While natural spider silk has proven superior in terms of its mechanical properties, researchers from the Graphene Flagship in Europe have found a way to boost its strength by using graphene-based materials, paving the way for a class of high-performance bionic composites.
The graphene-enhanced silk, which is produced naturally by the spiders, exhibit enhanced mechanical properties of up to three times the strength and ten times the toughness of the unmodified spider silks. This work was a collaboration between the University of Trento, and the Cambridge Graphene Centre at the University of Cambridge.
Scientists, acknowledging that natural materials can have properties that cannot be achieved with lab-produced materials, are expanding their research into artificially modified biological materials.
According to Nicola Pugno from the University of Trento, while humans have used silkworm silks for thousands of years, spider silk has been the focus of recent research due to its promising mechanical properties.
“It is among the best spun polymer fibres in terms of tensile strength, ultimate strain, and especially toughness, even when compared to synthetic fibres such as Kevlar,” Pugno said.
“We already know that there are biominerals present in the protein matrices and hard tissues of insects, which gives them high strength and hardness in their jaws, mandibles and teeth, for example. So our study looked at whether spider silk’s properties could be ‘enhanced’ by artificially incorporating various different nanomaterials into the silk’s biological protein structures,” said Pugno.
To enhance the spider’s silk, the researchers prepared solutions of graphene and carbon nanotubes (CNTs) which were sprayed within the enclosure the spiders were kept in. After allowing the spiders to ingest the graphene and CNT dispersions from their environment, silk was collected from the spiders and tested for graphene/CNT content and mechanical properties.
The biocomposite silk threads displayed significant increases in strength, toughness and elasticity. The strongest silk threads had a fracture strength of up to 5.4 GPa, over three times as strong as the unmodified silks. They also displayed a tenfold increase of their toughness modulus, up to 2.1 GPa.
This study opens up new potentials for tailoring the properties of biological materials to enhance their properties for use in novel applications. For example, these artificially modified silks could find use in high-performance or biodegradable textiles such as parachutes or medical dressings.
According to the researchers, the strength is comparable to that of the strongest carbon fibres or limpet teeth, and the results are proof of concept that will pave the way to exploiting the naturally efficient spider spinning process to produce reinforced bionic silk fibres.