IM20212EN

Volume 2 2021

PIEZOELECTRIC WOOD: ELECTRICITY FROM WOODEN FLOORS CLEAN WATER, THANKS TO NEW PLASTIC CERIUM MOLYBDATE MATERIAL BEATS COVID CLEANER, GREENER PLASTICS FROM WASTE FISH PARTS RECYCLABLE BIOPLASTIC MEMBRANE CLEARS OIL SPILLS RECYCLING HIGH-TECH WASTE BIOLOGICALLY FROM TEXTILE TO SUGAR TO NEW TEXTILE

Voeg informatie toe aan de Kennisbank Biobased Bouwen De Biobased Economy speelt een belangrijke rol in de duurzame ontwikkeling van Nederland en biedt nieuwe kansen voor het bedrijfsleven. Via de kennisbank kunt u kennis vergaren en delen over de beschikbaarheid en toepassingsmogelijkheden van biobased materialen, producten en bouwconcepten. Samen versterken we zo de biobased economie. Ruim dertig partijen in de bouwsector ondertekenden de green deal biobased bouwen. Deze producenten, architecten, adviseurs en kennisinstellingen delen hun kennis rond kansrijke mogelijkheden van biobased bouwen. Ook de ministeries van Binnenlandse Zaken (Wonen en Rijksdienst), Economische Zaken, en Infrastructuur en Milieu ondersteunen de green deal. Bouw ook mee aan de biobased economie en voeg uw project- of productbeschrijvingen toe aan deze kennisbank. Kijk op www.biobasedbouwen.nl voor meer informatie>

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CONTENT About

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 2021 (6 editions) costs € 40,70 (excl. VAT) Members of KIVI and students: € 25,- (excl. VAT)

SJP Uitgevers

Postbus 861 4200 AW Gorinchem tel. +31 183 66 08 08 info@innovatievematerialen.nl

Publisher

Gerard van Nifterik

Advertizing & sponsoring

Drs. Petra Schoonebeek ps@innovatievematerialen.nl

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), prof.dr.ir. Jos Brouwers, (Department of the Built Environment, Section Building Physics and Services TU Eindhoven), prof.dr.ir. Jilt Sietsma, (4TU.HTM/ Mechanical, Maritime and Materials Engineering (3mE), Kris Binon (Flam3D), Guido Verhoeven (Bond voor Materialenkennis/SIM Flanders, Prof. dr. ir. Christian Louter (Institut für Baukonstruktion Technische Universität Dresden).

2 News 12 Digitalized road construction: Knitting roads

Empa scientists are investigating how roads could be reinforced with simple means and recycled easily after use. Their tools are a robot and a few meters of string.

14 Piezoelectric wood: Electricity from wooden floors

Researchers at Empa and ETH Zurich have made wood compressible and turned it into a micro-generator. When it is loaded, an electrical voltage is generated. In this way, the wood can serve as a bio-sensor - or generate usable energy. 18 Clean water, thanks to new plastic UT researchers Ameya Krishna B, Dr. Saskia Lindhoud and Prof. Dr. Wiebe de Vos (Faculty of Applied Sciences/MESA +) have developed anion-exchange membranes from a new type of plastic (saloplastic). The technique can be used to make membranes that are extremely stable in extreme conditions such as a very high or low pH. This makes them useful for fuel cells or water desalination. They published their work in the journal Journal of Colloid and Interface Science at the beginning of March.

20 New cerium molybdate material beats COVID

Researchers at Tokyo Institute of Technology working in collaboration with colleagues at the Kanagawa Institute of Industrial Science and Technology and Nara Medical University in Japan have succeeded in preparing a material called cerium molybdate (γ-Ce2Mo3O13 or CMO), which exhibits high antiviral activity against coronavirus. The results of the study were published earlier this year in Materials Letters, titled ‘Preparation of cerium molybdates and their antiviral activity against bacteriophage Φ6 and SARS-CoV-2.’

22 Cleaner, greener plastics from waste fish parts

Derived from crude oil, toxic to synthesize, and slow to break down, conventional polyurethanes are not environmentally friendly. Today, researchers discuss devising what they say should be a safer, biodegradable alternative derived from fish waste like heads, bones, skin and guts that would otherwise likely be discarded. Fish-oil based polyurethane could help meet the immense need for more sustainable plastics. A team of Francesca Kerton, Ph.D. of the Memorial University of Newfoundland developed a process for converting this fish oil into a polyurethane-like polymer. The researchers presented their results at the spring meeting of the American Chemical Society (ACS) held online during April 2021.

24 Recyclable bioplastic membrane to clear oil spills from water

Polymer scientists from the University of Groningen and NHL Stenden University of Applied Sciences, both in the Netherlands, have developed a polymer membrane from biobased malic acid. It is a superamphiphilic vitrimer epoxy resin membrane that can be used to separate water and oil. This membrane is fully recyclable. When the pores are blocked by foulants, it can be depolymerized, cleaned and subsequently pressed into a new membrane. A paper describing the creation of this membrane was published in the journal Advanced Materials on 7 March 2021.

30 Recycling high-tech waste biologically 34 Tiny mushrooms make new hook-and-loop fasteners 36 Nanocomposites for Solid-State Batteries 38 From textile to sugar to new textile

Cover: Design PV modules, Lucerne University of Applied Sciences and Arts, page 6

INNOVATIVE MATERIALS 2 2021

NEWS

Circular viaducts: innovative wood-concrete girder Mobilis and ipv Delft are developing a circular viaduct of wooden beams with a prefabricated top layer of recycled concrete. It is one of ten proposals within an SBIR process of Rijkswaterstaat (the Dutch irectorate-General for Public Works and Water Management). SBIR stands for Strategic Business Innovation Research (SBIR) Circular Viaducts. Rijkswaterstaat’s call was answered last year by 32 parties, 10 of which are now engaged in feasibility studies. Later this year, three parties will actually be allowed to develop a prototype.

Wooden beams

The wood-concrete beam system is a direct alternative to the current prefab concrete beams. The system consists of laminated wooden beams with a deck of

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recycled concrete. The beams are held together by tensioning them together with transverse prestressing. Cantilevered precast concrete edge elements protect the wood against weather influences, which ensures a very long lifespan of one hundred years. Application of the innovative modular system has significant advantages. In this way, an MKI reduction of 40 percent is achieved. The environmental cost indicator (MKI) shows the environmental impact and shadow costs of a product. The system owes its good MKI score to, among other things, the use of wood, a renewable material that absorbs CO2 instead of emitting it, and recycled concrete. The weight of an arbitrary viaduct will be approximately 20 percent lower, which will lead to a reduction in the foundation material. In addition, the

product is modular and the various elements can be completely separated and reused after use. An additional advantage of the modular system is the short implementation time. TBI company Mobilis and ipv Delft are working closely with engineering firm Miebach (wooden bridge construction), Rutte Groep (recycled concrete) and Heko Spanten (supplier of wood construction) in the development of their version of the circular viaduct. ipv Delft> Mobilis>

NEWS

Coca-Cola: Paper Bottle Coca-Cola is partnering with Danish startup Paboco to develop a 100 % paper bottle. According to the company a paper bottle than can be recycled like any other type of paper, and it opens up a whole new world of packaging possibilities. The first-generation prototype consists of a paper shell with a 100 % recycled plastic closure and liner inside. The next step, is to create a paper bottle without the plastic liner. Paper bottles must adhere to the same stringent safety and quality standards as other food and beverage packaging. The project is still in its initial stages of development, but according to Paboco, it has potential to be a real breakthrough in circularity for the industry, unearthing huge potential in how packaging is designed, produced and used by consumers. The paper bottle concept supports The Coca-Cola Company’s World Without Waste sustainable packaging goal to collect and recycle a bottle or can for every one it sells by 2030. The company also wants to significantly reduce the amount of packaging materials and only use fully recyclable packaging materials. Coca Cola Company>

video

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NEWS

Copr Bay Bridge

Foto’s: coprbayswansea

On March 8th, a gold-coloured bridge that features more than 2,700 laser-cut shapes has been installed in Swansea, Wales. The 150 metric tonne Copr Bay Bridge over Oystermouth Road is up to 12 metres wide, 49 m long and features 2,756 laser-cut origami shapes. Commissioned and developed by Swansea Council, the footbridge will be pivotal in improving access between the city, the Marina and the coastline. Copr Bay Bridge is especially notable for its aesthetic appearance. The pattern on the bridge’s side panels was designed by Swansea-born artist Marc Rees in collaboration with architect Acme (London). The bridge was eventually made from curved 15 mm steel plate. The iconic arch stabilizes the slender bridge deck and creates a new urban space ‘floating’ over the road, enclosed by patterned steel offering glimpses across the road, the arena and the new coastal park. Until now, Oystermouth Road was for cars, not people. The bridge will be a stepping stone for a greener and more liveable Swansea city centre. Swansea city centre is undergoing one of the largest urban transformations currently being delivered in the UK. £1 billion is being invested in comprehensive projects across the city to allow Swansea to realise its potential as one of the most vibrant places to live, work,

