Providing traceability for Quartz Crystal Microbalances (QCM)

Figure 1: QCM facility.

Quartz crystal microbalances (QCMs) are used in a wide range of applications and NPL is working towards a means of making such measurements traceable to national standards.

QCMs are used to measure very small changes in mass by monitoring the resonance of a quartz crystal.  As mass is added to the crystal, in the form of a surface layer, the resonance of the crystal changes and the added mass can be calculated. However such calculations are based purely on theory and NPL is investigating methods to validate QCM theory and allow then to be traceably calibrated…

Additionally, NPL’s Engineering Measurement team is developing a traceable QCM facility that will be capable of sensing small mass changes in gels (Figure 1). The ability of a QCM to measure the mass of a thin rigid film has been well characterised, however the behaviour of thicker viscoelastic gels are not well understood.

Monitoring mass changes in gel like materials is of particular interest to biomaterials research. Scientists in NPL’s Biomaterials team need to monitor the rate of protein movement through gel like substances. Development of a validated QCM facility that can measure mass changes in gels would allow the measurement of this protein movement.