The spider fang is a natural injection needle, hierarchically built from a complex composite material comprising multiscale architectural gradients. Considering its biomechanical function, the spider fang has to sustain significant mechanical loads. Here we apply experiment-based structural modelling of the fang, followed by analytical mechanical description and Finite-Element simulations, the results of which indicate that the naturally evolved fang architecture results in highly adapted effective structural stiffness and damage resilience. The analysis methods and physical insights of this work are potentially important for investigating and understanding the architecture and structural motifs of sharp-edge biological elements such as stingers, teeth, claws and more.

Background and Aims Stomatal morphology and function have remained largely conserved throughout ∼400 million years of plant evolution. However, plant cell wall composition has evolved and changed. Here stomatal cell wall composition was investigated in different vascular plant groups in attempt to understand their possible effect on stomatal function. Methods A renewed look at stomatal cell walls was attempted utilizing digitalized polar microscopy, confocal microscopy, histology and a numerical finite-elements simulation. The six species of vascular plants chosen for this study cover a broad structural, ecophysiological and evolutionary spectrum: ferns (Asplenium nidus and Platycerium bifurcatum) and angiosperms (Arabidopsis thaliana and Commelina erecta) with kidney-shaped stomata, and grasses (angiosperms, family Poaceae) with dumbbell-shaped stomata (Sorghum bicolor and Triticum aestivum). Key Results Three distinct patterns of cellulose crystallinity in stomatal cell walls were observed: Type I (kidney-shaped stomata, ferns), Type II (kidney-shaped stomata, angiosperms) and Type III (dumbbell-shaped stomata, grasses). The different stomatal cell wall attributes investigated (cellulose crystallinity, pectins, lignin, phenolics) exhibited taxon-specific patterns, with reciprocal substitution of structural elements in the end-walls of kidney-shaped stomata. According to a numerical bio-mechanical model, the end walls of kidney-shaped stomata develop the highest stresses during opening. Conclusions The data presented demonstrate for the first time the existence of distinct spatial patterns of varying cellulose crystallinity in guard cell walls. It is also highly intriguing that in angiosperms crystalline cellulose appears to have replaced lignin that occurs in the stomatal end-walls of ferns serving a similar wall strengthening function. Such taxon-specific spatial patterns of cell wall components could imply different biomechanical functions, which in turn could be a consequence of differences in environmental selection along the course of plant evolution.

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Plant tissues are able to generate complex movements via shape modifications. These effects are tightly related to distinctive multi-scale composite architectures of the plant material, and can therefore largely be interpreted by composite mechanics principles. Here, we propose a generic framework for the analysis and prediction of the shape morphing of intricate biological composite materials, arising from changes in humidity. We have examined in depth the hierarchical structures of three types of seed pods for which we propose a theoretical scheme that is able to accurately simulate the relevant shape deformations. The validity and generality of this approach are confirmed by means of laboratory scale synthetic models with similar architectures leading to equivalent morphing patterns. Such synthetic configurations could pave the way to future morphing architectures of advanced materials and structures.

Ceramic composites found in nature, such as bone, nacre, and sponge spicule, often provide an effective resolution to a wellknown conflict between materials' strength and toughness. This arises, on the one hand, from their high ceramic content that ensures high strength of the material. On the other hand, various pathways are provided for stress dissipation, and thus toughness, due to their intricate hierarchical architectures. Such pathways include crack bridging, crack deflection, and delamination in the case of layered structures. On the basis of these inspiring ideas, we attempted here to create simultaneously strong and tough laminated alumina composite with high ceramic content. Composites were prepared from highgrade commercial alumina with spin-coated interlayers of ductile polymers (PMMA and PVA). The specimens' ultimate properties (strength, fracture toughness, and work of fracture) were measured by a four-point bending method. In some cases, fracture toughness of the composites was increased by up to an order of magnitude, reminiscent of the natural layered composites. It is proposed that this increase may be attributed to an interlocking mechanism, often encountered in biological composites. The significance of sample architecture and the role of the interfacial and bulk properties of the interlayer material are discussed. J ournalspicule. The structural architecture and interlayer adhesion will be viewed as variable parameters, the optimized values of which will hopefully lead to a tough and strong composite with high ceramic content. Emphasis is put here on the use of simple, affordable materials and techniques so as to demonstrate the universality and applicability of bioinspired toughening mechanisms. Supporting InformationAdditional Supporting Information may be found in the online version of this article:

In the absence of minerals as stiffening agents, insects and spiders often use metal‐ion cross‐linking of protein matrices in their fully organic load‐bearing “tools.” In this comparative study, the hierarchical fiber architecture, elemental distribution, and the micromechanical properties of the manganese‐ and calcium‐rich cuticle of the claws of the spider Cupiennius salei, and the Zn‐rich cuticle of the cheliceral fangs of the same animal are analyzed. By correlating experimental results to finite element analysis, functional microstructural and compositional adaptations are inferred leading to remarkable damage resilience and abrasion tolerance, respectively. The results further reveal that the incorporation of both zinc and manganese/calcium correlates well with increased biomaterial's stiffness and hardness. However, the abrasion‐resistance of the claw material cross‐linked by incorporation of Mn/Ca‐ions surpasses that of many other non‐mineralized biological counterparts and is comparable to that of the fang with more than triple Zn content. These biomaterial‐adaptation paradigms for enhanced wear‐resistance may serve as novel design principles for advanced, high‐performance, functional surfaces, and graded materials.