Numerical simulation on the formation of a toroidal microvortex by the optoelectrokinetic effect

In this study, the formation of a toroidal microvortex by optoelectrokinetic effect was numerically simulated using COMSOL v4.2a multiphysics software. AC voltage was applied to the two parallel electrodes in a microchannel to generate temperature gradient in the fluids. In addition to the AC electrothermal effect, local heating by a laser illumination was also considered. Numerical simulations were conducted for dielectric fluids. The toroidal microvortex induced by the optoelectrokinetic effect shows that two counter-rotating vortices are produced above the bottom electrodes. Fluid motions in the middle of bottom boundary are cancelled out by flows in opposite directions and consequently producing stagnation. It is expected that micro/nano particles are deposited in bottom electrode. Local heating enhanced the intensity of microvortex substantially due to the additional temperature gradient, it was confirmed that the AC electrothermal effect with laser illumination can be used for rapid concentration of micro/nano particles in the spot area.