A Novel Miniaturized Electroosmotically-driven Micromixer Modified by Surface Channel Technology

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 canbe particularly troublesome, due to low Reynolds number in micro-scale and also, this problem is compounded by the factthat small channel fabrication is another challenge for designing micro-electromechanical systems. In this paper a novel technique of microchannel fabrication with silicon nitridewalls based on surface micromachining is modified to an electroosmotically-driven micromixer. During the fabricationprocess, 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 theresulting electroosmosis perturbs the low Reynolds number flow. FE-Analysis shows that the micromixer with coveredelectrodes provides the high mixing efficiency of 80% for a 64μm long microchannel. On the other hand this layer canreduce 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 offolding and stretching in the microchannel indicate the chaotic mixing.