15 minute read
Research
from IM2021EN
Dr. Tatheer Zahra (Photo: Queensland University of Technology)
Running shoe material inspired 3D-printed design to protect buildings from impact damage
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A material used in running shoes and memory foam pillows has inspired the design of a 3D-printed product that could help protect buildings from collision damage and other high impact forces, like shock energy caused by gas explosions, earthquakes and wind forces. Dr Tatheer Zahra from the Queensland University of Technology (QUT) Centre for Materials Science used off-the-shelf material to 3D print geometric shapes that mimic the behaviour of auxetic materials. Her work was published on September 30 in Smart Materials and Structures.
Auxetics are structures or materials that have the property that when stretched, they become thicker perpendicular to the applied force. This occurs due to their particular internal structure and the way this deforms when the sample is uniaxially loaded. Such materials or structures have special mechanical properties, like high energy absorption and fracture resistance. Auxetics may be useful in applications such robust shock absorbing material, like running shoes.
According to dr Zahra 3D printing auxetic geometries could potentially replace steel and fibre reinforced polymer mesh reinforcements in composites, and could also be used as a flexible and widely applicable protective wall render. She said the energy absorption would be equivalent to a 20 mm thick reinforced composite protective render over a full-scale building wall, which could potentially withstand the impact force of a car travelling at 60 km/hr. Now that the potential of the material has been demonstrated in the lab, the designs will soon be tested in full scale.
More at QUT>
Video: A 180 g auxetic geometry resists 25kN force (approx. 2500 kg) by contracting in all directions to absorb energy of around 260 J without showing damage or changes in shape when released. If scaled-up, these geometries may be useful in saving buildings and other structures from collision impact
Self-healing ‘living materials’ used as 3D building blocks
Scientist of the Imperial College London have created ‘living’ 3D building blocks that can heal themselves in response to damage. So-called Engineered Living Materials (ELMs) exploit biology’s ability to repair material in response to inflicted damage. According to Imperial this could lead to the creation of real-world materials that detect and heal their own damage, such as fixing a crack in a windshield, a tear in the fuselage of an aircraft or a pothole in the road. Integrating the building blocks into self-healing building materials could reduce maintenance in the future and increase the lifespan and usability of a material. This work was published in Nature Communications on August 19th .
To create ELMs, the researchers used genetically engineered bacteria to have them produce fluorescent 3D sphere-shaped cell cultures, known as spheroids, and to give them sensors which detect damage. They arranged the spheroids into different shapes and patterns, demonstrating the potential of spheroids as modular building blocks. They used a thick layer of bacterial cellulose, an organic compound produced by certain types of bacteria. They damaged the material by making holes in it and then inserted the freshly grown spheroids into the holes. After incubating them for three days, it appeared that the material appeared to have repaired itself excellently. According to the scientists this discovery opens a new approach where grown materials can be used as modules with different functions like in construction. By placing the spheroids into the damaged area and incubating the cultures, the blocks were able to both sense the damage and regrow the material to repair it. The discovery also opens up to allow cultured materials to play a role as modules with different functions, such as in construction. The research should be seen in light of the growing scientific interest in bacterial cellulose. Bacterial cellulose is produced by some types of bacteria to form protective envelopes around the cells. It has different properties from plant cellulose and is characterized by high purity, strength, moldability and increased water holding ability. Although bacterial cellulose is produced in nature, many methods are currently being investigated to enhance cellulose growth from cultures in laboratories as a large-scale process. By controlling synthesis methods, the resulting microbial cellulose can be tailored to have specific desirable properties, which could be the basis for the development of a whole new class of functional materials. The next step is to develop new spheroid building blocks with different properties, such as combining them with materials like cotton, graphite and gelatins to create more complex designs. This could lead to new applications like biological filters, implantable electronics or medical biosensor patches.
‘Bacterial cellulose spheroids as building blocks for 3D and patterned living materials and for regeneration' by Ellis et al., was published 19 August 2021 in Nature Communications. It’s online>
www.imperial.ac.uk>
Researchers saw excellent repair that was structurally stable and restored the consistency and appearance of the material
Photo: DTU
New way to capture CO2
Worldwide efforts are being made to limit CO2 emissions, and one of the instruments to achieve this is CO2 capture. The techniques used to do this are mainly based on liquid processes. The most widely used method is to capture the CO2 from the flue gas and channelling it into a liquid. The flue gas or biogas is passed through long pipes to a large quantity of liquid - typically water - which contains various additives that help absorb the CO2 in the liquid. Once the CO2 has been absorbed in the liquid, it has been captured. This is an efficient method, but also highly energy-consuming.
