264927 Hydrodynamically-Driven Assembly in Dip Coating From Particle Suspensions

Tuesday, October 30, 2012: 2:00 PM
409 (Convention Center )
Carlos E. Colosqui1, Jeffrey F. Morris1,2 and Howard A. Stone3, (1)Levich Institute of Physico-Chemical Hydrodynamics, New York City, NY, (2)Chemical Engineering, The City College of City University of New York, New York City, NY, (3)Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ

Our computational study of dip coating from a particle suspension reports striped assemblies as those observed experimentally when the thickness of the withdrawn film is comparable to or smaller than the particle size. In this so-called thin-film entrainment regime, particles can assemble within the entrained film due to capillary interactions that minimize the free surface energy. Below a critical withdrawal speed, however, we find that the assembly process mainly occurs within the dynamic meniscus before particles can actually enter the thin film. This type of assembly process is observed when large interfacial forces required to deform the dynamic meniscus prevent particles from entering the film. Interfacial forces are overcome by hydrodynamic drag when a certain number of particles assemble in a close-packed formation. Hence, the assembly process within the dynamic meniscus is driven by hydrodynamic forces imposed by the background flow configuration. At low particle concentrations, the hydrodynamically-driven assembly significantly enhances the order and periodicity of the formed particle arrays.

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See more of this Session: Particulate and Multiphase Flows I
See more of this Group/Topical: Engineering Sciences and Fundamentals