Silk and Web Synergy: The Merging of Material and Structural Performance

Abstract

Millions of years of evolution have adapted spider silks to achieve a range of functions, including the well-known capture of prey, with efficient use of material. From a materials perspective, the exceptional mechanical properties of self-assembling silk biopolymers have been extensively explored, both experimentally and in computational investigations. Yet few studies account for the structural function of silk within the web itself. Recently, a series of investigations have been conducted to examine structure-function relationships across different length scales in silk, ranging from atomistic models of protein constituents to the spider web architecture. Here, through theoretical and computational models, we attempt to reconcile the unique mechanical behavior of spider silk (i.e., material) with the performance of the web itself (i.e., structure), and elucidate the intimate and synergistic relationship between the two – the ultimate merging of material and structure. Particularly, we review recent analyses that considered an entire web structure subject to load, as well as the critical anchorage that secures the web to its (uncertain) environment. Beyond assessment of simple performance, we derive the theoretical basis for the underlying mechanics (through quantized fracture mechanics and the theory of multiple peeling, respectively). As such, the results can be translated to engineered structures in general, beyond the particular case of spider silks and webs. Interestingly, in both cases (web fracture and anchorage failure), the extreme hyperelasticity – i.e. elastic stiffening under large extension – benefits structural performance, in contrast to typical engineering practice (wherein large deformation is typically avoided). The spider web is a highly adapted system where both material and hierarchical structure across all length-scales is critical for its functional properties.