At Technical University of Denmark (DTU), recently developed a new and more energy-efficient method that can capture the CO2 in a solid material and upgrade it to a cleaner product, which can subsequently be used to produce, for example, fuels. The researchers used a solid material that has ionic liquid1 in its pores. The ionic liquid binds the CO2 - and when the material has been saturated with CO2 - the CO2 can subsequently easily be released through a combination of slight heating and lowering of the pressure. According to the scientists one of the key advantages of using an ionic liquid is that it does not evaporate into gas when it is heated or the pressure is lowered, and it therefore remains in the solid material, which can be reused in the carbon capture unit. This avoids heating and pumping of excess liquid in the plant. The researchers hope to be able to capture up to 90 per cent of the CO2 from the biogas with an energy consumption that is less than half of that of the methods most commonly used today. The actual carbon capture unit with the new technology will be installed and tested as a demonstration project at one of Wärtsilä’s biogas plants in Sweden, where it will purify part of the biogas produced. The tests take up to six months and have
to demonstrate whether the material continues to capture and release CO2 efficiently. Both the materials and the process have been patented.
Source: DTU>
1 An ionic liquid (IL) is a salt in the
liquid state. In some contexts, the term has been restricted to salts whose melting point is below some arbitrary temperature, such as 100 °C. While ordinary liquids such as water and gasoline are predominantly made of electrically neutral molecules, ionic liquids are largely made of ions>
On the right: The material with the ionic liquid is shaped as small tubes. According to Professor Anders Riisager, the carbon capture testing of the biogas production at the plant in Sweden will be performed with approx. 10 kg of the material (Illustration: DTU Chemistry)
Scientists of National University of Science and Technology MISIS in Moscow have developed an easy and cost-efficient method for obtaining industry-grade silicon carbide from wood processing waste. The study was published in Materials Chemistry and Physics.
Silicon carbide is a hard, synthetically produced crystalline compound of silicon and carbon. Silicon carbide is nearly as hard as diamond, wear-resistant, heat and radiation proof. The material is widely used in the metal industry and in the manufacture of high-temperature bricks and other refractory materials. In addition, silicon carbide crystals are used in grinding wheels, sandpaper, the jewelry industry, construction, the production of bullet-proof vests, car parts such as brakes and much more. Interesting are so-called biomorphic carbides, which are made from carbon obtained from wood. Several biomorphic carbides have already been developed from different woods and even cereals: beech, oak, pine, linden, maize and millet. Recently, attempts have even been made to synthesize biomorphic silicon carbide from various industrial materials such as fiberboards, paper and wood composite boards. However, current technologies of biomorphic silicon carbide production are imperfect. The properties of the synthesized products are often unpredictable. In addition, the conventional methods of producing silicon carbide from charcoal are time consuming.
Scientists from NUST MISIS and Tomsk Polytechnic University have come up with a method for obtaining high-quality silicon carbide from charcoal and silicon in plasma of direct current low-voltage arc discharge in ambient air using an electric-arc reactor with graphite electrodes.
It was found that the three-fold arc processing during 25 - 30 seconds each at a current of 220 A allows a complete transformation of initial silicon into its carbide. An important advantage of the proposed method is the simplicity of the synthesis process, which doesn’t require a sealed chamber, inert gases or a vacuum pump. Another important advantage is that synthesis takes very little time (from seconds up to several minutes) compared to the conventional methods. And last but not least, the raw carbon material is renewable and comes from wood (waste).
More at NUST MISIS>
Sustainable glitters
Cambridge researchers have developed a sustainable, plastic-free glitter for use in the cosmetics industry - made from the cellulose the main building block of cell walls in plants. There are thousands of types of glitter, most commonly made from ultra-thin, multi-layered sheets that contain plastics as well as dyes and reflective materials such as aluminium, titanium dioxide, iron oxide and bismuth oxychloride. These sheets are then cut into small particles. Some experts warn that glitter poses a threat to the environment, contributing to microplastic pollution.
The sustainable Cambridge kind of glitter is made from cellulose nanocrystals, which can bend light in such a way to create vivid colours through a process called structural colour. The same phenomenon produces some of the brightest colours in nature - such as those of butterfly wings and peacock feathers - and results in hues that do not fade, even after a century. Using self-assembly techniques that allow the cellulose to produce intensely-coloured films, the researchers say their materials could be used to replace the plastic glitter particles and tiny mineral effect pigments which are widely used in cosmetics. In Europe, the cosmetics industry uses about 5,500 tonnes of microplastics every year.
After producing the large-scale cellulose films, the researchers ground them into particles of the size used for making glitters or effect pigments. The resulting particles are biodegradable, plastic-free and non-toxic. The researchers also say that they have succeeded in making the process suitable for industrial machines.
According to Camebridge, this is the first time these materials have been fabricated at industrial scale. Although further optimisation of the process is still needed, the researchers are hoping to form a spin-out company to make their pigments and glitters commercially available in the coming years.
