'Dancing' holes in droplets submerged in water-ethanol mixtures: New form of 'active matter' driven by the dissolution of droplets of an ionic liquid

Researchers have observed the formation of holes that move by themselves in droplets of ionic liquids (IL) sitting inside water-ethanol mixtures. This curious, complex phenomenon is driven by an interplay between how ionic liquids dissolve, and how the boundary around the droplet fluctuates. Self-driven motion is a key feature of active matter, materials that use ambient energy to self-propel, with potential applications to drug delivery and nano-machine propulsion.