22am2-E2 ステンレス箔振動子を用いた静電誘導型の振動発電素子の発電量向上の検討

Abstract

This research reports a robust oscillator fabricated from a fine-grained stainless steel and optimization of output power in out-of-plane electrostatic vibration energy harvesters. The oscillator (area: 4 cm^2) showed shallow side-etched depth less than 10 μm and thus ideal vertical vibration. We numerically evaluated output powers and resonance frequencies with changing initial air gaps by simultaneously solving equation of motion and Kirchhoff's law. Applied acceleration is 0.5G. The output power increased with decreasing initial air gap and then exhibited a peak value of 25 μW at 0.6-mm air gap, whereas the resonance frequency decreased. The reason for the resulting peak is that stronger electrostatic force less than 0.6-mm air gaps reduces amplitude of the oscillator and thus the variation of capacitance. The decreased resonance frequency may be attributed to the soft spring effect by stronger electrostatic force.