Some of the particles’ facets grow while other shrink, producing a variety of geometrical forms such as kites, isosceles triangles and spiked tetrahedra. Then, from some of the sharp corners emerge tentacle-like strands, as if being extruded from a nozzle. As they grow, the strands bend into undulating shapes — and the droplets start to swim, propelled through the fluid by the tentacles’ extension.
If ever a science fiction movie director were seeking inspiration for how to depict tiny robotic alien life forms, they need look no further than those created by a team of scientists in Bulgaria, Poland, the UK and China. Beginning as innocuous oily droplets about 20–40μm across floating in water, these structures take on faceted, crystal-like shapes when cooled to around 2-8°C – even though they aren’t frozen.
Then things get really weird.