Electromechanical response of cellular electret films

Charged polypropylene films with a cellular structure show pseudopiezoelect ric properties. Measurements of the direct and inverse electromechanical tr ansducer constants of such films, relating to the operation as sensors and as actuators, respectively, yield values of approximate to 200 pC/N. These values can be explained with a theoretical model by assuming reasonable cha rge distributions and charge densities. The experimental and the theoretica l results show the reciprocity of the transducer constants. (C) 1999 Americ an Institute of Physics. [S0003-6951(99)02646-7].