Gels under stress: The origins of delayed collapse

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Vol. 458; pp. 126 - 133
• Main Authors: Teece, Lisa J., Hart, James M., Hsu, Kerry Yen Ni, Gilligan, Stephen, Faers, Malcolm A., Bartlett, Paul
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 20.09.2014
• Subjects: Colloids; Confocal microscopy; Gels; gravity; Sedimentation; Confocal microscopy; Gels; Sedimentation; Colloids
• ISSN: 0927-7757; 1873-4359
• DOI: 10.1016/j.colsurfa.2014.03.018

[Display omitted] •We review the process of delayed collapse in weak colloidal gels.•We present new data on the microscopic processes which occur during delay.•We propose a new microscopic model of collapse.•We validate the model by analyzing new experimental data on the effect of an external force on gel collapse. Attractive colloidal particles can form a disordered elastic solid or gel when quenched into a two-phase region, if the volume fraction is sufficiently large. When the interactions are comparable to thermal energies the stress-bearing network within the gel restructures over time as individual particle bonds break and reform. Typically, under gravity such weak gels show a prolonged period of either no or very slow settling, followed by a sudden and rapid collapse – a phenomenon known as delayed collapse. The link between local bond breaking events and the macroscopic process of delayed collapse is not well understood. Here we summarize the main features of delayed collapse and discuss the microscopic processes which cause it. We present a plausible model which connects the kinetics of bond breaking to gel collapse and test the model by exploring the effect of an applied external force on the stability of a gel.