Micron scale energy harvesters using multiple piezoelectric polymer layers

Abstract

This paper presents the design, fabrication, and experimental results of micron scale energy harvesters that utilize piezoelectric polymer polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE). Proposed devices are free-standing thin film cantilevers with multiple PVDF-TrFE and electrode layers. During the design phase, optimal piezoelectric layer thickness for the chosen substrate was calculated as 7.4μm. In order to alleviate the potential fabrication problems, a multilayer approach was adopted instead of coating a single layer. Device dimensions were selected to yield resonance frequencies below 1kHz. Cantilever type piezoelectric energy harvesters with 3 parallel-connected PVDF-TrFE layers were created using standard microfabrication techniques. Energy harvesting performances of the fabricated devices were evaluated using an electrodynamic shaker and an accelerometer to create and observe input vibrations at different amplitudes and frequencies. Measurement results were compared with theoretical calculations and the effect of substrate clamping was discussed. The power output of a (1800μm×2000μm) prototype was measured as 0.1μW when driven with a peak input acceleration of 1.0g at its resonance frequency of 192.5Hz. Half power bandwidth of the same prototype was measured as 2.9Hz. Proposed energy harvesters have relatively low resonance frequencies for their sizes and have the potential to be easily integrated with other microfabricated devices.