Quartz crystal microbalance is a method in which a disk of piezo-electric quartz is used as a balance. By monitoring the mechanical resonance frequency and quality factor of the disk one can obtain the mass absorbed to the disk surface. The Multifrequency Lockin Amplifier, MLA-3, can be used to track resonance and damping coefficients at high rates using multifrequency comb excitation allowing for for ultrafast quartz crystal microbalance.
The MLA-3 was also used to realize electrochemical quartz crystal microbalance in work by Professor Diethelm Johannsmann at TU Clausthal. They were able to observe fast pH-driven viscosity changes in albumin solutions.