CHEMICAL SENSING BY ANALYZING DYNAMICS OF PLASMA POLYMER FILM-COATED SENSORS

A chemical sensing system that incorporates unique sensor films and uses pattern recognition of their dynamic responses is presented. This system consists of a sensor array of quartz-crystal microbalances coated with plasma polymer films. The films, synthesized by radio-frequency sputtering, are useful because of their high density of radical sites and unsaturated bonds. When this sensor array is exposed to a gas, the adsorption and desorption of the target gas causes a dynamic frequency response in each piezoelectric sensor. The sensor response is analysed by an autoregressive model typically used to estimate the parameters of dynamic systems. This model's coefficients reflect the sensor dynamics, providing pattern vectors that characterize the target gas. Based on this model, classification maps for single gases can be created with these pattern vectors. These maps show that the dynamic sensor response provides useful information for gas classification. This model also confirms that our sensing system can identify and quantify the components of a gas mixture.