Development of cryptophane A-coated SAW methane gas sensor

Accurately measurement and monitor on methane gas (CH4) concentration is an urgent problem to be solved in the purpose of safety and process control in homes, industries and mines. This paper proposed a new surface acoustic wave (SAW) based methane gas sensor, which was coated by a supra-molecular cryptophane A (CrypA). A differential SAW oscillator with excellent frequency stability was performed, and the two-port SAW resonator with low insertion and high Q-value was designed as the feedback element of the oscillator. CrypA was deposited along the SAW propagation path of the sensing device by drop-coating. Fast response and excellent repeatability were observed in methane gas sensing experiment at room temperature (20°C), and the estimated detection limit and measured sensitivity in CH4 dynamic range of 0.2%~5% was evaluated as ~0.05% and ~204Hz/%, respectively.