Touch Sensor Powers Itself

Materials scientists report a new touch sensor that powers itself from electrical charges picked up from a person touching the device’s surface (Nano Lett. 2014, DOI: 10.1021/nl5005652). The easy-to-assemble sensor could be used in security systems or even as flexible touch-sensitive skin for robotics, the researchers say. Zhong Lin Wang of Georgia Institute of Technology and his team built the device to exploit the triboelectric effect, the phenomenon behind static electricity. The sensor consists of two films of indium tin oxide (ITO) that serve as electrodes with a sheet of polyethylene terephthalate (PET) sandwiched between. The top of the device is a layer of fluorinated ethylene propylene (FEP) polymer studded with an array of nanowires made from the same fluorinated polymer. When someone touches the sensor, the FEP layer gathers charges on its surface and creates a voltage across the ITO electrodes. This voltage is large enough to power an external circuit. The device detects pressures as small as 0.03 kPa, which is less than the pressure typically produced when a person swipes a smartphone touch screen with their finger, Wang says.