Understanding QCM-D Response to Deposition and Attachment of Bacteria and Particles on Surfaces

Ariela Tarnapolsky, Chemical Engineering, Technion - Israel Institute of Technology, Haifa, Israel
Viatcheslav Freger, Chemical Engineering, Technion - Israel Institute Of Technology, Haifa, Israel

Quartz crystal microbalance with dissipation monitoring (QCM-D) is a powerful tool for studying adhesion, yet its use for analyzing deposition and attachment of abiotic microparticles and living cells on surfaces from solutions has been hampered by the difficulties of interpreting the response and loading regimes. In this study, we systematically investigate QCM-D response to deposition of abiotic microparticles as well as Pseudomonas fluorescence bacteria by modulating different characteristics of particles and substrate, including surface chemistries and mechanical properties, particle size, and solution composition. Using the electromechanical analogy, we constructed a physical model for the interaction of particles with QCM-D in the form of an equivalent circuit, in which inertial, elastic and dissipative loads are represented by appropriately connected elements, whose mechanical impedance can be related to actual physical characteristics of the particle and surface. In this way we could observe and understand the entire spectrum of possible responses and transition from inertial to elastic loading for model abiotic polystyrene and silica particles and pinpoint the effects of different physical parameters. The only uncertainty of the model was associated with the contact mechanics relation, however, this could be resolved by adjusting the contact radius as an independent parameter. Ultimately, we found that the model offers a reasonable quantitative prediction of the observed response and its frequency dependence for different abiotic particles and substrates as well as for bacterial cells. This model can be used to interpret and analyze QCM-D results and help turn it to a quantitative tool for studying deposition and attachment of micro-colloids and living cells on surfaces.