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Volume 3 2019



Innovatieve Materialen (Innovative Materials) is a digital, independent magazine about material innovation in the fields of engineering, construction (buildings, infrastructure and industrial) and industrial design. A digital subscribtion in 2019 (6 editions) costs € 39,50 (excl. VAT) Members of KIVI and students: € 25,- (excl. VAT)

1 News 8 Urbach tower

The Institute for Computational Design and Construction (ICD) and the Institute of Building Structures and Structural Design at the University of Stuttgart developed the so-called Urbach Tower, a structure made of self-shaping wood. The design emerges from a new self-shaping process of the curved wood components. Components for the 14 m tall tower are designed and manufactured in a flat state and transform autonomously into the final, programmed curved shapes during industry-standard technical drying. This opens up new and unexpected architectural possibilities for high performance and elegant structures, using a sustainable, renewable, and locally sourced building material. The tower was built as a contribution the Remstal Gartenschau 2019.

12 Experimetal concrete 2018

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Innovative Materials platform: Dr. ir. Fred Veer, prof. Ir. Rob Nijsse (Glass & Transparency Research Group, TU Delft), dr. Bert van Haastrecht (M2I), prof. Wim Poelman, dr. Ton Hurkmans (MaterialDesign), Jos Brouwers, (Department of the Built Environment, Section Building Physics and Services TU Eindhoven), Jilt Sietsma, (4TU.HTM/ Mechanical, Maritime and Materials Engineering (3mE), prof.dr. Pim Groen, (SMART Materials Aerospace Engineering (AE) TU Delft/Holst Centre, TNO), Kris Binon (Flam3D), Guido Verhoeven (Bond voor Materialenkennis/SIM Flanders, Prof. Dr. ir. Christian Louter Institut für Baukonstruktion Technische Universität Dresden).

For a number of years, the ‘Experimental Concrete’ inspiration project has been organized, aimed at pushing the boundaries of the material use and performance. The project started in 2003 as an initiative of the Cement&BetonCentrum and now falls under the responsibility of the Betonhuis Constructief Prefab. Through the years, the basic idea remained and led to an impressive number of out of the box concepts. Instead of being gray, dull and functional, concrete is understood as playful, innovative and groundbreaking (Innovative Materials number 1 2018). Every year the results of the workshops are presented; those of 2018 during the Bouwbeurs, February this year. At the end of April, an Inspiration book was published, completing the Experimental Concrete 2018 project.

18 Thin ´Smartphone Glass´ as Façade Glazing

The research undertaken in the field of novel thin glass applications in the building industry shows promising results. Thin glass can be applied as an adaptive façade glazing system, thereby providing appealing glazing solutions which can change their shape in function of external parameters. Moreover, thin glass in combination with 3D-printed polymer cores offer strong and stiff yet very lightweight composite façade glazing panels with an appealing appearance. Benefit of such panels is their ease of installation, reduction in transport energy and possibilities for sun-shading and daylighting control within the design of the 3D-printed core. Further studies are currently being developed as a collaborative effort between TU Delft, TU Dresden and industry partners.

24 Structure and Function for Designer Polymers

Polymers are essential building blocks of both biological life and artificial everyday objects. Every polymer molecule consists of long chains of repeating units (mers) linked together either linearly or within a complex architecture. Building blocks may be nucleotides in DNA, aminoacids in proteins, or petroleum-based small molecules, such as ethylene, propylene or styrene in the case of synthetic polymers. Herman Staudinger proposed almost exactly hundred years ago, that polymers are covalently bonded chain-like molecules. To celebrate this discovery the year 2020 has been named the year of polymer science.

30 Smart Materials, Part 3: Piezoelectric constitutive equations

Smart materials are everywhere, but often invisible or simply not recognized. This is the second article in a series of eight, in which prof. Pim Groen will discuss the world of smart materials; this time piezoelectric materials. Piezoelectricity is the electric charge that accumulates in certain solid materials in response to applied mechanical stress and vice versa.

34 Enterprise Europe Network (EEN) supports companies with international ambitions

Request for partnership; June 2019.



New polymer films conduct heat instead of trapping it Polymers are usually the go-to material for thermal insulation. Now MIT engineers developed thin polymer films that conduct heat; an ability normally associated with metals. In experiments, they found the films, which are thinner than plastic wrap, conduct heat better than ceramics and many metals, including steel. The team’s results, published in the journal Nature Communications, titled ‘Nanostructured polymer films with metal-like thermal conductivity’. According to MIT their work may spur the development of polymer insulators as lightweight, flexible, and corrosion-resistant alternatives to traditional metal heat conductors, for applications ranging from heat dissipating materials in lap-

tops and cellphones, to cooling elements in cars and refrigerators. The team was able to fabricate thin films of conducting polymer, starting with a commercial polyethylene powder. Normally, the microscopic structure of polyethylene and most polymers resembles a spaghetti-like tangle of molecular chains. Heat has a difficult time flowing through this jumbled mess, which explains a polymer’s intrinsic insulating properties. The team looked for ways to untangle polyethylene’s molecular knots, to form parallel chains along which heat can better conduct. To do this, they dissolved polyethylene powder in a solution that prompted the coiled chains to expand and untangle. A custom-built flow system further untangled the molecular

chains, and spit out the solution onto a liquid-nitrogen-cooled plate to form a thick film, which was then placed on a roll-to-roll drawing machine that heated and stretched the film until it was thinner than plastic wrap. The team then built an apparatus to test the film’s heat conduction. While most polymers conduct heat at around 0.1 to 0.5 watts per meter per Kelvin, they found the new polyethylene film measured around 60 watts per meter per Kelvin. More at MIT > The paper ‘Nanostructured polymer films with metal-like thermal conductivity’ is online>

By mixing polymer powder in solution to generate a film that they then stretched, MIT researchers have changed polyethylene’s microstructure, from spaghetti-like clumps of molecular chains (left), to straighter strands (right), allowing heat to conduct through the polymer, better than most metals



Concrete sewer components of the 3D printer

During the Hannover Messe 2019, the Bundesanstalt f端r Materialforschung und pr端fung (BAM) presented its research on manufacturing techniques for complex 3D-printed concrete elements. BAM believes that in the future these processes will make it possible to produce relatively quickly, cheaply and tailor-made components meant for, for example, sewer systems. The basic idea is that in the conventional production of concrete components, design options are limited by the relatively expensive formwork. If functional elements in the infrastructure have to


be replaced, for example due to damage, repair is often associated with high costs. In such cases, additive production processes can be used to produce cost-effective, customized concrete components in small series. Against this background, BAM and TU Clausthal are currently investigating the possibilities of 3D printing of alkali-activated concrete. At the BAM stand, during the Hannover Messe, a sixty-centimeter-sized cube with holes was shown, which was made with a 3D printer. The Bundesanstalt f端r Materialforschung und pr端fung is involved in the EU project

AMITIE (Additive Manufacturing Initiative for Transnational Innovation in Europe). As part of AMITIE, BAM scientists are working with Italian startup Desamanera on 3D printing of very large, complex components made of concrete.

More at>


Longest 3D-printed concrete pedestr an bridge in the world On 13 May, 3D printing of a bridge was started, which should become the longest concrete 3D-printed pedestrian bridge in the world. The project is a collaboration between Rijkswaterstaat (and the municipality of Eindhoven (clients), Eindhoven University of Technology as knowledge partner and BAM, Dywidag, Weber Beamix, Summum Engineering and Witteveen + Bos as market parties. Rijkswaterstaat wants to gain experience with the possibilities that 3D printing offers for sustainable and circular projects. Rijkswaterstaat is part of the Dutch Ministry of Infrastructure and Water Management and responsible for the design, construction, management and maintenance of the main infrastructure facilities in the Netherlands.

