Geometrically polarized architected dielectrics with apparent piezoelectricity

Abstract

Through the suitable geometry of a repeating unit, a metamaterial can exhibit a property not present in the base material. Here, we propose a class of low area-fraction, bending-dominated metamaterials that exhibit apparent piezoelectricity, even though the base material is not piezoelectric. The proposed metamaterials exploit a universal electromechanical coupling operative at sub-micron scales, flexoelectricity, and upscale it to the macro-scale through geometrically-polarized material architecture. We quantify the apparent piezoresponse thanks to accurate simulations of continuum flexoelectricity. We characterize how apparent piezoelectricity depends on lattice geometry, orientation, feature size and area fraction. We find that if the base material is a good flexoelectric, then our low area-fraction designs exhibit piezoelectric couplings comparable to the best piezoelectric ceramics in bulk. More generally, our work provides the rules to endow any dielectric metamaterial with apparent piezoelectricity, hence enabling non-toxic, environmentally friendly and biocompatible materials for electromechanical transduction.