title: Patterning of small particles by a surfactant-enhanced Marangoni-Bénard instability.
abstract: Evaporating drops provide a means of organizing particles suspended within them. Here, the manner in which surfactants alter these patterns is studied as a function of the surface state of an insoluble monolayer at the drop interface. The surface state is visualized throughout the drop evolution using fluorescence microscopy. A regime of surfactant coverage is identified that creates conditions that enhance the Marangoni-Bénard instability. This result was not anticipated in prior studies, in which surfactants are predicted to prevent this instability. These data demonstrate that, by tuning the liquid-gas boundary condition, the patterns formed from an evaporating drop can be controlled.
authors.affiliation: Department of Chemical Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA.
authors.forename: Van X
authors.initials: VX
authors.lastname: Nguyen
authors.forename: Kathleen J
authors.initials: KJ
authors.lastname: Stebe