Interfaces in soft matter

Microfluidics and application to biology

Patterns at fluid interfaces

Have you ever pay attention how quiet is a water surface behind a boat wake? Indeed, the presence of complex flows below the fluid interface modifies significantly the propagation of surface waves. We take inspiration from this principle to design and structure fluid interface but by confining surbsurface swirling flows. Such confinements have been realized in the context of shock waves, hydraulic bump, leidenfrost levitation or Marangoni-driven flows. We investigate theoretically this vortex-mediated interface response to engineer new forms of information propagation at fluid interfaces.

Dynamics of soft interfaces

Surface waves and bio-locomotion

Interfacial phoretic and Marangoni flows

An interface between two liquids or between a solid and a liquid or between two solids is at the microscopic scale a continuum with a concentration of species from the two bulk systems in contact. These species interact and one can define interface energy, associated with these interactions, Any gradients of this energy induce transport within the interface, which at the hydrodynamic level of description induce velocity slip or stress jump at the interface. These boundary conditions, in turn, develop flows and/or stress in the bulk phases. We study and use these flow to self propel Janus colloids or water droplets in oil.

Disordered interfaces for fracture

We use the framework of elastic interfaces in disordered media, which encompasses systems such as domain walls in ferromagnetic materials, or the contact line in wetting problems, to study the properties of fracture. For brittle materials, where the interface represents the fracture front, we have calculated the effect of the material disorder on its toughness (its resistance to fracture). For quasi-brittle materials, the material gets damaged before a macroscopic fault develops. In this case the elastic interface model should be adapted to describe the properties of the damage field.

See also: Collective effects in compressive fracture of disordered materials

Polymer nanohydrodynamics and interfacial slip

Self-healing and mechanical metamaterials