Emergence of Multiscale Dynamics in Colloidal Gels

TL;DR

This study reveals complex multiscale dynamics in colloidal gels at low particle concentrations, showing how different regimes emerge as the gel transitions to a nonergodic state, with implications for understanding gel structure and behavior.

Contribution

It uncovers the emergence of multiscale dynamics and identifies three distinct regimes in colloidal gels using differential dynamic microscopy, advancing understanding of gel evolution.

Findings

Three dynamic regimes with distinct $q$-dependent behaviors.

Identification of two characteristic length scales beyond cluster size.

Observation of $ au o q^{-3}$ scaling indicating network homogeneity.

Abstract

To gain insight into the kinetics of colloidal gel evolution at low particle volume fractions $\phi$, we utilize differential dynamic microscopy to investigate particle aggregation, geometric percolation, and the subsequent transition to nonergodic dynamics. We report the emergence of unexpectedly rich multiscale dynamics upon the onset of nonergodicity, which separates the wave vectors $q$ into three different regimes. In the high-$q$ domain, the gel exhibits $\phi$-independent internal vibrations of fractal clusters. The intermediate-$q$ domain is dominated by density fluctuations at the length scale of the clusters, as evidenced by the $q$-independence of the relaxation time $\tau$. In the low-$q$ domain, the scaling of $\tau$ as $q^{-3}$ suggests that the network appears homogeneous. The transitions between these three regimes introduce two characteristic length scales, distinct from the cluster size.