Odd elasticity framework for cell monolayer mechanics

Cell monolayers are active materials with orientational order that exhibit exotic mechanical phenomena. Traditionally, hydrodynamic theories have captured mechanical anisotropy due to orientational order through active anisotropic stresses. In this work, we propose a minimal model for cell monolayer mechanics that encodes anisotropy through material properties, and show the existence of an odd modulus without chirality. Our model accurately reproduces the stress-strain focusing and cell accumulation-depletion observed experimentally near topological defects in various cell monolayers. Finally, we provide plausible microscopic mechanisms — based on non-reciprocal mechanosensitive mechanisms — that can give rise to a coarse-grained achiral odd modulus. Our findings offer an alternative to conventional active nematic models of cell monolayers, emphasizing the role of activity and anisotropic material properties.