微流體系統中薄膜幫浦與流量感測器之研究

Investigation on membrane pump and volumetric thermal flow sensor for a microfluidic system

吳俊輝(Chun-Hui Wu)

指導教授 ： 陳炳煇

國立臺灣大學/工學院/機械工程學研究所/博士(2016年)

https://doi.org/10.6342/NTU201603070

摘要

本論文提出一新式量測方式用來量測薄膜幫浦之流容，並提出四個新理論公式用來定量分析及六個新理論公式用來定性預測其流容值。藉由量測薄膜中心點撓度以計算其對應之壓力值，進而決定其流容值。並探討PDMS薄膜厚度與楊氏係數之關係，並由實驗數據提出一線性關係式。在撓度為非線性時，流容之實驗數據與理論預測值兩者之間表現出相當一致之趨勢。
本論文亦開發兩形，洞形與啞鈴形，共五種不同之微加工熱式流量感測器，用於進行低流量之量測。其中感應元件是由parylene-C薄膜包覆於兩片薄膜式鉑電阻。洞形感測器分別採垂直與水平放置以分析其靈敏度差異，將洞形感測器採垂直放置時，感測器與水流方向垂直；採水平放置時，感測器懸空於流道正中央，與水流方向平行。而洞形感測器中有一孔洞能讓流體從中穿過，藉此帶走大量之熱以提高靈敏度，缺點為流阻較大。實驗結果顯示靈敏度不如預期，因此考慮增強隔熱、提昇效率、並降低阻力後，重新設計感測器外形並開發出一新式啞鈴形感測器。實驗結果顯示，啞鈴形感測器之最佳靈敏度在功率為0.13 mW時，能高達7.7 mV/(μl/min)，且能夠量測到0.05 μl/min 之體積流率及量測解析度。最後並與相關文獻進行性能比較以評斷本文所開發之流量感測器。

關鍵字

流容 ； 微流體 ； PDMS ； 楊氏係數 ； 熱式流量感測器 ； parylene-C ； 流量量測

並列摘要

A novel approach was proposed to measure the hydraulic capacitance of a microfluidic membrane pump. Membrane deflection equations were modified from various studies to propose six theoretical equations to estimate the hydraulic capacitance of a microfluidic membrane pump. Thus, measuring the center deflection of the membrane allows the corresponding pressure and hydraulic capacitance of the pump to be determined. This study also investigated how membrane thickness affected the Young’s modulus of a polydimethylsiloxane (PDMS) membrane. Based on the experimental results, a linear correlation was proposed to estimate the hydraulic capacitance. The measured hydraulic capacitance data and the proposed equations in the linear and nonlinear regions qualitatively exhibited good agreement.
Micromachined thermal flow sensors for measuring liquid flow down to 0.05 μl/min were developed. The sensing element is a parylene-C thin film with two thin film platinum resistors as heating and sensing elements. The sensors are integrated with AWG 24 Teflon tubing and additional two external constant resistors to form a Wheatstone bridge. The efficacies of the orifice type sensors in two configurations, vertical and horizontal were also investigated. In vertical configuration, the sensor was arranged perpendicular to the flow direction. The orifice flow allows maximum heat transfer from the sensor to the flow but leads to higher flow resistance. After redesigning the geometries of the sensor, the dumbbell type thermal flow sensor was further developed. The sensor is suspended in the middle of the channel to improve thermal insulation and achieve better sensitivity. The sensors have demonstrated a flow rate resolution below 0.05 μl/min. The experimental results show that the sensor has a sensitivity of 7.7 mV/(μl/min) at 0.13 mW power consumption and 0.05 μl/min volumetric flow rates. Comparison with related literatures has been made to judge how good the flow sensor developed in this study is.

並列關鍵字

hydraulic capacitance ； microfluidic ； PDMS ； Young’s modulus ； thermal flow sensor ； parylene-C ； flow rate measurements

參考文獻

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