Research On Characteristic Of High Reflux Passive Micromixer

As one of the important structural units of microfluidic chips and the pre-treatment device of Micro Electro Mechanical Systems(MEMS),micromixers have been developing with the development of microfluidic chips and MEMS.According to two different mixing principles applied,micromixers can be divided into two groups: active micromixers and passive micromixers.Compared with active micromixers,passive micromixers do not require additional power sources,so passive micromixers have the following major advantages: simple structures,simple manufacturing process,and easy integration;More importantly,when fluid flows in the microchannel,passive micromixers will not affect the biochemical activity and physical and chemical properties of organic fluids.So passive micromixers have a wide range of applications,such as: chemical synthesis,emulsion preparation,biochemical analysis,biometric technology,drug control release and other fields.In order to overcome the shortcoming of low mixing efficiency near the vicinity of the wall in the mixing process of passive micromixers,on the basis of summarizing the previous research on the reflux passive micromixers,a high reflux passive micromixer based on jet principle has been designed,and this micromixer has the advantages of simple structure,high reflux rate and high mixing efficiency.This micromixer mainly make use of the high speed jet to suck and mix the fluid in the mixing zone,which produces the reflux in the circulation channel,so this micromixer can realize the multi-cycle mixing of the low efficiency fluid in the vicinity of the boundary layer.In this paper,the influence of different structural parameters and fluid properties on the mixing performance of micromixer was studied by using commercial software ANSYS CFX.Simultaneously,the actual mixing effect of micromixer was studied by designing microfluidic mixing experiments,and we make a full comparison between the experimental results and simulation results.The numerical simulation results show that as the jet intensity increases and the viscosity of fluid becomes lower,the reflux rate and mixing efficiency of the micromixer are continuously improved;When the jet intensity reaches a certain level,the jet in the mixing zone will deflect,which leads to a large difference in the amount of recycle flow between two circulation channels.And this asymmetric recirculation makes the collision of fluid moleculesmore intense,and chaotic convection more stronger,which results in a high mixing efficiency;When Re ? 15,the maximum reflux rate of the micromixer exceeds 35% and the mixing efficiency exceeds 95%.In addition,according to the comparison between the experimental results and the numerical simulation results,due to the experimental results and the numerical simulation results keep a good consistency,which means that the numerical simulation method used in this paper is reliable,and this is also explained that in some extent,the micromixer designed in this paper has a good application value.