Mechanical metamaterial piezoelectric nanogenerator (MM-PENG): Design principle, modeling and performance

Abstract

Piezoelectric nanogenerator (PENG) has been reported as a green energy solution that generates electrical power from mechanical deformations resulted in the environment. Here, a novel design concept of PENG is reported based on mechanical metamaterials (MM). Plate-like MM with piezoelectric materials is designed in a sliding cell such that low frequency excitations causes structural instability (i.e., postbuckling) of the piezo-MM and thus, the piezo layer is triggered to generate electrical power. In this process, the environmental input (<1Hz) is converted into mechanical energy through the postbuckling behavior of the MM, and the mechanical energy is transformed into electrical power by the piezo layer. Nanoscale hexagonal MM is fabricated and tested, and the spin-coating technique is introduced to grow the piezo layer (e.g., PVDF-TrFE) on the MM. Analytical models are developed to obtain the electrical power generated by the MM-PENG. Numerical simulations are conducted to validate the theoretical predictions and satisfactory agreements are obtained. Parametric studies are carried out to investigate the influences of the pattern ratio, geometric ratio and scaling ratio on the output electrical power. In the end, we outlook that the MM-PENG opens an exciting path to green energy by generating electrical power for multifunctional applications. Keywords: Piezoelectric nanogenerator (PENG), Plate-like mechanical metamaterials (MM), Bilaterally sliding constraints, Mechanical energy harvesting, Low-frequency excitations