In situ studies of particle deposition on non-transparent substrates

An oblique impinging-jet (OBIJ) cell was developed, suitable for colloid deposition studies at various interfaces including the practically significant case of non-transparent substrates. Particle transport conditions in the cell were quantitatively evaluated by studying kinetics of polystyrene latex particle deposition on mica. The dependence of the reduced particle flux (mass transfer coefficient) on the flow Reynolds number (Re) was determined by in situ microscope enumeration of adsorbed particles. It was demonstrated, in accordance with previous results for the orthogonal impinging-jet cell, that the flux increased significantly with the Re number. This was interpreted in terms of the convective diffusion theory incorporating the hydrodynamic and specific interactions. The governing transport equation originating from this theory was solved numerically, for the region near the stagnation point, by using the finite-difference method. These numerical solutions were used for nonlinear fitting of the flow intensity parameter α dependence on the Re number. In this way, the transport conditions in the vicinity of the stagnation point were fully characterized. The method was applied for studying kinetics of latex adsorption on non-transparent, plasma treated polymeric substrates. It was demonstrated that a prolonged treatment (ca. 20 min) enhanced considerably particle deposition rate that attained values pertinent to the model mica substrate.