Dip-coating flow in the presence of two immiscible liquids Articles uri icon

publication date

  • July 2021

start page

  • A26-1

end page

  • A26-30

volume

  • 922

International Standard Serial Number (ISSN)

  • 0022-1120

Electronic International Standard Serial Number (EISSN)

  • 1469-7645

abstract

  • Dip coating is a common technique used to cover a solid surface with a thin liquid film,
    the thickness of which was successfully predicted by the theory developed in the 1940s by
    Landau &# Levich (Acta Physicochem. URSS, vol. 17, 1942, pp. 141&;8211#153) and Derjaguin
    (Acta Physicochem. URSS, vol. 20, 1943, pp. 349–352). In this work, we present an
    extension of their theory to the case where the dipping bath contains two immiscible
    liquids, one lighter than the other, resulting in the entrainment of two thin films on the
    substrate. We report how the thicknesses of the coated films depend on the capillary
    number, on the ratios of the properties of the two liquids and on the relative thickness
    of the upper fluid layer in the bath. We also show that the liquid/liquid and liquid/gas
    interfaces evolve independently from each other as if only one liquid were coated, except
    for a very small region where their separation falls quickly to its asymptotic value and
    the shear stresses at the two interfaces peak. Interestingly, we find that the final coated
    thicknesses are determined by the values of these maximum shear stresses.

keywords

  • thin films; coating; multiphase flow