Structural origins of dynamical heterogeneity in colloidal gels

Dibble, Clare J.; Kogan, Michael; Solomon, Michael J.

doi:10.1103/physreve.77.050401

Cited by 56 publications

(67 citation statements)

References 25 publications

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“…3,6,19,20 Similar results have been reported for weakly attractive systems. 7,8 This agrees with numerical and experimental findings for molecular glass formers 11,12,21,22 and grains. [13][14][15][16] Although the debate is still very active on whether or not the glass and the jamming transitions coincide in thermal hard spheres, [23][24][25][26][27][28] and thus on how far the regime where x grows may extend, it is unlikely that significantly larger correlation lengths may be measured in the supercooled regime.…”

Section: -17supporting

confidence: 89%

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Ultra-long range correlations of the dynamics of jammed soft matter

et al. 2010

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We use photon correlation imaging, a recently introduced space-resolved dynamic light scattering method, to investigate the spatial correlation of the dynamics of a variety of jammed and glassy soft materials. Strikingly, we find that in deeply jammed soft materials spatial correlations of the dynamics are quite generally ultra-long ranged, extending up to the system size, orders of magnitude larger than any relevant structural length scale, such as the particle size, or the mesh size for colloidal gel systems. This has to be contrasted with the case of molecular, colloidal and granular ''supercooled'' fluids, where spatial correlations of the dynamics extend over a few particles at most. Our findings suggest that ultra long range spatial correlations in the dynamics of a system are directly related to the origin of elasticity. While solid-like systems with entropic elasticity exhibit very moderate correlations, systems with enthalpic elasticity exhibit ultra-long range correlations due to the effective transmission of strains throughout the contact network.

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Section: -17supporting

confidence: 89%

“…1 Work in the past decade has shown that a feature shared by most of these systems is the heterogeneous character of their slow dynamics, which result from rearrangements that are localized in space and intermittent in time, [1][2][3][4][5][6][7][8][9][10] in analogy with molecular glass formers 11,12 and driven athermal grains and foams.…”

Section: Introductionmentioning

confidence: 99%

Ultra-long range correlations of the dynamics of jammed soft matter

et al. 2010

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“…As the attraction strength increases we see a transition from a low, but finite, value of Z in the liquid state, and a rapid growth in the coordination number as the sample transforms into an aggregated colloidal gel (Fig. 1d) [5]. However, the average coordination number does not provide insight into the strong intrinsic heterogeneity in the microscture of colloidal gels, which becomes visible in a computer-generated representation of our experimental system in which the particles are color-coded according to their instantaneous value of Z (Fig.…”

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confidence: 99%

“…These colloidal gels are non-equilibrium solids, kinetically arrested en route to their equilibrium state of solidliquid coexistence [3]. Such particle gels are characterized by strong heterogeneity in their local connectivity, mesoscopic structure and their dynamics and mechanics [4][5][6][7]. The microstructure and internal dynamics of colloidal gels can be directly observed with microscopy techniques at the single-particle level.…”

