012: Head of the RRP1 project at CoE NAMASTE

technology and materials are also suitable for making three-dimensional ceramic structures. Thick-film technology is used for the lateral and vertical electrical interconnections, and to realise the embedded and surface passive electronic components (resistors, thermistors, inductors, capacitors). In Figure 1.1 a photograph of LTCC-based pressure sensors is shown.

CoE NAMASTE motivates research and development synergies in the field of ceramic microsystems. Microsystems are one of the fastest-growing technologies, and most of them are made by the micro-machining of silicon. On the other hand, complex microsystems combine different materials (silicon, ceramic, metal, polymer, etc.) and technologies (semiconductor, thin and thick film, etc.). In some demanding applications thick-film technologies and ceramic materials are a very useful alternative. In comparison with silicon microsystems, the ceramic microsystems are larger, more robust and operate over a wider operatingtemperature range.

The objective of the project is to develop permanent and temporary sacrificial volume materials as well as selected functional materials, compatible with LTCC technology. At the same time, the objective is also to develop the technology for 2D and 3D LTCC microsystems and to demonstrate this new technology on devices. For this purpose the synergy of different partners during the research and development is needed. The partners are: the Electronic Ceramics Department at the Jožef Stefan Institute, the Department for Inorganic Technology and Materials at the Faculty of Chemistry and Chemical Technology, HIPOT-RR, KEKON, KEKO Equipment, and HYB. The project partners form the value chain, which includes all the activities from basic and applied research to marketing. The activities within CoE NAMASTE are limited to the demonstrator level (Figure 1.2). In the first two years of the project, the two segments of ceramic microsystems were developed. The

Ceramic 2D and 3D structures Low-temperature co-fired ceramic (LTCC) technology has been used for many years for interconnection technology in the electronics industry. Its main advantage is the compatibility with thick-film technologies. Electronic devices and systems based on a combination of these two technologies are reliable and the characteristics are stable. In comparison with other technologies, the LTCC and thick-film technologies enable the fast and easy fabrication of electronic devices and systems. Therefore, it could both reduce the cost of devices and shorten their development times. LTCC

Figure 1.1: LTCC-based pressure sensors

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Partners: Institut „Jožef Stefan“ http://www.ijs.si

Univerza v Ljubljani http://www.uni-lj.si

Hipot-RR d.o.o. http://www.hipot-rr.si

HYB d.o.o. http://www.hyb.si Figure 2.2: Innovation scenario from research to marketing activities

first segment is ceramic pressure sensors (a typical representative of micro-electro-mechanical systems), and the second segment is chemical microsystems. The developmental level of each segment is shown in Figure 1.2. Here we address preliminary and parallel projects related to 2D and 3D structures, which were supported by the Slovenian Research Agency; the Ministry of Higher Education, Science and Technology; the Ministry of Defence; the Ministry of Economic Development and Technology and the industrial partners.

development phase in several research institutions around the world. This novelty (technology and materials) is also the main topic of the research project “Two- and three-dimensional ceramic structures” within the CoE NAMASTE. The topic is, from the research point of view, explicitly multidisciplinary. Within the frame of the project, different functional and other materials, used in ceramic structures for electro-mechanical and chemical applications, are being developed, and the LTCC and thick-film technologies are being studied and applied. Part of the research group of the project “Two- and three-dimensional ceramic structures” is shown in Figure 1.3.

LTCC technology is suitable for the fabrication of ceramic microsystems, but the technology and materials for this application are in the early

Figure 1.3: Part of the research group of the project “Two- and three-dimensional ceramic structures”

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KEKO-Oprema d.o.o. http://www.keko-equipment.com

Kekon d.o.o. http://www.kekon.com


LTCC MATERIALS AND TECHNOLOGY

Motivation

Janez Holc 1976: B.Sc. in Chemistry, University of Ljubljana. 1982: M. Sc. in Chemistry, University of Ljubljana 1984: Ph.D. in Chemistry, University of Ljubljana 1970 - 1984: Employed at the Jožef Stefan Institute 1984 – 1986: Employed in Iskra Electrooptics 1986 – 2012: Employed at the Jožef Stefan Institute

Trends in the development of multifunctional microsystems are the integration of different devices such as micro-electronics, micro-mechanics, micro-fluidics, micro-optics, microacoustics, micro-thermic and micromagnetics. The example is the so-called Intelligent and Integrated Microsystem – IMS which may contains, apart from the listed functions, also sensors, actuators, communication and other electronic devices. IMS devices are nowadays mainly made of silicon. However the ceramic materials are also used. They enable the production of robust and chemical inert microsystems. Among the ceramic materials the LTCC (Low Temperature Co-fired Ceramic) material is promising material for the development of ceramic microsystems.

Present position: external collaborator

Influence of the firing conditions on the functional properties of LTCC

Most important work:

The LTCC materials are widely used for multilayer electronic packaging for modern high-speed and high-frequency electronics found in many devices for telecommunications and automotive applications. They are usually glass ceramic composite materials composed of a low-melting-point glass and ceramic filler. The relatively high amount of the glass phase enables firing of the structures at lower temperatures (around 900 °C) in comparison to classical ceramics (fired around 1300-1500 °C). Besides the reduction of the costs connected with the firing, it also enables the use of the high electrically conductive low melting point metals, such as silver and its alloys, gold and copper. The unfired LTCC material is usually in the form of ceramic tapes, where the glass and ceramics particles are embedded in the polymer material. Due to relatively easy shaping of unfired material and the easy production of multi-layered interconnected structures the LTCC was recognized as a material suitable for making three-dimensional ceramic structures, such as cantilevers, bridges, diaphragms, and buried channels and cavities, which are the building components of microsystems.

BLINC, R., CEVC, P., ZORKO, A., HOLC, J., KOSEC, M., TRONTELJ, Z., PIRNAT, J.. Electron paramagnetic resonance of magnetoelectric Pb(Fe1/2Nb1/2)O3. J. appl. phys., 2007, vol. 101, 5 pages (033901) LEVSTIK, A., BOBNAR, V., FILIPIČ, C., HOLC, J., KOSEC, M., BLINC, R., TRONTELJ, Zvonko, JAGLIČIĆ, Zvonko. Magnetoelectric relaxor. Appl. phys. lett., 2007, vol. 91, no. 1, 012905-1012905-3 MALIČ, B., JENKO, D., HOLC, J., HROVAT, M., KOSEC, M.. Synthesis of sodium potassium niobate : a diffusion couples study. J. Am. Ceram. Soc., 2008, vol. 91, no. 6, 1916-1922. MALIČ, B., BERNARD, J., HOLC, J., JENKO, D., KOSEC, M.. Alkaline-earth doping in (K, Na)NbO3 based piezoceramics. J. Eur. Ceram. Soc.. [Print ed.], 2005, vol. 25, 2707-2711.

Figure 1.4: The microstructure of DuPont 951 LTCC. The anorthite phase crystalize on the surface of the Al2O3 during the firing.

the production of microsystems, such as good workability, compatibility with commercial thick film pastes, chemical and mechanical properties of LTCC material. An important part of the successful production of the microsystems is a thorough knowledge of the microstructure and the phase composition which influence the chemical, mechanical and thermomechanical properties of the LTCC material. The microstructure of the fired sample of widely used LTCC is presented in Figure 1.4. The phase composition of commercial LTCC material (DuPont 951) as a function of firing temperature was analysed and is shown in Figure 1.5. In the temperature range between 450 and 850 °C the LTCC material is composed of lead borosilicate glass and alumina particles. The alumina particles partially dissolve during firing. Above 850 °C the anorthite phase crystalizes from the glass phase, accordingly the amount of glass phase in the LTCC decreases. The change in the phase composition affects the coefficient of thermal expansion (TCE) of the LTCC material

In the frame of the project “Two- and three-dimensional ceramic structures” several commercial LTCC materials were analysed. The study was focused on the most important properties for

Figure 1.5: The phase composition of the LTCC as a function of temperature fired in the temperature range between 600 and 1000 °C.

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processing window, which allows adjusting the firing procedure in accordance with the requirements of the integrated materials. Sacrificial and fugitive materials for the production of large and thin buried cavities In order to produce the complex threedimensional structures the use of sacrificial and fugitive material is useful. Sacrificial materials support the structures during lamination and are burned out during the firing, while the fugitive materials support the structures through the whole process. The test structures of the LTCC material were made using new carbon-based sacrificial and mineral-based fugitive materials. Reactions between the LTCC and these fugitive and sacrificial materials were analysed.

Figure 1.6: The TCE of the LTCC material vs. firing temperature.

(Figure 1.6). With increasing firing temperature the amount of anorthite in the LTCC is increasing, which results in a decrease of the TCE of the LTCC material. As the TCE of the anorthite is lower than the TCE of alumina and glass phase. The lower TCE can importantly improve the thermal shock resistance of the LTCC material, which is a desired property of material for the complex microsystems.

The cavities with a very high width-todepth ratio, i.e., 18mm/35μm, and a thin ceramic membrane on the top of the cavity were successfully prepared by using the developed sacrificial and fugitive materials (Figure 1.8). The development of such structures presents an extraordinary technological achievement, which can be used for the production of complex ceramic micro-systems.

Figure 1.7: The characteristic biaxial flexural strength of the sample fired at different temperature.

The influence of firing temperature on the characteristic flexural strength was also investigated. Lower flexural strength of LTCC at lower temperature could be correlated mainly to the porosity of the samples sintered at lower temperatures. The phase composition, mainly different ratios of the alumina and anorthite phases, had a negligible effect on the characteristic flexural strength of the LTCC material (Figure 1.7).

Figure 1.8: The microstructure of the buried cavity in the LTCC with a very high width-to-depth ratio (18 mm / 35μm) and with a thin ceramic membrane on the top (top) and a schematic crosssection of the structure (bottom).

The LTCC material properties in relation to the firing temperature show that the material has a relatively wide

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MAKAROVIČ, K., MEDEN, A., HROVAT, M., HOLC, J., BENČAN, A., DAKSKOBLER, A., KOSEC, M.. The effect of processing conditions on the properties of LTCC material. J. Am. Ceram. Soc., 95 [2], 760-767, 2012 HOLC, J., MAKAROVIČ, K., BELAVIČ, D., HROVAT, M., KOSEC, M., JORDAN, B..Postopek izdelave praznin v keramičnih večplastnih strukturah : patentna prijava P-201100202. Ljubljana: Urad RS za intelektualno lastnino, 3. jun. 2011.


FUNCTIONAL MATERIALS

Hana Uršič Nemevšek 2005: Graduate in physics (University of Ljubljana, Slovenia) with a thesis: Optical holographic gratings on the base of polymers and liquid crystals 2005–2010: Employed at Jožef Stefan Institute as a young researcher 2010: Ph. D. in nanoscience and nanotechnologies (Jožef Stefan International Postgraduate School) with a thesis: Structural and electrical properties of 0.65PMN-0.35PT thick films on different substrates 2010–2011: Postdoctoral associate at Instituto de Ciencia de Materials de Madrid, Madrid, Spain 2011: Researcher at Institute Jožef Stefan, Electronic Ceramics Department and CoE NAMASTE 2012: Head of the RRP1 project at CoE NAMASTE

Recent progress in two- and threedimensional ceramic microstructures can be considered to be the result of the growing opportunities offered for miniaturised systems by the successful implementation of functional materials and technologies. Today, the use of thick-film technology combined with other ceramic technologies and functional materials has become attractive for the production of various applications from simple functional structures, for example, bending actuators or piezoresistors, to more complex systems, such as integrated sensors, micro-fluidic systems, voltage converters, transducers, etc. Thick films processed printing technology

by

The use of the appropriate thermal treatment allows the co-firing of the functional films together with the electrical contacts and even the processing of three-dimensional selfstanding structures. In the frame of this project the processing of functional materials is studied with the aim to integrate functional thick-film layers into two- and three-dimensional ceramic microstructures. For this purpose the lead-based piezoelectric, ferroelectric and relaxor materials are prepared in the thick film and bulk ceramic forms, such as Pb(Zr,Ti)O3 (PZT), Pb(Mg0.33Nb0.66)O3 (PMN), Pb(Mg0.33Nb0.66)O3–PbTiO3 (PMN–PT), Pb(Sc0.5Nb0.5)O3 (PSN) and Pb(Sc0.5Nb0.5)O3–PbTiO3 (PSN–PT). In figure 1.10 the microstructure of PMN– PT thick film is shown.

screen

The important advantage of the conventional thick-film technology is in the successive deposition of several layers, which makes feasible thicker piezoelectric films (up to 100 m thick) and functional multilayer structures. The technology typically entails the deposition of several successive functional layers onto an electrically insulating substrate by screen-printing. Figure 1.9 shows schematically the screen-printing procedure. It is a relatively simple and convenient method for producing films with thicknesses of a few micrometres up to a few tens of micrometres.

Due to the ecologically “hazardous” materials based on lead (Pb), the research in the area of piezoelectric materials is also focused on finding and developing lead-free piezoelectric materials. Potassium sodium niobate solid solution K0.5Na0.5NbO3 (further denoted as KNN) is still considered as one of the best alternatives to the leadbased piezoelectrics. Despite the interest in the KNN system, not much has been done on the understanding of the processing of the KNN thick films and their implementation into devices. For example, implementing the KNN thick films into micro-electromechanical systems (MEMS) requires, in the first place, an extensive knowledge of the thick-film processing and also an understanding of the piezoelectric properties of the films, which are usually inferior as compared to the ceramics. Within CoE NAMASTE, in parallel ith the studies on the highly efficient Pb-based compositions, our focus is also to develop and optimize the processing conditions for the leadfree KNN thick films, towards high film density and high piezoelectric activity. We have recently improved the densification of the KNN thick films by introducing potassium sodium germanate as a liquid-phase sintering aid. As a result we obtained dense KNN thick films at 1000 °C, which is more than 100 °C lower than the typical sintering temperatures of the KNN bulk ceramics. In contrast to the KNN ceramics with typically randomly oriented grains, the KNN thick films showed preferential crystallographic orientation primarily in a non-polar

Figure 1.9: Scheme of the screen-printing procedure

Figure 1.10: Micrograph of PMN–PT thick film on alumina substrates prepared by screen-printing technique

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direction, along which, in principle, the highest piezoelectric d33 coefficient is expected. Structures processed printing technology

by

TREFAL, G., MALIČ, B., HOLC, J., URŠIČ, H., KOSEC, M.. Synthesis of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 by controlled agglomeration of precursor particles, J. Am. Ceram. Soc., vol. 95(6), pp. 1858–1865 (2012).

ink-jet

Ink-jet printing is a method for the preparation of 2D and 3D structures of functional materials, which is gaining a lot of interest recently. Its main advantages are no need for the use of templates, masks, and no need for etching, because the shape of the structures is achieved with the spatially controlled deposition of functional materials on the substrate. For preparing tick-film structures of functional materials, we have to prepare the materials in the form of a suspension. In our research we have first focused on establishing a general protocol for the preparation of costefficient and environmentally friendly aqueous suspensions containing nanoparticles of functional materials suitable for ink-jet printing. We were able to prepare aqueous suspensions of TiO2 particles, which were then used for printing (figure 1.11). First optimization of the particle size is needed to prevent nozzle clogging, next the fluid properties of suspensions, such as viscosity and surface tension have to be adjusted for the suspension to be suitable for this printing technique. We have demonstrated a general approach for the preparation of inks containing functional materials, which can be used for preparing structures of functional materials on substrates.

Figure 1.11: Ink-jet printing of TiO2 suspensions

10 mm

Figure 1.12: Test circuits for evaluations of gauge factors of thick-film resistors (black square shapes) on alumina (top) and LTCC (bottom) substrate.

the test circuits for the evaluation of gauge factors of thick film resistors are shown. Resistors were printed and fired on alumina and low temperature co-fired ceramic (LTCC) substrates. Piezoelectric bulk ceramic materials Traditionally, the piezoelectric and ferroelectric bulk ceramic materials are prepared by a solid-state synthesis method. However, due to their complex chemical composition alternative methods must be employed to prepare them in pure form and/or to enhance their functional properties. For example in the case of PMN-based materials traditional solid-state synthesis using a mixture of constituent oxides yields materials which contain in addition of perovskite also non-desired pyrochlore phases. These secondary phases deteriorate the functional properties of the material. Recently, we have developed a new method for a preparation of PMN-based materials, which in contrast to traditional solidstate synthesis yields phase-pure materials with superior properties. Our approach is based on the controlled agglomeration of reagent particles in aqueous suspensions, which enables control of the reactions in the solid state, and hence favours the pureperovskite phase formation. Materials prepared with this approach exhibit excellent properties in comparison to the materials prepared by traditional technique.

Thick-film piezoresistor materials In the frame of the project the thickfilm piezoresistor materials are also studied. Thick film resistors connected in a Wheatstone bridge configuration, printed and fired on ceramic membranes are convenient and rather low cost sensing elements for pressure or force sensors. The gauge factor is defined as the ratio of the relative change in resistance and the deformation of a resistor. The gauge factors of thick-film resistors are up to 15 or even 20 and are significantly higher than the gauge factors of sensors realised with thin metal foils. The additional advantages of thick film resistors are low temperature coefficients of resistivity of the gauge factors and a wide range of resistivites of realised components. In figure 1.12

25

KUŠČER, D., STAVBER, G., TREFALT, G., KOSEC, M.. Formulation of an aqueous titania suspension and its patterning with ink-jet printing technology, J. Am. Ceram. Soc., vol. 95(2), pp. 487–493 (2012). ROJAC, T., MALIČ, B., KOSEC, M., POŁOMSKA, M., HILCZER, B., ZUPANČIČ, B., ZALAR, B.. Mechanochemical synthesis of NaNbO3: a complementary study of reaction mechanism using Raman spectroscopy and quadrupole 23 perturbed Na nuclear magnetic resonance. Solid state ion., vol. 215, pp. 1–8, (2012).


LTCC-BASED CERAMIC PIEZORESISTIVE PRESSURE SENSORS

Motivation

Darko Belavič 1977: Graduate in electrical engineering from the University of Ljubljana, Slovenia From 1978: Employed at Iskra Uporovni elementi, Šentjernej 1980: Specialization on hybrid thickfilm technology at BTM, Gent, Belgium 1985: Iskra R&D Management School, Škofja Loka, Slovenia 1995-1997: Coordinator of mixed R&D group on hybrid thick-film technology From 1997: Employed at HIPOT-RR, Slovenia and head of the R&D Group HIPOT From 1998: Additional employed at Jožef Stefan Institute, Ljubljana, Slovenia 2004-2006: Coordinator of Slovenian partner HIPOT-HYB in the project NEWTRESI (6.FP) 2004-2007: Coordinator of Slovenian partner HIPOT-HYB in the project MINUET (6.FP) 2004-2007: Coordinator of five Slovenian partners in the project GreenRoSE (6.FP) From 2007: Head of the program KeraMEMS From 2010: Work in the RRP1 project at CoE NAMASTE Membership: MIDEM Society and Technology Centre SEMTO

application and the technology being used. A particularly important material is the material for the deformable diaphragm. This elastic diaphragm has to fulfil some basic requirements, including an elastic behaviour over a wide strain range without creep and/or hysteresis. LTCC material is fragile, but on the other hand, flexible and strong enough to fabricate (with proper design and construction) the diaphragm of pressure sensors for different pressure ranges. The typical values of Young’s modulus are about 110 GPa, flexural strength about 200 MPa, and Poisson’s ratio about 0.17. These values are depending on the microstructure and can be different in LTCC materials of various producers. Figure 1.14 shows the deflections of the diaphragms made with alumina (96% Al2O3), and LTCC materials. The deflections as a function of the distance from the diaphragm centre (r) are presented for the pressure sensors at an applied pressure of 100 kPa. The diameter of the circular edge-clamped diaphragm is 6 mm, and the thickness is 100 µm. The deflection of LTCC diaphragm is about three times bigger

Pressure sensors convert a physical quantity, i.e., pressure, into an electrical signal. In most cases the sensing elements in pressure sensors are based on the piezoresistve principle and are made by micro-machining silicon and semiconductor technology. For specific applications some other materials (ceramic, metal, polymer, etc.) and technologies (thin and thick film, etc.) are more suitable. Conventional alumina-based ceramic piezoresistive pressure sensors with a flexible diaphragm have been on the market for many years. But the fabrication of ceramic pressure sensors using thick-film and LTCC (lowtemperature cofired ceramic) materials and technology is a new challenging opportunity for the pressure-sensor market. This is mainly because the use of LTCC material and technology increases the pressure sensitivity and enables more flexibility in designing and construction. Construction sensors

of

ceramic

pressure

Typical ceramic pressure sensors are made with circular edge-clamped deformable diaphragms. The edge of the diaphragm is bonded to the hard and inflexible ring, and indirectly to the base substrate. These three elements form the cavity of the pressure sensor. The cross-section of this type of ceramic pressure sensor is D ai p h ra gm w ith ra d ui s R ( ) a n d th ci kne ss ( t) . C a v ity

German, Polish and American IMAPS chapters

Figure 1.14: The deflections of diaphragms made with LTCC and alumina materials at an applied pressure of 100 kPa.

EU programmes EURIMUS and EUROPRACTICE European Global Business Council on Electronic Components Most important publications:

LTCC s tru c tu re

as compared with the deflection of alumina diaphragm. The dependence of the geometry and the material properties of the LTCC construction on the deflection of an edge-clamped deformable diaphragm under an applied pressure is described with the equation

M e ta l tu be

Belavič D. et al. Int. J. of Appl. Ceramic Tech. 3: 442-449, 2004 Belavič D. et al. Microelectron. Reliab. 45: 1924-1929, 2005 Belavič D. et al. J. Electroceramics 19: 363-368, 2007

Figure 1.13: The cross-section of the LTCC structure of a thick-film pressure sensor (not to scale).

schematically shown in Figure 1.13.

yr  

The capsule of the thick-film pressure sensor can be made from different materials, depending on the

3P 1  2 R 2  r 2  16 E t 3

2

where the deflection y at the position r from the centre of the diaphragm is a

26


function of the applied pressure, P, the material characteristics (Young’s modulus, E, and Poisson’s ratio, ) of the diaphragm, and the dimensions (thickness, t, and radius, R) of the diaphragm (Figure 1.13). The applied pressure generates not only the deflection but also the tensile and the compressive strains in the diaphragm.

presented. LTCC pressure sensors for low pressure range The pressure sensor (Figure 1.16) was designed for the pressure range 0–10 kPa. The structure has 100-μmthick diaphragm with a diameter of 9.6 mm. The pressure sensitivity is about r140 μV/V/kPa.

The piezoresistive ceramic pressure sensor has four sensing thick-film resistors screen-printed and fired onto the deformable diaphragm. Each of these resistors acts as a strain gauge (based on the piezoresistive properties of the thick-film resistors). These four resistors are electrically connected in a Wheatstone-bridge configuration and excited with a stabilized bridge voltage (Vb). The thick-film resistors are shown in Figure 1.15.

Family of LTCC pressure sensors for different pressure ranges The family of pressure sensors was designed for different pressure ranges: 0–35 kPa, 0–100 kPa, 0–200 kPa, 0–400 kPa, and 0–700 kPa. All sensors have the diaphragm with a diameter of 6.8 mm, while the thicknesses of the diaphragm are from 100 to 400 μm. The pressure sensitivities are from 80 μV/V/kPa for the lower pressure range to 3.5 μV/V/kPa for he higher pressure range. An example of LTCC pressure sensors is shown in Figure 1.17.

E dge o f da i ph ragm

Th c i k - fm il pe i zo re s s i to rs

R

R

1

LTCC pressure sensors for high pressure range

4

1 5

V

2 ,3

V

OU T

b 4

R

1

2

3

4

2

R

3

The pressure sensor was designed for pressure range 0– 3400 kPa. The sensor has 600μm-thick diaphragms with a diameter of 5.8 mm. The pressure sensitivity of the sensors is about 1.3 mV/V/kPa. The test sample of LTCC pressure sensors for high pressure range is shown in Figure 1.18.

5

Figure 1.15: The electrical connection and location of thick-film resistors on the diaphragm of the piezoresistive ceramic pressure sensor.

Construction sensors

of

ceramic

pressure

In the past few years we developed the technology and the design method for a fabrication of LTCC based ceramic pressure sensors for different pressure ranges from relative low (0-5 kPa) to relative high (0-5 MPa) pressures. In the following sections some demonstrators of pressure sensors for different pressure areas will be

Most of the presented demonstrators of LTCC based ceramic pressure sensors are developed in the cooperation of CoE NAMASTE with the companies HIPOT-RR, HYB and IN.Medica. A part of the research and development team

Figure 1.16: LTCC ceramic piezoresistive pressure sensors designed for pressure range from 0 to 10 kPa. The structure has outside diameter of 25 mm.

SANTO-ZARNIK, M., BELAVIČ, D.. “The effect of humidity on the stability of LTCC pressure sensors”. Metrol. Syst. Pomiarowe, 2012, vol. 19, no. 1, 133140. SANTO-ZARNIK, M., BELAVIČ, D.. “An experimental and numerical study of the humidity effect on the stability of a capacitive ceramic pressure sensor”. Radioengineering, Prague, 201-206. BELAVIČ, D., HROVAT, M., SANTOZARNIK, M., HODNIK, M., MAKAROVIČ, K., SEDLAKOVA, V.. “Investigations of thick-film resistors for piezoresistive LTCC-based ceramic pressure sensor”. EDS'12, Electronic Devices and Systems IMAPS CS International Conference 2012, June 28-29, 2012, Brno, Czech Republic. Proceedings, 321-326.

Figure 1.17: LTCC ceramic pressure sensors designed for different pressure ranges (from 0-35 kPa to 0-35 kPa). The structure has dimension of 10 x 10 mm. The thickness of the structure is different for different pressure ranges..

Figure 1.18: LTCC ceramic piezoresistive pressure sensors designed for pressure range from 0 to 3.4 MPa. The structure has outside diameter of 15 mm.

Figure 1.19: Cooperation CoE NAMASTE with companies HIPOT-RR, HYB and IN.Medica.

is shown in Figure 1.19.

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CERAMIC MICRO REACTORS

Advanced ceramic micro-systems are in many cases created with multilayer ceramic modules that integrate screenprinted thick-film electronic components and sub-circuits as well as 3D buried structures, for example, cavities or channels.

1973: BSc., Faculty for chemistry and chemical technology, University of Ljubljana 1982: MSc., Faculty for chemistry and chemical technology, University of Ljubljana 1993: PhD., Faculty for chemistry and chemical technology, University of Ljubljana From 1974: Employed at the Jožef Stefan Institute, Ljubljana From 2009: Asst. Prof., Jožef Stefan International Postgraduate School Most important work: MALIČ, B., JENKO, D., HOLC, J., HROVAT, M., KOSEC, M.. Synthesis of sodium potassium niobate : a diffusion couples study. J. Am. Ceram. Soc., 2008, vol. 91, no. 6, 1916-1922. HROVAT, M., BELAVIČ, D., KITA, J., CILENŠEK, J., GOLONKA, L., DZIEDZIC, A.. Thick-film temperature sensors on alumina and LTCC substrates. J. Eur. Ceram. Soc.. , 2005, vol. 25, 3443-3450. KOSEC, M., BOBNAR, V., HROVAT, M., BERNARD, J., MALIČ, B., HOLC, J.. New lead-free relaxors based on the K0.5Na0.5NbO3-SrTiO3 solid solution. J. mater. res., 2004, vol. 19, 1849-1854.

Figure 1.21: Electromagnetic spectrum

Figure 1.22: Electromagnetic spectrum

are shown in Figs. 1.21. and 1.22, respectively. One example of the 3D reactor is the ozonator for the synthesis of ozone from the oxygen. The structure with3 dimensions of 70 x 40 x 1.4 mm contains 3 m of micro-channels. The operating voltage is 7 kV and the yield is 5 vol.% of ozone.

However, LTCC tapes contain a relatively high concentration of lowmelting-point glass, enabling the materials to sinter densely at relatively low firing temperatures. During the firing the top parts of the structures over the buried cavities tend to deform. One of the possible solutions is to use so-called sacrificial carbon-based layers within the O u te l t Fu e l 3D LTCC W a te r structures. During the lamination and PS 1 PS 3 the earlier stages of the firing they support the PS 2

Another example is the LTCC-based micro-reactor for steam reforming. That type of reactor was developed for S e rv c ie A ir

Fu e l

PS 4 2 x E vapo ra to r

M x i er

E vapo ra to r

Marko Hrovat

A chemical reactor is a typical device or system where the chemical stability, the thermal stability and the mechanical stability are important factors. Micro-reactors (the dimensions are in the millimetre and micrometre ranges) in comparison with large, conventional reactors have a much higher surface-to-volume ratio, and higher rates of reaction, mass and heat transfer. Therefore, the combination of LTCC (low-temperature co-fired ceramic) and thick-film technologies is suitable for the fabrication of ceramic chemical micro-reactors.

S econd leve lo f e lec tr ica lh ea te rs and tem p e ra tu re sen so rs

R E FO RM ER F irs t leve lo f e lec tr ica lh ea te rs and tem p e ra tu re sen so rs

C om bu s to r

Figure 1.20: Schematic presentation of the use of carbon bases sacrificial layers to form input and output openings and a buried cavity.

M x i er

Figure 1.23: A schematic architecture of the micro-reactor. On the top are the two evaporators for the methanol and the water. On the middle is the reformer with buried channels. On the bottom the combustor (heater) is located

the production of hydrogen as a fuel for low-temperature fuel cells. Water and methanol are steam reformed at elevated temperatures into hydrogenrich gases. Micro-reactors are basically composed of the evaporators for water and liquid fuel, the reformer and the combustor. This is schematically shown in Fig. 1.23. In the evaporator the water and the methanol evaporate. In

desired 3D structure and prevent deformations. Later, the sacrificial layers burn out. This is shown schematically in Fig. 1.20. Large cavities with either low heights of 100 um or large heights of 3 mm were successfully realised; first with the use of sacrificial layers and second with internal supporting pillars. Structures

28


GENORIO, B., SUBBARAMAN, R., STRMČNIK, D., TRIPKOVIC, D., STAMENKOVIC, V., MARKOVIC, N. M. Tailoring the selectivity and stability of chemically modified platinum nanocatalysts to design highly durable anodes for PEM fuel cells. Angew. Chem. (Int. ed., Print), 2011, vol. 50, no. 24, 5468-5472, MAKAROVIČ, K., HOLC, J., BELAVIČ, D., HROVAT, M., KOSEC, M.,. The method of fabrication of multilayer ceramic structures for non-contact dielectric heating of liquids, P-201200049, Urad RS za intelektualno lastnino, 03. 06. 2012

Figure 1.24: The final 3D LTCC structure of micro reactor. On the top of the picture is the back side of the structure and on the bottom is the top side with input and output connections. (dimensions 75 × 41 × 9 mm3).

the micro-channels of the reformer catalyzed reactions between the water and the methanol take place. The complete structure is shown in Fig 1.24. On the top of the picture is the back side of the structure and on the bottom is the top side with input and output connections. Elongated

rectangles located at longer sides are exhausts for the combustor leading from the combustor at the bottom through the whole structure. The crosssection of the internal structure is shown in Fig. 1.25. Burners’ cavities and exhausts are denoted.

Figure 1.25: The cross-section of the complex LTCC reactor structure. Burners’ cavities and exhausts are denoted. The internal structure with buried cavities and channels is shown..

29

KIEŁBASIŃSKI, K., JAKUBOWSKA, M., MŁOŻNIAK, A., HROVAT, M., HOLC, J., BELAVIČ, D.. Investigation on electrical and microstructural properties of Thick Film Lead-Free resistor series under various firing conditions. J. mater. sci., Mater. electron., 2010, vol. 21, no. 10, 1099-1105


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EM absorbers Magnetic fluids Varistor ceramics Gas-discharge systems

Overvoltage and EM protection

31


RRP2

Slavko Bernik 1986: B. Sc. thesis: Phase equilibria in the systems Bi2O3-RuO2-CdO, Bi2O3RuO2-Nb2O5 and RuO2-CdO- Bi2O5, Faculty of Chemistry and Chemical Technology, University of Ljubljana (FKKT UL) From 1986: Employed at Jozef Stefan Institute 1990: M. Sc. thesis: Research of high Tc superconductors in the system Y-BaCu-O, FCCT UL. 1991: State award for research of high Tc superconductors in the Y-Ba-Cu-O system. 1992: Ph. D. thesis: High Tc superconductots in the system Bi-SrCa-Cu-O, FKKT UL. 1993: Postdoctoral specialisation at National Institute of Standards and Technology, Ceramics Division, Gaithersburg, Maryland, ZDA 2010: Habilitation in materials at Jozef Stefan International Postgraduate School. From 2010: Head of the RRP2 project at CoE NAMASTE

Figure 2.1: Special ZnO-based varistors with high stability under DC field fulfill requirement for overvoltage protection of photovoltaic panels and wind turbine generators

Materials, components and technologies for the next level of overvoltage and electromagnetic protection In the framework of the Center of Excellence NAMASTE, established Slovenian researchers from the Jozef Stefan Institute, Kolektor Nanotesla Institute, Faculty of Chemistry and Chemical Engineering from the University of Maribor and the companies VARSI, Iskra ZaĹĄÄ?ite and Kolektor Magma join their knowledge, expertise and ideas for the same objectives of the project, to enhance the progress of materials, elements (components), devices and technologies for a higher level of current-voltage and electromagnetic protection.

concerned, its versatility of physical properties already enable broad range of technological application besides varistors and opens new challenges such as the possible replacement for expensive ITO (In-Sn-O) in technologies of transparent conductive films (TCF) for flat-screen displays and photovoltaic (PV) panels or as promising oxide thermoelectric material for high-temperature applications in waste heat recovery. With the extensive presence of modern information and telecommunication technologies, the amount of electromagnetic (EM) radiations with a broad range of frequencies drastically increased everywhere in our environment, especially in the last decade. To minimize the negative effects of high-frequency radiation on electronic equipment, humans and also other living creatures of this world, it is necessary to decrease the intensity of these radiations. In this, the key importance is played by the appropriate planning and installation of the effective systems for EM absorption, which reduces EM background by its absorption. Such an approach has significant advantages in comparison to the classical EM shielding, which EM radiation only backscatter into surrounding and hence only transfers the problem elsewhere. Effective EM protections are possible only with the available highperformance absorption materials. The development of proper magnetic materials for EM absorption strongly complies with another nowadays very interesting topic of magnetic fluids, which opens another array of new technologies in biomedical applications.

