Mixing Process and Flow Structure in Electrokinetic Micromixer with Rough Walls- A Study on Rough Geometry

In this study, the flow structure and efficacy of electrokinetic micromixer with rough walls is investigated using a numerical method. The main purpose is to use both active and passive methods of electrokinetic and wall roughness to further improve the performance of the micromixer. Surface roughness can be used to disrupt the flow and create perturbation and ultimately improve the performance of the micromixer. COMSOL Multiphysics 5.6 software is employed to simulate the problem. The effects of type of roughness geometry, direction of wall roughness, and electric field intensity on the mixing effectiveness of the proposed micromixer are analyzed. The results show that for the case of micromixer with the smooth walls, the mixing effectiveness parameter is only 53.4%, while by using the roughness on the walls, the mixing effectiveness parameter is improved considerably. The micromixer with the oblique-angled triangle roughness with the mixing effectiveness parameter of 73.7% has the best mixing effect among the other cases. For the case of roughness with non-equilateral triangle shape, the mixing effectiveness parameter increases significantly and is about 70.5%, and for the case of roughness with right-angled triangle shape, it is about 72.5%. The direction of wall roughness has negligible effect on the mixing effectiveness parameter. By using the roughness on the micromixer walls, the average velocity at the output of the micromixer is decreased. The mixing effectiveness parameter increases with decreasing the exerted electric field from 200 Volt/cm to 50 Volt/cm. For the case of micromixer with oblique-angled triangle roughness, there is no necessity to consider a lengthy channel and the effective length of the mixture is not long (almost 1500 mu m).

Automated summary

This study investigates the flow structure and efficacy of an electrokinetic micromixer with rough walls using a numerical method. It shows that adding roughness to the walls improves the mixing effectiveness significantly, with different roughness shapes having different effects. The direction of wall roughness has a negligible effect on the mixing effectiveness, and decreasing the electric field intensity also increases the mixing effectiveness.