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Wetting of yield-stress fluids

By: Catherine Barentin
From: U. Lyon 1, France
At: Online - Zoom
[2021-06-17]

Yield-stress fluids such as emulsions, suspensions, gels or foams exhibit interestingmechanical properties depending on the applied stress. Indeed they behave like an elasticbelow a critical stress called "yield stress" and flow like a liquid above it. This intermediatebehavior solid/liquid makes them particularly interesting for applications (food industry,cosmetics, building industry), but fundamentally difficult to describe.

In this seminar, I will study the wetting properties of yield stress fluids by performing threecapillary experiments: a) capillary rise [1] , b) adhesion due to a capillary bridge [2] and c)spreading of a drop of a yied-stress fluid [3]. In the case of simple fluids, such experimentsare classical and the wetting laws (Jurin's law or Young law) are well kown.Here I will study the influence of the yield stress on the final capillary rise or on the finalcontact angle. I will also show the strong impact of the dynamic history and of the boundaryconditions [4]. More importantly, I will show that exploring the competition between surfacetension, which is an equilibrium property, and yield stress effects that often keep the systemout of thermodynamic equilibrium due to a dynamic arrest is possible as soon as forcebalances are performed.

 

[1] B. Géraud et al. , Eur. Phys. Letters, v 107, 58002 (2014); 

[2] L. Jorgensen et al., Soft Matter, v 11, 5111 (2015);

[3] G. Martouzet et al., Phys Rev Fluids, accepted (2021);

[4] J. Péméja et al., Phys. Rev. Fluids, v4, 033301 (2019);