A New Scheme for Improving the Mixing Efficiency in Micro Scale

Generally speaking, most micro-fluidic mixing systems are limited to the low Reynolds number regime in which diffusion dominates convection, and consequently the mixing process tends to be slow and it takes a relatively long time to have two fluids completely mixed. Therefore, rapid mixing is essential in micro-fluidic systems. In order to hasten the mixing process in micro scale, in this study we come up with a novel scheme for a two dimensional micro-fluidic mixer which encompasses three pairs of electrodes, one pair embedded in the mixing chamber and two pairs located in the micro-channels before and after the mixing chamber. The width of the middle pair is assumed to be twice of the other pairs. In addition, the fluids enter the device via two different entrances within a T-junction. The width of all micro-channels is equal to 50 micrometer and the whole mixer is less than 1 millimeter in length. While Electrical potentials are applied to three electrodes in the outlet and inlet ports in order to conduct the fluids within the mixer, the chaotic electrical fields applied to the mixing chamber are derived by the Duffing-Holmes nonlinear system. We numerically simulate the performance of our micro-mixer by solving Navier-Stokes and continuity equations for fluid velocity field, Poisson-Boltzmann equation for describing the electrical double layer potential distribution, Laplace equation for the externally induced electrical field distribution and concentration transport equation in order to obtain the concentration distribution of two fluids within the geometry. Then, the mixing efficiency is calculated in the outlet cross section of the mixer and the results indicate that a mixing performance efficiency of up to 98% is obtainable by utilizing this proposed scheme.