THEORETICAL AND EXPERIMENTAL-STUDY OF MASS SENSITIVITY OF PSAW-APMS ON ZX-LINBO3

Acoustic plate mode (APM) devices have recently been used as sensing e lements, both for the physical measurement of fluid properties and in biosensor applications. One of the primary interaction mechanisms in t hese devices is mass loading caused by the added mass bound to the lay ered crystal surface, However, the material properties of these thin c omposite layers are not well characterized or known as is required in order to accurately predict the sensor response. In the present work, perturbation theory is used to derive expressions for the sensitivity of the APM sensors to mass loading and viscoelastic stiffening, Mass s ensitivity experiment was conducted on ZX-LiNbO3 in a liquid environme nt to accurately reflect the sensitivity of an actual biosensor and th e results are compared to theory. The measured data show a f(2) depend ence for the mass sensitivity for APMs on ZX-LiNbO3 in the measured fr equency range, which indicates a SAW-like behavior. This behavior is d ue to the fact that the acoustic plate modes on ZX-LiNbO3 are pseudo-S AW (PSAW) derived, and the acoustic energy is confined to the sensing surface, As a result, the APMs on ZX-LiNbO3 are referred to as PSAW-AP Ms. Discussions are given in terms of the added mass which occurs in t ypical biosensor applications.