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Natural polymeric materials are an attractive potential replacement for non‐biodegradable plastics. However, one of the main challenges for high‐end applications of these materials, is to maintain their high mechanical properties in a watery environment. Here, inspired by the reinforcement principle of multiscale architecture in natural crab exoskeletons, an ultra‐strong and hydrostable film is developed through a top‐down method directly from the crab shell. The resulting chitosan film exhibits an outstanding isotropic tensile strength of ≈220 MPa and a superior wet strength of ≈70 MPa, which is significantly higher than that of conventional polysaccharide‐based materials and many commercially used plastics. Its excellent mechanical properties are due to the realization of strong interactions between chitosan fibrils even in wet conditions through interdigitation and densification processes without other additives. Additionally, it also possesses outstanding transparency, flexibility, antimicrobial ability, and biodegradability, making it a promising high‐performance and eco‐friendly material for many potential applications. [ABSTRACT FROM AUTHOR]

The interest in soft elastomers has been revived because they are needed in the emerging soft robotics and wearable devices. It is imperative to adjust the mechanical properties of elastomeric materials for real‐life applications as well as to develop an approach to construct more complex and customized architectures. In this study, an embedded extrusion‐based three‐dimensional (3D) printing method was used to prepare silicone elastomeric composites. Cellulose nanocrystals were introduced to tailor the rheology of the ink and serve as reinforcements after solidification. The printing paths were carefully designed to write Bouligand structures, which have been widely found in arthropod cuticles and fish scales because of their exceptional damage resistance. Compared with the pure elastomer and randomly distributed composites, the 3D‐printed elastomeric composites with bioinspired structures exhibited simultaneously enhanced stiffness, extensibility, and toughness. This strategy may be extended to the realization of other biomimetic designs and paves the way for soft material manufacturing. [ABSTRACT FROM AUTHOR]

Here, experiments and analysis revealing the unique defense mechanisms of the coelacanth, a lobe‐finned fish termed a "living fossil", are reported, as it was considered to be extinct until 1938, but extant for 400 million years. This defense is provided by primitive elasmoid scales having a rare double‐twisted Bouligand structure of lamellae which provides extraordinary resistance to deformation without failure. Distinct from other elasmoid scales, the collagen fibrils in the coelacanth fish scales form bundles which are embedded in a matrix comprising fibers arranged perpendicular to the layered (double‐twisted Bouligand) structure that provide added rigidity and resistance to deformation. Using in situ synchrotron small‐angle X‐ray scattering during uniaxial tensile testing, the deformation mechanisms of the collagen are identified in terms of fibril stretching, reorientation, sliding, bending, and delamination. The unique structure of the coelacanth scales, distinct from modern elasmoid scales such as the carp, provides a variety of mechanisms to arrest cracking, making it an outstanding damage‐tolerant material to resist predator attacks. The unique double‐twisted Bouligand structure of the scales of the "living fossil" coelacanth fish is examined. Combining ex situ and in situ scanning electron microscopy experiments, coupled with small‐angle X‐ray scattering analysis, the mechanical behavior and in particular the toughening mechanisms are uncovered for this ancient armor. The findings may potentially provide insight for improving the penetration resistance of new engineering structural materials. [ABSTRACT FROM AUTHOR]