A 3-D Overbridge-Shaped Micromixer for Fast Mixing Over a Wide Range of Reynolds Numbers

This paper reports the development of a 3-D passive micromixer named the overbridge-shaped micromixer (OBM), which can achieve fast mixing by taking advantage of the splitting, recombination, and chaotic advection mechanisms simultaneously. A scheme with the splitting channels of unequal widths is proposed for tremendously enhancing the mixing uniformity in the regions closing to the side walls. The channel depth-to-width ratio is the key factor to mixing performance. A four-unit OBM has been successfully fabricated via a multilayer polydimethylsiloxane process, and the total length of the OBM is <2 mm. Up to a 90% efficiency has been achieved within a Reynolds number (Re) range from 0.01 to 200 by numerical analysis, and the same mixing efficiency was also proven experimentally within a Re range from 0.01 to 50. A high efficiency of 90% was also obtained when mixing two fluids with different flow rates at the two inlets ranging from a ratio of 1:9 to 9:1.