微流道中被動懸臂樑式閥門之模擬與研製

Abstract

摘要 微流體系統中通常包含了微流道、微型閥、微致動器以及微感測器等組件，可以整合各種功能應用於不同領域。本研究首先以數值模擬方法，應用有限元素法分析軟體探討懸臂樑式閥門在不同壓力下作動的關係，目的在研析出小壓力下能驅動的微型閥門。閥門在流場中受力變形的程度，與閥門的機械性質有關，欲在低壓力驅動時，閥門材料需有較低的楊氏係數與較高的蒲松比，以往所使用的材料為矽或鋁，楊氏係數在169 GPa及200 GPa之間，相當強硬；而聚二甲基矽氧烷(PDMS)的楊氏係數為1.4 MPa、蒲松比為0.49，即具備前述的特性，故本論文採用PDMS做為懸臂樑式閥門的材料。 本文在進行數值模擬前，先測試網格的獨立性，以確定計算結果之準確性，並以合宜的網格數進行接下來的模擬，模擬結果顯示閥門位移與壓力差呈一線性關係，且對三維流場進行模擬，並比較兩者的結果，二維流場的模擬結果與三維流場中閥門對稱面的模擬結果接近，並可得知閥門在三維流場中壓力分布的趨勢。 本文接著以微機電技術製作出PDMS微型閥模組，並以注射式幫浦做為微閥效能測試的驅動源。本文製作出兩種尺寸的微閥做比較，一厚度為5 μm、長度為270 μm，另一厚度為10 μm、長度為290 μm，以推出液體量與抽回的液體量的比值做為效能依據，其中厚度為10 μm、長度為290 μm的微閥在操作頻率0.25 Hz，推出液體量與抽回的液體量的比值比值為1.6，且對250 μm寬的微流道，閥門長度設計為290 μm較佳。

Abstract A micro-fluid system usually involves micro channel, micro valve, micro actuator, and micro sensor. It can be applied to different areas as integrating with other devices. This study employs FEM computational software to investigate how a cantilever type valve acts under various pressures and to develop a micro valve which can be operated under low pressure. PDMS material has Young’s modulus of 1.4 MPa and Poisson ratio 0.49 favorable for a passive micro valve. This study uses PDMS material to manufacture cantilever type valves. Before numerical simulation, the grid independence has been tested in order to assure the accuracy of simulation. Simulation results shows a linear relationship between displacements of valves and the driven pressures. Results of 2D and 3D simulations are also compared. Bases on the numerical works, micro valves were fabricated by MEMS techniques, and a syringe pump was used as an actuating source. Two sizes of micro valves were fabricated. The performance of the two valves are compared based on the infuse/withdraw ratio. The ratio of the valve with 290 μm length shows a better pumping capability of 1.6 under 0.25 Hz operating frequency.