This paper reports a microfluidics-based lab-on-a-chip device combining the alternating current (AC) dielectrophoresis (DEP) and pressure-driven flow for separation of particle/cell mixtures. The dielectrophoretic separation is achieved by a hybrid design using a PDMS (poly-dimethylsiloxane) hurdle and a pair of embedded metal electrodes to generate localized non-uniform AC electric field. Since the particles and the cells are transported through the small DEP separation region, the negative effects associated with the Joule heating and exposure to the electric field have been significantly reduced. Mixtures of polystyrene particles of different sizes and yeast cells with polystyrene particles were successfully separated at AC electric field of 200 kHz. (C) 2008 Elsevier Ltd. All rights reserved.