We report on the behavior of micron-sized prolate ellipsoids trapped at an oil-water interface. The particles experience strong, anisotropic, and long-ranged attractive capillary interactions which greatly exceed thermal energy ${k}_{B}T$. Depending surface chemistry, aggregate into open structures or chains. Using video microscopy, we extract pair interaction potential between show it exhibits a power law over length scales probed. Our observations can be explained using recent...

The Stokes-Einstein relation relates the diffusion coefficient of a spherical Brownian particle in viscous fluid to its friction coefficient. For suspended anisotropic liquid, theory predicts that drag should also be anisotropic. Using video microscopy coupled with tracking routines, fluctuations micrometer-sized particles were analyzed yield quantitative measurement coefficients parallel and perpendicular nematic director. experimental values agree quite well recent numerical calculations...

We experimentally and theoretically investigate the shapes of contact lines on surfaces micrometer-sized polystyrene ellipsoids at water-air interface. By combining interferometry optical trapping, we directly observe quadrupolar symmetry interface deformations around such particles. then develop numerical solutions partial wetting problem for ellipsoids, use these to deduce corresponding values angles, ${\ensuremath{\theta}}_{c}(k)$, as a function ellipsoid aspect ratio $k$. Surprisingly,...

We study the behavior of colloidal particles suspended in a thermotropic nematic solvent presence an electric field. For normal boundary conditions director at particles' surface, we show experimentally that field applied along dipolar axis elastic dipole induces transition to quadrupolar configuration. Turning off makes system go back initial state. also it is possible directly evidence repulsion between droplets.

Anisotropic particles adsorbed at a water-air interface are known to aggregate due capillary interactions. We show that the packing configuration of pair prolate ellipsoids critically depends on their relative size and/or aspect ratio mismatch. While identical simply pack side-by-side, slightly different sizes observed systematically self-assemble into characteristic arrows, i.e. with finite angle between axes. The occurrence such arrows cannot be explained within far-field approximation...

A micrometer-sized spherical particle classically equilibrates at the water–air interface in partial wetting configuration, causing about no deformation to interface. In condition of thermal equilibrium, just undergoes faint Brownian motion, well visible under a microscope. We report experimental observations when is made light-absorbing material and heated up by vertical laser beam. show that, small power, trapped on-axis similarly 2-dimensional trapping transparent sphere optical forces....

This experimental paper deals with phase separations of binary mixtures composed a continuous liquid crystal and an isotropic dispersed phase. In contrast to mixtures, the investigated do not lead full separation but self-ordering colloidal particles, as reported earlier (Loudet, J. C. et al. Nature 2000, 407, 611). We present here further aspects such which include kinetics separation, origin formation dislocation-like patterns, influence surfactants, chiral additives, temperature on formed...

Colloidal particles dispersed in a partially ordered medium, such as liquid crystal (LC) phase, disturb its alignment and are subject to elastic forces. These forces long-ranged, anisotropic tunable through temperature or external fields, making them valuable asset control colloidal assembly. The latter is very sensitive the particle geometry since it alters interactions between colloids. We here present detailed numerical analysis of energetics elongated objects, namely prolate ellipsoids,...

We experimentally study the behavior of micrometer-sized prolate ellipsoidal particles dispersed in a nematic liquid crystal. The latter is an aqueous solution rodlike micelles. When embedded into such solvent, ellipsoids with small enough aspect ratios aggregate to form anisotropic structures oriented at angle respect local background director (as already observed for spheres). This is, however, no longer case when ratio reaches well-defined value: above that value, remain well and...

Using optical microscopy, phase shifting interferometry and atomic force we demonstrate the existence of undulated structures in meniscus ferroelectric smectic-C* films. The is characterized by a periodic undulation smectic-air interface, which manifests itself striped pattern. instability disappears untilted smectic-A phase. modulation amplitude wavelength both depend on thickness. We study temperature evolution structure propose simple model that accounts for observed undulations.

We report on optical levitation of dielectric particles, prolate ellipsoidal shape, a few tens micrometers in length, low-aperture laser beam. Ellipsoids moderate aspect ratio (k < 3) are observed to be trapped the axis beam, similarly simple spheres. Conversely, elongated particles > cannot kept immobile, and rather undergo sustained oscillating motions, comprising both lateral angular excursions around beam axis; hence name "tumble". The tumbling motion, straightforward manifestation...

We investigate the radial thermocapillary flow driven by a laser-heated microbead in partial wetting at water–air interface. Particular attention is paid to evolution of convective patterns surrounding hot sphere as latter increasingly heated. The morphology nearly axisymmetric low laser power (P). Increasing P leads symmetry breaking with onset counter-rotating vortex pairs. boundary condition interface, close no-slip low-P regime, turns about stress-free between pairs high-P regime. These...

We report the experimental observation of anisotropic diffusion polystyrene particles immersed in a lyotropic liquid crystal with two different anchoring conditions. Diffusion is shown to obey Stokes-Einstein law for particle diameters ranging from 190 nm up 2 micron. In case prolate micelles, beads diffuse four times faster along director than perpendicular directions. theory part we present perturbative approach Leslie-Ericksen equations and relate coefficients Miesovicz viscosity...

Striped patterns in the meniscus of smectic membranes: free surface is distorted and forms wrinkles, bumps dimples.

Significance The formulation of colloidal particle/liquid crystal (LC) composites is a well-identified route toward the design smart responsive materials with tunable optical or mechanical properties. However, particles aggregate because they distort intrinsic order LC phases, which costs elastic energy. For micrometer-sized inclusions, resulting forces dominate coarsening system. In this paper, we find previously unidentified regime where interactions no longer prevail when are downsized to...

We report on the formation of edge dislocations in two-dimensional crystals colloidal chains particles suspended a nematic solvent. The systems are obtained from phase separation binary mixture composed polymer and liquid crystal. structures governed by elastic interactions mediated matrix. Since latter one breaks rotational invariance symmetry, distortions around cannot be appropriately described existing theories. develop simple model which accounts for this symmetry breaking to gain...

We study nonaqueous emulsions that are composed of liquid crystal and silicone oils. New surfactant molecules specifically synthesized to stabilize these emulsions. The behavior the present surfactants is reminiscent classical used for aqueous Depending on their affinity or oils, they may either in Stabilization be potentially useful as a new method making electrooptical display instruments known polymer dispersed devices. It also presents way impart specific optical properties materials...

The Stokes flow of a submerged jet directed toward free interface is investigated theoretically. presence minute amount surface-active agents drastically modifies the hydrodynamic response interface.

This article reviews recent findings on the formation of ordered colloidal structures from bulk demixing in liquid crystalline materials. In contrast to classical phase separations, which lead randomly distributed macrodomains various sizes, crystals leads remarkably uniform droplets that form arrays either infinitely long straight chains (nematic phase) or highly curved (cholesteric phase). distinctive behaviour arises presence topological defects and elastic distortions around inclusions...