Fluid property investigation by impedance characterization of quartz crystal resonators - Part I: Methodology, crystal screening, and Newtonian fluids

In the first of this two-part communication, we present a methodology for t he application of thickness shear mode (TSM) quartz crystal resonators (QCR ) in fluid property investigation. To this end, we outline a protocol for t he preparation of crystal surfaces for fluid contact and establish a method ology for the pre-screening of quartz crystals for application in fluid pro perty investigation. We also present a data fitting algorithm which enables the conversion of raw impedance data into equivalent circuit parameters. S ubsequently, we report on our study of a series of Newtonian fluids (2-prop anol/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 betwe en the theory and experimentally derived equivalent circuit parameters. The influence of fluid elasticity on the impedance response of liquid-contacte d thickness-shear mode (TSM) quartz crystal resonators (QCR) is investigate d in the second part. Model predictions are compared to experimental result s on a series of a TSM QCR contacted with poly(dimethylsiloxane) fractions. The findings show that with appropriate instrumentation and models to inte rpret results, TSM QCR can be rapid and effective tools in viscoelastic flu id property investigation. (C) 1999 Elsevier Science S.A. All rights reserv ed.