Silk fibers fibrillation

A trademark of amyloid fibrils is their cross-/ structure. This structure is the basis of the repetitive hydrogen-bonding extension of the fibril (Makin et al., 2005). Cross-/ structures are observed in the silk fibers of some insects (Geddes et al., 1968 Hepburn et al., 1979), although none are observed in spiders or lepidoptera (Craig, 1997). This absence has been explained by the possibility that cross-/ silks or a-silks may be converted into collinear /1-silks by stretching the fiber and an increased orientation-function correlated to the speed at which silk is formed (Riekel et al., 2000). 

In comparison to Reference Silk and Historic Silk fibers, the Marine Silk fibers show more extensive morphological damage with deep cracks, surface striations, fibrillation, and fiber flattening. These changes in morphology, combined with the increased diameter of two of the Marine Silks, reflect changes in the physical microstructure of the artifacts as a result of the deep ocean environment. 

Correspondingly, AFM and scanning electron microscope (SEM) results show that both spider and silkworm silk fibers are composed of numerous nano fibrils of diameter about 20-30nm, which are separated into crystalline and non-crystalline... 

Both stretched and unstretched silk threads from the Black Widow spider were imaged. Two types of fibers were observed within the threads (thicker, 300 nm in diameter, oriented parallel to the thread axis thinner, 10-100 nm fibrils oriented across the thread axis). With increasing strain, mean fiber and fibril diameters were found to decrease and fibrils aligned themselves more closely with the thread axis. The authors were able to relate these structural features to models of secondary and tertiary structure and organization in spider silk (77). 

Bico technology can also be used to form composite fibers that can be broken apart, by using pol5miers with poor mutual adhesion (eg, polyolefin and PET). A fiber made with a dozen or more segments, alternating between two polymer types, can be post-processed to form separated fibrils of the two different materials. The shapes of the fibrils can affect the aesthetics of the fabrics, for example, sharp edges on the fibrils confer crispness and the soimd of silk to fabrics. 

The hierarchically built fiber is produced by the assembly of silk proteins through the spider s sophisticated spinning spinneret [9]. The silk assembly process occurs via a lamellar liquid crystalline assembly into nano fibrils to form the final silk thread (Figure 6.3). A diagrammatic optical section of the secretory part (A- and... 

Increasing reeling speed can produce stronger but less extensible fibers (Figure 6.7). As the crosslinks connecting protein chains in silk fibrils (see Figure 6.2), P-crystaUites play important roles in determining mechanical properties of silk. The size and orientation of the crystallites as well as the... 

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