微小尺度下，使兩種或多種流體在合理的時間內完成混合，近年來在微型全分析系統（Micro-Total-Analysis-System）中扮演一個很重要的工作，目前在生物醫學方面的應用有生醫檢驗、基因表現分析、藥物偵測等。然而在我們所熟悉的巨觀流場中，我們可以藉由紊流的產生，來增加兩種不同流體的接觸面積，便可得到混合的效果。但是在微小尺度下，由於流場速度及長度尺寸均不及巨觀尺度，造成系統中的雷諾數（Reynolds number）遠小於紊流發生之雷諾數，因此我們可以排除以產生紊流的方法來幫助混合的可能性。
本論文研究的目標是設計一新型微混合器，並利用計算流體力學（CFD）數值模擬計算探討此微混合器。其主要概念，便是在主要流道的左右，各加上一個回流的支流，利用這些回流流道可以將流體導引回至主流道的前端，藉著彎曲流場以產生混合的效應，並分析該微小尺寸混合器裝置內的流場，希望可以提供此類微混合器重要的設計參數給設計者及實驗者，如幾何形狀、流道位置、進口速度等對混合機制所產生的影響。

In micro-scale, complete mixing of two or more fluids within a reasonable time plays an important role in Micro-Total-Analysis-System recently. The applications of biomedical area are biomedical diagnose, gene expression analysis and drug discovery. However, in the macroscopic flow we know, we can increase the contact area of two different fluids by producing turbulence to enhance the mixing effect. But the flow velocity and length in micro-scale are smaller than those in macro-scale, and the Reynolds number in micro system is smaller than the turbulent Reynolds number. Therefore, the possibility of enhancing the mixing effects by producing turbulence, has been excluded.
The objective of this study is to design a new type micromixer by using Computational Fluid Dynamics (CFD) techniques. The primary idea of this micromixer is to add feedback channels on the both sides of the main flow channel. Producing the mixing effect by using these feedback channels that guide the fluids flow back to the main channel. Analyze and simulate the flow of this micromixer, so that we can provide important design parameters for designers and the operation conditions for experimenters, which can bring about influences of mixing, likes geometry, channel position and inlet velocity.

[1] Manzs, A., Graber, N., and Widmer, H.M., “Miniaturized Total Analysis Systems: A Novel Concept for Chemical Sensing”, Sensors and Actuators, B1, 244-248, 1990.
[2] Fujita, H., “A Decade of MEMS and its Future”, Peoceeding of IEEE MEMS Symposium, pp. 1-7, 1997.
[3] Bird, R.B., Stewart, W.E., and Lightfoot, E.N., Transport Phenomena, John Wiley & Sons, Inc., 1960.
[4] Gebhard, U., Hein, H., Just, E., and Ruther, P., “Combination of a Fluidic Micro-Oscillator and Micro-Actuator in LIGA-Technique for Medical Application”, TRANSDUCERS’97, Chicago, June 1997.
[5] Gebhard, U., Hein, H., Schmidt, U., “Numerical Investigation of Fluidic Micro-Oscillators”, Journal of Micromechanics and Microengineering, Vol.6, pp. 115-117, 1996.
[6] Miyake, R., Lammerink, T.S.J., Elwenspoek, M., Fluitman, J.H.J., “Micro Mixer with Fast Diffusion”, Proceedings An Investigation of Micro Structures, Sensors, Actuators, Machines and Systems. IEEE, pp. 248-283, 1993.
[7] Knight, J.B., Vishwanath, A., Brody, J.P., and Austin, R., “Hydrodynamics Focusing on a Silicon Chip: Mixing Nanoliters in Microseconds”, Physical Review Letters, Vol.80, No.17, pp. 3863-3866, 1998.
[8] Andreev, V.P., Koleshko, S.B., Holman, D.A., Scampavia, L.D., and Christian, G.D., “Hydrodynamics and Mass Transfer of the Coaxial Jet Mixer in Flow Injection Analysis”, Analytical Chemistry, Vol.71, No.11, pp. 2199-2204, 1999.
[9] Schwesinger, N., Frank, T., and Wurmus, H., “A Modular Microfluidic System with an Integrated Micromixer”, Journal of Micromechanics and Microengineering, Vol.6, No.1, pp. 99-102, 1996.
