Basic Principles in the Design of Spider Silk Fibers

Abstract

The prominence of spider silk as a hallmark in biomimetics relies not only on its unrivalled mechanical properties, but also on how these properties are the result of a set of original design principles. In this sense, the study of spider silk summarizes most of the main topics relevant to the field and, consequently, offers a nice example on how these topics could be considered in other biomimetic systems. This review is intended to present a selection of some of the essential design principles that underlie the singular microstructure of major ampullate gland silk, as well as to show how the interplay between them leads to the outstanding tensile behavior of spider silk. Following this rationale, the mechanical behavior of the material is analyzed in detail and connected with its main microstructural features, specifically with those derived from the semicrystalline organization of the fibers. Establishing the relationship between mechanical properties and microstructure in spider silk not only offers a vivid image of the paths explored by nature in the search for high performance materials, but is also a valuable guide for the development of new artificial fibers inspired in their natural counterparts.

Rapid molecular diversification and homogenization of clustered major ampullate silk genes in Argiope garden spiders

“…Recent comparisons among Entelegynae spiders [ 32 , 127 ] indicate that A . aurantia has the lowest degree of crystallinity (the ratio between crystalline and amorphous phases) that results in elevated levels of nanostructure disorder.…”

“…ventricosus MaSp2 genes. Recent experiments examining changes in the microstructure of dragline silk fibers under stress suggest an increase in the crystalline phase as the fiber stretches [ 127 , 130 ]. This transformation does not appear to be tied to the poly-A nanocrystal sheets but results from the formation of new crystalline structures that provide additional strength during the latter stages of strain.…”

Differences in the Elastomeric Behavior of Polyglycine-Rich Regions of Spidroin 1 and 2 Proteins

“…Supercontraction was initially defined by a significant reduction in the length of MAS fibers spun by orb-weaving spiders when immersed in water [ 40 , 41 ] and was found to be intimately connected with the appearance of elastomeric tensile properties when the material was tested under this condition [ 42 , 43 ]. Thus, the existence of a network of elastomeric chains was established as one of the three basic microstructural features that constitute the basic design elements of MAS fibers [ 36 , 37 ], along with β-nanocrystals [ 44 , 45 ] and an additional network of hydrogen bonds in the dry fiber that collapses when immersed in water [ 46 ].…”

Spider Silk-Improved Quartz-Enhanced Conductance Spectroscopy for Medical Mask Humidity Sensing

“…This rearrangement results in the phenomenon of supercontraction that will change the modulus of the spider silk [11,12]. The spider silks are widely used in optical systems [13], the synthesis of new materials [14,15], biomedical applications [16][17][18][19][20][21] and tensile mechanics [22][23][24][25][26]. Spider silk also exhibits powerful cyclic contractions, which can be reversible and have reproducible use [9,27].…”