Foam coarsening in a yield stress fluid.

Foams coarsen because of pressure differences between bubbles of different sizes. We study the coarsening of quasi-2D foams made from model yield stress fluids: concentrated oil-in-water emulsions. We show that increasing the yield stress of the foamed emulsion continuous phase leads to both slower coarsening and irreversible structural change.

Hierarchical bubble size distributions in coarsening wet liquid foams.

Coarsening of two-phase systems is crucial for the stability of dense particle packings such as alloys, foams, emulsions, or supersaturated solutions. Mean field theories predict an asymptotic scaling state with a broad particle size distribution. Aqueous foams are good model systems for investigations of coarsening-induced structures, because the continuous liquid as well as the dispersed gas phases are uniform and isotropic.

Coarsening transitions of wet liquid foams under microgravity conditions.

We report foam coarsening studies which were performed in the International Space Station (ISS) to suppress drainage due to gravity. Foams and bubbly liquids with controlled liquid fractions between 15 and 50% were investigated to study the transition between bubble growth laws previously reported near the dry limit → 0 and the dilute limit → 1 (Ostwald ripening). We determined the coarsening rates for the driest foams and the bubbly liquids, they are in close agreement with theoretical predictions.

Soft matter dynamics: A versatile microgravity platform to study dynamics in soft matter.

We describe an experiment container with light scattering and imaging diagnostics for experiments on soft matter aboard the International Space Station (ISS). The suite of measurement capabilities can be used to study different materials in exchangeable sample cell units. The currently available sample cell units and future possibilities for foams, granular media, and emulsions are presented in addition to an overview of the design and the diagnostics of the experiment container.

Elastic behavior of confined soap froth.

The elastic response of ordered 3D soap froth, in which N layers of cells are confined between two rigid walls, is analyzed. Surface Evolver simulations are used to compute the equilibrium structure, which consists of a layer of Fejes-Toth cells at each wall and N - 2 core layers of Kelvin cells. The reference state corresponds to the plate spacing ho that achieves isotropic stress; and the foam confinement is varied by changing h.