These novel sensors invented at ISC can send out electrical impulses to control things. They have therefore been designed like an electrical capacitor – two electrode layers consisting of a conductive silicone above and below and one insulating film layer in between. However, if you press on the capacitor nothing happens at first.
“The electrical capacitance – the electrical charge divided by the voltage applied – is the decisive factor. However, in a conventional capacitor structure the pressure effect is so small that it can barely be measured let alone be used for control purposes,”Böse explains.
In order for the pressure to have an effect, the researchers applied additional layers of silicone on the film. Thus, for example, two more films press from above and below to put additional pressure on the film in the middle. The two films are not smooth but have a special pattern that was added by the researchers. Through their special capacitor design, the researchers were able to use a physical property of silicone, which so far has only been observed when stretching a silicone film coated with layers of electrodes – its geometry changes; the surface becomes larger and the silicone layer becomes thinner. The result is that the electrical capacitance increases. “We transferred it from tensile forces to compression forces,” explains Böse.