Microencapsulation is an advanced methodology for the protection, preservation, and/or delivery of active materials in a wide range of industrial sectors, such as pharmaceuticals, cosmetics, fragrances, paints, coatings, detergents, food products, and agrochemicals. Polymeric materials have been extensively used as microcapsule shells to provide appropriate barrier properties to achieve controlled release of the encapsulated active ingredient. However, significant limitations are associated with such capsules, including undesired leaching and the nonbiodegradable nature of the typically used polymers. In addition, the energy cost of manufacturing microcapsules is an important factor to be considered when designing microcapsule systems and the corresponding production processes. Recent factors linked to UN sustainability goals are modifying how such microencapsulation systems should be designed in pursuit of "ideal" microcapsules that are efficient, safe, cost-effective and environmentally friendly. This review provides an overview of advances in microencapsulation, with emphasis on sustainable microcapsule designs. The key evaluation techniques to assess the biodegradability of microcapsules, in compliance with recently evolving European Union requirements, are also described. Moreover, the most common methodologies for the fabrication of microcapsules are presented within the framework of their energy demand. Recent promising microcapsule designs are also highlighted for their suitability toward meeting current design requirements and stringent regulations, tackling the ongoing challenges, limitations, and opportunities.

We have developed a method for transferring particles from a powder bed to a liquid droplet using an electric field. This process has been used to create liquid marbles with characteristics not normally found in those formed by direct contact methods such as rolling. It has also been used to manufacture hydrophilic particle-liquid aggregates and more complex layered aggregates incorporating both hydrophobic and hydrophilic particles. This article briefly outlines the electrostatic aggregation method itself, the materials used and structures formed thus far, and explores the rich fundamental physics and chemistry underpinning the process as they are understood at present.

The impact of polymer emulsifier diffusion rates and droplet formation kinetics are critical for effective control of emulsion droplet size and stability during the membrane emulsification process. It is expected that the molecular weight of a polymer stabiliser will play a significant role in the resultant emulsion due to the low energy nature of the emulsion formation mechanism and dependence on emulsifier diffusion inherent in a membrane emulsification system. Dodecane in water emulsions were formed via membrane emulsification at various concentrations and molecular weights of a polyvinyl alcohol polymer. Emulsion attributes were quantified via laser diffraction and optical microscopy over time. These data were then related to the diffusion time of polymers of different molecular weight at various concentrations via pendent droplet tensiometry. It was found that molecular weight of a polymeric stabiliser and subsequent diffusion to the interface have a significant impact on droplet size, dispersity and stability. Larger polymeric stabilisers were slower to diffuse to the interface, resulting in highly stable larger droplets, while smaller polymers quickly adsorbed to the interface but offered limited steric stabilisation and thus resulted in significant droplet coalescence. Combination of both high and low molecular weight polymers as stabilisers was observed to result in emulsions of low dispersity and controllable sizes for extremely low concentration of polymer.

Larger particles are more readily extracted from an advancing bed of charged particles owing to decreased interparticle cohesion.

To form nonspherical emulsion droplets, the interfacial tension driving droplet sphericity must be overcome. This can be achieved through interfacial particle jamming; however, careful control of particle coverage is required. In this work, we present a scalable novel batch process to form nonspherical particle-stabilized emulsions. This is achieved by concurrently forming interfacially active particles and drastically accelerating emulsion destabilization through addition of electrolyte. To achieve this, surfactant-stabilized oil-in-water emulsions in the presence of dopamine were first produced. These emulsions were then treated with tris(hydroxymethyl)aminomethane hydrochloride buffer to both simultaneously initiate polymerization of dopamine in the emulsion continuous phase and reduce the Debye length of the system, thus accelerating droplet coalescence while forming surface-active particles. The concentration of buffer and imposed shear was then systematically varied, and the behavior at the interface was studied using pendent drop tensiometry and interfacial shear rheology. It was found that polydopamine nanoparticles formed in the emulsion continuous phase adsorbed to the reducing interface during coalescence, resulting in anisotropic droplets formed via arrested coalescence. Greater shear rates resulted in accelerated coalescence and formation of secondary droplets, whereas lower shear rates resulted in thicker interfacial films. The efficacy of this method was further demonstrated with a second system consisting of sodium dodecyl sulfate as the surfactant and polypyrrole particles, which also resulted in nonspherical droplets for optimized conditions.