28.5 m and a width of 3.6 m and will be printed in parts. These parts are then assembled on site. The bridge will replace an outdated wooden bridge in the

Nijmegen Geologic Strip in the Zwanenveld district. More at RWS>

Together with designer Michiel van der Kley, a pedestrian bridge has been developed, which will be installed in Nijmegen in the summer of 2019. Rijkswaterstaat is responsible for the construction of the bridge. Research into the structural safety of the 3D-printed bridge is being conducted at TU Eindhoven. The execution of the bridge will start on Monday 25 March 2019. The pedestrian bridge has a span of




‘Rebuild Notre Dame by 3D printing its ashes’ Last april, the roof of the Notre Dame in Paris was destroyed in a fire. Since then, president Macron has promised to restore the building and millions of euros have already been donated to make that happen. But how? The estimate is that at least four hundred professionals must be trained to get the job done: master stone-cutters, woodworkers, quarrymen, roofers, sculptors and other craftsmen. In France the specialized labour simply isn’t available and it would take a decade to train a crew. And even so, if there is access to the best craftsmen; what about the materials? Notre Dame was built out of wood and stone. The oak wood comes from old forests that were cut in the 13th century. These forests do not exist in France anymore. The stone is a typical Parisian stone, a local material called Lutetian limestone, which was dug from now abandoned mines. Now the main old mine is underneath the 5th, 6th, 14th and 15th arrondissement. According to CONCR3DE founders Eric Geboers and Matteo Baldassari, even if


all the materials and craftsmanship were available, simply copying the building, pretending there never was a fire, would

be a historical forgery. In 2016 they founded CONCR3DE with the aim of providing a way to produce sustaina-

3D printed Le Stryge out of Parisian limestone and ash, in evening light (image by CONCR3DE)

NEWS ble and unique forms of architecture, construction, design and manufacturing, using inkjet 3D printing technology. Now, they want to take the remains of the Notre Dame and use them to build it up again. The stone would be reused, maintaining the soul of the building.

3D scan

Fortunately, the original design of the church has been preserved by a full 3D scan of the cathedral back in 2000. CONCR3DE wants to use this to rebuild the Notre Dame, by 3D printing it. By collecting the ash, dust and damaged stone, it could be turned into a 3D printable powder. The powder has the same colour as the yellowish grey of Parisian stone, mixed with the charred remains of the wood. Using the 3D scans, lost parts of the Notre Dame can be 3D printed.

According to Geboers and Baldassari it’s not just a dream. For the last couple of years the Rotterdam based company has been creating various stone 3D printing materials. For instance, they 3D printed Le Stryge, a famous demon originally created by Viollet Le Duc in the 19th century, and using a 3D scan and a material that was a combination of lime stone and ash.


In the same way they would like to rebuild the Notre Dame. A workflow can be created where rubble is crushed and mixed, directly 3D printed and then installed by the craftsmen and without need for new expensive and hard to find materials. According to CONCR3DE the Notre Dame would be able to reopen within several months.

‘We would like the Notre Dame to rise from its ashes like a phoenix,’ Geboers and Baldassari said, ‘The fire is now part of its long history. The building should show its layered history proudly, and show the world that it has conquered it. The fire can also be the future of Notre Dame.’ Text is based on an article by Eric Geboers and Matteo Baldassari. More about CONCR3DE an be found at>

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MAKE IT MATTER MAKE IT MATTER is compiled in collaboration with MaterialDistrict ( In this section new, and/or interesting developments and innovative materials are highlighted.

3D printed bioplastic structures Commissioned by fashion brand COS, architectural firm Mamou-Mani designed a large scale 3D printed architectural installation made from bioplastic, which was on display during Milan Design Week. Conifera, as the project is called, was created from seven hundred interlocking modular bricks, made from a mix of wood and bioplastic. The material is made from fully compostable resources. The bricks come in three different colours. The brown ones are made with wood, the white ones are coloured with pigment and the translucent ones are made from PLA in its purest form. More at MaterialDistrict>

Remake ceramics With ‘Remake ceramics’, Fabrique Publique reuses broken pieces of ceramics, and makes it a valuable resource for new products. The first tests with recycled ceramics were applied to a set of tableware called ‘Future history’. The plates contained between 5 and 10% of recycled material. In further research, tests with higher percentages of recycled content were carried out, as well as tests with smaller/bigger type of grains.

More at MaterialDistrict>

Fabric like brick facade Architectural firm Behet Bondzio Lin Architekten designed a brick façade that seems to move like fabric. It’s is designed for the building of the Association of the Northwest German Textile and Garment Industry. The architectural firm used seven different types of bricks in varying colours. In total, 74,000 custom-made clinkers have been used, each arranged beforehand in a computer programme to create the desired effect. The design won the Deutscher Ziegelpreis in 2019. More at MaterialDistrict>


MAKE IT MATTER Tiles with vulcanic ash In collaboration with design studio Formafantasma, Dzek developed a collection of tiles, glazed with volcanic ash. ExCinere, as the collection is called, is a range of tiles for both interior and exterior surfaces, from kitchen counters and bathroom floors to architectural façade cladding. The ExCinere project further explores the application of lava, a natural-occurring, self-generating and abundant material. According to the studios, the glazed tiles make full use of volcanic stone’s material properties. Dzek and Formafantasma presented the new collection at the Milan Design Week this year. More at MaterialDistrict>

Coffee polymer Coffee polymer is a material consisting of 30 percent coffee grounds and 70 other biobased raw materials. There are three versions available. The Espresso Polymer is a specially developed biobased material, fully made out of a natural raw material. The Cappuccino Polymer is fully biodegradable in natural circumstances in about one year. Stored under dry circumstances, it can be used for years. The Americano Polymer is, developed for single-use products. In about two months the material will biodegrade. More at MaterialDistrict>

Tower to collect potable water from the air Non-profit organization Warka Water designed a vertical structure made of simple materials like polyester mesh and bamboo to collect and harvest potable water from the air. The design is based on the fact that air always contains a certain amount of water vapour, no matter the local ambient temperatures and humidity conditions. The aim is to collect 40 to 80 litres (10 to 20 gallons) of drinking water every day. More at MaterialDistrict>

3D printed urban furniture barrier Designed by Joe Doucet and manufactured by Urbastyle, Rely is row of 3D printed concrete benches, attached to each other to double as a discreet protective barrier against terrorism with vehicles. The 3D printed concrete units, each weighing over one ton are attached to each other by steel rods. In the event of a vehicle driving into an pedestrianised area, either on purpose or by accident, the linking system would allow the benches to absorb the impact and stop the vehicle by slowly deforming. More at MaterialDistrict>



Self-shaping wood

Urbach tower

The Institute for Computational Design and Construction (ICD) and the Institute of Building Structures and Structural Design at the University of Stuttgart developed the so-called Urbach Tower, a structure made of self-shaping wood. The design emerges from a new self-shaping process of the curved wood components. Components for the 14 m tall tower are designed and manufactured in a flat state and transform autonomously into the final, programmed curved shapes during industry-standard technical drying. This opens up new and unexpected architectural possibilities for high performance and elegant structures, using a sustainable, renewable, and locally sourced building material. The tower was built as a contribution the Remstal Gartenschau 2019. In timber construction, moisture typically causes problems with cracking and deformation; hence, moisture changes and stress development must be carefully controlled. In contrast, in this project wood is programmed and arranged in a way to utilize this powerful, naturally occurring deformation to trigger a designed self-shaping behavior. This shape change is only driven by the wood’s characteristic shrinking during a decrease of moisture content. The curved Cross Laminated Timber (CLT) components for the tower’s structure are designed and produced as flat panels that deform autonomously into predic-


NEWS ted curved shapes when dried. The 5.0 m x 1.2 m spruce wood bilayers parts are manufactured with a high wood moisture content and dried in an industry standard technical drying process. When removed from the drying chamber the parts are precisely curved. The parts are overlapped and laminated together, forming larger curved CLT components with form stable geometry. Material specific computational mechanics models have been developed to both design, predict, and optimize the material arrangement required to produce different curvature types and radius.


