The Bleustein–Gulyaev wave for liquid sensing applications

Crystallographic orientations in piezoelectric materials which support the Bleustein–Gulyaev (BG) wave are shown to offer sensor designers candidate sensor platforms for liquid phase sensing applications. This wave, which occurs in the family of Z-axis cylinder cuts in piezoelectric materials belonging to the orthorhombic mm2 crystal group, has displacements in the surface plane perpendicular to the propagation direction and an electric field in the sagittal plane. This wave offers the advantage of not radiating a compressional wave when loaded with a liquid. Theoretical calculations for the velocity and the associated mechanical and electric fields have been performed for potassium niobate (KNbO3), a candidate mm2 group crystal, which show that this material offers many promising orientations for liquid phase acoustic wave sensors.