Ultrasensitive Surface Acoustic Wave Gas Sensor for Trace VOCs Detection Based on Sensing Mechanism of Gas-Liquid Phase Transition

In this study, a novel un-coated Rayleigh surface acoustic wave (SAW) gas sensor was developed based on sensing mechanism of gas-liquid phase transition for trace volatile organic compounds (VOCs) detection. The sensor utilized single-port surface acoustic wave resonator (SAWR) with resonance frequency of 433 MHz as the sensing component, which was fabricated on ST-cut quartz substrate with zero temperature coefficient to avoid temperature interference. The model of gas-liquid phase transition was established to illustrate the relationship among the sensor sensitivity, temperature and gas concentration. The selectivity of the polymer-uncoated SAWR gas sensor was realized by integrating a capillary separation column for detection of mixed trace VOCs. The frequency shift was monitored and transmitted to a smartphone. The experimental results showed that the miniaturized gas analyzer has good selectivity, fast response and ultrahigh sensitivity with a detection limit at ppb level.