We studied the Brownian motion of isolated ellipsoidal particles in water confined to two dimensions and elucidated effects coupling between rotational translational motion. By using digital video microscopy, we quantified crossover from short-time anisotropic long-time isotropic diffusion directly measured probability distributions functions for displacements. confirmed interpreted our measurements by Langevin theory numerical simulations. Our observations provide insights into fundamental...

We present a novel surface-controlled bistable nematic liquid crystal display. This black and white device uses simple monostable planar anchorings dielectrically positive nematic. The two textures are, respectively, quasiuniform U almost half-turn twisted T. Short electric pulses break the surface anchorings. Hydrodynamically coupled breaking of both creates is obtained by only one anchoring. Write erase times for high resolution video are achieved at voltages compatible with usual drivers.

To explain the observed deviation from Rapini-Papoular surface energy of nematic-liquid-crystals, we propose a model form Tr[(${\mathit{Q}}_{\mathit{i}\mathit{j}}$-${\mathit{Q}}_{0\mathit{i}\mathit{j}}$${)}^{2}$] (${\mathit{Q}}_{\mathit{i}\mathit{j}}$ is quadrupolar order parameter nematic-liquid-crystal and ${\mathit{Q}}_{0\mathit{i}\mathit{j}}$ field). For broken anchoring, this predicts decrease \ensuremath{\Delta}S\ensuremath{\approxeq}3/2(\ensuremath{\xi}/d)${\mathit{S}}_{\mathit{B}}$...

We study the nematic-smectic phase transition of a thermotropic liquid crystal confined to spherical shell. Far from temperature, ${T}_{\mathrm{NS}}$, we observe configuration with four $+1/2$ defects, as predicted by theory. Since in this case ${K}_{1}\ensuremath{\approx}{K}_{3}$, defects are at thinnest part shell minimize energy associated defect cores. By contrast, near where ${K}_{3}\ensuremath{\gg}{K}_{1}$, bend distortions become prohibited and organize themselves along great circle...

We report on video-microscopy measurements of the translational and rotational Brownian motions isolated ellipsoidal particles in quasi-two-dimensional sample cells increasing thickness. The long-time diffusion coefficients were measured along long $({D}_{a})$ short $({D}_{b})$ ellipsoid axes, respectively, ratio, ${D}_{a}/{D}_{b}$, was determined as a function wall confinement particle aspect ratio. In three dimensions (3D), this ratio $({D}_{a}/{D}_{b})$ cannot be larger than 2, but...

We have investigated the active motion of self-propelled colloids confined at air-water interface and explored possibility enhancing directional Janus by slowing down their rotational diffusion. The two dimensional micron-sized silica-platinum has been experimentally measured particle tracking video-microscopy increasing concentrations catalytic fuel, i.e. H2O2. Compared to in bulk, a dramatic enhancement both persistence length trajectories speed observed. interplay colloid self-propulsion,...

A post-synthesis alignment of individual single-walled carbon nanotubes (SWCNTs) is desirable for translating their unique anisotropic properties to a macroscopic scale. Here, we demonstrate excellent dispersion, orientation and concomitant-polarised photoluminescence SWCNTs in nematic chromonic liquid crystal. The methods obtain stable suspension are described, order parameters the crystal matrix measured independently.

Biological or artificial microswimmers move performing trajectories of different kinds such as rectilinear, circular, spiral ones. Here, we report on circular observed for active Janus colloids trapped at the air–water interface. Circular motion is due to asymmetric and nonuniform surface properties particles caused by fabrication. Motion persistence enhanced partial wetted state actively moving in two dimensions The slowing down in-plane out-of-plane rotational diffusions described discussed.

We measure the electric-field-driven annihilation of nematic disclination pairs with strength $\ifmmode\pm\else\textpm\fi{}1/2$ in $4\mathrm{\text{\ensuremath{-}}}\mathrm{\text{cyano}}\mathrm{\text{\ensuremath{-}}}{4}^{\ensuremath{'}}\mathrm{\text{\ensuremath{-}}}n$-pentylbiphenyl (5CB) liquid crystal. The use a very weak azimuthal anchoring ensures two-dimensional director field. relaxation is governed by formation $\ensuremath{\pi}$ wall connecting two opposite charge defects. $+1/2$...

