摘要

本論文的主要目的是探討具不同濕潤性質之微流道內流體或微粒之輸送現象。我們使用微型模造技術以PDMS為材料來製作微流道系統，並配合所發展具選擇性的表面改質技術來對微流道內進行區分濕潤性質的差異。

本論文包含兩部份。第一部份是探討於不同親疏水性質之T型微流道內之流體流動行為。我們測量水進入疏水性支管所需要的靜壓來衡量濕潤的難易程度。我們同時發現管徑愈小所需的液柱高愈高。我們利用Young-Laplace Equation解釋此實驗相關的力平衡，預測結果與實驗相當符合，故我們可根據流道管徑大小與親/疏水性的對應關係，發展簡易但有效的「微型閥」控制元件。

論文的第二部份，我們觀察油珠在具不同親疏水性質的Y型分岔微流道中運動，發現油珠可因親疏水差異所造成之表面滑移效應不同而偏向親水端移動。然而油珠的運動模式可隨流量不同而改變。這是由於表面效應與其它流體力學效應同時作用的結果。我們並提出尺度分析來估計各相關效應之強弱並可完全解釋實驗觀察結果。此部份之研究對於含不同親疏水性的混合微粒系統之分離可提供有效指引。

Abstract

The aim of this thesis is to examine the transports of fluids or particles in microchannels with non-uniform wettabilities. We utilize the PDMS-based microfabrication techniques to fabricate microchannels. With the aid of the techniques developed by our group, we can selectively modify surface properties of a microchannel for our study.

There are two parts in this thesis. In the first part, we examine the behaviors of a liquid in a T-shape microchannel that has a hydrophilic/hydrophobic contrast between the main and branch channels. We measure the hydrostatic pressure (through the liquid height), the minimum driving force required for the water to enter the hydrophobic branch, to characterize the effect of the wettability on transporting the liquid in the channel. It is also found that the smaller the channel width, the greater the liquid height. We also employ the Young-Laplace equation to explain the underlying force balance, and find an excellent agreement between experiment and theory. This research can be applied to develop “microvalves” for controlling the fluid motion using hydrophilic/hydrophobic differences.

The second part of the thesis is to examine the motions of oil drops in a bifurcating microchannel with hydrophilic and hydrophobic branches. We find that the drops can move towards the hydrophilic end due to the difference in surface-slip effects. The behaviors of the drop movements, however, can change at different applied flow rates. This is caused by interactions between surface effects and other hydrodynamic influences. We devise a scaling analysis to estimate the orders of magnitudes for relevant effects. The analysis also provides a rationale for explaining our observations. This research has potential applications in separating particles with differences in their affinities to the channel surfaces.

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葉宗儒，具圓形凹槽結構的微流道系統之流動特性探討及其在微混合器之應用，碩士論文，國立成功大學，2005。