膠體粒子在溫度梯度下的受力與交互作用

Force and Interaction of colloidal particle under temperature gradients

曾梓維(Tzu-Wei Tseng)

指導教授 ： 江宏仁

國立臺灣大學/工學院/應用力學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.10643

摘要

膠體粒子在溫度梯度之下，沿著溫度梯度方向的運動的行為稱之為熱泳，由於液體中熱泳的行為非常複雜，迄今仍然沒有一個完整的理論能對熱泳現象進行解釋，因此在不同的外界環境下，許多模型被提出．在顆粒熱泳的運動機制中，有一個模型是根據膠體粒子電雙層內的離子，在溫度梯下產生滑移流，而使得膠體粒子產生運動，這個滑移流在實驗中有被觀察到，但是此滑移流目前尚未有直接的量測，除此之外目前熱泳研究中，大部分都藉由膠體粒子的熱擴散係數和索瑞特係數來進行探討，對於膠體粒子在熱泳中的受力卻很少人討論．

因此在我們的實驗中利用光鉗系統，在不同的外界環境下對於單顆膠體粒子在熱泳下的受力進行量測，我們亦利用粒子受力的量測，來研究兩顆膠體粒子同時受熱泳下，膠體粒子間的交互作用；實驗結果顯示單顆膠體粒子受到的熱泳力會線性依賴溫度梯度和膠體粒子大小，而在兩顆膠體粒子的研究中，發現當兩粒子距離足夠近的時候，在沿著溫度梯度方向兩粒子的受力會同時變小，除此之外實驗中我們也觀察到粒子周圍滑移流的動態，我們利用此滑移流的流速改變，來驗證粒子間交互作用的結果．

關鍵字

膠體粒子 ； 熱泳 ； 滑移流

並列摘要

In the presence of a thermal gradient, the motion of colloidal particles drift along a temperature gradient is known as thermophoresis. There is no clear theory so far to explain the phenomenon of thermophoresis because of the complicated interaction between particles and solvents. Therefore there are many transport mechanisms of thermophoresis which depend on different conditions are reported. One of the mechanisms of particle thermophoresis is caused by slip flow which is about the moving ions inside electric double layer. Slip flow was observed others studies, but it hasn’t been directly measured until now. Besides most of the researches study the effects of thermophoresis by measuring Soret coefficient and thermal diffusion coefficient, however thermophoretic force of colloidal particle is rarely discussed.

In our experiment, we set an optical tweezers system to measure force of colloidal particle under temperature gradients in different conditions. In addition we studied the interaction of two colloidal particles by measuring force. We found the force of colloidal particle is linearly dependent to temperature gradients and particle size. On the studies of two colloidal particle interactions, we found that when two particles get close enough, force of two particles along the temperature gradient become smaller. Moreover we observed the motion of slip flow around the particle by trajectories of tracers. By measuring the changes in velocity of tracer particles we could verify the results of interaction of two colloidal particles.

並列關鍵字

Colloidal particle ； thermophoresis ； Slip flow

參考文獻

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