As tough as spider silk

If you’re looking for a fibre that exhibits both high strength (it resists deformation) and high toughness (it’s hard to break) you need look no further than natural spider silk. It is much less dense than steel, for example, but a given weight of it is about five times as strong as the same weight of steel.

Creating synthetic fibres that have similar mechanical properties to spider silk has proved to be difficult, however.

In a paper published in the journal Science, researchers introduce a synthetic polymer yarn that’s approaching the spider-silk ballpark of mechanical properties.

The underlying findings could inform the design of similarly strong and tough polymer fibres useful in a wide variety of applications and areas, including biomedicine, space technology and textiles.

Study leader Xiaojian Liao, from the University of Bayreuth, Germany, and colleagues have developed a new fabrication process that addresses previous limitations to produce a polymer yarn with outstanding strength and toughness.

The research team electrospun polyacrylonitrile (PAN) co-methyl acrylate yarns, which were modified with a small amount of poly(ethylene glycol) bisazide (PEG-BA). Afterwards, the yarns were heat-stretched and allowed to cool slowly under tension.

According to the authors, this annealing process aligned the yarn’s small fibres and linked them together via the PEG-BA molecules, imbuing the yarn with properties comparable to those of spider silk.

“The properties achieved are groundbreaking and represent an important breakthrough in overcoming the trade-off between toughness and strength in fibres,” writes Bronwyn Fox, from Australia’s Swinburne University of Technology, in a related Perspective.

“The next challenge is to carbonise these electrospun multi-fibrillar yarns and measure the resulting carbon fibre properties. Combining a number of the aforementioned strategies could create a new generation of high-performance carbon fibres with unprecedented properties.”