Non-equilibrium sedimentation of colloids: confocal microscopy and Brownian dynamics simulations

Schmidt, Matthias; Royall, C. Patrick; Blaaderen, Alfons van; Dzubiella, Joachim

doi:10.1088/0953-8984/20/49/494222

Cited by 17 publications

(15 citation statements)

References 62 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Again, caution about residual charges applies. Alternatively, g(r) determined from confocal microscopy can be fitted to the PY form or to simulation data [81] to give φ.…”

Section: F Measuring φ-Dependent Propertiesmentioning

confidence: 99%

On measuring colloidal volume fractions

Poon¹,

Weeks²,

Royall³

2012

Soft Matter

195

242

View full text Add to dashboard Cite

Hard-sphere colloids are popular as models for testing fundamental theories in condensed matter and statistical physics, from crystal nucleation to the glass transition. A single parameter, the volume fraction (phi), characterizes an ideal, monodisperse hard-sphere suspension. In comparing experiments with theories and simulation, researchers to date have paid little attention to likely uncertainties in experimentally-quoted phi values. We critically review the experimental measurement of phi in hard-sphere colloids, and show that while statistical uncertainties in comparing relative values of phi can be as low as 0.0001, systematic errors of 3-6% are probably unavoidable. The consequences of this are illustrated by way of a case study comparing literature data sets on hard-sphere viscosity and diffusion.Comment: 11 page

show abstract

“…Again, caution about residual charges applies. Alternatively, g(r) determined from confocal microscopy can be fitted to the PY form or to simulation data [81] to give φ.…”

Section: F Measuring φ-Dependent Propertiesmentioning

confidence: 99%

On measuring colloidal volume fractions

Poon¹,

Weeks²,

Royall³

2012

Soft Matter

195

242

View full text Add to dashboard Cite

show abstract

“…While early theoretical works focused upon (a) kruegerm@mit.edu (b) joseph.brader@unifr.ch the influence of hydrodynamic interactions on the sedimentation velocity in dilute systems (see e.g. [12][13][14]), the dynamic settling of denser suspensions has only recently been studied in detail in experiments, Brownian dynamics simulations, and theoretically, using dynamic density functional theory (DDFT) [15][16][17]. Incorporating hydrodynamic interactions into theories of dense suspensions is a difficult task, although recently some progress has been made [18,19].…”

mentioning

confidence: 99%

“…where γ 0 is the strain amplitude, ω is the frequency and Θ(τ ) is the unit step function. The oscillatory shear protocol (17) can be realized experimentally, e.g. in a simple parallel plate shear cell, which is particularly advantageous when seeking to combine rheological measurements with real space (confocal) microscopy (see e.g.…”

mentioning

confidence: 99%

Controlling colloidal sedimentation using time-dependent shear

Krüger

Brader

2011

EPL

View full text Add to dashboard Cite

Abstract. -Employing a recently developed dynamical density functional theory we study the response of a colloidal sediment above a wall to shear, demonstrating the time dependent changes of the density distribution and its center-of-mass after switching shear either on or off and under oscillatory shear. Following the onset of steady shear we identify two dynamical mechanisms, distinguished by their timescales. Shortly after the onset, a transient enhancement of the packing structure at the wall reflects the self-organization into lanes. On a much longer timescale these effects are transmitted to the bulk, leading to migration away from the wall and an increase in the center-of-mass. Under oscillatory shear flow the center-of-mass enters a stationary state, reminiscent of a driven damped oscillator.Colloidal suspensions under shear have been the subject of intense research during the last decades, both theoretically as well as in simulations and experiments [1][2][3][4]. Dense systems have attracted particular attention, as particle interactions can transmit the effects of shear into directions perpendicular to the flow, leading to nontrivial collective dynamics. An important consequence of applying steady shear is that the intrinsic slow dynamics exhibited by quiescent dense systems (and characterized by observables such as density correlators or mean squared displacements [5][6][7][8][9]) can be sped up drastically in all spatial directions, provided the shear rate exceeds the inverse of the structural relaxation time [10]. The dynamical response becomes richer still when considering timedependent shear fields for which transient dynamics can play a dominant role (e.g. oscillatory shear [11]).In real colloidal systems the buoyant mass of the suspended particles is often nonzero, such that gravity drives the formation of a nonuniform density distribution: A colloidal sediment (or creaming profile, in the event that the buoyant mass is negative). The study of colloidal sedimentation has a long history, effectively starting with the pioneering experimental work of Perrin at the start of the 19th century. While early theoretical works focused upon (a) kruegerm@mit.edu (b) joseph.brader@unifr.ch the influence of hydrodynamic interactions on the sedimentation velocity in dilute systems (see e.g. [12][13][14]), the dynamic settling of denser suspensions has only recently been studied in detail in experiments, Brownian dynamics simulations, and theoretically, using dynamic density functional theory (DDFT) [15][16][17]. Incorporating hydrodynamic interactions into theories of dense suspensions is a difficult task, although recently some progress has been made [18,19].Experiments in which shear flow has been applied to particle sediments (where in the early literature, mostly large, nearly non-Brownian particles were considered) report changes in the viscosity, attributed to a shear induced modification of the underlying microstructure [20]. Moreover, an increase in the height of the sediment has been observed with inc...

