Functionally-Graded Serrated Fangs Allow Spiders to Mechanically Cut Silk, Carbon and Kevlar Fibers.

Before humans and allegedly any animal group, spiders developed "functionally graded toothed blades" that cut one of the toughest biological materials: silk. Here, this work reveals the importance of micro-structured serrations in spiders' fangs that allow these animals to cut silk and artificial high-performance fibers, such as carbon or Kevlar. The importance of serrations revolves around the stress concentration at the interface between the fang and the fibers, resulting in a cutting efficiency superior to that of a razor blade.

Triclinic Metamaterials by Tristable Origami with Reprogrammable Frustration.

Geometrical-frustration-induced anisotropy and inhomogeneity are explored to achieve unique properties of metamaterials that set them apart from conventional materials. According to Neumann's principle, to achieve anisotropic responses, the material unit cell should possess less symmetry. Based on such guidelines, a triclinic metamaterial system of minimal symmetry is presented, which originates from a Trimorph origami pattern with a simple and insightful geometry: a basic unit cell with four tilted panels and four corresponding creases.

Air-encapsulating elastic mechanism of submerged blowballs.

In this article, we report the observation of an air-encapsulating elastic mechanism of Dandelion spherical seed heads, namely blowballs, when submerged underwater. This peculiarity seems to be fortuitous since is living outside water; nevertheless, it could become beneficial for a better survival under critical conditions, e.g.

Ceramics with the signature of wood: a mechanical insight.

In an attempt to mimic the outstanding mechanical properties of wood and bone, a 3D heterogeneous chemistry approach has been used in a biomorphic transformation process (in which sintering is avoided) to fabricate ceramics from rattan wood, preserving its hierarchical fibrous microstructure. The resulting material (called biomorphic apatite ​[BA] henceforth) possesses a highly bioactive composition and is characterised by a multiscale hierarchical pore structure, based on nanotwinned hydroxyapatite lamellae, which is shown to display a lacunar fractal nature. The mechanical properties of BA are found to be exceptional (when compared with usual porous hydroxyapatite and other ceramics obtained from wood through sintering) and unique ​as they occupy a zone in the Ashby map previously free from ceramics, but not far from wood and bone.

Micro-structured medium with large isotropic negative thermal expansion.

A challenge in nano- and micro-mechanics is the realization of innovative materials exploiting auxetic behaviour to tailor thermal expansion properties. For this purpose, a new class of micro-structured media possessing an extremely wide range of tunable (positive, negative or even zero) thermal expansion is proposed and analytically and experimentally assessed. For this class of isotropic media, the effective coefficient of thermal expansion is explicitly linked to two microstructural variables via a simple relation, allowing the design with desired values.