Physicists at the University of Sussex may have come up with a solution to the long-standing problem of fragile smartphone screens.
The team of Scientists led by Professor Alan Dalton has developed a new technique to make smartphone touch screens that are less brittle, less expensive and more environmentally friendly. This approach also guarantees gadgets that are more responsive, use less energy, and do not discolor in the air.
Indium tin oxide, which is currently used to make the screens of smartphones, is costly and fragile, and this poses a problem. The principal component, indium, is a rare-earth metal and is ecologically damaging to extract. Indium tin oxide’s ideal alternative, silver, is also costly. The Physicists at the University of Sussex have successfully combined silver nanowires with graphene, which is a two-dimensional carbon material. This innovative hybrid material equals the performance of the current technologies at a much lower cost.
In particular, the way in which these materials are assembled is new. Graphene, which can float on water, is a single layer of atoms. By creating a stamp—similar to a potato stamp that a child might make—the Researchers 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), which is the same type of silicone rubber used in medical implants and kitchen utensils.
While silver nanowires have been used in touch screens before, no one has tried to combine them with graphene. What’s exciting about what we’re doing is the way we put the graphene layer down. We float the graphene particles on the surface of water, then pick 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 we like.
Professor Alan Dalton, The School of Mathematical and Physical Sciences, The University of Sussex
Professor Dalton then added, “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.”
“The addition of graphene to the silver nanowire network also increases its ability to conduct electricity by around a factor of ten thousand. 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.” Professor Dalton continued.
Although silver is also 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.
Dr Matthew Large, Leader of Research on the project, The School of Mathematical and Physical Sciences, The University of Sussex
Dr Large also said, “One of the issues with using silver is that it tarnishes in air. What we’ve found is that the graphene layer prevents this 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.” Dr Large added.
The paper titled, “Selective mechanical transfer deposition of Langmuir graphene films for high-performance silver nanowire hybrid electrodes”, is written by Matthew J. Large, Sean P. Ogilvie, Sultan Alomairy, Terence Vockerodt, David Myles, Maria Cann, Helios Chan, Izabela Jurewicz, Alice A. K. King and Alan B. Dalton at the Universities of Sussex, Surrey, and Taif in Saudia Arabia. It is published in the American Chemical Society’s Langmuir journal.