Graphene & New Materials Tech Digest - April 2017

Stretchy, self-healing material

Scientists at the University of California, Riverside, have developed an elastomer material that is extraordinarily stretchy and can self-heal when broken. A one inch film of the material stretched to 100 inches. The elastomer has been shown to twitch when exposed to an electric field, making it a potential material for artificial muscles. The material can selfheal at temperatures as low as -20C, and even if left separated for days. The stretchiness of the material is thought to be due to its fishnet-like molecular structure and the addition of metal ions that have an affinity for the molecular ligands. The material’s stretchiness and healing speed could be tuned by increasing or decreasing the amount of metallic ions in the material.  The scientists see the possibility of the material being used as an artificial skin, muscle or in flexible electronics. 

Increased pressure resistance could help graphene’s filtering ability

MIT researchers have developed a method to increase the strength of graphene sheets which would enable them to withstand the high pressure that is required in the desalination process. The team reinforced the graphene with an underlying substrate dotted with tiny pores. The resulting graphene was able to with stand pressures of up to 100 bars (20 times the pressure from a typical tap). The challenges that remain are how to create uniform pores on the graphene for use in desalination, and how to scale the material. 

Stencilling in 2D materials

Scientists from Penn State University, USA, have demonstrated stencilling with atoms in 2D materials, a method that has potential uses in next-generation electronics.  The material used in this case was transition metal dichalcogenide (TMD) which holds promise for use in computing to augment silicon on chips to give them new properties and abilities. The team’s methods to stencil patterns into the material was as follows: they spanned a photoresist on the material, as they would if they intended to make a device. It was then exposed to ultraviolet light in the desired areas and developed like a photograph. Where the polymer was exposed the photoresist washes away. This area is then cleaned. Only in the cleaned area will the 2D material grow.

Gecko feet 

Scientists at the American Chemistry Society have created a double sided adhesive that shares the ability shown by geckos’ feet of being able to adhere and then detach from a surface. The material, which works even on wet surfaces, is the result of integrating nanostructured hydrogel fibres onto an inorganic membrane. The material’s stickiness and friction changes in relation to pH levels. At pH 2 the material exhibited ultra-high friction and adhesion, would change to a state of low friction and stickiness when exposed to a solution of pH 12. The scientists see the material having potential uses in underwater robotics, sensors and bionic devices. 

Photosynthesis in synthetic material

Scientists at the University of Central Florida have discovered a way to trigger photosynthesis in synthetic materials called metal–organic frameworks (MOF). The MOFs use carbon dioxide from the air and turn it into formate and formamides (two types of ‘solar fuel’ – fuel produced directly from solar energy). To achieve this the scientists used titanium to which was added organic molecules that act as light harvesting antennas designed to absorb the blue spectrum of light when incorporated into the MOF. A device made to test the hypothesis was fed carbon dioxide while being exposed to blue light. It reduced the carbon dioxide into solar fuel and cleaned the air, the scientists claim. The team plan to fine tune the approach to make the device produce less reduced carbon which negatively impacts efficiency.

Biodegradable circuit boards

A team of scientists from Stanford University have created a biodegradable semi conductive cellulose substrate material that could be useful for implantable devices, wearables and sensors, as well as helping to reduce electronic waste. The substrate, into which electronics could be embedded, is flexible and conforms to a surface to which it is applied. The device can be made to dissolve by adding a weak acid such as vinegar. In addition the team developed electronic circuitry made of iron to add to the substrate, that is more environmentally friendly than traditional circuitry materials such as gold.

Nanotransistors

Scientists at Trinity College Dublin, Ireland, have made printed 2D-nanomaterial transistors which they believe could be incorporated into food and drink labels to warn of spoilage or indicate correct storage or serving temperature, for instance. The team used standard printing techniques to combine graphene nanosheets as the electrodes, with two other nanomaterials – tungsten diselenide and boron nitride – as the channel and separator (two important parts of a transistor) to form an all-printed, all-nanosheet, working transistor.
The team sees this as opening the way to printed 2D nanosheets for use as electronic circuits. 

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