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.