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BP: Fachverband Biologische Physik

BP 6: Active Matter II (joint session BP/CPP/DY)

BP 6.2: Vortrag

Montag, 17. März 2025, 15:15–15:30, H37

Defects in active solids: self-propulsion without flow — •Fridtjof Brauns¹, Myles O'Leary², Arthur Hernandez³, Mark Bowick¹, and Cristina Marchetti⁴ — ¹Kavli Institute for Theoretical Physics, Santa Barbara, USA — ²Princeton University, Princeton, USA — ³Leiden University, Leiden, the Netherlands — ⁴University of California Santa Barbara, Santa Barbara, California 93106, USA

Topological defects are a key feature of orientational order and act as organizing centers of orientation fields. Self-propulsion of +1/2 defects has been extensively studied in active nematic fluids, where the defects are advected with the fluid through the flow field they generate. Here, we propose a minimal model for defect self-propulsion in a nematic active solid: a linear elastic medium with an embedded nematic texture that generates active stress and in turn is coupled to elastic strain. We show that such coupling gives rise to self-propelled +1/2 defects that move relative to the elastic medium by local remodeling of the nematic texture. This mechanism is fundamentally different from the fluid case. We show that this mechanism can lead to unbinding of defect pairs and stabilize +1 defects. Our findings might help explain how orientational order, e.g. of muscle fibers, is reconfigured during morphogenesis in solid-like tissues. For instance, motility and merging of +1/2 defects play a crucial role in setting up the body axis during Hydra regeneration.

Keywords: active solid; topological defect; elasto-nematic coupling; morphogenesis