Manipulation And Simulation Of Droplets Based On Electrowetting On Dielectric

Owing to the potentials of integration, automation, efficiency and convenienceof microfluidic chip systems (MCS), it has become one of the important researchfocuses of analysis instruments recently. The manipulation and control of micro-literor nano-liter liquids, such as the transportation, separation, mixing and so on, is thebasis for the MCS development, and one of the most challenging research intereststhroughout the world. Compared with other actuation ways, only electrowetting ondielectric (EWOD) realizes the integration and automation of transporting, creating,dividing and merging droplets on one chip, and thus builds a solid foundation forMCS. Furthermore, EWOD-based MCS is very promising in the application of someoptical devices, such as variable focus micro lens, tunable optical fibers and so on.Therefore, the research and development in this field are flourishing in recent years.In this thesis, the design, fabrication and test of the device based on EWOD areperformed. Firstly, based on the theories of EWOD, contact angle saturation andsurface adhesion, we put forward a two dimensional physical model of EWOD-based"sandwich" devices. The effects on the transportation and creation of droplets arequalitatively analyzed in the model. Secondly, with the help of the model and thecomputational fluid dynamics (CFD) software, CFD-ACE+, the processes oftransporting, creating, dividing and merging droplets are simulated successfully. Thelinear relation between the gap height and the droplet movement speed is obtained.The simulation results agree well with the theoretical model and the experimentalfindings.Thirdly, EWOD-based devices are made by two structures, the metal-Si3N4 andpoly-SiO2. For conformal and low-price hydrophobic thin film, the fluorocarbonpolymer (p-C:F) film is deposited by inductively coupled plasma chemical vapordeposition (ICP-CVD). The effects of the deposition conditions on the compositionsand chemical bonds are also analyzed, and thus the deposition conditions areoptimized. The static contact angle between the deionized water and the p-C:F filmreaches 112o. Meanwhile, Teflon~? AF 1600 from Dupont Company, which is the besthydrophobic material acquired from the business, is fabricated by spinning. Bycomparison, the performance of the p-C:F can be improved further.Lastly, based on the studies of the theories and the processes, the layout ofEWOD devices is designed. A measurement system including the peripheral controlcircuits is built up. The EWOD-based "sandwich" device is fabricated. Under thevoltages of 35 V and 45 V, the transportation and creation of droplets are successfullyrealized successfully in the media of air and the silicon oil.