Sound Energy Harvester with Frequency Tunable Acoustic Metamaterial Cavity

Abstract

We demonstrate a new type of acoustic harvester by utilizing an acoustic metamaterial cavity designed by double coiledup space like structures. In the case of double coiled-up metamaterials, high refractive index (n) miniaturizes the device at the subwavelength scale and high impedance (z) leads to efficient sound amplification rate inside the cavity, respectively. These miniaturized cavities enable to enhance the energy-convergence rate of acoustic harvester. When the resonant frequency of acoustic cavity coincides with the 1st natural frequency of the piezoelectric harvester, the amplification of sound pressure with 16dB sound pressure level gain leads to efficient acoustic mechanical-electrical conversion rate. Compared to acoustic harvesting method with only piezoelectric devices, experimental results illustrate that the proposed techniques exhibit six-time higher voltage output.