Nanowire Breakthrough Paves Way for Completely Flexible Devices



Nanowire Breakthrough Paves Way for Completely Flexible Devices
Silver nanowires and graphene combine to create a hybrid material, which matches the performance of the existing technologies at a fraction of the cost.
Technology Briefing

Transcript


Indium tin oxide, which is currently used to make smart phone screens, is brittle and expensive. The primary constituent, indium, is also a rare metal and is ecologically damaging to extract. Silver, which has been shown to be the best alternative to indium tin oxide, is also expensive. 

But now a breakthrough from physicists at the University of Sussex has combined silver nanowires with graphene - a two-dimensional carbon material - to create new hybrid material, which matches the performance of the existing technologies at a fraction of the cost.  

On top of that, the new approach also promises devices that use less energy, are more responsive, and do not tarnish in the air. The way in which these materials are assembled is new. Graphene is a single layer of atoms, and can float on water.  

By creating a "stamp" - a bit like a rubber stamp - the scientists can pick up the layer of atoms and lay it on top of the silver nanowire film in a pattern. The stamp itself is made from poly (dimethyl siloxane); the same kind of silicone rubber used in kitchen utensils and medical implants. 

While silver nanowires have been used in touch screens before, no one has tried to combine them with graphene. The new process is unique in the way it puts the graphene layer down.  

The researchers float the graphene particles on the surface of water, then pick them up with a rubber stamp, and lay it on top of the silver nanowire film in whatever pattern they wish. And this breakthrough technique is inherently scalable. 

It would be relatively simple to combine silver nanowires and graphene in this way on a large scale using spraying machines and patterned rollers. That means that brittle mobile phone screens may soon be a thing of the past.  

The addition of graphene to the silver nanowire network also increases its ability to conduct electricity by a factor of ten thousand. This means manufacturers can use a fraction of the amount of silver to get the same, or better, performance. As a result, screens will be more responsive and use less power. 

Although silver is also a rare metal, like indium, the amount needed to coat a given area is very small when combined with graphene. Since graphene is produced from natural graphite - which is relatively abundant - the cost for making a touch sensor drops dramatically. 

Until now, one of the issues with using silver is that it tarnishes in air. The researchers found that the graphene layer prevents this from happening by stopping contaminants in the air from attacking the silver. 

They also saw that when the hybrid films are bent repeatedly the electrical properties don't change, whereas you see "a drift" in the films without graphene, which people have developed previously. This research paves the way towards developing completely flexible devices.  

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