Our society is highly technologically oriented. At the same time as the technology in many ways strongly contributes to the quality of our lives, it also makes us very much dependent on it and consequently vulnerable. Electrical and electronic equipment and devices, information and telecommunication technologies are part of our everyday life at work and in our homes. Their undisturbed use is essential in many ways and can be ensured only with the use of highquality devices for protection against transient surges which mostly result from lightning strikes and electrostatic discharges. Without proper protection transients can harm or even destroy the equipment, which causes large material and economic damage due to loss of equipment, loss of work hours (reduced production), and disturb communications and the transfer of the data, which is essential for the everyday activities in the global world. However, of the highest importance is ensuring the safety of the people and protection of their lives, endangered by sudden burst of energy via unprotected or even improperly protected equipment while in use. ZnO-based varistors with high current voltage nonlinearity and high energy absorption capability, and combinations of ZnO-based varistors and gas discharge tubes (GDT) offer the best solutions for the construction of highly efficient surge protection devices (SPDs). When ZnO is

The objectives of the project are improved and new materials, new knowledge, new applications and new technologies that will support the development of elements and devices for the next level of overvoltage and EM protection, in accordance with the strategic plans and orientations of the industrial partners. In this general rules

32


for the protection systems are persuaded that the protection system has to protect reliably and efficiently without interfering with the device under protection, which is possible only when the protection system fully complies with the protected device. Important issues are also miniaturization and a higher level of integration of protection elements and systems with other electrical/electronic components and devices. The project is opened also toward novel applications with high potential in the future, which are not yet in the domain of the industrial partners in the project but they involve either materials or technologies familiar to them; i.e. ZnObased TCFs, ZnO-based thermoelectric materials, magnetic fluids, etc.

application between N line (L) – neutral (N)).  Combined SPDs of varistors and GDTs (higher level of surge protection, saving on raw materials and energy). R&D activities on the electromagnetic (EM) absorbing materials and EM protection involve the development of:  High-permeability soft-magnetic powders.  New generation of the advanced composite materials based on softmagnetic filler for applications in different wireless systems such as RFID and radar systems.  Absorber materials to reduce the reflection of incident microwave radiation.  Absorber materials to reduce the penetration of incident microwave radiation.  Materials for reduced electromagnetic interference between the individual elements of the electronic systems to improve their working characteristics.  Measuring systems for the characterization of magnetic materials and composites in the frequency range from 40 MHz to 10 GHz.  Method for the synthesis of superparamagnetic particles of barium hexaferrite.  Synthesis methods for the processing of various magnetic nanoparticles for biomedical applications.  Soft/hard magnetic composite materials for sensor applications.  Soft/hard magnetic composite materials for rotor applications.

The R&D topics related to ZnO ceramics, varistor ceramics and overvoltage protection devices (SPDs) involve the development of:  Low-doped ZnO based varistor ceramics (saving on raw materials, ecological benefits).  Varistors based on low-doped varistor ceramics (lower production costs, energy savings).  Varistors for dc field applications in renewable energy systems of photovoltaic panels and wind turbine generators (reliable production of “green” energy).  Polymer varistors based on composites of polymer matrix and varistor powder filler (recycling of waste varistors).  Thick film varistors and tapes for he integration of overvoltage protection into hybrid circuits (a new, highly demanding device).  Transparent conductive ZnO films for applications in flat screen displays and photovoltaic panels to replace ITO (In-Ti-O), which due to limited production of In and its high prices already endangers the rapid growth of these applications.  ZnO-based oxide thermoelectric materials, which are highly demanded in the quest for suitable n-type counterparts of high temperature thermoelectric p-n modules for waste heat recovery.  New miniaturized GDTs which are of key importance for the miniaturization of surge protection devices (SPDs) at preserved efficiency and reliability (reduced production costs, saving on energy).  Technology for preparation of selfextinguishing GDTs (new

The important aspect of the project is shairing the equipment among the partners in the project and the purchase of new equipment for the synthesis of materials, their characterization and testing, which is needed for the successful realization of the project as well as for the necessary long-term R&D activities of the partners in accordance with their strategic plans.

33

Partners: Varsi d.o.o. http://www.varsi.si/

Iskra Zaščite d.o.o. http://www.iskrazascite.si/

Kolektor Magma, d.o.o. http://www.kolektor.si

Nanotesla institut Ljubljana http://www.nanotesla.si/index.php

Institut „Jožef Stefan“ http://www.ijs.si

Univerza v Mariboru http://www.uni-mb.si

Figure 2.2: Facade putty and wall paintings to reduce the penetration of electromagnetic (EM) radiation


LOW-DOPED ZNO-BASED VARISTOR CERAMICS

Slavko Bernik 1986: B. Sc. thesis: Phase equilibria in the systems Bi2O3-RuO2-CdO, Bi2O3RuO2-Nb2O5 and RuO2-CdO- Bi2O5, Faculty of Chemistry and Chemical Technology, University of Ljubljana (FKKT UL) From 1986: Employed at Jozef Stefan Institute 1990: M. Sc. thesis: Research of high Tc superconductors in the system Y-BaCu-O, FCCT UL. 1991: Sate award for research of high Tc superconductors in the Y-Ba-Cu-O system. 1992: Ph. D. thesis: High Tc superconductots in the system Bi-SrCa-Cu-O, FKKT UL. 1993: Postdoctoral specialisation at National Institute of Standards and Technology, Ceramics Division, Gaithersburg, Maryland, ZDA 2010: Habilitation in materials at Jozef Stefan International Postgraduate School. From 2010: Head of the RRP2 project at CoE NAMASTE Most important work: PODLOGAR, M., RICHARDSON, J. J., VENGUST, D., DANEU, N., SAMARDŽIJA, Z., BERNIK, S., REČNIK, A.. Growth of transparent and conductive polycrystalline (0001)-ZnO films on glass substrates under lowtemperature hydrothermal conditions. Adv. Funct. Mater., 2012, vol. 22, no. 15, 3136-3145

The research activities are aimed at decreasing the varistor dopants added to ZnO to a minimum level that still enables the preparation of varistor ceramics with excellent current-voltage nonlinearity for a broad range of breakdown voltages. While the usual additions to ZnO of the varistor dopants, i.e., oxides of Bi, Sb, Co, Mn, Ni and Cr, are in the range from 7 to 12wt.%, our results confirmed that their amount can be reduced by as much as four times. Such varistor ceramics with a high microstructural homogeneity contain the minimum amounts of secondary phases at the grain boundaries of the ZnO and represent the closest approximation to an ideal varistor material composed only of highly conductive ZnO grains of the proper size for a given breakdown voltage, separated only by non-linear, varistor-type, grain boundaries (Fig. 2.7).

characteristics. The ideal non-linear grain boundary has a breakdown voltage of about 3.2 V. The size of the ZnO grains determines the number of grain boundaries at a given thickness of ceramics and hence its breakdown voltage. Control of the grain-growth is essential for the successful preparation of various types of varistors with suitable dimensions (thickness) for overvoltage protection at voltages ranging from a few volts up to several 100 kilovolts. Bi2O3, which contributes the liquid phase, and the spinelforming dopants, Sb2O3 in high-voltage and TiO2 in low-voltage varistor ceramics, are the main grain-growth controlling dopants. Their influence on the grain growth is, in general,

The idea of reducing the amount of varistor dopants added to ZnO seems obvious and appealing for the preparation of varistor ceramics. In reality, however, it contradicts some generally accepted understandings about varistor ceramics related to the processes of grain growth and microstructure development, which have a key influence on the breakdown voltage. Each varistor dopant has a specific role in the formation of the unique electrical characteristics of varistor ceramics, which result from the Bi2O3-induced current-voltage nonlinearity of the grain boundaries in the pre-breakdown region and the high conductivity of the ZnO grains doped with oxides of Co, Mn and Ni in the upturn region at high currents of the I-U

Figure 2.6: Exaggeratedly grown ZnO grains with IBs which form in TiO2-doped ZnO ceramics. A microstructure composed entirely of such grains is characteristic for low-voltage varistor ceramics.

BERNIK, S., BERNARD, J., DANEU, N,, REČNIK, A.. Microstructure develop. in low-antimony oxide-doped zinc oxide ceramics. J. Am. Ceram. Soc., 2007, vol. 90, no. 10, 3239-3247. BERNIK, S., DANEU, N., REČNIK, A.. Inversion boundary induced grain growth in TiO2 or Sb2O3 doped ZnObased varistor ceramics. J. Eur. Ceram. Soc.., 2004, vol. 24, 3703-3708. BERNIK, S., MAČEK, S., AI, B.. Microstructural and electrical characteristics of Y2O3-doped ZnOBi2O3-based varistor ceramics. J. Eur. Ceram. Soc.., 2001, vol. 21,1875-1878. BERNIK, S.. Synthesis and phase relations of the 110 K superconducting 2223 phase in the Bi-Pb-Sr-Ca-Cu-O system. Supercond. sci. technol., 1997, vol. 10, 671-677.

Figure 2.7: Microstructures of classical and low-doped varistor ceramics with a three times lower amount of varistor dopants added to ZnO, sintered at 1200oC for 2 hours. Both materials have a break-down voltage at 200V/mm and a coefficient of nonlinearity equal to 40. Note the difference in the amount of secondary phases at the grain boundaries of the ZnO.

34


explained by the amount of the secondary phases at the grain boundaries they form in reactions with ZnO, which also incorporate significant amounts of other varistor dopants. A higher level of doping and hence a larger amount of secondary phases mean stronger hindering of the grain growth and consequently a smaller grain size and a higher breakdown voltage for the ceramics.

infected with an IB and can grow larger before they collide with each other, which results in coarse-grained ceramics. However, at larger additions of Sb2O3 more grains are infected with the IB and can grow very little before they impinge on each other, which gives fine-grained ceramics. Based on an understanding of the actual mechanism that controls the grain growth in varistor ceramics, the group from the IJS developed varistor ceramics having only 3 to 4 wt.% of varistor dopants added to the ZnO. Within the Centre of Excellence CoE NAMASTE RRP2 varistor ceramics with a breakdown voltage below 100V/mm we successfully developed. Now, we have formulations for the processing of the low-doped varistor ceramics with an excellent I-U nonlinearity and breakdown voltages ranging from 60V/mm to 350V/mm, all with Sb2O3 as the additive for the grain-growth control (Fig. 2) and sintered at 1200°C for 2 hours. They are used within the project RRP2 for the optimisation of the varistor compositions and the development of a new generation of varistors of all types in the VARSI Company.

Both dopants, Sb2O3 and TiO2, also result in the formation of inversion boundaries (IBs) in the ZnO grains. In the case of Sb2O3 the IBs are present in each ZnO grain of the varistor ceramics, while during the addition of TiO 2 only in some, typically extremely large, grains. A solid basis for the development of low-doped varistor ceramics came with the discovery by the researchers from the Jozef Stefan Institute that IBs play a key role in grain growth and microstructure development, while the role of the spinel phase is subordinated. This changed entirely the paradigm of microstructure development in the varistor ceramics and showed that the grain growth in ZnO ceramics can be controlled by very small amounts of IBs-triggering dopant in a way to prepare either coarse- or fine-grained ceramics. Grains that are infected with an IB in the early stage of sintering preferentially grow at the expense of normal grains until they collide with each other and completely prevail in the microstructure. The number of grains infected with IBs can be controlled with low amounts of the IBs-triggering dopant. At lower additions of Sb2O3 fewer grains are

Low-doped ZnO-based varistor ceramics means savings in raw materials, a reduction of processing costs, enhancement of the varistor performance and benefits to the environment. It also gives us advantages in the development of thick-film varistors and multilayer varistors.

PODLOGAR, M., RICHARDSON, J. J., VENGUST, D., DANEU, N., SAMARDŽIJA, Z., BERNIK, S., REČNIK, A.. Growth of transparent and conductive polycrystalline (0001)-ZnO films on glass substrates under lowtemperature hydrothermal conditions. Adv. funct. mater. (Print), 2012, vol. 22, no. 15, 3136-3145. MENG, L., ZHENG, L., CHENG, L., ZHENG, Y., LI, G., BERNIK, S.. Enhancement of the electrical stability of ZnO varistors by a novel immersion process. J. Am. Ceram. Soc., 2011, vol. 94, issue 9, 2939-2945. LUKOVIĆ GOLIĆ, D., BRANKOVIĆ, G., POČUČA, M., VOJISAVLJEVIĆ, K., REČNIK, A., DANEU, N., BERNIK, S., ŠĆEPANOVIĆ, M., POLETI, D., BRANKOVIĆ, Z.. Structural characterization of self-assembled ZnO nanoparticles obtained by the sol-gel method from Zn(CH[sub]3COO)[sub]2[times]2H[sub] 2O. Nanotechnology (Bristol), 2011, vol. 22, no. 39, 395603-1-395603-10. BERNIK, S., PODLOGAR, M., DANEU, N., REČNIK, A.. A novel approach to tailoring the microstructure and electrical characteristics of ZnO-based varistor ceramics via inversionboundary (IB) induced grain growth. Zašt. mater., 2011, vol. 52, no. 2, 7379. BERNIK, S., CHENG, L., PODLOGAR, M., LI, G.. Development of ZnO-based varistor ceramics sintering at temperatures below 1000°C. V: BELAVIČ, D. (ur.), ŠORLI, I. (ur.). 48th International Conference on Microelectronics, Devices and Materials & theWorkshop on Ceramic Mycrosystems, September 19 September 21, 2012, Otočec, Slovenia. Proceedings. Ljubljana: MIDEM Society for Microelectronics, Electronic Components and Materials, 2012, 169174. BERNIK, S., NASTRAN, S., RUSTJA, S., SAMARDŽIJA, Z., TAVČAR, A., PODLOGAR, M., PIRIH, A., CERGOLJ, M.. Slip-casting of tubular ZnO-based varistor ceramics. V: ĐONLAGIĆ, Denis (ur.), ŠORLI, Iztok (ur.), ŠORLI, P. (ur.). Proceedings. Ljubljana: MIDEM Society for Microelectronics, Electronic Components and Materials, 2010, 153158.

Figure 2.8: Current-voltage characteristics (E vs. J) of the low-doped varistor ceramics with the addition of only 34 wt.% of varistor dopants to ZnO, sintered at 1200oC for 2 hours, with the microstructures of highand low-voltage varistor ceramics.

35


THERMAL CHARACTERIZATION OF VARISTORS AND THE DEVELOPMENT OF VARISTORS FOR “DC” APPLICATIONS

Thermal characterization of varistors

Andrej Pirih 1981: B. Sc. - Faculty of Electrical Engineering, University of Ljubljana = FEE UL 1981 – 1983: FEE UL – research assistant, working on fundamental research of switching capacitor-filters and switching capacitor oscillators. 1983 – 1987: Employed at SIQ Slovenian Institute of Quality and Metrology – independent researcher. 1987 – 1999: Employed at Center of Electro-Optics (now the company Fotona) – head system engineer. 1995: M. SC. - FEE UL 1999 – 2005: Employed at Iskra Zaščite d.o.o. – R&D director. From 2003: An active member of the International Electrotechnical Commission (IEC)

varistor ceramics and their sources, which enable further optimizations of the processing parameters. Such an approach also contributes strongly to a better understanding of the behaviour and the response of varistors exposed to various types of electrical transients (loads).

The properties of ZnO-based varistor ceramics depend not only on their composition, but also on their homogeneity, which is to a large extent influenced by the preparation of the starting powder mixture and the granulate, the shaping of the raw pieces by pressing and the final heat treatment. The quality of the complete processing is evaluated by laboratory tests in which the varistors are exposed to various current loads with simultaneous monitoring of their temperature over the volume by the use of a thermo-vision camera. Such tests make it possible to study the homogeneity of varistor ceramics under current loads and an analysis of the correlations between the type of varistor ceramics and the processing technology, on the one hand, and their current absorption or thermal resilience, on the other. It allows us to determine any inhomogeneities in the

Typical transient loads to which varistors, as overvoltage protection devices, are exposed, can be characterized as follows: 1. Current loads with various impulse shapes – shape 10/350 µs is considered as the most severe of all the current impulses (fig. 1); 2. AC voltage overloads 50Hz/60Hz (fig. 2); 3. DC voltage loads (fig. 3); Interactive loads of current impulses while the varistors are subjected to an AC or DC voltage.

From 2005: Employed at VARSI d.o.o. – Project & Engineering director 2010: IEC 1906 AWARD in 2010 for his outstanding professional contribution to the work of working groups WG3 and WG5 and sub-committee SC 37A 2011: SIST award in 2011 for exceptional achievements in the standardization of overvoltage protection systems and the applications of varistors. Most important work: PIRIH, A., CERGOLJ, M., BERNIK, S., SODEC, J., TAVČAR, A., HARIŠ, M. A high-current surge generator 8/20 (µs) for testing ZnO varistors and SPDs up to 100 kA; 48th International Conference MIDEM & the Workshop on Ceramic Mycrosystems, September, 2012, Otočec, Slovenia. Proc.. Ljubljana: MIDEM, 2012, 303-308.

Figure 2.12: a) Current impulse shape 10/350 µs. b) Temperature distribution in varistor stack loaded with current impulse 10/350 µs

PIRIH, A., CERGOLJ, M., BERNIK, S., RUSTJA, S., TAVČAR, A., HARIŠ, M. Test methods to determine the current rating of Iimp for class I SPD and relations with the test parameters of applied generators; Proceedings. Ljubljana: MIDEM, 2010, 89-94. SURTEES, A. J., ŠTAGOJ, A., PIRIH, A., CREVENAT. New test method to determine the short-circuit withstand rating of an SPD; 29th International conference on lightning protection (ICLP 2008), 23nd-6th June 2008, Uppsala, Sweden. [S.l.]: ICLP, 2008, 7b5-1/7b-5-12

Figure 2.13: a) AC/DC source for load tests of varistors (CoE NAMASTE). b) AC overload of varistor

36


PIRIH, A., CERGOLJ, M., BERNIK, S., SODEC, J., TAVČAR, A., HARIŠ, M.. A high-current surge generator 8/20 [mu]s for testing ZnO varistors and SPDs to 100 kA. V: BELAVIČ, Darko (ur.), ŠORLI, Iztok (ur.). 48th International Conference on Microelectronics, Devices and Materials & theWorkshop on Ceramic Mycrosystems, September 19 September 21, 2012, Otočec, Slovenia. Proceedings. Ljubljana: MIDEM Society for Microelectronics, Electronic Components and Materials, 2012, 303308. Figure 2.14: a) DC overload of varistors. b) Temperature distribution in overloaded varistor

Development of varistors for DC applications

known; therefore, such aging tests are performed only occasionally and when new materials are in use or the processing parameters were changed. In contrast, the influence of a DC voltage on varistors and the reasons for their instability are not well studied and understood. It shows as a degradation of the transition knee from the ohmic to the nonlinear regime in the I-U curve and a decrease of the non-linear coefficient, which subsequently results in an increase of the leakage current IL. At this point the varistor comes into the state of a positive feedback loop, which means that ohmic heating due to a leakage current causes an increased thermionic emission and hence a larger leakage current, and the degradation is accelerated towards the complete failure of the varistor. The research is aimed at understanding these processes and finding solutions. A typical example of such a test is shown in Fig. 2.15.

With the expansion of renewable energy sources such as photovoltaic systems (solar panels) and windturbine generators, which require the use of inverters, the need for overvoltage-protection devices operating under a DC voltage has emerged. Practical experiences already showed a serious problem of a reduced lifetime for surge-protection devices operating under a DC voltage. This presents a serious challenge to the producers of varistors, a basic component of surge-protection devices, to enhance their durability under a DC field. Hence, an important research activity in the development of varistors within the project RRP2 is focused on studies of the varistor’s behaviour under a DC voltage to understand the degradation processes, and to prevent them, for an improved performance and an extended lifetime of the varistors. Life-time test of normal DC voltage

varistors

under

The behaviour of varistors under an AC voltage is relatively well studied and V750P50/2 - life test on twin blocks T=40ºC, R.H=97%, V DC =970V, t=500h, (tim e interval Δt=30 m in) 100 90 80 70

IL [μA]

60 50 40 30 20 10 0 0

100

200 block1 block5

300

400

500

600

700

block2 block6

800

block3 block7

Figure 2.15: Life-time test of varistors under DC voltage

37

900 1000 1100 1200 1300 1400 block4 block8

No. of m eas.

PIRIH, A., CERGOLJ, M., BERNIK, S., RUSTJA, S., TAVČAR, A., HARIŠ, M.. Test methods to determine the current rating of Iimp for class I SPD and relations with the test parameters of applied generators. V: ĐONLAGIĆ, Denis (ur.), ŠORLI, Iztok (ur.), ŠORLI, Polona (ur.). Proceedings. Ljubljana: MIDEM - Society for Microelectronics, Electronic Components and Materials, 2010, 89-94.


GAS-DISCHARGE TUBES

Robert Rozman 2003: Graduate in physics (University of Ljubljana, Slovenia) with thesis Instability of wave absorption in laser processing of materials From 2003: Employed at Faculty of Mechanical Engineering, University of Ljubljana. 2008: PhD in mechanical engineering (University of Ljubljana) with thesis entitled “Model and properties of plasma plume formation in laser material processing”. From 2008: Employed at Iskra Zaščite d.o.o., Surge Voltage Protection Systems, Engineering and Cooperation, R & D - Head of Gas Discharge Tube Program. Most important work: ROZMAN, R., GRABEC, I., GOVEKAR, E.. Influence of absorption mechanisms on laser-induced plasma plume. Appl. surf. sci., 2008, Volume 254, Issue 11, Pages 3295–3305 ROZMAN, R., KMETEC, B., PODOBNIK, B., KOVAČIČ, D., GOVEKAR, E.. Optimisation of direct laser structuring of printed circuit boards. Appl. surf. Sci, 2008, Volume 254, Issue 17, 5524-5529 BIZJAK, M., BRECELJ, F., JELIĆ, N., NEMANIČ, V., PIRIH, A., PREGELJ, A., ROZMAN, R., ŠTAGOJ, A., ZAJEC, B., BIZJAK, M. (Ed.). Plinski odvodnik za zaščito pred prenapetostjo pri udarih strele. Ljubljana: Zavod Tehnološki center SEMTO, 2010. XVI, 1170-1178. (2010) 4.893.

In general, the gas-discharge tube (GDT or gas arrester) consists of two electrodes that are separated by a ceramic tube, with the interior being completely sealed and filled with an appropriate mixture of gases. In the presence of low voltages on the electrodes the GDT acts as a perfect insulator, while during the occurrence of surges the GDT begins to conduct an electrical current. Conduction starts due to an electrical breakthrough, which causes gas ionization and plasma formation. Between the electrodes the electrical arc is established, which has a very high electrical conductivity and high temperature. High electrical conductivity allows the discharge of a very high current, but high temperatures can lead to thermal damage of the GDT electrodes or sometimes even to the destruction of the GDT. A high-quality GDT must provide a stable spark-over voltage, fast extinguishing of the arc current after the current surge, high insulation resistance and a fast response time to establish the arc. These characteristics must be maintained even after high current surges. To achieve repeatability of the above parameters it is very important to understand the gas and plasma physics, the physics of materials and a variety of vacuum techniques. In addition, high-tech equipment is very important for the development and manufacture of GDTs. The most important equipment for GDT production is a high-vacuum furnace, which allows different heat treatments of the materials in a vacuum and an inert atmosphere. In the vacuum furnace the brazing and filling of the GDT with the appropriate mixture of pure gases takes place.

our laboratories with the construction of a new clean room and a new modern vacuum furnace (Figure below). The clean room enables the

Figure 2.8: Clean room with high-vacuum furnace

repeatable assembly of GDTs without the risk of impurities that can get inside the GDT. The most important acquisition is the new high-vacuum furnace. With full automation of the process we will achieve the rapid development and reproducible production of GDTs. At the beginning of our laboratory for GDTs in 2002 we started with the production of GDTs with a metal body. These are the GDTs where the metal body performs the function of the electrode (Figure below, 2.9a). As an insulator, we used glass where the second electrode is inserted through the glass. Such a GDT is essentially different from the usual GDT with a ceramic body (Figure below, 2.9b), which globally accounts for more than a 99% share. The advantage of the GDT with a metal body in comparison to the usual configuration, where the body is ceramic, is mainly in the larger areas of the electrode with the same external dimensions. Larger areas of electrodes bring higher current capabilities. The disadvantage of a GDT with a metal body and glass insulator is in the worse mechanical and thermal stability in comparison to the construction with a ceramic body. This deficiency led us to

For the purpose of the development and production of GDTs we updated

Figure 2.9: GDT with metal body and glas insulator (a), GDT with ceramic body (b) and GDT with metal body and ceramic insulator (c).

38


develop a new design of GDT with a metal body and a ceramic insulator (Figure above, 2.9c). This design (Figure below, 2.10a) allows easy installation, good insulation resistance, as well as high mechanical and thermal stability.

The above-described energetic GDTs are the core of our production. In addition, we employ a number of new implementations. Foremost, these are the upgrading of existing GDTs with new demands for different spark-over voltages and new dimensions. We are also dealing with the development of specific GDTs serving a specific purpose according to the desires of the market.

Within the CoE NAMASTE the main task was to minimize the size of this new design of GDT with a metal body. For this reason we conduct many different experimental tests. First we try to define the geometry of the electrodes and the ceramic insulator. After this we tested many different gas compositions and pressures and in the end we try to employ different materials for the electrodes. The quality of the samples was tested on a high-current surge generator where we simulate the real conditioning at high current overvoltages. With these improvements we achieve a very small size of the GDT for high-current surges. A dimensional comparison of our GDT with the usual GDT shows the great advantage of our design over an ordinary ceramic body (Fig. 3b). The smaller diameter of the GDT with a metal body and a high current capacity allows significant savings in terms of installation space compared to an ordinary GDT.

In general, the main disadvantage of a GDT is its ability to extinguish the arc current in the presence of follow currents. Typical performance allows us to extinguish the arc at follow currents up to 100 A. In the case of larger follow currents, there is a high probability that the GDT will not be able to extinguish the arc current. Such a case normally results in the destruction of the GDT. Therefore, in the CoE NAMASTE we have started to develop a special design of GDT, which will be able to extinguish follow currents of up to 25,000 A. The idea is to build a multicell GDT, which is a serial connection of GDTs in one closed cell. With this system we will offer a completely new product for surge-protective devices where now we can find varistors and air spark gaps. The advantages of such a GDT over existing elements-based varistor technology are a low residual voltage, galvanic separation between the electrodes and fire safety. The main advantage in comparison to the air spark gap is no exhaust in the case of the GDT. Due to these advantages of multi-cell GDT the future work in the CoE NAMASTE is well defined. Based on our experience in developing ordinary GDTs we will work on multi-cell GDTs which will open up a new field of surgeprotective devices and new opportunities for the future.

GDTs are tested according to the IEC 61643-1 standard for Class I and Class II. GDTs are suitable for use as the binding of N-PE, where the follow currents do not exceed 100 A (maximum voltage 255 V) in grounding and telecommunication lines as well as for potential equalization. The technology in our laboratory allows the manufacture of GDTs with different spark-over voltages and other requirements that come from the market.

Figure 2.10: GDT with metal body and glas insulator (a), GDT with ceramic body (b) and GDT with metal body and ceramic insulator (c).

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ROZMAN, R., Ĺ TAGOJ, A.. Operation of GDT with metal body desigend for high current surges. V: 30th International Conference on Lightning Protection, September 13-17, 2010, Cagliari, Italy. ICLP 2010. [S. l.]: IEEE Advancing Technology for Humanity, 2010, 5 pages.


ELECTROMAGNETIC WAVE ABSORPTION OF POLYMER NANOCOMPOSITES BASED ON FERRITE

Branka Mušič 2001: Graduate in chemistry (University of Ljubljana, Slovenia) with thesis: Copper(II) complexes with lignin model compound vanillin. From 2002: Employed in coating industry Helios in research and development department 2007: MSc in chemistry (University of Ljubljana, Slovenia) with thesis: Photocatalytic activity of TiO2 in facades paint . 2012: PhD in chemistry (University of Maribor, Slovenia) with thesis: Incorporation of magnetic materials in coating system 2012: Employed at Nanotesla Institute Ljubljana Most important work: Slovenian patent: Synthesis of coating composite absorber of electromagnetic radiation on the basis of ceramic ferrite materials - ŽNIDARŠIČ, Andrej, RAJNAR, Nevenka, MUŠIČ, Branka. Synthesis of composite coating absorber of electromagnetic radiation on the basis of ceramic ferrite materials: patent application : P-201100185, 2011-05-26. Ljubljana: Urad RS za intelektualno lastnino, 2011. 11 str. MUŠIČ, Branka, DROFENIK, Mihael, VENTURINI, Peter, ŽNIDARŠIČ, Andrej. Electromagnetic wave absorption by an organic resin solution based on ferrite particles with a spinel crystal structure. Ceram. int.. 2012, vol. 34, issue 4, str. 2693-2699.

Figure 2.3: Electromagnetic spectrum

The increasing exploitation of microwave (MW) frequencies has increased the amounts of electromagnetic (EM) interference and electromagnetic pollution and stimulated the development of MW absorbers. The absorption of EM waves occurs in magnetic materials due to their magnetic losses. Ferrites exhibit substantial magnetic losses in the vicinity of their natural resonance (FMR). Because of this they are one of the best materials for MW absorbers. Compared to the ferrites with a spinel structure, the hexagonal ferrites exhibit a larger intrinsic magnetocrystalline

Figure 2.4: TEM image of SrFe12O19 particles.

anisotropy field and so can be applied at higher frequencies By varying the chemical compositions it

VENTURINI, Peter, ZNOJ, Bogdan, STEINBÜCHER, Miha, MUŠIČ, Branka, ŠEGEDIN, Urban, GODNJAVEC, Jerneja, BURJA, Klemen. Environmentally friendly paints with special functional properties. V: VALANT, Matjaž (ur.), GARDONIO, Sandra (ur.), FABBRETTI, Elsa (ur.), PIRNAT, Urša (ur.). SlovenianItalian Conference on Materials and Technologies for Sustainable Growth, Ajdovščina, 4-6 May 2011. Book of abstracts. Proceedings book. Nova Gorica: University, 2011.

Figure 2.5: The reflection loss versus the frequency. Here, the bandwidth is defined as the frequency width in which the reflection loss is less than – 10 dB which indicates that 90% of the EM waves are absorbed.

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Table 2.1:

Magnetic assessment of the investigated products

Sample code

Phase

Crystal structure

Ms 2 (Am /kg)

Mr 2 (Am /kg)

Hc (kA/m)

S1

α-Fe2O3

Cubic

6

/

/

S2

α-Fe2O3, SrFe12O19

Cubic, Hexagonal

38

25

399.4

S3

SrFe12O19

Hexagonal

60

36

464.2

S4

Fe3O4, SrFe12O19

Cubic, Hexagonal

63

7

15.4

is possible to control the electromagnetic properties such as the saturation magnetization, magnetocrystalline anisotropy, permeability and the permittivity of a ferrite composite. In general, MW absorbers can be prepared in the form of ceramics or as composites where the ceramic phases are embedded in a polymeric matrix. Here, the EM properties of the composites can be very effectively tuned, simply by varying the volume fractions of the filler constituent phases. When we include magnetically different phases in the filler, one absorbing at a lower frequency and the other at a higher frequency, then it is possible to widen the absorption frequency range within one composite material.

formation of nanosized particles of SrFe12O19 with a high saturation 2 magnetization Ms = 60 Am /kg, remanent magnetization of Mr = 36 2 Am /kg and a coercivity of Hc = 464.2 kA/m was achieved after a calcination at 900 °C. With a 3+manipulation of the molar ratio 2+ Sr /Fe in the system FeO–SrO and a calcination of the co-precipitated precursor at an elevated temperature it was possible to realize filler within the composite with multipart crystal structures and multifarious magnetic properties (shown in the Table). For this reason it is possible to prepare materials with a natural resonance in different frequency ranges. The ferrites with a spinel structure are useful as absorber materials in the lower GHz range, while the hexagonal ferrites are a special kind of absorbing material in the range above 32 GHz due to their magnetic anisotropy.

