Design and test of a passive planar labyrinth micromixer for rapid fluid mixing
2012
Li, Peng | Cogswell, Jeremy | Faghri, Mohammad
In this paper, we explore the possibility of improving the efficiency of Dean vortex-based mixers by only employing smooth-walled simple two-dimensional (2D) geometries. Numerical simulation results reveal that the symmetries of Dean flows in the prevalent “S-shaped” mixers can be broken up by adding a simple 180° turn between two consecutive curved channels. A planar labyrinth micromixer that is composed of multiple such mixing units is designed for improved mixing. The mixer is fabricated in a single lithography step and the labyrinth has a footprint of 7.32mm×7.32mm. Experiments using fluorescein isothiocyanate solutions and deionized water demonstrate that our design achieves fast and uniform mixing within 9.8s to 32ms for Reynolds numbers (Re) between 2.5 and 30. For the first time, multiple fluid bands are observed at Re=5 in a simple 2D microchannel design without using obstructions or split-and-recombine features. An inverse relationship between mixing length and mass transfer Péclet number (Pe) is observed. Due to the simple planar structure, the micromixer can be easily integrated into lab-on-a-chip devices where passive mixing is needed.
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