The "Egg of Columbus" for Making the World’s Toughest Fibres

In this letter we present the "Egg of Columbus" for making fibres with unprecedented toughness: a slider, in the simplest form just a knot, is introduced as frictional element to dissipate additional energy and thus demonstrating the existence of a previously "hidden" toughness. The proof of concept is experimentally realized making the world’s toughest fibre, increasing the toughness modulus of a commercial Endumax macroscopic fibre from 44 J/g up to 1070 J/g (and of a zylon microfiber from 20 J/g up to 1400 J/g). The ideal upperbound toughness is expected for graphene, with a theoretical value of 10^5 J/g. This new concept, able of maximizing (one fold increment) the structural robustness, could explain the mysterious abundance of knot formations, in spite of their incremental energy cost and topological difficulty, in biological evolved structures, such as DNA strands and proteins

A New Concept for Smart Drug Delivery: Adhesion Induced Nanovector Implosion§

In this paper we show that controlling adhesion in highly flexible nanovectors can help in smartly delivering the drug. The high flexibility of the nanovector is used to smartly deliver the drug only at the target site by the new concept of “adhesion induced nanovector implosion”; a liquid drop analogy is developed for the calculations

Strong and Tough Silk for Resilient Attachment Discs: The Mechanical Properties of Piriform Silk in the Spider Cupiennius salei (Keyserling, 1877)

Spiders are able to produce different types of silk with different mechanical and biological properties. Piriform silk is produced to secure spiders and their webs to surfaces by using a nano-fibril network embedded in a cement-like matrix. Despite their fundamental role, the mechanical properties and function of these anchorages are still poorly understood due to the practical difficulties in nano-fibril sample preparation, the complexity of the system, and the high variation of attachment disc structures. Here we estimated the mechanical properties of this nano-fibril silk and those of the whole silk membrane in the large wandering spider Cupiennius salei through a combination of nanoindentation and nanotensile techniques and with the support of a simple analytical model. The results highlight the mechanical properties of the piriform silk, facilitating the modeling of silk composite mechanics. This could inspire the design of more efficient bio-inspired adhesives and fabrics

Systematic numerical investigation of the role of hierarchy in heterogeneous bio-inspired materials

It is well known that hierarchical structure is an important feature in biological materials to optimise various properties, including mechanical ones. It is however still unclear how these hierarchical architectures can improve material characteristics, for example strength. Also, the transposition of these structures from natural to artificial bioinspired materials remains to be perfected. In this paper, we introduce a numerical method to evaluate the strength of fibre-based heterogeneous biological materials and systematically investigate the role of hierarchy. Results show that hierarchy indeed plays an important role and that it is possible to “tune” the strength of bio-inspired materials in a wide range of values, in some cases improving the strength of non-hierarchical structures considerably

An Experimental Study on Adhesive or Anti-adhesive, Bio-inspired Experimental Nanomaterials

Adhesive abilities of insects, spiders and reptiles have inspired researchers for a long time. All these organisms show outstanding performance, particularly for force, adhesion and climbing abilities, relative to their size and weight. Scientists have focused on the gecko’s adhesive paw system and climbing abilities. Its adhesion mechanism has been an important topic of research for nearly 150 years. However, certain phenomena of geckos are still not fully understood and represent today the main challenge in several scientific discussions that aim to better understand their adhesive ability. The manuscript deals with the influence of surface roughness on the gecko’s adhesion on the inverted surface of Poly(methyl meth-acrylate) (PMMA) and glass, of PMMA with different surface roughness, on the gecko’s maximum normal adhesive force. In general, the adhesive structure and mechanism of an animal could be connected to the micro-structured roughness of natural substrata (e.g. plant surfaces) in the natural environment. This manuscript focuses on the nanometer scale, which is involved in everything from gecko spatulae to the waxy nanotubules of the lotus leaf, to the fibroin protein materials that constitute spider silks. In general, spider silks display superior mechanical properties, but only in the last few decades, researchers investigated various types of silks and evaluated their very different mechanical properties. The dragline and the flag silks (or radial and circumferential) of orb weaving spiders have been characterized in scientific literature while, to our knowledge, few studies have been conducted on bundles, which connect the cocoons of Meta menardi to the ceiling of caves