The precursors of the nanocrystalline powders with single and mixed phases with the spinel and/or hexagonal structure were successfully synthesized using the co-precipitation method. The

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MUŠIČ, B., DROFENIK, M., VENTURINI, P., ŽNIDARŠIČ, A. Electromagnetic wave absorption by an organic resin solution based on ferrite particles with a spinel crystal structure. Ceram. int.. ,2012, vol. 34, issue 4, 2693-2699. DRMOTA, A., DROFENIK, M., ŽNIDARŠIČ, A.. Synthesis and characterization of nano-crystalline strontium hexaferrite using the coprecipitation and microemulsion methods with nitrate precursors. Ceram. int.., 2012, vol. 38, issue 2, 973979. DRMOTA,A., KOSELJ, J., DROFENIK, M., ŽNIDARŠIČ, A.. Electromagnetic wave absorption of polymeric nanocomposites based on ferrite with a spinel and hexagonal crystal structure. J. Magn. Magn. Mater.., 2012, vol. 324, issue 6, 1225-1229. MUŠIČ, B., ŽNIDARŠIČ, A., VENTURINI, P.. Electromagnetic absorbing materials = Absorberji elektromagnetnega valovanja. Inf. MIDEM, jun. 2011,vol. 41, št. 2, 92-96.


NANOFLUIDS FOR APPLICATIONS IN MAGNETIC HYPERTHERMIA

Magnetic fluids play an important role in biomedical applications such as magnetic resonance imaging, magnetic targeted drug delivery and magnetic fluids intracellular hyperthermia.

Irena Ban 1987: B. Sc. in inorganic chemistry (University of Maribor, Slovenia) with thesis: Procedures for obtaining pure silicon and purity comparison of the metallurgical and polycrystalline silicon with polarization curves. From 1987: Employed at the University of Maribor, Faculty of Chemistry and Chemical Engineering. 1991: M.Sc. in Chemistry (University of Ljubljana) with thesis: Synthesis and characterisation of hydroxylammonium fluorotitanates. 1999: Ph.D. in Chemistry (University of Maribor) with thesis: Synthesis and characterisation of hydroxylammonium fluorometalates of titanium, zirconium and hafnium. 2001: Habilitation in General and Inorganic chemistry. From 2011: Employed at UM (100%) and CoE NAMASTE (20%). Most important work: BAN, I., DROFENIK, M., MAKOVEC, D.. The synthesis of iron-nickel alloy nanoparticles using a reverse micelle technique. J. magn. magn. mater., Dec. 2006, vol. 307, iss. 2, 250-256.

surrounding tissue irrelevant for the magnetic energy input during the therapy. The main object of the research activity “Nanofluids for applications in magnetic hyperthermia” within the project RRP2 is to prepare and optimize magnetic fluids based on magnetic particles. An important step in these investigations is focused on the surface engineering of the nanoparticles. Several techniques are used for the preparation of magnetic nanoparticles with different TCs:

Several techniques are used for the preparation of magnetic nanoparticles. Investigations in the field of magnetic nanoparticles have increased in the last decade due to their use in biomedicine, particularly in the field of magnetic hyperthermia. This method exhibits a potential to be an alternative method in comparison to the methods used today for the curing of cancer. Here, the magnetic nanoparticles implanted in the malignant tissue which are exposed to an AC-magnetic field serve as generators of heat since they can transform the magnetic energy into the thermal energy which heats the cancer tissue to about 42 °C. This temperature representing a critical temperature might destroy the cancer cells, however, is too low to damage the surrounding healthy tissue cells which would survive. To maintain such a temperature magnetic nanoparticles with a Curie temperature equal to the therapeutic one, 42 °C, is demanded where the magnetic materials lose their ferromagnetic properties. The application of such a magnetic particles represents an auto-regulating system, which presents the overheating of the

 Microemulsions:The microemulsion method was used to synthesize the magnetic nanoparticles based on the alloy CuNi with a therapeutic Curie temperature of 43°C with the possibility to apply them for “in vivo” applications in magnetic hyperthermia. The synthesis of the particles was carried out in reverse micelles with the reduction of a mixture (Cu2+ or and Ni2+)(aq) ions in the alkaline medium with hydrazine or NaBH4. Due to the different standard potentials of copper and nickel, an inhomogeneous precipitation of both atoms during the reduction occurs, where the first is deposited copper and in the extreme case a core-shell structure takes place. The

BAN, I., DROFENIK, M., SUVOROV, D., MAKOVEC, D.. Subsolidus phase equilibria and the Li5Nd4FeO10 phase in the Li2O-Nd2O3-Fe2O3 system. Mater. res. bull.., 2005, vol. 40, iss. 10, 18561863. BAN, I., KRISTL, M., DROFENIK, M., POPOVIĆ, A.. Hydroxylammonium fluorogermanates. Thermochim. acta., 2004, vol. 419, iss. 1/2, 253-257. BAN, I., VOLAVŠEK, B., GOLIČ, L.. Synthese und Untersuchungen von Hydroxylammoniumfluorohaftanaten(IV). Z. anorg. allg. Chem. (1950), 2002, 628, 695-698. BAN, I., KRISTL, M., VOLAVŠEK, B., GOLIČ, L.. Kristallstruktur und thermische Analyse von Hydroxylammoniumhexafluorotitanat(IV)-dihydrat und Hydroxylammoniumhexafluoroindat(III). Monatsh. Chem., 1999, vol.130, 401-408.

Figure 2.11: Magnetic fluid.

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ROFENIK, M., BAN, I., MAKOVEC, D., ŽNIDARŠIČ, A., JAGLIČIĆ, Z., HANŽEL, D., LISJAK, D.. The hydrothermal synthesis of super-paramagnetic barium hexaferrite particles : review. Mater. chem. phys.., 2011, vol. 127, iss. 3, 415419 BAN, I., KRISTL, M., DANČ, V., DANČ, A., DROFENIK, M.. Preparation of cadmium telluride nanoparticles from aqueous solutions by sonochemical method. Mater. lett.., 15. Jan. 2012, vol. 67, iss. 1, 56-59

Figure 2.12: Measurement system for determination of the Heating Effect of Magnetic Fluid in Alternating Magnetic Field.

final Curie temperature was achieved using thermally activated homogenization in a NaCl salt matrix which prevents the sintering of particles.

temperature is determined by the use of a modified TGA-SDTA apparatus. DLS measurements are used for a determination of the particle size distribution. The magnetic heating effects of the solid powdered and homogenized samples of CuNi are measured with a conventionally built measuring system for generating an alternating magnetic field, equipped with a calorimeter.

 Sol-gel method: Magnetic nanoparticles of copper-nickel Cu1-xNix alloys with different stoichiometry were prepared in a process which involves four steps: preparation of starting precursor in SiO2 matrix by sol-gel method and subsequent decomposition, annealing and reduction. The reduction step has two purposes: first is the reduction of the CuNi mixed oxides to a Cu1alloy and the second is xNix homogenization of Cu1-xNix alloy nanoparticles in a reductive atmosphere

The main object of the project is to prepare and optimize the magnetic fluids based on magnetic particles and the important step of the investigation proposed in this programme is focused on the surface engineering of magnetic nanoparticles with biocompatible coatings.

 Mechanical alloying: The Cu1-xNix and Cr1-xNix nanoparticles were also synthesized with the assistance of the mechanical alloying of nickel and chromium or copper powders using a high energy ball mill Spex 8000M in nitrogen. The measured Curie point of the powders was appropriate for magnetic hyperthermia applications. The composition and magnetic properties of the particles are determined with XRD analyses and magnetic measurement using a VSM. The morphology of the synthesized particles is determined with electron microscopy (TEM) while Curie

Figure 2.13: TEM image of magnetic nanoparticles of CuNi in silica matrix; (sol-gel method)

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BAN, I., STERGAR, J., DROFENIK, M., FERK, G., MAKOVEC, D.. Synthesis of copper-nickel nanoparticles prepared by mechanical milling for use in magnetic hyperthermia. J. magn. magn. Mater., Sep. 2011, vol. 323, iss. 17, 2254-2258, FERK, G., BAN, I., STERGAR, J., MAKOVEC, D., HAMLER, A., JAGLIČIĆ, Z., DROFENIK, M.. A facile route to the synthesis of coated maghemite nanocomposites for hyperthermia applications. Acta chim. slov.. [Tiskana izd.], 2012, vol. 59, no. 2, 366-374. STERGAR, J., BAN, I., DROFENIK, M., FERK, G., MAKOVEC, D.. Synthesis and characterization of silica-coated Cu1-x Nix nanoparticles. IEEE trans. magn., Apr. 2012, vol. 48, no. 4, 4 BAN, I., KRISTL, M., DANČ, V., DANČ, A., DROFENIK, M.. Preparation of cadmium telluride nanoparticles from aqueous solutions by sonochemical method. Mater. lett.. [Print ed.], 15. Jan. 2012, vol. 67, iss. 1, 56-59


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RRP3

New materials and technologies for advanced sensor systems Motivation

Janez Trontelj 1965: E.E. degree from the Faculty of Electrical Engineering, University of Ljubljana, Slovenia 1965: Employed at University of Ljubljana 1970: M.E. degree from the Faculty of Electrical Engineering, University of Ljubljana, Slovenia 1971: Ph.D. degree from the Faculty of Electrical Engineering, University of Ljubljana, Slovenia Current position: Head of the Laboratory for microelectronics; full Professor teaching Measurements in electronics, Measurements in telecommunications and Microelectronic technologies From 2010: head of the RRP3 project at CO NAMASTE

Figure 3.1: Clinical infections and need for hand disinfection

Figure 3.2: Result of DRIE process

products and technologies which enhance the competiveness of participating members - especially with new products or more detailed procedures (e.g., usage of an optical position encoder).

The goal of this project is to develop or to employ micro and nano technologies for: - the development and characterization of new materials suitable for MEMS and NEMS products and - the development of new micro/nano structures on the integrated-microsystems level and make them suitable for mass application, for personal health monitoring, for environment monitoring and protection, etc.

Hospital infection It has been well known for a long time that hand hygiene prevents crossinfection in hospitals. Hand disinfection is therefore mandatory for medical staff in hospitals and clinics, especially when entering certain areas where all external pathogens need to be eliminated. It was found that fever and cough symptoms are significantly reduced when alcohol-based hand disinfectants are used by the employees. In Europe, ethanol is a common active agent in hand-rub formulations and is, nowadays, also recommended in guidelines for hand hygiene published by Centers for Disease Control and Prevention and by the World Health Organization. Although, at the same concentration, ethanol is less efficacious than isopropanol, which, in turn, is less efficacious than n-propanol, it is the preferred alcohol for hand antisepsis in many countries. Within CoE NAMASTE we partly developed a system which detects the concentration of ethanol with a sensor mounted in the personal badge. The badge afterwards sends information to door control to prevent or allow access if hands were disinfected.

To achieve the above goals a strong synergy between researchers of modern electronic materials, the designers of new technologies for micro-processing and micromachining and the experts understanding micromechanics, chemistry, quantum physics and electronics. Sensor systems are becoming a key developing direction as they influence practically all human activity. Therefore, they are included in all major development strategies of Slovenia including industry, environment protection, health, etc. This is the reason of the largest growth of this field in the developed world. Slovenia has already a visible role in a number of highquality achievements and is in some cases even at the leading edge as shown in the various tables in this project. Detection of various hazardous or dangerous substances becomes more and more important in all areas of everyday life. Special focus are public areas - where a mass of people is present all the time and separate detection is difficult, security points where access or detection of substances would present life hazard and medical rooms where contamination with bacteria or other life-threatening infections must be eliminated. Therefore, the group started the development of new sensors with special emphasis on improvements of materials and technology for advanced sensor systems. The discoveries of the group from the field of microelectronics and microsensor structures, integrated circuits and other areas are introduced to

DRIE fabrication process In the fabrication of advanced silicon microstructures such as microelectromechanical (MEMS) and micro-optoelecromechanical (MOEMS) systems, exact etching profile control and compatibility of etching process with semiconductor microtechnology is mandatory. Dry etching processes such as reactive ion etching (RIE) and more advanced deep reactive ion etching (DRIE) compared to wet chemical etching offer much more freedom in the etching of various profiles and etched surface quality control, independent of crystal orientation. Therefore, DRIE is becoming a basic standard tool for silicon micromachining. As a part of CoE NAMASTE special optimization of DRIE

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process was done in LMSE. The results of fabricated microstructures are much better than in standard procedures as in LMSE DRIE process is no mask undercut and no bowing effect. This optimization brings higher precision and exact matching of designed and fabricated structures.

information loss and easy control and data process. The production of a Smart Sensor has already started. THz vision Detection of hidden objects, for the purpose of providing security in case of massive surveillance of public transport has great importance today. The time of the discovery of an explosive agent in the passenger or luggage can prevent or mitigate the consequences. It can also be the discovery of weapons or dangerous objects to prevent the attacks on people (vehicles, buildings, airplanes, military facilities, etc.). For the detection of various objects in the luggage X-rays have been used, which cannot be used to illuminate the living beings, since the higher level of intensity of irradiation causes changes

Piezoelectric micropumps Piezoelectric pumps are applicable whenever a small amount of liquid or gas must be transferred. As piezoelectric pumps are small and silent, they are especially suitable for drug dosing. The main advantage is they can be positioned very near to the point of interest or diseased tissue and therefore the precise control of the drug dosage place and quantity can be obtained. As a part of CoE NAMASTE, several types of micropumps were designed and fabricated by LMSE. Vapor Trace Detection

Partners Univerza v Ljubljani http://www.uni-lj.si

Iskra Avtoelektrika d.d. http://www.iskra-ae.com

TELA merilni sistemi d.o.o. http://tela-ms.si

Iskraemeco d.o.o. http://www.iskraemeco.si

In industry many processes includes dangerous and health-hazardous gases, which should be detected if a malfunction of the process happens. Also in food industry many products can be exposed to irregular environment. Such a product can be health hazardous, but hardly detectable. With special chemical sensors, traces in the air can be detected. A sspecial point of interest was found in military section, where explosives or other chemical substances can be traced to prevent destruction or contamination. As part of RRP3 task under CoE NAMASTE sensor system for vapor trace detection of explosives +12 was made. Three TNT molecules in 10 molecules of N2 can be detected.

Figure 3.3: LMSE fabricated micropumps

in the cells (cancer). It is very important when choosing the type of lighting (frequency / wavelength) is its ability to penetrate into the material and the potential disruptions that could stop or weakened such waves. A new field is being opened that has so far been less studied because of the immaturity of the technology, this is an area of 0.1 THz to 10 THz and is called the terahertz (THz) region. In LMFE as a part of CoE NAMASTE, a new THz sensor was developed which can detect THz waves at about 300 GHz frequencies and can be used in anarray for subject or object scanning. The sensor is micro-bolometer operating at room temperatures and it is extremely sensitive as his NEP can be up to 5pW/√Hz.

Measurement of energy consumption Precise measurement of energy consumption is nowadays important for consumer and provider. Old measurement systems needed an operator that checked the state of meter mounted on the client location, but systems used recently already transmit state and also some basic information of period etc. The problems arise when the counter does not work in agreed measurement margins or there is a defect somewhere in the communication loop. Therefore, a smart system was developed under CoE NAMASTE and with cooperation between IskraEmeco and LMFE, which provide selfcalibration, communication with base in several data networks to prevent

Figure 3.5: Energy-consumption meter

Figure 3.4: Sensor system for vapor trace detection of explosives

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Figure 3.6: THz senzor


INTEGRATED POLYMER-BASED CAPACITIVE AND LOW-POWER GAS SENSOR FOR REMOTE SENSING OF CHEMICAL AGENTS

Hand disinfection

Anton Pleteršek 1976: B.D. University of Ljubljana, FE, Slovenia 1987: Ph.D. University of Ljubljana, FE, Slovenia Co-founder of the IDS-microchip hitech company where he is managing the designs of ASSPs.

The active substance in most hand disinfectants is mainly ethanol (ethyl alcohol), CH3CH2OH, so our application focuses on detecting ethanol vapors in the air. A typical use of hand disinfectant is a dose of 3.4 ml of fluid from the original dispenser, followed by 30 seconds of hand scrubbing (surgical 1.5 minutes), until the user’s hands are completely dry. In this process, all of the disinfectant evaporates, and the resulting gas can be detected by chemical sensors. The preferable choices for low power applications – like wireless sensing – are capacitive sensors.

Alcohol Sensors

2010: National Award for the best innovations for the year 2010 (CCIS`s Award for best Innovation) granted by Chamber of Commerce and Industry of Slovenia Current positions: University of Ljubljana, FE, Department of microelectronics LMFE; Associate Professor for the Microelectronics System Integration at the FE, Ljubljana and for Integrated Circuits in FERI Maribor Most important work: US000007282901B2 Temperature independent low reference voltage source , US patent US000007777661B2 Interpolation method and a circuit for carrying out said method used in a high-resolution encoder, US patent

Figure 3.7: Fabricated LMFE capacitive based chemical sensor.

US020110241842A1 Method for a battery and passive power supply to an RFID tag and a switching circuit for carrying out said method , US patent SI000000023192A Procedure for the acquisition and shaping of external sensors by using RFID smart labels and circuit for performing this procedure, SI patent

Figure 3.8: Metal-oxide SnO2 sensor fabricated in LMFE. Heater and ethanol-sensing plate is shown.

Materials for sensors Successful realization and fabrication of micro-machined capacitive sensors implemented by two types of polymer films SU8 and PEUT have been done by the LMFE research group. The change in capacitance with absorption of the analyte is related to three different processes: adsorption on the polymer surface (the given rise of a new thin layer on the top of the polymer), adsorption into the polymer phase (changing the dielectric constant of the polymer), and swelling of the

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Figure 3.9: Fabricated SnO2 based detector on silicon membrane. Back-etched silicon under the heater area is shown plate is shown.

polymer. These three steps define the relation between the sensor’s response, its reversibility, and its geometrical parameters. Polymer-based sensors are promising due to reduced power consumption, and have therefore been the focus of much attention. Challenges in their design and fabrication relate to their higher sensitivity to ambient humidity, selecting the most suitable polymers, and the need for additional micromachining steps in their fabrication. Next, investigation on MOSs based on tin dioxide (SnO 2) films has been done by the LMFE staff in CoE NAMASTE (Figs. 3.8, 3.9). Metal oxide semiconductor chemical sensors are in their essence resistive sensors. At high temperatures, oxygen is adsorbed onto the SnO2 crystal surface, which creates a potential barrier, thus impeding the electron flow in the sensor. In the presence of reducing gases, i.e. the target gases of the sensor, oxygen surface density decreases, thus lowering the potential barrier. This effect reduces the sensors’ resistance. MOS sensors respond to a number of different gases but their response can be tailored by using different doping agents or different concentrations of dopants in the sensing film or by using different working temperatures. We are working with platinum, polysilicon or platinum based heater and back-etched wafer in place of the heater to minimize heat dissipation. The current evaluations, done by A. Pleteršek, K. Polh in M. Macek show that heating current of 1mA will be sufficient to achieve 400°C in the place of the detector.

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FABRICATION OF SILICON MICROSTRUCTURES BY DRIE

LMSE process optimization

Danilo Vrtačnik 1981: B.Sc. from Faculty of Electrical Engineering, University of Ljubljana, Slovenia 1994: M.Sc. from Faculty of Electrical Engineering, University of Ljubljana, Slovenia 2000: Ph.D. from Faculty of Electrical Engineering, University of Ljubljana, Slovenia 1991: Employed / research at Laboratory of Microsensor Structures and, Faculty of Electrical Engineering, University of Ljubljana 2007: Senior Researching Associate at the University of Ljubljana, Faculty of Electrical Engineering, Slovenia

power of deposition and/or etch step should be appropriately corrected, i.e. by decreasing ICP power and/or by increasing CCP power. The pressure in general should be low in order to prevent off-axis ions from bombarding the trench sidewalls, but should be still high enough to supply sufficiently high density of etching species.

There are general rules how to optimize the Bosch silicon etch process. However, we have to be aware that each mask pattern design requires individual optimization. In general, high etch rate of silicon etching results in higher sidewall roughness (increased rippling) and lower profile uniformity. The coarse adjustment of the process was achieved by appropriate adjustment of source ICP and bias (CCP) RF power, while more precise adjustment was attained by proper setting the ratio between duration of etch and deposition step time and the finest adjustment by gas flow rates. When etch profile is negative tapered it is necessary to decrease the etching time or increase the deposition time. If this is not enough, then ICP and CCP

A serious problem of silicon etching (exothermic process) is the rise of the substrate temperature which affects the etching profile and selectivity when it approaches the transition glass (TG) temperature of the passivation and/or mask film. This occurs at higher etch rates and longer etch times. For comparison, results of etching micropillar arrays obtained by our conventional RIE system and the new a)

Most important work: VRTAČNIK, D., RESNIK, D., MOŽEK, M., PEČAR, B., AMON, S. Investigation of cutting edge in edge-on silicon microstrip detector. Nucl. instrum, methods phys res., Sect. A, Accel.. [Print ed.], Aug. 2010, vol. 620, no. 2/3, 557-562 ILIESCU, C., VRTAČNIK, D., AMON, S. Residual stress in thin films PECVD depositions : a review. J. Optoelectron. Adv. Mater., Apr. 2011, vol. 13, no. 4, 387-394. RESNIK, D., HOČEVAR, S., BATISTA, J., VRTAČNIK, D., MOŽEK, M., AMON, S.. Si based methanol catalytic micro combustor for integrated steam reformer applications. Sens. actuators, A, Phys.. , 2012, vol. 180, no.1 , 1-10.

b)

Figure 3.10: SEM photomicrograph of silicon pillar arrays obtained in LMSE by: a) conventional RIE system and b) DRIE system.

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VRTAČNIK, D., RESNIK, D., MOŽEK, M., PEČAR, Borut, AMON, S.. Investigation of cutting edge in edge-on silicon microstrip detector. Nucl. instrum, methods phys res., Sect. A, Accel.., Aug. 2010, vol. 620, no. 2/3, 557-562

a)

b)

Figure 5.11: a) SEM image of silicon test microstructures and b) cross-section of 4 µm wide silicon holes (inset shows the rippling effect).

DRIE Plasmalab 100-ICP 180 system is shown in Fig.3.10a and Fig. 3.10b, respectively. Optimized RIE (SF6/O2 chemistry) process results in silicon etching rate of 1.8 m/min, selectivity of 75, mask undercut of 1.5m (pillars with height 33m and width 3.5m, i.e. AR=9), while the optimized DRIE process (etching rate of 2.5 m/min, selectivity of 120, AR=12) shows no mask undercut and no bowing effect for the same depth of micropillars.

USA and applying standard photolithography. Microstructures consisted of pillar, hole and trench arrays with dimensions ranging from few micrometers to few hundred micrometers representing in total silicon load pattern around 50%. Fig.3.11a shows SEM image of arrays of pillars and holes 5, 8 and 10 µm wide and 30 µm high and deep, respectively. Detail of 5 µm holes (actual dimension is 4 µm) in cross-sections is shown in Fig.3.11b. Inherent property of Bosch etching process is the rippling (scalloping) effect, where typical holes sidewall roughness of 150 nm was measured.

Fabricated test microstructures Starting material was single side polished 100 mm diameter silicon wafers, n-type, resistivity 20 Ohm.cm and thicknesses of 500 µm. Microstructures were patterned by positive photoresist HPR 504, Hunt Inc.,

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SENSOR SYSTEM FOR VAPOR TRACE DETECTION OF EXPLOSIVES

Motivation

Drago Strle 1976: Graduated at University of Ljubljana, Faculty for electrical engineering in Ljubljana 1981: B.Sc. at University of Ljubljana, Faculty for electrical engineering in Ljubljana 1991: Ph.D. in Electrical engineering with thesis: » Algorithms for Synthesis of Switched-Capacitor circuits « at University of Ljubljana, Faculty for electrical engineering in Ljubljana (with collaboration to IskraEmeco) From 1991: Employed at University of Ljubljana, Faculty for electrical engineering, LMFE 2012: Habilitated as associate professor, University of Ljubljana Most important work: STRLE, D., ŠTEFANE, B., NAHTIGAL, U., ZUPANIČ, E., POŽGAN, F., KVASIĆ, I., MAČEK, M., TRONTELJ, J., MUŠEVIČ, I.. Surface-functionalized MEMS capacitive sensors and CMOS electronics for vapor Trace detection of explosives. IEEE Sens. Journal. [Print ed.], 2012, vol. 12, issue 5, 1048-1057. GREGOROVIČ, A., APIH, T., KVASIĆ, I., LUŽNIK, J., PIRNAT, J., TRONTELJ, Z., STRLE, D., MUŠEVIČ, I.. Capacitorbased detection of nuclear magnetization: Nuclear quadruple resonance of surfaces. J. magn.reson. (San Diego, Calif., 1997) 2011, vol. 209, no. 1, 79-82.

Detecting vapor traces of different materials in the atmosphere is a potentially powerful method to reveal the presence of explosives, land mines and other hazardous materials. The detection method is based on the fact that these materials constantly emit rather small, but detectable number of molecules that constitute the material. In this work, we describe a sensor measurement system, where extremely small capacitance change caused by the adsorption of the target molecules to the surface of a functionalized MEMS capacitor, is measured. FixedCOMB fingers of each sensor are modified with different selfassembled mono layers on SiO2 surface that preferentially adsorb different target molecules. Using extremely sensitive electronic measurement system makes it possible to detect small amounts of molecules in the air. Differently modified differential sensors serve for selectivity improvements. Achieved sensitivity for TNT molecules adsorbed on APS modified sensor is 3ppt/√Hz and approximately ten times better for RDX.

Figure 3.12: SEM micrographs of a COMB sensor

NH2 NH2

Common limitations of existing detection systems are: large in size, high power consumption, unreliable detection with false alarms, insufficient sensitivity and chemical selectivity, hyper-sensitivity to environmental influences, and extremely high price. Our motivation is to build a sensor

NHCONH2

O Si O O

O Si O O

O Si O O

APS

APhS

UPS

Figure 3.13: Chemical modification molecules

system with improved characteristics compared to the ones listed above, with very small physical dimension and extremely small power consumption.

STRLE, D. Low noise signal processing for MEMS/NEMS based chemical/biological sensors: a system perspective. Slov.vet. res. [English ed.], 149-154.

Figure 3.14: SIP composed of 2 diff. sensors and the ASIC

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STRLE, D., ŠTEFANE, B., MUŠEVIČ, I.. Detecting vapor traces of explosives using a self-assembled mono layer on a surface-modified MEMS capacitor and CMOS electronics. V: 7th IEEE International Conference on Nano/Micro Engineered and Molecular Systems, Kyoto, Japan, 5-8 March 2012. IEEE-NEMS 2012. [Piscataway]: Institute of Electrical and Electronics Engineers: = IEEE, cop. 2012, 86-89

Figure 3.15: Response of APS modified sensor to TNT

Figure 3.16: Response of differently modified sensors (UPS, APS, NO, APHS) to RDX vapor in Lab. Environment

Results

channel. Integrating all elements described above in a SiP (Fig. 3.14), it is possible to detect less than 3ppt of TNT in the atmosphere using only a few 3 mm and 10mW power. The result of the sensitivity measurements to TNT vapors in an N2 atmosphere is presented on Fig, 4. The demonstrator has been built and consists of four differently modified differential sensors and integrated CMOS electronics in 2 SIPs. The achieved sensitivity is better than 3ppt/√Hz (3 TNT molecules in 10+12molecules of N2 in 1Hz bandwidth) at 25°C and approx. 10 times better for RDX. The sensitivity can be easily improved 10 times, while the selectivity will improve with a bigger array of differently modified sensors.

The central part of the detection measurement system is a surfacemodified differential capacitive sensor shown in Fig. 3.12.The modification chemistry is for 3 different modification molecules presented on Fig. 3.13. Each differential sensor is composed of two COMB capacitors covered with a thin layer of SiO2; only one is chemically modified. Equal number of target molecules is on average present in the space between the plates of both capacitors; the target molecules adsorb preferentially for a short time to the surface of the modified capacitor, changing its relative dielectric constant. Using appropriate excitation signals and extremely low noise electronics it is possible to measure the difference of capacitances of two differently modified differential pairs in one

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PRECISION ELECTRONIC WATT-HOUR ENERGY METER WITH BIST

Motivation

Uroš Bizjak 1996: Graduated at University of Ljubljana, Faculty for electrical engineering, Ljubljana 1996: Employed at IskraEmeco 2000: B.Sc. at University of Ljubljana, Faculty for electrical engineering in Ljubljana 2006: Ph.D. in Electrical engineering at University of Ljubljana, Faculty for electrical engineering in Ljubljana (with collaboration to IskraEmeco) From 2006: Head of Basic development group in Research and Design From 2011: Member of Application technology group in Research and Design

calculates in real time effective values of voltage, as well as current signals. The circuit also detects sag and swells on the measured AC voltage and passes these events to the controlling microprocessor for logging and further processing.

An integrated monolithic circuit of a precision smart electronic watt-hour meter is used in a measurement of a consumed electrical energy at the installation. The circuit comprises high performance low-noise analog measurement subsystem and dedicated hardwired digital signal processor, both in the close proximity on the same silicon die. The analog part samples voltage and current signals from voltage and current sensor, conditions and amplifies both signals with a low-noise operational amplifier and passes adjusted signals to state-ofthe-art high-performance delta-sigma analog-to-digital converters. The signals in their digital form are carried into digital signal processor, where they are further filtered, phase shifted and processed in order to calculate active, reactive and apparent energy. Besides these fundamental calculations, the signal processor

The implementation is based on a deep sub-micron CMOS technology, mainly due to the possibility of high level of integration of complex mixed-signal electronics circuits. In addition to the high level of integration; deep submicron CMOS technologies also enable the production of cheap, low power system-on-chip devices that have small footprint on a printed circuit board. High integration and consequently small transistor geometries are unfortunately reflected in degraded properties of basic building elements of analog electronic circuit structures. The main drawbacks of deep sub-micron technologies are: crosstalk of switching noise from the digital part of the circuit

Most important work: BIZJAK, U., STRLE, D.. IEC class 0.5 electronic watt-hour meter implemented with first-order sigmadelta converters. AEÜ, Int. j. electron. commun. , 2005, vol. 59, 447-453. RIBNIKAR, R., BIZJAK, U., STRLE, D.. Efficient built-in self-test of a highprecision electronic watt-hour meter, Inf. MIDEM, 2011, Vol. 41, No. 3, 222228, ROZMAN, M., PERNE, J., STRLE, V., BIZJAK, U., KOSMAČ, M.. Integriranovezje, predvideno za merilnik električne energije: patent številka SI 21580 A. Ljubljana: Urad Republike Slovenije za intelektualno lastnino, 2005.

Figure 3.17: Layout of SoC, which implements precision integrated watt-hour meter IC

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Figure 3.18: Modern multi-tariff electronic three-phase watt-hour meter

to the sensitive analog part, hard to implement precise measurement and reliability of the implementation. A technological analysis is necessary before the circuit is carried out in the deep sub-micron CMOS technology, as well as impact analysis of non-idealities of degraded basic building blocks on the measurement performance of the circuit. Due to close proximity of the circuits, it is also necessary to analyze mutual disturbances between separate blocks and to derive strategies to lower their impact on the circuit performance. Due to the complexity of the sub circuits, it is necessary to find appropriate testing strategies that include self-testing and BIST (built-inself-test) functionality, in order to substantially reduce the production testing time. In addition, since parameters degrade over time, it is also necessary to implement self-test during normal operation of the circuit to

periodically check for performance degradations.

possible

Results Measured results of the prototypes show that these advanced design strategies that are introduced into circuit design, lead to high performance and high quality SOC (system On Chip) integrated circuit for precision electronic watt-hour meter, implemented out in deep sub-micron CMOS technology. The prototype electronic watt-hour meter satisfies class 0.5 IEC requirements, with a load current ranging from 50mA to 120A. At the same time, advanced internal signal processing substantially reduces the computation load on the central microprocessor and makes possible additional BIST functionality.

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THz SYSTEM / CAMERA DEMONSTRATOR

The usage of THz waves in different applications is growing daily. Although the main applications for THz are currently found in security systems, huge potential is seen in applications in medical research and diagnostic and for industrial purposes for a determination of chemical compositions and for different measurements.

Janez Trontelj 1965: E.E. degree from the Faculty of Electrical Engineering, University of Ljubljana, Slovenia 1965: Employed at University of Ljubljana 1970: M.E. degree from the Faculty of Electrical Engineering, University of Ljubljana, Slovenia 1971: Ph.D. degree from the Faculty of Electrical Engineering, University of Ljubljana, Slovenia Current position: Head of the Laboratory for microelectronics; full Professor teaching Measurements in electronics, Measurements in telecommunications and Microelectronic technologies From 2010: head of the RRP3 project at CO NAMASTE Most important work: TRONTELJ, J., MAČEK, M., SEŠEK, A., ŠVIGELJ, A. Uncooled THz system for hidden object detection. V: LEITNER, R. (ur.), ARNOLD, T. (ur.). International THz Conference 2011 : Nov. 24-25, 2011, Villach, Austria. [Wien]: Österreichische Computer Gesellschaft, cop. 2011, 41-47. TRONTELJ, J., SEŠEK, A., MAČEK, M.. THz sensor array operating at room temperature. V: RTO-MP-SET-169 PRE-RELEASE. [S. l.]: NATO RTO, 2011, 1-8. PAVLOVIČ, L., TRONTELJ, J., KOSTEVC, D.. 300 GHz microbolometer doubledipole antenna for focal-plane-array imaging. V: LEITNER, R. (ur.), ARNOLD, T. (ur.). International THz Conference 2011 : Nov. 24-25, 2011, Villach, Austria. [Wien]: Österreichische Comp. Gesellschaft, cop. 2011, 155-160.

