title: Stratification Dynamics in Drying Colloidal Mixtures.
abstract: Stratification in binary colloidal mixtures was investigated using implicit-solvent molecular dynamics simulations. For large particle size ratios and film Péclet numbers greater than unity, smaller colloids migrated to the top of the film, while big colloids were pushed to the bottom, creating an "inverted" stratification. This peculiar behavior was observed in recent simulations and experiments conducted by Fortini et al. [ Phys. Rev. Lett. 2016 , 116 , 118301 ]. To rationalize this behavior, particle size ratios and drying rates spanning qualitatively different Péclet number regimes were systematically studied, and the dynamics of the inverted stratification were quantified in detail. The stratified layer of small colloids was found to grow faster and to larger thicknesses for larger size ratios. Interestingly, inverted stratification was observed even at moderate drying rates where the film Péclet numbers were comparable to unity, but the thickness of the stratified layer decreased. A model based on dynamical density functional theory is proposed to explain the observed phenomena.
authors.affiliation: Department of Chemical and Biological Engineering, Princeton University , Princeton, New Jersey 08544, United States.
authors.forename: Michael P
authors.identifier: 0000-0002-9561-4165
authors.initials: MP
authors.lastname: Howard
authors.affiliation: Institute of Physics, Johannes Gutenberg University Mainz , Staudingerweg 7, 55128 Mainz, Germany.
authors.forename: Arash
authors.identifier: 0000-0003-0563-825X
authors.initials: A
authors.lastname: Nikoubashman
authors.affiliation: Department of Chemical and Biological Engineering, Princeton University , Princeton, New Jersey 08544, United States.
authors.forename: Athanassios Z
authors.identifier: 0000-0002-8152-6615
authors.initials: AZ
authors.lastname: Panagiotopoulos