http://www.springerlink.com/openurl.asp?genre=article&id=doi:10.1007/s00396-005-1391-5

Abstract: Evaporation of a droplet of silica microsphere suspension on a polystyrene and poly(methyl methacrylate) blend film with isolated holes in its surface has been exploited as a means of particles selfassembly. During the retraction of the contact line of the droplet, spontaneous dewetting combined
with the strong capillary force pack the silica microspheres into the holes
in the polymer surface. Complex aggregates of colloids are formed
after being exposed to acetone vapor. The morphology evolution of
the underlying polymer film by exposure to acetone solvent vapor is
responsible for the complex aggregates of colloids formation.