From sticking to slipping conditions in QCM-D

Supported lipid bilayers are often studied by using quartz crystal microbalance with dissipation monitoring (QCM-D). The interpretation of the QCM-D data usually implies the no-slip boundary condition at the substrate (QCM) surface. Under certain circumstances, the oscillations of the QCM crystal may however result in the transition to slipping conditions. Employing the Frenkel–Kontorova model, we show that during this transition the amplitude of the bilayer vibrations drops in a stepwise fashion, i.e., the process can be classified as a first-order kinetic phase transition. The model allows us also to scrutinize the corresponding changes in the force between the bilayer and support and dissipation of energy.