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visit and study in the nation. It is expected that the bridge will be ready for use in the second half of this year, ahead of the opening of the regeneration project’s arena which is on schedule to be completed this year. More at coprbayswansea.com>

Video (Swansea Council)

NEWS

Hét expertisecentrum voor materiaalkarakterisering. Integer, onafhankelijk, objectief onderzoek en advies. ISO 17025 geaccrediteerd. Wij helpen u graag verder met onderzoek en analyse van uw innovatieve materialen. Bel ons op 026 3845600 of mail info@tcki.nl www.tcki.nl

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NEWS

Design Florence Schölp, winner of the public award

From PV module to design There is plenty of space for energy generation on building envelopes. However, photovoltaic façades are still rare, even though technology and aesthetics can be combined. As part of a competition, students at the Lucerne University of Applied Sciences and Arts (HSLU) there-

Lynn Balli’s winning design

6 | INNOVATIVE MATERIALS 2 2021

fore designed photovoltaic modules as design objects for a façade of NEST. NEST is a modular research and innovation building of Empa, for the Swiss Federal Laboratories for Materials Science and Technology. At NEST, new technologies, materials and systems are tested, rese-

arched, further developed and validated under real conditions. The winning projects were selected on February 19, 2021. In a two-week block event, students and lecturers from the Department of Design and Art worked with lecturers

NEWS

Design Laura Schor

from the Department of Engineering and Architecture to design PV modules for Empa and Eawag’s modular research and innovation building NEST1 in Dübendorf. The designs simulate PV modules in a new guise of colours, patterns and motifs, and how they could be visually integrated into the NEST research and innovation building of Empa and Eawag in Dübendorf. At the end of the workshop, there were two selection processes at a public online event to award the best projects.

Firstly, there was an Audience Award: participants were allowed to choose their own winning project via online voting. The winning project of the online voting went to Florence Schöb with her design ‘Networked’. In addition, a professional jury appointed the official winner. ‘Glasklar’ by Lynn Balli was declared the winning design by the jury, consisting of executives from Empa, HSLU and Zug Estates. ‘An elegant highlighting of the dynamics of glass and the successful implementation with eight individual works

of art,’ the jury said. Lynn Balli’s PV module designs will be installed on the façade of NEST in the summer of 2021. Further Information Prof. Dr. Stephen Wittkopf Tel. +41 41 349 36 25 stephen.wittkopf@hslu.ch More info at HSLU> More about NEST>

Lynn Balli’s winning design, visualized on the NEST building

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NEWS

3D printed ‘iglo’ from PET waste The first 3D printed workspace has been put into use in the Grofsmederij (forging works) on the RDM site in Rotterdam. The workspace was printed in De Werkplaats at M4H using PET waste from industry based in the port and beyond. The so-called R-IGLO was commissioned by Royal3D and designed by the ArchiTech Company. Together with local entrepreneurs, the Port of Rotterdam Authority is looking for sustainable developments. The R-IGLO is a great example of this.

Design

This sustainable property solution is named R-IGLO due to its distinctive and instantly recognisable appearance. The letter R stands for Reusable, Recycled, Rotterdam and Royal3D. The ArchiTech

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NEWS

Rotterdam Makers District The Rotterdam Makers District is made up of M4H Rotterdam and RDM Rotterdam. The Rotterdam Makers District hosts entrepreneurs and knowledge institutions working on inventions for the new economy. Start-ups are given the chance to expand and become established organisations. It is where young people are introduced to technology. New, occasionally serendipitous partnerships can create innovative technologies that can be tested and applied on site. The area acts as the incubator, testing ground and shop window for the new economy for the entire region. Collectivity forms the basis for circularity: knowledge, space and flows are shared in physical and digital networks.

Company designed the shape and distinctive pattern. The structure consists of adaptable elements of different sizes. Its modular character means the individual sections are easy to transport and assemble, which also makes them easy to dismantle and store.

Grofsmederij on the RDM site in Rotterdam. In its management capacity, The Port of Rotterdam Authority is responsible for all property at RDM. More about the PET iglo> Photo’s: Port of Rotterdam

video

3D Printer

The R-IGLO is printed from recycled PET material from the port of Rotterdam, reinforced with 30 % fibreglass. Using Royal3D’s Continuous Fibre Additive Manufacturing (CFAM) printer in De Werkplaats in M4H, printing can be carried out on an industrial scale. The machine prints at least 15 kg per hour and can print objects measuring up to 4 x 2 x 1.5 metres. CFAM allows fibre to be added continuously to the print material, significantly increasing its structural strength and stiffness. The R-IGLO is a Port of Rotterdam Authority pilot project that is now being implemented and tested in the

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MAKE IT MATTER

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

Stack3D masonry robot Startup Stack3D has developed a bricklaying robot that gives architects freedom of design when designing prefab brickwork. This makes it possible to provide industrialized construction with prefabricated masonry in every conceivable form. It stacks bricks in various, predetermined patterns. According to the manufacturer, the new bricklaying robot ­makes it possible to produce a complex digital design completely digitally. More at MaterialDistrict>

Circular carpets Studio Wae produces circular modular carpet tiles. These tiles are made of manufacture errors or overstock, provided by the three biggest carpettile producers of The Netherlands. These tiles are composed with 100 % production waste. This means no new resources are needed for the products which is great for the CO2 footprint. The designs are inspired on M.C. Esher.

More at MaterialDistrict>

Turning plastic bags into self cooling fabric Researchers at MIT developed self-cooling fabrics made from polyethylene, a material commonly used in plastic bags. Polyethylene (PE) is thin and lightweight, and it lets heat pass through rather than trapping it. On the other hand, the material also locks in water and sweat. The scientist find a way to make polyethylene weakly hydrophobic and able to attract water molecules to its surface. The fibres were then bunched together to make weavable. More at MaterialDistrict>

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MAKE IT MATTER MultiTexPro Leveling, acoustic and insulating wallpaper. The first two layers of the innovative MultiTexPro wall covering level out any unevenness up to 4 mm on the wall. The textile top layer provides a sleek finish. The thickness of the material inhibits sound waves and insulates the room.

More at MaterialDistrict>

Expanded cork Earthkweek developed a green roof system based on the expanded cork of Pro Suber. In this way they help to reduce the city’s temperature and temper the effect of heavy short term rainfall. By using the cork based system there will be a cooling effect in the summer and an extra layer with insulation capacity that would lower the heating costs in winter.

More at MaterialDistrict>

Flax Wall core Faay is a Dutch family-owned business with 45 years of experience in the field of partition walls and false ceilings. They manufacture around 1,000 panels a day. Faay wall panels have a solid core of clamped flax fiber. The environmental impact of flax production is low. That is because flax absorbs CO2 and converts it into oxygen while it is growing and it has a low energy content during the processing process which means its environmental impact is low. More at MaterialDistrict>

BetaWare For her master thesis at Bauhaus-Universität Weimar, German designer Lara Weller developed a vegan and compostable material - BetaWare - made from sugar beet waste and molasses, and which can be processed using existing processing techniques. As proof-of-concept, six products were designed to show that BetaWare can be used in a variety of ways. Each product was manufactured using different processes, such as milling, sawing, drilling, casting and pressing. More at MaterialDistrict>

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NEWS

Digitalized road construction:

Knitting roads Empa scientists are investigating how roads could be reinforced with simple means and recycled easily after use. Their tools are a robot and a few meters of string. The idea of constructing objects, simply using a robot, stones and rope originates from a project of the Gramazio Kohler Research lab at ETH Zurich. Here the project was actually raised as an art and research project. Pillars piled up purely from strings and gravel demonstrated that outstanding stability can be achieved by simply interlocking the gravel with a thread - without any cement as a binder. Laboratory tests showed that gravel pillars with a height of 80 cm and a diameter of 33 cm can withstand a pressure of 200 kN, which corresponds to a load of 20 tonnes. The technique was used a few years ago in the Rock Print Pavilion at the Gewerbemuseum in Winterthur, Switzerland. The pavilion was built with thirty tons of loose stones, 120 kilometers of rope - and a construction robot. The same kind of technique is now used to construct roads. A robotic arm lays out a string in a geometrical pattern on a bed of gravel. What appears to be a contemporary art performance is basic

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The Rock Print Pavilion at the Gewerbemuseum in Winterthur, Switzerland 2018. The pavilion was built with thirty tons of loose stones, 120 kilometers of rope - and a construction robot

NEWS are placed on top of each other in a test box, with the floor of the box covered with a rubber mat that fixes the whole package to the ground. It simulates the deformable bed, to which the pavement is applied. The gravel-thread package is then loaded with a rotating plate and with pressure after which two tests were carried out: one with a rope-armed stone package; and another without. This load test shows that by entangling the individual gravel stones with the thread, the package can withstand a pressure of 5 kN - half a tonne - without the stones moving much. Normally, the binder bitumen performs this task in asphalt. Dynamic load tests with rolling pressure, similar to the extreme conditions road pavements have to withstand, are soon to be carried out. In parallel to their lab experiments, the researchers model everything in 3D on the computer using the Discrete Element Method (DEM). This should reveal the displacement of individual stones and the tensile forces acting on the thread something that cannot be investigated in the lab. In addition, different patterns and mesh widths and their effects on the stability of the pavement will also be examined in more detail.

