What are the benefits of taking measurements at several frequencies simultaneously?
Simultaneous measurement at multiple overtones is required to model viscoelastic properties and to calculate the correct thickness of films that do not obey the Sauerbrey relation. With the Q-Sense E4 system, 14 incoming parameters (seven frequencies and seven dissipation values) per sensor provide a well-determined model of the particular film properties. Moreover, the different overtones give information about the homogeneity of applied layers: as the detection range out from the sensor surface decreases with increasing overtone number, abnormal frequency behavior suggests vertical variations in film properties. The fact that the detection range from the sensor surface decreases with increasing frequency is also used by the modelling software to calculate an accurate thickness of films that do not fully couple to the oscillation of the sensor. For rather soft films, with high water content (e.g., films made of large proteins), you will not obtain accurate thickness information withou
