title: Armoring a droplet: soft jamming of a dense granular interface.
abstract: Droplets and bubbles protected by armors of particles have found vast applications in encapsulation, stabilization of emulsions and foams, or flotation processes. The liquid phase stores capillary energy, while concurrently the solid contacts of the granular network induce friction and energy dissipation, leading to hybrid interfaces of combined properties. By means of nonintrusive tensiometric methods and structural measurements, we distinguish three surface phases of increasing rigidity during the evaporation of armored droplets. The emergence of surface rigidity is reminiscent of jamming of granular matter, but it occurs differently since it is marked by a step by step hardening under surface compression. These results show that the concept of the effective surface tension remains useful only below the first jamming transition. Beyond this point, the surface stresses become anisotropic.
authors.affiliation: Departamento de Física Universidad de Santiago de Chile, Avenida Ecuador 3493, 9170124 Estación Central, Santiago, Chile.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Lagubeau
authors.affiliation: Departamento de Física Universidad de Santiago de Chile, Avenida Ecuador 3493, 9170124 Estación Central, Santiago, Chile.
authors.forename: Antonella
authors.initials: A
authors.lastname: Rescaglio
authors.affiliation: Departamento de Física Universidad de Santiago de Chile, Avenida Ecuador 3493, 9170124 Estación Central, Santiago, Chile.
authors.forename: Francisco
authors.initials: F
authors.lastname: Melo
mesh_terms: D016880:Anisotropy; D057446:Hydrodynamics; D013500:Surface Tension