The robotic arm lays out the ‘knitting pattern’. Empa researchers are investigating different patterns in a number of test series (Image: Empa)

research that explores new ways in road construction. On the one hand, robot-assisted construction techniques for road building are being tested that have so far only been used in structural engineering. On the other hand, a new type of mechanical reinforcement is intended to change the typical structure of the road surface and thus to help save valuable resources in future or even to recycle road surfaces altogether. Asphalt also consists of rocks of various sizes and a binder, bitumen. Thus Martin Arraigada and Saeed Abbasion from Empa’s ‘Concrete & Asphalt’ lab transferred this concept to road construction. According to ETHZ, a string-reinforced road surface that does not require bitu-

men promises a number of advantages. Since bitumen is extracted from crude oil, air pollutants are released during production and also later during use. What’s more, it makes asphalt susceptible to cracking and deformation and, on top of that, impermeable to rainwater this too could be overcome. Last but not least, the process allows for a rollable and recyclable pavement. The Empa researchers are using various experimental setups to test solutions for the above-mentioned aspects. The robotic arm plays a central role. It places the string in a programmed pattern on the layers of gravel stacked on top of each other. For the mechanical tests, five of these layers of gravel and thread

The research of Martin Arraigada and Saeed Abbasion has not yet resulted in a final product that is ready to be used in road construction. However, their research provides a lot of innovative potential to get closer to a recyclable and possibly rollable road pavement with simple means. More at Empa>

Video

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INNOVATIVE MATERIALS

Piezoelectric wood

Electricity from wooden floors Researchers at Empa and ETH Zurich have made wood compressible and turned it into a micro-generator. When it is loaded, an electrical voltage is generated. In this way, the wood can serve as a bio-sensor - or generate usable energy.

The research of Ingo Burgert and his team at Empa and ETH Zurich aims at extending the existing characteristics of wood in such a way that it is suitable for completely new ranges of application. For instance, they have already developed high-strength, water-repellent and magnetizable wood (Innovative Materials volume 6 2020). Now, together with the Empa research group of Francis Schwarze and Javier Ribera, the team has developed a simple, environmentally friendly process for generating electricity from a type of wood sponge, as they reported last March in the journal Science Advances, titled ‘Enhanced mechanical energy conversion with selectively decayed wood.’

Piezoelectric

If you want to generate electricity from wood, the piezoelectric effect comes into play. Piezoelectricity means that an electric voltage is created by the elastic deformation of solids. This phenomenon is mainly exploited by metrology, which uses sensors that generate a charge

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Already a little pressure can generate electrical voltage in the wood sponge (Image: ACS Nano/Empa)

INNOVATIVE MATERIALS

This is how a piezoelectric nanogenerator works: after the rigid wooden structure has been dissolved, a flexible cellulose network remains. When this is squeezed, charges are separated, generating an electric voltage (Image: ACS Nano/Empa)

signal, say, when a mechanical load is applied. However, such sensors often use materials that are unsuitable for use in biomedical applications, such as lead zirconate titanate (PZT), which cannot be used on human skin due to the lead it contains. It also makes the ecological disposal of PZT and Co rather tricky. Being able to use the natural piezoelectric effect of wood thus offers a number of advantages. If thought further, the effect could also be used for sustainable energy production. But first of all, wood must be given the appropriate properties. Without special treatment, wood is not flexible enough; when subjected to mechanical stress; therefore, only a very low electrical voltage is generated in the deformation process.

years: delignification, the removal of lignin from the wood structure. Wood cell walls consist of three basic materials: lignin, hemicelluloses and cellulose. Of these three components, lignin has the function of giving the wood sturdiness. In order to transform wood into a material that can easily be deformed, lignin must at least partially be extracted. This is achieved by placing wood in a mixture of hydrogen peroxide and acetic acid. The lignin is dissolved in this acid bath, leaving a framework of cellulose layers. The resulting white wood sponge consists of superimposed thin layers of cellulose that can easily be squeezed together and then expand back into their original form - wood has become elastic.

Sponge

Burgert’s team subjected the test cube with a side length of about 1.5 cm to about 600 load cycles. The material showed an amazing stability. At each compression, the researchers measured

Jianguo Sun, a PhD student in Burgert’s team, used a chemical process that is the basis for various ‘refinements’ of wood the team has undertaken in recent

Electricity from wooden floors

a voltage of around 0.63V - enough for an application as a sensor. In further experiments, the team tried to scale up their wooden nanogenerators. For example, they were able to show that 30 such wooden blocks, when loaded in parallel with the body weight of an adult, can light up a simple LCD display. It would therefore be conceivable to develop a wooden floor that is capable of converting the energy of people walking on it into electricity. The researchers also tested the suitability as a pressure sensor on human skin and showed that it could be used in biomedical applications. The work described in the Empa-ETH team’s latest publication, however, goes one step further: the aim was to modify the process in such a way that it no longer requires the use of aggressive chemicals. The researchers found a suitable candidate that could carry out the delignification in the form of a biological process in nature: the fungus Ganoderma applanatum, the causes of white rot

Nanogenerator: after the rigid wood structure (left) has been dissolved with an acid, flexible cellulose layers remain (middle/right). When pressed together, differently charged areas are displaced against each other. The surface of the material becomes electrically charged (Image: ACS Nano/Empa)

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INNOVATIVE MATERIALS

Scanning electron microscopy (SEM) images of balsa wood (left) and delignified wood illustrate the structural changes (Image: ACS Nano/Empa)

in wood. The fungus breaks down lignin and hemicellulose in the wood particularly gently and the process can be easily controlled in the lab. There are still a few steps to be taken before the ‘piezo’ wood can be used as a sensor or as an electricity-genera-

ting wooden floor. But the advantages of such a simple and at the same time renewable and biodegradable piezoelectric system are obvious - and are now being investigated by Burgert and his colleagues in a follow-up projects. And in order to adapt the technology for in-

WE KUNNEN NIET ZONDER NATUUR Word nu lid op natuurmonumenten.nl en ontvang 4 x per jaar het magazine Puur Natuur

16 | INNOVATIVE MATERIALS 2 2021

dustrial applications, the researchers are already in talks with potential cooperation partners. Empa>

INNOVATIVE MATERIALS

Copper foam as a highly efficient, durable filter for reusable masks During the COVID-19 pandemic, people have grown accustomed to wearing facemasks, but many coverings are fragile and not easily disinfected. Most of current COVID filter systems are based on fiberglass, carbon nanotubes and polypropylene fibers. These materials have drawbacks. For example, they are not durable enough to undergo repeated decontamination procedures, while some further rely on electrostatics so they can’t be washed, leading to large amounts of waste. But there seems to be an alternative. Recently, researchers have developed metallic foams with microscopic pores that are stronger and more resistant to deformation, solvents, and high temperatures and pressures. Metal foams are durable, and their small pores and large surface areas suggest they could effectively filter out microbes. Researchers from Georgetown University (Washington) and the University of California (Davis) have investigated whether copper foam could indeed play such a role. They fabricated metal foams by harvesting electrodeposited copper nanowires and casting them into

a freestanding 3D network. A second copper layer was added to further strengthen the material. In tests, the copper foam held its form when pressurized and at high air speeds, suggesting it’s durable for reusable facemasks or air filters and could be cleaned with washing or compressed air. The team found the metal foams had excellent filtration efficiency for particles within the

