在數位微流體晶片上同時產生複數液珠

Abstract

數位微流體已廣泛用於複雜、多步驟的生物應用。然而因為現有的三電極式分裂方法無法快速地產生液珠，一些需要大量液珠的檢測如分子的並行多重檢測或者數位核酸放大檢測對於數位微流體設備仍然是很大的挑戰。為了解決這項問題，在基於電濕潤的數位微流體晶片上，我們提出了一種使用鋸齒狀電極的新穎的液珠分裂方式。它需要兩步驟控制：首先液體將被拉伸填滿列電極，然後再由電極陣列切斷液體，便能同時產生多個液珠。鋸齒狀電極產生了彎月形液體填充的現象，與傳統的電極手指設計相比，液體與電極有著更大的初始重疊面積，進而穩定了產生的液珠體積。實驗在不同角度的1公分鋸齒狀電極同時產生20個奈升等級液滴 (6~8nL)，若排除在列兩端的液滴，液滴的體積變異係數(CV)僅有1.26%。此外，液珠的數量取決於列電極的長度及列數，且不會影響CV值。這方法展示了在數位微流體晶片上進行並行多重檢測及數位核酸放大測試的巨大潛力。

Digital microfluidics (DMF) has been widely used in biological applications that involve complex and multistep protocols. However, parallel multiple analysis in molecular or digital nucleic acid amplification tests which require numerous droplets are still a challenge for DMF device because the existing three-electrode splitting method cannot generate droplets rapidly. To solve the problem, a novel splitting method with a zigzag row-electrode design on electrowetting-based DMF chips is proposed. It requires a two-step actuation control: the liquid is first stretched on the row-electrode and then split by the electrode array to simultaneously generate multiple droplets. The zigzag electrode promotes the meniscus filling phenomena and provides a larger initial overlapping area between the liquid and the electrode array than the traditional electrode fingers design, thereby stabilizing the volume of droplets generated. Twenty (20) nanoliter droplets (of 6~8 nL) are simultaneously generated in 1 cm zigzag row-electrode with different angles. Excluding the droplets at the both ends of the row, the coefficient of variance (CV) of droplet volume is only 1.26%. Furthermore, the number of the droplets can be controlled by the length and the number of the row-electrodes without affecting CV. It shows a high potential for parallel multiple analyses or digital nucleic acid amplification tests on DMF chips.