Fatigueless response of spider draglines in cyclic torsion facilitated by reversible molecular deformation

Abstract

We demonstrate that spider draglines exhibit a fatigueless response in extreme cyclic torsion up to its breaking limit. The well defined Raman bands at 1095 and 1245 cm -1 shifted linearly towards lower wavenumbers versus increasing twist in both clockwise and counter-clockwise directions. Under thousands of continuous loading cycles of twist strain approaching its breaking limit, all the Raman bands were preserved and the characteristic Raman peak shifts were found to be reversible. Besides, nanoscale surface profile of the worked silk appeared as good as the pristine silk. This unique fatigueless twist response of draglines, facilitated by reversible deformation of protein molecules, could find applications in durable miniatured devices. V C 2014 AIP Publishing LLC.

Silkworm and spider silk electrospinning: a review

“…This absence of swinging reduces the risks of dislocations and ruptures inside the protein chains; hence, the spider thread keeps its integrity after torsion and can even endure several torsional stresses without losing its mechanical properties. Recent studies even suggest a fatigueless and superelastic behavior, where the original nanostructure and detorsion capacities remain unchanged after thousands of twisting spins per cm of thread (Kumar and Singh 2014 ). Number of twisting cycles at breaking point is the highest in spiral threads, followed by dragline (Kumar et al 2020 ).…”

How spiders hunt heavy prey: the tangle web as a pulley and spider's lifting mechanics observed and quantified in the laboratory

“…This means that Steatoda triangulosa did not stretch the silk's threads until large deformations and only the assumption of the linear regime was self-consistent with the experimental observations. It is possible that this occurs because silk threads deformed and kept in the linear elastic regimes are better in bearing loads cycles, with a small hysteresis [47][48][49][50]. This is beneficial for hunting mechanisms that involved extremely large prey that usually do not die immediately and, thus, fight for their lives.…”

Fatigueless structures inspired by nature: A case study

“…Materials cannot be immune from fatigue, but structures can. Dealing with biomimetic fatigue design, there are only very few but illuminating papers in the recent literature . Taking inspiration from the junction of a trunk and a branch and to the optimized design of a variable nonconstant notch radius, it has been recently shown in some preliminary investigations that the fatigue behavior can be substantially improved in the direction of an ideally fatigueless design, where the failure limit is only given by the material and not by the structure .…”

“…Taking inspiration from the junction of a trunk and a branch and to the optimized design of a variable nonconstant notch radius, it has been recently shown in some preliminary investigations that the fatigue behavior can be substantially improved in the direction of an ideally fatigueless design, where the failure limit is only given by the material and not by the structure . Spider draglines exhibit a fatigueless response under extreme cyclic torsion conditions at different scale levels . This unique twist response of draglines could find applications in durable and biocompatible miniatured devices.…”