0.1-1.6 µm size range, which is relevant for filtering out SARS-CoV-2. Their most effective material was a 2.5 mm-thick version, with copper taking up 15 % of the volume. This foam had a large surface area and trapped 97 % of 0.1-0.4 µm aerosolized particles, which are commonly used in facemask tests. According to the team’s calculations, the breathability of their foams was generally comparable to that of commercially available polypropylene N95 facemasks. The metal foam turned out to be easy to clean, recyclable and cheap. The researchers estimate that the materials would currently cost about $ 2 per mask, and that disinfection and reuse would extend their life, making them economically competitive with current products. The research was reported in ACS’ Nano Letters on March 24 2012, titled ‘Efficient and Robust Metallic Nanowire Foams for Deep Submicrometer Particulate Filtration.’ The abstract is online> More at ACS>

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INNOVATIVE MATERIALS

Clean water, thanks to new plastic UT researchers Ameya Krishna B, Dr. Saskia Lindhoud and Prof. Dr. Wiebe de Vos (Faculty of Applied Sciences/MESA +) have developed anion-exchange membranes from a new type of plastic (saloplastic). The technique can be used to make membranes that are extremely stable in extreme conditions such as a very high or low pH. This makes them useful for fuel cells or water desalination. They published their work in the journal Journal of Colloid and Interface Science at the beginning of March. Clean, fresh water has always been one of the most important resources for humans to survive. No wonder that a growing shortage of water has become a major concern in the last century. Researchers worldwide have been working to overcome this problem, for example by developing new technologies to create drinkable water. One of these technologies is electrodialysis for seawater or brackish water

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desalination. This technique requires an ion-exchange membrane that selectively allows the ions from aqueous salt to pass through them while blocking the water. The process to create these membranes is often challenging, leading to expensive membranes, while the resulting membranes are often not stable in extreme environments with either a very high or a very low pH.

New technique

The researchers found a technique that can overcome the problems faced by the commercially used ion-exchanged membranes by creating a so-called saloplastic. When mixing certain positively and negatively charged polymers in water, the scientists were already able to create a polyelectrolyte complex (PEC) that can be best described as a mozzarella-like ball of plastic. The main problem the

INNOVATIVE MATERIALS (MST; Faculty of S&T / MESA+) and the Molecular Nanofabrication group (MNF; Faculty of S&T / MESA+). The paper ‘Hot-pressed polyelectrolyte complexes as novel alkaline stable monovalent-ion selective anion exchange membranes’, by Ameya Krishna B, Dr Saskia Lindhoud and Prof Dr Wiebe de Vos is published earlier this year in the Journal of Colloid and Interface Science. Figure 1: The new process of hot pressing the polyelectrolyte complex leads to a dense and transparent membrane

team faced was how to easily process this complex into a usable membrane.

Hot pressing

The article is online> Text Universiteit Twente>

brane of the future, according to the researchers. The research has been done in the Membrane Science and Technology cluster

After researching several techniques, the researchers found hot-pressing to have the highest potential. In this process, the PEC is placed in a mould to be inserted in a hot press. At first, the press closes without any extra pressure and heats up to a temperature of 80 °C. After around twenty minutes, when the material reaches the set temperature, the hot press applies a high pressure of two hundred bar. Similar to the pressure felt underwater at a depth of around two kilometres.

Transparent film

The PEC remains under these conditions for five minutes, after which the material is cooled to 25 degrees Celsius. According to the scientists, the whole process takes around an hour, which is way less compared to other used techniques that can take up to several days. The final product is a dense and transparent film. The plastic from Twente is sturdy and flexible and fully dense down to the nanometer scale. Moreover, the approach is fully scalable and provides excellent control over the size, thickness and structure of the membrane.

Applications

The membrane has many potential applications besides desalination. The stability at very high and low pH levels makes it possible to use the material in fuel cells. Next to the relatively easy production process which does not rely on organic solvents, the material is also self-healing when added to saltwater, making it possibly the sustainable mem-

Figure 2: The final product, a dense and transparent film

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INNOVATIVE MATERIALS

New cerium molybdate material beats COVID Researchers at Tokyo Institute of Technology working in collaboration with colleagues at the Kanagawa Institute of Industrial Science and Technology and Nara Medical University in Japan have succeeded in preparing a material called cerium molybdate (γ-Ce2Mo3O13 or CMO), which exhibits high antiviral activity against coronavirus. The results of the study were published earlier this year in Materials Letters, titled ‘Preparation of cerium molybdates and their antiviral activity against bacteriophage Φ6 and SARS-CoV-2.’ The ongoing coronavirus pandemic has highlighted the urgency not only of vaccine development and rollout but also of developing innovative materials with antiviral properties that could play a vital role in helping to contain the spread of the virus. Conventional inorganic antimicrobial materials are often prepared with metals such as copper or photocatalysts such as titanium dioxide. However, metal-based materials can be prone to corrosion, and the effects of photocatalysts are usually limited under dark conditions. Now, a research team led by Akira Nakajima of Tokyo Institute of Technology’s Department of Materials Science and Engineering proposes a new type of an antiviral material that can overcome these drawbacks. The team successfully combined a relatively low-cost rare earth element cerium (Ce) with molybdenum (Mo), which is well known for its antibacterial effects, to prepare two types of cerium molybdate (Ce2Mo3O12 and γ-Ce2Mo3O13) in powder form. Both powders exhibited antiviral activity. Notably, γ-Ce2Mo3O13

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Scanning electron microscope image of CMO powder

INNOVATIVE MATERIALS also exhibited high antiviral activity against SARS-CoV-2, the virus that causes COVID-19. After four hours, the CMO powder reduced the level of coronavirus by four orders of magnitude (to less than 1/10,000 of the original level). The researchers infer that an effective combination of cerium with the molybdate ion as well as the specific surface area are key factors contributing to the observed antiviral activity.

Handles, straps, elevator buttons

To obtain the desired CMO powder samples with an almost single-crystal phase, the team conducted many trial experiments. If standardized and mass-produced, CMO could be used in a wide range of materials such as resins, paper, thin films and paints. This would open up the possibility of using CMO coatings for high-contact surfaces such as door handles, straps inside vehicles, elevator buttons and escalator belts as well as walls, tiles and windows, but especially in everyday items such as smartphones and clothing. He notes that applications for eye and face ware such as glasses and masks may take a little longer time to develop, but be on the horizon. Tokyo Institute of Technology> The article ‘Preparation of cerium molybdates and their antiviral activity against bacteriophage Φ6 and SARS-CoV-2’ (DOI : 10.1016/j.matlet.2021.129510) is online>

Figure 1. (a) Antiviral activity of prepared powders against coronavirus and photographs showing the change in plaque number of coronavirus after four hours: (b) control and (c) with CMO.

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INNOVATIVE MATERIALS

Cleaner, greener plastics from waste fish parts Polyurethanes are nearly everywhere. They are applied in shoes, clothes, refrigerators and construction materials. But these highly versatile materials can have a major downside. Derived from crude oil, toxic to synthesize, and slow to break down, conventional polyurethanes are not environmentally friendly. Today, researchers discuss devising what they say should be a safer, biodegradable alternative derived from fish waste like heads, bones, skin and guts that would otherwise likely be discarded. Fish-oil based polyurethane could help meet the immense need for more sustainable plastics. A team of Francesca Kerton, Ph.D. of the Memorial University of Newfoundland developed a process for converting this fish oil into a polyurethane-like polymer. The researchers presented their results at the spring meeting of the American Chemical Society (ACS) held online during April 2021.

The conventional method for producing polyurethanes presents a number of environmental and safety problems. It requires crude oil, a non-renewable resource, and phosgene, a colourless and highly toxic gas. The synthesis generates isocyanates, potent respiratory irritants, and the final product does not readily break down in the environment. The limited biodegradation that does occur can release carcinogenic compounds. Meanwhile, demand for greener alternatives is

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growing. Previously, others have developed new polyurethanes using plant-derived oils to replace petroleum. However, these too come with a drawback: the crops, often soybeans, that produce the oil require land that could otherwise be used to grow food. Leftover fish struck Kerton as a promising alternative. Salmon farming is a major industry for coastal Newfoundland, where her university is located. After the fish are processed, leftover parts are often discarded, but some-

INNOVATIVE MATERIALS times oil is extracted from them. Kerton and her colleagues developed a process for converting this fish oil into a polyurethane-like polymer. First, they add oxygen to the unsaturated oil in a controlled way to form epoxides, molecules similar to those in epoxy resin. After reacting these epoxides with carbon dioxide, they link the resulting molecules together with nitrogen-containing amines to form the new material. According to the scientists the resulting material is odorless. Kerton has recently had some success swapping out the amine for amino acids, which simplifies the chemistry involved. In other experiments, the team has begun examining how readily the new material would likely break down once its useful life is over. Team member Mikhailey Wheeler soaked pieces of it in water, and to speed up the degradation for some pieces, she added lipase, an enzyme capable of breaking down fats like those in the fish oil. Under a microscope, she later saw microbial growth on all of the samples, even those that had been in plain water, an encouraging sign that the new material might biodegrade readily. Kerton and Wheeler plan to continue testing the effects of using an amino acid in the synthesis and studying how amenable the material is to the microbial growth that could hasten its breakdown. They also intend to study its physical properties to see how it might potentially be used in real world applications, such as in packaging or fibres for clothing. Using fish oil, researchers have made a polyurethane-like material (Credit: Mikhailey Wheeler)

