Trench-filled cellular parylene electret for piezoelectric transducer

Cellular ferroelectrets with charged voids are promising for piezoelectric transducers, but the long-term stability or reproducibility due to the conventional “stochastic” fabrication and the corona charging methods is of concern. We microfabricated a high-density cellular piezoelectret with high-aspect-ratio polymer structures based on the trench-filled parylene technology. Vertical walls of the parylene structures are charged using soft x-ray to realize uniform artificial dipoles, of which moments could vary along with parylene structural deformation driven by the inertia of a seismic mass. Charge and voltage sensitivities of 9600 pC/N and 960 V/N with respect to the in-plane resonant oscillation have been achieved at 149 Hz, respectively.