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THz waves penetrate almost all nonmetallic materials and tissues but their penetration strongly depends on the water content, because water greatly reduces the signal. One of the conditions for THz system testing is the observation of the operation in various weather conditions and at the different levels of air humidity. c)

The system that developed in the LMFE has a central frequency of 300GHz where the so-called atmospheric "window" is present. This means that the influence of moisture in the air is greatly reduced. The core system is the bolometer sensor system with associated antenna, shown in Figure 3.19. Acquiring a reasonable picture demands the use of multiple sensors, for this reason the sensors are grouped together in a line in a set of four sensors. The sensor imager has four lines and combines a total of 16 sensors. Sensor imager also includes signal processing and bias electronics. The main idea is to connect the receiver antenna to the bolometer with matched impedances. The antenna is tuned to a specific frequency (300 GHz). The gathered energy is transferred from the antenna to the bolometer which heats up and changes its resistance. Constant current flow through the bolometer and the change

Figure 3.19: a) SiN membrane based antenna – bolometer couple with connectors b) Dipole with bolometer and bias c) Micrograph of Ti bolometer dimensions 15 µm x 1.5 µm

in resistance produce a change in the voltage drop which is proportional to the energy gathered at the receiver antenna. The voltage is converted into digital and used in further signal processing. The system operates in two modes. In the first mode ("transparent mode") the signal travels from the THz generator trough the observed object to the sensor. The system with

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Figure 3.20: a) Measurement system for transparent mode, b) Image of a leaf, c) THz image of a leaf

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PLETERĹ EK, A., TRONTELJ, J.. A selfmixing NMOS channel-detector optimized for mm-wave and THZ signals. J. infrared millim. terahertz waves (Print), 2012, vol. 33, no. 6, 615626. Ĺ VIGELJ, A., TRONTELJ, J.. THZ imaging system for hidden objects detections = THZ vizijski sistem za odkrivanje skritih predmetov. Inf. MIDEM, jun. 2011, vol. 41, no. 2, 139-143

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Figure 3.20: a) Measurement system for transparent mode, b) Image of a leaf, c) THz image of a leaf

measured results is presented in Figure 3.20.

observed object to the imager. The mobile measurement system for the reflection mode is presented in Figure 3.21a.

Figure 3.20a presents the measurement system with the THz generator, mirror, observed object, lens and imager. Figures 3.20b and 3.20c present the observed object and its THz image. In the second mode ("reflection mode") signal travels from the THz generator and reflect from the

Figure 3.21b and 3.21c present the observed object, while Figure 3.21d presents the THz image of the observed object under a cotton cloth.

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Nematic colloids Optical microresonators Liquid crystal microlasers Laser-induced defect printing Colloidal and confined blue phases Actuation of liquid crystal elastomers Molybdenum and tungsten based nanomaterials Optical liquid crystal shutters for eye protection

Soft composites 59


RRP4

Soft composites for optical, electronic, photonic, and sensor applications Motivation

Slobodan Žumer 1973: Ph.D. in Physics at University of Ljubljana, Slovenia, Determination of short quadrupolar spin-lattice relaxation times in solid state with hnuclear quadrupole double resonance 1974-75 Post-doctoral fellow Universite Libre de Bruxelles 1984-86 Visiting Scientist LCI, Kent State University, Kent OH 1987 - present Full Professor of Physics at University of Ljubljana & scientific adviser at Jozef Stefan Institute, Ljubljana, Slovenia 1992-93 Visiting Professor at LCI, Kent State University, Kent OH 2004-14: Head of National Research program Physics of soft matter, surfaces, and nanostructures 2010-13: Head of the RRP4 project at CE NAMASTE Selected recent publications: RAVNIK, M., ALEXANDER, G. P., YEOMANS, J. M., ŽUMER, S. Threedimensional colloidal crystals in liquid crystalline blue phases. Proc. Natl. Acad. Sci. U. S. A., 2011, vol. 108, 51885192. TKALEC, U., RAVNIK, M., ČOPAR, S., ŽUMER, S., MUŠEVIČ, I. Reconfigurable knots and links in chiral nematic colloids. Science (Wash. D.C.), 2011, vol. 333, issue 6038, 62-65. ČOPAR, S., ŽUMER, S. Nematic braids: Topological invariants and rewiring of disclinations. Phys. Rev. Lett., 2011, vol. 106, 177801-1-177801-4.

important is large susceptibility of the materials to external stimuli, like optic, electric, and mechanic fields, as it is of central importance for applications. The academic research is complemented by the work and development in two partner companies. The high-tech company Balder d.o.o. successfully competes at a world level and controls a large share of the world market in special liquid crystal light shutters for personal eye protection. The small spin-off company Nanotul is active in the field of inorganic nanoparticles and nanofibers. Central to the work of partners is multidisciplinarity of the fields (condensed matter, surfaces, soft matter, nanoparticles) and complementarity in the approaches (experiments, theory, modeling, simulations, technology, and marketing). In summary, our project is a successful synergy, which developed and can further develop molecular, mesoscopic and macroscopic soft composite materials useable and to be used in optic, photonic, actuation, and sensor devices, as acknowledged by multiple international standards, awards, publications, patents and simple personal responses of top-edge international experts.

Soft composites are complex advanced materials which are designed to perform differently and to perform better, in particular in optic, photonic, and nano-technological applications. Our Centre-of-Excellence research module joined partners from different backgrounds and expertise –physics, optics, chemistry, nano-sciences & optics- to contribute, as part of the CoE NAMASTE, to the fundamental goal of developing advanced materials and technologies for the future. Here, in this booklet, we showcase several selected highlights of our work –some concepts are worldwide first-, including colloidal microscopic knots and links, efficient and tuneable droplet resonators, 3D omnidirectional lasers, laser induced printing of optical defects, fluid driven self-assembly of 3D colloidal crystals, actuated elastomers for artificial muscles, nanomaterial additives for lubricant oils, and optical LCD shutters for eye protection. Introduction Our module aimed at exploiting our expertise in the field of mesogenic soft matter and anorganic nanostructures to develop ground for new high-tech applications. The achievements of our experimental condensed matter physics labs for Soft Matter, Surfaces, and Nanostructures at Jožef Stefan Institute, theoretical&modelling group for Soft Matter Theory & Simulations at the Faculty for Mathematics and Physics at University of Ljubljana, and partner companies Balder and Nanotul are at the top edge of science and applications in these fields. We develop novel complex materials with specific targeted optic, photonic, electronic, and mechanic properties. Particularly

Results of our project RRP4 in numbers Our NAMASTE research achivements in part based on the new NAMASTE equipment (See Apendix!) can be briefly summarized in-numbers as (from 2010): 25 scientific papers in international journals, including highest level: 1x Science, 1x Nature Communications, 3x Physical Review Letters, 2x PNAS-USA; 30 plenary and invited lectures; 2 EU & 2 US patents and 4 prototypes. Highlights from our 8 work packages H1: NEMATIC COLLOIDS: ASSEMBLING TOPOLOGICAL SOFT MATTER Worldwide first assembly and knitting of arbitrary microscopic knots and links was demonstrated, using defect lines in nematic colloids (Fig. 4.1) H2: NEMATIC DROPLETS AS TUNABLE OPTICAL MICRORESONATORS Nematic droplets are demonstrated to work as highly tunable and high-Q optical microresonators (Fig. 4.2).

Figure 4.1: (left) Experimental and modeling realization of Hopf link. (right) Modelling prediction of defect-states in opal nematic colloids

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H3: LIQUID CRYSTAL MICROLASERS Worldwide first three-dimensional omni-directional laser was demonstrated in polymer dispersed and dye-doped chiral nematic spherical cavites (Fig. 4.3).

Partners: Institut „Jožef Stefan“ http://www.ijs.si

H4: LASER-INDUCED PRINTING OF NEMATIC DEFECTS Figure 4.2: Polarization micrograph of nematic droplet microresonator

Imprinting of complex optical nanoand micro-patterns with LaguerreGaussian laser beams was demonstrated by using advanced computer modeling (Fig. 4.4).

Univerza v Ljubljani http://www.uni-lj.si

H5: COLLOIDAL AND CONFINED BLUE PHASES First self-assembly using regular internal structure of a complex blue phase fluid was demonstrated, showing 3D, quasi-2D and 2D colloidal crystals (Fig. 4.5).

Figure 4.3: Lasing from a cholesteric droplet

Balder Optoelectronic Elements and Measuring Systems, Ltd www.balder.eu

H6: ACTUATION OF LIQUID CRYSTAL ELASTOMERS The combined experimental and modeling research lead to development of a new generation of soft materials, with reversible mechanical deformation of the magnitude by far exceeding the one found in solid materials and triggerable by nonthermal means (Fig. 4.6).

Figure 4.4: Index l=1 laser imprinted optical pattern; red shows variation of the optical axis

Nanotul d.o.o. http://www.nanotul.com

H7: NANOMATERIAL ADDITIVES FOR LUBRICATING OILS MoS2 nanotubes were developed as new functional additives to oils and greases for friction reduction, and as graphene analogues; WS2 flakes were used to fabricate field effect transistors (Fig. 4.7).

Figure 4.5: Three-dimensional colloidal crystals self-assembled using blue phase II complex fluid

H8: OPTICAL LIQUID CRYSTAL SHUTTERS FOR EYE PROTECTION STN LC light shutters and their angular compensation by means of the negative c-plate birefringence was developed, producing world first active LC welding filters (Fig. H) with the highest optical quality (1/1/1/1) according to international Standard EN 379.

Figure 4.6: Mesogenic structure of deformed nematic elastomer, as predicted by numerical simulations

Figure 4.7: Micrographs of wear scars on the steel discs (a) without or (b) with MoS2 nanotube lubrication

Figure 4.8: World highest standard welding helmet BH3, developed and produced by Balder

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NEMATIC COLLOIDS: ASSEMBLING TOPOLOGICAL SOFT MATTER Motivation

EXPERIMENTS Igor Muševič 1993: Ph.D. in Physics at University of Ljubljana, Slovenia, with thesis: Študij elementarnih eksitacij v feroelektričnem tekočem kristalu From 1995: Head of AFM Laboratory at Jožef Stefan Institute From 2006: Head of Condensed Matter Physics Department at Jožef Stefan Institute (JSI) From 2007: Full Professor of Physics at University of Ljubljana (FMF UL), Slovenia From 2010: Principal Investigator at CE NAMASTE and CE Nanocenter Selected publications: IMUŠEVIČ, I., BLINC, R., ŽEKŠ, B. The Physics of ferroelectric and antiferroelectric liquid crystals. World Scientific, Singapore (2000). MUŠEVIČ, I., ŠKARABOT, M., TKALEC, U., RAVNIK, M., ŽUMER, S. Twodimensional nematic colloidal crystals self-assembled by topological defects. Science, 2006, 313, 954-958. MUŠEVIČ, I., ŠKARABOT, M., BABIČ, D., OSTERMAN, N., POBERAJ, I., NAZARENKO, V., NYCH, A. Laser trapping of small colloidal particles in a menatic liquid crystal: clouds and ghosts. Phys. Rev. Lett., 2004, vol. 93, 187801-1-187801-4. Coworkers: Uroš Tkalec, Miha Škarabot, Venkata S. R. Jampani, Marryam Nikkhou

Topology is a mathematical discipline focused on connectedness, i.e. how objects (in mathematics, spaces) transform one into another by reshaping but not by cutting and gluing. However, only very recently, topology proved new major value as a tool for designing novel materials with advanced and incomparable topological- material characteristics. And nematic colloids are one of the materials at the forefront of this research. Figure 4.9: Threefold disclination profile visualized by using the splay-bend parameter. (b–e) Entangled dimmers characterized by self-linking number, writhe, and free energy differences relative to the the ground state

Here, we show that arbitrary (i.e. any) microscopic knots and links can be knotted from disclination defect lines, surrounding micro-sized colloidal particles in nematic complex fluids, thus forming unusual topological soft matter – the nematic braids. Geometrical diversity of defect lines, the richness of entangled structures and rewiring mechanism areparticularly interesting. More generally, from technological perspective, knotted nematic braids show fascinating and promising electro-optical properties for application in optics, photonics, and plasmonics.

31 5 m Figure 4.10: Trifoil knot realized on a 3x3 array of microscopic colloidal particles (left, see dark lines). Topologically, this knotted structure is equivalent to the final knot diagram (right), following the sequence of Reidemesiter moves

Nematic braids Experiments with nematic braids show a rich variety of knotted and linked defect lines that can be rewired by optical manipulation [1-3]. These structures exhibit symmetry and topological diversity, allowing us to combine diffe- rent classification tools and create a unified description for entire classes of different structures. Čopar and Žumer [4] demonstrate the use of tetrahedral rewiring for classification of entangled states in different geometries. We intro-duce a new topological invariant – self-linking number, which characterizes the internal twisted structure of the disclination loops (see Fig. 4.9). We also unveil a rewiring scheme for the crossing of two threefold disclinations, based on tetra- hedral rotations of relevant segments [5], which allows us to predict all possible nematic braids.

Figure 4.11: Example of complex two-component link with five crossings. Oppositely twisted nematic domains appear in different colors if observed under crossed polarizers

colloidal dispersion of glass microspheres in a nematic liquid crystal (Figs. 4.10 and 4.11). Experimentally, laser tweezers are used to systematically assemble and analyze the knotted structures, using both intensity and position variability to

Knots and links Worldwide first we present experimental realisation and theoretical interpretation of microscopic knots and links, using

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effectively tie the knots. Using the optical tweezers, we can also change a specific knot into a different knot, changing locally the knot tangles. To explain and classify the observed knots and links, a theoretical approach is developed, based on phenomenological theory and topological methods [1, 4]. Tailoring knots to order was achieved through computer modeling of polynomial invariants, tangle specification and appropriate array size, resulting in a made-to-order assembly process (Fig. 4.12). Combining experiments and theory, thus, we have found a way to create arbitrary microscopic knots.

Figure 4.12: Made-to-order assembly of Borromean rings on a 4x4 particle array. The feasible tangle combinations are tested with the numerical algorithm and the selected configuration is identified by direct comparison with Jones polynomials

SIMULATIONS & THEORY Slobodan Žumer

Coworkers: Miha Ravnik, Simon Čopar, Tine Porenta, David Seč

More generally, knots and links are objects studied within the mathematical discipline knot theory and have always had an imported role in human history, like in building, sailing, handcraft and art. Knots have – of course- prominent role also in modern science, where knotting of DNA, knotting of light, and knotted magnetic vortices in type II superconductors are only some best known examples. From application perspective, the knots and links in nematic colloids are opening a fundamentally new route for binding and fabrication of photonic microstructures with advanced topology that could control the flow of light at micro and nano-scale..

Figure 4.13: Trifoil knot realized on a 3x3 array of Entangled colloidal dimer in chiral -cell can be rewired at four different sites (A-D). Each of the sites can assume states [X], [R] or [L], producing 81 configurations, 36 of which are different

TKALEC, U., RAVNIK, M., ČOPAR, S., ŽUMER, S., MUŠEVIČ, I. Reconfigurable knots and links in chiral nematic colloids. Science, 2011, vol. 333, no. 6038, 62-65.

Colloidal entanglement has further functionality if using highly twisted nematic cells, effectively giving more rewiring sites and more complex dstructures [2, 3] (Fig. 4.13). Indeed, increasing chirality of the liquid crystal facilitates and gives even spontaneous formation of linked and entangled colloidal patterns.

Figure 4.14: Spherical colloidal particle can be topologically attached to the optical fiber. . While merging with a -1/2 loop produces ordinary entangled state, merging with a +1/2 loop creates a hybrid nematic disclination

Topological charges on micro-cylinders We performed experimental analysis of topological defects around homeotropic optical fibers immersed in nematic, studying the topological characteristics of disclination loops. Topologically, such configuration allows for a sequence of alternating 1/2 disclination loops and if their separation is sufficiently large, they are stable. It is also possible use such loops to attach colloidal particles to optical fibers (Fig. 4.14). More generally, the presented system is interesting because it represents a controllable »topological reactor«, capable of direct testing and application of topological conservation laws.

The scientific achievements include:  Worldwide first design and production of arbitrary microscopic knots and links, using defect lines in nematic colloids.  Classification of topological states within the standard knot theory, extended by the new topological invariant called self-linking number.  New topology-based strategy for targeted design of complex micro- and nano-structures, demonstrating topological soft matter.

Summary and Deliverables

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JAMPANI, V. S. R., ŠKARABOT, M., RAVNIK, M., ČOPAR, S., ŽUMER, S., MUŠEVIČ, I. Colloidal entanglement in highly twisted chiral nematic colloids : twisted loops, Hopf links, and trefoil knots. Phys. Rev., E Stat. nonlinear soft matter phys. (Print), 2011, vol. 84, no. 3, 031703-1-031703-9. ČOPAR, S., PORENTA, T., JAMPANI, V. S. R., MUŠEVIČ, I., ŽUMER, S. Stability and rewiring of nematic braids in chiral nematic colloids. Soft Matter, 2012, vol. 8, issue 33, 8595-8600. ČOPAR, S., ŽUMER, S. Nematic braids: Topological invariants and rewiring of disclinations. Phys. Rev. Lett., 2011, vol. 106, 177801-1-177801-4. ČOPAR, S., PORENTA, T., ŽUMER, S. Nematic disclinations as twisted ribbons. Phys. Rev., E Stat. nonlinear soft matter phys., 2011, vol. 84, issue 5, 051702-1-051702-7. DONTABHAKTUNI, J., RAVNIK, M., ŽUMER, S. Shape-tuning the colloidal assemblies in nematic liquid crystals. Soft Matter, 2012, vol. 8, issue 5, 1657-1663.


NEMATIC DROPLETS AS TUNABLE OPTICAL MICRORESONATORS Introduction

EXPERIMENTS Igor Muševič

Coworkers: Matjaž Humar, Stane Pajk LAGERWALL, J. P. F., SCALIA, G. A new era for liquid crystal research: Applications of liquid crystals in soft matter nano-, bio- and microtechnology. Curr. Appl. Phys., 2012, vol. 12, 1387-1412. VAHALA, K. J. Optical microcavities. Nature, 2003, vol. 424, 839-846. HUMAR, M., RAVNIK, M., PAJK, S., MUŠEVIČ, I. Electrically tunable liquid crystal optical microresonators. Nat. Photonics, 2009, vol. 3, no. 10, 595600. MUŠEVIČ, I., ŠKARABOT, M., HUMAR, M. Direct and inverted nematic dispersions for soft matter photonics. J. Phys.Cond. Matter, 2011, vol. 23, 284112-1-284112-7. MAUNE, B., LAWSON, R., GUNN, C., SCHRERER, G., DALTON, L. Electrically tunable ring resonators incorporating nematic liquid crystals as cladding layers. Appl. Phys. Lett., vol. 83, no. 23, 4689-4691 (2003). WANG, T.-J., CHU, C.-H., LIN, C.-Y. Electro-optically tunable microring resonators on lithium niobate. Opt. Lett., 2007, vol. 32, no. 19, 2777-2779. KIRAZ, A., KARADAG, Y., COSKUN, A. F. Spectral tuning of liquid microdroplets standing on a superhydrophobic surface using electrowetting. Appl. Phys. Lett., 2008, vol. 92, 191104-1191104-3. LIN, I-H., MILLER, D. S., BERTICS, P. J., MURPHY, C. J., DE PABLO, J. J., ABBOTT, N. L. Endotoxin-induced structural transformations in liquid crystalline droplets. Science, 2011, vol. 332, no.6035, 1297–1300. HUMAR, M., MUŠEVIČ, I. Surfactant sensing based on whispering-gallerymode lasing in liquid-crystal microdroplets. Opt. Express, 2011, vol. 19, no. 21, 19836-19844.

In recent years, great attention has been paid to the development of microoptical components and integrated photonic circuits. Small size, easy and cheap manufacturing, tens of gigahertz clock rate, nonlinear response and tunability are the main properties that scientist and companies are searching for. Among them, tunability in a broad interval of optical wavelengths is very difficult to achieve using solid state components. Liquid crystals have large response to external stimuli, like electric and magnetic fields, temperature, interfacial adsorption, chemical substances and light. These influences change their optical properties, which can be used for broadband tuning of photonic components [1]. External electric field from your laptop battery is used to control the structure of a thin layer of a liquid crystal and optical transmission of each pixel of the screen. Millions of tiny liquid crystal droplets are embedded in a polymer matrix in PDLC switchable windows and can be switched by external electric field. In this work we have used individual liquid crystal micrometer-sized droplets as whispering gallery mode (WGM) microresonators. These are photonic devices that can trap and store light by means of total internal reflection [2].

Figure 4.15: Micrograph of a radial 15 μm droplet of nematic liquid crystal E12 in PDMS.

Figure 4.16: Fluorescent light intensity from a LC droplet. The droplet is illuminated by Ar+ laser near the left edge (black cross).

Methods The droplets were prepared by mixing a small amount of fluorescently labeled nematic liquid crystal and polydimethylsiloxane (PDMS) or water. The PDMS was polymerized and the liquid crystalline droplets obtained radial configuration of the nematic director with a point hedgehog defect at the center (Fig. 4.15). An Ar-ion laser beam was focused to the rim of a single droplet using a microscope (Fig. 4.16 and 4.17), thus exciting fluorescence. The spectrum of fluorescent light was analyzed using an optical spectrometer.

Figure 4.17: Schematic view of WGMs in a LC droplet. WGMs are excited by a focused Ar+ laser (green light illuminating the edge of the droplet). Only the light radiating towards the microscope objective is detected (red cone)..

Results A series of well resolved peaks were observed in the spectrum of light coming from an illuminated droplet, corresponding to WGM resonances (Fig. 4.18). These resonances can be considered as light, circulating inside the microdroplets, bouncing-off the interface by total internal reflection. There are two sets of resonances,

Figure 4.18: WGM resonances in a 12.6 μm droplet of E12 in PDMS. The inset shows details of a WGM spectral line in a 53 μm-diameter E12 droplet. The linewidth is approximately 0.055 nm, and the LC cavity Q-factor is of the order of 12.000.

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because liquid crystals are birefringent. The TM resonances sense the extraordinary index and the TE resonances sense the ordinary index. The mode numbers of the observed peaks were identified by calculating the resonant frequencies using analytical solutions of Mie type for the electric and magnetic field. When an electric field was applied to the droplet we achieved shift of WGM resonances of the order of 20 nm at 2.6 V/µm in 17 µm diameter droplets, as shown in Fig. 4.19 [3,4]. This is nearly two orders of magnitude larger compared to similar effects in solids [5-7]. The tunability is due to the electric field induced distortion of the nematic LC in the droplet. The distortion effectively lowers the refractive index seen by the TM modes, shifting them to shorter wavelengths (Fig. 4.19). The shift is almost linear and completely reversible. The tuning speed is of the order of ten milliseconds and is limited by the response time of the NLC.

Figure 4.19: Electric-field-induced wavelength shift of WGM resonances in a 16.1 μm diameter microresonator made from dye doped E12 nematic liquid crystal. Color scale indicates intensity of detected light.

the interface between the liquid crystal and water, changing the surface alignment of the liquid crystal [8]. We have demonstrated that the presence of 0.3 mM concentration of sodium dodecyl sulfate surfactant in water induces significant and clearly detectable changes in the lasing spectrum from WGMs [9]. The developed sensing method could be easily integrated into existing microfluidic devices. Monitoring and automated recognition of the lasing spectra from liquid-crystal microdroplets has therefore a clear advantage in comparison to the conventional observation of individual droplets under an optical microscope and could provide efficient and automated readout of the presence of targeted molecules in water surrounding the liquid-crystal microdroplet sensor.

Tuning of the WGMs was further achieved by changing the temperature [4]. For the liquid crystal used, the extraordinary index decreases as the temperature is increased, whereas the ordinary index increases. Therefore, as the temperature is increased the TM modes should shift to shorter wavelengths and the TE modes to longer wavelengths. This is indeed observed in the experiments. For the temperature range from 27°C to 55°C a spectral shift of 20 nm was achieved for TM modes and 13 nm for TE modes. WGMs are also tunable by strain, as demonstrated on a 150 µm thick free standing film of PDMS, containing liquid crystal droplets. The film was stretched up to 15% so that the droplets deformed into ellipsoids. This caused an increase or decrease of the path of circulating light, depending on the plane of circulation. The measured shift was around 30 nm for 15% strain [4].

Conclusions Liquid crystal WGM resonators have great potential in future micro-photonic circuits as well as in basic research. From the application point of view this work could have impact on the development of a number of tunable photonic devices, such as microlasers, narrow filters, optical switching and routing, ultrasensitive biosensing, temperature and displacement measurements and high resolution spectroscopy. The developed elements could be useful not just for commercial applications, but also in various studies such as nonlinear optics, cavity quantum electrodynamics and single photon sources.

Spectral shifts of LC droplets exceed their free spectral range, meaning that the resonator frequencies can be shifted to any value. Liquid crystal microdroplets could be used as tunable optical microresonators but also as temperature and strain sensors. Liquid crystal droplets can also be used as chemical sensors. The molecules that we want to detect can be absorbed to

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MODELING Miha Ravnik 2009: Ph.D. in Physics at University of Ljubljana, Slovenia, with thesis: Colloidal structures confined to thin nematic layers From 2005: employed at Faculty of Mathematics and Physics, University of Ljubljana, Slovenia From 2009: Postdoctoral researcher at University of Ljubljana (FMF UL), Slovenia 2009-2012: Postdoctoral research fellow at University of Oxford, UK From 2011: partialy employed at CoE NAMASTE Selected publications: RAVNIK, M., ŠKARABOT, M., ŽUMER, S., TKALEC, U., POBERAJ, I., BABIČ, D., OSTERMAN, N., MUŠEVIČ, I. Entangled nematic colloidal dimers and wires. Phys. Rev. Lett., 2007, vol. 99, no. 24, 247801-1-247801-4. RAVNIK, M., ALEXANDER, G. P., YEOMANS, J. M., ŽUMER, S. Mesoscopic modelling of colloids in chiral nematics. Faraday discuss., 2010, vol. 144, 159-169. RAVNIK, M., ALEXANDER, G. P., YEOMANS, J. M., ŽUMER, S. Threedimensional colloidal crystals in liquid crystalline blue phases. Proc. Natl. Acad. Sci. U. S. A., 2011, vol. 108, 51885192.


LIQUID CRYSTAL MICROLASERS Motivation

EXPERIMENTS Igor Muševič Coworker: Matjaž Humar, JSI

Photonic microdevices, such as integrated microlasers, have attracted huge interest for emerging photonic technologies. Today, most prototypes of photonic structures are made in 2D using standard lithographic methods. More interesting are 3D structures that confine light in all three dimensions, but they are very difficult to make using solid matter. One of these 3D structures is the spherical Bragg resonator that is made of concentric layers of alternating low and high refractive index [1]. Because of perfect spherical symmetry, the photonic bandgap is independent of direction and therefore strongly confines light in the center of the structure. By using standard lithographic methods 2D Bragg structures have been successfully realized and lasing has been demonstrated [2]. 3D onion microcavities were produced by chemical synthesis [3] or by etching and chemical vapor deposition [4], but lasing has not been achieved in 3D till recently.

Figure 4.20: 3D cholesteric liquid crystal laser. The yellow rods represent LC molecules that form a helix running outwards from the center of the droplet. The laser emits light from the center in all directions.

Experiment We have used a bottom up approach based on liquid crystals to make 3D Bragg microcavities. Liquid crystals are not only well-known for their large optical birefringence and high response to external stimuli, but they can also self-assemble in a variety of interesting structures. Chiral liquid crystals are especially interesting for photonics, because they spontaneously form a periodic-helical structure with the pitch comparable to the wavelength of light. Because of the periodic modulation of refractive index produced by the helix, there is a photonic bandgap in the direction of the helix. If a laser dye is added to such a liquid crystal and external excitation is used, the photonic structure can start to emit coherent laser light [5-7].

Figure 4.21: Lasing from the center of a droplet pumped by a pulsed laser

Figure 4.22: The intensity of the laser line as the pump laser intensity is increased. Lasing threshold can clearly be observed at ∼ 1.8 mJ/cm2

We have extended this well-known lasing principle in cholesteric liquid crystals from planar geometry (1D) into a spherical one (3D). A low birefringence nematic liquid crystal MLC-7023 was mixed with 25.5wt% of S-811 chiral dopant and 0.2wt% of Nile red fluorescent dye. A small quantity of this dye-doped liquid crystal was mechanically mixed into an immiscible carrier fluid such as glycerol. In the process of mechanical mixing thousands of droplets with different

sizes were produced. Each droplet has a spherulite structure (Fig. 4.20) [8,9] that corresponds to the layered structure with the helical pitch running out in a radial direction. Optically, this is a spherical Bragg onion resonator. Results A single droplet was observed under a microscope and illuminated by a

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pulsed, Q-switched doubled Nd:YAG laser. When increasing the pumping pulse energy, at one point a narrow spectral line appeared above the lasing threshold corresponding to a single mode lasing [10,11]. The linewidth was 0.1 nm and the laser line was positioned at 620 nm, matching the longer wavelength photonic bandgap edge of the LC. Lasing could also be observed as a bright spot in the center of the droplet (Fig. 4.21).

BRADY, D., PAPEN, G., SIPE, J. E. Spherical distributed dielectric resonators. J. Opt. Soc. Am. B, 1993, vol. 10, 644-657.

Figure 4.23: Angular dependence of the emitted intensity from a single 3D Bragg laser. The laser emits uniformly in all angles

Lasing was also confirmed by measuring the output intensity versus input energy of the pump laser. The measurements show typical threshold behavior that is characteristic for lasing (Fig. 4.22). Nearly all the droplets larger than 15 μm emitted laser light when excited. We have measured the average power of a 3D CLC Bragg laser to be up to 0.05 mW at a 200 Hz repetition rate.

that emits light isotropically in all directions and acts as a point source of light. Furthermore, the wavelength can be tuned by temperature by several tens of nanometers. A number of applications of the cholesteric onion microlasers is anticipated, such as holography, telecommunications, optical computing, imaging, sensing and even as a material for paints or light sources that emit coherent light in all directions. By polymerizing the liquid crystal itself, a more mechanically stable microlaser can be made, useful for example in biological imaging. Furthermore, the 3D cholesteric laser is also one of the simplest lasers to make in general. Only four commercially available substances are needed: a nematic liquid crystal, a chiral dopant, a fluorescent dye and a carrier fluid. No complicated mixing procedures are needed and the whole process can be completed in less than fifteen minutes in any laboratory. Coupled regular arrays of thousands and even millions of CLC microlasers could also be made. We anticipate that by using better materials and optimized material parameters, such as the concentration of the chiral dopant and of the fluorescent dye, it will be possible to further reduce the size and increase the tunability and the functionality of the cholesteric onion lasers. The CLC onion microlasers could also be combined with optical fiber waveguides to collect radiating light into the waveguides. Omnidirectional laser emission is the most relevant result of this work, and we have demonstrated that soft-matter has many advantages over the solid matter for future photonic technologies.

The lasing wavelength is not dependent on the droplet size and can be arbitrarily selected from UV to IR by utilizing liquid crystals with proper pitch length and a proper laser dye. By changing the temperature of the droplet, the cholesteric pitch is varied and the wavelength of the laser line can be tuned by several tens of nanometers. The temperature change of 13 K shifts the laser line by 40 nm. By measuring the angular dependence of the emission we have found that the emission is highly uniform (Fig. 4.23) and the laser is really emitting light isotropically in all directions. This laser is therefore acting as a coherent, pointlike, omnidirectional source of light. A number of other characteristics of the laser, such as the polarization, stability, linewidth as a function of droplet size and thresholds have been measured. Multimode lasing with several lasing lines has been achieved. Conclusions We have demonstrated the world's first 3D microlaser made of a cholesteric liquid-crystal microdroplet. The droplets were prepared by mechanical mixing of the cholesteric liquid crystal, laser dye and a carrier fluid. The liquid crystal spontaneously self assembles into an onion-like structure that works as a spherical Bragg reflector and has completely spherically symmetrical photonic bandgap. This is the first laser

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SHAW, A., ROYCROFT, B., HEGARTY, J., LABILLOY, D., BENISTY, H., WEISBUCH, C., KRAUSS, T. F., SMITH, C. J. M., STANLEY, R., HOUDRE, R., OESTERLE, U. Lasing properties of disk microcavity based on a circular Bragg reflector. Appl. Phys. Lett., 1999, vol. 75, 3051-3053. GOUREVICH, I., FIELD, L. M., WEI, Z., PAQUET, C., PETUKHOVA, A., ALTEHELD, A., KUMACHEVA, E., SAARINEN, J. J., SIPE, J. E. Polymer multilayer particles: A route to spherical dielectric resonators. Macromolecules, 2006, vol. 39, 14491454. XU, Y., LIANG, W., YARIV, A., FLEMING, J. G., LIN, S.-Y. Modal analysis of Bragg onion resonators. Opt. Lett., 2004, vol. 29, 424-426. COLES, H., MORRIS, S. Liquid-crystal lasers. Nat. Photonics 4, 676-685 (2010). KOPP, V. I., FAN, B., VITHANA, H. K. M., GENACK, A. Z. Low-threshold lasing at the edge of a photonic stop band in cholesteric liquid crystals. Opt. Lett., 1998, vol. 23, 1707-1709. SHIBAEV, P., CROOKER, B., MANEVICH, M., HANELT, E. Mechanically tunable microlasers based on highly viscous chiral liquid crystals. Appl. Phys. Lett., 2011, vol. 99, 233302-1-233302-3. BEZIĆ, J., ŽUMER, S. Structures of the cholesteric liquid crystal droplets with parallel surface anchoring. Liq. Cryst., 1992, vol. 11, 593-619. SEČ, D., LOPEZ-LEON, T., NOBILI, M., BLANC, C., FERNANDEZ-NIEVES, A., RAVNIK, M., ŽUMER, S. Defect trajectories in nematic shells: role of elastic anisotropy and thickness heterogeneity. Phys. Rev., E Stat. nonlinear soft matter phys., 2012, vol. 86, iss. 2, 020705-1-020705-4. HUMAR, M., MUŠEVIČ, I. 3D microlasers from self-assembled cholesteric liquid-crystal microdroplets. Opt. Express, 2010, vol. 18, no. 26, 26995-27003. MUŠEVIČ, I., HUMAR, M. Spherical liquid-crystal laser: patent application PCT/EP2011/005607. München: European Patent Attorneys, 8. 1. 2011.


