本論文探討應用數位微流體技術於產生奈升級液滴，以介電潤濕法(electrowetting on dielectric)方式開發微流體系統元件的晶片設計與製作。此晶片優點為只需藉由液滴所接觸之電極表面電壓變化，即可由液體儲存槽中產生一奈升液滴。若將本晶片應用在微流體系統中，則可以取代微流體系統中的微制動器與微混合器結構，降低製程難度與成本。若應用於實驗室晶片平台(lab-on-a-chip)、微分析晶片(micro total analysis system)則可減少樣本體積、降低成本、可拋棄式與可攜式等優點。首先討論液滴在不同介電材料表面的接觸角變化，以選擇低驅動電壓之材料為晶片介電層。其次，實現數位微流體晶片中的四種基本操作：傳輸(transporting)、分離(cutting)、混合(merging)與產生(creating)。接著探討液滴在不同電極尺寸大小與通道高度情形下，所分離出液滴體積大小。
本文數位微流體晶片使用微機電製程技術所製作，控制系統則使用單晶片ATmega 8535控制8個電極輸出埠，依不同介電材料在大氣環境下，其最小驅動電壓分別為：聚對二甲基苯(Parylene C) 80 VDC、氧化矽50 VDC與氮化矽30 VDC，當外加矽油(silicon oil)將液滴表面包覆時，則能有效將驅動電壓分別降低為：聚對二甲基苯50 V DC、氧化矽30 VDC與氮化矽15 VDC，此外矽油還可以有效減緩奈升液滴揮發速率。降低驅動電壓可以避免介電層崩潰所造成之電解現象，使晶片的應用性更為廣泛，而減緩液滴於大氣環境下揮發速率，則可以使液滴有較佳的可移動時間與量測應用。

In this work, the development of digital microfluidic devices based on EWOD (electrowetting on dielectric) to create nano-liter droplets is presented. By altering electric voltage on contact electrodes, the device is able to create nano-liter droplets from the reservoir, which could be applied to microfluidic systems in replacement of micro-actuators and micro-mixers to facilitate the fabrication process, reduce the volume of samples and lower the cost. Besides, it is disposable and portable. First, we investigate the change of contact angle of a droplet upon different dielectric materials to choose the optimal material for the dielectric layer. Second, four basic operations of digital microfluidic devices are performed: transporting, cutting, merging and creating. Finally, we analyze the size of droplets created by different sizes of the electrodes and heights of the channel gaps.
The digital microfluidic devices are fabricated using MEMS process and driven by microcontroller ATmega8535. The initial driving voltages of the droplet for Parylene, oxide and nitride are 80 VDC, 50 VDC, 30 VDC, respectively. When the droplet is covered by a layer of silicon oil, the initial driving voltage reduces to 50 VDC, 30 VDC and 15 VDC for Parylene, oxide and nitride, respectively, and the evaporation rate of the droplet decreases. The reduction in driving voltage could avoid the electrolysis resulting from the breakdown of dielectric layer and expand the application of the device. In addition, the improvement of evaporation rate could grant the droplet longer move time and application.

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