本研究主要目的為藉由量測微流道內壓力與溫度分佈以探討微尺度下稀薄效應與壓縮效應對流場的影響。傳統壓力感測技術受限於體積大小而無法密集地排列於微結構中，僅能於入/出口作間段式量測，於流道內部則難以量測，其量測結果多為一維、間斷且非連續性的，空間解析度較為不足；於較低壓力區間因量測機制所仰賴之物理性質變化多隨壓力降低而逐漸趨緩，使得低壓情況下靈敏度較低，故近年來探討微流道內稀薄效應與壓縮效應對流場之影響多以數值模擬方式進行。有鑑於此，本論文使用壓力/溫度螢光感測技術，選取合適的螢光分子，利用其光化學機制進行量測，並透過光學量測系統擷取影像以獲得微流道內全域性的二維壓力/溫度分佈，空間解析度可達3.73 μm/ pixel且敏感度不因壓力下降而降低，可藉此探討微流道內稀薄效應與壓縮效應對流場造成的影響。
本研究主要透過壓力/溫度螢光感測技術量測長0.5 cm、寬50 μm與100 μm，及深50 μm的微流道內壓力與溫度分佈，並透過螢光顯微鏡搭配4X顯微物鏡擷取螢光訊號，藉此提高實驗量測的空間解析度並減少因激發光入射角度所造成的陰影區域，最後利用即地校正方式輔以逐點影像校正法提高實驗量測準確度。由於壓力螢光分子不僅受到壓力改變而有螢光亮度變化，亦因溫度變化而影響螢光強度，故於壓力量測前須先針對相同的實驗設置作溫度量測。本研究利用溫度感測技術量測各實驗條件下微流道內溫度分佈，實驗結果顯示，於連續流範疇中流體因顯著的流道入/出口壓力差而產生壓縮效應，速度梯度增加使得摩擦係數增高，導致流道下壁面由入口向出口逐漸增溫；然而，隨著流場之紐森數提高，稀薄效應越為顯著，流場進入滑移流範疇並且出現速度滑移與溫度躍昇現象，使得此增溫現象逐漸趨緩。另外，於各實驗條件下流道內溫度差皆小於2.3 ℃，此溫度變化對於本研究所使用之壓力螢光感測塗料所造成的壓力量測誤差小於1 %。
了解PSP壓力螢光感測技術受溫度的影響後，於相同實驗條件下量測微流道內部的壓力分佈情形，並與藉由Navier-Stoke方程式搭配一階滑移邊界條件所求得之解析解相比較，藉此驗證基本流場的壓力量測精確度。就壓縮效應的討論中，藉由改變微流道入/出口壓力差，檢視流場因壓縮效應所產生的非線性壓力分佈曲線變化情形，實驗結果顯示流道軸向壓力分佈隨著入/出口壓力差由1.9增加至4.6而越趨於非線性，與線性分布之無因次最大偏移量由0.02增高為0.23，無因次化之發生位置則由0.47延後至0.62。然而，隨著流場內紐森數提高，流體越趨於稀薄，流道邊界處逐漸出現速度滑移與溫度躍昇現象，導致壁面出現速度不為零的情況、流道軸向之流速逐漸增加且摩擦係數漸小，使軸向壓力分佈越趨於線性而近似於無滑移的不可壓縮流場。當出口紐森數由0.006提升至0.008，相對應之無因次最大偏移量由0.25降至0.07，出口紐森數達0.01以上時，其與線性分布之偏移量皆已趨近於0而近似於線性分布。本研究利用壓力/溫度螢光感測技術，成功量測得微直管流道於不同的入/出口壓力差與紐森數之內部壓力分佈，並藉此探討壓縮效應與稀薄效應之相互抑制情形，了解微流道內於不同壓力條件下所產生的流場現象，提供微機電產品於設計與開發上的實驗資訊。

The purpose of this thesis is to investigate compressibility and rarefaction effect in micro gas flow by measuring pressure profiles in microchannel. Both of them have been sudied by using micro pressure sensors which are fabricated with the comventional MEMS technique in the past decades. The spatial resolution and low-pressure sensivity for conventional pressure sensors is not enough due to its size and membrance design. As a result, most of the studies discussing compressibility and rarefaction effect in microchannel were carried out by the numerical simulation.
In this study, pressure-sensitive paints (PSP) and temperature-sensitive paint (TSP) are applied inside rectangular microchannel (0.5 cm x 50 μm/100 μm x 50 μm) to obtain the globl flow field with detailed pressure and temperature data. The spatial resolution for the PSP/TSP measurements has improved to 3.73 μm/ pixel by integrating a microscope with a 4X objective lens in the system to collect the luminescent signals. In order to improve the accuracy of PSP measurements, in-situ and pixel-by-pixel calibration are applied in data processing. Therefore, compressibility and rarefaction effects can be clearly observed in microchannel with the pressure data obtained by PSP measurements.
Due to the temperature dependence of PSP sensors, the luminescent intensity of PSP sensors does not only change with pressure but also temperature variation. Hence, it’s nescessery to examine the temperature distribution inside the microchannel by TSP sensors. The result shows that the axial temperature along microchannel increases in contimuum flow regime; however, the temperature inceasement can be barly observed while the Knudsen number is greater than 0.001. Additionally, all the temperature defference inside the microchannel for each flow condition is less than 2.3 ℃. The difference of luminescent intensity of PSP (PtTFPP/ PDMS) is less then 1% in 2.3 ℃ temperature defference. Thus, the pressure distribution inside the microchannel can be obtained with PSP technique without temperature effect.
In pressure measurements, the PSP results show that the nonlinear pressure distributions in microchannels which are caused by compressibility effect. The dimensionless deviation from the linear pressure distribution raised from 0.02 to 0.23, and the dimensionless location of the maximum deviation increased from 0.47 to 0.62 with increasing inlet to outlet pressure ratios from 1.9 to 4.6. On the contrary, rarefaction effect reduces the curvature of pressure distribution inside the microchannel as the Kudsen number increases. The dimensionless deviation from the linear distribution reduced to 0.07 from 0.25, and the dimensionless location of the maximum devication also decreased due to the gaseous slip at the wall as the outlet Knudsen number increased to o.oo8 from 0.006. According to the experimental results, compressibility effect and rarefaction effect restrain each other in microchannel in terms of nonlinearity of pressure distribution.
In conclusion, the feasibility of PSP/TSP sensors in microchannel measurements has been demonstrated in this study. Compressibility and rarefaction effects in microscale have been discussed with the detail pressure information obtained by PSP technique. The PSP/TSP results are valuable for future gas-MEMS development.

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