LASER-INDUCED PRINTING OF NEMATIC DEFECTS Motivation

SIMULATIONS & MODELING Slobodan Žumer Coworkers: Miha Ravnik, Tine Porenta

The long range orientational order of nematic liquid crystal –the director – is well responsive to external fields, specifically optic and electric [1], causing reorientation of the director or changes in the birefringence due to absorption. Both these two mechanisms can be accessed with optical tweezers, therefore making them a natural tool for inducing and tuning structures and patterns in liquid crystals. Especially interesting are advanced tweezers with intensitymodulated and polarization-modulated light beams, like Hermitian and Laguerre-Gaussian (LG) beams [2] that can imprint complex defect structures like torons [3] (see Fig. 4.24).

Figure 4.24: Schematically presented toron, formed by complex laser beams in frustrated cholesterics [3].

profile. More specifically, we even control the dynamic trajectories in the formation of superstructures by predesigning time and space dependence of the optical fields.

Here, we show that optical tweezers with complex LG beam profiles induce and effectively imprint complex birefringent profiles in the liquid crystalline matrix, using the dual functionality of laser beam in liquid crystals: (i) the beam polarization imprints the local optical axis, whereas (ii) as a result of absorption, the beam intensity imprints the local birefringence.

Results If laser beam power is high enough to affect nematic ordering, i.e. it exceeds the optical Frèedericksz transition threshold in the high-intensity region, the nematic director aligns withthe direction of the polarization. The Laguerre-Gaussian optical beam is characterized by a winding number of the polarization profile l (Fig. 4.25), which is a topological invariant that commonly classifies topological defect lines. The induced nematic director field inside the beam reflects the polarization profile of the LG beam but with notable additional features. They arise from the localization of director perturbation and from director’s n to – n symmetry that allows for formation of disclination lines with half integer winding numbers. In the high-intensity beam regions (indicated by white shading), the director exactly follows the direction of the polarization as presented in Fig. 4.26. On the inner border of the high-intensity regions l

Methods The design of optical imprinting is performed by using advanced numerical modeling, complemented by experiments of collaborators. The challenge is to model advanced optical tweezers with functionalized optical beams of variable polarization and intensity profile, such as LG beams, to achieve selective and targeted formation of topological superstructures. The modeling is based on the minimization of the Landau–de Gennes free energy of a nematic in the external fields [4], extensively adapted for the optical fields [5,6]. The imprinted structures are actually coupled back to the optical fields of the laser beams and change their exact

Figure 4.25: Intensity and polarization profiles of various Laguerre-Gaussian modes. Beams with polarization windings numbers l = 0, 1, 2, 3 are shown. White color represents regions of high electric field intensity in two distinct beam-planes (perpendicular and parallel to the beam); black gives regions with zero intensity. Red arrows show the polarization within the plane of the beam waist. Lengths of the arrows indicate the magnitude of the polarization

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SIMONI, F., FRANCESCAN-GELI, O. Effects of light on molecular orientation of liquid crystals. J. Phys.: Cond. Matter, 1999, vol. 1, R439-R487 (1999). CURTIS, J. E., GRIER, D. G., Structure of optical vortices. Phys. Rev. Lett., 2003, vol. 90, 133901-1-133901-4. SMALYUKH, I. I., LANSAC Y., CLARK, N. A., TRIVEDI, R. P., Three-dimensional structure and multistable optical switching of triple twist toron quasiparticles in anisotropic fluids. Nat. Mater., 2010, vol. 9, no. 2, 139145. RAVNIK, M., ŽUMER, S. Landau-de gennes modelling of nematic liquid crystal colloids. Liq. cryst., 2009, vol. 10/11, 1201-1214.

Figure 4.26: Nematic structures field-stabilized by optical Laguerre Gaussian beams. Nematic structures induced by L-G beams with l = 0, 1, 2, 3 are presented in A, B, C, and D, respectively. Defect loops are drawn in yellow as isosurfaces of nematic degree of order S = 0.4. White shading visualizes regions with high beam intensity and black represents zero intensity regions. Director field is presented in a colored scheme: if red, the director is oriented along the z direction (along the beam); if blue, the director is parallel to the lateral (xy) plane. (E) Zoom-in of the director field, now in two perpendicular planes, for the l = 1 structure. (F) The transformation of the outer disclination loop from locally +1/2 defect line to -1/2 defect line is illustrated by director field lines

orthogonal defect rings are induced, their number exactly equal to the absolute value of the polarization winding number l. The symmetry in the positions of the defect rings reflects the symmetry of the polarization profile. Outside the high-intensity region of the optical beam, defect loop forms in the lateral (xy) plane. This loop is a result of the localization of the nematic deformation only to the region of high intensity, allowing the director outside the loop to be ideally uniformly aligned as preferred by the homeotropic cell. If

induced by the l=1 optical beam, the loop is a 1/2 twist disclination. For optical beams with other polarization winding numbers, the lateral defect loop exhibits complex variations from 1/2, twist, to +1/2 profile of the director field . Particularly important for imprinting of structures is the absorption of light in the bulk or at confining surfaces. The tweezers can locally ‘soften’ the nematic, resulting in easier formation of nematic defect structures in detail reviewed in Ref. 6 (see also Fig 4.27). Summary & Deliverables The scientific achievements include: • Using L-G beams, complex structures of high complexity are imprinted in the molecular orientational field of nematic liquid crystals. • Various mechanisms –confinement, presence of colloidal particles and chirality- stabiles the structures, making them energetically stable or metastable. •Methodologically, we developed a numerical modeling software tool that can predict and provide guidance for experimental realization of imprinting of topological structures by complex optical beams. The method can be further adapted for more complex confinement, anchoring profiles, and incorporation of colloidal particles.

Figure 4.27: Stretching and manipulation of nematic defect loop near a colloidal particle

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PORENTA, T., RAVNIK, M., ŽUMER, S. Complex field-stabilised nematic defect structures in Laguerre-Gaussian optical tweezers. Soft Matter, 2012, vol. 8, iss. 6, 1865-1870. ŽUMER, S., PORENTA, T., RAVNIK, M. Complex field-induced nematic defect structures in Laguerre-Gaussian optical tweezers. V: KHOO, Iam-Choon (ur.). Liquid Crystals XVI, (Proceedings of SPIE, the international society for optical engineering, vol. 8475). SPIE, 2012, 7 pp.


COLLOIDAL AND CONFINED BLUE PHASES Motivation

SIMULATIONS & MODELING Miha Ravnik Coworkers: Slobodan Žumer, Julia M. Yeomans, Gareth P. Alexander FUKUDA, J., ŽUMER, S. Novel defect structures in a strongly confined liquid-crystalline blue phase. Phys. Rev. Lett., 2010, vol. 104, 017801-1017801-4. RAVNIK, M., ALEXANDER, G. P., YEOMANS, J. M., ŽUMER, S. Mesoscopic modelling of colloids in chiral nematics. Faraday discuss., 2010, vol. 144, 159-169. FUKUDA, J., ŽUMER, S. Cholesteric blue phases : effect of strong confinement. Liq. cryst., 2010, vol. 37, no. 6-7, 875-882. ŽUMER, S., RAVNIK, M., PORENTA, T., ALEXANDER, G. P., YEOMANS, J. M. Blue phases as templates for 3D colloidal photonic crystals: [invited talk at SPIE Optics and Photonics Conference on Connecting Minds for Global Solutions, San Diego, 1 - 5 August 2010]. V: KHOO, Iam-Choon (ur.). Liquid crystals XIV : August, 2010, San Diego, California, US, (Proceedings of SPIE, v. 7775). SPIE, 2010, 7 pp. FUKUDA, J., ŽUMER, S. Ring defects in a strong confined chiral liquid crystal. Phys. Rev. Lett., 2011, vol. 106, 097801-1-097801-4.

The networks are periodic with a typical unit length of the cubic unit cell of few phases. The networks are periodic with a 100nm. Optically, blue phases are macroscopically isotropic, optically active, and give field-induced electrostriction.

Blue phases (BPs) are liquid crystalline materials which gained a major momentum in last few years because of their unique physical properties; i.e. being fluids with a crystalline unit cell. This combined fluidity and microscopic crystallinity indicate multiple remarkable phenomena, including lasing, large optical Kerr effect, flexoelectricity effects, and capabilities for polymer-doping and synthesis of regular polymer networks.

3D Blue phase colloidal crystals Ravnik and Žumer, together with partners from the University of Oxford, demonstrate that colloidal particles can self-assemble into stable, 3D, periodic structures in blue phase LCs (see Fig. 4.28), by using advanced computer modeling. The assembly is based on blue phases providing a 3D template of trapping sites for colloidal particles, which stems from the orientational order of the LC molecules. Specifically, face-centered cubic colloidal crystals form in type-I blue phases, whereas body-centered crystals form in type-II blue phases. For typical particle diameters (approximately 100 nm) the effective binding energy can reach up to a few 100 kT (kT is thermal energy), implying robustness against mechanical stress and temperature fluctuations. Moreover, the colloidal particles substantially increase the thermal stability range of the blue phases, for a factor of two and more. The LCsupported colloidal structure is one or two orders of magnitude stronger bound than, e.g., water-based colloidal crystals.

Here, we show that blue phases can self-assemble superstructures of microscopic and nanoscopic functionality, based on organization of nanoparticles and ultra-spatialconfinement. The superstructures indicate novel applications in advanced optics and photonics. Blue phases Blue phases are locally isotropic fluids in which the chiral molecules (or nonchiral molecules with chiral dopants) organize into complex threedimensional structures, characterized by the molecular orientational order. Up to three blue phase structures emerge, denoted as blue phase I, II and III with increasing temperature. The structures form as double-twisted cylinders of the average molecular orientational order separated by a network of defect lines where the orientational order breaks. Effectively, it is the network of the defect lines, which characterizes the blue phases.

Ultra-confined blue phases & Skyrmions

FUKUDA, J., ŽUMER, S. Quasi-twodimensional Skyrmion lattices in a chiral nematic liquid crystal. Nature Comms., 2011, vol. 2, art. no. 246, 5 pp. RAVNIK, M., ALEXANDER, G. P., YEOMANS, J. M., ŽUMER, S. Threedimensional colloidal crystals in liquid crystalline blue phases. Proc. Natl. Acad. Sci. U. S. A., 2011, vol. 108, 5188-5192. RAVNIK, M., FUKUDA, J., YEOMANS, J. M., ŽUMER, S. Confining blue phase colloids to thin layers. Soft Matter, 2011, vol. 7, iss. 21, 10144-10150. FUKUDA, J., ŽUMER, S. Structural forces in liquid crystalline blue phases. Phys. Rev., E Stat. nonlinear soft matter phys., 2011, vol. 84, iss. 4, 04071-1-04071-4. ŽUMER, S., RAVNIK, M., FUKUDA, J. Confined blue phases: trapping of colloidal particles in disclination superstructures. V: KHOO, Iam-Choon (ur.). Liquid crystals XV : 21-22 August 2011, San Diego, California, United States, (Proceedings of SPIE, the International Society for Optical Engineering, vol. 8114). SPIE, 2011, 7 pp. 11. ŽUMER Slobodan, FUKUDA Junichi, RAVNIK Miha. Confined colloidal blue phases with potential for photonics. Mol. Cryst. Liq. Cryst. 561,

Figure 4.28: Self assembly of 3D colloidal crystals in blue phase I and blue phase II, forming face centred cubic (FCC) and body centred cubic (BCC) particle super-structure

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Methods For the purpose of this research, we have developed a custom written numerical program package (in C, multithreading, cluster computations), capable of simulating general blue phases, colloids, and various effects of confinement and external fields. The method is based on the minimization of the total free energy of a chiral nematic material. Indeed, the approach has proven to be a powerful theoretical tool, able to qualitatively and quantitatively describe the developed materials. In parallel to the free energy minimization, the group also uses molecular Monte Carlo approaches that can address the role of molecular interactions, e.g., in the assembly of colloidal nano-particles.

Figure 4.29: Confined quasi-2D blue phase with double helix defect structure

Fukuda and Zumer demonstrate multiple new exotic micro-structures in blue phases confined to thin cells, not found in any bulk blue phase or any other liquid crystalline systems. The stability of these structures depends on temperature, cell thickness, and anchoring conditions at the confining surfaces. The following structures are found: double-helix structure (Fig. 4.29), arrays of undulating disclination lines, fragmented inchworm-like lines, hexagonal lattice of Skyrmion excitations (Fig 4.30), and regular array of ring disclinations. These complex structures of confined blue phases are a clear manifestation that liquid crystals can perform differently and more when subjected to strong spatial confinement.

Summary & Deliverables The scientific achievements include: • Self-assembly process for production of 3D, quasi-2D, and 2D colloidal crystals. • Revealed nanoscopic and microscopic trapping sites, for trapping of colloidal particles, polymers, and macro-molecules. • Novel optically active structures with potential for optics and photonics, including photonic crystals.

Technologically, they are particularly interesting as a route towards spontaneously formed anistropic nanopatterns and micro-modulations. The properties of these structures can be further advanced, if doping with colloidal particles, forming 2D and quasi-2D colloidal crystal, presented in Figure 4.

• Discovery of fundamental particle excitations in material fields –the Skyrmions and baby-Skyrmions- with applications for memory devices, nanopatterning, and surface-grating design.

Centre-of-Excellence VISITING SCIENTIST Jun-ichi Fukuda 1999 PhD in physics at Kyoto University , “Phase separation of liquid crystalline polymers: Statics and dynamics” 1999 Post doctoral fellow, Japan Society for the Promotion of Science (JSPS) (Nagoya, Japan) 1999-2004 Post doctoral fellow, Yokoyama Nano-structured Liquid Crystal Project, Japan Science and Technology Agency (JST) (Tsukuba, Japan) 2004-09 Researcher, National Institute of Advanced Industrial Science and Technology (AIST) (Tsukuba, Japan) 2009-present Senior Researcher, National Institute of Advanced Industrial Science and Technology (AIST) (Tsukuba, Japan) 2009 Visiting Scientist, University of Ljubljana, and Jožef Stefan Institute, Slovenia 2012-13 Visiting Scientist, University of Ljubljana, and Center of Excellence NAMASTE, Slovenia Selected recent publications: OHZONO, T., FUKUDA, J., Zigzag line defects and manipulation of colloids in a nematic liquid crystal in microwrinkle grooves. Nat. Comms, 2012, vol. 3, art. no. 701, 4 pp. FUKUDA, J., ŽUMER, S. Quasi-twodimensional Skyrmion lattices in a chiral nematic liquid crystal. Nature Comms., 2011, vol. 2, art. no. 246, 5 pp. FUKUDA, J., YONEYA, M., YOKOYAMA, H. Surface-groove-induced azimuthal anchoring of a nematic liquid crystal: Berreman's model reexamined. Phys. Rev. Lett., 2007, vol. 98, 187803-1187803-4.

Figure 4.30: Quasi-2D Skyrmion lattices with hexagonal symmetry in ultra-confined blue phase liquid crystal. Defects (in red) are visualized as areas with reduced degree of order. Molecular orientational ordering is shown in grey

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Figure 4.30: Confined 2D and quasi-2D blue phase colloidal crystals


ACTUATION OF LIQUID CRYSTAL ELASTOMERS Introduction

EXPERIMENTS Boštjan Zalar Ph.D. in Physics at University of Ljubljana, Slovenia, with thesis: Investigations of static and dynamic properties of pseudo-spin glasses with nuclear magnetic and nuclear quadrupole resonance Science Councillor at Department of Solid State Physics (F5), J. Stefan Institute, Ljubljana Full Professor of Physics at Jožef Stefan International Postgraduate School, Slovenia Principal Investigator at CoE NAMASTE and CE EN-FIST Selected publications: ZALAR, B., ŽUMER, S., FINOTELLO, D. Deuteron NMR study of monolayerthick films of nematogenic molecules. Phys. Rev. Lett., 2000, 84, 4866-4869. LEBAR, A., KUTNJAK, Z., ŽUMER, S., FINKELMANN, H., SÁNCHEZ-FERRER, A., ZALAR, B. Evidence of supercritical behavior in liquid single crystal elastomers. Phys. Rev. Lett., 2005, vol. 94, 197801-1-197801-4. CORDOYIANNIS, G., LEBAR, A., ZALAR, B., ŽUMER, S., FINKELMANN, H., KUTNJAK, Z. Criticality controlled by cross-linking density in liquid singlecrystal elastomers. Phys. Rev. Lett., 2007, 99, 197801-1-197801-4. Coworkers: Blaž Zupančič, Valentina Domenici , Martin Čopič, Maja Remškar, Claudio Zannoni

Liquid crystal elastomers (LCEs) are soft functional materials consisting of weakly crosslinked polymer networks with embedded liquid crystalline (mesogenic) molecules. LCEs are therefore characterized by a pronounced coupling between macroscopic strain and orientational mesogenic order. Since the latter can be controlled by external stimuli such as temperature variation, electric field, or ultraviolet light, LCE have great potential for application as sensors and actuators.

Figure 4.31: A typical DNMR spectrum of an azomesogenic material

Experiments Detailed knowledge on the local orientational organization of LCE network building blocks is of crucial importance in understanding and tailoring their macroscopic actuation response. Deuterium magnetic resonance (DNMR) spectroscopy has recently been demonstrated as a powerful tool for studying orientational order of molecules and/or their segments in LCE networks [1]. In natural abundance, the sensitivity of DNMR is too low, so that specimens must either be deuteron-labeled or doped with deuterated probes. The second approach is relatively straightforward, however, chemical inequivalence between the mesogens, linked to the polymer backbone, and the probes, can result in phase separation, commonly observed in binary liquids, even at relatively low concentrations of deuterated probes. Similar behavior is encountered in photoisomerizable networks, where the azomesogen subcomponent may exhibit segregation tendencies, a phenomenon not yet well understood in conventional LCEs. We addressed this problem by analyzing DNMR spectra and determined the phase diagram of a model system, specifically of 7AB low molar mass UV illuminationmanipulated azonematogen [4] (Fig. 4.31).

Figure 4.32: Optical image of the LCE/MoO3-x nanowire composite, showing the alignment of nanowires along the actuation,nematic e.g. with electric or magnetic director n at the surface.

fields. However, the development of such materials is still in its infancy. We have addressed this issue by preparing composites of LCEs and MoO3-x nanowires, embedded into the polymer network at sample surface (see Fig 4.32). Their structure, morphology, and thermal behavior have been investigated by scanning/transmission electron microscopy (SEM/TEM) and optical imaging, as well as by thermomechanical measurements [3]. Theoretical phenomenological and molecular modeling has revealed that real LCEs networks may exhibit soft elastic response when manipulated by external magnetic or electric fields [7]. Moreover, DNMR spectroscopy has demonstrated that the multiple-component character of these networks and the resulting local phase separation tendencies need to be taken into account when designing the composition of the network. The particular case of combining molybdenum-based nanowires with LCEs has demonstrated that composites preserving the pristine mechanical and optical properties of the host matrix can indeed be prepared.

Thermomechanical actuation of LCEs is known to suffer from relatively slow actuation timescales, making it inappropriate for applications in actuator technologies and micro and nano-electromechanical (MEMS/NEMS) devices. Composites of LCEs and inorganic nanoparticles could possibly overcome this disadvantage by providing a nonthermal approach to

Molecular Simulations In order to assist the preparation of new LCE materials, we have also carried out large-scale molecular simulations of

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SIMULATIONS Gregor Skačej

Figure 4.33: Electro-mechanical effect in a swollen main-chain LCE: snapshots of simulated molecular configurations. Electric field strength increases from left to right, resulting in strong deformations

2002: Ph.D. in Physics at University of Ljubljana, Slovenia, with thesis: Modeling of strongly confined liquidcrystalline systems From 1996: Teaching and research Assistant at Faculty of Mathematics and Physics, University of Ljubljana 2003-2005: Postdoctoral research fellow at University of Bologna, Italy From 2010: Researcher at CoE NAMASTE Selected publications: SKAČEJ, G., ZANNONI, C. Controlling surface defect valence in colloids. Phys. Rev. Lett., 2008, vol. 100, 197802-1197802-4.

Figure 4.34: Electromechanical effect in LCE as seen in simulated scattered X-ray patterns (left), calculated on our CoE NAMASTE 360-core computing cluster Avalon (right)..

swollen main-chain LCEs, treating systems with up to 216000 elongated mesogenic molecules, crosslinked into a polymer network (Fig. 4.33).

and scattered X-ray patterns. The calorimetry data is particularly appealing for the study of phase transitions, while DNMR and X-ray scattering can be used to study orientational and positional order of mesogenic molecules.

Our simulated experiments include temperature scans, stress-strain runs, and the application of an external electric field (Fig. 4.34). Performing constant-stress Monte Carlo simulations in our systems we have so far observed isotropic (disordered), nematic (orientationally ordered), and smectic (orientationally and positionally ordered) phases, as well as a stressinduced isotropic-to-nematic transition [5]. Moreover, a transversal electric field has been seen to induce a collective rotation of aligned mesogenic molecules, resulting in orientational stripe domains [6]. This rotation is accompanied by a rather soft significant elastic deformation, which seems to be particularly promising for application.

Conclusions The performed experimental research activities show that synthesis of LCEs with tailored properties and preparation of LCE-based composites with nanoparticles may lead to development of a new generation of soft materials, with reversible mechanical deformation of the magnitude by far exceeding the one found in solid materials and triggerable by nonthermal means. On the other hand, molecular simulation has so far addressed only the very basic phenomena in LCE, finding sufficient qualitative agreement with real experiment, and is now ready to proceed towards more complex composite materials.

The rather extensive simulation output has also been used to predict typical experimental observables, such as LCE sample dimensions for stress-strain experiments, specific heat for calorimetric studies, DNMR spectra,

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SKAČEJ, G., ZANNONI, C. Main-chain swollen liquid crystal elastomers: a molecular simulation study. Soft Matter, 2011, vol. 7, 9983-9991. SKAČEJ, G., ZANNONI, C. Molecular simulations elucidate electric field actuation in swollen liquid crystal elastomers. Proc. Natl. Acad. Sci. U. S. A., 2012, vol. 109, no. 26, 10193-10198. CORDOYIANNIS G., LEBAR A., ROŽIČ B., ZALAR B., KUTNJAK Z. Controlling the critical behavior of para-N to N transition in main-chain liqiud-singlecrystal. Macromolecules, 2009, vol. 42, 2069-2073. DOMENICI, V., ZUPANČIČ, B., LAGUTA, V. V., BELOUS, A., V'YUNOV, O., REMŠKAR, M., ZALAR, B. PbTiO[sub]3 nanoparticles embedded in a liquid crystalline elastomer matrix: structural and ordering properties. The journal of physical chemistry. C, Nanomaterials and interfaces, 2010, vol. 114, no. 24, 10782-10789. DOMENICI, V., CONRADI, M., REMŠKAR, M., VIRŠEK, M., ZUPANČIČ, B., MRZEL, A., CHAMBERS, M., ZALAR, B. New composite films based on MoO[sub](3-x) nanowires aligned in a liquid single crystal elastomer matrix. J. Mater. Sci., 2011, vol. 46, no. 10, 36393645. ZUPANČIČ, B., DIEZ-BERART, S., FINOTELLO, D., LAVRENTOVICH, O. D., ZALAR, B. Photoisomerizationcontrolled phase segregation in a submicron confined azonematic liquid crystal. Phys. Rev. Lett., 2012, vol. 108, no. 25, 257801-1-257801-5. SKAČEJ, G., ZANNONI, C. Molecular simulations elucidate electric field actuation in swollen liquid crystal elastomers. Proc. Natl. Acad. Sci. U. S. A., 2012, vol. 109, no. 26, 10193-10198.


MOLYBDENUM AND TUNGSTEN BASED NANOMATERIALS 0,2

Maja Remškar 1985: graduate in physics (University of Ljubljana, Slovenia) From 1987: employed at Jozef Stefan Institute 1994: PhD in physics in the field of Condensed Matter Physics 1995: postdoc at EPFL | ÉcolePolytechniqueFédérale de Lausanne, Lausanne, Switzerland 2003: habilitation at University of Ljubljana From 2004: member of Governmental Commission for Women in Science From 2010: employed at CoE NAMASTE, CoE PoliMaT and CE Nanocenter. From 2010: Principal Investigator at CE NAMASTE and CE Nanocenter

PAO

0,18

Motivation

PAO+NT

Coefficient of friction

0,16

Molybdenum disulfide (MoS2) is a known lubricant, which has been applied extensively for decades in form of platelets. It is used also for removal of sulfur from the petroleum and as photocatalysis in hydrogen generation. In 1993 the MoS2 nanotubes were discovered in Israel. At Jozef Stefan Institute they were firstly synthesized by innovative technique in 1995. In 2007 we optimized the synthesis, discovered new morphologies of MoS 2, like “mama”-tubes, coaxial nanotubes, nanobuds, and applied for patent protection. Besides MoS2 compound we developed also a procedure for synthesis of MoO3 nanomaterials, which are usable as sensors, as host for lithium intercalation, and as antibacterial contact material.

0,14 0,12 0,1 0,08 0,06 0,04 0,02 0 25

50

75

100

Sliding distance [m]

Figure 4.35: Coefficient of friction of base oil (PAO) and PAO oil mixed with 5 wt% MoS2 (from Ref. 1)

Figure 4.36: Optical micrographs of wear scars on the steel discs after 100 m of sliding for a pin-on-disc contact lubricated with (a) pure base PAO oil and (b) PAO oil with 5 wt% MoS2 nanotube (from Ref. 1).

We established a spin-off company Nanotul for commercialization of the nanomaterials developed in the research process. The company Nanotul is a member of technological Park Ljubljana and co-founder of the Center of Excellence NAMASTE. Goals of our research are:

Selected publications: REMŠKAR, M., MRZEL, A., ŠKRABA, Z., JESIH, A., ČEH, M., DEMŠAR, J., SADELMANN, P., LÉVY, F., MIHAILOVIĆ, D. Self-assembly of subnanometerdiameter single-wall MoS[sub]2 nanotubes. Science, 2001, vol. 292, 479-481. REMŠKAR, Maja. Inorganic nanotubes. Adv. Mater., 2004, vol. 16, 1497-1504.

Coworkers: Ivan Iskra, Janez Jelenc, Maja Češarek, Marko Đjorić,Bojana Višić, Ana Dergan

 to develop nanomaterials industrial application

for

 to find size dependent phenomena  to study surface with atomic and nanoscale resolution

Figure 4.37: Coefficient of friction at stainless steel (AISI 316) contact using sunflower (SF) oil and the SF oil with 2 wt. % of MoS2 nanotubes (from Ref. 2).

Equipment CoE NAMASTE: Near field optical microscope (Witec) equipped with confocal raman spectroscopy and atomic force microscopy; spin coater, thin film applicator;

friction for more than 2-times and wear as much as 5–9-times compared to the pure PAO oil. [Ref. 1] The MoS2 nanotubes strongly reduce friction between stainless steel (AISI 316) counterparts measured in flat-onflat configuration also vegetable oils used as lubricants [Ref. 2]. The 2 wt. % of the MoS2 nanotubes in rapeseed oil decrease friction for 25 % in comparison with the pure oil, while in sunflower oil the MoS2 nanotubes reduce friction for 40 %.

JSI: ultra high vacuum atomic force microscope/scanning tunneling microscope; transmission electron microscope; x-ray diffractometer. Results We have developed process for synthesis of gram-quantities of pure MoS2 nanotubes for application in semi industrial tribology testing. The friction tests in boundary lubrication regime have been performed in collaboration with Faculty of Mechanical Engineering, University in Ljubljana and CE Nanocenter. It was found that 5 wt. % MoS2 nanotubes added to polyalphaolephin (PAO) synthetic oil, which is typically used in automotive industry, significantly decreases the

Friction between a single MoS2 nanotube and silicon tip tested by atomic force microscope operating in ultra-high vacuum at room temperature revealed that the coefficients of friction are much below the relevant values obtained for flat MoS2 single crystal or graphite [Ref 3]. We revealed a nontrivial dependency of coefficient of friction on interaction strength

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between the nanotube and underlying substrate that is explained with dissipation of energy and shear deformation. The MoS2 nanotubes with high interaction strength revealed up to four times larger coefficient of friction (0.08 ± 0.02) than weakly supported tubes (0.023 ± 0.005). In addition, we evidenced that a rolling mechanism of MoS2 fullerene-like nano-onions is indeed possible at low loads in accordance with recent predictions.

KALIN, M., KOGOVŠEK, J., REMŠKAR, M. Mechanisms and improvements in the friction and wear behavior using MoS2 nanotubes as potential oil additives. Wear., 2012, vol. 280/281, iss. 4, 36-45.

We have chemically exfoliated MoS2 nanotubes and produced single-layer flakes that are stable for months, with a low degree of restacking [Ref. 4]. The optical absorbance by the flakes shows a strong quantum confinement effects. The relatively simple process of getting one-layer-thick MoS2 can be used to provide new types of materials with possible applications in polymer composites, photovoltaics, and nanoelectronics.

Figure 4.38: Atomic force microscopy images of three MoS2 nanotubes with low interaction strength between the nanotubes and underlying HOPG substrate (a-c) and of one with a strong interaction (d) with marked areas of the friction measurements; scale bars: 500 nm (from Ref. 3).

We found a new way of synthesis of Molybdenum blue-type material from ethanol dispersion of MoS2 thin flakes, which have been obtained by exfoliation of MoS2 nanotubes [Ref. 5]. The smallest observed Mo blue molecule is 1.6 nm in diameter, while their self assemblies range from 10 nm to a few tens of µm. Our Mo-blue molecules represent the smallest reported Mo blue in general.

JELENC, J., KRAJNIK, P., REMŠKAR, M. Rastlinska olja z dodanimi nanocevkami MoS [spodaj]2 kot učinkovita zelena maziva. V: VIŽINTIN, Jože (ur.), SEDLAČEK, Marko (ur.). Posvetovanje o tribologiji, hladilno mazalnih sredstvih in tehnični diagnostiki = Conference on Tribology, Metal Working Fluids and Technical Diagnostics [tudi] SLOTRIB 2012, Ljubljana, Slovenija, 15. november 2012. Zbornik predavanj Posvetovanja o tribologiji, hladilno mazalnih sredstvih in tehnični diagnostiki. Ljubljana: Slovensko društvo za tribologijo: = Slovenian Society for Tribology, 2012, 47-52. JELENC, J., REMŠKAR, M. Friction on a single MoS2 nanotube. Nanoscale Res. Lett., 2012, vol. 7, 208-1-208-17. VIŠIĆ, B., DOMINKO, R., KLANJŠEK GUNDE, M., HAUPTMAN, N., ŠKAPIN, S. D., REMŠKAR, M. Optical properties of exfoliated MoS[sub]2 coaxial nanotubes - analogues of graphene. Nanoscale Res. Lett., 2011, vol. 6, no. 1, 593-1-593-6. VIŠIĆ, B., KLANJŠEK GUNDE, M., KOVAČ, J., ISKRA, I., REMŠKAR, M. MoS2 nanotube exfoliation as new synthesis pathway to Molybdenum blue. Mater. Res. Bull. (accepted)

Figure 4.39: Monolayers of MoS2

We have built the first field-effect transistor (FET) based on thin WS2 flakes in collaboration with Notre Dame University, Indiana [Ref. 6]. We found 5 ambipolar behavior and a high (10 ) on/off current ratio at room temperature with current saturation. The FETs also show clear photo response to visible light. The promising electronic and optical characteristics of the devices make them attractive for future electronic and optical devices.

