Order formation of colloidal nanoparticles adsorbed on a substrate with friction

We examine the adsorption process and order formation of colloidal nanoparticles on a planar surface with friction. We perform Brownian dynamics simulations with a three-dimensional cell model in which the particle–particle and particle–substrate interactions are modeled on the DLVO theory, and examine the effects of the friction acting between the adsorbed particles and the substrate on the adsorbed structure formed on the substrate. The results obtained are as follows: when the friction is so strong that the adsorbed particles are stuck to the substrate, ordered structures never form, which seems to be quite natural. However, when the magnitude of the frictional force is moderate, an ordered structure can form even with low coverage because the frictional force aids order formation. This is because the friction counterbalances the particles’ Brownian motion, which would otherwise disturb the ordered structure. Furthermore, through a detailed examination of the distribution of the Brownian motion, it is demonstrated that an increase in the friction has a similar effect as a decrease in temperature.