show abstract

“…Brownian dynamics simulations have been used intensively to study the physics of different kind of macromolecules and soft matter systems [4], as for example, the rheological behaviour of polymer [5,6,7,8,9,10], the dynamics of proteins and DNA [11,12,13,14], the flow behaviour of colloids [15,16,17,18,19,20,21], the structural dynamics of liquid-crystals [22,23] and the dynamics of carbon nanotubes [24,25,26,27]. …”

Section: Brownian Dynamics Modellingmentioning

confidence: 99%

Review on the Brownian Dynamics Simulation of Bead-Rod-Spring Models Encountered in Computational Rheology

Cruz

Chinesta

Régnier

2012

Arch Computat Methods Eng

View full text Add to dashboard Cite

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. Abstract Kinetic theory is a mathematical framework intended to relate directly the most relevant characteristics of the molecular structure to the rheological behaviour of the bulk system. In other words, kinetic theory is a micro-to-macro approach for solving the flow of complex fluids that circumvents the use of closure relations and offers a better physical description of the phenomena involved in the flow processes. Cornerstone models in kinetic theory employ beads, rods and springs for mimicking the molecular structure of the complex fluid. The generalized bead-rod-spring chain includes the most basic models in kinetic theory: the freely jointed bead-spring chain and the freely-jointed bead-rod chain. Configuration of simple coarse-grained models can be represented by an equivalent FokkerPlanck (FP) diffusion equation, which describes the evolution of the configuration distribution function in the physical and configurational spaces. FP equation can be a complex mathematical object, given its multidimensionality, and solving it explicitly can become a . This paper presents a review of the fundamental issues in the BD simulation of the linear viscoelastic behaviour of bead-rod-spring coarse grained models in dilute solution. In the first part of this work, the BD numerical technique is introduced. An overview of the mathematical framework of the BD and a review of the scope of applications are presented. Subsequently, the links between the rheology of complex fluids, the kinetic theory and the BD technique are established at the light of the stochastic nature of the bead-rod-spring models. Finally, the pertinence of the present state-ofthe-art review is explained in terms of the increasing interest for the stochastic micro-to-macro approaches for solving complex fluids problems. In the second part of this paper, a detailed description of the BD algorithm used for simulating a small-amplitude oscillatory deformation test is given. Dynamic properties are employed throughout this work to characterise the linear viscoelastic behaviour of bead-rod-spring models in dilute solution. In the third and fourth part of this article, an extensive discussion about the main issues of a BD simulation in linear viscoelasticity of diluted suspensions is tackled at the light of the classical multibead-spring chain model and the multi-bead-rod chain model, respectively. Kinematic formulations, integration schemes and expressions to calculate the stress tensor are revised for several classical models: Rouse and Zimm theories in the case of multi-bead-spring chains, and Kramers chain and semi-flexible filaments in the case of multi-bead-rod chains. The implemented BD technique is, on the one hand, validated in front of the analytical or exact numerical solutions known of the equivalent FP equations for those classic kinetic theory models; and, on the other hand, is control-set th...

show abstract

Non-equilibrium sedimentation of colloids: confocal microscopy and Brownian dynamics simulations

Cited by 17 publications

References 62 publications

On measuring colloidal volume fractions

On measuring colloidal volume fractions

Controlling colloidal sedimentation using time-dependent shear

Review on the Brownian Dynamics Simulation of Bead-Rod-Spring Models Encountered in Computational Rheology

Contact Info

Product

Resources

About