An experimental and theoretical study is described concerning the dielectric motion of particles in a suspension subject to high-gradient AC electric fields. The experiments were performed on very dilute suspensions of polystyrene latex beads in DI water. Several experiments were run using channels designed with Sandia National Laboratories' SwIFT/sup /spl trade// (Surface Micromachining with Integrated Fluidic Technologies) process. The SwIFT/sup /spl trade// process allows for the closest spacing of electrodes achievable using photolithographic patterning. A sinusoidal AC electric field was applied between two electrodes using 10 V peak-to-peak (ptp) and 30 MHz. Negative dielectrophoresis is observed with particles moving towards the low field gradient. The Computational Fluid Dynamics Research Corporation Code (CFDRC) was used to calculate the field gradient. Particle polarizability was calculated by measuring the concentration dependence of the permittivity at specified frequencies using an impedance analyzer.