Touchscreen you don’t have to touch
Researchers have developed nanostructures that could pave the way for touchless interactive displays. Scientists led by Bettina Lotsch at Stuttgart’s Max Planck Institute for Solid State Research and LMU Munich created the materials that change electrical and optical properties when a finger comes near them by using a moisture sensor that can detect sweat on human skin.
Researchers claim touchless interactive screens would avoid problems their touch counterparts face with mechanical wear and transmission of bacteria and viruses.
The approach harness phosphatoantimonic acid, a crystalline solid at room temperature with a structure made up of antimony, phosphorous, oxygen and hydrogen atoms. P
irmin Ganter, doctoral student at the Max Planck Institute for Solid State Research and the Chemistry Department at LMU Munich, said: “It’s long been known to scientists that this material is able to take up water and swells considerably in the process. The material can be used to make sensors and Ganter explained:
“Because these sensors react in a very local manner to any increase in moisture, it is quite conceivable that this sort of material with moisture-dependent properties could also be used for touchless displays and monitors.”
Phosphatoantimonate nanosheets were then used to develop a photonic nanostructure which reacts to the moisture by changing colour.
Katalin Szendrei, also a doctoral student in Lotsch’s group, explained: “If this was built into a monitor, the users would then receive visible feedback to their finger motion.”
A multilayer sandwich material - with alternating layers of ultrathin phosphatoantimonate nanosheets and silicon dioxide (SiO2) or titanium dioxide nanoparticles (TiO2) – was constructed. With more than ten layers, the stack reached a height of little more than one millionth of a metre.
The material reacts to the change in humidity within a few milliseconds whereas previously reported materials normally took several seconds or more to respond.
There are still a number of challenges to overcome including economic production methods and a protective layer that can still let moisture through.