Dielectrophoresis (DEP) based on the processes of particle separation and particle detection in micro-channel is one of the most important operations required for many lab-on-a-chip devices. To understand the mechanism of the DEP, a theoretical analysis of dielectrophoretic separation motion of a spherical particle in a rectangular micro-channel filled with an aqueous electrolyte solution is presented in this paper. The dimensions of micro-channel are 100 μm in width and 200 μm in length. In this study, driven forces on the particle are analyzed in detail. At the gravitational direction, it is assumed that the density of the spherical particle is higher than that of the solution, and thus the gravitational effect is considered coupled with the buoyancy force and the electric double layer interaction force as well as the van der Waals force. Both the DEP force and the viscous friction force drive the particle separation motion from the solution in micro-channel. The particle separation distance of the particle from the bottom wall by the action of these forces and its motion behavior are analyzed and calculated. The DEP motion along the channel in an applied non-uniform electric field is simulated. Effects of particle’s size, electrolyte solution concentration and applied electric field strength on the DEP motion are discussed.

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