ACS>

A week of immersion in the world of 3D manufacturing! December 6 to 10 2021, International multi-event – Benelux region

The International multi-event - 3D Delta Week - will be organized from 6 - 10 December 2021. The 3D Delta Week will create value for users and providers along the 3D Manufacturing Value Chain. It will be the 3D manufacturing meeting point for expert and layman, inside or outside the Benelux region. The 3D Delta week is already gathering a dozen of renown events and will continue growing as the place-to-be, with activities aimed at specific sectors, at R&D and industry, at users and suppliers. The scheduling of events will allow participants to easily move from one activity to another. The Benelux area (the Delta) is a top region in terms of 3D production, with a myriad of academic and applied research centres, a particularly high number of 3D-printers and

numerous promising start-ups and established enterprises. On the user side, the region boasts a multitude of application areas - all in all, an extremely versatile and high-quality ecosystem. Now, the appropriate podium has been created to bring this leading 3D production region to the fore. The 3D Delta Week is an initiative initially set up by Brainport Eindhoven, Flam3D, Jakajima and Mikrocentrum. www.3ddeltaweek.com

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INNOVATIVE MATERIALS

Recyclable bioplastic membrane to clear oil spills from water Polymer scientists from the University of Groningen and NHL Stenden University of Applied Sciences, both in the Netherlands, have developed a polymer membrane from biobased malic acid. It is a superamphiphilic vitrimer epoxy resin membrane that can be used to separate water and oil. This membrane is fully recyclable. When the pores are blocked by foulants, it can be depolymerized, cleaned and subsequently pressed into a new membrane. A paper describing the creation of this membrane was published in the journal Advanced Materials on 7 March 2021. Superamphiphilic membranes, that ‘love’ both oil and water, are a promising solution but not yet a very practical one. These membranes are often not robust enough for use outside the laboratory environment and the membrane pores can clog up as a result of fouling by algae and sand. Chongnan Ye and Katja Loos from the University of Groningen and Vincent Voet and Rudy Folkersma from NHL Stenden used a relatively new type of polymer to create a membrane that is both strong and easy to recycle. The new vitrimer membrane is made by pressing and sintering of polymers from the natural monomer malic acid. This membrane can be recycled by ball milling and subsequent pressing and sintering.

materials that have the mechanical properties and chemical resistance of a thermoset plastic. However, vitrimer plastics can also behave like a thermo­ plastic, since they can be depolymerized and reused. This means that a vitrimer plastic has all the qualities to make a good membrane for oil spill remediation. Furthermore, it was made from malic acid, a natural monomer. The vitrimer is produced through basecatalysed ring opening polymerization between pristine and epoxy-modified biobased malic acid. The polymers are ground into a powder by ball milling and turned into a porous membrane through the process of sintering.

Dynamic network

Both water and oil will spread out on the resulting superamphiphilic membrane. In an oil spill, much more water is present than oil, which means that the

In recent years, the researchers from both institutes have joined forces to investigate vitrimer plastics, polymer

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Pores

The new vitrimer membrane is made by pressing and sintering of polymers from the natural monomer malic acid. This membrane can be recycled by ball milling and subsequent pressing and sintering (Illustration: Chongnan Ye, University of Groningen)

INNOVATIVE MATERIALS membrane is covered by water that can then pass through the pores. The membrane is firm enough to filter oil from the water. When sand and algae clog up the pores, the membrane can be depolymerized and recreated from the building blocks after removal of the pollutants. The principle has now been successfully tested in the laboratory on a scale of a few square centimeters. The scientists hope that an industrial partner will come forward that wants to further develop this membrane. More at RUG> The article is online>

The hybrid research group with (letf to right) Katja Loos, Chongnan Ye, Rik Brouwer, Renato Lemos Cosse, Vincent Voet and Rudy Folkersma (Photo University of Groningen/Chemport Europe)

18-20 May Online Event renewable-materials.eu Organiser

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All renewable material solutions at one event: bio-based, CO2-based and recycled The Renewable Materials Conference will provide new advantages and synergies by establishing a meeting point for numerous cross-sectoral networking opportunities. Day 1: • Renewable Chemicals and Building Blocks from Biorefineries, CCU and Chemical Recycling

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25 | INNOVATIVE MATERIALS 2 2021

RESEARCH

New mix could double concrete’s carbon uptake Concrete is a versatile, relatively cheap and easily available material. World­wide, 30 billion tons of concrete are used. Unfortunately, there is also a down­ side. Cement, a component of concrete, produces eight percent of the world’s carbon footprint. Looking to lower that percentage, Purdue University engineers have discovered a way to make concrete more sustainable. They developed an new recipe for concrete that has the potential to cut carbon emissions dramatically. A team lead by Mirian Velay-Lizancos, an assistant professor of civil engineering at Purdue (West Lafayette, Indiana), pro­ poses adding small amounts of nanoscale titanium dioxide to the cement paste that makes up concrete. The team found that titanium dioxide, enhances con­crete’s natural ability to sequester carbon dioxide. The team discovered that adding only small amounts of nano-titanium dioxide nearly doubles concrete’s absorption of the problematic greenhouse gas. The study recently appeared in the scientific journal Construction and Building

Materials: Modification of CO2 capture and pore structure of hardened cement paste made with nano-TiO2 addition: Influence of water-to-cement ratio and CO2 exposure age. Initially, Velay-Lizancos and two of her doctoral students, Carlos Moro and Vito

Francioso, were studying how titanium dioxide might interact with cement to make concrete stronger and how curing temperature might affect those interactions. They noticed that some of their concrete samples that included nano-titanium dioxide absorbed carbon dioxide from the surrounding air faster than other samples. Further investiga­ tion revealed that adding nano-titanium dioxide to the concrete mix decreased the size of calcium hydroxide molecules, making it vastly more efficient at absorbing carbon dioxide than other cement pastes. The addition accelerated the rate of carbon absorption and increased the total volume of carbon dioxide it can absorb. More at Purdue>

Marian Velay-Lizancos and her students are developing concrete that can sequester carbon dioxide more successfully and efficiently than traditional mixes (Purdue University photo/John Underwood)

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video

RESEARCH

New biodegradable insulation foam Researchers at the University of North Texas (UNT) College of Engineering have developed a new building insulation product that is stronger, safer, and more sustainable than the conventional polyurethane-based products currently used. Current conventional insulation releases volatile compounds into the atmosphere, adversely contributing to the home or workplace environment as well as to climate change. Nandika D’Souza, UNT professor in the Department of Mechanical Engineering, could have solved this problem. The team found that by mixing corn-based polylactic acid (PLA) with cellulose fibers and using supercritical carbon-dioxide, they were able to create a foam that was not only safer than the conventional insulation, but also compostable and energy efficient. Both PLA and cellulose are degradable fiber. The latter one is often found as a waste in the paper industry, so not only is it stronger, but also is cheaper and easier to come by. Conventional foams are not environmentally-friendly and do not break down

once they are no longer usable. They can stay in the environment for 1,000 years. The new UNT-foams are believed to be 90 percent biodegradable within 50 days. Despite its biodegradability, the foam lasts as long as the conventional insulation.

The results of D’Souza’s work were published in in Scientific Reports> UNT>

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RESEARCH

Heat conduction record with tantalum nitride Computer chips generate heat that must be dissipated as quickly as possible so that the chip is not destroyed. This requires special materials with particularly good heat conduction properties. In collaboration with groups from China and the United States, a research team lead by prof. Georg Madsen from the Institute of Materials Chemistry from TU Wien therefore set out to find the optimal heat conductor. They finally found what they were looking for a very specific form of tantalum nitride - no other known metallic material has a higher thermal conductivity. In order to be able to identify this record-breaking material, they first had to analyse which processes play a role in heat conduction in such materials at the atomic level . The results have now been published in the scientific journal ‘Physical Review Letters’. Basically, there are two mechanisms by which heat propagates in a material. Firstly, through the electrons that travel through the material, taking energy with them. This is the main mechanism in good electrical conductors. And secondly through the phonons, which are collective lattice vibrations in the material. The atoms move, causing other atoms to wobble. At higher temperatures, heat conduction through propagation of these vibrations is usually the decisive effect.

