New Method Of Microfluidic-based Rapid Mixing And Its Applications

To study rapid protein folding reactions, the reaction must be triggered at a very shottime scale, which is good fit with the characteristic of micromixer. Recently, manymicrofludic mixers were proposed to achieve fast and uniform mixing, especially zigzagserpentine micromixer. However, no general rule was reported for optimization of fastzigzag micromixer.In this work, a novel design rule is presented for the optimization of a simple zigzagmicromixer to studies of protein folding kinetics. The novel design rule includes two parts:1) occurring frequency of corner f=C/Δt, in which C is the corners number, Δt isdeadtime;2) Turning Degree. By using computational fluid dynamics simulations, wesystematically investigated the mixing efficiency of zigzag-shaped microchannels withvarying corner geometries. We found that the mixing time reduced with the increasing ofOccurring Frequency of Corner and Turning Degree. It showed that the design rule wepresented was significant for the optimization of micromixer. Thus, given a microchannelof30μm width and20μm depth with4corners of45°, a mixing time of¹4μs can beexperimentally achieved.Using microsecond mixer, we studied the two chemiluminescence reactions catalyedby horseradish peroxidase and Co²⁺. There are three aspects gat from the horseradishperoxidase system:1) the CL intensity of fast mixing is4⁵times as large as slow mixing,and CL intensity decreased significantly in fast mixing,2) detection limit is5×10^-9M,3)the linear range is4orders of magnitude. Contrastively, in Co²⁺system:1) the CLintensity of fast mixing is4⁵times as large as slow mixing, and CL intensity did notdecrease significantly in fast mixing,2) detection limit is5×10^-9M,3) the linear range is4orders of magnitude. To a conclusion, the Z-shape microsecond mixer provides a newplatform for the study of folding kinetics of horseradish peroxidase andchemiluminescence kinetics of the immunoassay.