Design And Experimental Study On The SAR Micromixer Based On SU-8 Photolithographic Technique

In 21st century, the aim of analytical instruments and analytical science is miniaturization and integration; microfluidic chips develop fastest among it. Micromixer is a important part of microfluidic chip and realization of quick and even mixing of reagent is very important to improve performance of the chip.Based on domestic and international studies on micromixer, one splitting and recombination (SAR) type micromixing unit which can be fabricated by two dimension microchannel fabrication process was designed. According to three indexes, three structural parameters were optimized by numerical method. Two kinds of SAR micromixers and two typical micromixers which used for comparison were fabricated using SU-8 photolithographic technique. The SAR micromixers were tested by four fluids with different viscosity. The main content of this paper is as follows:1 Researches on micromixer of recent few years, mixing principles and advantages and disadvantages of all kinds of passive and active micromixers are summarized; the main research content and significance is also discussed.2 Governing equations and some constants of microfluiding are given first, and then essence and process of finite volume method and discretization equation are introduced. Finally, modeling, meshing, parameter setting and boundary conditions of micro mixing unit are explained.3 Mixing principle of SAR micromixer is illustrated. Three structural parameters of SAR mixing unit:depth of single layer h, branch angle 0, length of straight part of branch, are optimized based on three indexes:mixing efficiency of unit length, split ratio, pressure gradient, together with consideration of the application and fabrication of micromixer, and finally the optimized parameters are:h=100μm,0=70°and 1=0μm.4 The SU-8 photolithographic technique were explained step by step and the polymer PDMS which used as microchannel is also introduced shortly. For objective evaluation, straight channel micromixer and slant block type micromixer are chosen as comparing objects for the designed SAR micromixers. All these micromixers are fabricated by SU-8 photolithographic technique.5 Detection and quantitative evaluation Methods of mixing effect of micromixer are introduced. Mixing effects of SAR micromixers are tested thoroughly by using four kinds of mixture with different viscosity which are obtained by mixing glycerol and DI water in four volume ratios as experimental fluids and mixing length as evaluating index.