本研究主要是以實驗之方式進行電驅動流體在微流體晶片傳輸問題之探討，所探討之問題主要可分為兩大部分：
第一部分為以簡單操作模式控制多重樣品流體(M x N)之電動聚焦及無閥切換(註：M為樣品流數量、N為出口端數量)。其操控原理為：由於玻璃管道之表面電位勢為負電位，根據Helmholtz-Smoluchowski方程式可知電驅動流體之流動方向與電位勢梯度方向同向，流體之流向可藉由電場之控制而被操控，因此在M x N微流體無閥切換裝置上，若要將樣品流操控至所指定之出口管道，只需控制所指定之出口管道具有電位勢梯度存在，其餘出口管則無電位勢梯度存在，則樣品流則可輕易地流向所指定之管道。實驗與數值模擬之結果皆顯示藉由此操作模式，樣品流可輕易地被切換至所指定之出口管道。
第二部分為多重樣品流之電動不穩定現象與其應用於微流體混合之探討。由於檢測樣品流與邊鞘流之電導率( )通常會有差異而有電導率梯度存在，而根據Poisson方程式與歐姆電流模式(Ohmic current model)，可得淨電荷密度為 ，由此可知在樣品流與邊鞘流之界面上存在著淨電荷密度，也就是說遠離壁面處亦有電動力存在，而當電場強度達到一臨界值，電動不穩定之現象將會發生於微管道中，此不穩定之流場將有助於提升樣品之混合效率。先前之電動不穩定之研究，大都為單一層界面，如T型進樣管道，而本研究之晶片為多重樣品進樣管道(M x N)，其擁有2M層界面，實驗結果顯示混合效率可在短時間及短距離內被有效地提升。最後本研究結合第一部分中之操控模式，使得電動不穩定之多重樣品流可任意切換於所指定之出口管道。

In this study, we investigate the electrokinetically-driven flow transport phenomena in microfluidic chips experimentally. Two main issues are studied as follows:
Firstly, we study the control of the electrokinetic multiple sample flows focusing/valveless switching in an MxN microfluidic chip based on electrokinetic forces (note: M is the number of sample stream and N is the number of outlet port). According to the electrokinetic body force term in the equation of motion or Helmholtz-Smoluchowski equation, we know that the flows are driven electrokinetically along the direction of the externally applied electrical potential gradient. Therefore, the direction of electrokinetic flow streams can be easily guided by controlling the externally applied electrical potential distributions in microchannels. Experimental and numerical simulation results both show the sample flows can be pre-focused into narrow streams and then guided directly into the desired outlet ports using this simple control model.
Secondly, the electrokinetic instability phenomenon of multi-interface layers (2M) (note: the interface layer between the sample flow and sheath flow) and its application in micro-mixing are investigated experimentally. In practice, there is a difference in electrical conductivity between sample flow and sheath flow, i.e., the electrical conductivity gradient exists at the interface between sample flow and sheath flow. According to the Poisson equation and the Ohmic current model, the net charge density can be expressed as , and then we can know that the net charge density exist in the bulk liquid when the electrical conductivity gradients exist in microchannels, i.e., there are electrical body forces away from the channel walls (i.e., electrical double layer). At critical electrical field strength, this induced electrical body force will result in an instability flow field. This unstable flow field can be used to enhance the species mixing in microchannels and the mixing length and mixing time can be reduced effectively. Finally, using the simple control model previously, the electrokinetic instability multi-streams can also be directed into desired outlet channel.

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