We describe an experimental technique for the production of highly monodisperse emulsions (with minimum achievable polydispersities <3%). The phase to be dispersed is introduced into a coflowing, surfactant-laden continuous phase via a tapered capillary. Drops detach from the capillary when the streamwise forces exceed the force due to interfacial tension. Drop size is a function of the capillary tip diameter, the velocity of the continuous phase, the extrusion rate, and the viscosities and interfacial tension of the two phases. Emulsions composed of a variety of fluids and with drop sizes ranging from 2 to 200 μm have been produced using this technique.

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Monodisperse Emulsion Generation via Drop Break Off in a Coflowing Stream

Influence of interfacial rheology on foam and emulsion properties.

Studies on interfacial behavior and wettability change phenomena by ionic and nonionic surfactants in presence of alkalis and salt for enhanced oil recovery

Foams are dispersions of bubbles in liquids, often water. They are frequently stabilized by surfactant or polymer, but like Pickering emulsions, they can be also stabilized solely by particles. If the particles have a moderate hydrophobicity, the foams can be extremely stable (lifetimes of the order of years). Due to technical preparation difficulties, very few studies can be found in the literature to date. We will discuss the origin of these difficulties. We will also describe experiments using partially hydrophobic fumed silica particles, in which the foam properties were correlated with the properties of spread and adsorbed layers of these particles at the air–water interface. These combined experiments allowed us to define the conditions necessary to stop bubble disproportionation.

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D. Langevin

Papers

Dynamic Surface-Tension of Ionic Surfactant Solutions