Abstract
Multi-vibrational-mode electrostatic energy harvesters are designed and micro-machined utilizing a simple silicon-on-insulator (SOI) wafer-based process. Enhanced adaptability to various vibrational environments is achieved in the proposed design by using serpentine springs attached to the fishbone-shaped inertial mass. The experimental results show that the developed device could convert an input vibration of 6 g at 1272 Hz to 2.96, 3.28, and 2.30 μW for different vibrational directions of 0°, 30°, and 45° with respect to a reference direction, respectively, when all serpentine springs are identical. An alternative device design using serpentine springs with different stiffnesses between x- and y-axes exhibited resonance frequencies at 1059 and 1635 Hz for an input vibrational direction of 45° and acceleration amplitude of 4 g, successfully generating 0.723 and 0.927 μW of electrical power at each resonance, respectively.