Pickering nanoemulsions: An overview of manufacturing processes, formulations, and applications

There is an increasing demand for emulsions with low viscosity, a large fraction of dispersed phase, high transparency, or long shelf life. Emulsions consisting of nanosized dispersed droplets meet these criteria, but conventional nanoemulsions require large quantities of surfactants, some of which are unwanted due to health and environmental concerns. Surfactants can then be replaced by solid particles, forming the so-called Pickering emulsions. Combining nanosized droplets and particle-stabilized emulsions leads to Pickering nanoemulsions. Since their first appearance in 2012, they have received increasing attention, but several points remain challenging; the choice of particles according to their origin, shape, sizes, and wetting properties and the process to produce drop sizes in the nano range. This review describes the recent advances in terms of manufacturing processes and destabilization mechanisms of Pickering nanoemulsions. It reports the particles used to stabilize the oil-water interface and strategies to improve their wetting properties, as well as examples of applications for the design of formulations in the pharmaceutics, food packaging, and enhanced oil recovery sectors.