Probing colloidal gels at multiple lengthscales: the role of hydrodynamics

TL;DR

This study investigates how hydrodynamic interactions influence the formation and structure of colloidal gels, revealing that solvent effects promote anisotropic thread formation and open network structures, which are crucial for gelation.

Contribution

It demonstrates the significant impact of hydrodynamics on gel structure formation, using simulations and three-point correlations to quantify anisotropy at multiple scales.

Findings

Hydrodynamics suppress the formation of closed local structures.

Hydrodynamics promote anisotropic thread formation.

Structural differences are evident at interparticle distances just under twice the particle diameter.

Abstract

Colloidal gels are out-of-equilibrium structures, made up of a rarefied network of colloidal particles. Comparing experiments to numerical simulations, with hydrodynamic interactions switched off, we demonstrate the crucial role of the solvent for gelation. Hydrodynamic interactions suppress the formation of larger local equilibrium structures of closed geometry, and instead lead to the formation of highly anisotropic threads, which promote an open gel network. We confirm these results with simulations which include hydrodynamics. Based on three-point correlations, we propose a scale-resolved quantitative measure for the anisotropy of the gel structure. We find a strong discrepancy for interparticle distances just under twice the particle diameter between systems with and without hydrodynamics, quantifying the role of hydrodynamics from a structural point of view.