Using Low Frequency Electrical Signals for Particle Separations with Dielectrophoresis

In insulator-based dielectrophoresis (iDEP), particles are trapped and immobilized when the dielectrophoretic force acting on them dominates over other transport mechanisms, such as by electroosmotic flow (EOF). Thus, particles are released from the “dielectrophoretic” raps when EOF dominates over the DEP. Cyclical electrical signals were used to reduce and fine tune EOF transport by allowing iDEP separations using lower applied electric potentials than reported before. The cyclical signals reduced net EOF since EOF direction depends on the electric field direction. DEP direction does not change with the direction of the electric field, and was not weakened by a cyclical signal. Polystyrene spheres of different sizes were separated in a microchannel with cylindrical insulating structures 450 µm diameter and spaced 500 sym center to center. Initially, a sinusoidal signal between +400 and -400 V was applied, and minimum value was gradually increased, while the maximum value was kept constant at +400 V. This method achieves iDEP separations at lower applied voltages than those reported in previous work for similar particle mixtures.