Flexoelectric electricity generation by crumpling graphene

Abstract

We utilize atomistic simulations that account for point charges and dipoles to demonstrate that flexoelectricity, which arises from strain gradients, can be exploited to generate electricity from crumpled graphene sheets. Indentation of a circular graphene sheet generates localized developable (d)-cones, for which we verify the core radius and azimuthal angle with established theoretical models. We determine the voltage that can be generated based on the resulting electrostatic fields and compare the voltage generation to previous theoretical predictions that are scaled down to the nanoscale. In doing so, we find that the voltage generated from crumpling graphene exceeds, by about an order of magnitude, the expected voltage generation, indicating the benefit of exploiting the large strain gradients that are possible at the nanoscale. Finally, we demonstrate that crumpling may be a superior mechanism of flexoelectric energy generation as compared to bending of two-dimensional nanomaterials.