On measuring colloidal volume fractions

Poon, Wilson; Weeks, Eric R.; Royall, C. Patrick

doi:10.1039/c1sm06083j

Cited by 195 publications

(247 citation statements)

References 106 publications

(182 reference statements)

Supporting

Mentioning

243

Contrasting

Order By: Relevance

“…the time an ellipsoid needs to diffuse over the length of its equatorial diameter. The simulated g(r) are in a perfect agreement with the ones obtained numerically, employing the approximate Percus-Yevick (PY) closure to solve the Ornstein-Zernike equation for hard ellipsoids [24] (see Fig. 8).…”

Section: Computer Simulations Fluids Of Hard Ellipsoidssupporting

confidence: 68%

Structural Transition in a Fluid of Spheroids: A Low-Density Vestige of Jamming

et al. 2016

View full text Add to dashboard Cite

A thermodynamically equilibrated fluid of hard spheroids is a simple model of liquid matter. In this model, the coupling between the rotational degrees of freedom of the constituent particles and their translations may be switched off by a continuous deformation of a spheroid of aspect ratio t into a sphere (t ¼ 1). We demonstrate, by experiments, theory, and computer simulations, that dramatic nonanalytic changes in structure and thermodynamics of the fluids take place, as the coupling between rotations and translations is made to vanish. This nonanalyticity, reminiscent of a second-order liquid-liquid phase transition, is not a trivial consequence of the shape of an individual particle. Rather, free volume considerations relate the observed transition to a similar nonanalyticity at t ¼ 1 in structural properties of jammed granular ellipsoids. This observation suggests a deep connection to exist between the physics of jamming and the thermodynamics of simple fluids. DOI: 10.1103/PhysRevLett.116.098001 The thermodynamics of a fluid of simple spheres is wellknown and almost completely understood [1,2]. However, the constituents of real matter are typically nonspherical. Their translational degrees of freedom are coupled to their rotations [3]. A system of spheroids, ellipsoids of revolution, is arguably the simplest model of matter, where such a coupling exists. This model has recently been realized in colloidal and granular matter experiments, providing an important insight onto the local bulk structure of fluids [4,5] and jammed packings [6]. While a very good agreement between experiment and theory has been achieved for the fluids [5,7], these studies dealt with only one specific particle aspect ratio, t ¼ 1.6. The dependence of the fluid structure on the aspect ratio of the constituent particles has not been tested, so that the fundamental role played in these fluids by rotational degrees of freedom remains unknown. The understanding of jammed packings of ellipsoids is incomplete, as well. Many common order metrics are minimized for the, so-called, "maximally random jammed" (MRJ) packings [8]. Yet, it remains unclear, how the various protocols of compression, commonly starting from a fluidlike initial state, explore the available phase space and whether any fundamental physical reason exists for the convergence of many common compression protocols towards packings with densities close to that of the MRJ state [8][9][10][11][12][13].In this work, we study the dependence of the bulk structure in fluids of ellipsoids on the aspect ratio t ¼ a=b of the constituent particles, where a and b are the polar and the equatorial diameters, respectively. We combine experiments, theory, and Monte Carlo (MC) simulations, to explore the fundamental role of the rotational degrees of freedom in these fluids, in the vicinity of the so-called "sphere point" (t ¼ 1), where the coupling between rotations and translations vanishes. We demonstrate that the critical dependence of this coupling on ϵ ≡ jt − 1j, for ϵ → 0, gives rise...

show abstract

Section: Computer Simulations Fluids Of Hard Ellipsoidssupporting

confidence: 68%

Structural Transition in a Fluid of Spheroids: A Low-Density Vestige of Jamming

et al. 2016

View full text Add to dashboard Cite

show abstract

“…We measure this in each data set by counting the numbers of small and large particles observed within a subvolume of the tube, and converting this to the volume fraction using the known particle sizes. Note that 1% uncertainties in the particle radii translate to 3% uncertainties of the volume fraction, and since each particle radius is uncertain, we have an overall systematic volume fraction uncertainty of at least 5% [49].…”

Section: Experimental Methodsmentioning

confidence: 99%

“…V S ∼ a 3 s and likewise for V L , so 1% uncertainties in the particle radii lead to 3% uncertainties of the volume fraction. Since each particle radius is uncertain, we have an overall systematic volume fraction uncertainty of at least 5% [49]. There is also some uncertainty between samples as the different samples are observed to have different number ratios of small and large particles (see Table I), and so errors in small and large particle radii will affect the different volume fraction calculations in different amounts.…”

Section: Appendixmentioning

confidence: 99%

Slow dynamics in cylindrically confined colloidal suspensions

Saklayen

Hunter

Edmond

et al. 2013

AIP Conference Proceedings

Self Cite

View full text Add to dashboard Cite

Abstract. We study bidisperse colloidal suspensions confined within glass microcapillary tubes to model the glass transition in confined cylindrical geometries. We use high speed three-dimensional confocal microscopy to observe particle motions for a wide range of volume fractions and tube radii. Holding volume fraction constant, we find that particles move slower in thinner tubes. The tube walls induce a gradient in particle mobility: particles move substantially slower near the walls. This suggests that the confinement-induced glassiness may be due to an interfacial effect.

show abstract

“…Size polydispersity arises naturally in colloidal systems 20 and is a) mwwang@caltech.edu b) jfbrady@caltech.edu known to affect their phase and packing behaviors 21 and transport properties, [22][23][24] particularly at high density. However, the majority of existing theoretical and simulation works focuses on monodisperse systems.…”

Section: Introductionmentioning

confidence: 99%

Short-time transport properties of bidisperse suspensions and porous media: A Stokesian dynamics study

Wang

Brady

2015

The Journal of Chemical Physics

View full text Add to dashboard Cite

We present a comprehensive computational study of the short-time transport properties of bidisperse hard-sphere colloidal suspensions and the corresponding porous media. Our study covers bidisperse particle size ratios up to 4 and total volume fractions up to and beyond the monodisperse hard-sphere close packing limit. The many-body hydrodynamic interactions are computed using conventional Stokesian Dynamics (SD) via a Monte-Carlo approach. We address suspension properties including the short-time translational and rotational self-diffusivities, the instantaneous sedimentation velocity, the wavenumber-dependent partial hydrodynamic functions, and the high-frequency shear and bulk viscosities and porous media properties including the permeability and the translational and rotational hindered diffusivities. We carefully compare the SD computations with existing theoretical and numerical results. For suspensions, we also explore the range of validity of various approximation schemes, notably the pairwise additive approximations with the Percus-Yevick structural input. We critically assess the strengths and weaknesses of the SD algorithm for various transport properties. For very dense systems, we discuss in detail the interplay between the hydrodynamic interactions and the structures due to the presence of a second species of a different size. C 2015 AIP Publishing LLC. [http://dx

show abstract

On measuring colloidal volume fractions

Cited by 195 publications

References 106 publications

Structural Transition in a Fluid of Spheroids: A Low-Density Vestige of Jamming

Structural Transition in a Fluid of Spheroids: A Low-Density Vestige of Jamming

Slow dynamics in cylindrically confined colloidal suspensions

Short-time transport properties of bidisperse suspensions and porous media: A Stokesian dynamics study

Contact Info

Product

Resources

About