A combination of analytical calculations and Monte Carlo simulations is used to find the ground-state structures in monodisperse ferrofluid monolayers under the influence of an external magnetic field. We study two different regimes, where (i) the direction of an external field is perpendicular to t…

[Phys. Rev. E 86, 061408] Published Tue Dec 18, 2012

The fracture mechanics was usually employed to explain the crack propagation in the deposition produced by drying colloidal suspension. However, more complex than conventional fracture, those cracks periodically distribute and make up a unique pattern. Inspired by the concept of spinodal decomposi…

[Phys. Rev. E 86, 061406] Published Mon Dec 17, 2012

Despite their lack of thermodynamical stability, nanoemulsions can show a remarkable degree of kinetic stability. Among the various different preparation methods the phase-inversion concentration method is particularly interesting as it occurs spontaneously. Here we investigate such a system compose…

[Phys. Rev. E 86, 061407] Published Mon Dec 17, 2012

An algorithm is developed for numerical simulation of coupled stochastic dynamics of magnetic moment and magnetic anisotropy axis of a nanoparticle. Time-correlation functions of the magnetic moment and its components longitudinal and transverse to the magnetic anisotropy axis are calculated by aver…

[Phys. Rev. E 86, 061405] Published Fri Dec 14, 2012

A dielectric measurement method has been proposed to apply to the study of the microstructure of electrorheological (ER) fluids. To test our measurement method the dielectric permittivity increment caused by pair and chain formation was measured in dilute Brownian ER fluids composed of silicone oil …

[Phys. Rev. E 86, 061403] Published Tue Dec 11, 2012

The deterministic Landau-Lifshitz-Gilbert equation has been used to investigate the nonlinear dynamics of magnetization and the specific power loss in magnetic nanoparticles with uniaxial anisotropy driven by a rotating magnetic field, generalizing the results obtained for the isotropic case found b…

[Phys. Rev. E 86, 061404] Published Tue Dec 11, 2012

We report results from a computer simulation study on the rotational ratchet effect in systems of magnetic particles interacting via dipolar interactions. The ratchet effect consists of directed rotations of the particles in an oscillating magnetic field, which lacks a net rotating component. Our in…

[Phys. Rev. E 86, 061402] Published Thu Dec 06, 2012

The dynamic shape relaxation of the two-layer vesicle is calculated. In addition to the undulation relaxation where the two bilayers move in the same direction, the squeezing mode appears when the gap between the two bilayers is small. At a large gap, the inner vesicle relaxes much faster, whereas t…

[Phys. Rev. E 86, 061401] Published Wed Dec 05, 2012

We investigate a driven, one-dimensional system of colloidal particles in a periodically corrugated narrow channel subject to a time-delayed feedback control. Our goal is to identify conditions under which the control induces oscillatory, time-periodic states. The investigations are based on the Fok…

[Phys. Rev. E 86, 051405] Published Fri Nov 30, 2012

The dynamical behavior of single-component two-dimensional colloidal crystals confined in a slit geometry is studied by Langevin dynamics simulation of a simple model. The colloids are modeled as pointlike particles, interacting with the repulsive part of the Lennard-Jones potential, and the fluid m…

[Phys. Rev. E 86, 051404] Published Mon Nov 26, 2012

The rate of rapid Brownian coagulation is investigated for dispersions of spherical particles with particle volume fractions ranging from ${\varphi }_{\mathrm{p}}=0.003$ to $0.1$ by the direct numerical simulation method. This method explicitly considers hydrodynamic interactions (HIs) between particles by simultaneously so…

[Phys. Rev. E 86, 051403] Published Wed Nov 14, 2012

Using Langevin dynamics simulations we investigate the self-assembly of colloidal particles in two dimensions interacting via an isotropic potential, which comprises both a hard-core repulsion and an additional softened square-well potential of controllable width $\alpha$. In dilute concentrations, the par…

[Phys. Rev. E 86, 051402] Published Mon Nov 12, 2012

Experimental and theoretical studies were carried out to investigate the problem of magnetophoresis in a thin layer of concentrated magnetic fluids, concerning the aspect of particle aggregation. A heuristic theoretical model, describing diffusion fluxes of individual and aggregated particles, is su…

