Development of Microfluidic Devices and Their Applications to Nanoparticle Synthesis

• Main Authors: Ting-Ruen Shih, 施廷潤
• Other Authors: Chen-Kuei Chung
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/39711988457144277605

博士 === 國立成功大學 === 機械工程學系碩博士班 === 97 === In microfluidic systems, mixing and driving are two basic and important techniques. In this thesis, author focus on the researches of planar micromixers and capillary-driven chip. Most of proposed micromixers are multilayer structure and complex fabrication process. They are difficult to be integrated with others microfluidic devices. In order to improve above disadvantages, obstacled micromixers and rhombic micromixers with planar structures are proposed. Results show an obstacled micromixer with gap ratio of 1/8, three mixing units, obstacled width of 80 μm and square chamber can achieve high mixing efficiency over 90% at Re > 40. Much improved mixing can also be obtained at low Reynolds number (Re < 0.1) by molecular diffusion. The other planar design is the rhombic micromixer. Simulation results show higher mixing efficiency can be achieved by more rhombus, smaller throat width, and smaller turning width. In the combination of 4 rhombi, throat width of 100 μm, rhombic channel width of 200 μm and turning width of 100 μm, mixing efficiency of 85% can be obtained at Re 119. Second part in this thesis is the fabrication of the capillary-driven microfluidic chip with long-term hydrophilic property. In general, micropumps are often integrated to microchip to drive high-viscosity liquids, such as whole blood and blood plasma. However, a moving part in the micropump results in complex design and difficult fabrication. Hence, the capillary-driven microfluidic chip without moving parts is long-awaited because of simpler design and power-free operation. In this research, glass slide and LCP film were used to fabricate the capillary-driven chip because of the high hydrophilic property without using any surface modification treatments. Flow behavior of various viscosity fluids had been tested. Average moving velocities of DI water, blood plasma and whole blood are 9.52 mm/s, 4.88 mm/s and 1.89 mm/s, respectively. This chip can actuate high-viscosity blood which is generally driven by external syringe pumps or micropumps. Third part in this thesis is the nanoparticle synthesis by a continuous-flow system. An mm-scale aging channel and obstacled micromixer were combined as a high-throughput silica synthesis system for overcoming the disadvantage of low production rate in micro-scale synthesis systems and non-homogeneous mixing in the batch system. Synthesis experiments were carried out for getting narrower size distribution under different recipes and reaction temperatures. Results show smaller nanoparticle and narrow size distribution can be obtained under lower ammonia concentrations, higher water concentration and higher reaction temperature. Larger inner diameters of ageing tubes can give smaller nanoparticles and narrower size distribution.