電動力微流體元件之設計與應用：電潤濕數位微流體晶片與電滲流微混合器

Design and Application of an Electrokinetically-driven Microfluidic Device：Electrowetting Microfluidic Chips and AC Electroosmotic Micromixer

陳智霖(Jhih-Lin Chen)

指導教授 ： 謝文馨

國立中正大學/工學院/機械工程學系/博士(2013年)

摘要

本研究之目的為電動力微流體元件之設計與應用，包含(1)介電潤濕(Electro-Wetting-on-Dielectric, EWOD)數位微流體與(2)交流電滲流(AC electroosmotic flow, ACEO)微混合器，這些微流體元件具有液滴輸送、光學檢測、液體混合之功能。
第一個部分，利用EWOD機制建構數位微流體操作平台，在疏水表面上，利用電壓造成液滴表面能改變，使液滴與接觸面間由疏水轉為親水的潤濕現象，讓液滴產生移動。本研究成功示範電潤濕數位微流體之液滴輸送的可行性與重複性測試，使用電導度在100 μS/cm以下之去離子水、蔗糖、稀釋的緩衝溶液，皆可順利完成輸送液滴之功能，並且結合流式細胞儀光學檢測技術於晶片上，並進行螢光顆粒偵測極限測試。
第二個部分，本研究設計了一種面對面、大小不對稱的電極對，可以產生ACEO電容充電的效應，引起流體腔內複雜的三維渦流場，其速度可達每秒1 mm以上的速度，這樣的ACEO微混合器晶片具有幾項特點：(1)電極塗有鐵氟龍和Parylene C的疏水防汙層和介電絕緣層，防止電解和非特異性吸附問題。(2)從實驗觀察與數值模擬驗證其流場現象，都顯示此ACEO微混合器會產生出互相垂直的兩組旋渦。一組是由於底部電極周圍推出了強烈的切向電場，造成電極區域外部的流體向電極中心集中後向上流動，造成了垂直於電極方向的數個旋渦；另一組則是由於底部電極的四個角落外的切向電場最弱，形成了四個停滯點，從而導引平行於電極的漩渦產生。(3)由於面對面電極所產生的數個三維微渦流場能跨越整個流體腔，比起以往使用同(共)平面電極的微混合器更能均勻的混合整個流體腔。(4)從混合增強因子的比較可以證實，本論文的ACEO微混合器使用去離子水溶液混合時，混合時間可以縮短，提升的自然擴散速度有360倍，比起文獻高出10至42倍。(5)實現了單股DNA和大腸桿菌細胞的混合測試，證實此ACEO微混合器提供了極佳的混合性能與多種生物溶液混合的適用性。以上結論證實本研究之電滲流微混合器提供了高效能的混合特性，可快速且均勻的混合樣品溶液，可提供未來多樣化微流體系統的應用。
本論文已成功設計與應用上述電動力微流體元件，使其具有數位液滴輸送、光學檢測、微混合器之能力，將提供有用的信息在未來微流體操控領域的發展與應用。

關鍵字

大腸桿菌 ； 單股DNA ； 非對稱電極對 ； 混合增強因子 ； 微混合器 ； 交流電滲流 (ACEO) ； 介電潤濕(EWOD)

並列摘要

The purpose of this study is to design and application of electrokinetically-driven microfluidic devices：(1) Electro-Wetting-on -Dielectric (EWOD) digital microfluidic chip；(2) AC electroosmotic (ACEO) micromixer. These microfluidic devices can complete, including droplet transport, mixing, and optical detection.
The first part is the use of EWOD mechanism to construct a digital microfluidic platform. The voltage change the surface tension balance, and the contact surface of droplet wetting phenomenon is caused by a hydrophobic into a hydrophilic, so that droplet movement. This study demonstrate feasibility and reproducibility of the droplet transport in EWOD digital microfluidic, we used the electrolytic conductivity of less than 100 μS/cm, such as dilution buffer solution, DI water and sugar, can be successfully completed droplet transport function, and the combination of flow cytometer optical detection technology on the chip, and the implementation of the fluorescent particle limit of detection (LOD) test.
The second part of this study, the design of a face-to-face, asymmetric pair of planar electrodes can produce ACEO capacitor charging effect, causing fluid cavity complex three-dimensional vortex flow field, velocity nearly 1 mm/s, ACEO micromixer chip has several characteristics：(1) The electrodes for the reported micromixer were coated with dielectric (Parylene C) and hydrophobic anti-fouling (Teflon-AF) layers to prevent electrolysis at high voltages and non specific adhesion problems in biological applications and to increase the slip velocity on the electrode surface. (2) Based on the numerical calculations and experimental observations, the unique shape of the face-to-face, asymmetric pair of planar electrodes was noted as generating two sets of vortices. One set of vortices was located at the four corners of the bottom electrode, and another set of vortices was located above the bottom electrode. The confluence of inward ACEO flows from the edges of the bottom-electrode protrusion resulted in a higher velocity at the center of the protrusion and thereby locally induced a large inward-pumping force, which was responsible for the formation of vortices at the corners of the bottom electrode. (3) Due to the two sets of vortices generated by the unique shape of the face-to-face electrode pair and the mixing performance values were uniform across the entire height of the fluid cavity. (4) The mixing time for the stationary DI water and Acid Yellow 73 solution when the micromixer was used was found to be 360 times faster than that when diffusion was used. In past studies, the mixing time when ACEO micromixers were used with co-planar electrode pairs was 10 to 42 times faster than when diffusion was used. (5) The usefulness of the ACEO micromixer in the hybridization of ssDNAs and the mixing of E. coli and RNA stains was demonstrated experimentally. The results confirmed the excellent mixing performance of the ACEO micromixer; the mixing enhancement factors were 316 and 305, respectively, for these two biological applications.

並列關鍵字

Escherichia coli ； single-stranded deoxyribonucleic acids ； mixing enhancement factor ； asymmetric electrode pair ； micromixer ； Electro-Wetting-on-Dielectric ； AC electroosmotic flow

參考文獻

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