We examine the behavior of spherical silica particles trapped at an air–nematic liquid crystal interface. When a strong normal anchoring is imposed, beads spontaneously form various structures depending on their area density and nematic thickness. Using optical tweezers, we determine pair potential explain formation these patterns. The energy profile discussed in terms capillary elastic interactions. Finally, detail mechanisms that control hexagonal lattice analyze role gravity for curved interfaces.

We introduce the idea of transformation trajectories to describe evolution nematic shells in terms defect locations and director field when elastic anisotropy shell thickness heterogeneity vary. Experiments are compared numerical results clarify exact role played by these two parameters. demonstrate that is a result symmetry breaking initiated buoyancy enhanced liquid crystal elasticity, irrespective anisotropy. In contrast, anisotropy--in particular, disfavored bend distortion--drives an...

We report theoretical predictions and measurements of the capillary force acting on a spherical colloid smaller than length that is placed curved fluid interface arbitrary shape. By coupling direct imaging interferometry, we are able to measure in situ contact angle correlate its position with respect curvature. Extremely tiny forces down femtonewtons can be measured this method. Measurements agree well theory relating gradient Gaussian curvature mean prior colloidal deposition. Numerical...

A seminal paper [D. R. Nelson, Nano Lett., 2002, 2, 1125.] has proposed that a nematic coating could be used to create valency for spherical colloidal particles through the functionalization of topological defects. Experimental realizations however question complex behaviour solid and defects embedded in such shell. In order address related geometrical issues, we have studied micrometer-sized silica beads trapped shells. We underline mechanisms strongly modify texture simple (particle-free)...

A hydrolytic polycondensation reaction of a rigid, rodlike nonmesomorphous precursor leads to an isotropic sol and then anisotropic birefringent xerogel (see scheme). Optical X-ray structural analyses demonstrate short-range order the possibility crystalline order.

We measure optically the increase of quadrupolar order \ensuremath{\Delta}S, induced by a stabilizing electric field E, in nematic liquid crystal 4'-n-pentyl-4-cyanobiphenyl with large positive dielectric anisotropy ${\mathrm{\ensuremath{\epsilon}}}_{\mathit{a}}$\ensuremath{\sim}10. \ensuremath{\Delta}S shows linear and quadratic dependence on E. Both effects are comparable for largest E\ensuremath{\sim}3\ifmmode\times\else\texttimes\fi{}${10}^{5}$ V/cm. The variation is interpreted as...

Janus colloidal particles show remarkable properties in terms of surface activity, self-assembly and wetting. Moreover they can perform autonomous motion if chemically react with the liquid which are immersed. In order to understand self-propelled catalytic colloids at air–water interface, wetting orientation important be investigated. Wetting plays a central role active since it determines contact between fuel as well efficiency transduction chemical reaction into motion. Active is not...

This paper concerns the effect of changes in experimental conditions on micrometric-scale organization observed hybrid materials obtained from six rigid rod and semi-rigid bis-trialcoxsilylated precursors one trisilylate after polycondensation at silicon. Different solvents catalysts have been studied showing that birefringence properties are highly dependent these parameters. A drastic catalyst is especially case basic catalysis, which more or less capable inducing a catalytic cleavage...

The relaxation dynamic of a dipole +1/2 and -1/2 parallel disclination lines in confined geometry is measured. confinement the planar anchoring conditions force disclinations to be normal glass plates. In first asymptotic regime, direct elastic interaction between completely screened out by energy. second corresponding final annihilation steps, follows square-root law predicted de Gennes for two isolated disclinations. dynamic, good agreement with an model based on electrostatic analogy.

Surface capillary–gravity waves are experimentally investigated in a cylindrical basin subjected to horizontal oscillation by using high-sensitivity optical method. We study the low-oscillation-amplitude regimes for fluid which wets vertical walls and we show that presence of capillary meniscus can effect greatly main properties system. Both free decay forced oscillations surface investigated. The amplitude, phase damping gravity detail. fundamental mode is found exhibit nonlinear behaviour...