本研究探討流體在鋸齒形具90度轉彎流道之混合器混合現象；比較等截面流道與週期性擴張−收縮流道中之流體混合。藉著數值模擬與實驗觀察流量、週期性擴張−收縮流道和寬深比等參數對混合效率的影響。使用數值軟體CFD-ACE+模擬微混合器的三維流動和混合現象。此外，製作微混合器的過程包含：使用光微影製程製作母模、利用PDMS翻模、將具有流道的PDMS與載玻片接合。接著，將去離子水溶液以及玫瑰紅螢光水溶液分別以微注射幫浦注入待觀測微混合器，再使用共軛焦顯微鏡取得流道內螢光溶液之流動及濃度分佈的影像。比較得知數值模擬與實驗結果相當吻合。最後，由數值模擬的結果得知(一)藉著週期性擴張−收縮流道以及降低寬深比可提高混合效率。(二)在較高雷諾數時，混合效率會隨雷諾數的增加而提高，但同時壓降也會大幅增加。

In this work, we investigate fluid mixing in zigzag micromixers with 90-degree bendings; both uniform cross-section and periodically divergent-convergent channels are considered. We examine the effects of the flow rate, the periodically divergent-convergent channel and the aspect ratio on mixing efficiency by simulation and experiment. We apply the commercial package, CFD-ACE+, to simulation the three-dimensional flow and mixing in the micromixers. Besides, the fabrication process of the micromixers includes applying the photolithography method to fabrication SU-8 mold, casting the mold by PDMS (polydimethysiloxane) and bonding the patterned PDMS with a sheet of cover glass. The fluid flow system consists of the micromixers with pipes and two-syringe pumps, which pump pure water and water with Rhodamine B into micromixer. The fluid flow and mixing is observed by confocal spectral microscope. Comparison of simulation and experiment results is made. The simulation results show that (i) the mixing efficiency can be improved by using periodically divergent-convergent channels or by decreasing aspect ratio of the microchannel. (ii) For the cases with a higher Reynolds number, the pressure drop increases dramatically, while the mixing efficiency increases with the increase of the Reynolds number.

1.A. Manz, N. Graber and H. M. Widmer, 1990. “Miniaturized total chemical analysis systems: a novel concept for chemical sensing,” Sensors and Actuators B: Chemical, Vol. 1, pp. 244-248.
2.V. Mengeaud, J. Josserand and H. H. Girault, 2002. “Mixing processes in a zigzag microchannel: finite element simulations and optical study,” Analytical Chemistry, Vol. 74, pp. 4279-4286.
3.G. Comini, C. Nonino and S. Savino, 2003. “Effect of aspect ratio on convection enhancement in wavy channels,” Numerical Heat Transfer A, Vol. 44, pp. 21-37.
4.S. Savino, G. Comini and C. Nonino, 2004. “Three-dimensional analysis of convection in two-dimensional wavy channels,” Numerical Heat Transfer A, Vol. 46, pp. 869-890.
5.T. H. Ko, 2007. “Effects of corrugation angle on developing laminar forced convection and entropy generation in a wavy channel,” Heat Mass Transfer, Vol. 44, pp. 261-271.
6.T. H. Ko and C. S. Cheng, 2007. “Numerical investigation on developing laminar forced convection and entropy generation in a wavy channel,” International Communications in Heat and Mass Transfer, Vol. 34, pp. 924-933.
7.J.-K. Chen and R.-J. Yang, 2007. “Electroosmotic flow mixing in zigzag microchannels,” Electrophoresis, Vol. 28, pp. 975-983.
8.J.-T. Yang and K.-W. Lin, 2006. “Mixing and separation of two-fluid flow in a micro planar serpentine channel,” Journal of Micromechanics and Microengineering, Vol. 16, pp. 2439-2448.
9.J. S. H. Lee, Y. Hu and D. Li, 2005. “Electrokinetic concentration gradient generation using a converging-diverging microchannel,” Analytica Chimica Acta, Vol. 543, pp. 99-108.
10.S. A. Rani, B. Pitts and P. S. Stewart, 2005. “Rapid diffusion of fluorescent tracers into Staphylococcus epidermidis biofilms visualized by time lapse microscopy,” Antimicrobial Agents and Chemotherapy, Vol. 49, pp. 728-732.
11.J. Boss, 1986. “Evaluation of the homogeneity degree of a mixture,” Bulk Solids Handling, Vol. 6, pp. 1207-1215.
12.郭鈞華, 2008. “具直角轉彎、s型轉彎及分合流道的微型混合器,” 國立成功大學機械工程研究所碩士論文.