Laminar mixing in different interdigital micromixers: I. Experimental characterization

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Abstract
Interdigital‐type glass micromixers with alternating feed channels to periodically create liquid multilamellae, were fabricated for basic investigations of hydrodynamics for liquid mixing of two streams. Three interdigital designs developed, rectangular, triangular, and slit‐type, differed in their flow‐through mixing chamber. These designs are based on simple polygon geometries and their combinations. The flow patterns of an aqueous solution dyed with blue and uncolored water were investigated for different interdigital mixers. Since mixing in a nonfocused device, such as the rectangular mixer, was not completed, focusing techniques were applied. Geometric focusing was used to reduce lamellae width and to speed up mixing. In the special version of the triangular mixer, SuperFocus mixer, liquid mixing times are reduced to about 10 ms, as determined by iron‐rhodanide reaction imaging. In the latter case, the lamellae are compressed by a factor of 40, from a width of 160 to 4 μm. For both the triangular and slit‐type micromixer, flow patterns differed from regular multilamination ones. At high flow rates, lamellae tilted. When the flow cross‐sectional area was expanded, jet and associated eddies formed further improved mixing. Mixing investigations also helped develop imaging techniques. The rhodanide imaging complemented water blue contrasting.