  A simple multiscale approach to the diffusion-driven adsorption from a
solution to a solid surface is presented. The model combines two important
features of the adsorption process: (i) the kinetics of the chemical reaction
between adsorbing molecules and the surface; and (ii) geometrical constraints
on the surface made by molecules which are already adsorbed. The process (i) is
modelled in a diffusion-driven context, i.e. the conditional probability of
adsorbing a molecule provided that the molecule hits the surface is related to
the macroscopic surface reaction rate. The geometrical constraint (ii) is
modelled using random sequential adsorption (RSA), which is the sequential
addition of molecules at random positions on a surface; one attempt to attach a
molecule is made per one RSA simulation time step. By coupling RSA with the
diffusion of molecules in the solution above the surface the RSA simulation
time step is related to the real physical time. The method is illustrated on a
model of chemisorption of reactive polymers to a virus surface.
