Piezoelectric sensors
Quartz crystal microbalance (QCM) is a bulk acoustic
wave (BAW) sensor that measures the change in frequency
of a quartz crystal resonator induced by mass and viscoelastic changes at the QCM surface (e.g. the binding of target
to an immobilized bioaffinity agent). The resonance of the
quartz crystal is monitored using AC impedance which measures the shift in frequency and can be related to the mass
change. The QCM is highly sensitive and can measure
mass changes in the order of 1 mg/cm2 although can be prone
to interference from non-specific binding effects. Surface
acoustic wave (SAW) sensing is a related technique to
QCM and is classed in the broader group of acoustic wave
devices. SAW sensors changes in the modulation of surface
(as opposed to the bulk) acoustic waves induced by a change
in surface effects such as mass but also includes viscosity,
UV irradiation, magnetic fields, pressure, strain and temperature