The tower consists of twelve curved components, cantilevering fourteen metres upward, and sports a transparent roof. The curvature makes a lightweight and slender structure possible. Each of the parts is only 90 mm thick and has a protective layer of glue laminated larch wood and an inorganic coating that protects the wood against UV-radiation and fungi. The elements are connected by crossing screws. The Urbach Tower is one of sixteen stations designed for the Remstal Gartenschau 2019. The stations are small, permanent buildings that evoke the traditional white chapels distributed in the fields and vineyards along the scenic Rems Valley, Baden-Württemberg, Germany.

Project team ICD – Institute for Computational Design and Construction, University of Stuttgart Prof. Achim Menges, Dylan Wood ITKE – Institute of Building Structures and Structural Design, University of Stuttgart Prof. Jan Knippers, Lotte Aldinger, Simon Bechert In collaboration with the Laboratory of Cellulose and Wood Materials, Empa (Swiss Federal Laboratories for Materials Science and Technology), Switzerland & Wood Materials Science, ETH Zurich (Swiss Federal Institute of Technology Zurich), Switzerland; Blumer-Lehmann AG, Gossau, Switzerland

The project was supported by Gemeinde Urbach, Remstal Gartenschau 2019 GmbH, the University of Stuttgart, the Deutsche Bundesstiftung Umwelt DBU (German Federal Environmental Foundation) and the Swiss Innovation Agency InnoSuisse University Stuttgart> Remstal Gartenschau 2019>

Photography: ICD ITKE University of Stuttgart



FIBERBOTS FIBERBOTS is a digital fabrication platform, developed by the Mediated Matter group at the Massachusetts Institute of Technology Media Lab. The group is primarily concerned with fusing cooperative robotic manufacturing with abilities to generate highly sophisticated material architectures. The platform can enable design and digital fabrication of large-scale structures with high spatial resolution, by working in some kind of a swarm-like way of working. Some of nature’s most successful organisms collaborate in a swarm fashion. For instance, bees, ants and termites cooperate to rapidly build structures much larger than themselves. FIBERBOTS is a communicating swarm of robots designed to wind fiberglass filament around themselves to create high-strength tubular structures. These


NEWS structures can be built in parallel and interwoven to rapidly create architectural structures. The robots are mobile, using sensor feedback to control the length and curvature of each individual tube, working with advanced design protocols. The sixteen robots, including the design system to control them, were developed in-house and deployed to autonomously create a 4.5 m-tall structure. According to the Mediated Matter group, the project clearly demonstrates the potential of this enabling technology towards future collaborative robotic systems. According to MIT, this research seeks to depart from these uniaxial fabrication methods and develop fabrication units capable of being highly communicative while simultaneously depositing tailorable, multifunctional materials. Moreover, the researchers intend to demonstrate that this research framework is applicable across scales: from the micro-scale to the product scale and, uniquely, to the architectural scale. The FIBERBOTS project was developed

by the Mediated Matter group at the MIT Media Lab. Researchers include: Markus Kayser, Levi Cai, Christoph Bader, Sara Falcone, Nassia Inglessis, Barrak Darweesh, João Costa, and Prof. Neri Oxman (Founding Director).


Copper cladding Earlier this year has been payed attention to a striking renovation project by architect and designer Peter Ebner and friends ZT GmbH. The renovation took place at the ‘Freiherrliche von und zu Guttenberg`sche Hauptverwaltung GbR’ in Munich. The history of the building by architect Emanuel von Seidl begins with its construction in the Art Nouveau style in 1904. After World War II, the most-undamaged facade only needed minor cosmetic repairs, but the rest of the building was demolished and built up new again. There are horizontal historic elements at the level of the first floor which the architects wanted to continue into the interior to unify the inside of the building with its external history. A monolithic material - copper- was chosen. First the construction company built the form with plasterboards on a substructure for fireproofing. Then, 2 mm copper sheets were molded onto the forms. The result is a shiny, somewhat baroque interior, with an atmosphere and lighting that is changing by the reflective metal constantly during the day.>



Experimetal Concrete 2018 For a number of years, the ‘Experimental Concrete’ inspiration-project has been organized, aimed at pushing the boundaries of the material use and performance. The project started in 2003 as an initiative of the Cement&BetonCentrum and now falls under the responsibility of the Betonhuis Constructief Prefab. Through the years, the basic idea remained and led to an impressive number of out of the box concepts. Instead of being gray, dull and functional, concrete is understood as playful, innovative and groundbreaking (Innovative Materials number 1 2018). Every year the results of the workshops are presented; those of 2018 during the Bouwbeurs, February this year. At the end of April, an Inspiration book was published, completing the Experimental Concrete 2018 project. Experimental Concrete 2018 took place under the name ‘Adaptive formwork’. Various concepts were investigated, such as ‘B adaptive’, which combined three materials: concrete, glass and steel into a single sandwich element. The internal space is brought to an almost vacuum whereby a very high insulati-


on value is achieved. The internal pressure is adjustable from almost vacuum to normal air pressure. This means the correct insulation value can be obtained at any time of the day, in any season. (Idea & design: Egbert Boertien; prototype: Geelen Beton with Skaup architecture)


B adaptive: The internal space is brought to an almost vacuum whereby a very high insulation value is achieved


Typical of natural stone the ‘drawing’ or ‘veins’ making each panel different, while still clearly ‘family’ in terms of colour and structure. Experimental Concrete has searched for similar properties in concrete. This has been tested with production methods and blends that from their inherent nature make the desired patterns and textures. The results are therefore not aesthetically designed; only the production method is determined. (idea & design: Siebe Bakker & Patricia Hessing; prototype: Byldis)

Clay mold

Furthermore the use of clay as a mold material was explored. It appears clay has good properties for use as formwork. It is suitable for making ‘impossible’, ‘non-releasing’ forms and can be provided with a surface structure. After the concrete has hardened, the clay is still flexible and can be used again. Above: veined; below: clay mold


INNOVATIVE MATERIALS 3 2019 A second study has been focussing on scaling up the technique and the use of a three-axis cutter to process the clay. This technique has been used by designers for a long time in making one-to-one prototypes for the automotive industry. (Idea & design: Michael van Leeuwen; prototypes: Riboton & Geelen Beton; Verhoeven Timmerfabriek Nederland)


A good combination between latex (rubber) and concrete must be able to lead to flexible elements. The adhesion between the

Left: Latex; above and below: Double-double curved

two materials and the processability are essential. It has been found that, given the differences in ‘hardening time’, the simultaneous production of the concrete and the rubber elements didn’t work properly. A step-by-step process must therefore be followed. (Idea & design: Egbert Boertien, Patricia Hessing & Gabriel Korenhof; prototype: Westo Prefab Concrete Systems)

Double-double curved

With the prototype ‘Double-double curved’ was tested how the double curved shape of one panel can be used directly as a mold for the next panel. This creates a series of elements that will have a different form, in which the differences still clearly show similarity, so a balanced and varied total can be formed. (Idea & design: Mark Hemel & Arman Kayhan; prototype: Haitsma Beton with Verhoeven Timmerfabriek Nederland)

Stepless mold

Generally, to build a staircase, each production stage requires a separate mold. However, the differences between the treads are often very small. Adjustments to open positions


INNOVATIVE MATERIALS 3 2019 may sometimes also be necessary at the very last moment, when it appears during construction that other parts of the building show deviations from the design. In the context of Experimental Concrete, a mold system was developed that can be adjusted continuously. Thus, any desired step can be easily manufactured. It is also possible to produce ‘in stock’ elements that can be assembled ‘just in time’ for the then requested staircase. (Idea & design: Jos Roodbol & Cindy Vissering; prototype: HCI Betonindustrie)

Another project, Grow-crete, was intended to investigate the possibilities of growing vegetation on concrete and De-crete, started with the question ‘can we make concrete that crumbles after being exposed for a certain amount of time?’ The inspirational booklet Experimental Concrete 2018; Adaptive Forms (Betonhuis Constructief Prefab) was compiled under the editorial team of Siebe Bakker - bureau bakker - and is available online (pdf; in Dutch)>

Below: All-crete: De-crete

Stepless mold


In addition to the ‘Experimental Concrete project 2018’, an in-company session was held at the request of the MVRDV design agency. The emphasis was on material properties, focussed on multiple functions. For instance, soft and flexible concrete, still with structural assets. The idea was to develop a material that has simply everything. So it’s called ‘All-crete’. Various concepts have been investigated in this context, such as the incorporation of rubber balls or the connection of concrete balls with silicone and so called Flowcrete: a material that is moldable and soft enough to sit on; a project of MVRDV/Geelen Beton.



