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    Quartz crystal microbalance setup for frequency and Q‐factor measurements in gaseous and liquid environments

    Year: 1995

    Journal: Review of Scientific Instruments 66, 3924, doi:10.1063/1.1145396, 20110413

    Authors: Rodahl M. 1, Höök F.  2, Krozer A. 1, Brzezinski P. 3,  Kasemo B  4

    Last authors: Bengt Kasemo

    Organizations: 1 Department of Applied Physics, Chalmers University of Technology & Göteborg University, S‐412 96 Göteborg, Sweden 2 Department of Applied Physics and Department of Biochemistry and Biophysics, Lundberg Laboratory, Chalmers University of Technology & Göteborg University, S‐413 90 Göteborg, Sweden 3 Department of Biochemistry and Biophysics, Lundberg Laboratory, Chalmers University of Technology & Göteborg University, S‐413 90 Göteborg, Sweden 4 Department of Applied Physics, Chalmers University of Technology and Göteberg University, S‐412 96 Göteborg, Sweden map

    Country: Sweden

    An experimental setup has been constructed for simultaneous measurements of the frequency, the absolute Q factor, and the amplitude of oscillation of a quartz crystal microbalance (QCM). The technical solution allows operation in vacuum, air, or liquid. The crystal is driven at its resonant frequency by an oscillator that can be intermittently disconnected causing the crystal oscillation amplitude to decay exponentially. From the recorded decay curve the absolute Q factor (calculated from the decay time constant), the frequency of the freely oscillating crystal, and the amplitude of oscillation are obtained. All measurements are fully automated. One electrode of the QCM in our setup was connected to true ground which makes possible simultaneous electrochemistry. The performance is illustrated by experiments in fluids of varying viscosity (gas and liquid) and by protein adsorption in situ. We found, in addition to the above results, that the amplitude of oscillation is not always directly proportional to the Q factor, as the commonly used theory states. This puts limitations on the customary use of the amplitude of oscillation as a measure of the a factor.