[Phys. Rev. E 86, 051401] Published Mon Nov 05, 2012

We report the results of studies of the collective and pair diffusion coefficients of particles in two quasi-one-dimensional geometries: straight 2-mm-long channels and rings with radii between 3 and 35 μm. We find a contribution to the packing fraction dependence of the collective diffusion coeffic…

[Phys. Rev. E 86, 041402] Published Wed Oct 31, 2012

We study the rotational diffusion of aging Laponite suspensions for a wide range of concentrations using depolarized dynamic light scattering. The measured orientational correlation functions undergo an ergodic to nonergodic transition that is characterized by a concentration-dependent ergodicity-br…

[Phys. Rev. E 86, 041401] Published Fri Oct 05, 2012

We investigate the response of a dense monodisperse quasi-two-dimensional colloid suspension when a particle is dragged by a constant velocity optical trap. Consistent with microrheological studies of other geometries, the perturbation induces a leading density wave and trailing wake. We also use a …

[Phys. Rev. E 86, 031403] Published Fri Sep 28, 2012

Space-filling assemblies of athermal hydrophobic particles floating at an air-water interface, called particle rafts, are shown to undergo an unusual phase transition between two amorphous states, i.e., a low density “less-rigid” state and a high density “more-rigid” state, as a function of particul…

[Phys. Rev. E 86, 031402] Published Wed Sep 26, 2012

According to Harada and Sasa [Phys. Rev. Lett. 95, 130602 (2005)], heat production generated in a nonequilibrium steady state can be inferred from measuring response and correlation functions. In many colloidal systems, however, it is a nontrivial task to determine response functions, whereas detail…

[Phys. Rev. E 86, 030401(R)] Published Thu Sep 20, 2012

We study the motion of a ferromagnetic helical nanostructure under the action of a rotating magnetic field. A variety of dynamical configurations were observed that depended strongly on the direction of magnetization and the geometrical parameters, which were also confirmed by a theoretical model, b…

[Phys. Rev. E 86, 031401] Published Fri Sep 14, 2012

Using computer simulations, we investigate hysteresis loops and return-point memory for artificial square and kagome spin ice systems by cycling an applied bias force and comparing microscopic effective spin configurations throughout the hysteresis cycle. Return-point memory loss is caused by motion…

[Phys. Rev. E 86, 021406] Published Mon Aug 27, 2012

We implement molecular dynamics simulations in canonical ensemble to study the effect of confinement on a two-dimensional crystal of point particles interacting with an inverse power law potential proportional to $r^{-12}$ in a narrow channel. This system can describe colloidal particles at the air-water…

[Phys. Rev. E 86, 021405] Published Thu Aug 23, 2012

In materials science the phase-field crystal approach has become popular to model crystallization processes. Phase-field crystal models are in essence Landau-Ginzburg-type models, which should be derivable from the underlying microscopic description of the system in question. We present a study on c…

[Phys. Rev. E 86, 021404] Published Wed Aug 22, 2012

We provide a detailed derivation of a recently developed first-principles approach to calculating averages in systems of interacting, spherical Brownian particles under time-dependent flow. Although we restrict ourselves to flows which are both homogeneous and incompressible, the time dependence and…

[Phys. Rev. E 86, 021403] Published Mon Aug 13, 2012

In this paper we report on bubble growth rates and on the statistics of bubble topology for the coarsening of a dry foam contained in the narrow gap between two hemispheres. By contrast with coarsening in flat space, where six-sided bubbles neither grow nor shrink, we observe that six-sided bubbles …

[Phys. Rev. E 86, 021402] Published Mon Aug 06, 2012

The interaction of two diffusing particles is strongly influenced by their hydrodynamic coupling. At a tracking rate of 10 kHz we are able to measure the 3D trajectories of two colloidal spheres in a single harmonic potential, which was generated by scanning line optical tweezers. This common potent…

[Phys. Rev. E 86, 021401] Published Wed Aug 01, 2012

In this paper we present results of extensive Monte Carlo simulations of diffusion-limited aggregation (DLA) with a seed placed on an attractive plane as a simple model in connection with the electrical double layers. We compute the fractal dimension of the aggregated patterns as a function of the a…

