Chaotic flows driven by ±½ topological defects in active nematics — the spontaneous velocity field of self-propelled rod-like particles.
Active nematics (e.g. microtubule-kinesin mixtures, cell monolayers) spontaneously generate turbulent flows without inertia. ±½ defects are continuously created in pairs and annihilate, driving persistent chaotic motion. The +½ defect is comet-shaped and self-propels; the −½ is trefoil-shaped and passive.