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Simulation and experiment of U-mixers in centrifugal microfluidics
|關鍵字:||advection;對流;centrifugal force;microfludics;micromixer;離心力;微流體;微混合器||出版社:||機械工程學系所||引用:||Beebe, D. J., Trumbull, J. D., and Glasgow, I. K., “Microfluidics and Bioanalysis System: Issue and Examples,” Proceedings of Annual International Conference of the IEEE Engineering in Medicine and Biology, Vol. 20, 1998, pp. 1692-1697. Ducrée, J., Schlosser H. P., Haeberle, S., Glatzel, T., Brenner, T., and Zengerle, R., “Centrifugal Platform for High-Throughout Reactive Micromixing,” Proceedings of 8th International Conference on Miniaturized System for Chemical and Life Sciences Systems, Malmo, Sweden, September, 26-30, 2004. Duffy, D. C., Gills, H. L., Lin, J., Sheppard, N. F., and Kellogg, G. J., “Microfabricated Centrifugal Microfluidic Systems: Characterization and Multiple Enzymatic Assays,” Analytical Chemistry, Vol. 71, No. 20, 1999, pp. 4669–4678. Glasgow, and I., Aubry, N., “Enhancement of Microfluidic Mixing Using Time Pulsing,” Lab on a Chip, Vol. 3, No. 2, 2003, pp. 114-120. Glasgow, I., Batton, J. and Aubry, N., “Electroosmotic Mixing in Microchannels,” Lab on a Chip, Vol. 4, No. 6, 2004, pp. 558-562. Grumann, M., Geipel, A., Klaunick, C., Brenner, T., Zengerle, R., and Ducrée, J., “Microfluidic Mixing by Actuation of Magnetic Beads on Rotation Lab-on-a-Disk Platforms,” Proceedings of 9th International Conference on New Actuators, Bremen, Germany, June, 14-16, 2004. Gustafsson, M., Hirschberg D., Palmberg, C., Jornvall, H., and Bergman, T., “Integrated Sample Preparation and MALDI Mass Spectrometry on a Microfluidic Compact Disk,” Analytical Chemistry, Vol. 76, No.2, 2004, pp. 345-350. Hirschberg, D., Jagerbrink, T., Samskog, J., Gustafsson, M., Stahlberg, M., Alvelius, G., Husman, B., Carlquist, M., Jornvall, H., and Bergman, T., “Detection of Phosphorylated Peptides in Proteomic Analyses Using Microfluidic Compact Disk Technology,” Analytical Chemistry, Vol. 76, 2004, pp. 5864-3871. Hong, C. C., Choi, J. W., and Ahn, C. H., “A Novel in-Plane Passive Microfluidic Mixer with Modified Tesla Structures,” Lab on a Chip, Vol. 4, No. 2, 2004, pp. 109-113. Johnson, T. J., Ross, D., and Locascio, L. E., “Rapid Microfluidic Mixing,” Analytical Chemistry, Vol. 74, No. 1, 2002, pp. 45-51. Kim, D. S., and Kwon, T. H., “Modeling, Analysis and Design of Centrifugal Force-Driven Transient Filling Flow into a Circular Microchannel,” Microfluidics and Nanofluidics, Vol. 2, No. 2, 2006, pp. 125-140. Kockmann, N., Kiefer, T., and Engler, M., “Silicon Microstructures for High Throughput Mixing Devices,” Microfluidics and Nanofluidics, Vol. 2, No. 4, 2006, pp. 327-335. Liu, R. H., Stremler, M. A., Sharp, K. V., Olsen, M. G., Santiago, J. G., Adrian, R. J., Aref, H., and Beeb, D. J., “Passive Mixing in a Three-Dimensional Serpentine Microchannel,” Journal of Microelectromechanical Systems, Vol. 9, 2000, pp. 190-197. Melin, J., Giménez, G., Roxhed, N., Wijngaart, W. V. D. and Stemme, G., “A Fast Passive and Planar Liquid Sample Micromixer,” Lab on a Chip, Vol. 4, No. 3, 2004, pp. 214-219. Shakhashiri, B. Z., Chemical Demonstrations： A Handbook for Teachers of