Strain softening and stiffening responses of spider silk fibers probed using a Micro-Extension Rheometer

Dubey, Sushil and Joshi, Chinmay Hemant and Veer, Sukh and Uma, Divya and Somanathan, Hema and Majumdar, Sayantan and Pullarkat, Pramod A. (2020) Strain softening and stiffening responses of spider silk fibers probed using a Micro-Extension Rheometer. Soft Matter, 16 (2). pp. 487-493. ISSN 1744-6848

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Abstract

Spider silk possesses unique mechanical properties like large extensibility, high tensile strength, super-contractility, etc. Understanding these mechanical responses requires characterization of the rheological properties of silk beyond the simple force–extension relations which are widely reported. Here we study the linear and non-linear viscoelastic properties of dragline silk obtained from social spider Stegodyphus sarasinorum using a Micro-Extension Rheometer that we have developed. Unlike continuous extension data, our technique allows for the probing of the viscoelastic response by applying small perturbations about sequentially increasing steady-state strain values. In addition, we extend our analysis to obtain the characteristic stress relaxation times and the frequency responses of the viscous and elastic moduli. Using these methods, we show that in a small strain regime (0–4%) dragline silk of social spiders shows a strain softening response followed by a strain stiffening response at higher strains (>4%). The stress relaxation time, on the other hand, increases monotonically with increasing strain for the entire range. We also show that the silk stiffens while ageing within the typical lifetime of a web. Our results demand the inclusion of the kinetics of domain unfolding and refolding in the existing models to account for the relaxation time behavior.

Item Type:	Article
Authors:	Dubey, Sushil and Joshi, Chinmay Hemant and Veer, Sukh and Uma, Divya and Somanathan, Hema and Majumdar, Sayantan and Pullarkat, Pramod A.
Document Language:	Language English
Subjects:	Natural Sciences > Physics Natural Sciences > Life sciences; biology > Physiology & related subjects Natural Sciences > Animals (Zoology)
Divisions:	Azim Premji University - Bengaluru > School of Arts and Sciences
Full Text Status:	Public
URI:	http://publications.azimpremjiuniversity.edu.in/id/eprint/7198
Publisher URL:	https://doi.org/10.1039/c9sm01572h

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