新型被動式微混合器之研製

Abstract

摘要 對於兩種或兩種以上微量流體之快速混合，在微型系統與裝置裡是一項極為重要的主題，也是影響系統功能的重要因素。 本論文提出一新型被動式微混合器之設計，先以熱流數值摹擬軟體FLUENT分析微流道內的流場狀態、混合指標及壓力係數，進而改變流道結構、尺寸及擋塊角度，比較流場特性，設計出符合低壓降、高混合效果之微混合器。 依據數值摹擬結果，本文研製平面式微混合器，以矽晶圓作為基材，利用電感耦合電漿蝕刻機(ICP)蝕刻出母模，進而以聚二甲基矽氧烷(polydimethysiloxane, PDMS)翻製出模型，最後以氧電漿接合上玻璃上蓋，完成微混合器製作。實驗量測方法則利用螢光染料及食用色素分別加入甲醇與去離子水做為工作流體，經由影像分析軟體將CCD攝影機所擷取到之混合影像灰階化，再分析比較各種流道之混合效果，目的在設計出結構簡單、低壓降、高混合效能之微混合器。其中3-U turns & 2 streamlined obstacles per turn with 5 degree rotated之設計在Re = 30時具有0.79之混合指標，與蛇型流道相同，但僅需要蛇型流道壓降值之 。因此，本文所研製的微混合器將可應用於微型化直接甲醇燃料電池(Micro Direct Methanol Fuel Cell, μDMFC)有實質幫助。

Abstract It is an important topic for fast mixing two or more kinds of different μfluids in the micro systems and devices. It is also a significant factor that affected the functions of the systems. This thesis proposes a novel design of passive mixers. First, we analysis the flow fields, mixing indexes, and pressure coefficients by the commercial computational fluid dynamics software, FLUENT. In addition, we design a μmixer which meets the demands of low pressure drop, and high mixing performance by changing the μchannel structure size, and the orientation of the obstacle. According to the results of the simulations, the fabrication of the planar μmixers was based on the silicon wafer. After etching by the inductive coupling plasma etcher (ICP), we successfully fabricated our molds. Then we poured the PDMS on the molds to make our mixers and lifted the mixers from the molds. Finally, by using the oxygen plasma, we bonded the mixers with glasses to complete the chips. We use the pure methanol with fluorescent dye and D.I. water with food coloring as the working fluids. By using the charge-coupled device to capture the images, and employing the image analyzing software to quantity the concentration distribution, we can compare all the designs to find the simple structured, lowest pressure drop, and highest mixing performance mixer. Among our designs, 3-U turns & 2 streamlined obstacles per turn with 5 degree rotated design can meet the demand. At Re = 30, it has 0.79 of the mixing index, same as the serpentine design. However, it just needs three-quarter of the pressure coefficient. And we hope our design will essentially help the development of the μ-DMFC.