Chemistry, University of Wisconsin Press: Madison, WI, Vol. 1, 1983, pp. 341-343. Stremler, M. A., Haselton, F. R., McQuain, M. K., Cola, B. A., Peek, J., “Improving DNA microarray hybridization with a pulsed source-sink mixing device,” Proceedings of the 3rd Annual International IEEE EMBS Special Topic Conference on Microtechnology in Medicine and Biology, Kahuku, Oahu, Hawaii ú, May, 12-15, 2005, pp. 10-12. Stroock, A. D., Dertinger, S. K. W., Ajdari, A., Mezic, I., Stone, H. A., and Whitesides, G. M., “Chaotic Mixer for Microchannels,” Science, Vol. 295, Jan. 25 2002, pp. 647-651. Thorsen, G., Ekstrand, G., Selditz, U., Wallenborg, R. S., and Andersson, P., “Integated Microfluidics for Parallel Processing of Proteins in a CD Microlaboratory,” Proceedings of 7th International Conference on Miniaturized Chemical and Biochemlcal Analysis Systems, Squaw Valley, California, USA, October 5-9, 2003. Xia, H. M., Wan, S. Y. M., Shu, C., and Y. T. Chew, "Chaotic Micromixers Using Two-Layer Crossing Channels to Exhibit Fast Mixing at Low Reynolds Numbers," Lab on a Chip, Vol. 5, No. 7, 2005, pp. 748-755. 許晉嘉, Y型結構微混合器之旋轉可視化實驗, 國立中興大學碩士論文, 2006.||摘要:||
本研究利用計算流體力學軟體Fluent 6.2作為數值模擬之工具，探討四個90°彎曲流道所組成的U型混合器在旋轉流場下的混合表現。整個流場以離心力當作驅動力，邊界條件假設流道進出口壓力差為0。經由數位式CCD拍照進行可視化實驗，並與模擬結果對照驗證。實驗晶片利用CNC加工技術，於直徑10 cm的透明光面壓克力(PMMA)製作微流道結構。兩種工作流體分別為氯化鐵與硫氰化氨水溶液，混合後產生深紅色，藉此觀察流體混合的現象。模擬的結果顯示，U型結構會使流體產生上下對稱的渦流(vortex)，使得流體界面會產生摺疊(folding)、扭曲(distortion)及拉伸(elongation)的現象。轉速提高則會進一步產生混沌對流(chaotic advection)，增加流體的混合效果。當轉速從120提高到1200 rpm，其混合效率由20增加到84%。而兩個U型結構的混合器，其混合效率大約可以增加10~20%。由實驗拍攝到的影像進行混合效率量化，我們可以得到與模擬相同的結果，混合效率隨轉速提高而增加。
This study adopts the computational fluid dynamics software Fluent 6.2 as a simulation tool to discuss mixing performance of the U-mixer, formed by four 90 curved microchannels, on a rotating disk. The entire flow field is driven by centrifugal force with its boundary conditions assumed zero pressure at the channel inlet and outlet. The simulation results are compared with visualization experiments. The visualization experiments were carried out using a digital CCD camera in conjunction with a microscope to acquire the flow images. The centrifugal microfluidic system was constructed in a PMMA substrate of 10 cm in diameter using a CNC machine. The fluids employed for mixing experiments were ferric chloride and ammonium thiocyanate solutions. The chemical reaction of the two fluids produces blood-red color that can be quantified as the index of mixing efficiency. Simulation results show that a pair of symmetrical streamwise vortices is formed in the U-shaped channel. The vortical secondary flow causes the fluid interface to have folding, distortion and elongation, resulting in enhancement of the mixing. When the rotational speed increases from 120 to 1,200 rpm, its mixing efficiency grows from 20 to 84%. The centrifugal microfluidic system containing one more U-shaped structure (a double-U mixer) shows an increase of 10 ~ 20% in mixing efficiency. The mixing efficiency based on the concentration evaluated from the flow visualization experiments is in good agreement with the simulation results for the rotational speeds presented in the present study.
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