Hydrodynamics strongly affect the dynamics of colloidal gelation but not gel structure

TL;DR

This study uses simulations to show that hydrodynamic interactions significantly influence the rate of colloidal gelation but do not alter the final gel structure, resolving previous conflicting findings.

Contribution

It demonstrates that hydrodynamic interactions affect gelation dynamics without changing the resulting gel structure, clarifying longstanding debates.

Findings

Hydrodynamic interactions speed up gelation at low volume fractions.

Hydrodynamic interactions slow down gelation at high volume fractions.

Final gel structures are nearly identical with or without hydrodynamic interactions.

Abstract

Colloidal particles with strong, short-ranged attractions can form a gel. We simulate this process without and with hydrodynamic interactions (HI), using the lattice-Boltzmann method to account for presence of a thermalized solvent. We show that HI speed up and slow down gelation at low and high volume fractions, respectively. The transition between these two regimes is linked to the existence of a percolating cluster shortly after quenching the system. However, when we compare gels at matched 'structural age', we find nearly indistinguishable structures with and without HI. Our result explains longstanding, unresolved conflicts in the literature.