設計改良式表面聲波感測器應用於低濃度混合氣體量測

Improved Surface Acoustic Wave Sensor for Low-concentration Gas Mixture Detection

江明璋(Ming-Chang Chiang)

指導教授 ： 饒達仁

國立清華大學/工學院/動力機械工程學系/碩士(2013年)

https://doi.org/10.6843/NTHU.2013.00014

摘要

本文利用表面聲波 (Surface Acoustic Wave, SAW)原理發展出高靈敏度的電子鼻感測系統，利用128°YX-LiNbO3壓電材料與黃光微影製程技術完成感測晶片，當薄膜吸附造成重量變化導致表面聲波傳遞速度改變，藉此觀察後端頻率變化量判定吸附氣體種類與濃度。
本研究以量測低濃度混合氣體為目標，並提升感測靈敏度與精密度。整體系統方面，藉由改進原先感測腔體模組及奈米感測薄膜來達到實驗目的，其中感測腔體由1 L四頸瓶改良為200 μl微型流道儲存槽，而奈米感測薄膜由PNVP/中孔洞片狀碳材改良為PNVP/中孔洞空心碳球。另外經過多次同一晶片的量測數據顯示，使用PNVP薄膜量測氨氣最低濃度達250 ppb。對於甲烷量測最低可達9ppm。綜合單一氣體的反應資料庫，在不同溫濕度狀況下進行氨氣/甲烷混合氣體的量測實驗。利用此感測器量測混合氣體的結果與單一氣體資料庫間具有疊加效應存在，且氨氣訊號相較於甲烷訊號較易受到濕度的影響，隨著濕度的提高而下降。此外，藉由定量混合氣體實驗所建構的資料庫與疊加效應的應用，可即時的預測各種不同濃度的氨氣/甲烷混合氣體訊號大小。期望此氣體感測可以更為廣泛地被大眾應用於工安環境檢測與日常生活中。

關鍵字

表面聲波 ； 混合氣體 ； 氨氣 ； 甲烷 ； 氣體感測器 ； 濕度

並列摘要

The detection results for mixture gas (ammonia/methane) by polymer deposited on 128° YX-LiNbO3 surface acoustic wave (SAW) delay lines are studied in this work. The adsorption of mixture gas by sensitive coating material modulates the phase velocity of the acoustic wave due to the mass loading and acoustoelectric effect. Thus, the targeted mixture gas can be evaluated by recording the frequency shift of the SAW device.
In this research, we used the SAW sensor to detect chemical compounds such as ammonia, methane, and ammonia-methane mixture gases. To enhance the sensitivity and accuracy of the surface acoustic wave sensors, the sensing chamber and polymer films was improved. Miniature cover with fluidic channels (200 μl) has replaced 1L 4-neck bottle chamber as a sensing chamber of the system. PNVP with mesoporous carbon hollow nanosphere has replaced PNVP with platelet mesoporous carbon as a sensing film of the system. Very low concentration of ammonia (≈ 250 ppb) and methane (≈ 9 ppm) can be detected by our SAW devices. From the ammonia gas and methane gas database, we can find that the frequency shift of ammonia/methane mixtures equal to the sum of frequency shift of ammonia and methane. Besides, the signal loss of ammonia is much stronger than methane in high relative humidity conditions. By quantitative measurement results of ammonia/methane mixture gas, we can use synergistic effects of the gas mixture to predict the signal intensity of different concentrations. The SAW sensor can also be applied to other industrial and environmental detection, and hope the gas sensor can be widely used in the daily life.

並列關鍵字

Surface acoustic wave ； Mixture gases ； Ammonia ； Methane ； Gas sensor ； Humidity

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