本文中選用簡單的T型結構，並在主流道加2個擋板，來探討各種週期性的暫態注入方式對混合效果的影響。採用SU-8厚膜光阻以微影製程在矽晶圓上製作微混合器之母模，再以液態聚二甲基矽氧烷（polydimethysiloxane，PDMS）翻製微混合器主結構，接著與另一片PDMS接合，即完成實驗所需的微混合器。再加上矽膠管與兩個微量式注射幫浦構成系統，這兩個微量式注射幫浦可隨時間調配供應流體。影像擷取系統包含光學顯微鏡、數位攝影機、影像擷取卡，與電腦連結，將流體在流道中流動與混合的情況記錄下來，並截取出灰階值，由灰階值去求得混合效果。並用熱流數值軟體模擬計算流場狀態，以實驗及模擬去研究注入模式、流速大小及週期長短對混合的影響。結果顯示：（一）有擋板較無擋板的混合效果來的好，（二）往復流動的混合效果比穩態好，（三）就所選的三個模式中，以同相等流速、推拉時間比二比一的混合效果最佳，（四）Strouhal數的大小與混合效果的優劣受注入模式影響，會隨注入組合不同呈現不同趨勢的變化。

In this work, we investigate the effects of baffles and periodic infusion on the mixing in a simple “T” channel. We used the SU-8 thick film photoresist on the silicon wafer to fabricate the structure of the micromixers by photolithogrphy. Casting of polydimethysiloxane（PDMS）was followed to mold the SU-8 pattern. Another PDMS with three holes was used to bond the first patterned PDMS together. Then, we obtained the experimental micromixer. The fluid flow system consists of the micromixer, pipes and two micro-syringe pumps. The two pumps supply the two kinds of fluids to the micromixer at time variable rates. An image capture system, including an optical microscope, a CCD camera, an image capture card and a personal computer, was set up. The visualization of the mixing process and the grayscale level of the mixing fluids are obtained by the system. Mixing efficiency was evaluated by calculating grayscale level of the fluids flowing through the micromixer. We also study mixing flow by the CFD-ACE+. Study the effect of infusion mode, fluid velocity and period by experiment and simulation. The results show that (i) the baffles can make the fluid mixing better, (ii) the mixing effect of reciprocal flow is better then steady flow, (iii) the mixing efficiency of the infusion in which both inlets keep the same velocity in phase and time ratio of infusion to withdraw is 2:1 is superior to the other infusions, (iv) the dependence of the mixing effect on Strouhal number does not show a general trend for the different infusions considered.

1. Manz, A., Graber, N. and Widmer, H. M., “Miniaturized total analysis systems: a novel concept for chemical sensing,” Sensors and Actuators B: Chemical, Vol. 1, pp. 244-248, 1990.
2. Schwesinger, N., Frank, T., and Wurmus, H., “A modular microfluid system with an integrated micromixer,” Journal of Micromechanics and Microengineering, Vol. 6, pp. 99-102, 1996.
3. Koch, M., Chatelain, D., Evans, A. G.R., and Brunnschweiler, A., “Two simple micromixer based on silicon,” Journal of Micromechanics and Microengineering, Vol. 8, pp. 123-126, 1998.
4. 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.
5. 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.
6. Johnson, T. J., Ross, D., and Locascio, L. E., “Rapid microfluidic mixing,” Analytical Chemistry, Vol. 74, pp. 45-51, 2002.
7. Strook, A. D., Dertinger, S. K. W., Ajdari, A., Mezic, I., Stone, H. A., and Whitesides, G. M., “Chaotic mixer for microchannels,” Science, Vol. 295, pp. 647-651, 2002.
8. 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, pp. 190-197, 2000.
9. Vivek, V., Zeng, Y., and Kim, E. S., “Novel acoustic-wave micromixer,” IEEE International Micro Electro Mechanical System Conference, Miyazaki, Japan, pp. 668-673, January 23-27, 2000.
10. Yang, Z., Matsumoto, S., Goto, H., Matsumoto, M., and Maeda, R., “Ultrasonic micromixer for microfluidic systems,” Sensors and Actuators A: Physical, Vol. 93, pp. 266-272, 2001.
11. Lu, L. H., Ryu, K. S., and Liu, c., “A magenetic microstirrer and array for microfluidic mixing,” Journal of Microelectromechanical Systems, Vol. 11, pp. 462-469, 2002.
12. Tsai, J. H. and Lin L., “Active microfluidic mixer and gas bubble filter driven by thermal bubble micropump,” Sensor and Actuators A: Physical, Vol. 97-98, pp. 665-671, 2002.
13. Deshmukh, A. A., Liepmann. D., and Pisano, A. P., “Continuous micromixer with pulsatile micropumps ,” Solid-State Sensor and Actuator Workshop, Hilton Head Island, SC, USA, 2000.
14. Glasgow, I., and Aubry, N., “Enhancement of microfluidic mixing using time pulsing,” Journal of Lab on a Chip, Vol. 3, pp. 114-120, 2003.
15. Branebjerg, J., Fabius, B., and Gravesen, P., “Application of miniature analyzers: from microfluidic components to micro TAS,” Micro Total Analysis Systems Workshop, Enschede, Netherlands, pp. 141-151, 1994.
16. Lee, S., Lee, H. Y., Lee, I. F. and Tseng, C.Y., “Ink diffusion in water,” European Journal of Physics, Vol. 25, pp. 331-336, 2004.
17. Lu, L. H., Ryu, K. S., and Liu, C., “A magnetic microstirrer and array for microfluidic mixing,” Journal of Microelectromechanical Systems, Vol. 11, pp. 462-469, 2002.