Study on Flow Characteristics and Influencing Factors in Square Wave Micromixer

The micro-mixer is usually a pre-treatment device for laboratory chip ( LOC). The study on the influence of mixing mechanism and structure on mixing can provide guides for design and processing of micromixers. In this work, the flow characteristics and mixing mechanism in the square wave micromixer were studied when the channel Re ynolds number was between 0. 1 and 80, and the influence of channel structure on the flow and mixing performance of the fluid in the molecular diffusion dominant phase and the convection diffusion dominant phase was analyzed. The results showed that with the increase of Re in the channel, the fluid mixing transitions from molecular diffusion dominated to convection diffusion dominated stage. The factor that influenced the fluid mixing index during the dominant phase of molecular diffusion was the characteristic diffusion length. The channel width had a greater impact on the mixing index than the channel height. The reduction of the channel width could significantly increase the mixing index in the molecular diffusion phase. At Re = 0. 5, the mixing index was increased by 34. 59% when the channel width was reduced from 400 mu m to 200 mu m. The factor affecting the mixing index in the dominant phase of convection diffusion was the magnitude and intensity of the vortex generated by the centrifugal force at the turn of the microchannel. The vortex of the square wave micromixer with square section had the most fully developed vortex and the best mixing performance. Reducing the size of the square section could increase the vortex strength. At Re = 80, the mixing index of the micromixer with a channel section side length of 200 mu m was 22. 71% higher than the side length of 300 mu m.