[Phys. Rev. E 86, 011407] Published Fri Jul 27, 2012

Interactions between two vesicles in an imposed linear shear flow are studied theoretically, in the limit of almost spherical vesicles, with a large intervesicle distance, in a strong flow, with a large inner to outer viscosity ratio. This allows to derive a system of ordinary equations describing t…

[Phys. Rev. E 86, 011408] Published Fri Jul 27, 2012

We discuss a schematic model of mode-coupling theory for force-driven active nonlinear microrheology, where a single probe particle is pulled by a constant external force through a dense host medium. The model exhibits both a glass transition for the host and a force-induced delocalization transitio…

[Phys. Rev. E 86, 011406] Published Mon Jul 23, 2012

Using kinetic Monte Carlo simulation, we model gas-liquid spinodal decomposition in a size-polydisperse square well fluid, representing a “near-monodisperse” colloidal dispersion. We find that fractionation (demixing) of particle sizes between the phases begins asserting itself shortly after the ons…

[Phys. Rev. E 86, 011405] Published Thu Jul 19, 2012

If a suspension of magnetic micrometer-sized and nanosized particles is subjected to a homogeneous magnetic field, the nanoparticles are attracted to the microparticles and form thick anisotropic halos (clouds) around them. Such clouds can hinder the approach of microparticles and result in effectiv…

[Phys. Rev. E 86, 011404] Published Fri Jul 13, 2012

In colloidal suspensions, self-organization processes can be easily fueled by external fields. Here we consider monolayers of particles with permanent dipole moments that are driven by rotating external fields. In recent experiments, it has been shown that the particles in such systems self-organize…

[Phys. Rev. E 86, 011402] Published Mon Jul 09, 2012

We report on the diffusion of purely repulsive and freely rotating colloidal rods in the isotropic, nematic, and smectic liquid crystal phases to probe the agreement between Brownian and Monte Carlo dynamics under the most general conditions. By properly rescaling the Monte Carlo time step, being re…

[Phys. Rev. E 86, 011403] Published Mon Jul 09, 2012

We report the experimental observation of anisotropic diffusion of polystyrene particles immersed in a lyotropic liquid crystal with two different anchoring conditions. Diffusion is shown to obey the Stokes-Einstein law for particle diameters ranging from 190 nm up to 2 $\mu$m. In the case of prolate mi…

[Phys. Rev. E 86, 010401(R)] Published Thu Jul 05, 2012

Study of energy transport velocity of light is an effective background for slow, fast, and diffuse light and exhibits the photonic property of the material. We report a theoretical analysis of magnetic field dependent resonant behavior in forward-backward anisotropy factor, light diffusion constant,…

[Phys. Rev. E 86, 011401] Published Thu Jul 05, 2012

A modified phase-field crystal model in which the free energy may be minimized by an order parameter profile having isolated bumps is investigated. The phase diagram is calculated in one and two dimensions and we locate the regions where modulated and uniform phases are formed and also regions where…

[Phys. Rev. E 85, 061408] Published Thu Jun 21, 2012

We present a study on connectivity percolation in suspensions of hard platelets by means of Monte Carlo simulation. We interpret our results using a contact-volume argument based on an effective single-particle cell model. It is commonly assumed that the percolation threshold of anisotropic objects …

[Phys. Rev. E 85, 061407] Published Wed Jun 20, 2012

Langevin dynamics simulations are used to study the effect of shear on a two-dimensional colloidal crystal (with implicit solvent) confined by structured parallel walls. When walls are sheared very slowly, only two or three crystalline layers next to the walls move along with them, while the inner l…

[Phys. Rev. E 85, 061406] Published Mon Jun 18, 2012

Two important assumptions are often made in the analysis of molecular self-assembly at equilibrium, viz., that sequential is preferred to random aggregation and that the equilibrium constants at each stage of aggregation are equal, though both assumptions have not been justified strictly. In the pre…

