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Molecular origin of anisotropic shear elastoplasticity in chitin

Wan, Zhangmin [University of British Columbia, Vancouver, BC, Canada] (ORCID:0000000311780308)·Lu, Yi [Bioproduct Institute, Department of Chemical and Biological Engineering, The University of British C]·Yu, Yan [ORNL]·Niu, Xun [Bioproduct Institute, Department of Chemical and Biological Engineering, The University of British C]·Zhou, Chris [Department of Chemical and Biological Engineering, The University of British Columbia, Vancouver, BC]·Yan, Yancun [Department of Wood Science, The University of British Columbia, Vancouver, BC, V6T 1Z4, Canada]·Smith, Jeremy [ORNL] (ORCID:0000000229783227)·Srebnik, Simcha [Department of Chemical and Biological Engineering, The University of British Columbia, Vancouver, BC]·Rojas, Orlando [University of British Columbia, Vancouver, BC, Canada] (ORCID:0000000340364020)
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Abstract

Chitin nano- and mesoscale structures present in the exoskeleton of crustaceans exhibit exceptional longitudinal stiffness and toughness, rivaling or even exceeding that of many synthetic polymer architectures. Here, we reveal the origin of the asymmetric shear response in chitin multiscale architectures, marked by pronounced anisotropy in deformation. Under shear aligned with the molecular axis, chitin accommodates strain through coherent atomic rearrangements that enable elastic recovery. In contrast, shear applied perpendicular to this axis induces liquid-like plasticity via localized sliding. These results demonstrate the intrinsic mechanical anisotropy of chitin, underpinning a dual function in resisting repetitive loading while dissipating internal stress during high-strain events. Our findings establish the molecular basis of shear elastoplasticity in multiscale chitin structures, wherein axial elasticity supports energy storage in load-bearing regions, whereas transverse plasticity enables controlled energy dissipation. These atomic-scale insights lay a foundation for the predictive design of chitin-based materials with tunable strength-toughness profiles.

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Wan, Zhangmin [University of British Columbia, Vancouver, BC, Canada] (ORCID:0000000311780308), Lu, Yi [Bioproduct Institute, Department of Chemical and Biological Engineering, The University of British C], Yu, Yan [ORNL], Niu, Xun [Bioproduct Institute, Department of Chemical and Biological Engineering, The University of British C], Zhou, Chris [Department of Chemical and Biological Engineering, The University of British Columbia, Vancouver, BC], Yan, Yancun [Department of Wood Science, The University of British Columbia, Vancouver, BC, V6T 1Z4, Canada], Smith, Jeremy [ORNL] (ORCID:0000000229783227), Srebnik, Simcha [Department of Chemical and Biological Engineering, The University of British Columbia, Vancouver, BC], Rojas, Orlando [University of British Columbia, Vancouver, BC, Canada] (ORCID:0000000340364020). 2026-08-01. Molecular origin of anisotropic shear elastoplasticity in chitin. https://doi.org/10.1126/sciadv.adz6220

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