Optothermally pulsating microbubble-mediated micro-energy harvesting in underwater medium.

Despite the considerable research interest due to practical importance of pervasive wireless sensing systems in a wide range of engineering fields, power management remains an arduous task for further development of pervasive wireless sensing systems due to inherent needs for self-reliant functionality and portability during their operations. To this end, we here propose a new type of energy harvesting strategy in which an optothermally pulsating microbubble is submerged in an underwater medium. The pulsating microbubble gives rise to the periodic vibration of piezocantilevers in contact, which resultantly can produce electrical outputs. On the basis of this simple idea, mechanical power can be extracted from light energy through optothermally pulsating microbubbles in an aqueous medium and subsequently the mechanical power can be converted to electrical power for wireless devices. To elucidate physical factors affecting the performance of the proposed strategy, we thoroughly explore the effect of the intensity and frequency of the laser beam on the pulsation amplitude of optothermally pulsating bubbles and subsequent electrical outputs (e.g., electrical voltage and power). The dependence of electrical output on wetting property of piezocantilevers and electrical resistance is also established. The present work would provide a new framework for fundamental design of bubble-based microactuators as energy harvesters and microsensors in the near future.