Correction: The effect of wall depletion and hydrodynamic interactions on stress-gradient-induced polymer migration.

Correction for 'The effect of wall depletion and hydrodynamic interactions on stress-gradient-induced polymer migration' by Hossein Rezvantalab et al., Soft Matter, 2016, 12, 5883-5897.

Phase diagram of Janus particles: The missing dimension of pressure anisotropy.

Brownian dynamics simulations of single-patch Janus particles under sedimentation equilibrium reveal that the phases found at fixed temperature and volume fraction are extremely sensitive to small changes in lateral box dimension. We trace this sensitivity to an uncontrolled parameter, namely, the pressure component parallel to the hexagonally ordered layers formed through sedimentation. We employ a flexible-cell constant-pressure scheme to achieve explicit control over this usually overlooked parameter, enabling the estimation of phase behavior under given pressure anisotropy.

Controlled Levitation of Colloids through Direct Current Electric Fields.

We report the controlled levitation of surface-modified colloids in direct current (dc) electric fields at distances as far as 75 μm from an electrode surface. Instead of experiencing electrophoretic deposition, colloids modified through metallic deposition or the covalent bonding of poly(ethylene glycol) (PEG) undergo migration and focusing that results in levitation at these large distances. The levitation is a sensitive function of the surface chemistry and magnitude of the field, thus providing the means to achieve control over the levitation height.

An Aqueous-Based Approach for Fabrication of PVDF/MWCNT Porous Composites.

In this paper, we demonstrate the fabrication of conductive porous polymers based on foaming of an aqueous dispersion of polymeric particles and multi-walled carbon nanotubes (CNT). By tuning the surface energy of the constituents, we direct their preferential adsorption at the air-liquid (bubble) interface or within the liquid film between the bubbles. Sintering this bi-constituent foam yields solid closed-cell porous structure which can be electrically conductive if CNT are able to form a conductive path.

Rotator-to-Lamellar Phase Transition in Janus Colloids Driven by Pressure Anisotropy.

We demonstrate through Brownian dynamics simulations a phase transition in plastic crystalline assemblies of Janus spheres through controlled pressure anisotropy. When the pressure in plane with hexagonally ordered layers is increased relative to that normal to the layers, a rapid first-order rotator-to-lamellar transition of Janus sphere orientation occurs at constant temperature. We show that the underlying mechanism closely follows the Maier-Saupe theory, originally developed for isotropic-to-nematic transition in positionally disordered materials but here applied to positionally ordered ones.

The effect of wall depletion and hydrodynamic interactions on stress-gradient-induced polymer migration.

We generalize our recent continuum theory for the stress-gradient-induced migration of polymers [Zhu et al., J. Rheol.

Tilting and Tumbling of Janus Nanoparticles at Sheared Interfaces.

We investigate the response of a single Janus nanoparticle adsorbed at an oil-water interface to imposed shear flows using molecular dynamics simulations. We consider particles of different geometry, including spheres, cylinders, and discs, and tune their degree of amphiphilicity by controlling the affinity of their two sides to the fluid phases. We observe that depending on the shape, amphiphilicity, and the applied shear rate, two modes of rotational dynamics takes place: a smooth tilt or a tumbling motion.

Molecular simulation of translational and rotational diffusion of Janus nanoparticles at liquid interfaces.

We perform molecular dynamics simulations to understand the translational and rotational diffusion of Janus nanoparticles at the interface between two immiscible fluids. Considering spherical particles with different affinity to fluid phases, both their dynamics as well as the fluid structure around them are evaluated as a function of particle size, amphiphilicity, fluid density, and interfacial tension. We show that as the particle amphiphilicity increases due to enhanced wetting of each side with its favorite fluid, the rotational thermal motion decreases.

Designing patchy particles for optimum interfacial activity.

We study the adsorption of spherical patchy particles to a flat oil-water interface for their potential applications as interface stabilizers. Chemical heterogeneity in form of single and double patches of different sizes is introduced on the surface of a homogeneous particle to induce an amphiphilic character. For a single well-defined patch, we have developed theoretical criteria for designing particles with the maximum degree of surface activity based on any given wettability conditions.

Role of geometry and amphiphilicity on capillary-induced interactions between anisotropic Janus particles.

We study the capillary interactions between ellipsoidal Janus particles adsorbed at flat liquid-fluid interfaces. In contrast to spherical particles, Janus ellipsoids with a large aspect ratio or a small difference in the wettability of the two regions tend to tilt at equilibrium. The interface deforms around ellipsoids with tilted orientations and thus results in energetic interactions between neighboring particles.

Particle adsorption at polydimethylsiloxane (PDMS)/water interfaces in the presence of a cross-linking reaction.

The adsorption of polymeric particles at the interface of spherical drops of polydimethylsiloxane (PDMS) with water is studied in presence of a cross-linking reaction. Hydrophobic colloidal particles are first uniformly dispersed in water with the help of a nonionic surfactant. The PDMS droplets are then introduced to this dispersion.