Photo: Ice911

Reflective glass beads could slow the retreat of Arctic sea ice At the beginning of May, the Geophysical Institute of the Fairbanks University of Alaska posted a article about the research by Leslie Field and her colleagues. Field is an inventor trained in chemical and electrical engineering (MIT and Berkeley) who lectures at Stanford University in California. She also is founder of the non-profit group Ice911.


Ice 911 started in 2007 focussing on the issue of melting sea ice by increasing the reflectiveness of the Arctic sea ice. The team began testing different materials to see which could best reflect the sun. Now, over ten years later, Field and her Ice911 team members have developed a possible solution.


RESEARCH The idea is to try to rebuild a natural system with the least possible intervention. To do so, Field and her Ice911 members propose a reflective ‘sand’ made of powdered glass microspheres be spread over sea ice. The powder is mainly silica in the form of hollow glass spheres, with an average diameter of 65 μm. The material is available commercially in large amounts, and the Ice911 members are testing it on a lake in Barrow, the northernmost town in Alaska. They saw it increases sea ice’s reflectivity and can slow its melting. According to the scien-

tists that principle could help slow the earth’s warming. Last year the team published an open-access paper showing results of birds and small fish eating it with no apparent problems. Last May Field presented the results at the University of Alaska Fairbanks in front of a dozen scientists who work on northern sea ice.

The article‘Increasing Arctic sea ice albedo using localized reversible geoengineering’ (DOI: 10.1029/2018EF000820) is online>

More at the Fairbanks University of Alaska> Video


3D printing of large-scale metal parts A novel additive manufacturing method developed by researchers at Oak Ridge National Laboratory could be a promising alternative for low-cost, high-quality production of large-scale metal parts with less material waste. Researchers printed thin metal walls using a closed-loop, feedback-controlled technique to provide uniform flat layers at a desired height. The system automatically regulates the printing process, creating stable properties within the metal deposit and producing a high-quality build throughout the part. Because these metal printed walls represent the basic building blocks of parts manufactured with big area additive manufacturing, they expect the same stable properties to hold for parts printed with complex geometries. The team’s results were published in Applied Sciences, titled ‘Correlation of Microstructure and Mechanical Properties of Metal Big Area Additive Manufacturing’. The article is online > Oak Ridge National Laboratory, >



Thin ´Smartphone Glass´ as Façade Glazing Research undertaken at TU Delft and TU Dresden in the field of novel thin glass applications in the building industry shows promising results. Thin glass can be applied as an adaptive façade glazing system, thereby providing appealing glazing solutions which can change their shape in function of external parameters. Moreover, thin glass in combination with 3D-printed polymer cores offer strong and stiff yet very lightweight composite façade glazing panels with an appealing appearance. Benefit of such panels is their ease of installation, reduction in transport energy and possibilities for sun-shading and daylighting control within the design of the 3D-printed core. Further studies are currently being developed.

Researchers and students at the TU Delft and the TU Dresden are exploring the possibilities for using very thin glass for architectural applications. The basic idea is to adopt thin glass that is normally applied on smartphones and apply it in the building industry. The benefit of this thin ‘smartphone glass’ is its small thickness of around 0.5 mm, its high strength


and its high flexibility. This provides the opportunity for the creation of very lightweight yet strong façade glazing. Compared to traditional glazing a significant weight reduction is thus obtained, which directly translates into easier installation and less transport energy. Also, due to its high flexibility, the glass can easily be bent at room temperature,

without the need for cost and energy intensive hot shaping techniques. This offers opportunities for an easy creation of architectural appealing curvatures and the creation of adaptive and flexible façade glazing. The research follows two distinct routes, which are explained in this article.


Figure 1: Concept design and mock-up of an adaptive thin glass façade (MSc thesis of Rafael Ribeiro Silveira, TU Delft)

Thin Glass Concepts for Adaptive Façade Glazing

The first route within the research is to take full benefit of the flexibility of the thin glass. This means that the thin glass is used for the creation of flexible façade glazing that can repetitively change its curvature depending on external parameters. For instance, when applied as a double-skin façade, the thin glass can bent open, so to create ventilation openings. Or by integrating photovoltaic (PV) elements in a laminated thin glass panels, the PV cells could obtain an optimized orientation towards the sun by adjusting the curvature of the glass.

This concept of adaptive façade glazing is explored in a series of MSc thesis projects. The main challenge concerns the actuation of the thin glass, so how to bend the thin glass in a façade glazing system. Regarding this issue, several options were explored. Firstly, in the MSc thesis of Rafael Silveira Ribeiro, the option of a linear mechanical actuation of thin glass is explored. By means of an linear chain drive actuator, the thin glass façade glazing is pushed outwards, so to create ventilation openings. The concept was successfully demonstrated in a 500x800 mm mockup, see Figure 1.

Secondly, the MSc thesis of Özhan Topcu includes a study on the water- and airtightness of such novel adaptive façade glazing systems in closed condition. Several concepts are explored, see Figure 2, such as a) providing a magnetic gasket around the thin glass panel, similarly to a refrigerator door, to seal the panel in closed condition, b) applying bi-directional tension to the glass panel to provide a tight closure of the panel, or c) providing a stretchable fabric around the parameter of the glass, which can deform and follow the movements of the bendable thin glass panel both in open and closed condition. Also a case-study

Figure 2: Water and airtightness concepts for adaptive thin glass façades (MSc thesis of Özhan Topcu, TU Delft)



Figure 3: Case-study design of an adaptive thin glass façade (MSc thesis Özhan Topcu, TU Delft)

design of an adaptive thin glass façade was made, see Figure 3. Thirdly, in the MSc thesis of Congrui Zha, the bending of thin glass by means of soft pneumatic actuators is explored. By means of inflating a series of (soft) rubber air chambers that are adhesively bonded on a thin glass panel, the panel bends, see Figure 4. Since the thin glazing is designed as an insulating glass

unit containing two glass sheets with an intermediate cavity, a special flexible edge spacer is applied which is able to follow the bending movement of the thin glass. Using this concept a 300x300 mm mock-up was successfully produced to demonstrate the principles. Finally, in the MSc thesis of Bahareh Miri, the bending of thin glass by means of Shape Memory Alloy (SMA) wires is

investigated, see Figure 5. The concept consists of a very thin (Ø = 0.55 mm) SMA wire which is placed in the cavity between two panes of 0.5 mm thick glass panels. By heating the wire with an electric current, the wire contracts, thereby pulls upwards and bends the thin glass façade panels. Again, this concept was successfully demonstrated in a 500x800 mm prototype, see Figure 5.

