Numerical and experimental investigations of novel passive micromixers with fractal-like tree structures

The single-phase flow in the microchannel has one characteristic: it has a low Re (Reynolds number), and the range is usually between tens and hundreds, so the flow in the microchannel is generally laminar. Therefore, the fluid cannot mix well in the microchannel. Optimizing the structure of microfluidic chip to improve the mixing efficiency of micromixer has become a research hotspot. Here, we design a micromixer based on fractal-like tree structures. The purpose is to obtain a micromixer with better mixing performance by changing the structure. Through a series of numerical simulation, we can get that the micromixer with n (fractal level) = 2 and delta (angle increment) = 90 degrees has higher mixing efficiency at any Re. Firstly n has the greatest influence on the structure of micromixer, and the mixing performance of micromixers increases with the increase of n. Secondly, delta has a little effect on the structure of the micromixer, and the same effect on the mixing performance of the micromixer. Thirdly, through the study of Re, we can know the mixing performance of each micromixer is the best when Re = 0.01, and the worst mixing performance occurs at Re = 1 or 10. Finally, we verify the mixing performance of the micromixer with the change of n and Re through experiments.