Super-Tough Silk: The Potential of Knots in Evolved Spiders

Abstract

Spider silk is renowned for its exceptional mechanical properties, combining low density with high tensile strength and high extensibility and thus very high toughness modulus (t., i.e., dissipated energy per unit mass). However, the potential toughness of spider silk can be significantly enhanced if spiders evolved the -currently absent/undiscovered- ability to tie knots in their silk. This advancement will allow for a new level of gigantic toughness (T) revealing today “hidden toughness”, mimicking human engineering techniques and in particular a related proposal by the author used for realizing the world's toughest fibers. Indeed, knotting can provide additional energy dissipation via friction, enabling spiders to construct webs and traps with unprecedented efficiency. To quantify this scenario, the author calculates the gigantic toughness of 393 real spiders virtually assumed with evolving knot-making behaviors, showing toughness gain (G = T/t) of about one or two orders of magnitude. The resulting “super-tough silk” can benefit spiders in their natural habitats and suggests a new perspective on how knotting can serve as a key innovation in spider evolution and in Biology in general.