Graphene & New Materials Digest - February 2017

Graphene foam

Rice University scientists have created carbon nanotube reinforced graphene foam that can support 3,000 times its own weight – and then return to its original height. The conductive graphene foam is also highly conformable, being mouldable to almost any shape and size, the scientists report. The scientists tested the graphene foam as an electrode in lithium ion capacitors (LIC), with an energy density of 32 Wh kg-1 and after 500 cycles the device was still able to work at 78% capacity. The team believes this would be useful in electronics requiring mechanical and electrochemical stability.  

Soybean oil air-cured graphene

Scientists at Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) have developed a method to make graphene from soybean oil. The process, named GraphAir, involves using ambient air and the addition of a precursor to extract the carbon needed for graphene from the oil, meaning it has the potential to be fast, simple, safe and scalable according to the scientists. The process also works with other oils like waste oils left over from cooking. 

Stretchy printable electronic circuits

Researchers at Michigan State University have developed a stretchable integrated circuit using an inkjet printer. The material is a composite of other materials made from nanomaterials and organic compounds. The compounds are dissolved in solution to create a printable ink. The team has used the ink to create the stretchable material, the circuit and an organic light-emitting diode (OLED). However this still requires much work before commercialisation. 

Hagfish gunk liked by US Navy

The hagfish’s natural defence against predators is to release a sticky, gelatinous substance with the intention of clogging the predator’s gills. The slime is able to expand up to 10,000 times its initial volume. A synthetic version of this slime is being used by the US Navy that says that the material has mechanical properties comparable to Kevlar. The Navy intends the material to be used for ballistics protection, firefighting, anti-fouling, diver protection etc. 

Creating new materials on a liquid’s surface

Scientists at The Australian National University (ANU) have discovered a way to manipulate liquids to alter their material properties. Through controlled agitation of a liquid’s surface they could remote-control the nature of the material. The researchers say that the flow patterns at the surface of the liquid are novel materials, that could be capable of herding and trapping microorganisms, or which could have specifically designed electrical properties, for instance. 

Glowing chemical detectors

MIT scientists have made wearable devices out of cell-infused hydrogel films. When bacteria cells encounter certain materials, they will glow. The hydrogel provides a food source for the cells, that will keep them alive for several days. Different bacteria could be used to detect different chemicals in the environment. The device is composed of layers of hydrogel carved with tiny channels into which bacteria are injected; this is then fixed to a porous layer of rubber, protecting but still allowing the bacteria access to oxygen. Finally, the whole is bathed in a pool of nutrients. The researchers fabricated a glove incorporating the material and showed it glowing when it came into contact with a target chemical. 

Metamaterial doesn’t heat up

Engineers at Duke University have created an electromagnetic metamaterial – and it doesn’t contain any metal. Metamaterials are synthetic individual engineered materials not found in nature. The engineers showed that a dielectric metasurface – with a dimpled Lego-brick-like surface – made from their material was able to absorb terahertz waves without producing waste heat. The surface absorbed 97.5% of the energy produced by waves at 1.011 terahertz. The engineers believe that the material would be applicable to any electromagnetic frequency. The team believes that this material has uses in high-efficiency imaging, sensing and lighting as it doesn’t produce waste heat. 

Conductive graphene ink

A method for producing water based, conductive graphene ink has been developed by the Graphene Flagship working at the Cambridge Graphene Centre at the University of Cambridge, UK. Through a process of applying ultrahigh shear forces in a microfluidization process to exfoliate graphene from graphite the team were able to covert 100% of the starting graphite into flakes for use as conductive inks. The resulting inks have concentration of graphene flakes of 100g per litre. The team sees the ink being useful for printed electronics, RFID antennas, transistors and photovoltaic cells. The scientist claim that the process is scalable enough to allow for commercialisation.  

Metamaterial that cools

A team from the University of Colorado Boulder has created a metamaterial which has the ability to cool objects. The 50 micrometre thick glass-polymer hybrid can be applied to the surface of another material and it will cool it by reflecting incoming solar energy back into the environment and enabling the base material to shed its own heat through thermal radiation. The engineers say the material can be manufactured on roll, making it viable for residential and commercial use, such as cooling of buildings and powerplants and preventing overheating and increasing efficiency of solar panels for example. 

New material is very stiff

University of California Santa Barbara’s metamaterial, Isomax, has been shown to have achieved the theoretical limits of stiffness. Isomax is a solid foam material constructed of hollow three-sided pyramids, and octahedra reinforced with a cross of intersecting diagonal walls – giving the material a high strength-to-density ratio, and making it able to better withstand external forces than, for example, a honeycomb-structured material. The people behind the structure see it being used in aerospace structures, automobiles and robot machinery. 

Graphene enhanced contact lens

Researchers at Seoul National University, Graphene Square Inc and Interojo Inc, have developed a graphene-based conductive contact lens coating that could help protect the eye from electromagnetic radiation. The researchers applied a layer of graphene to the surface of a contact lens and then added some egg white and put it into a microwave oven. The graphene coating was shown to have protected the egg from some EM damage by dissipating it as heat over the lens’ surface. The graphene coated lens' temperature reached 45 degrees, whereas the temperature of an uncoated lens would hardly change. The also demonstrated that the lens can reduce water evaporation in vials capped with the lens by up to 30% compared to normal lenses. 

Temperature responsive material for fashion

MIT researchers have developed a material that responds to temperature to tighten or loosen. The team sees the material – which looks like the kind of foldable paper decorations one gets at Christmas – to have applications in the textiles and fashion industry to make clothing that responds to the environmental temperature to keep the wearer warm or cool.

Audio melding material

Researchers from the University of Sussex and University of Bristol in the UK have developed a metamaterial that is able to bend, form and focus audio waves as they pass through. The team arrange blocks made of the material to manipulate the audio waves. The team have demonstrated that by arranging the blocks in a single layer on a grid to create a certain sound field they could make a polystyrene bead levitate. The team see the material being used as an imaging device for medical diagnostics, or crack detection, or to focus ultrasound to destroy tumours deep in the body. 

Colour emitting material

Scientists at Osaka University have developed materials that emit multiple colours. The work advances mechanochromic luminescent materials (MCL) which could only emit two colours by flipping between two different states. The new material showed different colour responses to heating, fuming and grinding, changing colour between yellow, red, and orange. The material has been successfully incorporated into OLEDs and also displayed thermally activated delayed fluorescence (TADF), a phenomenon that has shown promise for use as a replacement to costly OLED technology. 

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