A passive wireless surface acoustic wave (SAW) sensor system for detecting warfare agent based on fluoroalcoholpolysiloxane film

Long-term monitoring of warfare agengts in the environment is a challenge for chemical gas sensors. To address this issue, we developed a 433 MHz passive wireless surface acoustic wave (WSAW) gas sensor for dimethyl methylphosphonate (DMMP) detection. The prepared WSAW gas sensor was a YX lithium niobate (LiNbO 3 ) substrate with metallic interdigital transducers (IDTs) and etched on it, and an antenna was placed near the IDT, DMMP-sensitive viscoelastic polymer fluoroalcoholpolysiloxane (SXFA) film was prepared on LiNbO 3 substrate, and coupling of modes modeling was used to optimize the design parameters. The sensor can function normally in an environment with a temperature of -30 °C–100 °C and humidity of less than 60% RH. When the wireless transmission distance was within the range of 0–90 cm, the sensor noise increases with the distance, and the stability was less than 32°/h. In the process of optimizing the film thickness of SXFA, a certain relationship was observed between the sensor sensitivity and the film thickness. When the film thickness of SXFA reached 450 nm, the optimal value was reached. At the distance of 20 cm between the transmitting and receiving antenna, DMMP was detected under different concentrations with the developed WSAW gas sensor. The lower detection limit of DMMP was 0.48 mg/m 3 , the sensitivity of the sensor was 4.63°/(mg/m 3 ), and the repeatability of the sensor was also confirmed.