Silk Versus Silk

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Spider silk is considered one of the strongest materials in nature – five times tougher than steel.

Despite the abundance of spiders in the world, though, it is not easy to collect large amounts of this silk for mass production.

But scientists in China recently found that the weaker silkworm’s silk could surpass that of the arachnid with a little tweaking, New Scientist reported.

In their study, a research team dissolved the insects’ silk in either sodium carbonate or papain – an enzyme from the papaya fruit. They then re-spun it in a bath of sugar, ethanol, and ions from zinc and iron.

When they tested the novel material, researchers found that the average force the silks could absorb without stretching – up to two gigapascals (GPa) – was almost 70 percent higher than the average from natural spider silk, which ranges between 0.9 and 1.4 GPa.

The new material has a higher Young’s modulus – a measure of how easily it can stretch – than any natural silk, indicating it is stiff rather than elastic.

Fritz Vollrath of the University of Oxford praised the findings but said caution was necessary, noting that the material made by the golden silk spider (Nephila clavipes) can reach tensile strengths of up to 2.9 GPa.

He also pointed out that artificial silk lacks the same unique qualities as real spider silk, such as its extensibility and also a variable amount of crystalline material – which can change its mechanical properties.

Vollrath said, “it’s a bit disingenuous to say, ‘now we’ve made a silk that is better than spider silk.’”