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

• Main Authors: Chen, Mei-Ching, 陳玫菁
• Other Authors: Yao, Da-Jeng
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/92970229566140248379

碩士 === 國立清華大學 === 奈米工程與微系統研究所 === 98 === 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.