A novel passive enlarged micromixer has been proposed and experimentally and numerically investigated in this study over 0.5 ≤ Re ≤ 100. Flow visualization was applied to qualitatively assess flow patterns and mixing, while induced fluorescence was applied to quantify the distribution of species at six locations along the channel length. Numerical simulations were applied to assist in the description of the highly rotational flow patterns. Two individual species are supplied through a total of three lamellae, which are converged prior to entering the main mixing channel, which consists of five groove-enhanced circular division elements. Grooves along the bottom surface of the channel allow for the development of helical flow in each subchannel of the mixing element, while the circular geometry of the mixing elements promotes the formation of Dean vortices at higher Reynolds numbers. The main mixing channel is 2000 μm wide and 750 μm deep, while the total channel length is 137.5 mm. Flow rotation was observed at all investigated Reynolds numbers, though the degree of rotation increased with increasing Re. A decreasing-increasing trend in the degree of mixing was observed, with a critical value at Re = 10. Of the investigated cases, the highest degree of mixing at the outlet was achieved at Re = 0.5, where mass diffusion dominates. A standard deviation of σexp = 0.062 was reported. At Re = 100, where advection dominates and secondary flow develops, a standard deviation of σexp = 0.103 was reported, and the formation of additional lamellae was observed along the channel length due to the merging of rotated substreams. The additional lamellae contributed to the increase in interfacial area and reduction of the path of diffusion.

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