Propelling microobjects using a stationary DC voltage

We report a method for propelling microobjects under a DC voltage without switching the direction of the voltage. In this study, a stationary DC voltage (about 100 V) was applied to the microobjects (glass beads) in oil using ITO electrodes. The glass beads exhibited random or oscillatory motion when few beads less than four beads were placed between the electrodes; on the other hand, the mass of beads much more than four beads exhibited unidirectional motion as a group. This technique can be applied to transportation of microobjects under simple patterned-electrodes in microsystems without waveform generators.