Successful construction of a simple sub-millimeter micromotor is reported, which operates under stationary direct current (DC) voltage, with neither a fixed rotational axis nor contacting brush. The screw-shaped chiral rotor undergoes a spinning motion when stationary DC voltage is applied using a pair of cone-shaped electrodes with a staggered arrangement. Analysis of the fluid motion revealed the occurrence of inward-swirling flow in between the electrode tips, which generates a stable spinning motion under the DC voltage. This simple DC micromotor could be beneficial for the advancement of microfluidics, microrobots, etc.
