以表面聲波感測器為作業環境偵測氨氣方法之探討

Work Environment Monitoring ammonia detection using SAW Sensor Devices

廖志倫(Liao Chin)

指導教授 ： 鍾相彬 ； 賴永昌

高雄醫學大學/健康科學院/職業安全衛生研究所/碩士(2005年)

摘要

表面聲波元件感測器的原理是聲波傳遞表面的變化，造成其輸出相位和介入損耗的改變，而這些變化可經由量測聲波諧震頻率特性來測得。由於表面聲波對於感測物質變化極為敏感，所以本次研究即是想探討表面聲波元件是否可以作為另一種環境監測方法之探討。氣體感測膜的選擇也是主要問題，因為polymer material 對於所要偵檢的氣體/液體要有吸附性，這次所要選擇偵測的氨氣，我們所選擇的polymer 是polyaniline(聚苯胺)，為本身具有導電性之共軛聚合物(conjugated polymer)，具有良好化學穩定性、及容易製備合成。
Surface Acoustic Wave Nano-gram Balance 的測量原理是化學物質通過晶片表面產生交互作用(interactioins)，交互作用是由於三種因素：mass loading；viscoelastic effects及permittivity effect。而氣相物質的量測原理是當感測氣體流過晶片表面時會因為mass loading而產生聲波諧震頻率特性和晶片上所塗布的polymer 產生作用。
由研究的成果可知聚苯胺感測塗層對於偵測氨氣具有極佳的靈敏度、回復性、再現性及選擇性。當操作溫度控制在30℃時，氨氣濃度與反應量的曲線呈現最佳的線性度與靈敏度，該靈敏度為0.0097 ppm/Hz，最低可偵測極限推測為1ppm的氨氣。

關鍵字

感測器 ； 胺氣 ； 表面聲波濾波器 ； 氨氣

並列摘要

Thin film coated SAW device has been proposed in the hazardous gas detection in this study. The absorption of the toxic gas passing through a SAW sensor can change the base resonance frequency due to the mass loading effect. By observing and measurement of the acoustic frequency variation on the SAW channel we can detect the presence of the environmental offensive gases. As a demonstration purpose, we selected the ammonia gas as our target media and used of the polyaniline (PANi) thin film as a coated-sensing polymer. The SAW semiconductor chips were designed and proto-type tested using IDTs electrodes on a LiNbO3 base with an assuming operating conditions of 25~30℃ at 1 atm. The conjugated polymers were also selected, based on their chemical stability and easy preparation, to be EB (polyaniline emeraldine base) and NMP(1-methyl-2-pyrrolidinone). These polymers were spraying-coated on the top of the SAW chip set with PANi EB to NMP at a ratio of 1:9. Standard ammonia gases concentrations were prepared by dilution method using dry nitrogen and have been used in the tests to verify the detection sensitivity.
Ammonia gases with varying concentration have been conducted in the tests using thin film of PANi polymer coated on SAW devices. Ammonia gas mixed with dry nitrogen started at 80ppm as an upper bound has been tried out continuously to lower concentrations by dilution method. As an initial result, the SAW device has a low detection response at about 30ppm.in an operating temperature at 30℃. We also found that the coating technique of the polymer and the homogeneity of mixing gases would strongly affect the detection outcomes.
We have demonstrated that the SAW devices can be used as toxic or offensive gas sensors based on mass-loading technique. The on-going research will be focused on the study of the stability, interferences and optimization of this extremely high sensitive probe in the work environment monitoring applications

並列關鍵字

ammonia ； Surface acoustic wave ； polyaniline

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