Quartz
Crystal Microbalance (QCM) technique uses
the piezoelectric effect to develop very high
accelerations on the surface of a quartz
resonator vibrating in a shear mode. Thus, a
mega-gravity inertial field is created on the
surface of a quartz resonator. The recently
formulated and demonstrated
Acceleration
Dependent Mass Sensitivity Principle
explains the very high mass sensitivity of the
QCM. It also explains the origins of
frequency dependence on a liquid viscosity and
helps the interpretation of the experimental
results.
QCM technique was introduced in 1959 by
Sauerbrey. Since then it became a a largely used
technique for mass measurements of the films
adherently deposited on the surface of a quartz
resonator. The resonant frequency of the quartz
resonator changes when the the mass of the
adherently deposited film changes. An increase
in the film mass will induce a decrease of the
resonant frequency. The mass change of a solid
film can be accurately calculated using the
equation derived from the
Energy Transfer
Model (ETM). This equation was
experimentaly verified up to a mass load of 37%.
The Sauerbrey's equation is accurate only for
small mass loads under 2%.
QCM-soft
calculates the mass of the deposited film and
its thickness using the equation derived from
the ETM.
The series resistance of a quartz resonator will
increase when vibrating energy is dissipated in
the contacting film or in the surrounding
medium. Phase transitions or changes of the
viscoelastic properties of the deposited film
can be revealed by changes in the series
resistance of the quartz resonator. The series
resistance can also be used to make corrections
in the mass calculations when viscoelastic films
(proteins, polymers etc.) are deposited on the
quartz resonator surface. This correction also
depends on the crystal geometry and electrode
design.
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