基於石英晶體微量天平低成本黏度密度感測器之參數研究

Abstract

液體的黏度和密度在工業、生醫和化學領域都扮演很重要的角色。舉例來說，機油的黏度會影響引擎的性能；而血液的黏度則和心血管疾病、糖尿病、腎臟病等健康問題有關。密度方面，像在化學蝕刻製程中，液體的密度也會影響反應速率，是非常關鍵的參數。 石英晶體振盪器具有壓電特性，可以在高穩定、高頻率的剪切模態下運作，因此常被用來當作檢測液體黏度與密度的元件。根據日本工業標準（JIS），黏度計主要分為旋轉式、落球式和振動式三類，而石英晶體振盪器屬於振動式。跟其他類型相比，振動式黏度計靈敏度高、樣量少，成本也較低，特別適合應用在生醫領域。 不過在振動式黏度計中，石英晶體微量天平（QCM）的靈敏度通常會比表面聲波（SAW）感測器略低。因此，我們在本研究中參考文獻的做法，透過優化流動池設計，來提升 QCM 對液體黏度與密度的感測能力。我們選用了甘油這種常見的小分子液體作為測試對象，並結合有限元素模擬和 3D 列印技術，開發出一款具備高穩定性、高靈敏度和高精確度的液體黏度-密度感測器。最終實驗結果，基於石英晶體微量天平低成本黏度密度感測器對甘油靈敏度(Sensitivity)可達 593.6 [Hz/(mPa·s·g/cm³)]、精確度(Resolution)為 2.24[μPa·s·g/cm³]。

Liquid viscosity and density are critical parameters in industrial, biomedical, and chemical applications. For example, engine oil viscosity affects performance and protection, while blood viscosity is linked to cardiovascular and metabolic diseases. In chemical processes, liquid density influences properties such as etching rates. Quartz crystal oscillators, due to their piezoelectric properties and high-frequency shear mode operation, are well-suited for viscosity and density sensing. According to JIS classification, quartz crystal-based sensors are vibrational viscometers, offering higher sensitivity, lower sample consumption, and lower cost compared to rotational and falling-ball types, particularly benefiting biomedical use. This study enhances the sensitivity of quartz crystal microbalance (QCM) sensors—typically less sensitive than surface acoustic wave (SAW) sensors—by optimizing the flow cell design from paper. Using glycerol as a test liquid, finite element simulations and 3D printing are employed to develop a high-sensitivity, high-accuracy viscosity-density sensor. As a result, the low-cost viscosity-density sensor based on a quartz crystal microbalance (QCM) achieves a sensitivity of 593.6 [Hz/(mPa·s·g/cm³)] and a resolution of 2.24 [μPa·s·g/cm³] in detecting the viscosity-density product of glycerol.