Electrokinetic motion of a deformable particle: dielectrophoretic effect.

Electrokinetics-induced motion and deformation of a hyperelastic particle confined in a slit microchannel has been numerically investigated for the first time with a full consideration of the fluid-particle-electric field interactions and the dielectrophoretic (DEP) effect. When the initial orientation of a cylindrical particle with respect to the applied electric field, θ(p0), is 90°, the particle tends to curl up as a "C" shape when moving from left to right. The electrokinetics-induced particle deformation is due to the joint effects of the shear force arising from the non-uniform Smoluchowski slip velocity on the particle surface and the asymmetric DEP force with respect to the center of the deformed particle arising from the spatially non-uniform electric field surrounding the particle. The electrokinetics-induced particle deformation is opposite to that of a particle moving in the same direction subjected to a pressure-driven flow. When the initial particle orientation is 0<θ(p0) <90°, a net torque arising from the DEP effect progressively rotates and aligns the particle with its longest axis parallel to the applied electric field, thus decreasing the non-uniformity of the electric field and accordingly the particle deformation. The numerical predictions are in qualitative agreement with our previous experimental observation. The results show that the DEP effect is significant and must be taken into account in the modeling of electrokinetic motion of a deformable particle in microfluidics.