Development of Micro Solar Boat Employing Ion Drag Force

Abstract

A micro solar boat(MSB), a miniature boat of 1mm×0.8mm×0.15mm driven by a light beam, has been developed by use of wafer processing techniques of semiconductor devices. The driving principle, the fabrication processes of a micro solar cell and driving electrodes, and the result of sailing experiment are described. The driving force is created by the reaction from flowing liquid, the flow of which is generated by a drag force of ions in the liquid. To accelerate the ions in one direction by a low DC voltage, a pair of special electrodes and a particular liquid are used: an interdigitated elec trode has half-covered fingers, while the liquid contains molecules that can be both plus and minus ions. The body of the MSB was made of semi-insulating GaAs. On the front surface four micro solar cells connected in series were formed to provide the output voltage of over 3 V, and on the rear surface the driving electrodes were formed with fingers of 20μm width. Under illumination by a laser beam of 2.3mW, the MSB proceeded in an expected direction at the maximum speed of 6mm/min.