Selective Detection of CO2 and H2O Dual Analytes Through Decoupling Surface Density and Shear Modulus Based on Single SAW Resonator

The detection of carbon dioxide (CO2) and water molecules (H2O) is of great interest because they play an important role in the fields of industry, agriculture, climate and medical treatment. However, both experimental studies and engineering applications indicate that most CO2sensors suffer from selectivity problems in high humidity. Herein, we detect concentrations of CO2and H2O simultaneously through decoupling surface density and shear modulus under negligible effect of electric conductivity based on a surface acoustic wave (SAW) resonator at 221 MHz. The SAW-based sensor demonstrates a small measurement error of ~ 65 ppm in CO2and ~ 1.2% RH in H2O. The sensor also shows excellent short-term stability of 0.8 kHz. Besides, this general method that using a single SAW resonator to detect two analytes selectively will be useful for other resonator-based sensors.