Asymmetric electrode design for significant performance enhancement of piezoelectric P(VDF-TrFE) polymer microcantilevers

Abstract

A concept of utilizing asymmetric electrode structures for significantly enhancing the performance of piezoelectric polymer microelectromechanical systems is proposed. Piezoelectric poly(vinyl difluoride-trifluoroethylene) (P(VDF-TrFE)) polymer micro unimorph cantilevers with different thicknesses of the top and bottom metallic electrodes are designed and investigated. Both the analytical calculations and finite element simulations show that a large shift of the neutral axis away from the center of the active piezoelectric P(VDF-TrFE) layer can be realized by the adoption of top and bottom metallic electrodes with different thicknesses. The neutral axis shift due to the asymmetric electrode thicknesses is greater for piezoelectric polymer materials due to the lower Young’s moduli. It was shown that superior performance could even be achievable with a softer P(VDF-TrFE) cantilever with asymmetric electrode thicknesses over a cantilever using a piezoelectric ceramic layer with a much stronger piezoelectric effect. The feasibility of fabricating the P(VDF-TrFE) polymer micro cantilevers with asymmetric electrode thicknesses was demonstrated with a surface micromachining process.