When the QCM sensor top surface is immersed in fluids, unlike in vacuum, the oscillation of the quartz is damped. This results in changes in frequency and more importantly the damping parameter Γ. Furthermore, the frequency and damping shift depend on the fluid’s properties. The figure shows an example of the influence of different fluids. When immersed in different pure Newtonian fluids (e.g. water and water-glycerol mixture in the figure), the fluid with higher viscosity and higher density will cause a decrease in frequency and an equal amplitude increase in damping. This is defined by Kanazawa:
ΔfKanazawa = -ΔΓKanazawa = -Cf √(ηl ϱl )
Cf is a constant relating to quartz shear modulus, quartz density and resonance frequency. ηl is the dynamic viscosity of the fluid and ϱl is the density of the fluid.