微細圓盤孔穴內之微流體流動現象分析

Abstract

本論文之目的在於製作一微流體裝置，藉由實驗來觀測液體的流動現象並探討表面張力、附著力及慣性力對其之影響。由實驗結果得知，以我們目前所設計微流體裝置之尺寸與操作條件下並不會使液體在圓盤孔穴中產生渦旋之現象。由於體積流率與圓盤孔穴之截面積大小皆會影響液體在其內部流動時的速度與慣性力，進而造成流動現象的改變。因此，應用圓盤孔穴的幾何尺寸作依據來計算韋伯數，較能詮釋在慣性力較強條件下實際的流動現象。然而，若是以附著力為主要之作用力進而影響流動現象的實驗或操作條件，皆不能用韋伯數來預測或解釋其現象，比如預測不同的液體種類或深度下微細圓盤孔穴中之流動現象。因為此二者皆會嚴重地改變液體與壁面附著力之影響程度，使得單靠韋伯數一個參數不足以詮釋微流體的流動現象。此外，若用表面張力較小的液體當工作流體，當其流經深度較小的圓盤孔穴中，因液體之附著力之作用較為顯著，周圍的液體將包住中心處之空氣，使得在出口區之前有產生氣泡的可能性。

This thesis purposes to manufacture a micro fluidic device for observation and examination of the effects of surface tension, adhesive force and inertial force on the flow phenomena. Experimental results show that phenomena of vortex won’t be produced during the conditions of operation in the present study. Since the volume flow rate and cross- sectional area of the circular disc-shaped chamber influence the velocity and inertial force and then the flow phenomena will be affected, the Weber number decided from the geometric sizes of chamber seems more appropriate to interpret the flow phenomena under the conditions where the inertial force is significant. However, due to the adhesive force between solution and wall surface, kind of solution and depth will significantly affect the flow phenomena, Weber number couldn’t properly predict or explain the flow phenomena. And because the adhesive force influence apparently, in case of smaller surface tension of work fluid or not deep depth of micro channel a bubble may be formed prior to outlet of the chamber.