Polymer Journal |  October 01, 2020

Aqueous spinning system with a citrate buffer for highly extensible silk fibers

Authors: Jianming Chen1, Yoshinori Ohta1,2, Hiroyuki Nakamura2, Hiroyasu Masunaga3, Keiji Numata1,4*

DOI: 10.1038/s41428-020-00419-1

  • 1. Biomacromolecules Research Team, RIKEN Center for Sustainable Resource Science
  • 2. Spiber Inc.
  • 3. Japan Synchrotron Radiation Research Institute
  • 4. Department of Material Chemistry, Kyoto University


Inspired by the natural spinning process, we developed an aqueous wet spinning system using a citrate buffer with polyethylene glycol (PEG), where the citrate buffer served for ion exchange and acidification and the PEG functioned for dehydration. This biomimetic condition induced the formation of solid fibers with a core–shell structure. The PEG layer could be subsequently removed by the equipped water bath, resulting in amorphous silk fibers. Due to the amorphous state, the silk fibers could be stretched at up to 12 times the original reel speed. Eventually, the mechanical properties featured an extraordinary extension of ~100% and a toughness of ~70 MJ/m3. The crystalline state of the resultant fibers was characterized by synchrotron WAXS to determine the degree of crystallinity and orientation of the beta-sheet structure. Interestingly, the citrate buffer-mediated spinning system enabled tuning of the induction of crystallization by changing the citrate buffer concentrations and coagulation time. The current amorphous spinning of regenerated silk fibers provided indepth insights into the green and sustainable fabrication of artificial capture-silk-like fibers with unique extensibility and toughness.

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本研究の遂行に際し、当社は 内閣府 革新的研究開発推進プログラム(ImPACT)「超高機能構造タンパク質による素材産業革命」の助成を受けました。