[Phys. Rev. E 85, 061405] Published Tue Jun 12, 2012

In the lateral confinement of a flat microfluidic channel, monodisperse emulsion droplets spontaneously self-organize in a variety of topologically different packings. The explicit construction of mechanically equilibrated arrangements of effectively two-dimensional congruent droplet shapes reveals …

[Phys. Rev. E 85, 061403] Published Wed Jun 06, 2012

Colloidosomes are created in the laboratory from a Pickering emulsion of water droplets in oil. The colloidosomes have approximately the same diameter and by choosing (hairy) particles of different diameters it is possible to control the particle density on the droplets. The experiment is performed …

[Phys. Rev. E 85, 061404] Published Wed Jun 06, 2012

The diffusive growth rate of a polyhedral cell in dry three-dimensional foams depends on details of shape beyond cell topology, in contrast to the situation in two dimensions, where, by von Neumann's law, the growth rate depends only on the number of cell edges. We analyze the dependence of the inst…

[Phys. Rev. E 85, 061401] Published Fri Jun 01, 2012

We experimentally study the motion of optically driven colloidal particles on a circular path by varying their number $N$. Although an identical driving force is applied to each particle, their equally spaced configuration is hydrodynamically unstable, and a doublet configuration is spontaneously form…

[Phys. Rev. E 85, 061402] Published Fri Jun 01, 2012

The effect of adding charged nonadsorbing polymers to electrostatically structured suspensions of charged liposomes has been experimentally studied by means of light scattering techniques. The static structure factor of the mixtures is analyzed using two polymers of different sizes. As the polymer c…

[Phys. Rev. E 85, 051405] Published Tue May 29, 2012

In this contribution, the yield behavior of a strongly flocculated colloidal structure subjected to a tensile-bending load is micromechanically modeled. The yielding of a cluster is assumed to be triggered by the failure of one bond (critical bond) and accompanied by massive breakage of further bond…

[Phys. Rev. E 85, 051406] Published Tue May 29, 2012

We study the structure and phonon spectrum of a two-dimensional bilayer system of classical charged dipoles oriented perpendicular to the plane of the layers for equal density in each layer. This system can be tuned through six different crystalline phases by changing the interlayer separation or th…

[Phys. Rev. E 85, 051404] Published Thu May 24, 2012

We analyze the geometric structure and mechanical stability of a complete set of isostatic and hyperstatic sphere packings obtained via exact enumeration. The number of nonisomorphic isostatic packings grows exponentially with the number of spheres $N$, and their diversity of structure and symmetry in…

[Phys. Rev. E 85, 051403] Published Tue May 22, 2012

Grand canonical Monte Carlo and histogram reweighting techniques are used to study the fluid-phase behavior of an athermal system of colloids and nonadsorbing polymers on a fine lattice in the “protein limit,” where polymer dimensions exceed those of the colloids. The main parameters are the chains'…

[Phys. Rev. E 85, 051402] Published Fri May 11, 2012

We examine the statics and dynamics of particles with repulsive Yukawa interactions in the presence of a two-dimensional triangular substrate for fillings of up to 12 particles per potential minimum. We term the ordered states Yukawa cluster crystals and show that they are distinct from the colloida…

[Phys. Rev. E 85, 051401] Published Wed May 02, 2012

The dynamics of an induced lamellar microemulsion adjacent to a planar hydrophilic surface (45 ns) were found to be three times faster compared to the bicontinuous bulk structure (133 ns). For these investigations the grazing incidence technique for neutron spin echo spectroscopy has been developed …

[Phys. Rev. E 85, 041408] Published Mon Apr 30, 2012

Competitive adsorption of counterions of multiple species to charged surfaces is studied by a size-effect-included mean-field theory and Monte Carlo (MC) simulations. The mean-field electrostatic free-energy functional of ionic concentrations, constrained by Poisson's equation, is numerically minimi…

[Phys. Rev. E 85, 041406] Published Thu Apr 26, 2012

Through a combination of theory, numerical simulation, and experiment, we investigate the motion of magnetic beads on the surface of a magnetic ratchet driven by multifrequency fields. Here, we focus on the influence of static forcing terms, which were not included in previous models, and we derive …

