Dielectrophoretic forces on particles in travelling electric fields

Computations are presented of the fields and forces experienced by dielectric uncharged particles subjected to travelling electric fields. The results provide an improved understanding of the various electrokinetic effects observed for particles exhibiting travelling wave dielectrophoresis, either over microelectrode structures or in channels between electrodes. The real and imaginary components of the complex dipole moment induced in a particle are found to be independently acted upon by the imposed electric field, producing both a trapping force and a translational force. The overall electrokinetic behaviour of a particle is determined by the combined effects of these two competing forces, and is a sensitive function of the dielectric properties of the particle and of the frequency of the applied travelling field. Effects produced by different electrode geometries and applied voltage signals are investigated, and these provide insights into possible practical applications.