Mysterious osmosis lets spiders weave graphene-reinforced webs
Thu 7 May 2015
An Italian research scientist has produced the strongest fibres ever measured simply by spraying spiders with carbon and graphene. Emiliano Lepore’s research [PDF] at the University of Trento has an almost Marvel-style simplicity that can only add to the current status of graphene as a font of endless wonders and industrial promise. But exploiting the apparently-simple osmosis may prove challenging.
Lepore ambiently sprayed 15 Pholcidae spiders with a solution containing carbon nanotubes and graphene flakes, first taking samples of the subjects’ webs as reference material. The post-spray webs the spiders produced match the tensile resilience of Kevlar 49.
Initially one might conclude that the ambient spray had contaminated the so-called ‘super webs’, but the team at Lepore’s laboratory found that reproducing this possibility in tests did not produce the same increase in tensile strength as the ingested-carbon webs.
Spiders’ dragline silk is already a marvel of nature in its unadulterated state, with a ductility that allows it to stretch to five times its natural length and a tensile strength comparable to high-grade alloy steel – all at a sixth of the density.
The cultivated carbon-webs have a fracture strength of 5.4 GPa and a toughness modulus approaching 2.1 GPa. Lenore’s team say in their research findings: “This is the highest toughness modulus for a fibre, surpassing synthetic polymeric high performance fibres (e.g. Kelvar49) and even the current toughest knotted fibers,”
The ease of the technique presents further possibilities for plant and animal-based adulteration with graphene substances, but there is a great deal more research to do to understand by what process the Pholcidae spiders have transmuted the ambient carbon and graphene into material that is bonded with their webs. Spider silk has long been of interest to research science, but the difficulties in harvesting it and the opacity of the biological processes that produce them have always sent science to analogous processes rather than direct exploitation. Some commenters on the research note that Lepore’s work could be further developed with the rather more amenable silk-worm.