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Issue 9, 2015
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Self-recovering caddisfly silk: energy dissipating, Ca2+-dependent, double dynamic network fibers

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Abstract

Single fibers of the sticky underwater larval silk of the casemaker caddisfly (H. occidentalis) are viscoelastic, display large strain cycle hysteresis, and self-recover 99% of their initial stiffness and strength within 120 min. Mechanical response to cyclical strains suggested viscoelasticity is due to two independent, self-recovering Ca2+-crosslinked networks. The networks display distinct pH dependence. The first network is attributed to Ca2+-stabilized phosphoserine motifs in H-fibroin, the second to Ca2+ complexed carboxylate groups in the N-terminus of H-fibroin and a PEVK-like protein. These assignments were corroborated by IR spectroscopy. The results are consolidated into a multi-network model in which reversible rupture of the Ca2+-crosslinked domains at a critical stress results in pseudo-plastic deformation. Slow refolding of the domains results in nearly full recovery of fiber length, stiffness, and strength. The fiber toughening, energy dissipation, and recovery mechanisms, are highly adaptive for the high energy aquatic environment of caddisfly larvae.

Graphical abstract: Self-recovering caddisfly silk: energy dissipating, Ca2+-dependent, double dynamic network fibers

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Article information


Submitted
03 Nov 2014
Accepted
11 Dec 2014
First published
11 Dec 2014

Soft Matter, 2015,11, 1667-1676
Article type
Paper

Self-recovering caddisfly silk: energy dissipating, Ca2+-dependent, double dynamic network fibers

N. N. Ashton and R. J. Stewart, Soft Matter, 2015, 11, 1667
DOI: 10.1039/C4SM02435D

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