Defect loops in 3D active nematics

In 2D active nematics, internally driven chaotic flows are characterized by the continual production, motion, and annihilation of point defect pairs. We investigate the behavior of active nematics in 3D, for which we have developed an experimental model system of microtubules and molecular motors, as well as numerical modeling approaches. The defects characterizing chaotic flow are here curvilinear rather than point-like. We present a theoretical model predicting a certain class of closed disclination loops to be the system’s generic singularities. Through detailed analysis of experimental and numerically generated configurations, we show how our predictions of defect topology, geometry, and dynamics provide important insights into this highly complex 3D system.