Effect of an imperfect interface in a quartz crystal microbalance for detecting the properties of an additional porous layer

Sauerbrey's equation may yield incorrect results when the upper layer is not rigidly attached onto the quartz crystal plate. Thus, we investigate the effect of an imperfect interface on the anti-plane vibration of a quartz crystal microbalance for detecting the characteristics of the upper transversely isotropic porous layer. Both the stiffness and inertial effect of the porous layer, as well as the influence of an inhomogeneous interface, are considered for an infinite or finite AT-cut (35°15′ cut deviating principal optic axis) quartz plate. The appearance of a weak interface is theoretically and numerically revealed to excite a new thickness twist wave in an infinite quartz crystal plate. Meanwhile, the non-uniform interface evidently changes the displacement and stress distributions, which is totally different from the homogeneous interface. These findings prove effective guidance for physical phenomenon explanations and experimental measurement in mass sensor devices.