Dynamic response of PPF-coated QCR sensor: Model based on sorption/desorption behaviours of gas molecules and adsorbed water

This paper proposes a mathematical model of a mass-sensitive chemical sensor with a PPF-coated quartz crystal resonator (QCR) to enable its use for the signal processing of gas sensing systems that are operated under ambient conditions. To approximate the pulse-like responses of the PPF-coated QCR sensor to the sample gas and adsorbed water, a mathematical model based on the diffusion equation (under the assumption of one-dimensional Fickian diffusion of the sample gas molecules to the sensor film) is extended to a time variation model (based on the assumption that the sorption/desorption phenomena occur in time order in the vicinity of the PPF surface). Computational experiments show the feasibility of the proposed mathematical model for estimating the response of the PPF-coated QCR sensor under ambient conditions.