Large-area Sensor Skins and Microphones

Large-area sensor skins and microphones might be possible with flexible transistors made from cheap ferroelectret packing foam. Just as in ferromagnetic materials tiny magnetic dipoles become permanently oriented in the presence of an applied magnetic field, so in ferroelectric materials electric dipoles become permanently polarized by the application of an electric field. Ferroelectrets, a novel class of cheap electroactive materials based on cheap polymer foams, are often used as packing material and for thermal insulation.

But now physicists at the Johannes Kepler University (in Linz, Austria) and Princeton University (US) have shown that ferroelectret films can muster electric fields big enough to trigger (switch) a field effect transistor. Hence many of the things transistors are good for can be engineered using flexible, cheap ferroelectret materials as building blocks.

Already the researchers have demonstrated in the lab working versions of flexible touch-sensors and microphones. Ingrid Graz (ingrid.graz@jku.at) says that her new form of soft electronics could be useful for producing flexible paper-thin keyboards and flexible microphones for mobile phones, active noise control devices, toys, hearing aids, and surround-sound systems. (Graz et al., Applied Physics Letters, 14 August 2006)