Distribution of particles during solvent evaporation from films

We examine films, subject to evaporation, that contain particles. The volume fraction of particles increases as solvent is removed up to a maximum value of close packing. The governing equation for evolution of particle volume fraction is derived and numerical solutions obtained for various Peclet numbers. For large Peclet numbers an asymptotic solution gives the position and functional form of a front of close packed particles which passes through the film. For intermediate Peclet numbers the scaling for the spatial gradient in volume fraction is found to be Pe(1/2). This is different from conventional sedimentation, where convection rather than diffusion dominates. (C) 2004 Elsevier Ltd. All rights reserved.