The effect of using graphene, as well as carbon nanotubes, has been tested out in studies to show the tensile strength of the produced silk. The silkworm is the larva or caterpillar of the domesticated silk moth, Bombyx mori. The larvae prepare to enter the pupal phase of their lifecycle by enclosing themselves in a cocoon made of raw silk, which is produced by the salivary glands. The diet of the silkworm affects the quality of the silk, with the normal feed being white mulberry.
Looking for ways to make silk stronger, scientists from Tsinghua University in China found that this can be achieved by adding graphene or an alternative form of carbon to the food eaten by silkworms.
Graphene is a remarkable material. It is a two-dimensional form of carbon that is very strong, lightweight, conductive and transparent. One reason for graphene’s properties is due to the electrons in graphene not behaving as expected in a metal. Instead the electrons behave as they would in a fluid. This is thought to relate to graphene’s two-dimensional structure.
To add the material to the feed, the Chinese scientists sprayed a water solution containing 0.2 percent carbon nanotubes or graphene onto mulberry leaves. The larvae were then allowed to eat the leaves.
In studies the reinforced silk was shown to be capable of withstanding around 50 percent more stress than traditional silk. Microscopic analysis showed the silk to be formed from a more orderly crustal structure, compared with unmodified silk. The new silk also demonstrated conductive properties; when heated it was able to conduct electricity.
This is not the first attempt to experiment with silk. Different teams of researchers have added dyes, nanoparticles, conductive plastics and antibiotics to the feed of silkworms.
The research has been published in the journal Nanoletters. The research is titled “Feeding Single-Walled Carbon Nanotubes or Graphene to Silkworms for Reinforced Silk Fibers.”
