Environmental characteristics of surface acoustic wave devices for sensing organophosphorus vapor

Obviously, the complicated application environment such as the varied temperature, humidity and interfering gases would produce great influences towards sensing process of gas sensors. To address the environmental characteristics in gas sensing process, surface acoustic wave (SAW) sensing devices built by a fluoroalcoholpolysiloxane (SXFA) deposited along the SAW propagation path of delay-line-patterned device were characterized in specific environments. Larger sensitivity, excellent linearity, and lower limit of detection (LOD) of 0.12 mg/m3 were achieved from the proposed sensing device towards organophosphorus dimethyl methyl phosphonate (DMMP). By varying the testing temperature (5 degrees C-45 degrees C) and humidity (30-80 %RH), the corresponding effect on sensor response was examined. Apparent crossed temperature and humidity sensitivity were observed in gas sensing process, and corresponding causes were demonstrated in details. Also, the cross interference test from the interference gases and smoke in the background environment demonstrated excellent anti-interference ability owned in the proposed sensing devices. Additionally, the long-term stability test in 18 months was conducted to examine the fatigue life of the sensing chip at temperature of 25 degrees C and humidity of 35 %RH. The concluded detection error was less than 8%. Moreover, the related mechanisms were also discussed.