German scientists have added tiny amounts of metal to spider silk to make
it even stronger and more elastic. The technique could lead to the development
of super-tough textiles, surgical thread or artificial tissues such as bones
or tendons, the researchers say. Tough, lightweight materials could also be
useful for applications in fields as diverse as construction, aircraft technology
and space technology.
Spider silk is famously tougher and lighter than steel. In this latest study,
published in the journal Science, the researchers borrowed a trick from nature
with the goal of further enhancing the properties of this already remarkable
material.
Many insects and other creatures incorporate small amounts of metals such as
zinc, manganese, calcium or copper into body parts like jaws, claws and stingers
to make them stiffer and harder. The scientists drew on a technique called 'atomic
layer deposition' (ALD) to get zinc, titanium and aluminium ions into the spider
silk.
Normally ALD just leaves a layer of metal oxides on the surface of the treated
fibre; treating spider silk in this way therefore had little impact on its strength.
However, by adapting the technique slightly, the researchers were able to get
the metal ions to infiltrate the spider silk and become part of the thread.
Silk treated in this way is both stronger and more elastic than untreated silk;
according to the scientists, these properties mean it takes 10 times more energy
to break a treated thread than it does to break a natural, untreated thread.
'Our work promises great potential in terms of practical applications, as many
other biomaterials can be made more break-resistant and ductile using our method,'
explained Dr Mato Knez of the Max Planck Institute of Microstructure Physics
in Germany.
However, there is a catch: the technique only works on materials that are made
largely out of proteins. Even so, Dr Knez and his team have already used this
to their advantage - they succeeded in using the technique to strengthen threads
made of collagen, the protein that protects our bones from breaking and our
skin from tearing.
The exact mechanism by which the metal infiltrates the silk and makes it stronger
remains unknown. However, the scientists are not without ideas. 'We assume that
the metal atoms bind the protein molecules to each other,' Dr Knez speculates.
Usually, hydrogen atoms form the links between the different molecules that
make up spider silk. These hydrogen bonds probably weaken or break during the
ALD process, allowing the metal atoms, which create stronger bonds, to take
their place.
Dr Knez emphasises that metal-enhanced spider silk is unlikely to be used in
industrial applications in the near future; spiders are not easy to keep and
the amount of silk they produce is relatively small. Nevertheless, he is optimistic
that the new technique will lead to the development of new materials.
He concludes: 'We are pretty certain that we will also be able to improve the
properties of synthetic materials that imitate natural ones using our process.'
Source: Cordis
Posted April 25th, 2009
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