Geometric modifications to simple microchannel design for enhanced mixing

The ability to control mixing of reagents in MEMS systems is crucial for many biological and chemical analysis applications. However mixing in these microfluidic devices is a challenge because the flows are laminar corresponding to very low Reynolds number. In this paper, mixing of two aqueous reagents is studied in a "tau" shaped microchannel by means of computational fluid dynamics (CFD). The baseline microchannel geometry has three branches: two inlets and one outlet. All the branches are 200 mum wide and 120 mum deep, which is a typical scale for mass produced disposable devices. Computational study has shown that, by splitting one of the branches of the "tau" shaped microchannel into half such that the net flow rate at the outlet remains the same as the baseline case, significantly enhances mixing. The two split inlets impinge the microchannel lateral flow from opposite directions. Also, by adding well shaped cavities at the split inlets further enhances the mixing. A detailed computational study is presented to show two different ways of employing split flow technique. Also a detailed study is done to investigate parameters like number of geometric splits, distance between the split inlets and impact of adding well shaped cavities to the best two-way split flow design for enhanced mixing.