Issue 29, 2021

Elasticity of colloidal gels: structural heterogeneity, floppy modes, and rigidity

Abstract

Rheological measurements of model colloidal gels reveal that large variations in the shear moduli as colloidal volume-fraction changes are not reflected by simple structural parameters such as the coordination number, which remains almost a constant. We resolve this apparent contradiction by conducting a normal-mode analysis of experimentally measured bond networks of gels of colloidal particles with short-ranged attraction. We find that structural heterogeneity of the gels, which leads to floppy modes and a nonaffine–affine crossover as frequency increases, evolves as a function of the volume fraction and is key to understanding the frequency-dependent elasticity. Without any free parameters, we achieve good qualitative agreement with the measured mechanical response. Furthermore, we achieve universal collapse of the shear moduli through a phenomenological spring-dashpot model that accounts for the interplay between fluid viscosity, particle dissipation, and contributions from the affine and non-affine network deformation.

Graphical abstract: Elasticity of colloidal gels: structural heterogeneity, floppy modes, and rigidity

Supplementary files

Article information

Article type
Communication
Submitted
08 Jan 2020
Accepted
13 Jun 2021
First published
15 Jun 2021

Soft Matter, 2021,17, 6929-6934

Elasticity of colloidal gels: structural heterogeneity, floppy modes, and rigidity

D. Z. Rocklin, L. Hsiao, M. Szakasits, M. J. Solomon and X. Mao, Soft Matter, 2021, 17, 6929 DOI: 10.1039/D0SM00053A

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