Complementary multi-mode low-frequency vibration energy harvesting with chiral piezoelectric structure

This letter proposes a complementary multi-mode low-frequency vibration piezoelectric energy harvester (PEH) which is mainly composed of three chiral folded beams in a light hexagonal matrix. The chiral structure can be constrained in two typical boundary conditions, each of which results in two different natural modes according to different effective stiffnesses. Numerical simulation and experimental results verified this property and found that the frequency responses are complementary for two PEH units with different boundary conditions. By connecting these two units electrically, the frequency bandwidth can be broadened by producing total four resonant peaks. Furthermore, external magnetic force was introduced to enable tuning of the frequency response. The proposed PEH with tunable multi-mode properties has potential applications in practical low-frequency vibration environments.