Abstract
Enhancing toughness in nanocomposites often involves viscoelastic organic phases, but this typically reduces stiffness. We describe a high-modulus toughening mechanism in mature
Cristaria plicata
nacre arising from a crystalline organic-inorganic framework composed of aragonite nanorods alternately integrated with intratabular biomolecular crystallites. Due to the critical slip-length effect, these crystalline units approach the theoretical limits of modulus and strength. The nanoconfined biomolecular crystallites function as nanopins at interlamellar interphases, alleviating stress concentrations and enabling cross-scale synchronized deformation, thereby conferring high fracture toughness. Inspired by this mechanism, reconstituted nacre fabricated from regenerated aragonite flakes simultaneously achieved high stiffness and crack resistance. These insights offer a promising pathway toward reliable, high-performance structural materials.