The electrochemical quartz‐microbalance in media of changing viscoelastic properties, and the design and characterization of a suitable driver electronics

In this work we develop a new description of the behaviour of the electrochemical quartz‐microbalance (EQMB). It takes into account the phase shift introduced by the driver and also the influence of changing visco‐elastic properties of the medium in contact with the quartz (i.e. film and/or liquid). Based on these concepts a new driver circuit has been designed. Its electronics is advanced relative to the classical drivers in two points: a) It allows a partial impedance analysis of the quartz, b) it introduces a controllable phase shift into the system driver+crystal. Thus, an evaluation and even correction of the obtained frequency‐results becomes possible. Experimental frequency data obtained in liquids with different visco‐elastic properties were corrected with the new approach and compared with theory. The capability of determining the resistive component of the quartz' impedance was also used to determine the limits of the rigid‐layer approximation for polypyrrole‐films.