Evaluation by fast Fourier transforms analysis of energy harvesting in electrostrictive polymers driven by an electric field and a mechanical excitation

Electrostrictive polymers offer the promise of energy harvesting with few moving parts where power can be produced simply by stretching and contracting a relatively low-cost rubbery material. The use of such polymers for energy harvesting is a growing field, which has great potential from an energy density viewpoint. Basically, the relative energy gain depends on the current induced by the mechanical strain and frequency. A previous study in the Laboratoire de Génie Electrique et Ferroélectricité laboratory has indicated that one can measure the dielectric constant, the Young's modulus, and the electrostrictive coefficient of a polymer film by determining the current flowing through the sample when the polymer film was simultaneously driven by an electrical field and mechanical excitation. The goal of this study has thus been to develop a solution for artificially increasing the coupling factor of electrostrictive materials, based on the optimization of the frequency of the electric field and the amplitude strain of the mechanical excitation leading to an increase in the generated current. When relating this parameter with a transverse strain of 5% and a bias field of 10 V/μm, it was found that such a process rendered it able to increase the converted power to 14 μW at a mechanical frequency of 6 Hz. The converted power was much higher than for the frequency of 3 Hz for which a low power was consumed by the polarization of the polymer. The theoretical analysis was supported by the experimental investigations. The contribution of this study provides a framework for developing energy harvesting techniques that should improve the overall performance of the system.