表面聲波氣體感測器應用於低濃度氨氣偵測與集群分析辨識

Polymer Coated Surface Acoustic Wave Sensor for Low Concentration Ammonia Detection and Clustering Analysis

陳玫菁(Mei-Ching Chen)

指導教授 ： 饒達仁

國立清華大學/工學院/奈米工程與微系統研究所/碩士(2010年)

https://doi.org/10.6843/NTHU.2010.00310

摘要

摘要
　　本文利用表面聲波 (Surface Acoustic Wave, SAW)原理發展出高靈敏度的2×2陣列化電子鼻感測系統，我們選用高機電偶合系數Ｋ2值的128°YX-LiNbO3壓電材料作為表面聲波元件之基材，並且利用黃光微影製程技術與金屬沉積在其上製作指叉式電極，最後以旋佈的方式在延遲線感測區塗佈上高選擇性的高分子薄膜。此元件設計操作頻率為117.4 MHz，經由薄膜吸附感測氣體造成重量變化，導致表面聲波傳遞速度改變，由此觀察頻率飄移的下降量。
　　本文選用十種高分子薄膜 ( PNVP、P4VP、PVAc、PS、PSMA、PEG、PSu、PCL、PMMA、PVB )，偵測甲醇、乙醇、丙酮、氨及三甲基胺等氣體，建立一個簡易的氣體辨識資料庫。其中對poly-N-vinylpyrrolidone (PNVP)感測薄膜量測32.9 ppm、57.3 ppm與100 ppm氨氣氣體，觀察頻率飄移的下降量，約有78.8 Hz、151.4 Hz與450 Hz，系統穩定度可達3 Hz/sec的頻率變化量。關於辨識方法的實驗設計，模擬一未知氣體（異丙醇氣體）進入感測系統，經過2-way階層式群集分析法(Hierarchical Clustering Analysis)及樹狀圖分析後，可正確地將異丙醇氣體與已知醇類歸為同一群集，並與胺類氣體分開為兩大群集，丙酮則被歸類為較靠近醇類之群集。

關鍵字

表面聲波 ； 高分子薄膜 ； 電子鼻 ； 頻率飄移 ； 氨氣

並列摘要

Abstract
　　The detection results for organic vapors and ammonia gas by different polymer deposited on 128° YX-LiNbO3 surface acoustic wave (SAW) delay lines are studied in this work. The gas sensor array is based on 2×2 non-continuously working oscillators equipped with differently polymer-coated surface acoustic wave sensors. The SAW detection system which is employed to detect various organic molecules in a static system was prepared using 117.4 MHz two-port SAW resonators and a computer for signal acquisition and data process. This gas sensor array system consists of SAW sensors, polymers with different polarity and function groups, and signal readout electronics. The appropriate coating materials on to the SAW crystal would be used for gas detection, e.g. poly(N-vinylpyrrolidone), poly(4-vinylphenol), poly(vinyl acetate), poly-ethylene-glycol, poly-styrene-co-maleic anhydride, polystyrene and poly-sulfone. The frequency shift of SAW was measured to detect the presence of ammonia and organic vapors. Therefore a simple database would be created by different gas detection. Detecting at an ammonia concentration of 32.9 ppm, the frequency shift was 78.9Hz with a response time of less than 90 s. The good result of tree-view from the two-way hierarchical clustering analysis is studied in this work after comparing the correlation between the 6 coating materials and 6 organic vapors. Furthermore, the SAW detection system can distinguish unknown gas or mixed gas by the database of pattern recognition in the future.

並列關鍵字

Surface Acoustic Wave ； polymer ； E-NOSE ； frequency shift ； ammonia

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