Acoustically Excited Oscillating Bubble on a Flexible Structure and Its Energy-Harvesting Capability

Abstract

When a bubble oscillates under the action of an acoustic field, it generates a cavitational microstreaming flow around it. We here explore oscillation dynamics of a bubble hanging on a flexible structure (i.e., piezocantilever) by acoustic excitation, and assess the suitability of the proposed method to micro-energy harvesting systems. We preferentially investigate the characteristics of bubble oscillation, such as the maximum amplitude and resonant frequency by varying the applied frequency and bubble size. The amplitude of the oscillating bubble is found to be maximized at the resonant frequency depending on the bubble size. Additionally, we measured the electrical outcome generated from bubble oscillation-induced microstreaming and resultant vibration of the piezocantilever, as functions of the applied frequency, bubble size, and distance between the bubble and piezoactuator. The generated voltage is considerably dependent of the applied frequency and bubble size. Meanwhile, it is inversely proportional to the distance between the bubble and piezoactuator. Finally, we found that the electrical output can be can be improved by increasing the number of bubbles. This work will provide a new framework for the fundamental design of bubble-mediated micro-energy harvesters and microsensors.