Contactless capturing of particles in liquid using pulsed alternating dielectrophoresis

Dielectrophoresis is an effective method for manipulation of particles in a medium, which can be achieved by applying electrical potentials to appropriately arranged electrodes. In the case of positive dielectrophoresis, the particles will move to regions of strong electric field and be captured at the edge or the surface of the electrodes, usually. The drawback thereby is that the particles may attach to the electrodes, leading to unwanted side effects. Negative dielectrophoresis moves them away from high field regions. In this article, the authors present a new method for contactless capturing of particles by using pulsed alternating dielectrophoresis. A signal sequence consisting of two pulsed ac voltages of different frequencies is applied to the electrodes. Each of them generates either positive or negative dielectrophoresis, respectively. With appropriate settings of dwell times and amplitudes, the particles are attracted toward the electrodes without attaching to them. Furthermore, the average distance from the electrodes can be tuned. Their experiments show that latex beads could be kept at a distance of up to about 20 mu m from the electrodes. (c) 2006 American Vacuum Society.