Smartphone screens are usually brittle and expensive due to indium tin oxide that is used in making them but Sussex researchers have come out with a solution to make smartphone touchscreens that are cheaper, less brittle, and more environmentally friendly.
Currently, Indium tin oxide, which is also a rare metal and is ecologically damaging to extract or the best alternative to it is silver, which is also expensive. Professor Alan Dalton at the University of Sussex and his team have developed a new way to make smartphone touchscreens energy-saving, more responsive and withstand tarnish in the air.
The breakthrough was achieved when the physicists combined silver nanowires with graphene - a two-dimensional carbon material, producing a new hybrid material that matches the performance of the existing technologies at a fraction of the cost.
Even the manufacturing process of these materials is new. Graphene is a single layer of atoms that can float on water. It was made into a stamp using poly (dimethyl siloxane) and medical implants. The scientists picked up the layer of atoms and laid it on top of the silver nanowire film in a pattern.
Though silver nanowires have been used in touch screens before, no one has tried to combine them with graphene. In this technique, researchers have put the graphene layer down and floated the graphene particles on the surface of water. Then they picked them up with a rubber stamp, a bit like a potato stamp and lay it on top of the silver nanowire film in whatever pattern they liked.
"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. This means that brittle mobile phone screens might soon be a thing of the past," said Prof. Alan Dalton from the school of Maths and Physical Science at the University of Sussex.
The addition of graphene to the silver nanowire network also increases its ability to conduct electricity by around a factor of 10,000. "This means we 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," he said.
Although they use silver, another expensive material, Dr Matthew Large, lead researcher on the project, explained:"Although silver is a rare metal, like indium, the amount we need 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."
Since silver tarnishes in air, the researchers have found the graphene layer useful. It prevents it from happening by stopping contaminants in the air from attacking the silver.
"What we've also seen is that when we bend the hybrid films repeatedly the electrical properties don't change, whereas you see a drift in the films without graphene that people have developed previously. This paves the way towards one day developing completely flexible devices," he said.
