MULTIPLE CHEMICAL INFORMATION FROM THE THICKNESS SHEAR MODE ACOUSTIC-WAVE SENSOR IN THE LIQUID-PHASE

The effects of viscosity, density, and dielectric constant of a liquid on the response of a thickness shear mode (TSM) bulk acoustic wave sensor are examined with respect to frequency response and the electrical properties of the equivalent circuit. The different behaviors of the characteristic frequencies upon perturbation of the equivalent circuit parameters are studied and the complementary nature of the motional inductance and motional capacitance discussed. The physical significance of the equivalent circuit parameters is described theoretically, and the relationship between the motional inductance and resistance of the TSM sensor and the density-viscosity product of the bulk liquid as well as that between the static capacitance of the TSM sensor and the dielectric constant of the liquid is demonstrated experimentally with a network analyzer. The composite responses of the resonant frequencies upon liquid loading can be interpreted in terms of the kinetic energy transfer, acoustic energy dissipation, and formation of interfacial structures in the sensing system. The properties of the surface adjacent liquid layer at the solid-liquid interface are estimated from the responses of the respective parameters.