Pressure on for flat sensors

A team of Austrian physicists has developed ultra-thin pressure sensors that can also be processed into sensitive textiles. Possible applications include ultra-thin microphones, pressure sensors for replacement skin, and interactive clothing.

The researchers used pressure sensitive foils known as ferroelectrets, which generate an electrical signal in reaction to pressure, to pass a signal to switch thin-film transistors. In combination, these made ultra-thin, pressure-sensitive switches that have a range of potential applications as a result of their sensitivity and low production costs.

‘The key factor is the correct coating of the components,’ said project manager Prof. Siegfried Bauer from the Institute of Experimental Physics at the Johannes Kepler University in Linz. ‘We applied a propylene foam over a TFT on a polyimide base. These are the type of TFTs we know from flat screens.’

The polymer propylene foam forms the sensor. When pressed, the differently charged sides of the individual cavities in the foam converge and produce an electrical signal.

‘The great thing about this combination is that the transistor switches only temporarily. If the pressure on the propylene layer decreases, the transistor reverts to its original state. Previously similar experiments only created permanent switching of the transistor. The transistor did not revert to its original state. That is naturally not ideal for a pressure sensor. It would still generate a signal even if the pressure were released,’ Bauer said.