Yield-stress fluids are soft materials whose behavior depends on the stress applied with a threshold mechanism: below the threshold (yield point) they behave like an elastic solid; above the threshold they flow like a liquid. As a model, in our laboratories we use an oil-in-water emulsion with the addiction of surfactants to prevent phase separation. Yielding is due to the concentration of oil drops in water: with increasing concentration of oil drops the viscosity change from a constant value – for low droplets concentration – to at steeper increasing value – for high droplets concentration.
At the moment we are studying these systems on two fronts: by making them flux in a microfluidic channel patterned with right-angle triangular-shaped posts on the bottom part (a); by studying thermal convection under Rayleigh-Bénard configuration (b).