Piezoelectric sensor based on electret thermoforming technology

Teflon FEP thermoformed piezoelectric transducers based on electret technology, which were introduced in 2005, basically consist of the fusion of two Teflon FEP films, creating air bubbles at the interface. The top and bottom of the air bubble surfaces are posterior charged to opposite polarities, forming large electric dipoles. Although this technology has enabled the production of transducers with piezoelectric coefficients above 300 pC/N, it is still in the laboratory stage. This paper proposes some improvements through a new methodology whereby the molding of one of the Teflon FEP films in a template is followed by fusion by hot lamination. This method enables control of the distribution and diameter of the bubbles and the production of piezoelectric transducers for specific applications such as presence sensors, thin keyboards, dynamic balances and pressure sensors.