Mean-field microrheology of a very soft colloidal suspension: inertia induces shear-thickening

TL;DR

This paper demonstrates that inertia in soft colloidal suspensions can cause shear-thickening behavior by enabling density waves, supported by a mean-field analytical approach.

Contribution

It introduces a mean-field analytical model showing how inertia induces shear-thickening in dense soft colloidal suspensions.

Findings

Inertia can induce shear-thickening in colloidal suspensions.

Density waves propagate due to inertia, affecting rheology.

Analytical expression for drag force in the presence of inertia.

Abstract

Colloidal suspensions have a rich rheology and can exhibit shear-thinning as well as shear-thickening. Numerical simulations recently suggested that shear-thickening may be attributed to the inertia of the colloids, besides the hydrodynamic interactions between them. Here, we consider the ideal limit of a dense bath of soft colloids following an underdamped Langevin dynamics. We use a mean-field equation for the colloidal density to get an analytical expression of the drag force felt by a probe pulled at constant velocity through the suspension. Our results show that inertia can indeed induce shear-thickening by allowing density waves to propagate through the suspension.