Title:	Strain softening and stiffening responses of spider silk fibers probed using a Micro-Extension Rheometer†
Authors:	Dubey, Sushil Veer, Sukh Majumdar, Sayantan Pullarkat, Pramod A. +3 Co-Authors
Issue Date:	14-Jan-2020
Publisher:	Royal Society of Chemistry
Citation:	Soft Matter, 2020, Vol.16, p487
Abstract:	Spider silk possesses unique mechanical properties like large extensibility, high tensile strength, super-contractility, etc. Understanding these mechanical responses require 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 spiders 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 strain-softening response followed by 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 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 behaviour.
Description:	Restricted Access.
URI:	http://hdl.handle.net/2289/7412
ISSN:	1744-683X 1744-6848 (Online)
Alternative Location:	https://ui.adsabs.harvard.edu/abs/2019arXiv190801595D/abstract https://arxiv.org/abs/1908.01595 https://doi.org/10.1039/C9SM01572H
Copyright:	2020 Royal Society of Chemistry
Additional information:	Supplementary Information Available
Appears in Collections:	Research Papers (SCM)

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