Condensed Matter Physics Seminar: Faceted liquid emulsion droplets of oil in water

Abstract:

Among all possible shapes of a volume V, a sphere has the smallest surface area A. Therefore, liquid droplets are spherical, minimizing their interfacial energy \gamma A for a given interfacial tension \gamma. We demonstrate that liquid oil droplets in water, stabilized by a common surfactant, adopt icosahedral and other faceted shapes, tunable by temperature T, above the bulk melting point of the oil Tm. Although emulsions have been studied for centuries, no faceted droplets have ever been detected. 

We attribute the observed transition from a spherical to an icosahedral shape to the interplay between \gamma and the elastic properties of the interfacial monomolecular layer, which in these systems crystallizes at T>Tm. The role of topological lattice defects in these systems will be discussed. In addition to faceting, we observe a wide range of other unexpected phenomena, such as a spontaneous splitting of liquid droplets. The common physical mechanism, responsible for all these effects will be demonstrated.

These phenomena allow deeper insights into the fundamentals of molecular elasticity to be gained, opening new horizons for a wide range of technologies, from self-assembly of complex shapes to new delivery strategies in bio-medicine.

Seminar Organizer: Prof. Shimshon Barad