Virtual Quartz Crystal Microbalance: Bioinspired Resonant Frequency Tracking

Abstract

The reference acoustic properties of the quartz crystal used as a resonator are ensured by its high-quality factor (Q-factor). The microbalance of the quartz crystal (QCM) exploits the bulk acoustic properties of the quartz crystal. Turning a network analyzer or impedance analyzer into a QCM with a decent measurement rate is a challenge. The use of a virtual instrument to implement an impedance analyzer (VIA) provides greater flexibility to the virtual QCM. In this paper, VIA’s flexibility is exploited for the experimental evaluation of conventional scanning procedures and the influence of associated parameters, in order to identify elements that can lead to a limitation of the performance of a virtual QCM. The results of the experimental investigation justify the use of an innovative and optimized bioinspired scanning procedure to effectively track the serial resonance frequency of the QCM sensor. Variable-resolution spatial sampling of the human retina and the ability of the eye to refocus on the area of interest is the source of bioinspiration for achieving an adaptive virtual QCM. The design methodology and physics are described in detail, and the experimental investigations demonstrate the effectiveness of the proposed bioinspired scanning procedure.