近年來微流體的技術迅速發展，其應用擴及生物科技、醫療技術，機密機械潤滑等，尤其在生物醫學檢測的應用上具有非常大的潛力。透過半導體製程使生醫晶片微小化，降低檢測樣品試劑之體積，並增加感測精度。趨動微流體可利用壓力差、電濕潤、毛細力、化學梯度、熱泳或光泳等方式，其中利用結構表面粗糙度差異驅使液滴移動的方式具有操作容易與製程簡單的優點，然而大部分的研究多是利用分段的結構梯度進行相關實驗。本文利用金屬輔助化學蝕刻，利用遞增的金屬膜厚製備出連續的奈米多孔矽結構梯度，探討液珠於結構梯度表面移動情形。

奈米多孔矽結構具有高表面積及物體吸附特性，與半導體製程有良好的相容性。多孔矽結構常利用蝕刻製備，其中以金屬輔助化學蝕刻製備多孔矽奈米結構具有製程簡易與設備成本低等優點。本文會先沉積白金薄膜以熱退火製程來製備奈米粒子，再進行金屬輔助化學蝕刻。藉由調整不同的白金膜厚和蝕刻時間來控制出相對應的奈米結構，探討奈米粒子大小、蝕刻時間和蝕刻結果的關聯性；再將蝕刻後的試片進行接觸角量測和改質，探討不同蝕刻結構和接觸角、遲滯效應的關係。最後結合以上結果，利用王水逐漸蝕刻出不同的膜厚形成梯度，進行蝕刻達到連續的多孔結構梯度。結果顯示所製備之多孔結構梯度所造成的趨動力相當小，並不足以造成液珠移動，不過透過接觸角量測和利用傾斜移動阻力的分析得知左右兩邊結構梯度具有遲滯上的差異。最後利用極性小的角鯊烷液體進行毛細擴散實驗，發現角鯊烷在擴散時，會往結構毛細力較小的區域移動較多。

Microfluidics has been grown up very fast recently, and widely used in biomedical and chemical analysis, and precision machinery lubrication. Microfluidic devices utilize microfabrication to minimize thier size, which can reduce the amount of test samples and reagents, enhance the accuracy of detection. The droplet-based microfluidic device is one of the promising technologies. The droplet can be driven by pressure difference, electro-wetting, capillary force, chemical gradient, thermophoresis, photopheresis and so on. Among these, the capillary force or the use of surface roughness changes has the advantage of simple operation and simple manufacturing process. However, most of the literatures only demonstrate the feasibility of water movement between two discrete surfaces with different roughnesses. In this study, we use metal assisted chemical etching to make nano porous silicon structure with continuous change in the surface roughness and investigate the drops movement on the surface.

Porous silicon structure has large surface to volume ratio Metal assisted chemical etching process is an simple and cost effective way to make porous silicon. In this research, we deposit platinum films and use thermal annealing to make nano particles for the following metal assisted chemical etching. The corresponding nano structures can be made by adjusting different thickness of platinum films and different etching times. The relationship between different thickness of platinum films and etching times is investigated. The contact angle and hysteresis are measured to study the wettability of the porous surfaces. Different metal thickness is made by steady pulling the sample out of the etchant, that is then annealed and etched to produce porous structural with continuous structure size gradients. The results show that the driving force given by continuous porous structural gradients is very small, and is unable to drive the liquid drops. On the other hand, we find that there is a different hysteresis between the structural gradients on the two sides from the contact angles measurements of the inclined surface. Finally, we use squalane to test the capillary motion on the surface, which shown that squalane will move further toward the area with smaller pore structures.

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