利用虛擬微流道於數位微流體平台拉伸DNA

Abstract

本論文中，我們嘗試利用電控微流體平台拉伸DNA，本實驗所使用的電控微流體的工作流體為臨界膠束濃度時的Triton X-100 界面活性劑，因為界面活性劑的分子性質，我們可以在此平台上建立一肥皂膜，再藉由電控微流體改變液滴接觸角來操控液滴移動的能力，我們因此得以控制液體在此液膜內部流動，由於此流道結構不需要固體邊界即能實現連續流體的能力，故我們稱之為虛擬微流道。 若對此平台的一側儲液槽施加電壓訊號，並量測此虛擬微流道中任一側的儲液槽的面積隨時間的變化，在已知液滴高度的情形下，我們便可以估算出流道中的體積流率，由量測的結果得知此結構中流體在施加固定的電壓下，其體積流率趨近一定值，我們因此判斷這是一種理想且可靠的微流道型態。 進一步在上述的界面活性劑工作流體中加入以YOYO-1 螢光染劑染色過後的lambda DNA，並以此建立虛擬微流道後，通與一電訊號於一側的儲液槽，DNA 會隨著流體移動並經過此虛擬微流道，又因為微流道入口前端的流場拉伸梯度，預期可以觀察到DNA 解開原本的纏繞狀態並被拉伸的過程。但是結果顯示單純靠流場拉伸DNA 的拉伸效果不彰，因此也嘗試利用介電泳力來幫助DNA 拉伸，最後雖觀察到DNA 被拉伸的現象，但是整體的拉伸效果仍有待加強。

We studied DNA stretching on a digital microfluidics (DMF) device along a virtual microchannel without physical solid channel walls but stabilized with surfactant molecules, Triton X-100, at the critical micelle concentration (CMC). The surfactants stabilized the virtual microchannel as a soap film between multiple droplets manipulated between two parallel plates. With the ability of adjusting the liquid pressure of the terminal droplets, the liquid was therefore pumped through this soap film at tunable velocity. The volume flow rate along the virtual microchannel was characterized by analyzing the droplet volume variation from the captured image times the predefined droplet height between plates. The results showed a constant and repeatable flow rate under a given liquid pressure difference provided by voltage application. DNA stretching was studied by adding the lambda DNA dyed with YOYO-1 fluorescent dye into the pumped liquid. As the liquid was pumped between the droplets, DNA molecules were supposed to be elongated along the virtual microchannel accordingly because of the high extensional strain. To no avail, it seems DNA molecules can hardly be stretched by simply pumped through the virtual microchannel. We therefore resort to dielectrophoresis force which can immobilize the microspheres acting as the obstacles which will tether DNA molecules while they flow through microchannel. After several trial, we finally observe the DNA stretching while there is still room for improvement.