Figure 4: Design concept and mock-up of an bendable insulating thin glass façade panel with soft pneumatic actuators (MSc thesis of Congrui Zha, TU Delft)



Figure 5: Adaptive thin glass faรงade with shape memory allows wire actuation (MSc thesis of Bahareh Miri, TU Delft)

Thin Glass Composite Panels with 3D-Printed Cores

The second route within the research is to stiffen the thin glass panels by means of 3D-printed core materials. This results in very rigid yet very lightweight faรงade glazing panels, which offer a benefit in terms of easier installation and reduction in transport energy. Additionally, more lightweight glazing may potentially also result in a reduction of material use for the support framing and a reduction of the overall building weight. Moreover, the 3D-printed cores offer opportunities for sun-shading and daylighting control. This concept of thin glass composite panels with 3D-printed cores is investigated in a series of MSc thesis projects. The main focus of the projects is to optimize the shape of the 3D-printed polymer (PET-G) core for structural purposes. Additionally, studies focus on the thermal insulating performance of such composite panels. Firstly, the MSc thesis project of Michele Akilo (exchange student from University of Bologna) focuses on thin glass composite panels with 3D-printed open

cell pyramidal trussed cores or 3D-printed hypar-shaped cores, see Figure 6. The open-cell trussed core provides an

optically open structure, whereas the hypar-shaped core provides a translucent and textured appearance to the panels,

Figure 6: Composite thin glass panels with 3D-printed trussed (left) and hypar-shape (right) cores (MSc thesis of Michele Akilo, , TU Delft / University of Bologna))


RESEARCH To do so, a Voronoi pattern was applied of which the geometry was generated through topology optimization, see Figure 8. Also the effects of different support conditions on the shape of the 3D-printed core pattern was analysed. Thirdly, the work of Charbel Saleh focuses in more detail on the durability of the composite panels and especially the polymer core. By exposing the specimens for several weeks to UV-radiation by means of specialized equipment, the long-term effects of sun-exposure is simulated, see Figure 9. This results in somewhat more brittle response of the polymer core, but does not significantly endanger the structural performance of the composite panels. At the end of the thesis the possibilities of a curved thin glass panel composite panel was explored, see Figure 10. Figure 7: Composite thin glass panel with 3D-printed trussed core in a bending test (MSc thesis of Lorenzo Lazzaroni, TU Delft / University of Pisa))

see Figure 6. The structural performance of the thin glass panels with trussed shaped cores are further investigated in the MSc theses of Lorenzo Lazzaroni (exchange student from University of Pisa). A 710x360 mm prototype was successfully produced and tested, using

UV-curing acrylate adhesives for bonding the polymer core and the glass, see Figure 7.   Secondly, the work of Tim Neeskens focuses on a further structural optimization of the 3D-printed core pattern.

Fourthly, the work of Marina Guidi further investigated the possibilities of producing curved thin glass panels with 3D-printed core panels. In this work, thin glass panels are adhesively bonded to a trussed polymer which is 3D-printed in a curved shape. Doing so, the final curved composite panels are kept in shape by means of the 3D-printed core, see Figure 10.

Figure 8: Composite thin glass panels with 3D-printed voronoi patterns (MSc thesis of Tim Neeskens, TU Delft)



Figure 8b: Design example (MSc thesis of Tim Neeskens, TU Delft)

Finally, the MSc thesis works of Marc den Heijer and Stella Brugman are currently investigating the insulating performance of the composite thin glass panels. The cavity that is created between the thin glass panels by means of the 3D-prined core provides a certain degree of thermal insulating performance similar to a regular insulating glass unit, whereas the 3D-printed core acts as a thermal bridge between the glass panels. The MSc projects investigate the combined effects of these phenomena. Prof. dr. ir. Christian Louter, Institute of Building Construction, TU Dresden

Figure 9: Thin glass composite panels under UV-exposure to investigate the long-term durability (MSc thesis of Charbel Saleh, TU Delft)


The support of AGC in providing the thin glass needed for this research is gratefully acknowledged. Also the support of engineering offices ABT and Octatube in co-supervising some of the MSc thesis works is much appreciated. Moreover, the external student supervision from prof. Maurizio Froli and Dr. Francesco Laccone from Pisa University and Prof. Tomaso Trombetti from University of Bologna is acknowledged. Researchers involved: Prof. Christian Louter (research leader), prof. James O’Callaghan, prof. Tillmann Klein, prof. Rob Nijsse, dr. Michela Turrin, dr. Marcel Bilow, dr. Fred Veer, dr. Martin Tenpierik. MSc-thesis projects by: Michele Akilo, Stella Brugman, Marina Guidi, Marc den Heijer, Lorenzo Lazzaroni, Bahareh Miri, Tim Neeskens, Rafael Ribeiro Silveira, Charbel Saleh, Özhan Topcu, Congrui Zha

Figure 10: Composite thin glass panels with curved 3D-printed core patterns (MSc thesis of Marina Guidi (left) and Charbel Saleh (right), TU Delft)



The Inception of Modern Polymer Science

Control of Molecular Structure and Function for Designer Polymers Polymers are essential building blocks of both biological life and artificial everyday objects (Figure 1). Every polymer molecule consists of long chains of repeating units (mers) linked together either linearly or within a complex architecture. Building blocks may be nucleotides in DNA, aminoacids in proteins, or petroleum-based small molecules, such as ethylene, propylene or styrene in the case of synthetic polymers. Hermann Staudinger proposed almost exactly hundred years ago, that polymers are covalently bonded chain-like molecules. [1] To celebrate this discovery the year 2020 has been named the year of polymer science.

Although covalent bonds hold together the monomers in both natural and synthetic polymers, they are fundamentally different, and this difference is expressed in the structure of the polymer chains. Every single macromolecule of a given type of protein or DNA strand is essentially identical, as it comprises the same number of mers. Even more: the sequence of consecutive mers in the chain is strictly predefined in a biological macromolecule, which in turn is critical


for its unique structure. These primary, secondary, tertiary and eventually quaternary structures define all biological functions of proteins and enzymes. The sequence control is the essence of complementary base pairing of DNA chains, responsible for both transferring genetic information and protein synthesis. On the other hand, typical synthetic polymers consist of a mixture of chains of many possible lengths (i.e. molecular weights). This is because most polymers,

of which we consume ~200 megatons a year, [1] are synthesized by coordination or by free radical polymerization. Radicals are extremely reactive species that within one second of a lifetime can react with thousands of monomers (i.e. polymerizable molecules containing a C=C double bond). After reaching the average one second lifetime, two radicals recombine or disproportionate, terminating the reaction. As these reactions occur at random, molecular


Figure 1. Synthetic polymers vs biopolymers. Left: Every day-use, commodity plastics consist of polymer chains of random molecular weights. Right: Hemoglobin contains four protein subunits; each protein has a strictly determined sequence of aminoacids, which gives rise to a unique way the protein folds. The folded structure enables specific function of the protein. (Image source: Wikipedia and Wikibooks)

weight distributions (MWD, also called dispersity, which is a measure for the spread of the distribution) is observed in synthetic polymers, as opposed to monodisperse biopolymers which display no distribution, i.e. each macromolecule is of the same chain length. [2] While plastics based on high dispersity polymers revolutionized the materials world in the 20th century, for many years polymer chemists have been trying to synthesize

well-defined polymers with a level of control approaching those from nature to eventually approach the properties and sophisticated function of their natural counterparts.

Prevent Termination

A typical chain growth polymerization process consists of three main reactions: initiation (i.e. formation of active species), propagation (i.e. chain growth

by repetitive addition of monomers) and termination (deactivation of active species). Very poor control over the polymer structure in conventional free radical polymerization usually arises from the continuous slow initiation, short radical lifetime and fast biradical termination. The ground-breaking discovery to overcome this limitation was made by the Polish-American chemist Michael Szwarc

Figure 2. Free radical vs ‘living’ polymerization. (a) Average molecular weight in free radical polymerization stays constant throughout the reaction, whereas in living polymerization the molecular weight increases linearly since all the chains grow simultaneously. (b) MWD is broad in free radical polymerization and approaches 1 in anionic polymerization. (Adapted from ref. [4] with permission from Royal Society of Chemistry)



Figure 3. Top: Mechanism of ATRP. Halogen (X) is transferred between the initiator/growing chain (R-Pn-X) and the copper catalyst (Cu/L) forming a radical (R-Pn·). This radical can add monomers (M), or terminate, however termination is minimized due to the equilibrium (KATRP) being strongly shifted towards the left side of the reaction. Bottom: Schematic overview of polymer microstructures enabled by controlling the radical polymerization process and examples of applications of these materials. (Adapted from ref. [7] with permission from American Chemical Society)

in 1956. Instead of employing radicals as active chain carriers, he used carbanions. [3] Unlike radicals, carbanions do not react with each other and thus do not terminate. Importantly, all chains could be initiated at the same time and propagate concurrently. The phrase ‘living’ was proposed for such an anionic polymerization, as all chains grow simultaneously without any termination, affording well-defined polymers with dispersity < 1.10 (Figure 2). The process has been used in industry, for example in the production of thermoplastic elastomers, i.e. physically crosslinked and recyclable rubbers, such as Kraton.

