Biological & Soft Matter Seminar: Electrolubrication in liquid mixtures: from Poiseuille to plug flow and back

Abstarct:

We describe the “electrolubrication” occurring in liquid mixtures confined between charged surfaces. For a mixture of two liquids, the effective drag decreases markedly in the presence of a field. The origin of this reduction is field-induced phase separation, leading to the formation of two low-viscosity lubrication layers at the surfaces. The thickness of the lubrication layers depends on the Debye length and the mixture correlation length. These layers facilitate larger strain at a given stress.

The effect is strong if the viscosities of the liquids are sufficiently different, the volume fraction of the less viscous liquid is small, the gap between the surfaces is small, and the applied potential is large. The maximum liquid velocity and flux are increased a factor α. In most liquids, α ∼ 1 – 10, and in mixtures of water and glycerol α ∼ 80 – 100 under relatively small potentials.