A collision impact based energy harvester using piezoelectric polyline beams with electret coupling

In this work, a hybrid energy harvester is proposed to broaden the working bandwidth of vibration energy harvesting. This design consists of two piezoelectric polyline beams standing with a gap distance, of which one is bonded with a piezoelectric patch and covered by an electret layer, while an electrode covers the other. The two polyline beams are coupled through the electret and electrode effect, which is beneficial for extending the working bandwidth. The motion with which the two beams bump into each other could extend the harvester's working bandwidth in the low-frequency area. If replacing the second beam with an inverted beam, the working bandwidth will also be extended. To understand the underlying mechanisms and compare their performance, corresponding theoretical and experimental studies are carried out. The results show that the proposed harvester consists of two polyline beams that possess broader bandwidth with the coupling and collision impact design. Parameter analysis of the tip mass position on the auxiliary beam is conducted. The proposed hybrid energy harvester excited by stochastic excitation could generate an output power of 69.1 µW under an excitation level of 0.0041g2 Hz-1 with an active surface area of 280 mm2.