Trick the Termination: A Radical Idea

Despite the successful commercialization, anionic polymerization suffers from several drawbacks. Namely, carbanions are very sensitive to traces of moisture or impurities and require stringent conditions and special equipment. Additionally, only a limited number of


monomers can be polymerized via the anionic mechanism, as opposed to the radical one. Thus, methods to control radical polymerization to the extent of a typical living anionic polymerization have attracted tremendous interest. This goal was ultimately achieved in the 1990s with the development of the reversible deactivation radical polymerization (RDRP) techniques, such as atom transfer radical polymerization (ATRP). [5,6] In conventional radical polymerization, in order to suppress biradical termination a very low concentration of free radicals (parts per billion vs. monomer) is used to permit a radical lifetime of ca. 1 second to grow chains to MW in the range of 100,000. This is accomplished by very slow dosing radicals to the system (slow initiation) and stays in a stark contrast to living anionic polymerization, when all chains are initiated fast and grow simultaneously. Thus, RDRP was developed in which all chains start growing concurrently (fast initiation), but, in a ‘magic’ way, 1 s lifetime of growing chains was extended to hours or even days. This was accomplished

by introducing a large pool of dormant (inactive) species that exchange dynamically with minute amounts of growing radicals, which are deactivated back to dormant species after addition of a few monomers before they can terminate. Thus, by inserting ca. 1 min dormancy state after 1 ms activity, the overall life of growing chains can be extended to hours or days. This would be like extending human life from 100 years to 3000 years, if after each 1 day of activity we could be dormant for 1 month. In ATRP, a halogen atom is transferred between dormant alkyl halides and parts per million of Cu catalysts (see the reaction scheme in Figure 3), extending the lifetime of growing chains from 1 s to several days. This enables synthesis of well-defined, essentially tailor-made polymers with complex architectures such as stars, brushes, combs as well as controlled composition, functionality, chain topology etc., giving rise to a multitude of materials as summarized in Figure 3. [7]


Figure 4. (a) Two main approaches to synthesize polymer brushes: grafting pre-synthesized functional polymer chains onto a functionalized surface; or grafting polymer chains directly from initiator-modified substrate. (b) Idealized, schematic representation of surface-anchored polymer chains in brushes, end-functionalized with a fluorescent dye, and their behaviour in different solvents. (c) Fluorescent patterns obtained by inkjet-printed surfaces employing the grafting-to approach. (d) Responsive, switchable behaviour of end-functionalized fluorescent brushes prepared by the grafting-from approach. Adapted from refs. [8-10] with permission from American Chemical Society and John Wiley and Sons

‘God Made the Bulk; Surfaces Were Invented by the Devil’ In this famous quote, Wolfgang Pauli referred to the complexity of the surface properties of materials. The development of ATRP enabled macromolecular engineering of designer polymers and their applications in many fields including, for example, nanotechnology. One major class of hybrid nanomaterials synthesized by ATRP are so-called polymer brushes. They are polymer chains anchored with one end to a given surface, either two-dimensional (e.g. planar substrates) or 3D (nanoparticles, proteins). The ability to functionalize surfaces by attaching macromolecules, and thus tune their properties, have made polymer brushes a very intensely investigated field in polymer science. Polymer brushes can be synthesized by two main approaches: grafting-to, where functionalized polymer chains are anchored to a surface; or grafting-from, where polymers are ‘grown’ directly from the initiator-functionalized surface (Figure 4a). [8] Both approaches have been

used to prepare ‘smart’ surfaces from fluorescently-labelled polymers, namely polymethyl methacrylate (PMMA) synthesized by ATRP and functionalized at the chain end with a single fluorescein molecule. Interestingly, PMMA displays solvent-responsive properties, making these brushes collapsed and non-fluorescent in water, but stretched and emissive in water/alcohol mixtures (Figure 4b). By employing inkjet printing, patterns consisting of specific functional molecules were prepared on glass slides. Then, using simple dip coating of these slides in a solution of the fluorescently-labelled PMMA, a selective deposition of polymer chains on the printed drops was achieved, resulting in ordered emissive molecular arrays at the surface (Figure 4c). [9] Alternatively, PMMA brushes grafted from glass slides using surface-initiated ATRP and subjected to similar chain-end modification were used to demonstrate the responsive behaviour (Figure

4d). Upon exchanging the solvent from isopropanol/water (ON state) to pure water (OFF state), a clear change in emission was observed by fluorescent microscopy (Figure 4d). [10] Collapse of the brushes in water forced them to aggregate, quenching the fluorescence of the chain ends. Both studies show applicability of polymer brushes in the design of patterned, smart surfaces with potential applications such as sensors, or in organic electronics.

The Second Century

In the last two decades we have witnessed an immense progress in controlling the microstructure of polymers, driven mainly by the development of precision synthetic tools, such as ATRP. While not aiming at replacing traditional polymerizations in the production of commodities, these chemistries have enabled new applications by employing designer macromolecules. However, controlled polymerization techniques are still being improved to make them more environmentally friendly, oxygen-tolerant, easier to use and industry-relevant. Control


RESEARCH of the monomer sequence in synthetic polymers is still far from the level of sophistication achieved by nature but holds the promise of creating macromolecules with yet difficult to predict properties. With the growing need for advanced materials, we can be sure that precision polymerizations will be at the forefront of materials development when polymer science enters its second century. Maciek Kopeć In cooperation with Julius Vancso and Krzysztof Matyjaszewski. Materials Science and Technology of Polymers, University of Twente, The Netherlands E- mail:


References [1] Mülhaupt, R. Hermann Staudinger and the Origin of Macromolecular Chemistry. Angew. Chem. Int. Ed. 2004, 43, 1054. [2] Odian, G. Principles of Polymerization, Fourth Edition. John Wiley and Sons: Hoboken, New Jersey, 2004. [3] Szwarc, M. Living Polymers. Nature 1956, 178, 1168. [4] Okamoto, K.; Luscombe, C.K. Controlled polymerizations for the synthesis of semiconducting conjugated polymers. Polym. Chem. 2011, 2, 2424. [5] Matyjaszewski, K.; Xia, J. Atom Transfer Radical Polymerization. Chem. Rev. 2001, 101, 2921. [6] Coessens, V. M. C.; Matyjaszewski, K., Fundamentals of Atom Transfer Radical Polymerization. J. Chem. Educ. 2010, 87, 916. [7] Matyjaszewski, K.; Tsarevsky, N. V. Macromolecular engineering by atom transfer radical polymerization. J. Am. Chem. Soc. 2014, 136, 6513.

