| Summary: | 碩士 === 國立臺灣大學 === 應用力學研究所 === 104 === Thermophoresis is a phenomenon when there exists a temperature gradient, and it would cause a matter flow. Previous research on thermophoresis suggests that it is caused by the slip flow which has been observed around particles. When a particle is fixed in an area with a temperature gradient, the flow happens in the opposite direction against thermophoresis. However, the research does not go any further and does not suggest how and why slip flow is generated. We are interested in if these two phenomena caused by the temperature gradient alike are related. If a particle is huge enough, a tiny part of the surface can be treated as a plane. Thus, the problem can be simplified and we need to consider what happens in the solid-liquid interface. In addition, slip flow is equivalent to thermos-osmosis which is defined as the flow generated by temperature gradient in the interface. The results shows that the wettability has a significant effect on the flow: here in after, the contact angle is used as the index of wettability. When θ = 30∘, driving forces equilibrated and no flow occurred. When θ > 30∘, the flow from the cold side to the hot side occurred. Reversely when θ < 30∘, the flow from the hot side to the cold side occurred. This result accords with the research of thermos-osmosis in porous materials. In addition, changing the property of particle surface shows that the direction of thermophoresis is related to its surface property. Hydrophobic PS (polystyrene) particle escapes from hot side in usual. Neither thermophoresis nor thermos-osmosis have been understand fully and almost do experiment indirectly. In our research, thermos-osmosis would not only follow the prediction but also thermophoresis. This suggest will make the research on the mechanism of thermophoresis simpler.
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