[Phys. Rev. E 85, 041407] Published Thu Apr 26, 2012

The ferrofluid emulsion, made of kerosene-based ferrofluid droplets suspended in nonmiscible aviation oil, demonstrates experimentally the nonmonotonic dependence of the effective magnetic permeability as a function of the uniform static magnetic field. In weak fields the emulsion permeability rapid…

[Phys. Rev. E 85, 041405] Published Mon Apr 23, 2012

We report a universal large deviation behavior of spatially averaged global injected power just before the rejuvenation of the jammed state formed by an aging suspension of laponite clay under an applied stress. The probability distribution function (PDF) of these entropy consuming strongly non-Gaus…

[Phys. Rev. E 85, 041404] Published Thu Apr 19, 2012

We investigate the nonlinear rheology of dilute, depletion-induced colloidal gels and report that these systems yield via a two-step process. We propose the two yield points to be associated with interparticle bond rotation and bond breakage, respectively. These distinct yielding mechanisms lead to …

[Phys. Rev. E 85, 041403] Published Mon Apr 16, 2012

We have experimentally investigated the interactions between floating magnetic spheres which are submitted to a vertical magnetic field, ensuring a tunable repulsion, while capillary forces induce attraction. We emphasize the complex arrangements of floating bodies. The equilibrium distance between …

[Phys. Rev. E 85, 041402] Published Fri Apr 13, 2012

We study a dense colloidal suspension confined between two quasiparallel glass plates as a model system for a supercooled liquid in confined geometries. We directly observe the three-dimensional Brownian motion of the colloidal particles using laser scanning confocal microscopy. The particles form d…

[Phys. Rev. E 85, 041401] Published Wed Apr 11, 2012

A mixture of hard-sphere particles and model emulsion droplets is studied with a Brownian dynamics simulation. We find that the addition of nonwetting emulsion droplets to a suspension of pure hard spheres can lead to both gas-liquid and fluid-solid phase separations. Furthermore, we find a stable f…

[Phys. Rev. E 85, 040401(R)] Published Mon Apr 02, 2012

The nonaffine motion of particles is central to the relaxation and flow of glasses. It is usually assumed in plasticity theories that nonaffine rearrangements are localized and uncorrelated. Here we present evidence that this assumption may not hold. We investigate and compare systematically differe…

[Phys. Rev. E 85, 031402] Published Thu Mar 29, 2012

We present a small and compact two-color cross-correlation light-scattering setup designed to study the structure and dynamics of colloidal suspensions in the regime of considerable turbidity. Using a homemade concentric four-arm goniometer, combined with fiber-optical illumination and detection dev…

[Phys. Rev. E 85, 031401] Published Tue Mar 13, 2012

We examine the branch structure of radial diffusion-limited aggregation (DLA) clusters for evidence of multifractality. The lacunarity of DLA clusters is measured and the generalized dimensions $D\left(q\right)$ of their mass distribution is estimated using the sandbox method. We find that the global $n$-fold symm…

[Phys. Rev. E 85, 021407] Published Mon Feb 27, 2012

We simulate the response of a particle-stabilized emulsion droplet in an external force field, such as gravity, acting equally on all $N$ particles. We show that the field strength required for breakup (at fixed initial area fraction) decreases markedly with droplet size, because the forces act cumula…

[Phys. Rev. E 85, 020403(R)] Published Fri Feb 24, 2012

We report computer simulation studies of the kinetics of ordering of a two-dimensional system of particles on a template with a one-dimensional periodic pattern. In equilibrium, one obtains a reentrant liquid-solid-liquid phase transition as the strength of the substrate potential is varied. We show…

[Phys. Rev. E 85, 020402(R)] Published Tue Feb 21, 2012

Recently the Brownian dynamics of self-propelled (active) rodlike particles was explored to model the motion of colloidal microswimmers, catalytically driven nanorods, and bacteria. Here we generalize this description to biaxial particles with arbitrary shape and derive the corresponding Langevin eq…

