Critical Casimir interaction of ellipsoidal colloids with a planar wall

Kondrat, Svyatoslav; Harnau, Ludger; Dietrich, S.

doi:10.1063/1.3259188

Cited by 45 publications

(81 citation statements)

References 65 publications

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“…In the context of critical Casimir forces such elongated particles have so far only been investigated in two theoretical studies. In the presence of a homogeneous substrate MFT predicts the occurrence of a critical Casimir torque within the plane normal to the substrate surface [56]. In Ref.…”

Section: Dashed Lines) the Center Of The Colloid Is Located At (A Anmentioning

confidence: 98%

Alignment of cylindrical colloids near chemically patterned substrates induced by critical Casimir torques

et al. 2014

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Recent experiments have demonstrated a fluctuation-induced lateral trapping of spherical colloidal particles immersed in a binary liquid mixture near its critical demixing point and exposed to chemically patterned substrates. Inspired by these experiments, we study this kind of effective interaction, known as the critical Casimir effect, for elongated colloids of cylindrical shape. This adds orientational degrees of freedom. When the colloidal particles are close to a chemically structured substrate, a critical Casimir torque acting on the colloids emerges. We calculate this torque on the basis of the Derjaguin approximation. The range of validity of the latter is assessed via mean-field theory. This assessment shows that the Derjaguin approximation is reliable in experimentally relevant regimes, so that we extend it to Janus particles endowed with opposing adsorption preferences. Our analysis indicates that critical Casimir interactions are capable of achieving well-defined, reversible alignments both of chemically homogeneous and of Janus cylinders.

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Section: Dashed Lines) the Center Of The Colloid Is Located At (A Anmentioning

confidence: 98%

Alignment of cylindrical colloids near chemically patterned substrates induced by critical Casimir torques

et al. 2014

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“…We calculate the normal and lateral forces directly from the numerically determined order parameter profiles φ(x, y, z) by using the stress tensor which, within the Ginzburg-Landau approach, is given by [29,35,42] …”

Section: Physical Systemmentioning

confidence: 99%

“…These long-ranged forces arise as a consequence of the confinement of the order parameter fluctuations in a critical fluid [23]. They have been analyzed paradigmatically by studying the effective interaction between a single colloidal particle and a homogeneous [24][25][26][27][28][29][30][31][32] or inhomogeneous [33][34][35][36][37] container wall as well as between two isolated colloidal particles [24][25][26][27][28] upon approaching the critical point of the solvent. Here we add one sphere to the sphere-wall configuration, which is the simplest possibility to study many-body forces.…”

Section: Introductionmentioning

confidence: 99%

Many-body effects for critical Casimir forces

Mattos

Harnau

Dietrich

2013

The Journal of Chemical Physics

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Within mean-field theory we calculate the scaling functions associated with critical Casimir forces for a system consisting of two spherical colloids immersed in a binary liquid mixture near its consolute point and facing a planar, homogeneous substrate. For several geometrical arrangements and boundary conditions we analyze the normal and the lateral critical Casimir forces acting on one of the two colloids. We find interesting features such as a change of sign of these forces upon varying either the position of one of the colloids or the temperature. By subtracting the pairwise forces from the total force we are able to determine the many-body forces acting on one of the colloids. We have found that the many-body contribution to the total critical Casimir force is more pronounced for small colloid-colloid and colloid-substrate distances, as well as for temperatures close to criticality, where the many-body contribution to the total force can reach up to 25%.

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“…As far as the theoretical side is concerned, it was de Gennes who first obtained the CCF between spherical particles [53] considering a local freeenergy functional. Among the other techniques used to study the CCF in sphere-plate and sphere-sphere geometries are the Ornstein-Zernike theory [54], conformal invariance methods [55][56][57], Monte Carlo calculations [58][59][60][61][62][63][64][65][66][67], fluid-particle dynamics simulations [68,69], mean-field type [70][71][72][73][74] and density-functional [75] theory calculations combined with the Derjaguin approximation [44,[76][77][78]. Several review articles and works [8,[79][80][81][82] summarize both the experimental and theoretical results presented there.…”

Section: Introductionmentioning

confidence: 99%

Sign change in the net force in sphere-plate and sphere-sphere systems immersed in nonpolar critical fluid due to the interplay between the critical Casimir and dispersion van der Waals forces

Valchev

Dantchev

2017

Phys. Rev. E

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We study systems in which both long-ranged van der Waals and critical Casimir interactions are present. The last arise as an effective force between bodies when immersed in a near-critical medium, say a nonpolar onecomponent fluid or a binary liquid mixture. They are due to the fact that the presence of the bodies modifies the order parameter profile of the medium between them as well as the spectrum of its allowed fluctuations. We study the interplay between these forces, as well as the total force (TF) between a spherical colloid particle and a thick planar slab, and between two spherical colloid particles. We do that using general scaling arguments and mean-field type calculations utilizing the Derjaguin and the surface integration approaches. They both are based on data of the forces between two parallel slabs separated at a distance L from each other, confining the fluctuating fluid medium characterized by its temperature T and chemical potential µ. The surfaces of the colloid particles and the slab are coated by thin layers exerting strong preference to the liquid phase of the fluid, or one of the components of the mixture, modeled by strong adsorbing local surface potentials, ensuring the socalled (+, +) boundary conditions. On the other hand, the core region of the slab and the particles, influence the fluid by long-ranged competing dispersion potentials. We demonstrate that for a suitable set of colloids-fluid, slab-fluid, and fluid-fluid coupling parameters the competition between the effects due to the coatings and the core regions of the objects involved result, when one changes T , µ or L, in sign change of the Casimir force (CF) and the TF acting between the colloid and the slab, as well as between the colloids. This can be used for governing the behavior of objects, say colloidal particles, at small distances, say in colloid suspensions for preventing flocculation. It can also provide a strategy for solving problems with handling, feeding, trapping and fixing of microparts in nanotechnology. Data for specific substances in support of the experimental feasibility of the theoretically predicted behavior of the CF and TF have been also presented.

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Critical Casimir interaction of ellipsoidal colloids with a planar wall

Cited by 45 publications

References 65 publications

Alignment of cylindrical colloids near chemically patterned substrates induced by critical Casimir torques

Alignment of cylindrical colloids near chemically patterned substrates induced by critical Casimir torques

Many-body effects for critical Casimir forces

Sign change in the net force in sphere-plate and sphere-sphere systems immersed in nonpolar critical fluid due to the interplay between the critical Casimir and dispersion van der Waals forces

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