多重乳化產生分散在另一不相溶液體中的液珠，其內部包覆更小的液珠，其中以水-油-水(W/O/W)的形式可承載水溶性的藥物，具有極大的應用潛力。在微流道內以乳化方式形成的液珠，取決於流體對流道壁面的親疏水性。因此本研究主要目標是以微機電製程，設計與製作微流道，用軟微影製程製作兩片PDMS流道接合而成立體結構的特性，以去離子水當作外層與內層流體，油酸作為中間相作為實驗流體，在疏水的流道內形成O/W，可避免表面改質的繁複程序，再依據上游端流道的幾何形狀，迫使液體匯集，使內層流體被中間層流體環繞形成層流，在下游處以flow-focusing被外層流體因Rayleigh-Plateau不穩定性斷裂形成W/O/W形式的多重乳化微囊胞。本研究目前可成功的在毫米尺寸的微流道中，透過簡單控制氣壓推進液體的壓力，在毫米尺度的微流道上可製作500μm ~1200μm粒徑大小的多重乳化的微囊胞。利用注射式幫浦控制，在微米尺度的微流道上，可產生粒徑大小為100μm ~500μm的多重乳化的微囊胞，調整輸入的流量或致動壓力可控制包覆膜層的厚度與包覆液珠的粒徑尺寸。未來將通入具感光性的高分子溶液或脂質作為油相來包覆水溶性藥物或生物細胞，製作粒徑小於50μm的多層乳化微囊泡，期望在生醫微流體、藥物釋放研究領域上有所應用與發展。

This study presents the development of 3-dimensional PDMS microfluidic channel network that is capable of generating water-in-oil-in-water double emulsions in a controlled manner. Microfluidic channels are designed to guide the individual and coupled flows, which are driven by 3 independent sources, and to manipulate the flow fields along the emulsification process. In addition to liquid flow-rates and channel geometries, interfacial tensions are also critical to the emulsification process. By introducing surfactant molecules to the interfaces, the breakup process and the emulsion structure are stabilized as desired. In the prototype demonstration, plastic molds with millimeter and micrometer-sized channels were fabricated by milling and multi-step lithography processes, respectively. The molded PDMS plates were surface treated and bonded irreversibly to form stereo channel network. Afterward, the generation of water-in-oleic-acid-in-water double emulsions was performed by the fabricated PDMS devices with various flow-rate and surfactant combinations. It was verified in the trials that: (1) totally three different breakup modes can be successfully induced to generate double emulsions, and (2) the sizes and the core-to-shell ratios of the resulted emulsions can be controlled independently by the outermost and the inner flow-rates, respectively. As such, the presented double emulsification scheme could potentially realize the consistency and controllability on the emulsion structure and size distribution, which are desired for various biological and pharmaceutical applications.

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