An acoustically oscillating droplet induced motion-powered energy harvester: (a) When a water droplet is acoustically excited by a piezoactuator around its natural frequency, it oscillates; (b) When an acoustically oscillating droplet is placed on the tip end of a piezocantilever, the oscillating motion of the droplet induces the continuous bending of the piezocantilever as the reaction, resulting in electric power generation from the piezocantilever. The envisioned energy harvesting system can extract mechanical power from acoustic noise over a wide range of frequencies using liquid droplets with different sizes and natural frequencies and convert the mechanical power to electrical power for wireless electronic devices. This new type of actuation technique is a simple but useful tool not only for energy harvesting systems but also for potential acoustic wave sensors and actuators in the future.