Flexural wave energy harvesting by multi-mode elastic metamaterial cavities

Abstract

In this paper, we design the elastic metamaterial cavities with multiple cavity modes for harvesting the flexural wave energy. The metamaterial plate is formed by drilling periodic holes in a thin aluminum plate, which exhibits a flexural wave mode band-gap. The metamaterial L1–L4 cavities are designed. The flexural waves are highly confined inside these metamaterial cavities due to the existence of the band-gap. The designed cavities can be utilized to confine and convert the mechanical wave energy to electricity for more than one cavity mode. To experimentally validate the multi-mode cavity design, a metamaterial L3 cavity is fabricated. The three cavity modes of the L3 cavity are observed experimentally, which agrees well with the numerical prediction. Three piezoelectric discs are attached in the metamaterial L3 cavity as the energy harvesters. The electrical outputs are measured to evaluate the performance of the metamaterial energy harvester. Compared to the reference harvester on a bare plate, the average power outputs are amplified by the metamaterial L3 cavity at three resonant frequencies. For the optimal resistance load, more than 40 times of the power amplification is achieved by the L3 cavity energy harvester. As prior energy harvesters based on a metamaterial cavity are usually efficient only for a single frequency, the multi-mode metamaterial cavity design can effectively widen the frequency bandwidth of the energy harvester.