Ultra strong pyroprotein fibres with long-range ordering

Area of Science:

• Materials Science
• Biomaterials Engineering
• Nanotechnology

Background:

• Silk's remarkable mechanical properties stem from its unique microstructure of aligned beta-sheet crystals within amorphous regions.
• Natural silks offer a promising foundation for advanced materials due to their inherent strength and extensibility.

Purpose of the Study:

• To significantly enhance the intrinsic mechanical and electrical properties of silk fibers.
• To investigate the transformation of silk's protein structure into an ordered carbon material.

Main Methods:

• Silk fibers underwent a simple heat treatment combined with axial stretching.
• Controlled heating and stretching induced the formation of poly-hexagonal carbon structures from beta-sheet crystals.
• Characterization of the resulting material's microstructure, mechanical strength, and electrical conductivity.

Main Results:

• A long-range-ordered graphitic structure was achieved by aligning carbon clusters derived from beta-sheets along the fiber axis.
• Mechanical properties were dramatically improved, with maximum strength and modulus reaching approximately 2.6 GPa and 470 GPa, respectively—surpassing raw silk by four and thirty times.
• The formation of sp2 carbon configurations led to a significant increase in electrical conductivity, reaching up to 4.37 × 10^3 S/cm.

Conclusions:

• Silk can be transformed into a high-performance carbon material with superior mechanical and electrical properties through controlled heat treatment and stretching.
• This method offers a scalable approach to creating advanced carbon-based materials from a natural, abundant resource.
• The resulting graphitic silk-derived material holds potential for applications requiring high strength, modulus, and electrical conductivity.