抄録
A chemical sensing system that uses a new type of sensor film and digital signal processing of their dynamic responses is described. This system consists of quartz crystal microbalances coated with plasma polymer films. These films are useful due to their high densities of radical sites and unsaturated bonds, which interact with gas molecules. Impedance analysis shows that a plasma-polymer-film-coated sensor is a durable and stable microbalance. When this sensor array is exposed to a gas, the adsorption and desorption of the target gas causes dynamic piezoelectric responses. Because the sensor films have an affinity for several types of gas, signal processing is needed to discern unique gas information. To analyze its response, we represent it by a linear filter, which is often used for estimating the parameters of dynamic systems. This filter has coefficients that represent the sensor's transfer function and these provide pattern vectors that characterize the target gas for classification. This filter shows that recognizing and quantifying the components of a gas mixture are possible using our sensing system. It also shows that the system can identify the sensor's transfer function even when the gas concentration changes, by using two sensors with different dynamic properties. These results show that this chemical sensing system is useful in a wide range of applications, such as chemical analysis systems and fire alarm systems.
