Evaporation-driven assembly of colloidal particles
  Colloidal particles absorbed at the interface of a liquid droplet arrange into unique packings during slow evaporation (Manoharan et al. Science 301 pp 483-487). We present a numerical and theoretical analysis of the packing selection problem. The selection of a unique packing arises almost entirely from geometrical constraints during the drying. 
Eric Lauga, Michael P. Brenner