[8] Zoppe, J. O.; Ataman, N. C.; Mocny, P.; Wang, J.; Moraes, J.; Klok, H.-A. Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes. Chem. Rev. 2017, 117, 1105. [9] Kopeć, M.; Tas, S.; van der Pol, R.; Cirelli, M.; de Vries, I.; Vancso, G.J.; de Beer, S. Fluorescent Patterns by Selective Grafting of a Telechelic Polymer. ACS Appl. Polym. Mater. 2019, 1, 136. [10] Tas, S.; Kopeć, M.; van der Pol, R.; Cirelli, M.; de Vries, I.; Bölükbas, D. A.; Tempelman, K.; Benes, N. E.; Hempenius, M. A.; Vancso, G. J.; de Beer, S. Chain End-Functionalized Polymer Brushes with Switchable Fluorescence Response, Macromol. Chem. Phys. 2019, 220, 1800537. Parts of this research have been performed within the framework of the 4TU.High-Tech Materials research program ‘New Horizons in designer materials’

The project page can be found here:


A next-generation plastic that can be recycled again and again Because plastics contain various additives, like dyes, fillers, or flame retardants, very few plastics can be recycled without loss in performance or aesthetics. Eventually a lot of plastic disappears to incinerators or landfills, where the carbon-rich material takes ages to decompose. Now a team of researchers at the U.S. Department of Energy’s (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) has designed a recyclable plastic that, like a Lego playset, can be disassembled into its constituent parts at the molecular level, and then reassembled into a different shape, texture, and color again and again without loss of performance or quality. The new material, called polydiketoenamine (PDK) was reported in the journal Nature Chemistry (Closed-loop recycling of plastics enabled by dynamic covalent diketoenamine bonds, May 2019). Unlike conventional plastics, the mono-

mers of PDK plastic could be recovered and freed from any compounded additives simply by dunking the material in a highly acidic solution. The acid helps to break the bonds between the monomers and separate them from the chemical additives that give plastic its look and feel. The researchers first discovered the exciting circular property of PDK-based plastics when they noticed that by applying various acids to glassware used to make PDK adhesives, the adhesive’s composition had changed. An NMR (nuclear magnetic resonance) spectroscopy surprisingly showed the original monomers had been formed. After testing various formulations the researchers demonstrated that not only does acid break down PDK polymers into monomers, but the process also allows the monomers to be separated from entwined additives. Next, they proved that the recovered PDK monomers can be remade into

polymers, and those recycled polymers can form new plastic materials without inheriting the colour or other features of the original material. The researchers believe that their new recyclable plastic could be a good alternative to many nonrecyclable plastics in use today. The researchers next plan to develop PDK plastics with a wide range of thermal and mechanical properties for applications as diverse as textiles, 3D printing, and foams. In addition, they are looking to expand the formulations by incorporating plant-based materials and other sustainable sources.> The article ‘Closed-loop recycling of plastics enabled by dynamic covalent diketoenamine bonds’ is online>



Smart Materials, Part 3

Piezoelectric constitutive equations Smart materials are everywhere, but often invisible or simply not recognized. This is the second article in a series of eight, in which prof. Pim Groen will discuss the world of smart materials; this time piezoelectric materials. Piezoelectricity is the electric charge that accumulates in certain solid materials in response to applied mechanical stress and vice versa. Pim Groen is professor of SMART Materials at Aerospace Engineering (AE) at Delft University of Technology (TU Delft) and Programme Manager of Holst Centre, TNO. 30 | INNOVATIVE MATERIALS 3 2019

INNOVATIVE MATERIALS 3 2019 Before discussing the complex properties of a piezoelectric material it’s good to start with the elastic behaviour of a simple dielectric material; so basically a non-piezoelectric material.

Elastic behaviour

The strain and stress are related by Hooke’s law which states that the force needed to extend or compress a spring by some distance, scales linearly with respect to that distance. So in this case the strain is the product of the stress multiplied by the compliance and the strain is simply the relative deformation and the stress is the applied force per unit area.

Electric behaviour non-piezoelectric

Figure 1. Elastic behaviour

The same can be done for the electrical behaviour; again for a non-piezoelectric material. An electrical field is applied over a body with electrodes on each side. The thickness of the body is called t and area of the electrodes is A. The dielectric displacement is simply the dielectric constant times the electrical field.

Direct Piezoelectric effect

Compared with the piezoelectric material, things are different. If a force is applied to the material, it will deform and by the direct piezoelectric effect there will occur an induced electric polarisation. This effect can be described by the dielectric displacement D which equals to d times the stress plus epsilon times the electric field which is generated over the piezo. The piezoelectric charge constant , d which was discussed in part 2. Two cases can be distinguished. First: the short circuited situation: D becomes simply d times the T, stress. Second: (the interesting one), the open circuit. In this case the dielectric displacement is zero. As a result the electric field generated equals d times T divided by epsilon or simply g times the stress. The g is the other important piezoelectric constant and is d divided by epsilon. This g is highly important for sensors and is called the piezoelectric voltage constant.

Figure 2. Electric behaviour non-piezoelectric

Figure 3. Direct Piezoelectric effect



The most important piezoelectric constants are d and g. The piezoelectric charge constant d represents both piezoelectric charge constants: the induced polarization [C/m2] per unit applied stress [N/m2]; and the induced strain per unit applied field [V/m]. The piezoelectric charge constant can be expressed in two units: [C/N] for the direct effect and [m/V] for the inverse effect. g represents the piezoelectric voltage constant [V.m/N] . In case of the inverse piezoelectric effect an electric filed is applied over the material which as a result will deform. The strain is given by the compliance time the stress plus the piezoelectric charge constant multiplied by the electric field. Again, two different cases can be distinguished. The first one occurs when there is zero stress: the actuator moves freely. Now the strain equals simply d multiplied by the electric filed.

Figure 4. Inverse piezoelectric effect

Piezoelectric constitutive equations

Figure 7 shows the matrix which gives a complete description of the electric, the elastic and the piezoelectric behaviour. Let’s explain the subscripts of the piezoelectric charge constants. The first subscript is the direction the electrical quantity: this can be the electrical displacement or the electrical field. The second subscript denotes the mechanical quantity so strain or strain. Figure 8 shows the simplification for tetragonal PZT.

Figure 5. d and g

But now the pointsymmetry is helping to come to a simpler matrix with less elements. Barium titanate and PZT crystallize in a tetragonal crystal structure, as was discussed last time. As a result a large number of matrix elements become zero. Also you see that because of the symmetry d24 is equal to d15 and epsilon 11 equals epsilon 22. As noted earlier: this was the theoretical part, needed to properly understand the application of piezoelectric materials. Next time this will be put in practice.


Figre 6. Piezoelectric constitutive equations


Figure 7. Complete description of electric, elastic and piezoelectric behaviour

Piezoelectric Materials and components A few years ago, Pim Groen, together with Jan Holterman, published ‘Piezoelectric Materials and components.’ It’s available online> An extended version (hard copy) can be ordered via the website of> Authors: Jan Holterman, Pim Groen ISBN: 978-90-819361-1-8 Hardcover, 218 fullcolor illustrations, 307 pages.

Figure 8. Simplification for tetragonal PZT



Enterprise Europe Network (EEN) supports companies with international ambitions The Enterprise Europe Network (EEN) is an initiative of the European Commission that supports entrepreneurs in seeking partners to innovate and do business abroad. The Network is active in more than 60 countries worldwide. It brings together 3,000 experts from more than 600 member organisations – all renowned for their excellence in business support.


Every company can participate by adjusting its profile to the database. This company will be brought to the attention in the country in which it wants to become active. At the same time it is possible to search for partners. EEN advisers actively assist in compiling the profile, which is drawn up in a certain format. The EEN websites also contain foreign companies that are looking for Dutch companies and organizations for commercial or technological cooperation. The EEN advisers support the search for a cooperation partner by actively deploying contacts within the network. In addition, Company Missions

and Match Making Events are regularly organized. All these services are free of charge. There are five types of profiles:

• Business Offer:

the company offers a product

Video: How Enterprise Europe Network works

• Business Request:

the company is looking for a product

• Technology Offer:

the company offers a technology

• Technology Request:

the company is looking for a technology

• Research & Development Request:

the organization seeks cooperation for research

When a company has both a Business Offer and a Business Request (or another combination), two (or even more if applicable) profiles are created. The profile includes the most essential

information about the nature of the supply or demand, the ‘type of partner’ that is intended and the expected cooperation structure. Get in touch with your local network contact point by selecting the country and city closest to where your business is based. They can help you with advice, support and opportunities for international partnerships. For sustainable building and the creative industry, contact ir. drs. Hans Kamphuis: T: +31 (0) 88 042 1124 M: 06 25 70 82 76 E: For Materials contact Nils Haarmans: T: +31 (0) 88 062 5843 M: 06 21 83 94 57 E: More information websites can be found at the Europe Network websites:


ENTERPRISE EUROPE NETWORK The Enterprise Europe Network Materials Database: Request for partnership: June 2019 New materials to simplify the creation, manufacturing and end of life processing of polyolefins