Limitations

But neither the electrons nor the lattice vibrations can propagate completely unhindered through the material. There are various processes that slow down this propagation of thermal energy. Electrons and lattice vibrations can interact with each other, they can scatter, they can be stopped by irregularities in the material. In some cases, heat conduction can even be dramatically limited by the fact that

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Tantalum nitride can conduct heat faster than almost all other materials (Illustration: TU Wien)

different isotopes of an element are built into the material. In that case, the atoms do not have exactly the same mass, and this affects the collective vibrational behaviour of the atoms in the material.

Hardly any different isotopes

The metal with the highest known thermal conductivity is silver, but the material with the highest thermal conductivity is diamond. But diamonds are expensive and very difficult to process. With elaborate theoretical analyses and computer simulations, the team finally succeeded in identifying a suitable material: the hexagonal θ-phase of tantalum nitride. Tantalum is particularly favourable because there are hardly any different isotopes. Almost 99.99 % of the naturally occurring tantalum is the isotope tantalum 181, other variants hardly occur. According to prof. Madsen the combination with nitrogen and the special atomic scale geometry make the phase metallic, and it suppresses interactions

of the heat carrying vibrations with other vibrations and with the conducting electrons. It is exactly those interactions that inhibit heat conduction in other materials. Therefore, this form of tantalum nitride combines several important advantages, making it a record-breaking material with a thermal conductivity several times higher than silver and comparable to diamond. This makes θ-phase tantalum nitride a very promising material for the chip industry, according to Madsen. Original publication: A. Kundu et al., ‘Ultrahigh Thermal Conductivity of θ-Phase Tantalum Nitride,’ Phys. Rev. Lett. 126, 115901 (2021), DOI: 10.1103/PhysRevLett.126.115901 The abstract is online> TU Wien>

RESEARCH

Graphene nanochannel water filters When sheets of two-dimensional nanomaterials like graphene are stacked on top of each other, tiny gaps form between the sheets that have a wide variety of potential uses. In research published in the journal Nature Communications, a research team of Brown University (Providence, USA) has found a way to orient those gaps, called nanochannels, in a way that makes them more useful for filtering water and other liquids of nanoscale contaminants. Use of these spaces that form between 2D nanomaterials are versatile. For instance, they could be used as a high performance filter. But using these nanochannels for filtration, these channels must be orderly oriented in some way. In the case of graphene stacks, the channels between the sheets are oriented horizontally. That’s not ideal for filtration, simply because liquid has to travel a relatively long way to get from one end of a channel to the other. It would be better if the channels were perpendicular to the orientation of the sheets. In that case, liquid would only need to traverse the relatively thin vertical height of the stack rather than the much longer length and width. According to Robert Hurt, a professor in Brown’s School of Engineering, no one had come up with a good way to make vertically oriented graphene nanochannels. That is until Muchun Liu, a former postdoctoral researcher in Hurt’s lab, figured out a novel way to do it. Liu’s method involves stacking Zr-doped graphene oxyde (Zr-GO) nano sheets on an elastic substrate, which is placed under tension to stretch it out. After the sheets are deposited, the tension on the substrate is released, which allows it to contract. When that happens, the graphene assemblage on top wrinkles into sharp peaks and valleys. When the graphene starts wrinkling, the sheets and the channels are tilted the out of plane. And if they are wrinkled a

a. Sketch of compressive film wrinkling. Side view of planar and 1D wrinkled films. Figure illustrates that wrinkling tilts the horizontal line into multiple near vertical line segments. b. Fabrication steps leading to vertically aligned Zr-GO/epoxy membranes. i), Drying-induced assembly of Zr-GO nanosheets (Zr/C atomic ratio approximately 1/22) on pre-stretched polystyrene substrate (GO film thickness 1 μm). Inset: nanostructure of planar Zr-GO films with horizontal alignment and tortuous flow pathways. Brown strips represent 1 μm thick multilayer GO film segments. The light-yellow box represents the epoxy matrix. Purple spheres represent ZrO(II) cations (unhydrated state for reference). Fully hydrated ZrO(II) diameter is approximately 1 nm, implying that ZrO(II) likely exists in the interlayer spaces in a partially hydrated state complexed with O-containing groups on GO. ii), Wrinkled Zr-GO films are produced by thermally activated mechanical compression. iii), Wrinkled Zr-GO films are removed from the substrate and imbedded into epoxy resin. iv), Multiple cycles of microtome sectioning yield Zr-GO/epoxy composite membranes. v), Side view of vertically aligned Zr-GO/epoxy membrane (VAGME) with the entrances to interlayer nanochannels open at the top and bottom surface. This method transforms a single planar Zr-GO film into hundreds of vertical film segments, where each segment is an array of approximately 1000 GO interlayer nanochannels aligned with a strong Z-directional component.

lot, the channels end up being aligned almost vertically. Once the channels are nearly vertical, the assemblage is encased in epoxy, and the tops and bottoms are then trimmed away, which opens the channels all the way through the material. The researchers have dubbed the assemblages VAGMEs (vertically aligned graphene membranes). The result is a membrane with short and very narrow channels through which only very small molecules can pass. Proof-of-concept testing demonstrated that water vapor could pass easily through a VAGME, while hexane - a

larger organic molecule - was filtered out. The researchers plan to continue developing the technology, with an eye toward potential industrial or household filtering applications. Brown University> The article ‘Controlling nanochannel orientation and dimensions in gra­ phene-based nanofluidic membranes’ by Muchun Liu, Paula J. Weston and Robert H. Hurt was published in Nature Communications, January 2021. It’s online>

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RESEARCH

Special peptide compounds in the form of a filter act as a biological fishing rod to remove gallium from industrial wastewaters (Image: HZDR/Sahneweiß)

Recycling high-tech waste biologically Rare metals are widely used in the high-tech industry. Many of these metals have a lower natural occurrence and are difficult to mine, which is also associated with high costs. This is why recycling plays an even more important role. By recovering the rare metals from industrial wastewater, slag or devices that are no longer in use, they can be returned to the recycling cycle. Scientists at the Helmholtz Institute Freiberg for Resource Technology (HIF) at the Helmholtz-Zentrum Dresden-Rossendorf have now shown that peptide-based material can be used for the extraction of gallium

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from production wastewater caused by the semiconductor industry. HIF researchers led by Dr. Katrin Pollmann have demonstrated that selective biosorption (the ability of certain microorganisms such as bacteria, yeasts, fungi, and algae to enrich themselves with metals or metal ions) is a suitable process for the recovery of gallium from industrial wastewater. Gallium is widely used in the semiconductor industry for wafer production, often in the form of gallium arsenide. Most of the industrial gallium is lost during production.

Nevertheless, gallium is of increasing importance for the industry. A high recycling rate from the gallium-processing industry is all the more important since they represent a much richer and more important source for secondary gallium production. Previous recycling processes for the production of gallium are often based on chemical electrolysis, an energy-intensive proces that also has environmental disadvantages. A relatively new alternative could probably be found in a biological approach. This recycling

RESEARCH method includes processes that use biological systems to extract metal from ores or waste materials. The biomass binds certain ions or other molecules in an aqueous solution or concentrates them. Biosorption is not dependent on metabolic activity and does not require the supply of nutrients. This enables biosorption to be used even in highly toxic environments. Biosorption is therefore an environmentally friendly alternative to recovering metals from industrial wastewaters, leaching solutions or mine waters. Freiberg’s scientists investigated typical biosorbent materials - peptides - that can recognize individual elements specifically, bind them selectively and remove them from solutions. A peptide is a molecule made up of a small number of amino acids linked together by peptide bonds. A peptide is distinguished from a protein by the small number of amino acids in the molecule, but can itself serve as a building block for a protein. To identify gallium-binding peptides, the HIF team used a technique that selects peptides that bind to a specific target. One of the five tested peptide filter materials in these experiments was shown to be particularly suitable for efficiently recovering gallium. However, this method has to be further deve­ loped for industrial application, since the chemical synthesis of the peptides for economic use in resource technology

Graphical abstract how gallium-binding peptides work as a tool for the sustainable treatment of industrial waste streams

is too expensive and not yet sufficiently environmentally friendly. Furthermore, it is important to optimize the peptides that a better metal binding capacity is achieved and thus a more efficient use is possible.

tys, F. Lederer, K. Pollmann, titled ‘Gallium-binding peptides as a tool for the sustainable treatment of industrial waste streams,’ was published earlier this year in Journal of Hazardous Materials (DOI: 10.1016/j.jhazmat.2021.125366)

The publication by N. Schönberger, C.Taylor, M. Schrader, B. Drobot, S. Ma-

Helmholtz-Zentrum Dresden>

The dates and location of MaterialDistrict 2021 are known. The event will move from March to September 15, 16 & 17 and from Rotterdam to Utrecht (Werkspoor Cathedral). MaterialDistrict Utrecht (formerly Material Xperience) is the only event in the Netherlands that offers material manufacturers and specifiers of materials in all sectors of spatial design (interior, architecture, garden & landscape, leisure, furniture & interior construction and exhibition, stage & decor).

