本文研究的目的在於利用微機電系統製程技術，實際製作微小化結構，針對流經微管道之不同粒徑的粒子，藉粒子擴散運動達到分離之效果，探討微管道變化與粒子擴散分離間的影響。製作方式是以塗佈感光性光阻，利用微影蝕刻方式在矽晶圓轉移圖案，搭配對準方式翻模製成的polydimethylsiloxane (PDMS)接合於玻璃片上，成為本研究的微管道系統，從平面注入與匯合管道改變至利用堆疊光阻圖案方式在單一矽晶圓上製作三維結構，設計匯合管道長度為34 mm，寬度為2 mm，擴散總高度為100 μm，應用在含0.1 μm與 2 μm粒子的溶液，此微管道容許微量的溶液，在不超過玻璃片尺寸下達到擴散分析之效果，最後利用有限範圍探討快速分離、擴散之產物效率高的設計參數。
　　在物理理論方面，討論不同尺度粒子流經匯合管道時，會經歷阻力、粒子的擴散等，本文並以不同的管道結構作測試。同時發現管道設計擴散高度參數的增加將提高流體的對流效應，降低粒子停留管道時間與擴散效果，而寬度的增加卻會使粒子在管道內的擴散效應相對與流場的對流比較，是有增益的效果；同時，微管道內檢測溶液的不同，在低雷諾數環境下，溶液的黏滯度與粒子擴散效果是有關的，粒子擴散較易發生於相對較低黏滯度的溶液中；藉由微管道中粒子本身之擴散係數與管道幾何形狀或壓力的探討；整合微製造、微流體、微圖形結構技術達成實驗室晶片之擴散分析的構想。

　　The study describes a Micro Electro Mechanical Systems,（MEMS）fabrication technique for building three-dimensional（3-D）microchannels using polydimethylsiloxane（PDMS）elastomer. The master for each layer is formed on a silicon wafer using an epoxy-based photoresist. PDMS is cast against the master producing molded layers containing channels. Miniaturization of micro fluidic channels assays of channels change, such as length, height and width. We have designed and built a channel for separation by diffusion. The length of the confluence channel is 34 mm, the width is 2 mm and the height is 100 μm, Experiments were performed at flow rates of 5 μl/min. In this condition, using 0.1 μm and 2 μm sphere in micro-channel, our device allows quantities of fluid in picoliter to be analyzed on devices. We also set the constraint to optimize the geometry which can maximize the volume flow rate of product stream.
　　Theoretical studies of different size particles in the confluence channel have been performed as function of the drag force and diffusivity. The results were validated using different microchannels in two- and three- dimensional channels. We found that the increase of length of channel and diffusion distance can enhance the convection in flow, and suppress diffusion effect in the microchannel. The separation by diffusion can be implemented in a microfluid system in which the dimensions of the channels are sufficiently small that only low-Reynolds-number (Re<<1) flow can occur. Changing the geometry or pressures can control the microchannel flows. The channel combines microfabrication, microfluidic and surface micropatterning techniques for integration of the device into a “lab-on-a-chip” diffusive analysis system.

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