Defect dynamics on active nematic ellipsoids

Living organisms are built from cells displaying all varieties of morphologies and textures that encode for specific functions and physical behaviors. In the current work, we build biomimmetic structural units by coating ellipsoidal droplets of smectic liquid crystal with an active nematic obtained from a cytoskeletal gel. As an extension to recent research on active spherical systems, we exploit the patterned structure and the anisotropic shape of the shells core to mold the complex nematodynamics of the interfacial active material. We show the existence of novel time-dependent states in which topological defects periodically oscillate between a rotational and a translational configuration. Continuum hydrodynamic simulation of active nematics further support that, beyond topology and activity, these behaviors are profoundly influenced by the geometric properties and the texture of the droplet, as well as by external hydrodynamic forces. Our results illustrate how incorporating new constrains to conventional nematic shells orchestrates remarkable spatiotemporal motifs, paving the way for the design of the next generation of bioinspired micro-machines.