Abstract
In this paper an analysis of the responses of surface acoustic wave (SAW) sensors coated with polymer films is described. Complex bulk and shear moduli are utilized to represent viscoelastic properties of the polymer. Compared with the experimental results, the calculated results strongly suggest that the real part of the shear modulus mostly influences the velocity shift and attenuation change in the sensor responses. In addition, using the real parts of the shear modulus, the polymer films can be classified into three types: glassy films, glassy-rubbery films and rubbery films. Simulations of gas sorption for polymer films are performed. For glassy films, the SAW sensor response increases with increasing film thickness, whereas for glassy-rubbery and rubbery films, the relationship between the sensor sensitivity and film thickness is more complicated. Therefore, an optimization of the properties and thickness of films and the operating frequency is required for designing SAW gas sensors with polymer coatings.