Investigation of the reliability of piezoelectric chemical sensors

The aim of the research was to study the functional change of sensitivity, selectivity and overall stability of piezoelectric chemical sensors. A test device was built and experiments have been carried out to estimate the degradation of the piezoelectric sensor performance. Sensing materials were inspected by a scanning electron microscope (SEM) to investigate the surface structures. Strong correlation was found between the reliability and the quality of the sensing material surface. The surface formation depended upon the physical and chemical properties of the sensing materials. Both the electrostatic and structural features influenced the interactions between the sensor surface and the analytes. Interactions during the adsorption and desorption of volatile compounds could not only be estimated by the van der Waals interactions. The contact area of interactions, where the secondary chemical forces play a significant role, was determined by the surface structure and the molecular structure of the sensing material. Polarity and different surface formation were found to be the most important factors to improve the discrimination capability of piezoelectric chemical sensors. The same investigations were repeated after 3 months. The most remarkable comparison was the appearance of the SEM images. A relationship was also recognized between the elapsed time and the degradation of the selectivity of the detectors. The method developed can be used to estimate the applicability of a piezoelectric chemical sensor. (C) 2003 Elsevier Science B.V. All rights reserved.