Evolution of nonconformal Landau-Levich-Bretherton films of partially wetting liquids
Michiel Kreutzer (TU Delft - ChemE/Chemical Engineering)
Maulik Shah (TU Delft - ChemE/Product and Process Engineering)
Pravien Parthiban (National University of Singapore)
Saif A. Khan (National University of Singapore)
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Abstract
We experimentally and theoretically describe the dynamics of evolution and eventual rupture of Landau-Levich-Bretherton films of partially wetting liquids in microchannels in terms of nonplanar interface curvatures and disjoining pressure. While both the early-stage dynamics of film evolution and near-collapse dynamics of rupture are understood, we match these regimes and find theoretically that the dimensionless rupture time, Tr, scales with κ-10/7. Here, κ is the dimensionless curvature given by the ratio of the Laplace-pressure discontinuity that initiates film thinning to the initial strength of the disjoining pressure that drives the rupture. We experimentally verify the rupture times and highlight the crucial consequences of early film rupture in digital microfluidic contexts: pressure drop in segmented flow and isolation of droplets from the walls.