2011-08-012024-05-18https://scholars.lib.ntu.edu.tw/handle/123456789/710571摘要：微全分析系統可將傳統實驗室檢測的過程整合在一微型晶片上，具有減少樣本的用量、節省成本、反應迅速及節省空間等優點。微全分析系統通常由數個不同功能的微流元件所組成，分別用來輸送、混合、進行反應、分離試劑與檢體。在設計不同功能的微流元件時，微觀尺度流場型態的觀測及流場內的全域性量化是瞭解其效能與機制的重要工具，目前最常見的有螢光激發系統及uPIV (micro-particle imaging velocimetry)技術。然而，利用螢光染劑來量化微混合器內的效能，必須注意到螢光漂白(photobleaching)的問題，且其觀察區域會受到一般顯微鏡二維的限制，由於景深的緣故，並無法得知微流道不同截面上的流場情況，雖然雷射掃瞄式共軛焦顯微技術(confocal laser scanning microscopy)可以解決這個困境，然其單價太高不易取得，且微流道內的流速亦受其掃瞄速率的限制。而微觀溫度場的量測方面， 雖有Chamarthy等提出可利用PIV技術質點的布朗運動(Brownian motion)隨溫度改變[1]或螢光染劑受激發後亮度隨溫度改變的特性[2]來量測微流道內的溫度分布，但這兩種方式依然建構在螢光系統及uPIV之上，受其侷限。 在此，本研究計畫提出一嶄新構想，針對微觀尺度的微流現象，利用微紋影技術(micro-schlieren technique)開發一全域性量化及可視化技術。微紋影技術主要是藉由在光路上放置一刀緣(knife-edge)，使部分折射光無法投射在成像面上，即可得到局部亮暗程度不同的紋影影像，呈現出待測區內的折射率梯度。由於流場內的溫度梯度、密度梯度或濃度梯度皆會導致光之折射角的變化，故我們可藉由微紋影技術量測微流元件內之折射率梯度，進而推算流場內的溫度、密度或濃度變化。 本計畫書擬以兩年的時間，建構微紋影技術，針對微觀尺度的微流現象，開發一全域性的量化及可視化系統。在第一年中，主要的工作包括針對濃度或溫度與折射率之關係選取合適之工作流體，在T型微流道內進行校正實驗，得到紋影影像灰階與折射率梯度之關係，再利用此微紋影系統拍攝待測微流元件內之影像，以所得之量化結果評估其效率與觀察內部三維流場結構，並計算系統量測之不確定性。在第二年時，我們計畫設計並製作不同刀緣，比較刀緣設計與擺放位置對於系統靈敏度與解析度之影響及其適用性，並評估將此系統應用至其他純量的微觀全域量測或可視化之可能性。此外，我們亦將嘗試搭配高速攝影機，評估開發微紋影測速儀(micro-schlieren velocimetry)之可能性。<br> Abstract: Due to the unique behavior of fluids in microscale, microfluidic emerges as a promising platform for Micro-Total-Analysis-System (uTAS). To facilitate design for microfluidics aiming at different functionality, quantitative analysis of various fields is essential. Several approaches were explored by researchers. For instance, micro-Particle Imaging Velocimetry (uPIV) provides a full-field measurement of fluid velocity and is often used to study the flow structures in microfluidics. Another common technique used for performance evaluation of micromixers is Laser Induced Fluorescence (LIF). For temperature measurement, Chamarthy et al. [1-2] developed a PIV-based thermometry technique for low speed flows [1] and LIF thermometry for high speed flows [2]. Nevertheless, these methods are constrained by operational aspects such as maximum flow rate, detectable velocity gradient, and two-dimensionality of microscopy. Although confocal laser scanning microscopy is able to provide the cross-sectional details in microfluidics, the price remains high and flow velocity is limited by its scan rate. Herein, we propose a novel methodology that exploits the micro-schlieren technique for full-field measurements in microfluidics. Utilizing a knife-edge to block part of the distorted light, micro schlieren technique creates an intensity contrast that is able to depict variation of refractive index in transparent medium. To realize quantitative analysis, we will first perform a calibration procedure in a T microchennel in order to attain the correlation of image grayscale with the gradient of refractive index. Once relation between refractive index and measured quantity is known, we will be able to calculate distribution of measured quantity in target microfluidic from image produced by the micro-schlieren technique. By properly selecting the working fluids, full-field measurement of any scalar quantity, such as temperature, density, or concentration, can be taken for microfluidics. In this study, we aim at spending two years to construct, validate, and explore this novel methodology for quantitative analysis of microfluidics. In the first year, we will focus on applying the micro schlieren technique to full-field concentration and temperature measurements in microfluidic devices. Operating conditions will be optimized and system sensitivity will be evaluated. We will also carry out the uncertainty analysis to determine the confidence level in the results. In the second year, we will accommodate customized knife-edge designs into our micro schilieren system, including specialized cutoff, graded filter, and color coding. Moreover, we will explore the feasibility of applying the micro schlieren technique to other scalar measurement and micro schlieren velocimetry.微紋影技術全域性量測折射率梯度微流元件micro schlieren techniquefull-field measurementrefraction index gradientmicrofluidics