Figure 4.40: Collapse of a giant self-assembly of Moblue nanospheres

Conclusions MoS2 nanotubes are very promising additive to oils and greases for friction reduction Exfoliated MoS2 nanotubes lead to MoS2 monolayers, which show a strong quantum confinement effect, a low degree of restacking and represent inorganic graphene analogy. Thin WS2 flakes have been used for fabrication of field effect transistors. Figure 4.41: Drain current ID vs. back gate voltage VGS at various drain voltages VDS, showing 105 on/off current ratio

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HWANG, W. S., REMŠKAR, M. Transistors with chemically synthesized layered semiconductor WS[sub]2 exhibiting 10[sup]5 room temperature modulation and ambipolar behavior. Appl. Phys. Lett., 2012, vol. 101, no. 1, 013107-1-013107-4.


LIQUID CRYSTAL LIGHT SHUTTERS FOR PERSONAL PROTECTION Introduction RESEARCH & DEVELOPMENT Janez Pirš 1975: Ph.D. in Physics at University of Ljubljana, Slovenia Current position: Scientific counselor, Member of Engineering Accademy of Slovenia, Global Research Consultant – Kimberly Clark Profesional, Principal Investigator at CoE NAMASTE and CoE Nanocenter Selected publications: A. VREČKO, J. PIRŠ, M. BAŽEC and D. PONIKVAR: “Wide-view STN liquid crystal light shutter”, Appl. Optics, 47, no.12, (2008). ISO TC94/SC6/WG2/Task group ADF: “Additional test methods for automatic welding filters”, Internal ISO publication until the new standard: Environmental Eye and Face Protection becomes mandatory. EU and USA patents (granted): J. PIRŠ, A. VREČKO, S. PIRŠ, D. PONIKVAR: “High contrast, wideviewing angle LCD light filter” EP 1883854; US 8,026,998 J.PIRŠ, M. BAŽEC, S. PIRŠ, B. MARIN, B. URANKAR, D. PONIKVAR “High contrast, wide-viewing angle LCD light filter” US 8,026,998 Continuation in part US patent application US 2012/0002121 J. PIRŠ, M. BAŽEC, S. PIRŠ, B. MARIN, A. VREČKO: “High Contrast, Wide Viewing Angle LCD Light-Switching Element” EP 1625445, US 7,420,631 J. PIRŠ, B. MARIN, D. PONIKVAR, S. PIRŠ: “Driving scheme and electronic circuitry for the LCD electrooptical switching elements” EP 1131669; US 7,061,462 Coworkers: Bojan Marin, Silvija Pirš, Dušan Ponikvar, Bernarda Urankar, Dušica Pahor

Figure 4.42: LCD welding light filter – block diagram

light switching filter significantly improves the working conditions for the welder. It allows the welder full protection as well as normal vision before, during and after the welding without continuous “lifting and lowering” the protective helmet. So the welder has both hands free and can perform his work safer, much more efficiently and especially much better .

The technology for Liquid Crystal applications has made an important breakthrough in the past ten years. The new, high resolution LCD display panels for computer monitors and TV display panels have made Liquid Crystals the key technology for display applications. A number of non-display applications have immerged so far as well.

Technical performance of Balder’s automatic protective filters

A typical example of this kind are LCD optical light shutters that allow for electrical control of the transmitted light based on the electrical and optical anisotropy of these materials. The most widespread application is automatic LCD light filter for personal protection in welding. With the difference from e.g. regular high definition TV screen having  2 million (1920 x 1080) display pixels (local light shutters) allowing for displaying images, the LCD protective light filters have only one such switching element controlled by two electrodes. Compared to a standard display pixel (like TV screen) the LCD light switching protective filter must:  reduce the incident light by 1000 times more than a display pixel of a TV screen,  provide passive protection against harmful IR and UV light generated during the welding process,  selectively detect the welding light and modulate the transmitted light accordingly. Such extreme performance can be achieved only by:  two LCD light shutters in a tandem,  much higher driving electric field,  additional passive optical band-pass filter transmitting incident light only in the visible spectral range. As evident from the figure, such a protective automatic optical filter is in fact a multilayer laminate (Fig. 4.42) comprising at least two LCD cells, four polarizing filters and protective passive optical filter that reflects harmful infrared and ultraviolet light generated during the welding process. In order to improve the overall filter performance additional layers can be added (e.g. optical compensation layers).

gure 4.43: Light transmission vs. voltage characteristics of Balder’s LCD light filters

In the course of a number of its international research projects (NATO SfP, EU-FW5, Hierarchy) as well as projects financed by Slovenian research agencies (ARRS and TIA), Jožef Stefan Institute and its spin-off company Balder have developed an improved LCD light shutter concept for personal protection applications. A number of original technical solutions developed before and most of them during Balder’s participation in the CoE NAMASTE, allowed Balder to develop its new product line “ADC-plus” protective welding filters which are the only automatic welding filters in the world (competitors: e.g. Honeywell, 3M,…) that can be labeled with prestigious marking DIN Plus 1/1/1/1 or CE 1/1/1/1 (-maximal optical quality) according to EN 379. The excellent performance of Balder’s new-gen “ADC-plus” welding filters is achieved by the innovative technical solution based on the use of highly twisted ( 225°) LC structures rather than the standard 90°-twisted TN LCD light shutters ( 5 international patents and a patent application 2012; granted in EU and USA). The highly twisted nematic LC structure, never used for LCD light shutters before, allows for several important performance advantages: 1. Better light attenuation definition because of the low slope “transmission vs. voltage” characteristics in the optically closed state (Fig. 4.43), 2. Significantly better homogeneity of the angular dependence of the light attenuation in the optically closed (protective) state due to significantly higher angular symmetry of the 225° LC molecular twist as compared with the standard 90°-twisted nematic LCD light shutters,

The protective welding helmet with a built-in automatic LCD

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3. Significantly better overall homeotropic alignment of the LC molecules in the optically closed (protective) state of the LCD light shutter (Fig. 4.44). The latter allows for the additional angular compensation of the light attenuation by means of a simple, cheap negativebirefringent compensation foil (see Fig. 4.42). The above advantages result in a significantly improved overall optical performance of Balder’s new-gen ADCPlus line of welding filters as seen by a comparison of the computer modeling of the angular dependence of the standard TN LCD light shutter as used by others and Balder’s ADC-plus solution the slant light incidence angles presented in polar coordinates (Fig. 4.45).

electro-welding. The standard Balder’s welding helmet was also modified to fit with the medical equipment and the measuring light impulses generated by it. Since the experiments had to be carried on under clinical conditions, the welding apparatus was replaced by the Standard ISO welding light source, developed and manufactured by Balder. The obtained results clearly show that Balder’s ADC-Plus welding filter perfectly protects the human eye against the intense light flashes as occurring during the welding – signal of the eye nerve remains unaffected by the light pulse from the Standard ISO welding light source. Perspectives

RESEARCH & DEVELOPMENT Bojan Marin 1984: Graduated in Physics at University of Ljubljana 1975: MS in Electronics at University of Ljubljana, Slovenia Current position: Chief Executive Officer (Balder), Kimberly Clark Profesional

Balder’s technological breakthrough in the niche field of LCD protective welding filters did not pass unnoticed by the World Market. Kimberly Clark (KC), one of the key global Corporations dealing with Personal Safety (25 billion $ turnover/year) soon realized the opportunity offered by the exceptional performance of Balder’s filters. In June 2012, Balder became part of the KC’s division “Kimberly Clark Professional” with Slovenian personnel and management but the KC’s world-wide marketing network, business Computer modeling of the LC relations and potential for Figure 4.44:molecular orientation - comparison investment and unlimited between standard TN LCD vs. Balder’s professional growth. LCD light shutters

Safety regulations/standards On the grounds of the exceptional performance of Balder’s products (Fig. 4.46) the ISO invited Balder and IJS to actively participate in its expert groups ISO/TC94/SC6/WG2 and WG4 to prepare new ISO standard: “Occupational Eye and Face Protection”. Within the work in these two groups, Balder:  Proposed a new test method for measuring angular dependence of the active LCD welding light filters,  Proposed and developed together with Jožef Stefan Institute a new “test method for measuring the light sensitivity of the active LCD welding light filters”, which includes also the design and manufacturing of the new ISO standard light source simulating TIG welding,  Substantially contributed to the final draft of the new ISO standard. Medical evaluation Finally, in order to stay on a cutting edge of the automatic LCD light filter technology for personal protection applications, Balder is constantly monitoring and evaluating the overall performance of its products. With the support of Slovenian research agency ARRS, Balder has organized a comprehensive medical evaluation of eye hazards and eye protection (active LCD light filters) of human eyes against intense light flashes, as present in TIG and other electro-welding processes. The studies were performed at the Dept. for Ophthalmology at the University Clinical Center Maribor, Slovenia. The standard medical equipment (e.g. Tomey EP 1000) designed for routine medical analyses of the electric signals of the eye nerve, were modified to allow synchronization of the measurement with the intense light pulses as typically present with

Figure 4.45: Polar coordinate plot of the light attenuation - comparison between standard TN LCD vs. Balder’s LCD light shutters

Figure 4.46: New line of Balder’s ADC-Plus welding filter products

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Scaffolds Bioceramics Antimicrobials Microspectroscopies Nanoparticles in cells Nanoparticles in tissues Cell-material interactions Nanoparticles in the environment

Bioactivity, biocompatibility

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RRP5

Advanced bioactive, biocompatible and bioinert materials Motivation

Janez Ĺ trancar 1996: Graduate in physics (Faculty of Mathematics and Physics, University of Ljubljana, Slovenia): with thesis: Study of spin-labeled transport of lipophilic molecules through biological membranes via electron paramagnetic resonance From 1997: Employed at Jozef Stefan Institute 2000: PhD in biophysics (University of Ljubljana) with thesis: EPR spectroscopy of cell membrane surface 2002-2003: Postdoc at Institute of Biophysics and X-ray Structure Research, Graz, Austria 2005. Habilitation in nanobiophysics at Jozef Stefan International Postgraduate School From 2006: Head of the Laboratory of Biophysics and Research program Experimental Biophysics of Complex Systems From 2008: Lecturer at University of Maribor, Faculty of Natural Scuences and Mathematics (Physical Measurements) From 2009: Lecturer at University of Ljubljana, Faculty of Pharmacy (Molecular biophysics) From 2010: Head of the RRP5 project at CoE NAMASTE

surfaces in the food-processing industry by preventing contamination with nasty bacteria like Listeria monocitogenes and others. Numerous activities are focused to enhance the deposition of nanomaterials onto various surfaces, to improve the photoexcitation and antimicrobial effect, opening up new applications in civil engineering, especially related to heat exchange.

Recent developments in materials and functionalized surfaces open up new opportunities in the fields of medicine and medical materials, directly or indirectly affecting our health and the environment. New concepts and strategies have been setup to increase our quality of life. But how sure are we that these materials are safe enough they make close contacts with the human body sooner or later. There is no doubt that these materials have to be tested for interactions with our body tissues and cells, plants and animals extensively. Let’s allow these materials to work for us, not against us! In the world of novel materials and developing technologies, preventing hidden threats to our health and environment should be our main priority. Antimicrobial surfaces nanomaterials

based

on

Antimicrobial surfaces can potentially replace environmentally hazardous (bio)-chemical substances released into the environment. A completely different mode of action provides a new concept of antimicrobial protection, also reducing the probability of resistance development. Based on surface functionalization with nanomaterials these surfaces are prone to problems in deposition and immobilization. Consequently, nanomaterials can also be released from surface into the environment, potentially accompanying some unidentified threats.

Figure 5.1: Nanomaterials based on titan-oxide used for antimicrobial protection

Other activities are focused on setting up new methodologies to identify and trace nanomaterials in the cell, tissue organisms and environment. Some new techniques, like fluorescence microspectroscopy, have been developed in addition to many

Numerous research projects around the world proved that the research community is concerned about launching nanomaterial-functionalized systems onto the market. Many of these projects, therefore, aim at providing a guarantee for new materials' safety and/or at standardizing testing protocols, addressing materials' safety. Within the CoE NAMASTE we joined the research profiles of material sciences, natural sciences, biotechnology, medicine and veterinary sciences to encourage the development of new, human-healthy, antimicrobial surfaces to maintain clean

Figure 5.2: Spectrally identified nanoparticles within the cell by FMS

experimental hybrid methods installed in our laboratories or brought into research practice.

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Finally, some of our activities are also focused on establishing the monitoring of nanoparticles in the local environment and to identify contamination sources. New methods were developed as well as the special nanoparticle detector.

Partners: Institut „JoĹžef Stefan“ http://www.ijs.si

Univerza v Ljubljani http://www.uni-lj.si

Figure 5.4: Fibroblasts on the gelatin-scaffold studies by FMS

we join the highly interdisciplinary R&D activities of experts from material sciences and engineering, life sciences and medicine to address many implantrelated issues.

Figure 5.3: Prototype of nanoparticle detector

Biocompatibility Recent demographic trends clearly show that life expectancy is increasing, but not matched by an improvement in the quality of life. The regenerative medicine markets thus encounter a strong expansion every year, having a critical impact on the healthcare systems all around the world. A shortage of qualified people is expected, with the experts teaching at the universities or being trapped in the too restricted local environment of different companies, without being exposed to cutting-edge research. Successful medical device implantation and tissue regeneration thus depends mainly on skilled scientists capable of integrating different fields of science and transferring the knowledge directly to the research-driven medical-markettargeting private sector.

Biopolymer scaffolds are used to explore scaffold-cell interactions by fluorescence microspectroscopy and optical tweezing to provide new insights into biocompatibility through stress experiments. Material-induced cell proliferation and differentiation are also addressed. On the other hand, ceramic implants are carefully studied as bioinert materials, being especially prone to degradation and enabling strong binding at the same time to address long-term safety and the biocompatibility of these new materials and technologies.

Univerza v Mariboru http://www.uni-mb.si

PANVITA AGROMERKUR d.o.o. http://www.panvita.eu

Nanotul d.o.o. http://www.nanotul.com

Implanted medical devices with preferred material properties often induce a broad spectrum of undesired responses of the surrounding tissue, inflammatory response being the most famous, but followed also with undesired/uncontrolled cell adhesion or proliferation, migration and the least understood: material-induced cell differentiation. Obviously, biocompatibility depends on the materialtissue/cell pair, and as such, calls for the more intensified and broader research of the implant-cell interactions that governs biological reactions. There are endless attempts in the research community to address material biocompatibility adequately, to rationally guide new implant developments. Within CoE NAMASTE

Figure 5.5: A nano-crystaline coating consisting of boehmite (AlOOH) lamellas used in dental implants

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NANOPARTICLES AND FOTOEXCITATION TO FIGHT AGAINST BACTERIA

From 1984: Employed at Veterinary faculty as young researcher 1993: PhD on veterinary sciences (University of Ljubljana) with thesis: The use of clinoptilolite in intensive broiler rearing 1994-1996: Postdoc at Institute of Grassland and Environmental Research, North Wyke, GB and University of Hohenheim, DE 2005: Habilitation, associated professor, Univerity of Ljubljana From 1997: Head of the Instutute for Environmental and Animal Hygiene with Ethology, Veterinary faculty, University of Ljubljana Most important work: 1. GOBEC, Ivan, OCEPEK, Matjaž, POGAČNIK, Milan, DOBEIC, Martin. Inactivation of Mycobacterium avium paratuberculosis in sheep manure. Slov. vet. res.. [English ed.], 2009, vol. 46, no. 3, 105-113. 2. DOBEIC, Martin, PINTARIČ, Štefan. Laying hen and pig livestock contribution to aerial pollutin of Slovenia. Acta vet. (Beogr.), 2011, vol. 61, no. 2/3, 283-293. 3. DOBEIC, Martin, PINTARIČ, Štefan, VLAHOVIĆ, Ksenija, DOVČ, Alenka. Feral pigeon (Columbia livia) population management in Ljubljana. Vet. arh, 2011, vol. 81, no. 2, 285-298.

thermal dehydration (1200˘C) and adhesion on the surface owing to Van der Waals forces. For that reason, the uses of biocidal nano coatings can represent an important step in reducing the incidence of bacteria, particularly pathogenic species. Surfaces coated with nano biocidal coatings provide a permanent antibacterial protection, which offers the significant reduction of chemical disinfectants and labor costs, which is an important contribution to public health and environmental protection.

Mode of action – photoexcitation and free oxygen radicals

Preventing processing

Biocidal coatings, such as titanate submicron materials, have been shown to be bioactive materials, e.g., they photocatalyze the process of generating short-lived free radicals in wet conditions under UV or even violet visual light irradiation. The mechanism of titanate nanotubes activity is based on the photoinduced generation of free oxygen radicals reacting with different organic molecules and interfering also with the physiological processes of the cell. Titanate nanomaterials doped with

contamination

in

food

These materials were chosen for experiments as anti-bacterial agents in food plants. One of the most unpleasant food plant contaminants is bacteria Listeria monocytogenes, the responsible for the human disease listeriosis. The risk of food-borne bacteria Listeria has brought to attention the different pathways of Listeria contamination, while Listeria is ubiquitous, psychotropic and resistant at a wide range of temperatures, with

400

intensity of light (a.u.)

1982: Graduate in Biotechnical faculty - Veterinary department (University of Ljubljana, Slovenia)

OH• raddical production (a.u.)

Martin Dobeic

Virtually any material can exist in submicron dimensions. When “macro” particles are dismantling to the nano dimensions they greatly increase their surface-to-volume ratio. Besides, they dramatically change their chemical, mechanical, optical and magnetic properties, and increase their chemical reactivity. Some materials are known as anti-bacterial agents – the mode of their action is less specific, probably destroying the outer layers of bacterial cells.

300

200 TiNTs low Na degussa sun through glass window ceiling fluorescent lamp

100

0 280

300

320

340

360

l nm

380

400

420

Figure 5.6: Photoinduced radical production of titan-oxide nanotubes with sun and fluorescent lamp spectrum

a low content of copper or zinc had the highest photocatalitical activity when exposed to UV light or the wavelength range below 400 nanometers, which indicates that the antimicrobial action is possible, even with photoexcitation under ordinary fluorescent lamps, which are widely used in internal lightning.

the ability for biofilm formation are resistant to disinfection using common methods of chemical disinfection. The Listeria resistance to ground sanitation refers to the study of the titanate biocidal materials in nano dimensions. This is an important step in reducing the incidence of bacteria, particularly pathogenic species such as Listeria monocytogenes in food plants. Our experiments in laboratory conditions showed that at least 35% of the tested

The basic principle of a titanate nanotubes suspension coating is

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1. DOBEIC, M., KENDA, E., MIĆUNOVIĆ, J., ZDOVC, I.. Airborne Listeria spp. in the red meat processing industry. Czech J. Food Sci., 2011, vol. 29, no. 4, 441-447.

Figure 5.7: The average number (log10) of grown colonies of L. innocua on the test PET slides exposed in evisceration and in cold room of poultry slaughterhouse

closely related nonpathogenic bacteria (L.innocua) were reduced on titanate nanotubes-coated glass and PET material under the conditions of UV photoexcitation (365 nm) and controlled air moisture. The experiment in real conditions in poultry a slaughterhouse showed more than 2 log10 (99.22%) (in average 40-70%) of test bacteria (L. innocua) reduction on the PET test plates coated by titanate nanotubes, induced only by fluorescent light and air conditions.

fluorescent illumination with its UV-A (350 nm) irradiation. Consequently, test surfaces were wet, thus the moisture had a positive and significant influence on the titanate nanotubes free radicals release. Presumably, the contact temperatures of the test slides have no significant effect on the antibacterial effect of coatings. The intensity of the UV-A irradiation in the spectrum of fluorescent lights in food plants was obviously enough for the free radicals release.

The results of existing laboratory tests on the influence of titanate nanotubes coating on the reduction of L. innocua were rather moderate, presumably due to believable nanotubes aggregation and inhomogeneity and moreover, inconstant nanotubes loading on the surfaces of the tested glass (or PET test plates). The results of tests in a poultry slaughterhouse were rather different, owing to changeable air conditions and

Plans Further research work will be focused on improving the bactericidal effectiveness by improving the procedure of surface coating on PE test plates. This experiment indicates the possibility of the future use of titanate nanotubes coatings in the food industry.

Figure 5.8: Testing of antimicrobial efficiency in a slaughterhouse

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2. DOBEIC, M., PINTARIČ, Š., ZDOVC, I., GOLOB, M., KOKLIČ, T., KURE, S., ŠTRANCAR, J.. Titanate nanotubes as antibacterial coatings for control of Listeria in food plants. V: KÖFER, Josef (ur.), SCHOBESBERGER, Hermann (ur.). Proceedings of the 15th International Congress of the International Society for Animal Hygiene, July 3 - 7, Vienna, Austria. XV ISAH Congress 2011. Animal hygiene and sustainable livestock production : innovations in hygiene, nutrition and housing for healthy food from healthy animals. Brno: ISAH, 2011, 1171-1173. 3. PINTARIČ, Š., DOBEIC, M., ZDOVC, I., GOLOB, M., GREBENC, S., ŠTRANCAR, J.. Use the centrifugal samplers for detection of microorganisms in the air. V: KÖFER, Josef (ur.), SCHOBESBERGER, Hermann (ur.). Proceedings of the 15th International Congress of the International Society for Animal Hygiene, July 3 - 7, Vienna, Austria. XV ISAH Congress 2011. Animal hygiene and sustainable livestock production : innovations in hygiene, nutrition and housing for healthy food from healthy animals. Brno: ISAH, 2011, 785-787. 4. DOBEIC, M., KENDA, E., PINTARIČ, Š., ZDOVC, I.. Listeria contamination in meat processing plants. V: BRIESE, Andreas (ur.). XIV ISAH congress 2009, 19th to 23rd July, Vechta, Germany. XIV ISAH congress 2009. Sustainable animal husbandry : prevention is better than cure. Brno: ISAH, 2009, 831-834, Vol.2.


MICROSPECTROSCOPIES FOR NANOPARTICLE IN-CELL TRACKING

Janez Štrancar 1996: graduate in physics (Faculty of Mathematics and Physics, University of Ljubljana, Slovenia): with thesis: Študij transporta spinsko označenih lipofilnih molekul skozi biološke membrane z metodo elektronske paramagnetne resonance From 1997: Employed at Jozef Stefan Institute 2000: PhD in biophysics (University of Ljubljana) with thesis: EPR spectroscopy of cell membrane surface 2002-2003: Postdoc at Institute of Biophysics and X-ray Structure Research, Graz, Austria 2005: Habilitation in nanobiophysics at Jozef Stefan International postgraduate School From 2006: Head of the Laboratory of Biophysics and Research Program Experimental biophysics of Complex Systems From 2008: Lecturer at University of Maribor, Faculty of Natural Scuences and Mathematics (Physical Measurements) From 2009: Lecturer at University of Ljubljana, Faculty of Pharmacy (Molecular biophysics) From 2010: Head of the RRP5 project at CoE NAMASTE Most important work: 1. ŠTRANCAR, J., KOKLIČ, T., ARSOV, Z., FILIPIČ, B., STOPAR, D., HEMMINGA, M. A. Spin label EPR-based characterization of biosystem complexity. J. chem. inf. mod., 2005, vol. 45, no. 2, 394-406 2. KAVALENKA A., URBANČIČ I., BELLE V., ROUGER S., COSTANZO S., KURE S., FOURNEL A., LONGHI S., GUIGLIARELLI B., ŠTRANCAR. J. Conformational analysis of the partially disordered measles virus N[sub](TAIL)-XD complex by SDSL EPR spectroscopy. Biophys. j., 2010, vol. 98, no. 6, 1055-1064. 3. ARSOV, Z., URBANČIČ, I., GARVAS, M., BIGLINO, D., LJUBETIČ, A., KOKLIČ, T., ŠTRANCAR, J.. Fluorescence microspectroscopy as a tool to study mechanism of nanoparticles delivery into living cancer cells. Biomedical optics express, 2011, vol. 2, no. 8, 2083-2095

Currently available experimental methods allow the identification of very diverse phenomena on the subcellular level. Different cell organelles can be studies together with different cell processes. However, one of the main obstacles of the current methods is to identify, locate and trace submicron particles in living cells. Classical high resolution imaging methods like SEM and TEM cannot be applied under the physiological conditions required to study living cells. AFM and SNOM are applicable only at the surface of the cell, so tracking inside is almost impossible. On the other hand, standard visual light microscopy does not have the required resolution. The problem seems to be solved by the so-called superresolution techniques, but their application is still problematic due to positional stability problems.

Figure 5.9: Fuorescence microspectroscopy upgraded with IR tweezer and Raman microspectroscopy

case, the FMS system was developed with regard to our expertise in experiment-specific probe design and synthesis. Such an approach also requires a certain degree of flexibility in the excitation light source. Because our FMS system is based on a noncoherent xenon arc-lamp source, the confocal system also needs to be chosen accordingly, i.e., among the systems based on a spinning disk. This means that the image is acquired at the same time and not in a point-scanning manner. Therefore, the spectral detection method needs to be based on the sequential image acquisition through tunable, narrow-band-pass filters; in our case a liquid-crystal tunable filter (LCTF).

To overcome the problem of the resolution and experimental conditions at the same time, our developments are based on the fact that submicron particles and molecular identification can be done via spectral analysis instead of spatial resolution. Resolving spectroscopic information with a submicron resolution would therefore allow studying the molecular environment in living cells. Fluorescence microspectroscopy (FMS) For this purpose, a fluorescence microscope was upgraded to acquire spectral information in every pixel of the image. With the application of environmentally sensitive probes it is therefore possible to characterize the local molecular environment of the fluorophores via spectral analysis, while locating them with the resolution of fluorescent microscopy. The merging of the fluoresce spectroscopy and microscopy can be identified as fluorescence microspectroscopy (FMS).

The main disadvantage of a system with simultaneous channels is the spectral resolution at the desired sensitivity. For example, a system with 32 channels (merged with wavelengthdispersive systems) working in a broad spectral range (like 300 nm) provides poor resolution at the same sensitivity as our system. With respect to the typical fluorescence spectrum linewidth of 50-80 nm, such a device would provide only 5-8 points characterizing the emission spectrum. In our case, LCTF can be adjusted in 1 nm steps with a 10 nm filtering width, enabling much better resolution at the same sensitivity. The distortion of a lineshape is still small since the linewidth is much larger than 10 nm. When working in a narrow spectral range, like 30-60 nm, a 32 channel system would have the same resolution, but with 10-times lower

FMS based on a white-light source There are basically two ways of acquiring spectral information with a microscope, either through spectral analysis of the light from the single voxel by the means of wavelength dispersive systems or by sequential image acquisition through tunable narrow-band-pass filters. The choice of the method depends on the way the confocal microscopy is realized. In our

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(a) Wavelength (lambda) stack

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Figure 5.10 Principle of FMS operation: wavelength-dependent stack of images are used to extract spectral information which are color-encoded in final spectrally-contrasted image

sensitivity due to a 1 nm filter width, meaning that it needs to increase the exposure times by 10 times. Taking these facts into account, our system can be better on a full-image highresolution microspectroscopic analysis, while the point-scanning systems with wavelength-dispersive systems show their advantages in the case when not the whole image has to be scanned.

spectral maximum down to 1 nm can be resolved. With such characteristics, the FMS application is straightforward, for example, to identify and track nanoparticles in living cells. Upgrading Recently, the FMS system was upgraded with IR tweezers to manipulate the particles and the cells as well as to perform various stress experiments to trace the response of the cells on the interaction with the particles and other materials.

Spectral information is transformed into colors with a spectral-features coding allowing (co)localization of fluorescent particles and probes with considerably overlapping emission spectra, spectral-based identification and tracking of the nanoparticles, smaller than the optical diffraction limit, and finally, characterization of very small differences in the local environment detected by environmentally sensitive probes. A shift in the brightfield intensity

Currently, the FMS system is being upgraded with Raman microspectroscopy to complement the fluorescence picture with Raman information about the local chemical composition.

fluorescence intensity

fluorescence spectral coding

Obdelano z bleaching korekcijo - colocalization with lyzosomes SHIFT

μmcelicah inkubiranih z Kolokalizacija v10 MCF7 TiNT-Alexa in Mytotracker

TiNT-NBD in Lyzotracker

TiNT-NBD

MAXIMUM

Figure 5.11: Comparison of brightfield , conventional fluorescence microscopy and FMS based on spectral properties coding. Several applications of collocalization experiments are shown (bottom).

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ARSOV, Z., URBANČIČ, I., GARVAS, M., BIGLINO, D., LJUBETIČ, A., KOKLIČ, Tilen, ŠTRANCAR, J.. Fluorescence microspectroscopy as a tool to study mechanism of nanoparticles delivery into living cancer cells. Biomedical optics express, 2011, vol. 2, no. 8, str. 2083-2095. KUŻDŻAŁ, M., WESOŁOWSKA, O., ŠTRANCAR, J., MICHALAK, K.. Fluorescence and ESR spectroscopy studies on the interaction of isoflavone genistein with biological and model membranes. Chem. phys. lipids. [Print ed.], 2011, vol. 164, no. 4, str. 283-291, doi: 10.1016/j.chemphyslip.2011.03.001. PAJK, S., GARVAS, M., ŠTRANCAR, J., PEČAR, S.. Nitroxide-fluorophore double probes: a potential tool for studying membrane heterogeneity by ESR and fluorescence. Organic and Biomolecular Chemistry. [Print ed.], 2011, vol. 9, issue 11, str. 4150-4159.


CELLULAR INTERNALISATION OF NANOPARTICLES

Motivation

Model tissue and nanoparticles

Understanding of nanoparticle interactions with cells is a great challenge that must be met to understand the positive and negative roles of synthetic nanoparticles when used in medicine, pharmacy and the food industry.

In our study we use the digestive gland epithelium of a model invertebrate organism to study the internalisation of different types of nanoparticles after ingestion. Studied nanoparticles differ in chemical composition, surface characteristics and shape.

In vivo experimental set up Damjana Drobne 1989: Graduate in biology (University of Ljubljana , Slovenia) with thesis ... From 1996: Employed at UL 1996: PhD in biology / environmental toxicology (UM) with thesis: ... From 2004: Vice head of the Department of biology, BF.UL From 2007: Full professor for Toxicology, BF.UL From 2008: Full professor for Zoology, BF.UL From 2008: Head of Research Group for Nanobiology and Nanotoxicology at the Department of Biology at University of Ljubljana From 2011: Employed at UM (100%) and at CoE NAMASTE (20%).

An in vivo study is conducted with a model terrestrial organism (terrestrial isopod Porcellio scaber Isopoda, Crustacea) where nanoparticles are mixed with food. Individual animals are kept in Petri dishes and feed either with untreated food, or those treated with nanoparticles for two weeks. A suspension of nanoparticles is applied on the surface in a known amount of dried hazel leaves (Corylus avellana) and offered as a food source.

Up to now we have studied superparamagnetic cobalt-ferrite nanoparticles (CoFe2O4 with different surfaces, nano-ZnO and nano-TiO2. Superparamagnetic nanoparticles with appropriate surface chemistry have been widely used experimentally for numerous in vivo applications, such as magnetic resonance imaging contrast enhancement, tissue repair, immunoassay, detoxification of biological fluids, hyperthermia, drug delivery and in cell separation, etc.

After in vivo exposure, either the entire animals (from in vivo experiments) or tissue is cryo sectioned (10 µm thick) and prepared for TwinMic (Eletrra, Trieste) or cryo sectioned (50 µm thick) and prepared for PIXE.

Metal oxide nanoparticles are already manufactured on a large scale for both industrial and household use, yet hold even greater promise for future applications. For example, titanium dioxide nanoparticles are already used

Most important work: PIPAN TKALEC, Ž., DROBNE, D., VOGELMIKUŠ, K., PONGRAC, P., REGVAR, M., ŠTRUS, J., PELICON, P., VAVPETIČ, P., GRLJ, N., REMŠKAR, M.. Micro-PIXE study of Ag in digestive glands of a nano-Ag fed arthropod (Porcellio scaber, Isopoda, Crustacea). Nucl. instrum. methods phys. res., B Beam interact. mater. atoms. [in press] 2011, 10 str. MENARD, A., DROBNE, D., JEMEC, A.. Ecotoxicity of nanosized TiO2. Review of in vivo data. Environ. pollut. (1987). 2011, vol. 159, issue 3, str. 677-684. VALANT, J., DROBNE, D., NOVAK, S.. Effect of ingested titanium dioxide nanoparticles on the digestive gland cell membrane of terrestrial isopods. Chemosphere (Oxford). 2011,

Figure 5.12: Scanning electron (left) and light mirograph (right) of digestive gland epithelium. White square indicates a region of two cells which correcposnds to one further investigated by XRF at Elettra, Trieste.

Figure 5.13: XRF elemental maps of F and Co and their co-localistion, camples prepared by Sara Novak; XRF analyses B. Kaulich and A. Gianoncelli; Elettra, Trieste. (Sample 19 CoFe2O4 2000)

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Experiment - 32, nano CoFe2O4 fed (2000 ppm), No 43

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Figure 5.14: PIXE elemental maps of of digestive glands treated with CoFe 2O4, samples prepared by Sara Novak; PIXE analyses performed by P. Pelicon, P. Vavpetič, IJS. (Sample 32 CoFe2O4 2000, No. 43)

as UV-blocking agents in sunscreens, in photocatalytic water purification and will likely be used in the new generation of solar cells. Zinc oxide nanoparticles are a starting material for electronics applications, transparent UV-protection films and chemical sensors, as well as UV-filters in sunscreens.

the CoFe2O4 particles. Therefore, we conclude that nanoparticles did not enter the cells, but only dissolved the Co. Similar to XRF maps, PIXE maps also reveal that since the Co and Fe distribution inside the cells did not overlap. Again we have confirmed on a larger scale that the two elements entered cells as ions and not particles.

