Tsinghua University’s team of researchers has discovered that supplementing the silkworms diet with an addition of graphene and carbon nanotubes, has caused them to produce silk which is stronger than it usually is. In the paper published for Nanoletters, the research team explains that the silk made by spinning threads of protein made from the salivary glands, is made 50% more stress resistant than silk produced on a normal diet.
Experiments on silkworms have been conducted to make silk stronger in the past – by treating the natural silk with harsh chemicals, dyes, nanoparticles, conductive plastics and even antibiotics. None of these methods were environmentally friendly, as this is often done by treating the silk product itself after the silkworms have produced it, with much waste generated during post-treatment.
To add the materials in this study, a pure water solution containing 0.2% carbon nanotubes and/or graphene was sprayed directly onto mulberry leaves. The silkworms were then allowed to grow and produce their silk cocoons as they normally would. Testing of the silks that were produced showed they could withstand approx. 50% more stress than traditional silk. Upon closer examination, the silk was actually made of a more orderly crystal structure than normal silk. Just to test the limits of this new silk, the team heated the silk to 1050°C, causing it to become carbonized – this caused the silk to become electrically conductive.
Combined with the 0.2% solution, heat-treatment, and ease of production (without harsh chemicals), this silk will create more protective fabrics, stronger medical implants, and perhaps clothed with embedded electronics.
More research needs to be done on exactly how the silkworms were able to convert the carbon nanotubes and graphene into silk, but initial results show promise of a new super-material.