聲射流(Acoustic Streaming)是一種經由高頻率振盪下在流體與邊界交互作用產生的穩態流動現象。本文使用微型微粒循跡測速儀(Micro Particle Tracking Velocimetry, Micro-PTV)探討微流道中藉由不對稱三角形微結構在高頻下誘發之聲射流形態。本研究使用微铣削(Micro-milling)的方式製作實驗用之壓克力模具，並使用PDMS藥劑進行二次翻模，得到最終實驗使用之微流體裝置。實驗中採用三種不同頂角(α=20°, 35°, 70°)及三種不同傾角(β=30°, 45°, 60°)的不對稱三角形結構誘發聲射流渦旋，探討不對稱三角形頂角、傾角誘發之聲射流變化情形。並利用不同驅動電壓於單一個不對稱三角形結構誘發聲射流，以觀察驅動電壓對聲射流渦旋之影響。由μ-PTV之分析結果可得知一對相互反轉之聲射流渦旋會產生於頂角兩端，且聲射流於不對稱三角形結構尖端附近速度較快。不對稱三角形結構之頂角與聲射流最大絕對速度呈現逆相關之關係，即不對稱三角形頂角越大，產生的聲射流最大絕對速度越小。而不對稱三角形結構之傾角與聲射流渦旋之對稱性則成正相關之趨勢，即當傾角較大，聲射流渦旋則越趨近於對稱的形式。由頂角35°，傾角30°之不對稱三角形結構下改變電壓之實驗結果得知電壓與聲射流最大絕對速度成正相關關係，且電壓越大，產生的聲射流渦旋範圍越大。由不同高度的流場形態比較結果亦可推測聲射流之流場結構有三維之變化。

Acoustic streaming is a steady flow phenomenon generated from the interaction between the fluid and oscillating boundary. In this study, acoustic streaming flow patterns induced by high frequency oscillation of asymmetric triangular structures are investigated by micro-particle tracking velocimetry (μ-PTV) technique. The PMMA mold of the device in this study is made by micro-milling, and the microfluidic device is made of poly(dimethylsiloxane) (PDMS) through soft lithography. In order to compare the acoustic streaming flow patterns induced by the different asymmetric triangular structures, 3 different tip angles (α=20°, 35°, 70°) and 3 different inclined angles(β=30°, 45°, 60°) are investigated with a fixed frequency of 12 kHz and two voltages 20 V, 25 V. The results of μ-PTV analysis show that a pair of counter-rotating acoustic streaming vortices is generated near the tip of the triangular structure, and the acoustic streaming velocity is higher close to the tip. The tip angle of the asymmetric triangular structure and the maximum absolute flow velocity have an inverse correlation, whereas the larger inclined angle makes the acoustic streaming vortex pair more symmetric. The results of the different input voltage from the asymmetric triangular structure of α=35° and β=30° show that the when the input voltage is larger, the maximum absolute velocity is higher and the induced acoustic streaming vortex is also larger. A comparison of the acoustic streaming flow patterns at different channel heights also suggests that the acoustic streaming flow structure is three-dimensional.

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