A High-Frequency, High-Q Lamb Wave Resonator for Sensitive Detection of Viscosity–Density Product in Liquids

This paper presents a high-frequency laterally-excited solidly mounted resonator (XSMR) based on an aluminum nitride (AlN) thin film for liquid viscosity sensing, where the high-frequency design significantly enhances the detection sensitivity. Finite element simulation confirms that the structure can efficiently excite the antisymmetric A1 mode, and a modified Butterworth–Van Dyke (mBVD) equivalent circuit model is employed to analyze the correlation between the resonator’s frequency response and liquid viscosity. Experimentally, the device successfully excites the A1 mode resonance at 5.97 GHz, with both the quality factor (Q) and the Bode Q reaching 721. In liquid sensing experiments, tests conducted on glycerol-water mixtures with varying concentrations demonstrate a sensor sensitivity of 2.45 MHz/kg·m-2·s-0.5to the viscosity-density product. This result validates the enhanced response capability of the high-frequency resonator to changes in liquid physical parameters. This research demonstrates the potential of high-frequency Lamb wave resonators for high-sensitivity microfluidic sensing and real-time biochemical detection.