title: Can surfactant be present at pinch-off of a liquid filament?
abstract: Surfactants lower surface tension and are used to facilitate breakup and spreading. How much surfactant remains where a filament of initial radius R breaks is set by the ratio of convection, which sweeps surfactant away, to diffusion, which replenishes it, or Peclet number Pe proportional, variantR. Thus, as is well known, surfactant concentration Gamma-->0 when a macroscale filament breaks. Here theory and simulation are used to investigate pinch-off of microscopic filaments. At breakup, Gamma is shown to be nonzero but uniform on a filament of negligible Pe. Since R must be finite, the zero-Pe limit is transitory and yields to a final regime. Two such regimes with distinct dynamics characterized by different scaling exponents are reported.
authors.affiliation: School of Chemical Engineering, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Qi
authors.initials: Q
authors.lastname: Xu
authors.forename: Ying-Chih
authors.initials: YC
authors.lastname: Liao
authors.forename: Osman A
authors.initials: OA
authors.lastname: Basaran