Method for measuring the losses and loading of a quartz crystal microbalance

: Kankare J, Loilkas K, Salomaki M

Publisher: AMER CHEMICAL SOC

: 2006

Analytical Chemistry

ANALYTICAL CHEMISTRY

: ANAL CHEM

: 78

: 6

: 1875

: 1882

: 8

: 0003-2700

DOI: https://doi.org/10.1021/ac051908g

A novel, experimentally simple, and highly sensitive method for measuring the loading of a quartz crystal resonator was developed. The method is based on the use of double-sideband suppressed-carrier modulated high-frequency signal, which is swept through the resonance range of the resonator. Induced current in the resonator is passed through a capacitor, and the voltage over the capacitor is demodulated on an analog multiplier. The phase and amplitude information is carried to the frequency-doubled modulation signal and measured on a conventional low-frequency two-phase lock-in amplifier. A complex dimensionless loading parameter is obtained from the experimental data by nonlinear model fitting. The real and complex parts of this loading parameter have a simple relationship with other parameters commonly used for characterizing the resonator loading. The performance of the method was demonstrated by measuring a series of different glycerol-water mixtures ranging from 0 up to 100% glycerol. The results were close to the shear acoustic impedance of these mixtures measured and calculated from their viscosities and densities.