橢圓微型模穴之微液體填充研究

Abstract

本論文之研究目的在於製作橢圓模穴為主之微流體裝置，並藉由實驗觀測表面張力、附著力、慣性力對液體填充過程中之影響。實驗中，流道製作方式有二，一為PDMS翻模而成，另一為以MEMS技術於晶圓上蝕刻流道；根據偉伯數的變化、模穴大小、模穴旋轉角、改變橢圓模穴壁面材質和化學處理改變壁面性質，探討波前與其流動現象，並且使用微粒子影像測速法(PIV)重現會包圍氣泡模穴填充過程之速度，藉以釐清會發生包圍氣泡前後實際流動狀態。 實驗結果顯示，容易在模穴產生氣泡包覆現象之情況如下： 1.偉伯數相同，橢圓模穴旋轉後，越靠近進口流道時。2.橢圓模穴旋轉角相同的，偉伯數越高時。3.偉伯數相同，PDMS模穴以PDMS材質封裝比以玻璃封裝時更易包覆氣泡。4.偉伯數及模穴材質相同，相同面積但形狀較寬闊的模穴。另外在微粒子影像測速法過程中發現在彎角大的模穴中，因為進口慣性力被表面張力抵銷後，速度向量會在波前呈現均勻的分佈，導致填充時液面不足以到達模穴角落填充，造成最後的包覆氣泡現象。 另本研究中，尚有以化學處理法處理，改變已封裝好之模穴內部親疏水性。針對PDMS模穴而言，實驗中的氧電漿再處理法、界面離子活性劑處理法，均會使原本是疏水性質的模穴內壁轉變為較親水。研究結果顯示，能使模穴內變親水的效果，氧電漿再處理法最佳、HEMA處理法最差。針對silicon材料的流道而言，通入等向性蝕刻液TMAH後，能再度蝕刻模穴底面，因為模穴內部非平滑表面，所以比較蝕刻處理前的模穴、處理15分鐘的模穴、處理30分鐘的模穴的填充結果，因模穴底部表面型態的變化，會出現疏水、親水、相對疏水的現象。

The purpose of this thesis is to manufacture oval disk-shaped micro fluidic device for observation and also to examine the effect of surface tension, adhesive and inertial force in the filling process. Two methods to manufacture micro channels and micro chambers in this experiment are PDMS molding process and MEMS technology fabricating on the wafer. The liquid filling process is analyzed at variance value the Weber number, size of the chambers, aslope angle of the chambers, associated with the changes in materials of the walls of the micro chambers, and the chemical changes in processing. Furthermore, in order to clarify the actual circumstance of flowing before bubble entrapped and after, PIV is adopted in this experiment for reconstructing the speed distribution of filling in the bubble-entrapped chambers. The result of the experiment shows some circumstances when bubble entrapment occurred: 1. With the same Weber number, the degree between the chambers and the inlet channel decreased. 2. With the same degree between the chamber and the inlet channel, the Weber number increased. 3. The PDMS micro chambers package with PDMS sheet was easier than that with glass sheet. 4. With the same Weber number and the same property of the wall in the chamber, the superficies of the chamber was equivalent but the shape of the chamber was different. In addition, inertia in the inlet channel was offset by the surface tension in big curve chambers, and the speed quantities would spread evenly in the front shapes. Consequently, front shapes failed for reaching chamber corners and filling, and bubble entrapment occurred. Chemical treatment is also used to change the hydrophilic and hydrophobic quality inside the packaged chambers in this experiment. In regard to PDMS chambers, surfactant and treatment O2 plasma for the second time changed the hydrophobic chamber walls into somewhat hydrophilic. Moreover, to make chamber walls become hydrophilic, treatment O2 plasma is better than treatment HEMA in comparison with treatment HEMA in references. In regard to silicon channel, pouring TMAH would etch the bottom of the chambers once more. Inside the chambers was not smooth; when comparing the chamber walls used treatment TMAH for 15minutes and 30minutes with those had not used treatment TMAH, different filling phenomenon would appear while pouring water in chambers.