Active microrheology of colloidal suspensions of hard cuboids

TL;DR

This study uses active microrheology via simulations to explore how colloidal suspensions of hard cuboids respond to external forces, revealing linear and non-linear viscoelastic behaviors depending on force magnitude and particle geometry.

Contribution

It introduces a simulation-based investigation of active microrheology in colloidal cuboids, highlighting how particle shape and density influence microscopic viscoelastic responses.

Findings

Friction coefficient shows linear behavior at very low and high forces.

Non-linear force-thinning regime appears at intermediate forces.

Probe dynamics depend on cuboid geometry and suspension density.

Abstract

By performing dynamic Monte Carlo simulations, we investigate the microrheology of isotropic suspensions of hard-core colloidal cuboids. In particular, we infer the local viscoelastic behaviour of these fluids by studying the dynamics of a probe spherical particle that is incorporated in the host phase and is dragged by an external force. This technique, known as active microrheology, allows one to characterise the microscopic response of soft materials upon application of a constant force, whose intensity spans here three orders of magnitude. By tuning the geometry of cuboids from oblate to prolate as well as the system density, we observe different responses that are quantified by measuring the effective friction perceived by the probe particle. The resulting friction coefficient exhibits a linear regime at forces that are much weaker and larger than the thermal forces, whereas a non-linear, force-thinning regime is observed at intermediate force intensities.