Novel Defect Dynamics in Confined Chiral Active Liquid Crystals

Chiral structures and dynamics are ubiquitous in active and living systems, ranging from chiral biomolecules to helical flagella and the circular motion of microswimmers near surfaces. However, the effect of chiral activity in dense and confined active matter remains largely unexplored. Here we adopt a hydrodynamic model to investigate the dynamics of +1/2 defects in a confined chiral active nematic (CAN) and between CAN droplets. By tuning linear and chiral activity parameters for a CAN confined to a disk, we obtain a rich dynamic mode diagram for the two +1/2 defects, including spirograph, steady rotation, circularly advancing, stable lattice, and active turbulence modes. Our agent-based model can faithfully reproduce various defect modes. We further study two nearby CAN droplets, and find that their hydrodynamic interactions play a crucial role in mediating the synchronization and anti-synchronization of their defects in different dynamic modes. These interactions also dictate the attractive or repulsive forces between the two droplets. Therefore, our work provides important insights into the defect dynamics in confined chiral active liquid crystals, which will be heuristic for understanding the dynamic behaviours of chiral active matter in biological and synthetic contexts.