Dielectrophoretic motion of two particles with diverse sets of the electric conductivity under a uniform electric field

Abstract

In this paper, we have numerically studied two-dimensional dielectrophoretic motion of two identical particles with diverse sets of the electric conductivity suspended freely in a viscous fluid under an externally applied uniform electric field. For the study, we solve the Laplacian equation with a large sharp jump in the conductivity at the particle–fluid interface for the electric field (potential) and integrate the Maxwell stress tensor to compute the dielectrophoretic force acting on each particle, while we solve the continuity and Stokes equations for the flow field. For the simulations, we develop a finite-volume based numerical approach, where a sharp interface method is adopted for the solution of the electric field and a direct-forcing based immersed-boundary method is for that of the flow field. Results show that the dielectrophoretic motion of two particles depends significantly on their relative magnitudes of the conductivity compared with the fluid. When both particles have conductivity higher or lower than the fluid although their values differ from each other, they revolve, while repelling or attracting each other depending on their configuration, and finally get aligned in a line with the electric field. When either of both particles has conductivity higher than the fluid and the other has lower one, on the other hand, they revolve in the opposite direction and finally get aligned in a line perpendicular to the electric field. In addition, the motion becomes further strengthened as the conductivity of either of the particles increases above or decreases below that of the fluid, but the trajectories taken by them are not affected so significantly by their set of the conductivity except for the revolution direction.