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. Recent numerical and experimental research studies have investigated the effect of microchannel geometries and time pulsing on mixing enhancement. In this paper, mixing of two aqueous reagents is studied in a “T” 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 μm wide and 120 μm deep, which is a typical scale for mass produced disposable devices. A simple geometric modification to the baseline case is made by splitting one of the inlets in half such that the net flow rate at the outlet remains same as the baseline case. The two split inlets impinge the microchannel lateral flow from opposite directions. Significant improvement in mixing using the two-way split flow modification is predicted from the modeling. Previous studies have also shown that by adding well -shaped cavities or grooves in microchannels enhance mixing, so well-shaped cavities are added at the two split inlets. Considerable improvement over the two-way split flow model is seen by adding well-shaped cavities at the split inlets. Three geometries have been systematically studied for both constant and time dependent flows.

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