A quartz crystal microbalance (QCM) measures a mass per unit area by measuring the change in frequency of a quartz crystal resonator. The resonance is disturbed by the addition or removal of a small mass due to oxide growth/decay or film deposition at the surface of the acoustic resonator. The QCM can be used under vacuum, in gas phase ("gas sensor", first use described by [58]) and more recently in liquid environments. It is useful for monitoring the rate of deposition in thin film deposition systems under vacuum. In liquid, it is highly effective at determining the affinity of molecules (proteins, in particular) to surfaces functionalized with recognition sites. Larger entities such as viruses or polymers are investigated, as well. Frequency measurements are easily made to high precision (discussed below); hence, it is easy to measure mass densities down to a level of below 1 μg/cm2. In addition to measuring the frequency, the dissipation is often measured to help analysis. The dissipation is a parameter quantifying the damping in the system, and is related to the sample's viscoelastic properties.
"Quartz crystal microbalance." Wikipedia, The Free Encyclopedia. 4 Feb 2008, 14:01 UTC. Wikimedia Foundation, Inc. 7 Feb 2008 <http://en.wikipedia.org/w/index.php?title=Quartz_crystal_microbalance&oldid=189022845>.
