| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 99 === This study investigates two topics. The one is droplets mixing with different surface tensions, and these research results could be the reference for working fluids in the digital microsystem. The other one is developing a novel droplet-manipulation method, which enhances the working efficiency of micro-droplets without destruction of biochemical properties.
To analyze the droplets mixing behaviors, the coalescence are visualized by a high-speed camera, and the internal flow patterns are resolved by micro-PIV and micro-LIF. Experiments show that a pair of symmetrical vortices droplet happen only when the higher-surface-tension droplet collide the lower one, and hence the initial mixing indices are higher. However, the overall mixing efficiency depends on the ratio of contact area to total volume and the location of the fluid with high cohesion instead of surface energy differences.
Transport distances and directions of droplets on the surface with molecular or structured density gradients are limited; therefore, this research proposes a new manipulation method. The method stretches elastic surfaces with hierarchical structures to control structured densities and to generate density gradients, so that droplets alter their wettability and move without change of biochemical properties. This study currently has proved that the novel control concept is practical, and focuses on the design and manufacture of pliable components and stable stretch devices.
These results can be applied to biochemical tests and drug developments. The study expects that the mixing investigation is useful to mixing efficiency, and that the new manipulation method will advance droplets’ capability of transport and reacting.
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