Abstract: Nature often exhibits extraordinary properties that surpass those of individual components, inspiring the design of bioinspired materials with enhanced performance. Motivated by the painful experience of being pricked by the ultra-tough and sharp leaf tip of Agave striata (A. striata), we investigate its mechanical properties and microstructure to extract fundamental principles for designing strong and tough advanced materials from common elements. It reveals that the longitudinally aligned microfiber with a coaxial “brick-and-mortar” architecture, composed of alternating hard lignocellulose layers and soft viscoelastic biopolymer layers (∼300 nm in thickness), endows the leaf tip with exceptional mechanical properties, significantly outperforming natural wood and engineered wood-like materials. Specifically, the A. striata tip demonstrates threefold higher hardness and Young’s modulus, 2.5-fold greater compressive strength, and 17-fold superior toughness compared to basswood, a widely used structural wooden material with a similar composition. Mechanistically, the lignocellulose layers contribute strength and stiffness, while the biopolymer layers provide energy dissipation and deformation accommodation, resulting in a rare combination of strongness, toughness, and sharpness. The discovery of this coaxial brick-and-mortar architecture presents a novel strategy for engineering strong and tough nanocomposites and offers a design principle for advanced bio-inspired materials.

Key words: Natural leaves, Mechanical properties, Structure-property relationships, Bioinspired materials, Agave striata