Gels under stress: The origins of delayed collapse

Teece, Lisa J.; Hart, James M.; Hsu, Kerry Yen Ni; Gilligan, Stephen T; Faers, Malcolm A.; Bartlett, Paul

doi:10.1016/j.colsurfa.2014.03.018

Cited by 27 publications

(31 citation statements)

References 29 publications

(74 reference statements)

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“…The most common and ultimate metric characterizing the macroscopic feature of the collapse process is the time evolution of the height profile, h(t) of a gel. Measurements of h(t) are used to determine the characteristic timescale of the process, t d , and to quantify observed power-law or exponential decays of height profiles (Weeks et al 2000;Teece et al 2014;Harich et al 2016). The collapse dynamics of colloidal dispersions with long-ranged attractions, relative to the primary particle radius, are relatively well understood.…”

Section: Introductionmentioning

confidence: 99%

“…Careful confocal microscopy studies of the association and dissociation processes of individual particles and gel strands in the network structure have also shown that there is a direct link between the macroscopic mean delay time t d and the lifetime of an individual colloid-colloid bond (Gopalakrishnan et al 2006;Teece et al 2014). As a result simple phenomenological models have been developed that describe the collapse process in terms of a number of sticky inter-particle bonds undergoing sequential activated bond breaking and leading to a loss of network integrity.…”

Section: Introductionmentioning

confidence: 99%

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Modelling a hydrodynamic instability in freely settling colloidal gels

2018

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Attractive colloidal dispersions, suspensions of fine particles which aggregate and frequently form a space spanning elastic gel are ubiquitous materials in society with a wide range of applications. The colloidal networks in these materials can exist in a mode of free settling when the network weight exceeds its compressive yield stress. An equivalent state occurs when the network is held fixed in place and used as a filter through which the suspending fluid is pumped. In either scenario, hydrodynamic instabilities leading to loss of network integrity occur. Experimental observations have shown that the loss of integrity is associated with the formation of eroded channels, so-called streamers, through which the fluid flows rapidly. However, the dynamics of growth and subsequent mechanism of collapse remain poorly understood. Here, a phenomenological model is presented that describes dynamically the radial growth of a streamer due to erosion of the network by rapid fluid back flow. The model exhibits a finite-time blowup -the onset of catastrophic failure in the gel -due to activated breaking of the inter-colloid bonds. Brownian dynamics simulations of hydrodynamically interacting and settling colloids in dilute gels are employed to examine the initiation and propagation of this instability, which is in good agreement with the theory. The model dynamics are also shown to accurately replicate measurements of streamer growth in two different experimental systems. The predictive capabilities and future improvements of the model are discussed and a stability-state diagram is presented providing insight into engineering strategies for avoiding settling instabilities in networks meant to have long shelf lives.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modelling a hydrodynamic instability in freely settling colloidal gels

2018

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“…Comparable dynamic control of the aggregation process has been realised in phase-separating colloidal suspensions, which may afford a kinetically trapped gel material before coalescing into a more compact equilibrium arrangement. 107 The mechanism of degelation may also exhibit unexpected complexity. A common observation is that the temperature of the gel-sol transition exceeds Tgel, due to the kinetic stability of the aggregate state.…”

Section: Switchable Gelationmentioning

confidence: 99%

Gels with sense: supramolecular materials that respond to heat, light and sound

2016

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. (2016) 'Gels with sense : supramolecular materials that respond to heat, light and sound.', Chemical society reviews., 45 (23). pp. 6546-6596. Further information on publisher's website:https://doi.org/10.1039/C6CS00435KPublisher's copyright statement:Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Advances in the field of supramolecular chemistry have made it possible, in many situations, to reliably engineer soft materials to address a specific technological problem. Particularly exciting are "smart" gels that undergo reversible physical changes on exposure to remote, non-invasive environmental stimuli. This review explores the development of gels which are transformed by heat, light and ultrasound, as well as other mechanical inputs, applied voltages and magnetic fields. Focusing on small-molecule gelators, but with reference to organic polymers and metal-organic systems, we examine how the structures of gelator assemblies influence the physical and chemical mechanisms leading to thermo-, photo-and mechano-switchable behaviour. In addition, we evaluate how the unique and versatile properties of smart materials may be exploited in a wide range of applications, including catalysis, crystal growth, ion sensing, drug delivery, data storage and biomaterial replacement.

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“…1,2 Examples of such consumer products include fabric enhancers, cosmetics, and shampoos. 3 In many of these applications, the dispersed phase has a higher density than the continuous phase. Therefore, sedimentation of the dispersed phase may occur due to gravity.…”

Section: Introductionmentioning

confidence: 99%

Numerical and experimental analysis of the sedimentation of spherical colloidal suspensions under centrifugal force

et al. 2018

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Understanding the sedimentation behaviour of colloidal suspensions is crucial in determining their stability. Since sedimentation rates are often very slow, centrifugation is used to expedite sedimentation experiments. The effect of centrifugal acceleration on sedimentation behaviour is not fully understood. Furthermore, in sedimentation models, interparticle interactions are usually omitted by using the hard-sphere assumption. This work proposes a one-dimensional model for sedimentation using an effective maximum volume fraction, with an extension for sedimentation under centrifugal force. A numerical implementation of the model using an adaptive finite difference solver is described. Experiments with silica suspensions are carried out using an analytical centrifuge. The model is shown to be a good fit with experimental data for 480 nm spherical silica, with the effects of centrifugation at 705 rpm studied. A conversion of data to Earth gravity conditions is proposed, which is shown to recover Earth gravity sedimentation rates well. This work suggests that the effective maximum volume fraction accurately captures interparticle interactions and provides insights into the effect of centrifugation on sedimentation.

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Gels under stress: The origins of delayed collapse

Cited by 27 publications

References 29 publications

Modelling a hydrodynamic instability in freely settling colloidal gels

Modelling a hydrodynamic instability in freely settling colloidal gels

Gels with sense: supramolecular materials that respond to heat, light and sound

Numerical and experimental analysis of the sedimentation of spherical colloidal suspensions under centrifugal force

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