The team, led by Professor Alan Dalton and in collaboration with M-SOLV Ltd, a touch-sensor manufacturer based in Oxford, looked to alternative materials to overcome the challenges of ITO, which is suffering from supply uncertainty. Alternative materials investigated as ITO replacements have included graphene, carbon nanotubes and random metal nanowire films. Their research showed how silver nanowire films have emerged as the strongest competitor, due to transmittances and conductivities which can match and exceed those of ITO.
“Our research hasn’t just identified silver nanowires as a viable replacement touchscreen material, but has gone one step further in showing how a process called ‘ultrasonication’ can allow us to tailor performance capabilities,” said University of Surrey researcher, Matthew Large. “By applying high frequency sound energy to the material we can manipulate how long the nanosized ‘rods’ of silver are. This allows us to tune how transparent or how conductive our films are, which is vital for optimising these materials for future technologies like flexible solar cells and roll-able electronic displays.”
The team has also demonstrated how silver nanowires can be processed using the same laser ablation technique used to manufacture ITO devices, which will make transitioning from manufacturing from ITO to nanowires more straightforward. Using this technique, the team produced a fully operating five inch multi-touch sensor, identical to those typically used in smartphone technology. They found it performed comparably to one based on ITO but used significantly less energy to produce.
Prof Dalton concluded: “The fact we are able to produce devices using similar methods as currently in use, but in a less energy-intensive way is an exciting step towards flexible gadgets that do not just open the door for new applications, but do so in a much greener way.”
The team is now looking to develop the scalability of the process to make it more industrially viable. One limiting factor is the cost of silver nanowires. Funded by Innovate UK and EPSRC, the team is collaborating with graphene supplier Thomas Swan to use a nanowire and graphene combination in the electrodes to reduce the cost.
