Optimization a structure of MEMS based PDMS ferroelectret for human body energy harvesting and sensing

Abstract

A ferroelectret is typically a charge-storing cellular foam that demonstrates excellent piezoelectric properties making them potentially suitable for both sensing and energy harvesting applications. In this work we developed a numerical finite element analysis (FEA) model to describe ferroelectret materials and to further improve their piezoelectric properties. Using this FEA model, ferroelectret materials with rectangular and parallelogram void structure were designed and then fabricated by casting polydimethysiloxane (PDMS) in microfabricated silicon moulds. The piezoelectric properties and energy harvesting output of the fabricated PDMS ferroelectrets were both simulated and evaluated experimentally. For a single layer PDMS parallelogram void structure, the predicted piezoelectric coefficient d33 from the ANSYS simulations is around 320 pC N−1. The fabricated PDMS ferroelectret has a low Young’s modulus of 670 kPa and a piezoelectric coefficient of 240 pC N−1. A maximum d33 of 520 pC N−1 was observed in a multilayer ferroelectret structure. When applying compressive forces simulating a footstep, the material demonstrated an output power of 2.73 μW when connected to a 65 MΩ resistive load.