From random sequential adsorption to ballistic deposition: A general view of irreversible deposition processes

Irreversible adsorption/deposition processes are defined as processes in wh ich, once adsorbed, the particles can neither desorb from nor diffuse along the surface. These processes are commonly encountered when macromolecules or colloidal particles deposit on solid surfaces. This article presents a g eneral and unified picture of these processes based mainly on experimental, simulation, and theoretical results accumulated by the authors over recent years. We describe first the influence of surface exclusion effects on the adsorption process under negligible influence of gravity. Essential result s relative to the random sequential adsorption (RSA) model are given, The i nfluence of particle diffusion and hydrodynamic interactions during the ads orption process in the deposition zone near the deposition plane on the str ucture of the assembly of deposited particles and on the adsorption kinetic s are analyzed. It is shown that hydrodynamic interactions have the tendenc y to randomize the position of the particles over the available surface and thus to render the adsorption process RSA-like. Model predictions are conf irmed by experimental data. For the deposition of larger particles gravity plays an important role, and the deposition process is characterized by a d imensionless particle radius R* The case of an infinite value of R* is firs t discussed and the ballistic deposition (BD) model is described. The depos ition processes characterized by R* values ranging from 0.6 to 3.3 are then analyzed. For such R* values one observes a smooth transition from the RSA to the ED behavior when R* is increased.