Theoretical analysis and experimental validation of frequency-moldable electrostatic energy harvesters biased with a high elastic electret film

Abstract

It is an effective strategy to improve the power output of energy harvesters by adjusting resonance frequency of the devices to adapt to complex frequency distribution of vibrations in environments. This paper presents mechanical analysis and experimental validation of a kind of light-weighted, flexible electrostatic vibrational energy harvesters with a customizable resonance frequency range. Such energy harvester consists of a stretchable electret beam, whose high elasticity was achieved by introducing a corrugated structure, an arc-shaped counter electrode, and a light seismic mass. The resonance behavior of the device can be simulated by the corrugated beam with flexible support at both ends. Mechanical analytical modeling allows one to predict resonance frequency of energy harvesters, making the devices potentially interesting for customizable resonance harvesting and broad bandwidth energy harvesting, and thus to satisfy actual application scenarios. The experimental results are in agreement with the theoretical prediction. For a device with an initial size of 15 × 10 × 9 mm3 and a seismic of 0.06 g, by modulating the length of the fluorinated polyethylene propylene electret beam from 15 to 35 mm, a customizable resonance frequency ranging 14–60 Hz, and the normalized output power up to several 100 μW was achieved, demonstrating great superiority.