An UK company and an European company are jointly seeking new technologies to facilitate the improved manufacturing and improve the functionality of polyolefins and polyols. The materials must have proof of concept and they should enable use in markets including construction, food, healthcare, automotive. Dependent on the stage of development the agreements may include licensing, joint venture, technical cooperation or commercial agreement with technical assistance. POD Reference: TRUK20190201001


Partners sought for the development of high-performance cellulosic fibre materials

A German company specialised in viscose specialty fibres is looking for partners who distribute suitable porous materials, preferably particles, to produce cellulosic viscose fibres with superior mechanical and chemical properties for applications in functional apparel textiles, technical nonwovens, hygiene products and specialty papers. Technical cooperation agreements are sought. POD Reference: TRDE20181213001


A Swedish accessories startup is looking for a supplier of lightweight and opaque, eco-friendly or recycled plastic material

A Swedish startup is looking for a supplier of lightweight and opaque, eco-friendly or recycled plastic material. All earrings are currently made with a 0.3 mm adhesive vinyl in two layers and the company is looking for an environmentally friendly version of this material with similar properties that is available in a wide range of colours and patterns and has a matte finish. It would be preferable if the supplier has the capability to punch/cut out the material. POD Reference: BRSE20190416001


Looking for biodegradable material producers to develop a paper stirrers dispenser for vending machine applications

A major Italian company active in the vending machines production is looking for a paper or biodegradable material producer to develop a new type of paper stirrers dispenser, to replace plastic stirrers. The partner would join in the project under a technical or research cooperation agreement. POD Reference: TRIT20190520001



ENTERPRISE EUROPE NETWORK The Enterprise Europe Network Materials Database: Request for partnership; June 2019 Construction company looking for partners to develop modular industrialized houses

A Spanish building company is looking for partners able to develop modular industrialized houses under a joint-venture agreement. The houses should be easily transported, ecological, sustainable, human size and preferably made of wood. The construction technology should allow to use all types of new materials and systems in order to serve the market that is developing in the South of Europe and already functioning in the North. POD Reference: TRES20190503001


Seeking for technical expertise and know-how in precision ceramic machining

A Singapore machining company is seeking technical expertise and know-how in precision ceramic machining. It is looking for experts, consultants and/or organisations with deep technical expertise and knowledge to help develop and establish fine and precise ceramic machining, machined ceramic component cleaning and quality check capabilities. Research, commercial agreement with technical assistance or joint ventures are being sought with SMEs, inventors or research institutes. POD Reference: TRSG20190517001 More>

A Japanese company is seeking 3D printing technology for building constructions to distribute in Japan

The Japanese company specialized in finance and real-estate markets is aiming to distribute leading 3D printing technology specific to building constructions in Japan. The constructions should meet the quality standards of Japan’s building sector. The partnership with a potential partner could be made within the frame of a commercial agency agreement, a distribution service agreement, licensing or services agreements. POD Reference: BRJP20190214001


Manufacturer of molybden mesh for microfocus X-ray tube

A Swedish SME has developed a new type of X-ray tubes and is now looking for a manufacturer of small high precision components to produce a grid consisting of a mesh (about 6 mm in diameter) and a copper holder. The X-ray tube provides a precise, stable, high-flux micro focus beam using ZnO cold cathode technology. The company has a partner for prototype production, but wants to establish a partnership and an agreement with a manufacturer in Europe to scale-up the production. POD Reference: TRSE20181213001



ENTERPRISE EUROPE NETWORK The Enterprise Europe Network Materials Database: Request for partnership; June 2019 Novel solutions sought for an unsinkable ship

A multinational shipping enterprise with a registered base in Scotland (UK) is seeking novel approaches to outfit their freight and passenger ships with permanent, lightweight buoyancy features that will limit the amount of sea water that can ingress into the ship when there is a hull breach, rendering the ship essentially unsinkable. The Scottish company is looking for partnerships via a joint venture or commercial agreement with technical assistance to pilot technology on a ship. POD Reference: TRUK20190114001


A Finnish company is seeking for a supplier or manufacturer of foam plastic components

A Finnish eco-design company is looking for a supplier or manufacturer of designed and round shape-cut foam plastic components. The diameter of the component is 90 mm. The desired form of cooperation is a manufacturing or a subcontracting agreement. POD Reference: BRFI20171214001


A Swedish start-up is requesting manufacturing of linen products with custom prints/ weaving

A start-up from Northern Sweden specialized in designing surface pattern is searching for a European manufacturing partner for production of patterned linen fabrics (through digital printing or weaving) and sewing of home and kitchen textiles. Favoured is a long-term partnership via a manufacturing agreement. POD Reference: BRSE20190412001


Waterproof and biodegradable material technologies sought for horticulture application

A French SME active in the field of horticulture is looking for new technologies to improve the sustainability of their product. In particular they are interested by a material with waterproof and biodegradable properties to be used for water tanks on the one hand and also by a coating fully natural making wood waterproof. A technical coperation with a partner able to provide relevant material or coating is sought. POD Reference: TRFR20190315001



EVENTS ICSBM 2019 12 - 15 August 2019, Eindhoven

Solids Rotterdam 2019 2 - 3 October 2019, Rotterdam

ISCHP 2019 28 - 30 August 2019, Delft

Metavak 8 - 10 October 2019, Gorinchem

International Rubber Conference 2019 3 - 5 September 2019, Londen

ISPA 2019 9 - 10 October 2019, Dresden

European Architectural Envisioning Conference EAEA14 3 - 6 September, Nantes

Euro PM 2019 13 - 16 October 2019, Maastricht

ESIAM19 9 - 11 September 2019, Trondheim

Holz 2019 15 - 19 October 2019, Basel

Matexpo 11 - 15 September 2019, Kortrijk

K 2019 16 - 23 October 2019, DĂźsseldorf

EMO Hannover 16 - 21 September 2019, Hannover

PARCIM13 13th Pacific Rim Conference on Ceramic and Glass Technology 27 - 31 October 2019, Okinawa

Stainless & Speciality Steel 17 - 19 September 2019, Sevilla

Betondag 2019 14 November 2019, Rotterdam

Werkstoff woche 2019 18 - 20 September 2019, Dresden

Formnext 19 - 22 November 2019, Frankfurt

European Symposium on Biopolymers 25 - 27 September 2019, Straubing

European Aluminium Congress 2019 25 - 26 November 2019, Dusseldorf

EFIB 2019 30 september - 2 October 2019. Brussel

European Bioplastics Conference 2019 3 - 4 December 2019, Berlijn

Schweissen 2019 1 - 3 October 2019, Linz, Austria

Swiss Plastics Expo 2020 21 - 23 January 2020, Luzern


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High-Tech Materials form the key to innovative and sustainable technology @4TU_HTM

4TU.HTM Research Programme New Horizons in Designer Materials | Visibility and accessibility of Materials Science & Engineering | Annual symposium Dutch Materials | 4TU.Joint Materials Science Activities | web application

Innovative Materials, the international version of the Dutch magazine Innovatieve Materialen, is now available in English. Innovative Materials is an interactive, digital magazine about new and/or innovatively applied materials. Innovative Materials provides information on material innovations, or innovative use of materials. The idea is that the ever increasing demands lead to a constant search for better and safer products as well as material and energy savings. Enabling these innovations is crucial, not only to be competitive but also to meet the challenges of enhancing and protecting the environment, like durability, C2C and carbon footprint. By opting for smart, sustainable and innovative materials constructors, engineers and designers obtain more opportunities to distinguish themselves. As a platform Innovative Materials wants to help to achieve this by connecting supply and demand. Innovative Materials is distributed among its own subscribers/network, but also through the networks of the partners. In 2019 this includes organisations like M2i, MaterialDesign, 4TU (a cooperation between the four Technical Universities in the Netherlands), the Bond voor Materialenkennis (material sciences), SIM Flanders, FLAM3D, RVO and Material District.

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