SEPTEMBER 15, 16 & 17 2021 UTRECHT (WERKSPOORKATHEDRAAL)

Click here for more information

31 | INNOVATIVE MATERIALS 2 2021

RESEARCH

Straw and mango peels make renewable food packaging Wheat straw and mango peels that are normally disposed of in landfills or used as manure and animal feed could potentially be used in the development of renewable, biodegradable and non-toxic materials for food packaging. This is one of the main findings of a recent doctoral study at Stellenbosch University (SU, South Africa). This research was done by dr Lindleen Mugwagwa, who is a postdoctoral fellow in the Department of Process Engineering at SU. She recently obtained her doctorate in Chemical Engineering at SU. Mugwagwa’s study was the first to develop methods for extracting the necessary bio or natural polymers and antioxidants from both wheat straw and mango peels that contain properties which are suitable for developing an active food packaging material. It was also the first

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time that these products were integrated to form a biocomposite film, tested in a food environment. As part of her study, Mugwagwa deve­ loped and optimised processes for extracting these polymers and antioxidants. She then combined the polymers and antioxidants to make a food packaging material and tested the stability of the biocomposite films when in contact with food as well as their potential to release antioxidants into packaged food over time. Low-density polyethylene (LDPE) film, a commonly used plastic, was used as a benchmark. Mugwagwa says her study showed that the properties of polymers and antioxidants in wheat straw and mango peels can be tailor-made during extraction to

suit their application in food packaging. The polymers and antioxidants can be extracted simultaneously from the same feedstock without affecting their use in food packaging. According to Mugwagwa the type of food packaging material proposed in her study could be ideal to replace environmentally hazardous petroleum-based packaging materials. The publication ‘Fractionation of agro-waste to producebiopolymers and bioactive compounds for active food packaging’ is online> More at Stellenbosch University>

RESEARCH

Bioplastic made 100% of wood

More than 380 million tons of plastic are produced each year, far surpassing most other man-made materials. Huge quantities of plastics end up in landfills or disappear as litter and are slowly converting into millions of microplastic particles, polluting the oceans and soil. In the interest of decreasing this threat, a University of Maryland (UMD) research

team led by prof. Liangbing Hu recently developed a simple yet cost-effective in-situ lignin regeneration approach to synthesize a strong, large-scale, hydrostable, biodegradable and recyclable lignocellulosic bioplastic, produced 100 % from an abundant and inexpensive wood powder, which is generally discarded as waste. The study, entitled, ‘A strong,

biodegradable and recyclable lignocellulosic bioplastic,’ was published in Nature Sustainability on March 25. In the fabrication process, the porous structure of natural wood is deconstructed to form a homogeneous cellulose-lignin ‘soup’ that features nanoscale entanglement and hydrogen bonding between the regenerated lignin and cellulose micro/nanofibrils. Large-scale lignocellulosic bioplastic films can then be fabricated by simply casting the cellulose-lignin soup into a mold. Unlike most petrochemical plastics, this bioplastic can be broken down by microorganisms in soil, which offers an attractive closed loop cycle feature (see Figure). Additionally, the material is strong and robust, demonstrating a unique balance between degradability and durability. According to Liangbing Hu the lignocellulosic bioplastic can be made from various biomass feedstocks, such as grass, wheat straw and bagasse, giving the process an even wider range of possibilities. This study was a collaborative effort between scientists at UMD, University of Wisconsin-Madison, Yale University and the Center for Materials Innovation. The study was published March 25 2021 in Nature Sustainability: ‘A Strong, Biodegradable and Recyclable Lignocellulosic Bioplastic.’ DOI: 10.1038/s41893-02100702-w

he preparation of high-performance lignocellulosic bioplastic and its degradation, resulting in a close loop cycle (Credit: Qinqin Xia for the University of Maryland, College Park)

More at UMD>

33 | INNOVATIVE MATERIALS 2 2021

RESEARCH

The ‘mushroom’ covered surface of the adhesive material (Photo: Preeti Sharma)

Tiny mushrooms make new hook-and-loop fasteners Scientists from the universities of Wageningen and Groningen developed a material that sticks better than hook-and-loop fasteners and leaves no trace. Hook-and-loop fasteners, often referred to by the genericized trademark Velcro (due to the prominence of the Velcro Brand) typically consist of two components: lineal fabric strips which are attached to the opposing surfaces to be fastened. The basic principle is a mechanical form of adhesion, where the two surfaces interlock in order to stick together. However, these systems typi-

cally only function using specific counter surfaces and are often destructive to other surfaces such as fabrics. Researchers from Wageningen and Groningen have found a solution. They developed a surface patterned with soft micrometric features inspired by the mushroom shape showing a non destructive mechanical interlocking and thus attachment to fabrics. Adhesion occurs because the tiny mushrooms interlace with the mesh of the fabric. The material is flexible, which prevents damage when it is removed.

The closer the mushrooms are packed together, the stronger the adhesive effect. On the other hand, it prevents damage when pulling out. This is because the mushrooms interact; they influence each other through the surface. When pulling one mushroom loose, the flexible surface causes that at the same time its neighbour is pulled. According to the scientists, this work provides new handles for tuning the mechanical attachment properties of soft patterned surfaces that can be used in various applications including soft robotics.

Soft Rpbotics

The research is part of the Soft Robotics 4TU programme Soft Robotics. Earlier this year the research was published in Biointerphases, titled ‘Hooked on mushrooms: Preparation and mechanics of a bioinspired soft probabilistic fastener.’ More at WUR resource online>

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RESEARCH

New material: Rapid colour change

Colour change in electrochromic materials (Vera Hiendl, e-conversion/LMU)

Smart glass can change its colour quickly through electricity. A new material developed by chemists of the Ludwig-Maximilians-Universität München (LMU) has now set a speed record for such a change. Products such as automatically dimming rear view mirrors are based on electrochromic materials. Such materials consist of molecules and crystals whose optical properties change due to an external electric field or current. Recently, experts discovered that, in addition to established inorganic electrochromic materials, a new generation of highly ordered lattice structures can also be equipped with this capability: Covalent Organic Frameworks, so-called COFs. They consist of synthetically produced organic building blocks that, in suitable combinations, form crystalline and nanoporous networks. A team led by Thomas Bein (Physical Chemistry, LMU Munich) has now developed COF structures whose switching speeds and coloration efficiencies are many times higher than those of inorganic compounds. COFs are attractive

because their material properties can be adjusted over a wide range by modifying their molecular building blocks. Scientists at LMU Munich and the University of Cambridge took advantage thereof to design COFs that were ideal for their purposes. They have made use of the modular construction principle of the COFs and designed the ideal building block for our purposes with a specific thienoisoindigo molecule. Incorporated into a COF, the new component demonstrates how strongly it can improve the COF’s properties. At the same time, the new COF structures are much more sensitive to electrochemical oxidation. This means that even a low applied voltage is sufficient to trigger a colour change of the COFs, which is also completely reversible. In addition, this happens at very high speed: the response time for a complete and distinct colour change by oxidation is around 0.38 seconds, while the reduction back to the initial state takes only about 0.2 seconds. This makes the e-conversion team’s electrochromic organic frameworks among the fastest and

most efficient in the world. Several things in particular are responsible for the high speed. First: the conductive framework structure of the COFs enables fast electron transport in the lattice. And thanks to an optimized pore size, the surrounding electrolyte solution can quickly reach every corner. This is essential because the positive charge generated in the oxidized COF structure must quickly be charge-compensated by negative electrolyte ions. Last but not least, the product of the Munich scientists who are part of the e-conversion cluster of excellence has a very high stability. Long-term tests showed that the material was able to maintain its performance even after 200 oxidation-reduction cycles. According to LMU, these fundamental findings advances the development of a new class of high-performance electrochromic coatings. LMU> More about COF’s>

