Adsorption and assembly of colloidal particles at the surface of liquid droplets are at the base of particle-stabilized emulsions and templating. Here we report that electrohydrodynamic and electro-rheological effects in leaky-dielectric liquid drops can be used to structure and dynamically control colloidal particle assemblies at drop surfaces, including electric-field-assisted convective assembly of jammed colloidal 'ribbons', electro-rheological colloidal chains confined to a two-dimensional surface and spinning colloidal domains on that surface. In addition, we demonstrate the size control of 'pupil'-like openings in colloidal shells. We anticipate that electric field manipulation of colloids in leaky dielectrics can lead to new routes of colloidosome assembly and design for 'smart armoured' droplets.

Janus and patchy particles have designed heterogeneous surfaces that consist of two or several patches with different materials properties. These particles are emerging as building blocks for a new class of soft matter and functional materials. Here we introduce a route for forming heterogeneous capsules by producing highly ordered jammed colloidal shells of various shapes with domains of controlled size and composition. These structures combine the functionalities offered by Janus or patchy particles, and those given by permeable shells such as colloidosomes. The simple assembly route involves the synergetic action of electro-hydrodynamic flow and electro-coalescence. We demonstrate that the method is robust and straightforwardly extendable to production of multi-patchy capsules. This forms a starting point for producing patchy colloidosomes with domains of anisotropic chemical surface properties, permeability or mixed liquid-solid phase domains, which could be exploited to produce functional emulsions, light and hollow supra-colloidosome structures, or scaffolds.

Different natural clay minerals, including halloysite, montmorillonite and kaolinite, have been proven to be efficient drug carriers providing for high and long lasting drug concentrations owing to their adsorption capacity and ion exchange property. Synthetic clays, however, are advantageous over the natural clay minerals in terms of purity of composition and controllable cation exchange capacity, factors that contribute to improve reproducibility of the host system. Here we studied a synthetic smectite clay as a candidate for high adsorption and controlled release rate. Via X-ray powder diffraction we verified that, under acidic conditions, the antibiotic ciprofloxacin was successfully incorporated in the synthetic clay fluorohectorite, while via UV-VIS spectroscopy we showed that the degree of the drug incorporation is at least 25% higher than for other systems reported in the literature. Furthermore, temperature dependent release studies allowed us to show that the release process is thermally activated and diffusion-controlled. Finally, via bacterial and toxicological tests, we demonstrated that the effectiveness and toxicity of pure ciprofloxacin is unaffected in the clay–drug complex.

Utilizing electric fields, we have experimentally investigated the mechanics of particle-covered silicone oil drops suspended in castor oil, as well as particle assembly at drop surfaces.

A designed assembly of particles at liquid interfaces offers many advantages for development of materials, and can be performed by various means. Electric fields provide a flexible method for structuring particles on drops, utilizing electrohydrodynamic circulation flows, and dielectrophoretic and electrophoretic interactions. In addition to the properties of the applied electric field, the manipulation of particles often depends on the intrinsic properties of the particles to be assembled. Here, we present an easy approach for producing polystyrene microparticles with different electrical properties. These particles are used for investigations into electric field-guided particle assembly in the bulk and on surfaces of oil droplets. By sulfonating polystyrene particles, we produce a set of particles with a range of dielectric constants and electrical conductivities, related to the sulfonation reaction time. The paper presents diverse particle behavior driven by electric fields, including particle assembly at different droplet locations, particle chaining, and the formation of ribbon-like structures with anisotropic properties.