Optically-Powered Microscopic Bubble Rockets

Artificial microswimmers have attracted great interest recently, especially for applications in sensing and biology. In particular, micro-propulsion by producing bubbles using decomposition of a chemical fuel is an attractive method, but it requires a fuel source. In this talk, we demonstrate a new optically-powered approach to catalyst-free bubble self-propulsion that works in a broad range of fluids, including deionized water. These devices, approximately 100 microns in size, consist of encapsulated silicon photodiodes connected in series with two external electrodes. Under standard illumination conditions in a microscope, the photovoltaics drive water splitting at the electrodes and eject the resulting bubbles preferentially in one direction, propelling the device through fluid. These devices are fabricated and released in parallel using standard semiconductor technologies. We discuss the fabrication and characterization of these devices, demonstrate working bubble rockets, and discuss their efficiency and potential applications.