熱動式無閥微泵的研究

Abstract

本論文研究的目的在於研製微流體系統中的重要元件：熱動式無閥門微泵。微泵元件包括微薄膜致動器及厚深腔體結構。在元件的設計製造方面是利用半導體相關製程技術結合機械結構設計理念而成。 微薄膜致動器驅動的原理是利用不同材料間的熱膨脹係數差異，在加熱過程中薄膜受熱而膨脹變形。薄膜致動器的結構是由三層薄膜所構成，其中上下兩層是 bimorph 結構，由 SiNx 和鋁兩層所構成，而中間為銅線圈的加熱層。微薄膜致動器可利用變動溫度而使薄膜震動。利用有限元素分析軟體 ANSYS 5.3 分析薄膜變形量和溫度的關係，可作為實驗測試時的參考及得到最佳化的薄膜厚度來得到最大變形量。利用半導體製程所做出的薄膜大小為780 μｍ 見方。當輸入功率 1 瓦特時，可得到薄膜變形量 25μｍ。 在微泵的厚深腔體結構部分，我們採用改良過的微小擴散╱噴射型導流道取代一般微泵腔體的被動止回閥門。此一設計，在流道入口處修改為圓角，在出口處則增加突出的長條結構。由理論得知此一設計可在每一個進排水系統中，得到較大的淨排水量。為了配合微薄膜致動器大變形量的特色，我們採用 "LIGA-like"製程，製作深厚微泵腔室的結構。此一製程是一種以紫外光微影為基礎的 LIGA 技術。其中較為重要的是厚膜光阻及微電鍍技術。製作出金屬腔體及模仁。接著更可以利用熱壓系統，熱壓此平面型的腔體結構。我們所做出最厚的金屬腔體，厚度達 300 微米，並且其微小擴散╱噴射型導流道的壁面相當垂直。導流道出入口幾何形狀控制相當精確。 最後利用黏著的方式，將薄膜致動器及厚深腔體結合起來，製作出一熱致動式無閥微泵原型品。

In this paper, a micro pump is providing by the thermal membrane actuator and diffuser/nozzle elements are used as flow rectifying. The structure of the membrane actuator is like a sandwich; the top and bottom layers are the bimorph structure and the middle one is the micro heater. The bimroph structure is including SiNx and aluminum layers. Micro heater here is used for local temperature regulation. According to the bimorph effect, the membrane will oscillate by varying temperature. The numerical finite element program ANSYS 5.3 is used to simulate the behavior of the membrane actuators. The size of the fabricated membrane actuator is 780 μｍ in square. The vibration stroke is 25μｍ when input power is 1 W. Referring to the previous design, the diffuser/nozzle elements including rounded inlet and reentrant outlet. By means of this design on shapes of the flow channels, a larger volume flow can de predicted to reach in a pumping cycle. Here, we interest in fabricating thick chamber structure (i.e. 100μｍ) and a " LIGA-like " process is used to fabricate metallic chamber. Such method is an UV lithography-based LIGA process. This method combine thick film photoresist and micro electroplating to form a metallic chamber structure or act as a mode insert. Then a hot embossing system is applied for hot embossing of planar chamber structures in thermoplastic materials. The most thick metallic chamber structures is 300μｍ in thickness and the side wall of the diffuser/nozzle elements is quite sharp. Finally, the membrane actuator and chamber structure are glued together to form the prototype of micro pump.