Response of polymer-coated Love-wave device: a method to characterize thin film in the radio frequency domain

In this paper, we present Love-wave devices and their characteristics. Love-wave sensors present a high sensitivity for gas detection. High selectivity is achieved with a sensitive coating chosen for its affinities toward a target compound, this coating is often a polymer. Acoustic wave devices are sensitive to all types of propagation perturbations which include mass loading and mechanical properties changes (e.g. viscoelasticity) of the coating. Experimental results allow to determine the contribution of viscoelastic properties of the sensitive coating to Love wave devices responses. Furthermore, it can be a mean to characterize thin film materials in radio frequency domain. Experiments were done with a polymer as sensitive layer: PEUT (polyetherurethane).The first study of PEUT properties at high frequency allows to estimate the dynamic shear modulus of this polymer and to confirm the glassy-like state of the material at high frequency. Further experiments using PDMS (polydimethylsiloxane) with different viscosity and stiffnesses on Love-wave devices are then presented and analyzed.