Piezoelectric energy harvester using mechanical frequency up conversion for operation at low-level accelerations and low-frequency vibration

In this paper, we propose a modified frequency up-conversion mechanism to lower the operational acceleration level for energy harvesting devices using a snap-through buckling phenomenon. The proposed device consists of a buckled bridge beam clamped on flexible sidewalls with a proof mass and cantilever beams attached to the bridge. When subject to a vibration, the buckled bridge beam snaps through between two stable states, inducing impulsive acceleration on the attached piezoelectric cantilevers. During the snap-through transition, the flexible sidewalls deflect outward, thus lowering the threshold acceleration value for the state transition. Various sidewall materials with different flexibilities were tested to determine the maximum output power, bandwidth, and output characteristics for various input acceleration values. The minimum acceleration value for snap-through transition was 0.5g (g = 9.8 m/s²) when using latex sidewalls. A maximum output power of 0.4 mW Hz/cm²—that is 10 μW for test sample at an excitation frequency of 15 Hz—was generated by using the proposed device with latex sidewalls.