Acoustoelectric coupling

It is simple to derive the changes in velocity and attenuation arising from SAW/thin-film acoustoelectric coupling using the formalism outlined in Section... 

A number of interactions can affect plate-mode propagation characteristics, particularly in a liquid environment. In the following sections, models of several of the important modes of interaction will be outlined and compared to experimental results. These include (1) mass accumulation on the device surface, (2) viscous entrainment of the contacting liquid medium by the oscillating device surface, and (3) acoustoelectric coupling between evanescent plate mode electric fields and the liquid. 

Like the viscous entrainment of liquid by the surface, the electrical entrainment of ions decays exponentially with distance from the solid/liquid interface. Since the electric field has a decay length of A/2ir, however, ion coupling extends several micrometers into the liquid. Ion, dipole, and induced-dipole motion resulting from this acoustoelectric coupling lead to a perturbation in plate mode velocity and attenuation. 

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