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Controllable Internal Mixing In Coalescing Droplets Induced By The Solutal Marangoni Convection Of Surfactants With Distinct Headgroup Architectures, Jerome J. Nash, Patrick T. Spicer, Kendra Erk

School of Materials Engineering Faculty Publications

Through several complementary experiments, an investigation of the bulk and interfacial flows that emerged during the coalescence of two water-in-oil droplets with asymmetric compositional properties was performed. By adding surfactant to one of the coalescing droplets and leaving the other surfactant-free, a strong interfacial tension gradient (i.e., solutal Marangoni) driving energy between the merging droplets generated pronounced internal mixing. The contributions of two distinct types of surfactant, anionic ammonium lauryl sulfate (ALS) and cationic cetyltrimethylammonium bromide (CTAB) on the rate of coalescence bridge expansion and on the generation of opposing flows during coalescence were investigated. All coalescence experiments supported the …