Highly nonlinear dynamics in a slowly sedimenting colloidal gel

TL;DR

This study investigates the nonlinear dynamics of a colloidal gel under gravity using advanced light scattering and optical techniques, revealing that microscopic restructuring is driven by macroscopic deformation and follows specific scaling laws.

Contribution

It introduces a novel combination of light scattering and optical methods to analyze sedimenting colloidal gels, highlighting the role of strain rate in microscopic dynamics.

Findings

Sedimentation velocity scales linearly with height during compression.

Microscopic dynamics exhibit scaling when normalized by strain rate.

Gel restructuring is primarily governed by macroscopic deformation.

Abstract

We use a combination of original light scattering techniques and particles with unique optical properties to investigate the behavior of suspensions of attractive colloids under gravitational stress, following over time the concentration profile, the velocity profile, and the microscopic dynamics. During the compression regime, the sedimentation velocity grows nearly linearly with height, implying that the gel settling may be fully described by a (time-dependent) strain rate. We find that the microscopic dynamics exhibit remarkable scaling properties when time is normalized by strain rate, showing that the gel microscopic restructuring is dominated by its macroscopic deformation.