AsianScientist (Jun. 5, 2015) – Researchers have successfully prepared tough protein-carbon nanotube hybrid fibers which are comparable to natural spider silks. Their findings have been published in the Journal of Materials Chemistry B as the cover story.
Animal silks have been attracting a lot of attention in the biomedical field because of their excellent mechanical properties and good biocompatibility. However, the figure-of-eight spinning behavior of silkworms introduces defects in the fibers and is a major drawback in terms of the mechanical properties of silkworm cocoon silk.
In their previous research, a team led by Professor Chen Xin from Fudan University showed that silk fibroin fibers with controllable morphology and distinct structure could be produced by artificial spinning. In the present study, the team investigated whether adding carbon nanotubes to silk fibroin could help create stronger silk fibers.
By adding a small amount (less than one percent) of commercially available functionalized multiwalled carbon nanotubes to silk proteins, they were able to create protein-nanotube hybrid fibers that had a breaking energy comparable to that of spider dragline silk. The strongest of these fibers had a breaking stress of 0.42 gigapascal, breaking strain of 59 percent and breaking energy of 186 megajoule per m3.
Using the infrared beamline of the National Center for Protein Science Shanghai (NCPSS) located in the Shanghai Synchrotron Radiation Facility, the researchers were also able to obtain the β-sheet content of silk fibroin from a high-quality Fourier transform infrared (FTIR) spectrum. Their results showed that the β-sheet contents increase with the draw ratio in wet-spinning process and are obviously higher than that in the natural silkworm cocoon silk, thereby explaining the toughening mechanism.
The use of cheap silkworm proteins and commercially available functionalized carbon nanotubes paves the way for affordable super-strong materials.
The article can be found at: Fang et al. (2015) Tough Protein-carbon Nanotube Hybrid Fibers Comparable To Natural Spider Silks.
Source: Shanghai Institutes for Biological Sciences.
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