Strain coupling drives defect dynamics in active nematic elastomers

Dynamic reconfiguration of nematic textures through defect creation, motion, and fusion has been shown to play an important role in animal morphogenesis. The tissues involved in these processes have solid-like properties on the timescale of the defect dynamics, suggesting they should be modeled as active nematic solids rather than their widely studied fluid counterparts. Motivated by recent experimental findings, we propose a minimal model for an elastic medium with an embedded nematic texture that generates active stress and, in turn, is coupled to elastic strain. We show that such coupling can drive +1/2 defect motion relative to the elastic medium by local remodeling of the nematic texture. This is in contrast to active nematic fluids where +1/2 defects are advected with the flow. In confined systems where a total defect charge is enforced through anchoring at the boundary, we find rich dynamics, including orbiting +1/2 defects and stabilized +1 defects that can spontaneously deform from asters/vortices to spirals. Taken together, our model reproduces defect behaviors observed in biological tissues such as regenerating Hydra spheroids. While the present work is limited to flat elastic sheets, allowing out-of-plane deformation is an exciting avenue for future research.