Novel energy harvesting using acoustically oscillating microbubbles

When a bubble hanging on a piezocantilever is excited by an acoustic wave around its resonant frequency, it oscillates and simultaneously generates cavitational microstreaming around it. The microstreaming bends the piezocantilever with fine vibration, resulting in electric power generation from the piezocantilever. In this study, we explore the dynamic behaviors of an acoustically oscillating bubble on the flexible substrate as well as demonstrate applicability of the proposed system to practical applications such as energy harvesting and acoustic wave sensors. First, the effects of an applied frequency and bubble size on the dynamic characteristics of an acoustically oscillating bubble, such as maximum amplitude and resonant frequency, are experimentally investigated. The amplitude of an oscillating bubble is maximized at its resonant frequency, which is inversely proportional to its size. In addition, electrical voltage generated by a piezocantilever attaching with an oscillating bubble is measured at different applied frequencies, bubble sizes, and distances between the bubble and piezoactuator. The results show that the generated voltage is strongly affected by the applied frequency and is inversely proportional to the bubble size and the distance between the bubble and piezoactuator. Finally, the output voltage is almost linearly proportional to the number of bubbles.