A new theoretical model is formulated enabling quantitative analysis of QCM response for heterogeneous loads consisting of nano- and microparticles. In contrast to previous approaches, the influence of particle coverage and structure is described using a universal correction function in an ab initio manner. Explicit analytical expressions for the frequency and dissipation shifts are derived for the entire range of particle size under the rigid contact regime. The solvent coupling function are also calculated enabling to determine the dry coverage using the QCM measurements. These functions furnish the upper limit of the QCM signal, which can be attained for sensor providing perfect adhesion of particles. Correction function accounting for the finite adhesion strength (soft contact regime) are also derived. The theoretical results are confronted with QCM and atomic force microscopy (AFM) measurements of positively charged polymer particle deposition on silica sensors. Main features of the theoretical model are confirmed, especially the abrupt decrease in the QCM water factor (wet mass) with the particle coverage and the overtone number. The latter effect is especially pronounced for microparticles under the soft contact regime, where the higher number overtones produce a negligible QCM signal. These results represent a useful reference data for the interpretation of protein and bioparticles, e.g., virus and bacteria attachment processes to various substrates.

Hydrodynamic coupling effects pertinent to QCM investigation of nanoparticle adsorption kinetics were evaluated using atomic force microscopy and the theoretical modeling. Monodisperse polymer particles of the size between 26 and 140 nm and the density of 1.05 g cm-3 were used. The zeta potential of particles was opposite to the substrate surface zeta potential that promoted their irreversible adsorption on the silica sensor. The experimental kinetic data were interpreted in terms of theoretical calculations derived from the hybrid random sequential adsorption model. This allowed to determine the amount of hydrodynamically coupled solvent (electrolyte) for the absolute particle coverage range up to 0.5. The coupling function representing the ratio of the solvent to the particle volumes was also determined and used to explicitly calculate the solvent level in particle monolayers. It is shown that the solvent level abruptly increases with the particle coverage attaining values comparable with the particle size. One can expect that these results can serve as useful reference data for the interpretation of protein adsorption kinetics on rough surfaces where the presence of stagnant solvent is inevitable.