"Magic Numbers" in Self-Faceting of Alcohol-Doped Emulsion Droplets.

Oil-in-water emulsion droplets spontaneously adopt, below some temperature T , counterintuitive faceted and complex non-spherical shapes while remaining liquid. This transition is driven by a crystalline monolayer formed at the droplets' surface. Here, we show that ppm-level doping of the droplet's bulk by long-chain alcohols allows tuning T by >50 °C, implying formation of drastically different interfacial structures.

Anomalous Temperature-Controlled Concave-Convex Switching of Curved Oil-Water Menisci.

While the curvature of the classical liquid surfaces exhibits only a weak temperature dependence, we demonstrate here a reversible temperature-tunable concave-convex shape switching in capillary-contained, surfactant-decorated, oil-water interfaces. The observed switching gives rise to a concave-convex shape transition, which takes place as a function of the width of the containing capillary. This apparent violation of Young's equation results from a hitherto-unreported sharp reversible hydrophobic-hydrophilic transition of the glass capillary walls.

Polyhedral Water Droplets: Shape Transitions and Mechanism.

While classical liquid droplets are rounded, transitions have recently been discovered which render polyhedral water-suspended droplets of several oils. Yet, the mechanism of these transitions and the role of the droplets' interfacial curvature in inducing these transitions remain controversial. In particular, one of the two mechanisms suggested mandates a convex interface, in a view from the oil side.

Precise Self-Positioning of Colloidal Particles on Liquid Emulsion Droplets.

Decorating emulsion droplets by particles stabilizes foodstuff and pharmaceuticals. Interfacial particles also influence aerosol formation, thus impacting atmospheric CO exchange. While studies of particles at disordered droplet interfaces abound in the literature, such studies for ubiquitous ordered interfaces are not available.

Axial Confocal Tomography of Capillary-Contained Colloidal Structures.

Confocal microscopy is widely used for three-dimensional (3D) sample reconstructions. Arguably, the most significant challenge in such reconstructions is posed by the resolution along the optical axis being significantly lower than in the lateral directions. In addition, the imaging rate is lower along the optical axis in most confocal architectures, prohibiting reliable 3D reconstruction of dynamic samples.

Denser fluids of charge-stabilized colloids form denser sediments.

Granular matter, where solid-like elasticity emerges in the absence of crystalline order, has been actively studied over the last few decades, targeting fundamental physical understanding of granular packings and glasses, abundant in everyday life and technology. We employ charge-stabilized sub-micron particles in a solvent, known as colloids, to form granular packings through a well-controlled process, where initially homogeneous and thermodynamically equilibrated colloidal fluids form solid sediments, when subjected to an effective gravity in a centrifuge. We demonstrate that particles' volume fraction φj in these sediments increases linearly with that in the initial fluid φ0, setting an upper limit φRCP≈ 0.

Dense colloidal fluids form denser amorphous sediments.

We relate, by simple analytical centrifugation experiments, the density of colloidal fluids with the nature of their randomly packed solid sediments. We demonstrate that the most dilute fluids of colloidal hard spheres form loosely packed sediments, where the volume fraction of the particles approaches in frictional systems the random loose packing limit, ϕRLP = 0.55.