[10] Branebjerg, J., Granvesen, P., Krog, J.P., and Nielsen, C.R., “Fast Mixing by Lamination,” Proceedings. An Investigation of Micro Structures, Sensors, Actuators, Machines and Systems. IEEE, pp. 441-446, 1996.
[11] Koch, M., Chatelain, D., Evans, A.G.R., and Brunnschweiler, A., “Two Simple Micromixers Based on Silicon”, Journal of Micromechanics and Microengineering, Vol.8, No.2, pp. 123-126, 1998.
[12] Koch, M., Witt, H., Evans, A.G.R., Brunnschweiler, A., “Improved characterization technique for micromixers”, Journal of Micromechanics and Microengineering, Vol.9, No.2, pp. 156-158, 1999.
[13] Erbacher, Ch., Bessoth, F., Busch, M., Verpoorte, E., Manz, A., “Towards Integrated Continuous-Flow Chemical Reactors”, Mikrochimica Acta, Vol.131, pp. 19-24, 1999.
[14] Ehlers, St., Elgeti, K., Menzel, T., and Wießmeier, G., “Mixing in the Offstream of a Microchannel System”, Chemical Engineering and Processing, Vol.39, No.4, pp. 291-298, 2000.
[15] Veenstra, T.T., Lammerink, T.S.J., Elwenspoek, M.C., and van den Berg, A., “Characterization method for a new diffusion mixer applicable in micro flow injection analysis systems”, Journal of Micromechanics and Microengineering, Vol.9, pp. 199-202, 1999.
[16] Lee, S.Y.K., Lee, K.H.N., Wong, M., Zohar, Y., “Design, Fabrication and Calibration of a Mixing Layer Micro-Device”, International Symposium on Smart Structures and Microsystems, 2000.
[17] Bing, H., Brian, J.B., Xiang, Z., Roujian, Z., and Fred, E.R., “A Picoliter-Volume Mixer for Microfluidic Analytical Systems”, Analytical Chemistry, Vol.73, pp. 1942-1947, 2001.
[18] Gobby, D., Angeli, P., and Gavriilidis, A., “Mixing characteristics of T-type microfluidic mixers”, Journal of Micromechanics and Microengineering, Vol.11, pp. 126-132, 2001.
[19] Bertsch, A., Heimgartner, S., Cousseau, P., Renaud, P., “3D Micromixers – Downscaling Large Scale Industrial Static Mixers”, MEMS 2001. The 14th IEEE International Conference on, 2001.
[20] Jung, Y.C., Lu, M.C., Tsai, T.H., Yao, N.K., Webster, J.R., Tseng, F.G., “Study of an Order Changing Microfluidic Mixer”, 第一屆海峽兩岸微系統科技研討會論文集, 2000.
[21] Liu, R.H., Stremler, M.A., Sharp, K.V., Olsen, M.G., Santiago, J.G., Adrian, R.J., Aref, H., and Beebe, D.J., “Passive Mixing in a Three – Dimensional Serpentine Microchannel”, Journal of Microelectromechanical Systems, Vol.9, No.2, pp.190-197, 2000.
[22] Jones, S.W., Thomas, O.M., Aref, H., “Chaotic advection by laminar flow in a twisted pipe”, Journal of Fluid Mechanics, Vol.209, pp.335-357, 1989.
[23] Aref, H., “Stirring by chaotic advection”, Journal of Fluid Mechanics, Vol.143, pp.1-21, 1984.
[24] Yang, Z., Goto, H., Matsumoto, M., and Yada, T., “Micromixer incorporated with piezoelectrially driven valveless micropump”, Micro Total Analysis Systems’98, pp.177-180, 1998.
[25] Yang, Z., Goto, H., Matsumoto, M., and Maeda, R., “Ultrasonic Micromixer for Microfluidic Systems”, MEMS 2000, The 13th Annual International Conference on, 2000.
[26] CFD-ACE(U) User Manual, Version 6.6, CFD Research Corporation, 2001.
[27] Van Doormaal J.P., Raithby, G.D., “Enhancements of the SIMPLE Method for Predicting Incompressible Fluid Flows”, Numerical Heat Transfer, Vol.7, pp.147-163, 1984.