Self-Repair of a Biological Fiber Guided by an Ordered
Elastic Framework
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Abstract
Incorporating
sacrificial cross-links into polymers represents
an exciting new avenue for the development of self-healing materials,
but it is unclear to what extent their spatial arrangement is important
for this functionality. In this respect, self-healing biological materials,
such as mussel byssal threads, can provide important chemical and
structural insights. In this study, we employ in situ small-angle
X-ray scattering (SAXS) measurements during mechanical deformation
to show that byssal threads consist of a partially crystalline protein
framework capable of large reversible deformations via unfolding of
tightly folded protein domains. The long-range structural order is
destroyed by stretching the fiber but reappears rapidly after removal
of load. Full mechanical recovery, however, proceeds more slowly,
suggesting the presence of strong and slowly reversible sacrificial
cross-links. One likely role of the highly ordered elastic framework
is to bring sacrificial binding sites back into register upon stress
release, facilitating bond reformation and self-repair