[Phys. Rev. E 85, 021406] Published Tue Feb 21, 2012

The propulsion velocity of active colloids that asymmetrically catalyze a chemical reaction is probed experimentally as a function of their sizes. It is found that over the experimentally accessible range, the velocity decays as a function of size, with a rate that is compatible with an inverse size…

[Phys. Rev. E 85, 020401(R)] Published Wed Feb 15, 2012

We use confocal microscopy to study the three-dimensional (3D) structure of colloidal crystals formed by poly($N$-isopropylacrylamide)-co-(acrylic acid) microgels of diameter 1.0–1.5 $\mu$m. The confocal images are tracked to locate particle positions in 3D, which are used to compute pair-correlation func…

[Phys. Rev. E 85, 021405] Published Fri Feb 10, 2012

A vertical force applied to each of two colloids, trapped at a liquid-air interface, induces their logarithmic pairwise attraction. I recently showed [Phys. Rev. E 79, 011407 (2009)] that in clusters of size $R$ much larger than the capillary length $\lambda$, the attraction changes to that of a power law and…

[Phys. Rev. E 85, 021403] Published Tue Feb 07, 2012

Metastable gels formed by weakly attractive colloidal particles display a distinctive two-stage time-dependent settling behavior under their own weight. Initially, a space-spanning network is formed that, for a characteristic time, which we define as the lag time ${\tau }_{\mathrm{d}}$, resists compaction. This solidli…

[Phys. Rev. E 85, 021404] Published Tue Feb 07, 2012

We report x-ray photon correlation spectroscopy measurements of advective and diffusive dynamics in a dispersion of colloidal particles subjected to homogeneous shear flow in a rotating-disk shear cell. Intensity autocorrelation functions from scattering data collected using homodyne detection respo…

[Phys. Rev. E 85, 021402] Published Fri Feb 03, 2012

Shock wave propagation in multiphase media is typically dominated by the relative compressibility of the two components of the mixture. The difference in the compressibility of the components results in a shock-induced variation in the effective volume fraction of the suspension tending toward the r…

[Phys. Rev. E 85, 021401] Published Thu Feb 02, 2012

A fundamental assumption of the dynamical density functional theory (DDFT) of colloidal systems is that a grand-canonical free-energy functional may be employed to generate the thermodynamic driving forces. Using one-dimensional hard rods as a model system, we analyze the validity of this key assump…

[Phys. Rev. E 85, 011404] Published Fri Jan 27, 2012

Phase transitions of aqueous colloidal dispersions of charged platelike particles of niobate nanosheets were investigated as a function of the aspect ratio ($r_{\mathrm{asp}}$) and particle volume concentration (${\phi }_{\mathrm{p}}$) by means of small-angle neutron scattering and small-angle x-ray scattering. The results elucidate…

[Phys. Rev. E 85, 011403] Published Wed Jan 18, 2012

The dynamic behavior of a hard-sphere colloidal suspension was studied by x-ray photon correlation spectroscopy and small-angle x-ray scattering over a wide range of particle volume fractions. The short-time mobility of the particles was found to be smaller than that of free particles even at relati…

[Phys. Rev. E 85, 011402] Published Fri Jan 13, 2012

A dense mixture of granules and liquid often shows a severe shear thickening and is called a dilatant fluid. We construct a fluid dynamics model for the dilatant fluid by introducing a phenomenological state variable for a local state of dispersed particles. With simple assumptions for an equation o…

[Phys. Rev. E 85, 011401] Published Wed Jan 11, 2012

We independently determine the bulk and shear moduli of compressed microgel suspensions and the bulk modulus of individual microgel particles and find that the elastic behavior of the suspension reflects the degree of compression of the particles. This feature, which is distinct from other soft mate…

[Phys. Rev. E 84, 060402(R)] Published Thu Dec 08, 2011

We consider a nanodimer in solution with asymmetric thermal properties that shows self-propelled motion. One monomer of the nanodimer can be heated to a fixed temperature producing a radially symmetric temperature gradient. The thermophoretic properties of the second monomer produce then a propulsio…

[Phys. Rev. E 84, 061401] Published Tue Dec 06, 2011

Cornstarch suspensions exhibit remarkable behavior. Here, we present two unexpected observations for a sphere settling in such a suspension: In the bulk of the liquid the velocity of the sphere oscillates around a terminal value, without damping. Near the bottom the sphere comes to a full stop, but …

