Poled PVDF-TrFE coatings on quartz microbalance sensors: A new technique for study of proteins in solution

A quartz crystal microbalance (QCM) measures mass per unit area by determining the change in frequency of a quartz crystal resonator caused by the addition of a small mass. The nominal resonance frequency of the shear mode of the quartz sensor is 5 MHz. A frequency change of 0.1 Hz corresponds to an addition of about 2 ng/cm 2 of mass to the quartz surface. Sauerbrey was the first to recognize the potential usefulness of the QCM technology and demonstrate its extreme sensitivity to mass changes [1]. He developed the fundamental equation describing the QCM: equation Here Δƒ = change in frequency (Hz), ƒ 0 = fundamental frequency of resonator (MHz), ρ q = quartz density (2.648 g cm −3 ), μ q = shear modulus of AT-cut quartz (2.947 × 10 11 g cm −1 s −2 ), and Δm = mass change/unit area (µg/cm 2 ). The AT-cut is used because its resonant frequency is almost temperature-independent.