Off-equilibrium surface tension in colloidal suspensions

Abstract

We study the fingering instability of the interface between two miscible fluids, a colloidal suspension and its own solvent. The temporal evolution of the interface in a Hele-Shaw cell is found to be governed by the competition between the non-linear viscosity of the suspension and an off-equilibrium, effective surface tension ${\Gamma }_e$. By studying suspensions in a wide range of volume fractions, ${\Phi }_{\mathrm{C}}$, we show that ${\Gamma }_e\sim {\Phi }_{\mathrm{C}}^2$, in agreement with Korteweg's theory for miscible fluids. The surface tension exhibits an anomalous increase with particle size, which we account for using entropy arguments.

5 pages, 5 figures + supplementary material

References in corpus (1)

• Viscous fingering at ultralow interfacial tension

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