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RESEARCH

Self-assembled Vertically Aligned Nanocomposites for Solid-State Batteries The need to use solid-state batteries arises from the safety problems and limitations of conventional batteries’ liquid electrolytes. However, simply using solid-state electrolytes reduces the battery’s specific power; that is how fast it can charge/discharge. This limitation can be overcome by employing tridimensional geometries. Daniel Monteiro Cunha (University of Twente) focused on using self-assembled methods, via Pulsed Laser Deposition (PLD), to create lithium-containing Vertically Aligned Nanocomposites (VAN) to form such 3D geometries for application in solid-state batteries. Lithium-ion batteries are the primary power source for many applications - from portable electronics to electric vehicles, but none of the current devices can fully satisfy all the requirements for the projected energy storage needs. Standard rechargeable batteries are based on liquid electrolytes, which limit their

design and safety. Therefore, the need for all-solid-state micro-batteries arises, showing enhanced safety, volumetric energy/power density and chemical stability. These micro-batteries, developed by thin-film architecture, enables the powering of micro-scale devices, such as stand-alone sensor systems for internet

Figure 1: Top-view Scanning Electron Microscopy of a nanocomposite thin film composed of LiMn2O4 pillars embedded in an LiLaTiO3 matrix, promising solid-state battery materials

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of things, implantable medical devices, labs-on-chip, and credit cards. However, commercial solid-state batteries are constructed as a planar stack (two-dimensional) of thin-film layers, which exhibit undesirable energy vs power balance. This drawback can be overcome by the application of 3D geometries, increasing the internal surface area. Vertically aligned nanocomposite (VAN) thin films show such tridimensional structures. They have been developed as a new materials’ platform for creating self-assembled device architectures and multi functionalities. They show a wide range of attributes arising from the strong interplay among the materials’ properties. Highly crystalline VANs are self-assembled through PLD without control of the deposition sequence, as is required for other thin-film fabrication methods. Although various VANs have been studied in the last decade, no lithium-based VANs have yet been explored for energy storage. Considering that self-assembled VANs are obtained through PLD, the study’s main goal was to apply this principle for lithium-containing, non-toxic oxide materials and study its impact on the electrochemical behaviour for battery applications. Throughout the work, the possibility of obtaining such structures was demonstrated for various conditions. Its shape and distribution were

RESEARCH The PhD research work of Daniel Monteiro Cunha was carried out in the Inorganic Materials Science Group. His supervisors were prof.dr.ir. Mark Huijben and prof.dr.ing. Guus Rijnders from the faculty Science and Technology at the University of Twente. He successfully defended his PhD thesis on the 10th of March 2021. The title of his dissertation is ‘Self-assembled Vertically Aligned Nanocomposites for Solid-State Batteries’.

Figure 2: Cross-sectional energy selective backscattered scanning electron microscopy image showing the compositional contrast. This highlights the tridimensional geometry formation

The thesis can be found online> tailored, and electrochemical analysis shows the first steps towards battery application.

If this can be realized, batteries with better performance and safety can power various devices.

http://hightechmaterials.4tu.nl

Select key words and find relevant materials scientists or research groups within 4TU.

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

www.4tu.nl/htm @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 http://hightechmaterials.4tu.nl

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RESEARCH

Photography: Lund University/YouTube

From textile to sugar to new textile The collection of old textiles is relatively common, but it is less known that the collected textiles are rather difficult to recycle. Often collected textiles end up in landfills anyway. Researchers at Lund University in Sweden have developed a method that converts cotton into sugar, that in turn can be turned into spandex, nylon or even in ethanol. The production of waste textiles has steadily increased in recent decades due to the increase in textile consumption worldwide. For example, fibre consumption per capita was about 3.7 kg in 1950, rising to 10.4 kg in 2008. New recycling processes are therefore needed to initiate circularity in the textile world. Primary recycling technologies, where fibres are

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converted into new fibres, are preferred. However, as with paper recycling, cellulose fibres cannot be converted into new fibres indefinitely, as the regeneration process usually degrades the mechanical properties of the fibres. In addition, not all used garments would be suitable for such a recycling process. It has now been shown that enzymatic hydrolysis of lignocellulosic biomass can be used to depolymerize, but that technology is actually too expensive to process waste textiles. For that reason, the Lund researchers chose a different route, namely chemical hydrolysis, which promised to be a lot cheaper. The concept of hydrolysing pure cotton isn’t new. It was discovered in the 1800s.

The difficulty has been to make the process effective, economically viable and attractive. Now the researchers have succeeded in breaking down the plant fibre in cotton (cellulose) into smaller components, by soaking the fabrics in sulphuric acid. The most important challenge was to overcome the complex structure of cotton cellulose. In addition, there are a lot of surface treatment substances, dyes and other pollutants which must be removed. The secret is to use the right combination of temperature and sulphuric acid concentration. The search to find the right concentration of acid, the right number of treatment stages and temperature ultimately

RESEARCH dark-coloured sugar solution. Scientists believe that sugar as a raw material plays an important role in the biobased economy. For the chemical industry, sugar can even replace fossil raw materials for the production of chemicals and materials such as bioplastics and textile fibres. The article (Novel sustainable alternatives for the fashion industry: A method of chemically recycling waste textiles via acid hydrolysis) is online> Lund University>

resulted in a delicate process that can be used to convert textiles into new building blocks. When the team started making glucose out of fabrics a year ago,

the return was a paltry three to four per cent. Now they have reached as much as 90 per cent. The result of the new process is a clear,

Video

Plastic scanner From groundwater pollution to microplastics dissemination, plastic waste is a worldwide problem, now exacerbated by our reliance on disposable plastic products used in our effort to combat the COVID-19 pandemic. While in the West we can count on centralised and often automated waste recycling plants, most low- and middle-income countries cannot. Their recycling infrastructure is often informal, and has far fewer means to ensure correct waste management especially when it comes to the sorting of plastic. IDE student Jerry de Vos ((TU Delft Industrial Design Engineering) decided to tackle this issue in his Master Graduation project ‘Plastic Identification Anywhere’. He defended his thesis ‘Plastic Identification Anywhere: Development of open-source tools to simplify plastic sorting’ on February 25 at the Delft University of Technology. The research conducted in this thesis showed that especially the sorting stage of the plastic recycling process is very time consuming and labor-intensive. This discovery led to the central research question: which resources can be developed to accelerate the process of plastic sorting for informal recyclers? The project eventually led to a handheld plastic scanner using near-infrared spectroscopy, a technology known to be able to categorize more than 75 % of the plastics used in everyday life. To make it more accessible to informal recyclers in low and middle-income countries, and to easily integrate it in their countries’ waste management infrastructure, he developed this

device as an open-source project, whose components can be sourced and manufactured locally. Plastic scanner> More about this research>

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NIEUWS

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.

Database

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: hans.kamphuis@rvo.nl For Materials contact Nils Haarmans: T: +31 (0) 88 062 5843 M: 06 21 83 94 57 More information websites can be found at the Europe Network websites: www.enterpriseeuropenetwork.nl http://een.ec.europa.eu

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The corona crisis makes it uncertain whether events will actually take place on the scheduled date. Many events are postponed or online. The Agenda below shows the state of affairs as of May 2021. For recent updates: www.innovatievematerialen.nl International Conference on Natural Fibers (ICNF) 17 - 19 May 2021, Funchal

Plastics Recycling World Exhibition 2021 29 - 30 September 2021, Essen

1st Renewable Materials Conference, Hybrid 18 - 20 May 2021, Cologne

Vitrum 2021 5 - 8 October 2021, Milano

Eurasphalt & Eurobitume 15 - 17 June 2021, Madrid

Deburring EXPO 12 - 14 October 2021, Karlsruhe

Rapid.Tech + FabCon 3.D, 22 - 23 June 2021, Erfurt

Fakuma 12 - 16 October 2021, Friederichshafen

16th Coatings Science International 2021 29 June - 1 July 2021 , Noordwijk

Euro PM2021 Congress and Exhibition 17 - 20 October 2021, Lissabon

Additive Manufacturing Forum 2021 21 - 22 July 2021, Berlin

Glazing Summit 2021 21 October 2021, Birmingham

Kunststoffen 2021 15 - 16 September 2021, Den Bosch

Architect@Work 2021 Belgium 21 - 22 October 2021, Kortrijk

Materials+Eurofinish+Surface 15 - 16 September 2021, Den Bosch

iENA Nuremberg 29 October - 1 November 2020, Neurenberg

Material District Utrecht 15 - 17 September 2021, Utrecht

BOUWXPO 12 - 14 November 2021, Kortrijk

Nederlandse Metaaldagen 15 - 17 September 2021, Den Bosch

Fastener Fair Stuttgart 2021 9 - 11 November 2021, Stuttgart

Experience Additive Manufacturing 2021 21 - 23 September 2021, Augsburg

Solids 2022 16 - 17 February 2022, Dortmund

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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 2021 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.