Polyhedral liquid droplets: Recent advances in elucidation and application

The rediscovery of temperature-controlled self-faceting, shaping, and splitting transitions in liquid oil-in-water emulsion droplets, has recently led to a significant progress in the fundamental understanding of these counterintuitive phenomena, sparking scientific controversies, and opening new routes towards their technological applications. These recent developments are reviewed here. The faceting transitions were demonstrated to occur in a wide range of oil:surfactant combinations, for broad temperature ranges, and in droplets of sizes spanning an incredible 13 decades in volume, from nano (11×10⁻⁹) to yocto (300×10⁻²⁴) liters. Droplets' polymerization enables forming solid faceted particles, of shapes and sizes otherwise unachievable. Colloids and nanoparticles adsorbed controllably onto the faceted liquid droplets' interfaces self-position at their vertices and self-expel into the aqueous medium. The self-positioning enables droplets’ decoration by precisely positioned functional ligands, paving the way for directed self-assembly of multiparticle structures for a wide range of microtechnological and nanotechnological applications.