Organization of motile defects in active nematic solids

Motile topological defects are the hallmark of active nematic liquid crystals, where defect creation, motion and annihilation continuously remodel the texture and drive self-sustained active flows. Defects have also been shown to play an important role in the organization of epithelial tissue and in animal morphogenesis. In this talk I will describe topological defects in an active nematic elastomer – a solid-like materials where forces are generated internally by active processes. I will show that in these active solids defects can become motile through local melting of the nematic texture driven by strains induced by active stresses. Unlike in fluids, where defects are advected by active flows, this mechanism does not require flow of material as the defect move relative to the medium via local remodeling of the texture. Our work provides a natural framework for controlling structure and defects in active nematic solids and for understanding the observed restructuring of the nematic texture in Hydra.