Stress-induced long-range ordering in spider silk

Abstract

The emergence of order from disorder is a topic of vital interest. We here propose that long-range order can arise from a randomly arranged two-phase material under mechanical load. Using Small-Angle Neutron Scattering (SANS) experiments and Molecular Dynamics based finite element (FE) models we show evidence for stress-induced ordering in spider dragline silk. Both methods show striking quantitative agreement of the position, shift and intensity increase of the long period upon stretching. We demonstrate that mesoscopic ordering does not originate from silk-specific processes such as strain-induced crystallization on the atomistic scale or the alignment of tilted crystallites. It instead is a general phenomenon arising from a non-affine deformation that enhances density fluctuations of the stiff and soft phases along the direction of stress. Our results suggest long-range ordering, analogously to the coalescence of defects in materials, as a wide-spread phenomenon to be exploited for tuning the mechanical properties of many hybrid stiff and soft materials.

Revealing Spider Silk's 3D Nanostructure Through Low Temperature Plasma Etching and Advanced Low-Voltage SEM

“…These properties are attributed to a hierarchical arrangement of ordered and disordered protein structures within a single fiber (Vollrath and Porter, 2009;Vollrath et al, 2011;Porter et al, 2013). This nanostructure has been extensively explored by bulk and space-averaging techniques such as calorimetry (Cebe et al, 2013;Vollrath et al, 2014;Holland et al, 2018a), spectroscopy (Dicko et al, 2007;Boulet-Audet et al, 2015) small angle scattering X-ray and neutron diffraction (Termonia, 1994;Riekel et al, 2000;Greving et al, 2010;Wagner et al, 2017) and solid state nuclear magnetic resonance (NMR) (Willis et al, 1972;Hijirida et al, 1996;Kümmerlen et al, 1996;Yang et al, 2000;Holland et al, 2008;McGill et al, 2018), which together have provided the fuel for a range of modeling approaches (Giesa et al, 2011;Cranford, 2013;Ebrahimi et al, 2015;Rim et al, 2017). In comparison, spatially resolved techniques are yet to be fully explored, but have already hinted at a diverse set of rich nano-and microscale features such as micelles (Lin et al, 2017;Oktaviani et al, 2018;Parent et al, 2018), nanofibrils (Wang and Schniepp, 2018), elongated cavities (Frische et al, 2002), and an overall radial variation of composition and structure (Li et al, 1994;Knight et al, 2000;Frische et al, 2002;Sponner et al, 2007;Brown et al, 2011).…”

Mechanical Properties of Dragline Silk Fiber Using a Bottom-Up Approach

“…Our previous study on the dragline spider silk showcased that long-range order arising from mechanical work performed on the material was vitally important to understanding of mechanics and properties of silk fibers [32]. In the present study, we have deduced a simple 3D fiber model to understand the unique mechanical properties of Araneus diadematus dragline silk using a bottom-up computational approach.…”

Soft Matter Sample Environments for Time-Resolved Small Angle Neutron Scattering Experiments: A Review

“…This requires the construction of a solid chamber around the moving parts. An example of this is the stress-induced long range ordering in spider silk [72]. Here a combination of finite element modelling and SANS data were used to elucidate the role that crystalline domains play in the ordering of silk when extended.…”

“…This requires the construction of a solid chamber around the moving parts. An example of this is the stress-induced long range ordering in spider silk [72].…”