Evaluation of Dynamic Viscosity in the 10 MHz Range Using a General-Purpose Quartz Crystal Microbalance

Abstract

This study examined the validity of viscosity measurements in the frequency region of 10 MHz using a commercially available quartz crystal microbalance (QCM). Ethylene glycol aqueous solutions were used as model samples. From the changes in the resonant frequency and dissipation parameter before and after the introduction of the sample liquid, we determined dynamic viscosity through Johannsmann's equation and compared it with literature data for zero shear viscosity. As a result, the viscosity estimated by QCM was systematically higher. Based on the analysis of the electrical equivalent circuit of the resonator, we considered that such deviation is due to the energy loss inside the quartz resonator and the non-ideal nature of the interface in contact with the sample liquid. To avoid such non-idealities, we proposed a method of applying a calibration equation to the viscosity value obtained from the Johannsmann equation. This makes it possible to easily measure viscosity in the 10 MHz regions with an accuracy of ± 3 % error.