以交流電動力提升微混合器效能之實驗與數值模擬研究

Experimental and Numerical Study of Mixing Enhancement for a Micromixer with Applying AC-Electrokinetics

林柏彣(Bo-Wen Lin)

指導教授 ： 張正憲

國立臺灣大學/工學院/應用力學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.02902

摘要

在微流體系統中，交流電動力時常被用來做為操控粒子在流體中運動以及擾動流場的一種機制，交流電動力主要包含了介電泳、交流電滲，以及電熱效應，而這些交流電動力，則會因為電解質的帶電量，電解溶液的導電度，以及交流電場電壓、頻率的不同等而有所區分。
此外，在生醫與生化的領域中，常需要快速混合地兩種流體。一般之混合器使用機械式的攪拌來加速混合。然而，在微奈米尺度下，由於流體在微通道中呈現層流狀態，自然擴散即成為混合器中最主要的混合機制。但僅靠自然擴散來達到完全混合，則需要很長的微混合器通道及混合時間，不符微型混合器的設計要求。另外，若引進特殊的通道設計，以造成渦流等提升混合效率，則需付出消耗背壓的代價。因此，本研究將交流電動力效應應用於微混合器上以縮短擴散長度及混合時間，並提升混合效能。
本論文主要依據不同操作參數以及其影響因子探討微混合器之混合效能，並藉由數值模擬設計出三種不同的電極形狀以及最佳化之電極尺寸進行為混合器實驗，並結合相關理論及以有限元素法的模擬方式來解釋實驗中所觀察到的現象，使得理論、模擬與實驗間得以相互映證。其中，應用交流電動力效應之微混合器實驗結果顯示，分別在入口流率為10ul/hr與100ul/hr時能將混合指標有效地從自然擴散之40.15%與15.23%提升至85.55%與30.05%。

關鍵字

交流電動力 ； 電熱效應 ； 微混合器 ； 有限元素法 ； 混合指標

並列摘要

In microfluidics, the study of AC-electrokinetics correlates with the motion behavior of particles in fluids. The AC electrokinetics involving the dielectrophoresis, AC electroosmosis or AC electrothermal effect will be generated according to charges of colloids, different properties of electrolytes or amplitude and frequency of external applied voltages.
In addition, Biomedical and Biochemical applications require rapid mixing of different fluid samples. The mechanism of mixing in micromixer is different from the mechanical mixer. At the micro scale level, the fluid flow is usually highly ordered laminar flow and lack of turbulence which make the diffusion be the primary mechanism for mixing. However, to achieve complete mixing only through pure diffusion takes a long time and needs a long mixing microchannel as well, which does not satisfy the ideal design for a micromixer. Besides, it consumes back pressure if we bring in the particular channel geometry and obstacle configuration for the microchannel design in order to produce vortices to increase the mixing efficiency. Therefore, we apply AC-eletrokinetics effect to mixing enhancement for a micromixer to short the mixing length and mixing time in this work.
This work uses three different types of microelectrodes and optimal microelectrode sizes to conduct the experiment. The analytical and numerical results were compared with experimental measurements conducted in this work. The results of the mixing index at the flow rate of 10ul/hr and 100ul/hr can be lifted effectively from 40.15% and 15.23% to 85.55% and 30.05% respectively by applying AC-eletrokinetics effect.

並列關鍵字

AC-electrokinetics ； AC electrothermal effect ； micromixer ； numerical method ； mixing index

參考文獻

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