Design and simulation of passive micromixers based on capillary

Three-dimensional passive micromixers made by clamping capillaries in different directions and angles are presented in this paper. This type of mixers is easier to fabricate than the multi-layer passive mixers, and is the firstly proposed capillary-based micromixer. Simulations have been conducted for the flow and mass transport through the 3D-twisted compression-expansion microchannels. The simulations show that, compared to the T-mixer with the same cross-sectional perimeter, the 3D capillary mixers proposed in this paper can significantly enhance mixing. The 3D-twisted compression-expansion mixers with different clamping angles are analyzed. The results show that capillaries with clamping angle of 90 degrees, 45-90 degrees and 45 degrees exhibit different mixing mechanism. The 45-mixer presents the best mixing enhancement by reducing 90.8 % of the mixing length with only 57 %extra pressure drop in transporting the liquids to those of the T-mixer when the clamping cross-section of 0.6 mm x 0.2 mm, clamping interval of 1 mm, and the Peclet number of 3,000 are applied to all designed mixers.