Piezoelectric PDMS electrets for MEMS transducers

We have successfully demonstrated the fabrication of piezoelectric PDMS electrets utilizing foam forming and micro plasma discharge processes. To acquire electromechanical sensitivity, PDMS foams with micrometer-sized closed cells are implanted with positive and negative charges on the opposite internal surfaces of each cell, which behaves just like a dipole. In the prototype demonstration, PDMS foams with nanoparticles or polymers coated internally are fabricated and charged under electric fields up to 30 MV/m. The resulting PDMS electrets show an elastic modulus of 370 kPa and a piezoelectric coefficient (d₃₃) up to 106 pC/N, which is more than 5 times higher than that of common piezoelectric polymers (e.g., PVDF). As such, the demonstrated piezoelectric PDMS electrets could serve as soft and sensitive electromechanical transducers, which are desired for a variety of MEMS applications.