A multilayer PVDF composite cantilever in the Helmholtz resonator for energy harvesting from sound pressure

Although acoustic energy sources are an excellent alternative energy resource for harvesting, studies on harvesting such sources have been rarely investigated because of their lower energy density compared to other resources. For the purpose of efficient acoustic energy harvesting, this study presents a Helmholtz resonator with single-layer and multilayer piezoelectric composite cantilevers. A flexible PVDF piezoelectric composite cantilever is employed in this study due to the simple adjustment of its resonance to the acoustic resonance of the Helmholtz resonator. A multilayer PVDF composite cantilever is considered to improve the power harvested compared to a single-layer harvester. These approaches are investigated and verified by theoretical analysis including finite element simulations and experiments. The results of the current feasibility study show a maximum power of 0.19 μW (0.12 μW cm−2) with sound waves of 15 Pa (∼118 dB) at 850 Hz, which can be increased by a factor of 2.3 by adopting the structure of a four-layer PVDF composite cantilever. Theoretically, around seven times more power would be available using the optimal design of a twenty-layer composite structure compared to that of a single-layer composite acoustic energy harvester. Finally, the results of this study can be used in various applications for power generation by means of absorbing and eliminating specific frequency bandwidths of noise in continuously noisy environments.