XRF analyses of CoFe2O4 treated tissue nanoparticle reated tissue

Cellular internalization was also studied for nanoZnO and nanoTiO2 particles (Valant et al. 2009, Pipan-Tkalec et al. 2009).

The XRF maps of tissue samples treated with CoFe2O4 nanoparticles have revealed the location, distribution and co-localisation of selected elements. The colocalisation of Fe and Co was found only in places. Here, the ratio between Co and Fe is different than in

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PIPAN TKALEC, Ž., DROBNE, D., JEMEC, A., ROMIH, T., ZIDAR, P., BELE, M.. Zinc bioaccumulation in a terrestrial invertebrate fed a diet treated with particulate ZnO or ZnCl2 solution. Toxicology (Amst.). [Print ed.], 2010, iss. 2-3, vol. 269, 198-203. VALANT, J., DROBNE, D., SEPČIĆ, K., JEMEC, A., KOGEJ, K., KOSTANJŠEK, R.. Hazardous potential of manufactured nanoparticles identified by in vivo assay. J. hazard. mater.. [Print ed.], 2009, issues 1-3, vol. 171, 160-165.


NANOPARTICLES IN THE ENVIRONMENT

Motivation

Maja Remškar 1985: Graduate in physics (Faculty of Mathematics and Physics ,University of Ljubljana, Slovenia): From 1987: Employed at Jozef Stefan Institute 1994: PhD in physics in the field of Condensed Matter Physics 1995: Postdoc at EPFL | ÉcolePolytechniqueFédérale de Lausanne, Lausanne, Switzerland 2003: Habilitation at University of Ljubljana From 2002: Head of the Laboratory for Synthesis of Inorganic Nanotubes and Ropes From 2004: Member of Governmental Commission for Women in Science From 2010: Employed at CoE NAMASTE, CoE PoliMaT and CoE Nanocenter Most important work: ISKRA, I., DETELA, A., VIRŠEK, M., NEMANIČ, V., KRIŽAJ, Dejan, GOLOB, D., ELTEREN, D. T. van, REMŠKAR, M.. Capacitive-type counter of nanoparticles in air. Appl. phys. lett., 2010, vol. 96, no. 9, 093504-1-0935043

In the last two decades, with the introduction of new technologies and materials, emissions of particles on the nanoscale become an important topic. Because of the ignorance and insufficient know-ledge about nanoparticles there is a thought that the material in that form may pose potential health risks. Although there are regulations which govern the limits of the quantity of micron sized particles in the air, current guidelines are not sufficient to define the limits for nanoparticles.

Figure 5.15: Particle detector prototype

develop a different method - counting. We developed a unique method for detection of nanoparticles in the air which employs a completely different sensoric principle. Unlike other commercial devices which use the optical detection of liquid encapsulated nanoparticles our sensor detects those droplets in an electrical way. The method has proven successful and unique and is covered by a patent. In addition to a sensor, the entire condensation particle counter prototype was also developed. Numerical simulations confirmed the experimental signal form and indicated the direction of optimization for the sensor.

Nanoparticles can directly influence human welfare, health and the environment in which they are located. In terms of toxicity, they probably have a large impact on human health. From the meteorological point of view, they probably influence the weather like larger particles, as shown by various physical and chemical properties similar to those of larger particles. Because of all the effects written above, in recent years new devices that are able to detect individual nanoparticles in aerosol were developed. Because of their low mass, standard methods of weighing cannot be evaluated. It was necessary to

REMŠKAR, M., ISKRA, I., VIRŠEK, M., PLEŠKO, M., GOLOB, D.. Metoda in kapacitivnostni senzor za štetje aerosolskih nanodelcev : patent : SI 22895 (A), 2010-04-30. Ljubljana: Urad RS za intelektualno lastnino, 2010. 19 str., ilustr. REMŠKAR, M.. Safe nanotechnology and monitoring of airborne particulates in work environment : invited talk. Stockholm: Royal Institute of Technology, Deparment of production engineering, 10. okt. 2011

Figure 5.16: Panoramic view on mechanical workshop. Particle counter was placed in the left corner where bushing, polishing and welding takes place.

Figure 5.17: Particle concentration spectra in mechanical workshop during a work day

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Figure 5.18: Well defined increase of particle emissions, sizes between 60 and 100nm, during the fireworks event (Friday evening 24.6.2011)

Figure 5.19: Spectra of particle size concentration between 7.5 and 300nm (Zagorje ob Savi)

Monitoring different environments

pyrotechnics uses different metallic powders for various colours. During the explosions at extremely high temperatures, vapours of that material form new particulates - nanoparticles. By classical atmospheric processes, these particles then accumulate and aggregate into bigger particles of different morphologies.

With the portable nanoparticle spectrometer (TSI SMPS 3936L85), which is commercially available on the market, we are able to perform field measurements of particulate matter below 1 µm (particle diameter) in different environments. Since no one makes these measurements, we decided to check the emission rates on the nanoscale in several distinctive places.

In connection with local authorities and the national environmental agency (ARSO) we performed ambient-air monitoring in one of the most polluted cities – Zagorje ob Savi. Results revealed extremely high concentrations at the lower end of the measurement scale (especially below 20 nm nucleation range).

Inside the institute we performed a one week measurement in a mechanical workshop. The results showed extremely high emission rates during individual events where concentrations of particles below 100 nm reached 7 3 2∙10 particles/cm . The total concentration, which was recognized as a background, was rather high - 4 times higher than the average office environment.

In Koper (close to the port of Koper) preliminary measurements of two weeks were made. The motivation came from warnings by the Public Health Institution, which claimed that the origin of PM emissions is the port (terminal for minerals). Of course, there are also emissions from public and marine transport.

Another investigation took place in Ljubljana city centre during the Independence day celebration with fireworks. It is well known that

KRIŽAJ, D., ISKRA, I., REMŠKAR, M.. (Quasi 3D) numerical simulation of operation of a capacitive type nanoparticle counter. J. electrost.. [Print ed.], Dec. 2011, vol. 69, no. 6, 533-539. KRIŽAJ, D., ISKRA, I., REMŠKAR, M.. Numerical modeling of a capacitive type detector of airborne nanoparticles. V: JOBBÁGY, A. (ur.). 5th European Conference of the International Federation for Medical and Biological Engineering, 14-18 September 2011, Budapest, Hungary. IFMBE proceedings, (IFMBE proceedings, vol. 37). Berlin; Heidelberg; New York: Springer, cop. 2011, 1303-1306 BEESTON, M.P., GRGIĆ, I., ELTEREN, J.T. van, ISKRA, I., KAPUN, G., MOČNIK, G.. Chemical and morphological characterization of aerosol particles at Mt. Krvavec, Slovenia, during the Eyjafjallajökull Icelandic volcanic eruption. Environ. sci. pollut. res. int.. [Print ed.], 2012, vol. 19, no. 1, 235-243 ISKRA, I., KÁVÁSI, N., VAUPOTIČ, J.. Nano aerosols in the Postojna cave = Nano aerosoli v Postojnski jami. Acta carsol., 2010, vol. 39, no. 3, 523-528. KRIŽAJ, D., ISKRA, I., REMŠKAR, M.. Multiphysics modelling of nanoparticle detection / current status and collaboration sought. V: Comsol Conference, October 26-28, 2011, Stuttgart. Proceedings CD. [S. l.]: Comsol, 2011, 1-3 REMŠKAR, M., ISKRA, I., VIRŠEK, M., PLEŠKO, M., GOLOB, D.. Metoda in kapacitivnostni senzor za štetje aerosolskih nanodelcev : patent : SI 22895 (A), 2010-04-30. Ljubljana: Urad RS za intelektualno lastnino, 2010. 19., ilustr.

Figure 5.20: Well defined increase of particle emissions, sizes between 60 and 100nm, during the fireworks event (Friday evening 24.6.2011)

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REMŠKAR, M., ISKRA, I.. Nanotechnology and health : How do we safely produce and utilize nanoparticles? : invited talk; International simposium on environment protectiona, 20 maj 2011, Ljubljana, Slovenija


BIOMATERIALS: CERAMICS FOR DENTAL APPLICATIONS

Tomaž Kosmač 1974: Graduate in Metallurgy from University of Ljubljana 1978: M.Sc.in Metallurgy from University of Ljubljana 1982: PhD in Chemistry from University of Ljubljana Since 1974 : Jozef Stefan Institute, Ljubljana, Slovenia 1979 – 1980: On leave with Max Planck Institute for Metal Research, PML, Stuttgart, FRG, as visiting research fellow 1990 – 1991: Visiting Associate Professor at the University of Virginia, Mat. Sci. Dept., Charlottesville VA Present position at IJS: Head of Engineering Ceramics Department Part-time full professor, Metallurgy and Materials Dept., University of Ljubljana Most important work: KRNEL, K., KOCJAN, A., KOSMAČ, T.. A simple method for the preparation of nanostructured aluminate coatings. J. Am. Ceram. Soc., 2009, vol. 92, no. 10, 2451-2454. JEVNIKAR, P., KRNEL, K., KOCJAN, A., FUNDUK, N., KOSMAČ, T.. The effect of nano-structured alumina coating on resin-bond strength to zirconia ceramics. Dent Mater. 2010, vol. 26, no. 7, 688-696, PERKO, S., DAKSKOBLER, A., KOSMAČ, T.. High-performance porous nanostructured ceramics. J. Am. Ceram. Soc., 2010, vol. 93, issue 9, 2499-2502,

The growing demand for esthetic restorations in dentistry has led to the development of tooth-colored, metalfree systems. In most cases, yttria partially stabilized tetragonal zirconia (Y-TZP) is used as the core material, owing to its superior mechanical properties, chemical stability and biocompatibility. For the same reasons, zirconia-based, full-ceramic post-andcore and implant system superstructures were introduced to replace traditionally used metals.

microstructure, the materials’ prehistory and testing conditions. The process is grain-size dependent and is further influenced by chemical and microstructural inhomogeneities. While for retrieved Y-TZP femoral heads a relationship between the in-vivo and in-vitro ageing behavior has been established, no systematic ageing study with dental ceramics under clinical conditions has been performed so far. In order to pave way, an in-vivo experiment was designed to monitor the propagation of the t-m transformation of two bio-medical grade 3Y-TZP ceramics which were directly exposed to the aggressive environment of the oral cavity. Two high-purity “bio-medical-grade” powders (TZ-3YB-E and TZ-3YSB-E, Tosoh, Japan) were used to produce disc-shaped specimens with mean grain sizes of 0.51 um and 0.59 um, respectively. Four patients were provided with removable lower fulldentures, each with two fine-grained and two coarse-grained discs implanted in the lingual flange. After every six months the discs were removed and subjected to XRD and FEG-SEM surface analyses. The results after two years have clearly demonstrated that thermal cycling in the oral cavity fosters the diffusioncontrolled transformation on the surface of the zirconia ceramics. Based on the results obtained so far, one can conclude that “naked” surfaces are vulnerable and represent a potential threat of premature failure for allceramic dental restorations.

Despite the risk associated with the generic brittleness of ceramics, and that associated with the phase instability of Y-TZP ceramics under hydrothermal conditions, the interest in dental zirconia is growing. Driven by aesthetics, the dental zirconia market increases at a rate of 15 % per year and an even larger growth rate is expected in the future. Bioceramics, as integral part of the RRP5 project within the CoE NAMASTE, addresses some of the emerging problems related to the fabrication of tetragonal zirconia (Y-TZP) based allceramic fixed partial dentures (FPDs), their cementation as well as the performance of these FPDs under clinical conditions. Once exposed to cyclic mechanical and thermal loadings in the chemically aggressive environment of the oral cavity, the strength of the ceramic core material tends to diminish steadily over time, from stress corrosion, ageing and fatigue and the same holds for the interface bonding between the core material and the porcelain, as well as that between the core and the cement. Ageing, i.e., the low-temperature degradation (LTD) of zirconia is a welldocumented phenomenon. It is sensitive to the composition,

It has been shown that the long-term survival rate of zirconia-based dental restorations largely depends on the adhesive bond strength and a stronger bonding to the core would be advantageous for many clinical applications. Unfortunately, the establishment of a durable chemical or mechanical bonding to zirconia has proven to be difficult because of its surface stability. The most effective surface pretreatment so far involves air-particle abrasion using silica-modified alumina particles, followed by silanization. Since subsurface cracks that may be introduced during air-particle abrasion represent lifetime-threatening damage, this process has been seriously questioned. In order to eliminate the risk of premature failure, an alternative

Figure 5.21: Fine-grained and coarse-grained discs inserted in the lingual flange of removable lower full-denture

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solution to the adhesion problem was proposed that involves a non-invasive functionalization of the core ceramic surface, by applying a uniformly thin nanostructured alumina coating exhibiting a large surface area. For fabricating the coating, a relatively simple process was developed that exploits the dissolution/precipitation of aluminum hydroxides, which originate from the hydrolysis of AlN powder in an aqueous suspension. A nanocrystaline coating consisting of gammaAlOOH in the form of 6-nm-thick and 250-nm-long interconnected lamellas can be formed in this way. 0By a heat treatment at 600-1200 C these lamellas will be transformed to a transient alumina without any noticeable change in the morphology, but their bonding to the substrate will be significantly improved. This coating has a potential to improve the adhesion of dental cements to a sintered ceramic substrate by a factor of 2-4, depending on the surface roughness of the substrate and the dental cement used.

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Figure 5.22: Time dependence of the formation of monoclinic zirconia during autoclaving at 134 °C in an artificial saliva

of nanoparticles and submicron-sized particles a large interparticle area was formed during biscuit-sintering, resulting in a moderately porous material with increased strength, as a consequence of a retarded sintering process and the thereby related evolution of strength-determining pores in the biscuit-sintered material. The addition of nanoparticles was achieved by mixing aqueous suspensions of nanoparticles and submicron-sized particles. A uniform distribution of nanoparticles attached to the surface of the submicron-sized particles was achieved by manipulating the interparticle forces. These samples were shaped by slip casting, while the development of a pressure filtration device is underway. Regardless of the preparation route, the material was sintered without any substantial shrinkage to achieve a moderate (60%80%) relative density. Macroscopically, the kinetics of sintering was followed by a dilatometer, whereas on the lower scale an in-situ sintering study was performed using a high-resolution transmission electron microscope.

Yet another part of the project is aimed at developing moderately porous Y-TZP ceramics exhibiting a substantially reduced elastic modulus similar to that of the dentin, and a sufficiently high strength for dental applications. A diminished elastic mismatch is expected to reduce the magnitude of the stresses developed at the margin of the tooth and the restoration and therefore the likelihood of marginal seal failure and the onset of secondary caries. The easiest way of reducing the elastic modulus of a ceramic material is by introducing moderate porosity, though at the expense of reduced mechanical properties and aesthetic appearance. It is believed that a compromise between the elastic and mechanical properties can be obtained in this way, whereas additional porcelain veneering is expected to “seal” the surface of the core material and to reestablish the aesthetic appearance. The targeted values of the elastic modulus and flexural strength are 80 GPa and 800 MPa, respectively. It was shown that by blending proper amounts

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Figure 5.23: A nano-crystaline coating consisting of boehmite (AlOOH) lamellas

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ŠTEFANIČ, M., KRNEL, K., PRIBOŠIČ, I., KOSMAČ, T.. Rapid biomimetic deposition of octacalcium phosphate coatings on zirconia ceramics (Y-TZP) for dental implant applications. Appl. surf. sci.., 2012, vol. 258, issue 10, 4649-4656. JEVNIKAR, P., GOLOBIČ, M., KOCJAN, A., KOSMAČ, T.. The effect of nanostructured alumina coating on the bond strength of resin-modified glass ionomer cements to zirconia ceramics. J. Eur. Ceram. Soc., 2641-2645. KOSMAČ, T., KOCJAN, A.. Ageing of dental zirconia ceramics. J. Eur. Ceram. Soc.., 2012, vol. 32, no. 11, 2613-2622. ŠTEFANIČ, M., KRNEL, K., KOSMAČ, T.. Thermal processing of calcium phosphate coatings on zirconia ceramics. Key eng. mater., 2012, vol. 493/494, 462-466. HANSHINGUCHI, M., SATO, H., NISHI, Y., KRNEL, K., KOCJAN, A., KOSMAČ, T.. Effect of surface treatments on bonding strength of zirconia to dental ceramics. Key eng. mater., 2009, vol. 396/398,575-578.


POLYMER SCAFFOLDS FOR TISSUE ENGINEERING

Vanja Kokol 1994: Graduate in textile chemistry (University of Maribor = UM, Slovenia) with thesis Ecological and technological optimization of parameters in reactive printing of viscose. From 1994: Employed at UM 1996-1997: Scientific visit at Institut für Textilchemie der Deutschen Institut für Textil- und Faser-forschung, Denkendorf, Germany 1998: MSc in textile chemistry (UM) with thesis: The consequence of interactions between the guar thickener and different types of reactive dyes. 2001: PhD in textile chemistry (UM) with thesis: Investigation of interactions between guar gums, reactive dyes and surfactants. 2002: Postdoc at German Wool Research Institute, Aachen, Germany 2005: Habilitation in Textiles at University of Ljubljana. 2006 and 2008: Scientific visit at Institute for Environmental Biotechnology, TUG, Austria 2007: Scientific visit at Lund University, Physical Chemistry, Sweeden 2009: Scientific visit at Max Planck Institute of Colloids and Interfaces, Golm, Germany 2010: Habilitation in Textile Chemistry and Eco-textile Engineering at UM From 2011: Employed at UM (100%) and at CoE NAMASTE (20%). Most important work: CORTEZ, J., FATARELLA, E., NESTI, S., KOKOL, V., SCHROEDER, M.. Process for functionalising polymer materials and functionalised polymer materials so obtained : WO patent, 2009/019567 A2, 12. 2009; PCT/IB2008/002030, filling date: 1. August 2008. WIPO, International Bureau, 2009. JUS, S., KOKOL, V., GÜBITZ, G. M. Tyrosinase-catalysed coating of wool fibres with different protein-based biomaterials. J. biomater. sci., Polym. ed., 2009, 20, no. 2, 253-269. SOUSA, F. de, GÜBITZ, G. M., KOKOL, V.. Antimicrobial and antioxidant properties of chitosan enzymatically functionalized with flavonoids. Process biochem. (1991), July 2009, vol. 44, iss. 7, 749-756

Scaffolds used in tissue engineering should meet many different requirements, from the biocompatibility of the scaffold building blocks to the scaffold’s physical properties, like porosity, which directs tissue formation, enables oxygen and nutrition diffusion toward the cells and drains waste products from the matrix. Both, the composition and pore interconnectivity are essential for the promotion of cell attachment, growth, migration and angiogenesis. Biodegradability is another issue that plays a significant role in cell attachment, and ECM replacement of the live tissue. It is one of the most desirable properties of a smart implant to degrade on exactly the same time scale as nature tissue can restore its own ECM. Gelatin-based scaffolds The main advantages of the gelatine are bio and cyto-compatibility, where desirable cellular responses are engaged with the Arg–Gly–Asp (RGD)like sequence of gelatin, promoting cell adhesion and migration and being responsible for its helicoidal restructuring at specific temperature conditions, low-level immunogenicity and cytotoxicity, good biodegradability and bioresorbability, and great capacity for modification at the level of aminoacids. Thus, one of our activities is to optimize the preparation procedure and composition of gelatin-based scaffold and increase its biocompatibility with certain cell types, depending on the scaffold application. Research activities are conducted comprising both bio-engineering of the scaffolds, including gelatin biochemical processing like modification and functionalization, as well as the formation of three-dimensional (3D) structures.

Figure 5.24: Gelatin scaffolds, prepared in carbonate (top) and in phosphate buffer (bottom) under physiological conditions via fuorescence confocal microscopy; field of view is 500 m

Non-cytotoxic crosslinking agents (biochemical and enzymatic) and medias (water, ethanol) are used to formulate the porous matrices of different surface/interfacial properties, strength, viscoelasticity, and thermal and biostability. Combinations with other (nano)biopolymers (e.g. chitosan, bacterial cellulose) are also combined with gelatin to overcome these limitations. We showed that only by changing the freezing dynamic in the lowtemperature range and media used during cross-linking, it was able to influence the thermal and mechanical stability of the gelatine matrix, which can be further modulated by the procedure and the strength of the cross-linking.

Different preparation conditions using temperature and time-regulated freezing and crosslinking steps, with or without an intermediate lyophilisation, are applied to  Enable the formation of an appropriately sized and interconnected porous structure and facilitate the proliferation of cells and  guarantee the appropriate stability of the scaffolds in solutions at physiological conditions.

It was shown that the gelatine scaffold microstructure can be modulated by employing a cryogenic pre-treatment using the end-temperature and time variation, lyophilisation and subsequent crosslinking of the gelatine with zero-length crosslinkers (EDC/NHS) in different molar concentrations, reaction times (1-24 h) and medium used

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CORTEZ, J., FATARELLA, E., NESTI, S., KOKOL, V., SCHROEDER, M.. Process for functionalising polymer materials and functionalised polymer materials so obtained: WO patent, 2009/019567 A2, 12. February 2009; filling no. PCT/IB2008/002030, filling date: 1. August 2008. World Intellectual Property Organization, International Bureau, 2009. ŠTRANCAR,J., KOKOL,V. GORGIEVA. ,S.Method for preparation of biopolymeric scaffolds using temperature-regulated simultaneous freezing, crosslinking and un-freezing without intermediate lyophilisation. Patent application in submition. CIOLACU, D., GORGIEVA, S., TAMPU, D., KOKOL, V.. Enzymatic hydrolysis of different allomorphic forms of microcrystalline cellulose. Cellulose, 2011, 18/6, 1527-1541. BOŽIČ, M., GORGIEVA, S., KOKOL, V.. Laccase-mediated functionalization of chitosan by caffeic and gallic acids for modulating antioxidant and antimicrobial properties. Carbohydr. polym. 2012, 87/4, 2388-2398. Figure 5.25: Gelatin scaffolds populated with fibroblast cell line in 2 days, prepared in phosphate buffer under physiological conditions via FCM; field of view is 500 m

(PBS-P, PBS/EtOH-PE). A lower freezing temperature (-16 °C) and a higher crosslinking concentration induce the random formation of numerous, smaller pores (70-200 µm) with thinner pore walls (5-15 µm), when compared with radially-oriented larger pores (180-420 µm) with pore walls (5-30 µm) obtained at -12 °C. The crosslinker concentration had a pronounced influence on the pore morphology, giving rise to a round shape with a flatwall surface. EtOH induced additional folding of the pore walls to higher thicknesses, being especially pronounced at -16 °C, with the thicknesses of up to 35 µm and pore sizes of 35-160 µm, compared to wall thicknesses of 20-30 µm and pore sizes of 85-155 µm created at -12°C.

(FCM) by additional fluorescence labelling of the samples prior to measurements. Supporting proliferation

cell

growth

and

Cell attachment and their in-growth into the formed matrixes are analyzed by FMS. Standard cell lines are used, such as fibroblasts and chondrocytes. In addition, cancer cells, like breast cancer cell line, are also tested to study the differences in material-induced normal and cancer-cell growth. Plans Further research work will be focused on improving the preparation procedures of gelatine and gelatine/nanocellulose scaffolds using temperatureand time-regulated simultaneous freezing, crosslinking and un-freezing steps, without an intermediate lyophilisation, performing variations in a porous structure to facilitate the proliferation of cells, and to guarantee the appropriate stability of the scaffolds in solutions under physiological conditions. In addition, zeta-potential measurements will be introduced to evaluate scaffold outer and innersurface/interface properties, being a preliminary parameter for the prediction of cell attachment and their in-growth.

The crosslinking degree was identified by the UV-Vis spectro-photometric TNBS method, while IR spectroscopy (FTIR-ATR) was used to demonstrate the changes in amide-absorption regions, caused by the formation of new peptide bonds between basic (amino) and acidic (carboxyl) groups from the gelatine polymer. Using differential scanning calorimetry (DSC) we confirmed a significant transition temperature (Tm ≈ 35 °C), at which the changes in morphological and topographical matrix micro-structure (porosity, pore size and shape, wall thickness, surface) were identified by scanning electron microscopy (SEM) and fluorescence confocal microscopy

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GORGIEVA, S., KOKOL, V.. Preparation, characterization and in vitro enzymatic degradation of chitosan-gelatine hydrogel scaffolds as potential biomaterials, J. Biomed. Mater. Res.: Part A; in press, 2012. GORGIEVA, S., KOKOL, V.. Collagen- vs. gelatine-based biomaterials and their biocompatibility : review and perspectives. V: PIGNATELLO, Rosario (ur.). Biomaterials applications for nanomedicine. Rijeka: InTech, cop. 2011, 17-52


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Advising Servicing Education Research projects

New opportunities 95


RRP6

Engaging academic and technological experts for the creation of technological breakthroughs Motivation

Danjela Kuščer 1992: Graduate in University of Ljubljana, Faculty of Chemistry and Chemical Technology From 1992: Employet at Jozef Stefan Institute, Ljubljana 1999: PhD in material science, University of Ljubljana, Faculty for Chemistry and Chemical technolgy 2009: Habilitaion in Material science at Jožef Stefan International Postgraduated school From 2011: Head of the RRP6 project at CoE NAMASTE Most important work: KUŠČER, D., TCHERNYCHOVA, E., KOVAČ, J., KOSEC, M.. Characterization of the amorphous phase and the nanosized crystallites in high-energymilled lead-magnesium-niobate powder. J. Am. Ceram. Soc., 2009, vol. 92, no. 6, 1224-1229. KUŠČER, D., STAVBER, G., TREFALT, G., KOSEC, M.. Formulation of an aqueous titania suspension and its patterning with ink-jet printing technology. J. Am. Ceram. Soc., 95 [2] 487–493 (2012). KUŠČER, D., LEVASSORT, F., LETHIECQ, M., ABELLARD, A.P., KOSEC, M.. Leadzirconate-titanate thick films by electrophoretic deposition for highfrequency ultrasound transducers. J. Am. Ceram. Soc., 95 [3] 892-900 (2012).

CoE NAMASTE is a multidisciplinary consortium of research institutions and industry from the field of advanced materials for electronic applications. The added value of this cooperation is the possibility to bring together several research groups and companies with state-of-the-art expertise in distinctly different scientific disciplines, including materials, chemistry, physics, biology, medicine, electronics and engineering. The intensive collaboration of the partners is reflected in advanced ideas, which are not included in the research work within other projects of CoE NAMASTE. The “Project of new opportunities” was established to address these advanced topics and also to financially support selected research work of the Centre of Excellence NAMASTE. The activities within this project include advising, educating, servicing and preparing project proposals.

Figure 6.2: Education is an important goal for CoE NAMASTE We organised workshop on Characterisation of materials and edited a Book of Proceedings

Servicing

Education

The servicing is an important activity of our project within the CoE. The partners within the CoE are equipped with new, advanced equipment. The partners within the consortium share the equipment and the experts from the selected field help with the interpretation of the results. Having access to up-to-date equipment is especially important for industry.

CoE is active in the field of education. So far we have invited 10 experts from all over the world to share their knowledge with CoE NAMASTE. CoE is an organiser or co-organiser of workshops and conferences from the field of material science, electronics, new areas of development, like microfluidics?

Figure 6.1: CoE NAMASTE is active in the field of servicing: Viscosity of ceramic suspensions as a function of share rate was measured for ETI Elektroelement d.d. Izlake, Slovenia.

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Partners: Institut „Jožef Stefan“ http://www.ijs.si

ETI Elektroelement d.d. http://www.eti.si

Figure 6.3: CoE NAMASTE is organiser or co-organisaer of national and international conferences. Prof. Kosec, the director of CoE NAMASTE opens the Conference „Napredni materiali s tehnologijami prihodnosti«. (The Advanced Materials for the Future)

Zavod TC SEMTO http://www.semto.si

New opportunities The activities within the “Project of new opportunities” and the very fast response of the Centre of Excellence present an advanced approach that improves the competitiveness of the industrial partners in a global market and gives the possibility to the partners to be actively involved in advanced trends in the field of materials for electronic applications.

Zavod TC SEMTO http://www.semto.si

Obrtno-podjetniška zbornica Slovenije http://ozs.si Figure 6.4: CO NAMASTE is active in advertising its activities (Ljubljana Trade Fair, 2011)

Figure 6.5: CoE NAMASTE was actively involved in the conference Innovativness 2011, Ljubljana, May 2011 (3 lectures)

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THE INFLUENCE OF PARTICLE SIZE AND OTHER CERAMIC RAW MATERIALS AND CERAMIC SUSPENSIONS ON SINTERED CORDIERITE MATERIALS

Helena Razpotnik 1995: Employed at ETI d.d. Izlake, R&D department 1998-2002: Graduate in chemistry (University of Maribor): with thesis: Porcelanska rjava glazura v ETI d.d. Izlake 2009-: Head of R&D department at ETI d.d. 2011 : Master’s degree (Jožef Stefan International Postgraduate School ): with thesis: Raziskave uporabnosti porcelanske črepinje pri pripravi gliničnega porcelana C-120 Most important work: MALIČ, B., RAZPOTNIK, H., KORUZA, J., KOKALJ, S., CILENŠEK, J., KOSEC, M.. Linear thermal expansion of lead-free piezoelectric K[sub](0.5)Na[sub](0.5) NbO[sub]3 ceramics in a wide temperature ranged. J. Am. Ceram. Soc., 2011, vol. 94, issue 8, 2273-2275 RAZPOTNIK, H., LAVRAČ, I., HOLC, J., KUŠČER, D., KOSEC, M.. Postopek za izdelavo gliničnega porcelana z izboljšanimi mehanskimi lastnostmi : patent SI23546 A. Ljubljana: Urad RS za intelektualno lastnino, 31. maj 2012. RAZPOTNIK, H., HOLC, J., KUŠČER, D., KOSEC, M.. Reciklaža žganega tehnološkega odpada materiala C-120 z namenom izboljšanja TWB odpornosti in upogibne trdnosti : poročilo za obdobje od novembra 2009 do oktobra 2010, (IJS delovno poročilo, 10627, zaupno). 2010

ETI d.d. is a producer of ceramic materials used in electrotechnical products with good insulating properties. Cordierite materials are the majority of insulating materials, which have good thermal shock resistivity, are used in high temperature applications, have good resistance at hightemperature and are chemically inert. According to the IEC 60 672 standard, which defines the characteristics of ceramic and glass insulating materials, cordierite materials are classified in groups of alumina and magnesium silicates C 400 and C 500. Cordierite materials from group C 400 and C 500, nonporouse cordierite C 410 and porouse cordierites C 520 and C 530, are mainly used in electrotechnics. The influence of raw materials and ceramic suspension characteristics on sintered cordierite materials characteristics The raw materials used in the preparation of cordierite materials are talc, clay, alumina, kaolin and fire clay. These are mostly natural raw materials, therefore they have the benefit for the price but a weakness for the quality stability, due to a higher deviation in chemical composition. There is also a certain negative effect on the material and product quality. The second issue which also has a substantial effect on material quality is the technological process. What is also important besides the raw materials quality is the milling process and, consequently, the suspension particle size distribution. They have a significant influence on sintering reactions and consequently on the sintered cordierite materials characteristics.

Figure 6.6: Products based on nonporouse cordierite C 410 (top) and porouse cordierites C 520 (middle) and C 530 (botom)

Particle size materials

distribution

of

raw

The particle size of raw materials was conducted with wet sieving on separate sieves. Within CoE NAMASTE a particle size analyser Cilas 920 was bought in 2010. It gives data about the particle size distribution in the whole range and enables better expertise in this field.

Within the CoE NAMASTE further research work will be performed, focusing on improving the cordierite materials regarding better quality stability, which will be achieved with changes in raw materials composition. The aim of scientific research will be the determination of the separate raw materials effect and individual raw material characteristics on the quality of sintered cordierite materials, including the determination of individual reactions during the sintering process between different sintering temperatures.

The analyses of raw materials from different deliveries were made and the deviation in particle size distribution for separate raw material was defined. The results were used as the basic data for all further research and a determination of the possibility to

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The particle size distribution of ceramic suspensions also depends on other factors, e.g., milling medium, which is tap water in our case, and additives, the percent of medium, milling particles, type and capacity of mill and others. Further investigations will be focused on a determination of a single factor of suspension influence on the characteristics of sintered cordierite materials. With the optimization of cordierite compositions and ceramic suspensions conditions the quality of cordierite materials will be improved. New cordierite materials will meet higher requirements of materials and products on the market as well as increase the products reliability.

Figure 6.7: Particle size analyser Cilas 920

change the cordierite compositions according to the particle size distribution of separate raw materials and thus to improve the cordierite material quality. The samples of existing raw materials will be prepared with different particle size distributions and new raw materials for further analyses of the particle size raw materials and other raw materials characteristics (e.g., chemical composition) influence on sintered material.