The results are reported in the journal Nature Materials, titled ‘Large-scale fabrication of structurally coloured cellulose nanocrystal films and effect pigments.’ Nature Materials (2021). DOI: 10.1038/s41563-021-01135-8
More at Cambridge>
PeLEDs : stretchy, bendy, flexible LEDs
Researchers of McKelvey School of Engineering, part of The Washington University in St. Louis (WUSTL), have developed a new material suitable to fabricate a new type of flexible LEDs. Organic LEDs (OLEDs) are made with organic molecules or polymer materials. They are cheap and flexible. Inorganic LEDs such as microLEDs are high performing, bright and very reliable, but rigid and very expensive. The new technology combines the best of existing LEDs and organic LEDs (OLEDs). In addition, the WUSTL researchers developed a novel way to fabricate it - using an inkjet printer. The research was published last November in the journal Advanced Materials.
The WUSTL scientists used a particular type of crystalline material: modified organometal halide perovskite. The traditional way to create a thin layer of perovskite, which is in liquid form, is to drip it onto a flat, spinning substrate: so-called spin coating. As the substrate spins, the liquid spreads out, forming a thin layer. From there, it can be recovered and made into perovskite LEDs, or PeLEDs. In this process a lot of material is wasted by spattering away. And so the idea of the inkjet printer was born. Inkjet fabrication saves materials, as the perovskite can be deposited exactly where it’s needed. The process turned out to be much faster as well, cutting fabrication time from more than five hours to less than 25 minutes. Another benefit of using the inkjet printing method is that perovskite can be printed onto a variety of unconventional, even flexible substrates. However, the capability of printing on a flexible material appeared not to be enough; the LEDs themselves had to be flexible as well. This problem was solved by embedding the inorganic perovskite crystals into an organic, polymer matrix made of polymer binders. This made the perovskite and, by association, the PeLEDs, elastic and stretchable. However, there were problems to overcome. LEDs are constructed in a sandwich-like configuration, with at least an emissive layer, an anode layer and a cathode layer. Because all parts of the PeLED were made from liquid, the perovskite layer, as well as the two electrodes and a buffer layer, a major concern was keeping all of the layers from mixing. The team had to keep the perovskite layer safe from mixing with any of the others, the way running a highlighter over freshly written ink might smear it. So an suitable polymer has to been found, one that could be inserted between the perovskite and the other layers, protecting it from mingling while not interfering too much with the PeLED’s performance. After that was successful, the first stretchable PeLEDs could be printed effectively.
More at WUSTL>
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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.
Popcorn 'polystyrene'
Researchers from the University of Göttingen (Germany) developed a polystyrene-like material developed from popcorn. It can be used as packaging and insulation material, with compostable and has water-repellent properties. The technology is based on processes similar to those used in the plastics industry. German cereal producer Nordgetreide has received a licence agreement for the commercial use of the process and products for the packaging sector. German construction company Bachl Group is licensed to use the process to make building insulation.
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Roxipan
Roxipan is a decor panel with the appearance of concrete. Roxipan is adapted to both the construction and renovation of commercial, industrial, tertiary or private buildings. Wether smooth or not, water resistant or fire resistant, it is especially recommended for rooms with a high level of humidity. Roxipan panels are available in a variety of styles, smooth or rugged, plated on any support, MDF, plywood, chipboard, compact.
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Stax
Stax consists of layers of glass which are stacked and then fused together to create solid panels. This special process enables Nathan Allan to create exterior feature walls over very large surfaces. To classify the material as safety glass, flat panels of clear, cast, mirror glass are laminated to the back of the Stax panels. The lamination is necessary as the Stax glass panels are too thick to temper, which is the usual treatment to make safety glass.
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Balsaconcrete
Balsaconcrete is a lightweight material made of concrete with a core of foam. It can be used for tabletops, kitchentops, bathtubs and any other inside/outside panel or product that has to have the impact of concrete but not the heavy weight. Big sizes are possible, useable on any kitchenconstruction, available in all thicknesses, in any form and many colours.
Photography: evolveproductions.nl
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Timbercrete
Timbercrete is a building material, made of more than 50% by volume recycled sawmill waste. Homes made of this product consume less energy for heating/cooling. Timbercrete acts as a ‘carbon sink’ preventing the release of carbon dioxide from decomposing sawdust into the atmosphere. The material is fire resistant and can be used in a wide range of domestic, commercial, industrial and public buildings.
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Zero
Zero brick is a material which delivers joint-free brickwork without coming into conflict with the basic rules of traditional bricklaying. ZERO has an extra large hollow at the top to which the mortar can be applied. This makes it possible to reduce the joint thickness to 4mm. The bricklayer can simply go about his work with a trowel and ordinary mortar.
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Plexwood - geometric
Geometric is a 2-layer wood product, consisting of a substrate with a Plexwood veneer on one side. Angled in 15, 30, 45 or 0/90, +15/-15, +30/-30, +45/-45 degrees, new surfaces appear, creating inspiring and unlimited possibilities.