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confidence: 99%

Linking Particle Dynamics to Local Connectivity in Colloidal Gels

et al. 2017

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Colloidal gels are a prototypical example of a heterogeneous network solid whose complex properties are governed by thermally-activated dynamics. In this Letter we experimentally establish the connection between the intermittent dynamics of individual particles and their local connectivity. We interpret our experiments with a model that describes single-particle dynamics based on highly cooperative thermal debonding. The model, in quantitative agreement with experiments, provides a microscopic picture for the structural origin of dynamical heterogeneity in colloidal gels and sheds new light on the link between structure and the complex mechanics of these heterogeneous solids.Attractive interactions can drive a dilute colloidal suspension towards a solid state formed by a samplespanning and mechanically-rigid particle network [1,2]. These colloidal gels are non-equilibrium solids, kinetically arrested en route to their equilibrium state of solidliquid coexistence [3]. Such particle gels are characterized by strong heterogeneity in their local connectivity, mesoscopic structure and their dynamics and mechanics [4][5][6][7]. The microstructure and internal dynamics of colloidal gels can be directly observed with microscopy techniques at the single-particle level. As a consequence, it forms an interesting testing ground to explore the complex and length-scale dependent mechanics of heterogeneous solids. Colloidal gels derive their mechanical rigidity from physically bonded gel strands and nodes that form a percolating elastic network. The linear elasticity of gels is governed by the mechanics of the network architecture and its thermal fluctuations [8,9]. By contrast, the gradual aging of gels to a denser state [1,10] and their non-linear response to applied stresses [11,12], is governed by events occuring at the the much smaller length scale of individual particles. Since the bonds between the particles are typically weak, single particles can debond from strands in the gel by thermally-activated bond breaking [13]. On longer time scales, this result in the gradual restructuration of the gel network, causing it to coarsen, age and relax internal stresses that are built up during gelation [14]. Moreover, thermal-activation at the single particle level plays a crucial role in processes of fatigue that preempt stress-induced failure of the gel network [11]. To date, quantitative descriptions of these thermally-activated phenomena have relied on mean-field approximations [13]. Yet, the inhomogeneity in local coordination that is intrinsic to gels, must play a large role in the intermittent debonding dynamics that are at the origin of this complex non-linear behavior. As a result, linking the structure of colloidal gels to their non-linear mechanics has remained challenging, in particular as the relationship between local connectivity and thermallyactivated dynamics of single particles is not clearly established.In this letter we explore the connection between the local connectivity and intermittent bonding-debonding dy...

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“…Particle-tracking algorithms 23 applied to two-or three-dimensional time series of confocal micrographs yield the trajectories of all visible particles. As a result, the combination of confocal microscopy and particle-tracking has been applied to study the phase behavior, structure, and dynamics of colloidal suspensions, including ordered crystals [24][25][26][27] and disordered glasses [28][29][30][31] and gels [32][33][34][35] .…”

Section: Introductionmentioning

confidence: 99%

Confocal Imaging of Confined Quiescent and Flowing Colloid-polymer Mixtures

Pandey

Spannuth

Conrad

2014

JoVE

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The behavior of confined colloidal suspensions with attractive interparticle interactions is critical to the rational design of materials for directed assembly [1][2][3] , drug delivery 4 , improved hydrocarbon recovery [5][6][7] , and flowable electrodes for energy storage 8 . Suspensions containing fluorescent colloids and non-adsorbing polymers are appealing model systems, as the ratio of the polymer radius of gyration to the particle radius and concentration of polymer control the range and strength of the interparticle attraction, respectively. By tuning the polymer properties and the volume fraction of the colloids, colloid fluids, fluids of clusters, gels, crystals, and glasses can be obtained 9 . Confocal microscopy, a variant of fluorescence microscopy, allows an optically transparent and fluorescent sample to be imaged with high spatial and temporal resolution in three dimensions. In this technique, a small pinhole or slit blocks the emitted fluorescent light from regions of the sample that are outside the focal volume of the microscope optical system. As a result, only a thin section of the sample in the focal plane is imaged. This technique is particularly well suited to probe the structure and dynamics in dense colloidal suspensions at the single-particle scale: the particles are large enough to be resolved using visible light and diffuse slowly enough to be captured at typical scan speeds of commercial confocal systems 10 . Improvements in scan speeds and analysis algorithms have also enabled quantitative confocal imaging of flowing suspensions [11][12][13][14][15][16]37 . In this paper, we demonstrate confocal microscopy experiments to probe the confined phase behavior and flow properties of colloid-polymer mixtures. We first prepare colloid-polymer mixtures that are density-and refractive-index matched. Next, we report a standard protocol for imaging quiescent dense colloid-polymer mixtures under varying confinement in thin wedge-shaped cells. Finally, we demonstrate a protocol for imaging colloid-polymer mixtures during microchannel flow. Video LinkThe video component of this article can be found at

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Structural origins of dynamical heterogeneity in colloidal gels

Cited by 56 publications

References 25 publications

Ultra-long range correlations of the dynamics of jammed soft matter

Ultra-long range correlations of the dynamics of jammed soft matter

Linking Particle Dynamics to Local Connectivity in Colloidal Gels

Confocal Imaging of Confined Quiescent and Flowing Colloid-polymer Mixtures

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