Numerical studies of patchy colloids, under nonequilibrium conditions, have been based on Molecular Dynamics (MD) simulations, where the equations of motion of the colloids are solved at each time step. Advanced schemes based on event driven MD have also been developed to mimic, in a probabilistic way, the effect of the medium and reach longer timescales. Although a detailed description of local interactions is achieved, the microscopic approach is limited to a few hundred colloids. In this project we will use a novel stochastic scheme, based on nonequilibrium Monte Carlo (MC) methods, to access system sizes at least one order of magnitude larger.
Two characteristic timescales can be identified: one related with the flux of colloids towards the surface (inter-arrival time) and the other with the bonding of two patches on different colloids or between a colloid and the surface (bonding time). At low concentration of colloids, the inter-arrival time is much larger than the time required for bonding. Thus, we assume that colloids arrive one at a time and adhere instantaneously.
In this project, we will focus on chemical bonds (highly directional and irreversible within the timescale of interest) and thus there are only two bonding possibilities when a colloid approaches the surface: either the patch of the adsorbing colloid is aligned with the adsorbed patch (on the surface or on a previously adsorbed colloid) or the patch-patch interaction promotes the alignment of the patches (through rotation and translation of the adsorbing colloid).
We will investigate in detail the structural and scaling properties of the adsorbed films, interfaces, as well as the growth regimes for a wide range of model parameters.