| Summary: | 碩士 === 國立成功大學 === 工程科學系碩博士班 === 96 === Microfluidic technology has shown a reliable and promising new route for the formation of uniform emulsions in the past decade. In this thesis, a novel method for active control the internal droplet number of double-emulsion droplets was demonstrated. Moreover, various sizes of internal and external droplets were also successfully formed. This investigation presented a device integrated with T-junction, moving wall structure, and sheath-flow junction components, utilizing in water-in-oil-in-water (W/O/W) multiple emulsions. During the process, inner water-in-oil (W/O) single-emulsion droplets were formed by a T-junction design first, and then the droplets were subdivided into smaller droplets with equal size by passing through a microchannel connected with a series of T-junctions (3 branches). Meanwhile, the moving wall structures beside the branches could be exploited to control the number of the subdivided droplets by alternative blocking or releasing the branches. Following these steps, a certain number of subdivided droplets could be formed, and then moved out together. Finally, double-emulsion droplets with 1, 2 or 3 internal droplets were formed by using a sheath-flow junction microfluidic device. Experiment data demonstrated that the inner and outer droplets could have narrow size distributions with coefficients of variation in diameter of approximately 5%. At last, another extended design with 10 branches was used to subdivide a water-in-oil droplet into 10, and formed uniform double emulsions with 10 inner droplets. Relationships between the inner droplets formed by T-junction at inlet and the relevant sub-droplets formed by T-junctions at outlet were proved. Based on the results, sub-droplets with various sizes could be obtained by adjusting the relative flow rates of R1 (inner phase) and R2 (middle phase). The developments of these microfluidic devices are promising for a variety of applications in the cosmetics, pharmaceutical, and food industries.
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