Lawrence Berkeley National Laboratory

Binding particles to an interface between immiscible liquids to reduce interfacial tension underpins the emulsification and phase behaviour of composite liquid systems. Nevertheless, we found that the strong binding and two-dimensional assembly of ferromagnetic particles at a liquid–liquid interface not only suppresses emulsification but also increases interfacial tension. Consequently, the particle-stabilized interface in a cylindrical vessel rapidly and reproducibly adopts the shape of a Grecian urn after vigorous agitation. The suppression of emulsification, the rapid formation of a stable, non-planar equilibrium interface shape and the increase in interfacial tension all originate from attractive in-plane dipolar magnetic interactions between the particles.