Fluid property investigation by impedance characterization of quartz crystal resonators

Abstract

In the first of this two-part communication, we present a methodology for the application of thickness shear mode (TSM) quartz crystal resonators (QCR) in fluid property investigation. To this end, we outline a protocol for the preparation of crystal surfaces for fluid contact and establish a methodology for the pre-screening of quartz crystals for application in fluid property investigation. We also present a data fitting algorithm which enables the conversion of raw impedance data into equivalent circuit parameters. Subsequently, we report on our study of a series of Newtonian fluids (2-propanol/water solutions) by frequency response analysis of the fluid-contacted TSM QCR. The results are analyzed in comparison to theoretical predictions presented in an earlier publication. The results show good agreement between the theory and experimentally derived equivalent circuit parameters. The influence of fluid elasticity on the impedance response of liquid-contacted thickness-shear mode (TSM) quartz crystal resonators (QCR) is investigated in the second part. Model predictions are compared to experimental results on a series of a TSM QCR contacted with poly(dimethylsiloxane) fractions. The findings show that with appropriate instrumentation and models to interpret results, TSM QCR can be rapid and effective tools in viscoelastic fluid property investigation.