Flexoelectricity as a universal mechanism for energy harvesting from crumpling of thin sheets

Can the mere crumpling of a paper produce electricity? An inhomogeneous strain can induce electrical response in all dielectrics and not just piezoelectric materials. This phenomenon of flexoelectricity is rather modest unless unusually large strain gradients are present. In this paper, we analyze the crumpling of thin elastic sheets and establish scaling laws for their electromechanical behavior to prove that an extremely strong flexoelectric response is achieved at submicron length scales. Connecting with recent experiments on crumpling of a polymer paper, we argue that crumpling is a viable energy-harvesting route with applications in wearable electronics and related contexts.