Surprisingly strong: Spider silk after MPI treatment, lifting a weight of 27.5 g on a hook.
Credit: Max-Planck-Institute of Microstructure Physics
SYDNEY: Adding small amounts of metal to spider silk – a material already stronger and lighter than steel – makes it up to 10 times tougher, German researchers report.
The scientists devised a way to incorporate zinc, titanium and aluminium ions into natural spider silk. They say the method could one day prove useful for creating super-strong textiles, surgical thread or even synthetic bones.
"We might be able to use the process to toughen artificial materials," said co-author Mato Knez, based at the Max Planck Institute of Microstructure Physics in Halle.
Atomic layer deposition
Nature has already taken advantage of the strength metal ions can provide. Tiny amounts can be found in jaws, stingers, claws, and other composite materials that need to be hard or resilient.
The German team – whose research is reported in the U.S. journal Science today – achieved a similar effect in spider silk. They added metal to the silk fibres by modifying a method called atomic layer deposition (ALD).
ALD is usually used for coating solid materials. The material is alternately exposed to two different gases that react strongly with each other.
The first gas is added and removed, with one layer of molecules remaining on the material's surface. The second gas is then added, and it reacts with those molecules to form a coating on the material.
Multiple applications
"You can repeat this cycle to obtain a layer by layer growth of the coating," said Knez.
For the spider silk experiments, the researchers extended the exposure time of the gases. Instead of simply coating the fibres, the metal ions penetrated them and reacted with their protein structure.
The researchers tested the modified spider silk and found its mechanical properties were superior to those of the natural fibres.
However, tougher spider silk is not the main idea, Knez said. "The more interesting point is that we are able to improve the characteristics of protein-based materials," he said.
He hopes to apply the method to other proteins. Already the researchers have adapted the process to strengthen collagen fibres.
John Ramshaw, a protein chemist with Australia's government research body, the CSIRO, in Clayton, Victoria, said the new method could work with other natural materials, although further testing would be necessary.
"It will be interesting to see if the metal-modified materials are durable and that if the method can be taken to a commercial scale that will be cost effective," he said.
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