[Phys. Rev. E 84, 060401(R)] Published Thu Dec 01, 2011

The intrinsic viscosity of a dilute dispersion of rigid rods is studied using a recently developed direct numerical simulation (DNS) method for particle dispersions. A reentrant transition from shear-thinning behavior to the second Newtonian regime is successfully reproduced in the present DNS resul…

[Phys. Rev. E 84, 051404] Published Wed Nov 16, 2011

We use optical microscopy to measure the rotational Brownian motion of polygonal platelets that are dispersed in a liquid and confined by depletion attractions near a wall. The depletion attraction inhibits out-of-plane translational and rotational Brownian fluctuations, thereby facilitating in-plan…

[Phys. Rev. E 84, 051405] Published Wed Nov 16, 2011

We formulate a density functional theory that describes the phase behavior of hard rods and depleting polymers, as realized in recent experiments on suspensions of fd virus and nonadsorbing polymer. The theory predicts the relative stability of nematic droplets, stacked smectic columns, and a recent…

[Phys. Rev. E 84, 051402] Published Thu Nov 03, 2011

We observe a Fano-like resonance in a magnetically polarizable nanofluid. Under an external magnetic field, the transmittance spectrum of a ferrofluid emulsion containing droplet size of ∼220 nm shows an enhanced peak with a Fano-like profile, which is attributed to a localized waveguide resonance f…

[Phys. Rev. E 84, 051403] Published Thu Nov 03, 2011

We calculate the ion and composition distributions around colloid particles in an aqueous mixture, accounting for preferential adsorption, electrostatic interaction, selective solvation among ions and polar molecules, and composition-dependent ionization. On the colloid surface, we predict a precipi…

[Phys. Rev. E 84, 051401] Published Wed Nov 02, 2011

The hydrodynamic properties of rigid fractal aggregates have been investigated by considering their motion in shear flow in the Stokesian dynamics approach. Due to the high fluid viscosity and small particle inertia of colloidal systems, the total force and torque applied to the aggregate reach equi…

[Phys. Rev. E 84, 041405] Published Mon Oct 31, 2011

We show how attractive interactions dramatically influence emulsion rheology. Unlike the repulsive case, attractive emulsions below random close packing, ${\phi }_{\text{RCP}}$, can form soft gel-like elastic solids. However, above ${\phi }_{\text{RCP}}$, attractive and repulsive emulsions have similar elasticities. Such compressed at…

[Phys. Rev. E 84, 041404] Published Tue Oct 25, 2011

We report the results of a study of single-particle diffusion in dense colloid fluids confined in a ribbon channel geometry that is intermediate between quasione dimensional (q1D) and quasitwo dimensional (q2D). This paper complements a previous paper about pair diffusion in the same system [Phys. R…

[Phys. Rev. E 84, 041403] Published Tue Oct 18, 2011

We present a physically intuitive model of ice-lens formation and growth during the freezing of soils and other dense, particulate suspensions. Motivated by experimental evidence, we consider the growth of an ice-filled crack in a freezing soil. At low temperatures, ice in the crack exerts large pre…

[Phys. Rev. E 84, 041402] Published Fri Oct 14, 2011

We present a new analytical approach to the strong electrostatic coupling regime (SC) that can be achieved equivalently at low temperatures, high charges, low dielectric permittivity, etc. Two geometries are analyzed in detail: one charged wall first, and then two parallel walls at small distances t…

[Phys. Rev. E 84, 041401] Published Mon Oct 10, 2011

We investigated the effects of particle shape on shear thickening in densely packed suspensions. Rods of different aspect ratios and nonconvex hooked rods were fabricated. Viscosity curves and normal stresses were measured using a rheometer for a wide range of packing fractions for each shape. Suspe…

[Phys. Rev. E 84, 031408] Published Wed Sep 28, 2011

Tailoring rheological properties of colloidal suspensions with the adsorption of polyelectrolyte multilayers (PEMs) is based on the idea of controlling macroscopic mechanical properties by modifying the particle surface in a reproducible and well-understood manner. With layer-by-layer self-assembly,…

