Bio-inspired bi-stable piezoelectric harvester for broadband vibration energy harvesting

Inspired by the rapid shape transition of the Venus flytrap, a novel low-cost, bi-stable piezoelectric energy harvester is proposed, analyzed, and experimentally tested for the purpose of broadband energy harvesting. The harvester consists of a piezoelectric macro fiber composite (MFC) transducer, a tip mass, and two sub-beams with bending and twisting deformations created by pre-displacement constraints at the free ends using rigid tip-mass blocks. Different from bi-stable harvesters realized by nonlinear magnetic forces or residual stresses in laminate composites, the bio-inspired bi-stable piezoelectric energy harvester stores the potential energy induced by the mutual self-constraint of the sub-beams and harvests the large energy released during the rapid shape transition. Detailed design steps and principles are introduced and a prototype is fabricated to demonstrate and validate the concept. The experimentally measured nonlinear force-displacement curve of the harvester exhibits a discontinuous feature as the harvester jumps between the stable states. The dynamics of the proposed bio-inspired bi-stable piezoelectric energy harvester is investigated under sweeping frequency and harmonic excitations. The results show that the sub-beams of the harvester experience local vibrations including broadband high-frequency oscillations during the snap-through. The energy harvesting performance of the harvester is evaluated at different excitation levels over the frequency range of 9.0-14.0 Hz. Broadband energy harvesting is attained at relatively high excitation levels. An average power output of 0.193 mW for a load resistance of 8.2 k is harvested at the excitation frequency of 10 Hz and amplitude of 4.0 g.