Control of Topological Defects and Spontaneous Flows in Engineered Active Liquid Crystals

Active matter gives rise to intriguing spontaneous flows and motion whose collective behavior is difficult to steer and tailor, thereby placing limits on potential applications. Here, we present a new method to control the dynamics of an active liquid crystal. Theory shows that through the interplay of local active stresses it is possible to create anchoring effects that help confine activity-induced topological defects. This prediction is confirmed by hydrodynamic simulations of active nematics. Simulations further demonstrate that at moderate-to-high activity, local active stresses can be used to create defect pairs at will and direct the motion of +1/2 defects on demand; at low activity, such stresses can induce a spontaneous flow without strong elastic distortions of the nematic. Our calculations are compared to experiments of a flexible active liquid crystal.