Piezoelectricity of a single bubble formed by two oppositely charged Teflon® -FEP films

Multi-void space-charge electrets that have been formed by two fluoroethylenepropylene (Teflonreg-FEP) films with internal surface charge layers of opposite polarity exhibit high piezoelectric coefficients. In these electrets, several charged bubbles are arranged in parallel. A significant voltage is generated between the electrodes when the arrangement is submitted to a mechanical force that acts perpendicular to the electrodes (direct piezoelectricity). The arrangement thus works in a similar manner as a large number of tiny electret microphones. In view of this mechanism, the size and the shape of the bubbles are important aspects for the design of sensor and actuator devices. In this paper, we therefore investigate the behavior of single air bubbles formed by two fluoroethylenepropylene (Teflonreg-FEP) films theoretically and experimentally.