We experimentally and theoretically study the variety of elastic deformations that appear when colloidal inclusions are embedded in thin wetting films of a nematic liquid crystal with hybrid anchoring conditions. In the thickest films, the elastic dipoles formed by particles and their accompanying defects share features with the patterns commonly observed in liquid crystal cells. When the film gets thinner than the particles size, however, the capillary effects strongly modify the appearance of the elastic dipoles and the birefringence patterns. The influence of the film thickness and particles sizes on the patterns has been explored. The main experimental features and the transitions observed at large scale—with respect to the inclusions’ size—are explained with a simple two-dimensional Ansatz, combining capillarity and nematic elasticity. In a second step, we discuss the origin of the variety of observed textures. Developing a three-dimensional Landau-de Gennes model at the scale of the particles, we show that the presence of free interfaces and the beads confinement yield metastable configurations that are quenched during the film spreading or the beads trapping at interfaces.

We form films of carboxylated polystyrene particles (C-PS) at the air water interface and investigate the effect of subphase pH on their structure and rheology by using a suite of complementary experimental techniques. Our results suggest that electrostatic interactions drive the stability and the structural order of the films. In particular, we show that by increasing the pH of the subphase from 9 up to 13, the films exhibit a gradual transition from solid to liquidlike, which is accompanied by a loss of the long-range order (that characterizes them at lower values of pH). Direct optical visualization of the layers, scanning electron microscopy, and surface pressure isotherms indicate that the particles deposited at the interface form three-dimensional structures involving clusters, with the latter being suppressed and a quasi-2D particle configuration eventually reached at the highest pH values. Evidently, the properties of colloidal films can be tailored significantly by altering the pH of the subphase.

We study the dynamics of individual polystyrene ellipsoids of different aspect ratios trapped at the air-water interface. Using particle tracking and in situ vertical scanning interferometry techniques we are able to measure translational drags and the protrusion in air of the ellipsoids. We report that translational drags on the ellipsoid are unexpectedly enhanced: despite the fact that a noticeable part of the ellipsoid is in air, drags are found larger than the bulk one in water.

Binary c–T phase diagrams of organogelators in solvent are frequently simplified to two domains, gel and sol, even when the melting temperatures display two distinct regimes, an increase with T and a plateau. Herein, the c–T phase diagram of an organogelator in solvent is elucidated by rheology, DSC, optical microscopy, and transmitted light intensity measurements. We evidence a miscibility gap between the organogelator and the solvent above a threshold concentration, cL. In this domain the melting or the formation of the gel becomes a monotectic transformation, which explains why the corresponding temperatures are nonvariant above cL. As shown by further studies by variable temperature FTIR and NMR, different types of H-bonds drive both the liquid–liquid phase separation and the gelation.

Ultrasound-modulated optical tomography (UOT) is a technique that images optical contrast deep inside scattering media. Heterodyne holography is a promising tool able to detect the UOT tagged photons with high efficiency. In this work, we describe theoretically the detection of the tagged photon in heterodyne holography based UOT, show how to filter the untagged photon discuss, and discuss the effect of speckle decorrelation. We show that optimal detection sensitivity can obtain, if the frame exposure time is of the order of the decorrelation time.

Colloids and nanoparticles possessing two different faces with distinct properties are called Janus as the Roman God depicted with two faces looking in opposite directions. In this talk a fabrication of Janus particles by droplet based microfluidics will be presented. Silica colloids dispersed in the oil phase and gold nanoparticles dispersed in the aqueous phase meet at the droplet oil-water interface. The contact angle of the silica colloid defines the area of the silica face immersed in water, which can be decorated by the gold nanoparticles, forming the Janus silica-gold particle.Many physical and physicochemical aspects take part in this process. Wetting of the silica and gold particles set the contact angle of the particles at the droplet interface, which depends strongly on the chemical groups used to stabilize the particles, and in principle allow the fabrication of Janus particles of different area ratios. Adsorption onto the oil-water interface is also a key process, which depends not only on the concentration but also on the hydrodynamic flows and geometry present in the microfluidic channels. The role of long range surface forces such as Van der Waals and electrostatic will be also highlighted both for the adsorption kinetics and for the effect on the particle size dependent contact angle.

Commercial carboxymethylcellulose was used to prepare dispersible multi-walled carbon nanotubes-based composites. These composites were employed to prepare Pickering oil-in-water emulsions. Emulsion-templated macroporous materials were then prepared by embedding the oil droplets into a polymer resin arising from the polycondensation of furfural and phloroglucinol within the continuous aqueous phase in the presence of FeCl3 as catalyst. Polymerization afforded organic–inorganic nanocomposite materials in the form of capsules. After pyrolysis, highly microporous, magnetic and electrically conductive micrometric capsules could be obtained. This approach opens interesting prospects for catalysis, separation and electrochemistry applications.