以極化毛細管操控微量流體的研究

Abstract

最近由於在微流體操控上的需求, 微流道中的表面張力越來越受到重視, 為了控制其中的表面張力, 一般會使用到兩種主要的方法, 一種是熱毛細現象（thermocapillary）, 另一種是電毛細現象（electrocapillary）。這裡要提出一種新的方法, 利用極性流體的極化效應, 操控流體在微流道中的表面張力, 稱作極化毛細現象（polar capillary effect）。這種方法可以改變電極的特性, 讓原本斥水性的電極變成親水性, 以便控制流體的進出。為了驗證此種方法的可行性, 這裡設計及製造了幾種具有電極的微流道, 其中一種封閉式流道成功製造, 並進行相關測試。在測試中發現, 當對電極施加電壓小於2伏特時, 去離子水（DI water）在極化毛細管中幾乎不會流動。當施加電壓上到3伏特時, 該流體在微流道中開始明顯的流動, 其流速將近有69μm/min。除了實驗極化毛細現象之外, 毛細現象也會被測試, 為了要找出毛細現象裡的重要因子, 對將來改善極化毛細管的設計會有幫助。

Due to the demand on microfluidic handling, the surface tension in microchannel has attracted lots of attention recently. For controlling surface tension in microchannel, two major ways were reported, thermocapillary (Marangoni effect) and electrocapillary (electrowetting) methods. Here, a new surface tension controlling method by polarization of liquid in the microchannel is proposed, it is called polar capillary effect. The proposed method can change the solid-liquid interface at electrodes from hydrophobic to hydrophilic characteristic. In order to verify the feasibility, several microchannels with electrodes are designed and fabricated. One of sealed microchannels is fabricated and tested successfully. It is found that the liquid (DI water) in the capillary is motionless with input voltage under 2 volts. While the voltage is raised to 3 volt, the liquid flows smoothly in microchannel with the velocity of 69-μm/min. Besides the polar capillary effect, the capillary effect is also tested to identify the key factors within it, that help with the improved design of polar capillary in the future.