Simple particles with no twist can form spinning crystals just by touching nearby dust.
Collective rotation in nature usually requires individual parts to be asymmetric or chiral, like a propeller. This study found that perfectly symmetric particles can self-organize into solid-like living crystals that rotate as a single unit. This spinning is fueled by feedback from the surrounding environment of smaller, passive particles. The environment effectively creates a torque that forces the entire crystal to spin. This shows that complex, life-like motion can emerge from very simple rules and environmental interactions. It offers a new way to design self-moving micro-machines and synthetic tissues that do not require complex parts.
Spinning Living Crystals of Run-and-Tumble Particles with Environmental Feedback
arXiv · 2604.16163
Collective rotations are common in active matter, enhancing cohesion, transport, and mixing. They are typically attributed to chiral non-reciprocal dynamics due to intrinsic particle chirality, torque-generating interactions among units, or geometric confinement. Here, we uncover a different mechanism for rotational order in active matter where a dynamic environment coordinates the self-organization of non-chiral active particles into living crystals exhibiting sustained collective solid-like ro