Dynamical Behavior of Defects in Circularly Patterned Active Nematics

Active nematics represent a new class of non-equilibrium systems that combine orientational ordering with active stresses applied to elongated particles. Continuum simulations of the active nematic are employed to explain how the interplay of activity-fueled energy injection to the system and frictional damping forces impact the dynamics of topologically imposed self-propelling +1/2 defects. We show that by patterning the activity by imposing active stresses in circular domains near the center of confinement, it is possible to regulate the motion of defects. A phase diagram of the dynamical response of defects based on activity strength and hydrodynamic friction is developed, revealing a wealth of new phenomena. Our results disclose that defects synchronize their dynamics to minimize the elastic distortion energy while being driven out of equilibrium by active stresses. A phase diagram is presented that displays a rich dynamical behavior, including immobile defects, steady rotation, bouncing defects, cruising defects, and a synchronized dancing state.