浸入式表面聲波液體感測器之設計、製作及特性分析

Design, Fabrication and Characterization of Immersed-Type Surface Acoustic Wave Liquid Sensor

杜政樵(Cheng-Chiao Tu)

指導教授 ： 宋家驥

國立臺灣大學/工學院/工程科學及海洋工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.02494

摘要

拉幅波元件由於剪水平的方式傳遞與聲能量集中於表面，質點只會產生橫向位移而不會有縱向壓縮波，可避免待測液體負載於表面時而導致振幅大量衰減，所以適合做為高靈敏度的液體感測器。本文旨在設計與製作浸入式拉幅波液體感測器。藉由微機電製程，製作的拉幅波液體感測器包含低溫度頻率係數的ST-cut石英基板、鋁叉指換能器、以及物性化性穩定的二氧化矽波導層。浸入式的感測器結構可以有效地避免環境的干擾，液體負載與感測器溫度相同和容易控制，且能即時監控液體負載的變化。
量測的部分，由震盪電路、液體感測器及頻譜分析儀組成的溫控系統被利用來量測不同溫度及不同濃度下，甲醇與氯化鈉水溶液濃度對共振頻率的影響。結果顯示，濃度變化與頻率的偏移具有相當良好線性關係。因此所製作的浸入式拉幅波液體感測器適用於直接甲醇燃料電池的甲醇濃度之即時監測，及海水淡化系統中的鹽度感測。未來，浸入式拉幅波液體感測器預期將適合整合在更多領域，如工業檢測與生技感測系統等。

關鍵字

表面聲波 ； 拉幅波 ； 波導層 ； 浸入式液體感測器 ； 甲醇 ； 氯化鈉

並列摘要

The Love wave device has been proven to be a sensitive liquid sensor due to its shear-horizontal type propagation and the elastic wave energy concentrates near the
surface. Love wave with horizontal displacement can avoid the surface loading induced substantial attenuation when propagating on the substrate surface. This paper
presents the design and manufacturing of Love wave liquid sensors. By using the Micro-Electro-Mechanical Systems (MEMS), the fabricated Love wave liquid sensors consist of the substrate of ST-cut quartz, the Al interdigital transducers, and the SiO2 guiding layer. Choosing ST-cut quartz as substrate is because of its low temperature
coefficient of frequency. The immersion experiment diminishes the environmental disturbances and makes the temperatures control of the liquid loading easier.

A spectrum analyzer, liquid sensor and an oscillator circuit were employed for the measurement of methanol and Sodium Chloride (NaCl) solutions with different
weight concentrations at different temperatures. A linear relation is observed between the frequency shift and the weight concentration which shows that the fabricated Love
wave liquid sensors are applicable for NaCl as well as for methanol concentration in the direct methanol fuel cell (DMFC).

並列關鍵字

surface acoustic wave(SAW) ； Love wave ； guiding layer ； immersed-type liquid sensor ； methanol ； NaCl

參考文獻

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