Caterpillars of a silkworm spin svekhprochny threads of silk after eating of carbon nanotubes

The silk used for production of beautiful and fashionable clothes is strong material. Scientists reported about development of the new method allowing to make thin silk threads is even stronger — by feeding to silkworms of a decanter or one-wall carbon nanotubes. The silk received thus can be used in production of especially strong protective fabrics, biodegradable medical implants and eco-friendly wearable gadgets, they say.

The silk used for production of beautiful and fashionable clothes is strong material. Scientists reported about development of the new method allowing to make thin silk threads is even stronger — by feeding to silkworms of a decanter or one-wall carbon nanotubes. The silk received thus can be used in production of especially strong protective fabrics, biodegradable medical implants and eco-friendly wearable gadgets, they say.

Researchers added the dyes, antimicrobic substances which are carrying out polymers and nanoparticles to silk earlier — or processing silk yarn special structures or adding them to food to larvae of a silkworm. Caterpillars of a silkworm spin silk threads from solution of a protein of the silk emitted by their salivary gland.

To receive the silk strengthened by carbon, the researcher Inin Zhang with colleagues from Qinghua University fed worms with the leaves of a mulberry or a mulberry tree sprayed by water solutions with content 0,2 percent of carbon nanotubes or a decanter and then collected silk after caterpillars weaved cocoons out of silk threads as it usually and becomes in silk production. For handling of ready yarn it is required to use the toxic chemical compositions with the nanomaterials dissolved in them therefore the method of feeding of a silkworm is more convenient and environmentally friendly.

The modified silk turns out almost twice stronger than regular and can sustain for 50 percent bigger stretching to a thread gap. Scientists heated silk fibers to temperature of 1050 °C for carbonization of protein of silk, and then studied its structure and measured conductivity. Such silk, unlike regular, was capable to install electrical equipment. The combinational spectroscopy and electronic microscopy showed that heavy-duty silk fibers have more ordered crystal structure at the expense of the built-in nanomaterials.

The number of questions remains without answer so far. One of them — how silkworms add nanomaterials to silk. Also it isn’t clear what percent of the nanomaterials eaten by larvae remains in silk instead of being removed from an organism or otherwise to be transformed in the course of a metabolism. Carbon materials can’t be found visually in sections of silk threads, it is possible because content of nanoparticles is very low, Zhang says. Biologists can find answers to these questions, she adds.

The expert in chemistry of polymers Qing Shen from Donghua university reported about carrying out a similar research in 2014 when for rising of strength characteristics of silk multiwall carbon nanotubes 30 nanometers wide were used. Zhang says that her team used single-layer nanotubes of the smaller sizes — from 1 to 2 nanometer wide which “are suitable for including in crystalline structures of proteins of silk better”.

This work offers “an easy way of receiving high-strength fibers of silk in large volumes” — the expert in materials science Yaopeng Zhang from Donghua university which fed silkworms with titanium dioxide nanoparticles says to frame the heavy-duty silk having fastness to decomposing under the influence of ultraviolet rays. According to him, conductivity of new silk does it suitable for creation of the sensors which are built in smart tissues for reading of signals of a nervous system.