Nonlinear rheology of Laponite suspensions under an external drive

TL;DR

This study explores how steady shear affects the aging and flow behavior of Laponite suspensions, revealing suppression of aging, non-Newtonian shear-thinning, and the formation of non-equilibrium steady states, aligning with recent theories.

Contribution

It demonstrates experimentally that external shear can rejuvenate or slow down aging in Laponite suspensions, confirming theoretical predictions about non-equilibrium rheology.

Findings

Shear suppresses aging in Laponite suspensions.

The system reaches a non-equilibrium stationary state.

The suspension exhibits shear-thinning behavior.

Abstract

We investigate the nonlinear rheological behavior of colloidal suspensions of Laponite, a synthetic clay, driven by a steady and homogeneous shear strain. We show that the external drive leads to a drastic slowing down of the aging dynamics or even, in some cases, in the rejuvenation of the system. Under shear, after a surprisingly long time, the spontaneous aging process observed at rest is suppressed. The system then reaches a non-equilibrium stationary state, characterised by a complex viscosity depending on the applied shear rate. In addition, the glass exhibits a non-Newtonian shear-thinning behavior. These rheological behaviors confirm recent numerical and theoretical predictions.