Combination of Amorphous Silk Fiber Spinning and Postspinning Crystallization for Tough Regenerated Silk Fibers

Abstract

An artificial spinning system using regenerated silk fibroin solutions is adopted to produce high-performance silk fibers. In previous studies, alcohol-based agents, such as methanol or ethanol, were used to coagulate silk dope solutions, producing silk fiber with poor mechanical properties compared with those of native silk fibers. The alcohol-based coagulation agents induce rapid β-sheet crystallization of the silk molecules, which inhibits subsequent alignment of the β-sheet crystals. Here, we induce gradual β-sheet formation to afford adequate β-sheet alignment similar to that of native silk fiber. To this aim, we developed an amorphous silk fiber spinning process that prevents fast β-sheet formation in silk molecules by using tetrahydrofuran (THF) as a coagulation solvent. In addition, we apply postdrawing to the predominantly amorphous silk fibers to induce β-sheet formation and orientation. The resultant silk fibers showed a 2.5-fold higher extensibility, resulting in 1.5-fold tougher silk fibers compared with native Bombyx mori silk fiber. The amorphous silk fiber spinning process developed here will pave the way to the production of silk fibers with desired mechanical properties.

Influence of ethanol post-treatments on the properties of silk protein materials

“…There, ethanol takes water molecules from the protein, producing strong interaction between them than favors its rearrangement in regular array. This results in conformational transitions from amorphous to more crystalline structures [12,49,50].…”

Multiscale Hybridization of Natural Silk–Nanocellulose Fibrous Composites With Exceptional Mechanical Properties

“…Because of their excellent biocompatibility and biodegradability as well as intrinsic mechanical rigidity, various regenerated silk materials have received increased attention (Han et al, 2017;Magaz et al, 2018;Yazawa et al, 2018;Zhang et al, 2018). However, regenerated silk materials have a significant disadvantage in that they are difficult to scale up (Lee et al, 2018).…”

Wet‐Spinning Fabrication of Flexible Conductive Composite Fibers from Silver Nanowires and Fibroin

“…In contrast, RSF fibers can be effectively fabricated from acidic solvents such as FA and trifluoroacetic acid. 28 The fibroin acidic solution was stable and not sensitive to shear stress due to the interactions between the acidic solvents and hydroxyl groups on the fibroins. The fibroin acidic solution was created by directly dissolving fibroin films in acidic solvents with controllable fibroin concentrations.…”

“…However, the concentrated fibroin solution was unstable and gelled easily under the shear stress or extended time. In contrast, RSF fibers can be effectively fabricated from acidic solvents such as FA and trifluoroacetic acid . The fibroin acidic solution was stable and not sensitive to shear stress due to the interactions between the acidic solvents and hydroxyl groups on the fibroins.…”