Active Solids: Topological Defect Self-Propulsion Without Flow

Area of Science:

• Soft Matter Physics
• Materials Science
• Biophysics

Background:

• Topological defects in active nematic fluids exhibit self-propulsion due to flow fields they generate.
• Understanding defect dynamics in solid-like active materials is crucial for biological processes.

Purpose of the Study:

• To propose and analyze a minimal model for self-propelled topological defects in nematic active solids.
• To elucidate the mechanism of defect motion in elastic media with active stress.

Main Methods:

• Development of a minimal theoretical model for a nematic active solid.
• Analysis of defect dynamics arising from the coupling of nematic texture and elastic strains.
• Investigation of defect pair unbinding and stabilization.

Main Results:

• Self-propelled +1/2 defects move by local nematic texture remodeling, independent of advection.
• This mechanism differs fundamentally from self-propulsion in active nematic fluids.
• The model predicts defect pair unbinding and stabilization of +1 defects.

Conclusions:

• Defect self-propulsion in active solids occurs via a novel mechanism of local texture remodeling.
• This mechanism offers insights into orientational order reconfiguration during morphogenesis, such as in muscle fibers.
• The findings may explain defect motility and merging in tissue regeneration, like in Hydra.