Memory effect of spider major ampullate silk in loading-unloading cycles and the structural connotations

Area of Science:

• Materials Science
• Biomaterials Engineering
• Textile Science

Background:

• Spider silk undergoes repeated stretching during biological functions, closely relating fiber shape changes to mechanical properties.
• The influence of deformation and recovery time on spider silk's structure and tensile behavior after repeated stretching is not well understood.

Purpose of the Study:

• To investigate the effect of deformation and interval time on the structure and tensile behavior of major ampullate silk (MAS) after repeated stretching.
• To understand the mechanical memory and recovery mechanisms of spider silk.

Main Methods:

• Series of loading-unloading tests were conducted on MAS.
• Analysis of true stress-true strain curves to evaluate mechanical parameters evolution with cycle number.
• Investigation of recovery behavior after varying stretching strains and interval times.

Main Results:

• MAS reverts its tensile behavior independent of loading history after short intervals (8s to 5min).
• The true stress-true strain curve beyond a certain strain value is history-independent.
• Even after long intervals (≥1h), MAS can reproduce its last tensile behavior after one stretch.
• Elastic modulus increases with strain, while yield stress shows marginal variation across cycles.

Conclusions:

• Spider silk possesses a mechanical memory, enabling it to revert to a ground state and exhibit predictable tensile properties.
• Reversible changes in tensile behavior outside the elastic region are observed, attributed to viscoelasticity and combined deformation mechanisms.
• Findings offer insights for biomimetic design of novel fiber materials inspired by spider silk glands.