整合無閥門壓電幫浦之脈衝式微混合器設計

Abstract

本研究利用微機電製程技術，成功開發出一具有自我推動能力的微混合器，即為不須外加的驅動源便可推動流體進行混合。此微混合器係利用微機電技術製作，其流體動力來源以及驅使流體混合的機制，皆為一對壓電無閥門微幫浦。利用貼附於振動腔體上的壓電片，並配合漸張�漸縮管作為流體的驅動源，另外利用調變該對壓電片訊號的相位差，可使欲混合流體進入混合區段的時間不一致，藉以增加流體之間的接觸面積，達到更好的混合效率。 實驗中發現當驅動訊號為反相位時，有較好的混合效率，而操作頻率須在最佳工作頻率上對於流體增加接觸面積有更好的效益，且驅動電壓愈高對於流體間界面的突破效果愈好。本元件僅以一道光罩完成，且在相當短的距離內就可達到高的混合效能，對於元件整合而言，可大幅縮小元件的體積，提高了系統整合的可能性。

This study proposed a new-type self-pumping micromixer which has two valve-less PZT micropumps in parallel arrangement. The rapid mixing was obtained by unsteady mixing mechanism which was due to the periodic variation of the flow at both inlets. This mixing effect is also affected by the oscillating frequency and the phase difference between the two inlet streams. High-quality mixing can be obtained in very short distance so that the device could be reduced to a very small size. In this study, experiments on the mixing effects were carried out by using two different channel geometries and three phase differences, 0°(in-phase), 90°and 180°(anti-phase). A CCD with illumination by a double-pulsing Nd-YAG laser was used to capture the flow images for the mixing process. Mixing efficiency was thus obtained by evaluating the grey scales of the images. The current results showed that higher mixing quality was obtained when in anti-phase conditions than that in in-phase condition. The results also indicated that the two inlet-streams can not be kept at the same flow rate in phase difference of 90°. For the in-phase conditions, better mixing efficiency was obtained when the larger impinging energy of fluids was generated by higher excitation voltage. For the anti-phase conditions, the existence of crescent-shape interface and the stretch-and-fold phenomenon at the confluence had pronounced effect on the mixing. Better flow mixing can be obtained by using higher driving voltage.