Controllable high speed rotation of nanowires and micromotors

We report a versatile method for executing controllable high-speed rotation of nanowires by an AC electric field applied to strategically designed multiple microelectrodes. The rotation of the nanowires can be instantly switched on or off with precisely controlled rotation speed (to at least 1800 rpm), definite chirality, and total angle of rotation. We have determined the viscous torque due to the fluidic drag force on nanowires of different lengths at extremely low Reynolds numbers on the level of 10-5, which is not theoretically well known. We have also demonstrated a micromotor using a rotating bent nanowire driving a dust particle into circular motion. This method has been used to rotate magnetic and nonmagnetic nanowires as well as multi-wall carbon nanotubes. The relevance to microfluidic devices, microstirrers, and micro-electromechanical systems ［8］ is apparent.