OBERŽAN, M., HOLC, J., BUH, M., KUŠČER, D., LAVRAČ, I., KOSEC, M.. High-alumina porcelain with the addition of a Li[sub]2O-bearing fluxing agent. J. Eur. Ceram. Soc.. [Print ed.], 2009, vol. 29, no. 11, 2143-2152 RAMŠAK, I., MIRTIČ, B., OBERŽAN, M., RAZPOTNIK, H., KUŠČER, D., KOSEC, M.. Dense cordierite ceramics. V: BELAVIČ, Darko (ur.), ŠORLI, Iztok (ur.). 48th International Conference on Microelectronics, Devices and Materials & theWorkshop on Ceramic Mycrosystems, September 19 September 21, 2012, Otočec, Slovenia. Proceedings. Ljubljana: MIDEM Society for Microelectronics, Electronic Components and Materials, 2012, 351356. OBERŽAN, M.. High-alumina porcelain with improved mechanical and thermal properties : doctoral dissertation = Visoko glinični porcelan z izboljšanimi mehanskimi in termičnimi lastnostmi : doktorska disertacija. Ljubljana: [M. Oberžan], 2009. X, 138. [18] RAMŠAK, I. Fazna sestava goste kordieritne keramike : diplomsko delo = Phase composition of dense cordierite ceramics. Ljubljana: [I. Ramšak], jan. 2012. XV, 85 f.

Particle size distribution of ceramic suspensions Flexural strength, coefficient of thermal expansion and resistance to thermal shock are significant characteristics of cordierite materials which depend on the particle size distribution of ceramic suspensions. Particle size analyser Cilas 920 was used for a determination of the particle size distribution of all types of cordierite suspensions. The analyses included numerous ceramic suspensions from different charges with different characteristics. The analyses of flexural strength, coefficient of thermal expansion and resistance to thermal shock were carried out on the same samples. The results were used to determine the influence of particle size distribution on ceramic suspensions on the characteristics of sintered cordierite materials.

Figure 6.8: Milling of cordierite suspensions in a production mill with capacity of 5.000 kg

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VIRTUAL LABORATORY FOR MEASUREMENTS OF ELECTROMAGNETIC COMPATIBILITY

Virtual laboratory for measurements of electromagnetic compatibility (EMC)

Jožef Perne 1986: Graduated at the Faculty for Electrical Engineering, Computer Science and Informatics at the University of Maribor where his main field of study was automatics. 1971: Employed at the factory Iskraemeco d.d. starting as a developer, project manager and a head of the department

CoE and even further on individual projects. Demands for electromagnetic compatibility and demands for resistance, roughness and safety are those that need to be taken into consideration across the whole chain.

The virtual EMC laboratory project has two basis: Resolution of research and innovation strategies RS 2011 – 2010 (confirmed by the parliament of RS, strategic government documents “Družba Znanja Slovenija” March 2011) predicts development of the national research infrastructure. This means the forming of virtual centers which would provide access to the research infrastructure. The second is a strategic goal CoE NAMASTE which defines the vertical connection of materials with elements and products on the level of

The objective is to build a database of all the leading laboratories in the field of EMC and safety in Slovenia. This database will provide information for potential users about the measurements in the laboratories. The database would provide relevant information about availability and usage of the equipment, measurement procedures and qualifications for

1989: Director for Research and Development in the factory Iskraemeco d.d. From 2005: Director of a Technological Centre for Circuits, Components, Materials, Technologies and Electronic Equipment called TC SEMTO. From 2009: Owner of a company Pentera d.o.o., - company for innovation, development, research and consultancy Most important work: PERNE, J., ŠIFKOVIČ, J., ŠPAROVEC, L., VRBICA, M.. Ohišje števca za merjenje električne energije : model : registrska številka 200250039. Ljubljana: Urad Republike Slovenije za intelektualno lastnino, 2002.

Figure 6.9: EMC measurements

ROZMAN, M., PERNE, J., STRLE, V., BIZJAK, U., KOSMAČ, M.. Integrirano vezje, predvideno za merilnik električne energije : patent številka SI 21580 A. Ljubljana: Urad Republike Slovenije za intelektualno lastnino, 2005. PERNE, J.. Predgovor. V: BIZJAK, M. (ur.), BIZJAK, M., BRECELJ, F., JELIĆ, N., NEMANIČ, V., PIRIH, A., PREGELJ, A., ROZMAN, R., ŠTAGOJ, A., ZAJEC, B.. Plinski odvodnik za zaščito pred prenapetostjo pri udarih strele. Ljubljana: Zavod Tehnološki center SEMTO, 2010, str. V-VI.

Figure 6.10: Testing laboratory

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The reason for this project is mainly the need for interconnection. Knowledge in the field of EMC and safety is very specific but it is needed for the research and development of very distinctive materials, elements and products. Equipment for measurements and tests is very expensive and very specific for certain tests. Procedures for measurement and testing are defined by standards. They declare the necessary equipment and volume grade of procedures. In the laboratory this needs to be upgraded with precisely defined measurement procedures, traceability of measurement and test instruments and above all with experiences for finding solutions to the problems.

Figure 6.11 Example of tested system

performing measurements. database will include data about:

The

Standards

Regulations

Measurement and test equipment and its availability

Predefined measurement testing procedures

Knowledge and personnel dedicated for measurements and solving the developer problems

Concluded solutions in the field of EMC resistance, resistance on stress tests and safety tests

The next stage of the project is developing solutions in the electronics companies and the on-time implementation of EMC solutions in prototype phase of product design. Direct results are shown in decreased research time for new elements, parts or products and a cost decrease for measurements and tests.

and

Figure 6.12 EMC consortium

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POMPE, I., PERNE, J.. Posvet o zanesljivosti, elektromagnetni združljivosti in trajnostni dobi elektronskih sklopov in komponent, 56.6.2007, Univerza v Ljubljani, Fakultetaza elektrotehniko, Ljubljana. 2007. [COBISS.SI-ID 20839207] PERNE, J.. Konferenca o zanesljivosti, elektromagnetni združljivosti in trajnostni dobi elektronskih sklopov in komponent, 2009, Univerza v Ljubljani, Fakulteta za elektrotehniko, Ljubljana 2009. PERNE, J.. Konferenca o zanesljivosti, elektromagnetni združljivosti in trajnostni dobi elektronskih sklopov in komponent, 2011, Univerza v Ljubljani, Fakulteta za elektrotehniko, Ljubljana 2011. PERNE, J.. Inovacijski proces kot nosilni proces v industrijskem podjetju : predstavljeno na delavnici Inovacije in podjetništvo za inženirje MR, 13. september 2011, Ljubljana, Slovenija. 2011. PERNE, J., BIZJAK, M.. Vzroki prenapetostnih motenj in zaščita pred njimi : 10. konferenca slovenskih elektroenergetikov CIGRE-CIRED, 30. maj - 1. junij 2011, Ljubljana, SLovenija. 2011.


ELECTROCALORIC MATERIALS

The electrocaloric effect (ECE) is described as a reversible temperature change of a material under an applied electric field due to the induced change of dipolar states. In other words, the material heats up or cools down due to an increase or decrease of the applied electric field, respectively. Hana Uršič Nemevšek 2005: Graduate in physics (Faculty of Mathematics and Physics, University of Ljubljana, Slovenia) with a thesis: Optical holographic gratings on the base of polymers and liquid crystals 2005–2010: Employed at Jožef Stefan Institute as a young researcher

Figure 6.14: Laboratories for processing of electrocaloric bulk ceramic materials (top) and for electrocaloric measurements (bottom).

2010: Ph. D. in nanoscience and nanotechnologies (Jožef Stefan International Postgraduate School) with a thesis: Structural and electrical properties of 0.65PMN-0.35PT thick films on different substrates 2010–2011: Postdoctoral associate at Instituto de Ciencia de Materials de Madrid, Madrid, Spain 2011: Researcher at Institute Jožef Stefan, Electronic Ceramics Department and CoE NAMASTE Most important work: URŠIČ, H., HROVAT, M., HOLC, D., ZARNIK, M. S., DRNOVŠEK, S., MAČEK, S., KOSEC, M., A large-displacement 65Pb(Mg1/3Nb2/3)O3–35PbTiO3/Pt bimorph actuator prepared by screen printing, Sensor Actuat B-Chem., vol. 133, 699–704 (2008). URŠIČ, H., SANTO ZARNIK, M., TELLIER, J., HROVAT, M., HOLC, J., KOSEC, M., The influence of thermal stresses on the phase composition of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 thick films, J. Appl. Phys., vol. 109, 014101 1–5 (2011). URŠIČ, H., TELLIER, J., HOLC, J., DRNOVŠEK, S., KOSEC, M., Structural and electrical properties of 0.57PSN– 0.43PT ceramics prepared by mechanochemical synthesis and sintered at low temperature, J. Eur. Ceram. Soc., vol. 32, pp. 449–456 (2012). [Print ed.], 2012, vol. 50, no. 3, 1170-1178. (2010) 4.893.

magnetocaloric effect is greatly reduced, especially so in microelectronics. On the other hand, high electric fields are much easier to generate and manipulate, making electrocaloric devices more attractive for broad-range miniaturized applications. In addition, refrigeration based on ECE has a potential to reach high efficiency, even when compared to the vapour-compression cycle systems, with one major advantage: green-house emissions can be completely avoided.

Figure 6.13: Scheme of electrocaloric cooling cycle in comparison with compressor cooling cycle.

The ECE is of great importance for application in cooling and heating devices of a new generation, which would be friendlier for the environment and would contribute to a reduction of power consumption. There are two other competitive technologies, which are also based on physical properties of materials. The first one is based on the thermoelectric Peltier effect. However, these devices require high DC-currents, which results in a waste of heat due to Joule heating. Therefore, the thermoelectric cooling devices have rather low efficiencies. The counterpart of the ECE is the magnetocaloric effect, where large magnetic fields are usually required for their effective operation, which severely limits miniaturization possibilities. Thus, wide usage of the

Until recently, only a small amount of electrocaloric data was obtained by a direct measurement of the temperature change of an electrocaloric material. The majority of published data were obtained by indirect measurements. In the frame of this project, reliable direct measurements of the electrocaloric temperature changes in various ceramic materials are performed by Prof. Zdravko

Figure 6.15: PMN–PT ceramics (a) microstructure and photograph of ceramic with electrical contacts and (b) the temperature change of ceramic vs. applied electric field.

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Kutnjak, Dr. Brigita Rožič and coworkers from CoE NAMASTE and Condensed Matter Physics Dep., Jožef Stefan Institute, Slovenia.

processing of electrocaloric materials and wide possibilities for further improvements in their performance. Utilization of the electrocaloric materials in application is still at an

LU, S. G., ROŽIČ, B., ZHANG Q,. M., KUTNJAK, Z., LI, X., FURMAN, E., GORNY, L. J., LIN, M., MALIČ, B., KOSEC, M., BLINC, R., and PIRC, R. Organic and inorganic relaxor ferroelectrics with giant electrocaloric effect. Appl. Phys. Lett., vol. 97, 162904 (2010). ROŽIČ, B., MALIČ, B., URŠIČ, H., HOLC, J., KOSEC, M., NEESE, B., ZHANG, Q. M., and KUTNJAK, Z. Direct Measurements of the Giant Electrocaloric Effect in Soft and Solid Ferroelectric Materials. Ferroelectrics, vol. 405, 26-31 (2010). ROŽIČ, B., KOSEC, M., URŠIČ, H., HOLC, J., MALIČ, B., ZHANG, Q. M., BLINC, R., PIRC, R., KUTNJAK, Z., Influence of the critical point on the electrocaloric response of relaxor ferroelectrics. J. Appl. Phys., vol. 110, 064118 1–5 (2011).

Figure 6.16: PLZT 8/65/35 thin film on platinized silicon substrate (a) microstructure, (b) photograph of a sample with electrical contacts (c) temperature and (d) entropy change vs. applied electric field (Lu, Rožič et al. APL, 2010).

Processed and studied materials are lead-based relaxor and relaxorferroelectric materials, such as Pb(Mg0.33Nb0.66)O3, Pb(Mg0.33Nb0.66)O3– PbTiO3(PMN–PT),Pb1-3x/2Lax(Zr0.65Ti0.35) O3 and antiferroelectric materials for example PbZrO3. Here, in 0.9Pb(Mg0.33Nb0.66)O3–0.1PbTiO3 bulk ceramics the best ECE result of 3.5 K was obtained, exceeding any previous ECE value determined in bulk materials. In addition to lead-based materials, also environment-friendly lead-free materials are studied such as relaxorferroelectric (K0.5Na0.5)NbO3–SrTiO3 and antiferroelectric NaNbO3. The high resolution electrocaloric thermometry, dielectric spectroscopy and measurements of polarization are carried out on bulk ceramics, thick films (more than 1 m thick) and thin films (less than 1 m thick) in order to determine the magnitude of the ECE.

early stage of development. They can be exploited in various types of devices: coolers, temperature controllers, and electrical generators. One efficient way to prepare the structure with high electrocaloric characteristic is to employ the multilayer geometry. In this project, the electrocaloric PLZT multilayers are processed in cooperation with KEKON d.o.o. Žužemberk, Slovenia. In conclusion, the development of new electrocaloric materials may open possibilities for developing new cooling technologies as well as new opportunities and ideas for further applicative tasks in cooling and heating applications.

Relaxor ferroelectric thin films are known to possess the best electrocaloric characteristics. Probably the world’s highest ECE temperature change, as high as 40 K, was directly measured on the chemical-solutiondeposition-derived Pb0.88La0.08(Ti0.65 Zr0.35)O3 (PLZT 8/65/35) thin films, also studied in the framework of this project. The state of the art in the processing of electrocaloric materials is the development of new, effective functional materials and the investigation of innovative designed solutions. There are still a number of challenges to be faced in the

Figure 6.17: Microstructure and (inset) photograph of PLZT multilayers

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Equipment Organizational structure

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Appendices


APPENDIX 1 - ORGANIZATION

Marija Kosec, CoE Director 1970: graduate in Chemical Technology (University of Ljubljana, Slovenia) 1982: PhD in Chemistry (University of Ljubljana) From 1971: employed at the Jožef Stefan Institute 1979-1980: on leave with the Institute für Gesteinshüttenkunde der RWTH Aachen, Aachen as a PhD student 1993: on leave with the Ecole Polytechnique Federale de Lausanne, Department des Materiaux, Laboratoire de Ceramique as a visiting professor From 1997: Head of Electronic Ceramics Department at the Jožef Stefan Institute From 1999: Professor for Material Science (University of Ljubljana, Faculty of Natural Sciences and Engineering) From 2004: Professor at the Jožef Stefan Post Graduate School From 2009: CoE NAMASTE Director Professional Recognition: 2003: Ambassador of Science of the Republic of Slovenia 2006: Zois Price for extraordinary achievements in science 2009: Puh Price for the implementation of research results in industry 2010: IEEE UFCC Ferroelectric Recognition Award for significant contributions to the processing science and technology of ferroelectric powders, bulk ceramics, thin and thick films

Organizational structure Prof. Dr. Marija Kosec, the Scientific Director of the CoE, is a person of outstanding scientific reputation with a rich experience in project organisation and administration on the national and international scales. She is assisted by the Managing Director, Dr. Alenka Rožaj Brvar, who also has, due to her work experience in research and management in industrial environments, excellent competence and high efficiency in running the administration of this CoE. The CoE council, formed by the highest-level representatives of the research institutions, the Ministry of Higher Education, Science and Technology, and industrial partners further ensures that the strategic direction of the CoE is in agreement both with the work plan, but also with the larger aims of the EU Cohesion Policy. Research Projects The research in the Centre is conducted within six projects. The results of our common activities are well acknowledged in the international environment, since the members of the CoE have so far produced in collaboration with their partners some major breakthroughs in the scientific and innovation fields, represented by numerous scientific papers, patents, patent applications, innovations, prototypes and demonstration projects. Some exceptional results, such as the large aspect ratio of the dimensions of a buried cavity, which

will make possible the fabrication of highly sensitive ceramic membranes, developed by the partners in the Project RRP1 - Ceramic 2D and 3D structures. The Project RRP2 Materials for overvoltage and EM protection is aimed at new developments in materials for lowdoped ZnO varistors for high-voltage protection and prototypes for electromagnetic radiation protection. The partners in the Project RRP3 - Materials, micro- and nano-systems for sensors are “world champions” in THz field detection. As a result of the co-financing of CoE NAMASTE the Ti microbolometer has been designed and manufactured as a crucial building block for a surveillance system designed for THz radiation monitoring. Radiation in the THz range (between the micro and millimetre ranges) is not invasive for living organisms. It penetrates fabric and other shielding materials; therefore, it can be employed in all spectra that are applied for the protection of people and cargo. Several major breakthroughs (published in the most prestigious journals) were noted in the project RRP4 - Soft composites for optical, electronic, photonic, and sensor applications. They were first in the world to create a 3D microlaser. When the paper, describing the structure and properties of this novel 3D microlaser was published in Optics Express, the Optical Society of America (OSA), which is the world's most important optical society, published a press release on

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December 8, 2010, describing the significance and importance of this work. According to OSA, this press release has reached more than 35 million readers across the world. The key word “First 3D microlaser” now has more than 250,000 Google hits.

the industrial partners. Yet it provides for the essential upgrade of existing equipment or establishing and implementing new top R&D equipment, since it makes it possible to maintain research and technological excellence to achieve more, to develop top expertise with the instrumentation and techniques. And that was also one of the important reasons that we were able to attract 16 non-academic partners into our operation. The collaboration in the CoE helps partners to solve specific problems – the CoE is creating the opportunity to do something more and something extra.

The project RRP4 - Soft composites for optical, electronic, photonic, and sensor applications is the leader in studying phenomena in chiral nematic liquid crystals. Fluorescence microspectroscopy – developing new methods for investigating the interaction between nanomaterials and living cells – is one of the important themes of Project RRP5 - Bioactive, biocompatible and bioinert materials.

Furthermore, as a result of the CoE, even the collaboration between industrial partners is gaining a new dimension. The instrumentation that has been acquired with the grant for this CoE has significantly improved the available measurement, testing / characterisation and production infrastructure. It appears that techniques and instruments that provide structural and chemical analysis would also be important to perform the individual tasks.

The continuously growing number of new discoveries in the field of nanomaterials opened one striking new dilemma - how safe are these systems when we do not control their location and they diffuse into our environment? Sooner or later they enter our bodies. But how do they interact with our cells? According to the properties of their macroscopic analogue materials, they should be more or less inert. But are they really inert?

It is also important to emphasize that the instrumentation is located at the sites where both the technical infrastructure as well as the expertise are available to run these instruments. This enables the best performance, may it be at the research institutes or with various industrial partners.

The Project RRP6 - Project of new opportunities, allows the inclusion of new partners. The partners in the Project RRP6 explore the preparation of ceramic electrocaloric materials (volume ceramic, thick and thin layers of lead-based ceramic, as well as environmentally friendly ceramic materials). The world’s highest ECE temperature change, as high as 40 K, was directly measured on the Pb0.88La0.08(Ti0.65Zr0.35)O3 thin films.

Publications and patents The technological excellence of CoE NAMASTE is demonstrated by the number of innovations and patents achieved so far, as well as by the number of prototypes and demonstration projects. The number of publications is remarkable, and so is the rank of the journals which have been chosen for publication, including Proc. Nat. Acad. Sci. USA, Nature Comm., Phys. Rev. Lett., or Chem. Comm. In addition to that, CoE partners are participating or coordinating several international projects, which indicates the strong international relations of CoE NAMASTE.

Equipment One of the main goals of our operation is to work in interdisciplinary teams, share and transfer the knowledge, and learn from each other. The funding of the CoE represents a small fraction of the total needed financing for the research in the areas where the academic and research partners have traditionally co-operated with

Research Projects in the Centre:  RRP1: Ceramic 2D and 3D structures (dr. H. Uršič),

Cross-section of Pressure Sensor

the

Ceramic

 RRP2: Materials for overvoltage and EM protection (assist. prof. dr. S. Bernik)

High coercivity bonded magnets for automotive applications  RRP3: Materials, micro- and nanosystems for sensors (prof. dr. J.Trontelj)

THz Sensor System (300GHz – λ=1mm)  RRP4: Soft composites for optical, electronic, photonic and sensor applications (prof. dr. S. Žumer)

Word`s first micolaser emitting in 3D Cholesteric liquid crystal microdroplets  RRP5: Bioactive, biocompatible and bioinert materials (prof. dr. J. Štrancar)

New methods for tracking nanoparticles in living cells  RRP6: Project of new opportunities, which allows the inclusion of new partners (assist. prof. dr. D. Kuščer).

The world’s highest ECE temperature change, was directly measured on the Pb0.88La0.08(Ti0.65Zr0.35)O3 thin films.

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APPENDIX 2 - EQUIPMENT RRP1 Cutting saw for ceramics (RRP1O1/1) Responsible person: dr. Hana Uršič Nemevšek (hana.ursic@ijs.si) Location: JSI Producer: Buehler, Isomet 5000

Furnace for firing LTCC ceramic (RRP1- O2) Responsible person: dr. Hana Uršič Nemevšek (hana.ursic@ijs.si) Location: HYB d.o.o., Šentjernej Type: ATV PEO 603

Manual press 3T (RRP1 O1/2) Responsible person: dr. Hana Uršič Nemevšek (hana.ursic@ijs.si) Location: JSI

Rheometer (RRP1- O3) Responsible person: dr. Hana Uršič Nemevšek (hana.ursic@ijs.si) Location: JSI Type: Physica MCR 301

Pressure calibrator (RRP1 O1/3) Responsible person: dr. Hana Uršič Nemevšek (hana.ursic@ijs.si) Location: JSI

Optical tensiometer (RRP1-O3/2) Responsible person: dr. Hana Uršič Nemevšek (hana.ursic@ijs.si) Location: JSI Type: Krüss GmbH, EasyDrop DSA20E

Laboratory mill (RRP1-O1/4) Responsible person: Boris Jordan (boris.jordan@kekon.com) Location: KEKON, d.o.o., Žužemberk Producer: Bühler AG

Thermal Analysis (RRP1 –O3/3) Responsible person: dr. Hana Uršič Nemevšek (hana.ursic@ijs.si) Location: JSI Type: Netzsch, STA 409 PC Luxx

Laser cutting saw system (RRP1 O1/5) Responsible person: Mitja Jerlah (mitja.jerlah@ijs.si) Location: JSI Producer: LPKF Laser & Elektronika d.o.o.

Automatic Gas Pycnometer (RRP1-O4/3) Responsible person: dr. Hana Uršič Nemevšek (hana.ursic@ijs.si) Location: JSI-K5 Type: Micromeritics, Accu Pyc 1340 10cc

Temperature and climatic test system (RRP1- O1/6) Responsible person: Mitja Jerlah (mitja.jerlah@ijs.si) Location: JSI Type: Vötsch Industrietechnik, VCL 7003

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RRP2 Microwave-radiation furnace for synthesis and sintering (RRP2 –O1) Responsible person: asist. dr.Slavko Bernik (slavko.bernik@ijs.si) Location: JSI Type: Carbolite, MRF 16/22

Power source (RRP2-O8/1) Responsible person: mag. Andrej Pirih (andrej.pirih@varsi.si) Location: VARSI d.o.o.

Instrument for particle size analysis and Zeta meter (RRP2 –O4-O6) Responsible person: asist. dr.Irena Ban (irena.ban@uni-mb.si) Location: UNI MB-FKKT Type: Malvern Instruments, Nano ZEN3600

Temperature chamber (RRP2-O8/2) Responsible person: mag. Andrej Pirih (andrej.pirih@varsi.si) Location: VARSI d.o.o. Producer: HERAEUS VOTSCH

Ultrasonic processor (RRP2 –O4-O6/2) Responsible person: asist. dr.Irena Ban (irena.ban@uni-mb.si) Location: UNI MB-FKKT

Oscilloscope (RRP2-O8/3) Responsible person: mag. Andrej Pirih (andrej.pirih@varsi.si) Location: VARSI d.o.o. Type: Tektronix, DPO3012

Ultrasonic cleaner (RRP2 –O4-O6/3) Responsible person: asist. dr.Irena Ban (irena.ban@uni-mb.si) Location: UNI MB-FKKT Type: Iskra Pio, Sonis 10 GT

Thermal camera (RRP2-O8/4) Responsible person: mag. Andrej Pirih (andrej.pirih@varsi.si) Location: VARSI d.o.o. Type: Fluke, TI40-20/7,5

Centrifuge (RRP2 –O5) Responsible person: asist. dr.Irena Ban (irena.ban@uni-mb.si) Location: UNI MB-FKKT Type: Eppendorf, 5804 R

Moisture meter (RRP2-O8/6) Responsible person: mag. Andrej Pirih (andrej.pirih@varsi.si) Location: VARSI d.o.o. Type: Mettler Toledo, HB43-S

System for thermal analysis with the mass spektrometer (RRP2 –O7) Responsible person: dr. Branka Mušič (Branka.Mušič@kolektor.com) Location: Nanotesla Institute Type: SN5131222299

High Current Impulse Generator (RRP2- O8/7) Responsible person: mag. Andrej Pirih (andrej.pirih@varsi.si) Location: VARSI d.o.o., Ljubljana Type: HILO-TEST Gmbh, PG 2014000

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Pearson Current monitor (RRP2-O8/8) Responsible person: mag. Andrej Pirih (andrej.pirih@varsi.si) Location: VARSI d.o.o., Ljubljana Type: 1423 Producer: Nucletron Technologies GmbH

Optical non-contact measuring system (RRP2- O9) Responsible person: Mojca Balon (mojca.balon@kolektor.com) Location: Kolektor Magma d.o.o., Ljubljana Model: TESA VISIO, V-300 GL DCC

Laboratory manuel press (RRP2-O10) Responsible person: dr. Branka Mušič (Branka.Music@kolektor.com) Location: Nanotesla institute, Ljubljana Type: Testchem, LPR 250e

RRP3 Confocal microscope (RRP3-O2) Responsible person: dr. Marijan Maček (marijan.macek@fe.uni-lj.si) Location: UNI LJ-FE Type: Olimpus, LEXT 3100

Dry plasma etching with turbo pump (RRP3-O3/1 and RRP3-O3/2 ) Responsible person: prof. dr. Slavko Amon (slavko.amon@fe.uni-lj.si) Location: UNI LJ-FE Type: OXFORD Instruments, Plasmalab System 100-ICP180

Wafer bonder (RRP3-O2) Responsible person: dr. Marijan Maček (marijan.macek@fe.uni-lj.si) Location: UNI LJ-FE

RRP4 Optical tweezers and other optical components (RRP4-O1) Responsible person: prof. dr. Igor Muševič (igor.musevic@ijs.si) Location: JSI Type: Tweez 200si

NMR Diffusion Probe (RRP4-O4) Responsible person: prof. dr. Boštjan Zalar (bostjan.zalar@ijs.si) Location: JSI

3D Laser Litography System Photonic Professional (RRP4 –O2) Responsible person: prof. dr. Igor Muševič (igor.musevic@ijs.si) Location: JSI-C023 Producer: Nanoscribe GmbH, Germany

Chiller with pump (RRP4-O5/2) (RRP4-O5/1) Responsible person: dr. Janez Pirš (janez.pirs@ijs.si) Location: JSI Type: Grundfos, CRIE 1-7

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Computer simulation group (RRP4 –O3, RRP4-O3/2, RRP4-O3/4) Responsible person: prof. dr. Slobodan Žumer (slobodan.zumer@fmf.uni-lj.si) Location: UNI LJ-FMF Type: AVALON, Supermicro server 8016B-TF-N, 8026B-TRF-N, 8026-BTRF

Kelvin probe (RRP4-O6) Responsible person: prof. dr. Maja Remškar (maja.remskar@ijs.si) Location: JSI Type: 7280 DSP

Low pressure Impactor (RRP4-O7) Responsible person: prof. dr. Maja Remškar (maja.remskar@ijs.si) Location: Reactor Centre JSI Producer: Dekati

RRP5 Nanoparticles counter (RRP4-O6) Responsible person: Ivan Iskra (ivan.iskra@ijs.si) Location: JSI Type: TSI Inc., SMPS 3936L85

Air sampler (RRP5-O4) Responsible person: prof. dr. Martin Dobeic (martin.dobeic@vf.uni-lj.si) Location: UNI LJ-VF Producer: CORIOLIS DELTA

Analytical scale (RRP5-O2/1) Responsible person: prof. dr. Damjana Drobne (damjana.drobne@bf.uni-lj.si) Location: UNI LJ-BF Type: KERN, ABT 100-5M

Surfometer (RRP5-O5/2) Responsible person: Dr. Aleš Dakskobler (ales.dakskobler@ijs.si) Location: JSI Type: NOVA 2200E

The inverted microscope and Equipment for Fluorescence microscope (RRP5-O2/3, RRP5O2/4) Responsible person: prof. dr. Damjana Drobne (damjana.drobne@bf.uni-lj.si) Location: UNI LJ-BF Type: Carl Zeiss, Axio Vert A1

Digestorium (RRP5-O5/3) Responsible person: dr. Aleš Dakskobler (ales.dakskobler@ijs.si) Location: JSI – K605 Type: Hohenloher, 7174

Digestorium (225 cm high) (RRP5-O5/3) Responsible person: dr. Polona Umek (polona.umek@ijs.si) Location: JSI – K605 Producer: Köttermann

Spin processor (RRP5-O8) Responsible person: prof. Maja Remškar (maja.remskar@ijs.si) Location: JSI Type: Laurell Technologies Corporation, WS-650Mz-23NPP

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CO2 incubator (RRP5-O2/5) Responsible person: prof. dr. Damjana Drobne (damjana.drobne@bf.uni-lj.si) Location: UNI LJ-BF Type: Memmert, INCO-153

Thermal imager (RRP5-O10) Responsible person: dr. Štefan Pintarič (stefan.pintaric@vf.unilj.si) Location: UNI LJ-VF Type: TESTO AG, 881-2

Laminar flow chamber (RRP5-O2/5) Responsible person: Prof. Dr. Damjana Drobne (damjana.drobne@bf.uni-lj.si) Location: UNI LJ-BF Type: Iskra Pio, MC 12-1

Automated Inoculation System (RRP5-O11) Responsible person: dr. Irena Zdovc (irena.zdovc@vf.uni-lj.si) Location: UNI LJ-VF Type: TREK Diagnostic Systems, Inc., SENSITITRE AIM

RRP6 Zeta Potential Analyzer and Particle Size Option (RRP6-O2, RRP6-O2/2) Responsible person: assist. dr. Danjela Kuščer (danjela.kuscer@ijs.si) Location: JSI Type: Brookhaven Instruments, ZetaPlus

Laser based granulometer (RRP6-O1) Responsible person: mag. Mitja Koprivšek (mitja.koprivsek@eti.si) Location: ETI, Izlake Type: CILAS, ECOSIZER

RRSK SPS (RRSK-O1) Responsible person: prof. dr. Tomaž Kosmač (tomaz.kosmac@ijs.si) Location: JSI Producer: SPS Syntex inc.

With optical tweezers upgraded system for confocal fluorescent microspectroskopy (RRSK-O6) Responsible person: prof. dr. Janez Štrancar (janez.strancar@ijs.si) Location: JSI

Sample Holder for JEM 2100 HR (RRSK-O2/1) Responsible person: asist. dr. Andreja Benčan Golob (andreja.bencan@ijs.si) Location: JSI Type: Gatan, Inc., 677 JEOL

Dilatometer (RRSK-O7/1) Responsible person: dr. Hana Uršič Nemevšek (hana.ursic@ijs.si) Location: JSI Type: NETZSCH, DIL 402 CD/4

Thermal imaging microscope (RRSK-O3) Responsible person: prof. dr. Janez Trontelj (janez.trontelj1@guest.arnes.si) Location: UNI LJ-FE Type: FLUKE, SC5600

Contactless dilatometer (RRSK-O7/2) Responsible person: dr. Hana Uršič Nemevšek (hana.ursic@ijs.si) Location: JSI Type: MISURA

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Scanning Near-field Optical Microscope System (RRSK-O4) Responsible person: Prof. Maja Remškar (maja.remskar@ijs.si) Location: Reactor Centre JSI Type: WITec, Alpha 300RS

Atomic force microscope and The BioHeater (RRSK-O8, RRSK-O8/2) Responsible person: assist. dr. Andreja Benčan Golob (andreja.bencan@ijs.si) Location: JSI Microscope Type: ASYLUM RESEARCH, MFP-3D Heater type: ASYLUM RESEARCH, HTR-BIOHEAT Dark field detector (RRSK-O10) Responsible person: assist. dr. Andreja Benčan Golob (andreja.bencan@ijs.si) Location: JSI Type: HAADF

Backscattered electron detector (RRSK-O9) Responsible person: assist. dr. Andreja Benčan Golob (andreja.bencan@ijs.si) Location: JSI

CCD camera (RRSK-O11) Responsible person: assist. dr. Andreja Benčan Golob (andreja.bencan@ijs.si) Location: JSI Producer: GATAN

Correlation microscope (RRSK-O12) Responsible person: dr. Klementina Zupanc (Klementina.Zupan@fkkt.uni-lj.si) Location: UNI LJ-FKKT Type: Carl Zeiss, LSM 700

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CENTER ODLIČNOSTI NAMASTE / Centre of Excellence NAMASTE  
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