Piezoelectricity of multi-layers space-charge electrets from Teflon FEP film with homogeneous voids distributed on its surface

The development of new cellular and porous polymers has introduced new advances on the study of the piezoelectricity characteristics of electric charged polymers. Recently, a multi-layer space-charge electret was also fabricated using at least one "soft" porous and one "hard" nonporous Teflon PTFE film assembled in various multi-layer stacks. Now, in this paper we propose a new multi-layer space-charge electret fabricated using at least one Teflon-FEP film with small voids homogeneously distributed on its surface. The device has the same concept of the electret microphone mechanism. When these multi-layer setups are charged by impulse voltage process, it is possible to obtain samples with high piezoelectric coefficients. Controlling the size of the voids on the film interface, we can obtain a better control of the charging processes and, can determine a better value of the charging impulse voltage.