Active Nematics Confined by Pillar Arrays

In active nematic microtubule (ANMT) systems, extensile dynamics at the scale of microtubule bundles lead to interesting coherent flows at large scales. For 2D ANMT systems, these flows are largely characterized by the dynamics of mobile, topologically-protected defects in the nematic director field. When confined to simple geometries, such as channels or the surface of a sphere, the positive defects move according to specific braiding patterns, which can be predicted from recent ideas in braid theory and dynamical systems theory. Motivated by these predictions for a doubly periodic domain, we consider the behavior of ANMTs confined to the space between a square array of pillars. We share the results of recent experiments using this domain geometry. In particular, we will consider the interesting transport behavior of defects that emerges due to the pillar array, and see if any evidence for the predicted braiding pattern exists.