Researchers Discover Odd Elasticity Emerges Naturally in Disordered Chiral Active Materials
Researchers have proposed a theoretical framework explaining how 'odd elasticity' — a non-conventional elastic response — arises in disordered chiral active materials such as the cytoskeleton and bacterial flagella clusters. The model uses micropolar (Cosserat) elasticity combined with local active torques to show that odd elasticity emerges as a nonlinear effect of internal particle rotations. The findings could advance understanding of mechanical behavior in biological systems that break both time-reversal and mirror symmetries.
A new theoretical study posted to arXiv proposes a minimal generic model for disordered 'odd solids' to explain how odd elasticity — a recently discovered elastic response unique to chiral active materials — can emerge in naturally disordered biological systems. Prior understanding of odd elasticity was limited to ordered structures such as engineered metamaterial lattices, leaving its microscopic origins in biological contexts unexplored. The model employs micropolar (Cosserat) elasticity with local active torques and finds that odd elasticity arises as a nonlinear consequence of internal particle rotations. When the disordered odd solid is coupled to an odd fluid, the authors identify new dynamically unstable regions driven by the solid-fluid interaction and, in the underdamped regime, by inertia as well. Notably, in the overdamped limit, this coupling permits bulk wave propagation near the unstable regions — a counterintuitive result. The work spans 23 pages with 6 figures and has undergone five revisions since its initial submission in August 2025, suggesting ongoing refinement. Potential applications include modeling the mechanics of the cytoskeleton, rotary bacterial flagella clusters, and self-spinning starfish embryos.
What's missing
The model is purely theoretical and analytical; experimental verification in actual biological systems (e.g., cytoskeletal networks or bacterial flagella clusters) has not been performed. The study does not address how sensitive the predicted instabilities and wave propagation are to realistic levels of biological noise or heterogeneity beyond the minimal model assumptions.
What different sources said
- arXiv physicsCenter
Odd elasticity in disordered chiral active materials
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