A novel miniaturized electroosmotically-driven micromixer modified by surface channel technology

The more miniaturization of the Lab-On-a-Chip devices such as micromixer, micropump and so on, is the goal of this study. For microfluidic applications, mixing process can be particularly troublesome, due to low Reynolds number in micro-scale and also, this problem is compounded by the fact that small channel fabrication is another challenge for designing micro-electromechanical systems. In this paper a novel technique of microchannel fabrication with silicon nitride walls based on surface micromachining is modified to an electroosmotically-driven micromixer. During the fabrication process, electrodes are covered by a thin silicon nitride layer. The influence of silicon nitride layer on mixing efficiency is investigated. A time dependant electric field is applied and the resulting electroosmosis perturbs the low Reynolds number flow. FE-Analysis shows that the micromixer with covered electrodes provides the high mixing efficiency of 80% for a 64µm long microchannel. On the other hand this layer can reduce the high electric gradient created at sharp points and edges of the electrodes. The exponentially separation of the two close particles, during the mixing process and generation of folding and stretching in the microchannel indicate the chaotic mixing.