Active nematics, or self-driven liquid crystals, are useful frameworks to model living matter. Two dimensional instances of these systems have been studied extensively over the past decade, owing to their captivating life-like animation and rich phenomenology. Findings from these works suggest that motion in two dimensional active nematics result from hydrodynamic instabilities that generate motile topologically charged point disclinations, and that the behavior of the resultant flows and defects can be controlled straightforwardly through confinement.

In this talk, I will demonstrate that three dimensional active nematics are strikingly different from their two dimensional counterparts. The possibility of twist deformations in 3D alters the topology of the fundamental excitations : while the fundamental excitations in 2D active nematics are point disclinations with winding number +/- 1/2, their counterparts in three dimensions are topologically neutral disclination loops. Further, the emergent flows in a confined 3D active nematic couple the effects of confinement in different dimensions, giving rise to a curious geometric criterion for self-pumping flows.