Issue 19, 2024

Confinement controls the creep rate in soft granular packings


Flow in soft materials encompasses a wide range of viscous, plastic and elastic phenomena which provide challenges to modelling at the microscopic level. To create a controlled flow, we perform falling ball viscometry tests on packings of soft, frictionless hydrogel spheres. Systematic creep flow is found when a controlled driving stress is applied to a sinking sphere embedded in a packing. Here, we take the novel approach of applying an additional global confinement stress to the packing using an external load. This has enabled us to identify two distinct creep regimes. When confinement stress is small, the creep rate is independent of the load imposed. For larger confinement stresses, we find that the creep rate is set by the mechanical load acting on the packing. In the latter regime, the creep rate depends exponentially on the imposed stress. We can combine the two regimes via a rescaling onto a master curve, capturing the creep rate over five orders of magnitude. Our results indicate that bulk creep phenomena in these soft materials can be subtly controlled using an external mechanical force.

Graphical abstract: Confinement controls the creep rate in soft granular packings

Article information

Article type
27 Dec 2023
24 Apr 2024
First published
01 May 2024
This article is Open Access
Creative Commons BY license

Soft Matter, 2024,20, 4015-4020

Confinement controls the creep rate in soft granular packings

J. A. Dijksman and T. Mullin, Soft Matter, 2024, 20, 4015 DOI: 10.1039/D3SM01755A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content.

Social activity