近年來微全分析系統蓬勃發展，利用微機電製程製作之生醫晶片具有檢測樣本少、廢棄物少、低成本及可攜帶之優點，且目前已有細胞研究、細胞分離、藥物檢測等多方面應用。
利用兩道匯流流體在微管道中層流流場特性，造成一非線性濃度分布曲線。在神經細胞反應中，藥劑濃度梯度之控制為主要參數，而一般線性化濃度分布之目標則常使用管道形狀與幾何配置進行濃度分布探討，此類型管道設計通常較難製作且流阻較高。
本研究利用擴張管道放大濃度分布區間，可生成穩定且連續分布的濃度場，然利用支管於擴張區後端收集流體，可得特定且非連續之濃度分布。透過數值軟體進行濃度分布之模擬，並利用數值模擬結果與流阻理論輔助管道設計，使支管濃度分布呈線性化之結果。
本研究藉由擴張式擴散晶片之實驗與模擬，探討停留時間、擴張區幾何外型、收集區阻力比例對濃度場造成之影響，使我們對擴張式擴散晶片之流場特性與機制有進一步了解，可作為濃度分布管道設計研究之依據。

Recently, micro total analysis systems (μ-TAS) are beginning to appear in a wide range of applications. The chips fabricated by photolithography techniques bring the advantage of small volumes of fluids, reagents, and
waste. The miniaturized chips are also inexpensive and portable. The microfluidic system has be utilized in cell-base assays, cells separation, pharmacological activity, and etc..
Using two streams in a laminar flow field, we can get a nonlinear concentration distribution. The manipulation of concentration gradient is important in cell response, like neurocyte or cancer cells. Usually, linear concentration gradient profile can be manipulated by the complex microchannel geometry or spatial configuration. Such designs have high flow resistance and they are hard to fabricate.
In this study, we have found stable, extended and continuous concentration distribution in the expansion part of microchannels. We employ eight outlet channels to obtain the specific and fragmented concentration profiles. We have conducted experiments and used both the simulation and flow resistance theory to aid channel design and obtain linear concentration profile.
The study investigated the effect of residence time, the geometry of the expansion channel, and the resistance ratio of the exit channels on the concentration distribution. By exploring the parameters above, we have
gained better understanding of the characteristic of the present diffusion-based flow-field.

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