title: Estimating surfactant surface coverage and decomposing its effect on drop deformation.
abstract: A novel method is introduced to estimate surface coverage and the equation of state of insoluble surfactant on droplets, involving measurement of interfacial tension on a single parent drop and progressively subdivided generations of daughter drops. This has enabled quantitative decomposition of the dilution, tip-stretching, and Marangoni effects of surfactants on drop deformation. For a small viscosity ratio of 0.09, the Marangoni effect dominates, increasing first and then decreasing with surface coverage, the dilution effect is significant at high, and tip-stretching only at low surface coverage. For a viscosity ratio of 2.3, the dilution effect dominates, and neither Marangoni nor tip-stretching effects play an important role.
authors.affiliation: Unilever Research U.S., 45 River Road, Edgewater, New Jersey 07020, USA.
authors.forename: Y T
authors.initials: YT
authors.lastname: Hu
authors.forename: A
authors.initials: A
authors.lastname: Lips