Structural criterion for the onset of rigidity in a colloidal gel

TL;DR

This paper identifies that the onset of rigidity in colloidal gels occurs when particles with three or more bonds percolate, highlighting the importance of bond connectivity and interactions in gel rigidity.

Contribution

It introduces a structural criterion based on percolation of multi-bonded particles to predict gel rigidity, combining simulations and rheology.

Findings

Rigidity onset coincides with percolation of particles with ≥3 bonds

Rigidity arises after connectivity percolation due to bond interactions

Provides insight into low-valence colloidal gel mechanics

Abstract

Identifying the necessary conditions for the onset of rigidity in a gel remains a challenge. It has been suggested that local particle coordination could be used to establish such conditions, but rigid gels occur for various coordination numbers. Combining simulations, oscillatory rheology, and a percolation analysis, for particles where the valence can be controlled, we find that the onset of rigidity coincides with the percolation of particles with three or more bonds, which arises after the connectivity percolation. We show that the rigidity results from an interplay of bonding and non-bonding interactions, providing insight into low-valence colloidal gel rigidity.