[Phys. Rev. E 84, 031407] Published Tue Sep 27, 2011

By use of optical tweezers we explicitly measure the electrostatic and hydrodynamic forces that determine the electrophoretic mobility of a charged colloidal particle. We test the ansatz of O'Brien and White [J. Chem. Soc. Faraday II 74, 1607 (1978)] that the electrostatically and hydrodynamically c…

[Phys. Rev. E 84, 032401] Published Mon Sep 26, 2011

We present a model that describes the drying of solutions and colloidal dispersions from droplets confined between two circular plates. This confined geometry, proposed by Clément and Leng [Langmuir 20, 6538 (2004)], casts a perfect control of the evaporation conditions, and thus also of the concent…

[Phys. Rev. E 84, 031406] Published Tue Sep 20, 2011

Nonequilibrium structure formation and dynamics in suspensions of superparamagnetic colloids driven by an external rotating magnetic field are studied by particle-based mesoscale hydrodynamics simulations in confined geometry. We address the fundamental question how the rotation of the colloids abou…

[Phys. Rev. E 84, 031404] Published Mon Sep 19, 2011

The influence of an ellipsoid on the angular order of two-dimensional classical clusters is investigated through Brownian dynamics simulations. We found the following: (1) The presence of an ellipsoid does not influence the start of the angular melting, but reduces the rate at which the inner rings …

[Phys. Rev. E 84, 031405] Published Mon Sep 19, 2011

We study the behavior of a yield-stress fluid following the impact of a vertically falling sphere. Since the impact produces shear stresses larger than the yield stress, the material in the vicinity of the impact becomes fluidized. The sphere entrains air when it enters the fluid, and the resulting …

[Phys. Rev. E 84, 031403] Published Fri Sep 16, 2011

We use confocal microscopy to study the compressibility of a random-close-packed sample of colloidal particles. To do this, we introduce an algorithm to estimate the size of each particle. Taking into account their sizes, we compute the compressibility of the sample as a function of wave vector $q$, a…

[Phys. Rev. E 84, 030401(R)] Published Mon Sep 12, 2011

The anisotropy of magnetic emulsions induced by simultaneously acting electric and magnetic fields is theoretically and experimentally investigated. Due to the anisotropy, the electric conductivity and magnetic permeability of a magnetic emulsion are no longer scalar coefficients, but are tensors. T…

[Phys. Rev. E 84, 031402] Published Wed Sep 07, 2011

The effective capillary interaction potentials for small colloidal particles trapped at the surface of liquid droplets are calculated analytically. Pair potentials between capillary monopoles and dipoles, corresponding to particles floating on a droplet with a fixed center of mass and subjected to e…

[Phys. Rev. E 84, 031401] Published Thu Sep 01, 2011

Magnetophoresis—the motion of magnetic particles under applied magnetic gradient—is a process of great interest in novel applications of magnetic nanoparticles and colloids. In general, there are two main different types of magnetophoresis processes: cooperative magnetophoresis (a fast process enhan…

[Phys. Rev. E 84, 021402] Published Mon Aug 22, 2011

We present experimental measurements of dynamical heterogeneities in a dense system of microgel spheres, sheared at different rates and at different packing fractions in a microfluidic channel, and visualized with high-speed digital video microscopy. A four-point dynamic susceptibility is deduced fr…

[Phys. Rev. E 84, 021403] Published Mon Aug 22, 2011

We have developed a method based on the Mie theory for determining the local polymer concentration inside spherical nanoparticles, thereby obtaining vital information about whether the particles are swelling in the solvent or if they are contracted into a more compact structure. In addition, this me…

[Phys. Rev. E 84, 022401] Published Mon Aug 08, 2011

A theory of aerosol coagulation rates resulting from continuum-regime Brownian coagulation in the presence of size-dependent particle thermophoresis is developed and explored here. We are motivated by a wide variety of applications in which particle Brownian coagulation occurs in a nonisothermal gas…

[Phys. Rev. E 84, 021401] Published Fri Aug 05, 2011