Quartz Crystal Microbalance with Dissipation (QCM-D)
In QCM-D the dissipation and resonance frequency of a quartz crystal are used to follow the formation of surface films in solution. These films can be comprised of whole cells, proteins, or polymers. Their formation is monitored on surfaces (nanometer to micrometer thick) as diverse as gold, polyurethane, titanium, and polycarbonate. The kinetics of both mass and structural changes can be measured. If the layer is sufficiently rigid, the Sauerbrey relation can be used to determine the mass of the adhering layer. Less rigid films (dissipation > 1x10-6 per 5 Hz) dampen the oscillation of the crystal such that this relation will underestimate mass. In this case the dissipation at multiple frequencies is used to determine the viscosity, elasticity and thickness of the film. While the QCM (used for monitoring film deposition in vacuum) is itself not a new technology, QCM-D is distinct in that mulitple frequencies are recorded as well as the dissipation. QCM-D measurements require very accurate temperature control becasue the viscosity and quartz resonance frequency are both temperature dependent.
Coating of titanium (used in medical implants) with synthetic peptides to lower rejection rates
Self assebly of polyelectrolyte multilayers embedded with phospholipid vesicles
Studies of protein and whole cell adhesion to polymeric surfaces
Sample volume required above the crystal is only 50 ul.
Unlike SPR, QCM-D takes into account hydration of the layers.