Propagation of acoustic waves at the interface between a piezoelectric crystal and an isotropic viscoelastic conductive medium (SAW sensors)

Liquid-phase acoustic wave biosensors consist of a piezoelectric substrate, an isotropic film used for selectivity or as a molecular recognition element, and a liquid medium providing the environment for the species to be detected. At any point in time (during the chemistry being conducted at the surface) both film and liquid may be modeled as isotropic viscoelastic conductive media. A general theory describing the effects of isotropic viscoelastic conductive media on the propagation characteristics of acoustic waves excited by interdigital transducers (IDTs) is presented for arbitrary piezoelectric crystal orientations. Results and discussion are given relative to chemical sensors and biosensor applications.<>