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Arrest and Restoration of Capillary Assembly In a Surfactant Monolayer

Eric Lewandowski1, Jorge A. Bernate2, Peter C. Searson3, and Kathleen J. Stebe1. (1) Chemical and Biomolecular Engineering, Johns Hopkins University, 3400 N. Charles St., Maryland Hall Rm 221, Baltimore, MD 21218, (2) Chemical and Biomolecular Engineering Department, Johns Hopkins University, 221 Maryland Hall 3400 North Charles Street, Baltimore, MD 21218, (3) Johns Hopkins University, 3400 N. Charles St, Baltimore, MD 21218

Non-spherical particles at fluid interfaces cause the interface to distort at the three phase contact line to satisfy their boundary conditions. Overlapping distortions create capillary interactions that drive particle assembly. These capillary interactions can be arrested at interfaces which are tangentially immobile. Insoluble surfactant monolayers are used to change the dynamics of the assembly process and at high enough concentrations halt the assembly. Solubilty of the surfactant is then altered by changing subphase pH, thereby restoring particle mobility and self-assembly. Particle orientation is also explored at clean interfaces in the presence of an external field.