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Spider-Man silk from Halle

Scientists are making webs more tear-resistant and elastic

CARSTEN HECKMANN

Webs have amazing properties. They are extremely strong and yet still elastic. But even something good can be improved on. Dr. Mato Knez and his team at the Max Planck Institute for Microstructure Physics have added small amounts of metal to the spider's silk. This means that triple the amount of weight can hang on this treated silk. Other fibres may also be able to be made stronger using this method. MLU scientists cut the silk into 100 nanometre thick slices for their investigation.

Garden spider in the middle of its web. Photo: Max Planck Institute for Microstructure Physics

New York. He has probably never heard of the laid-back city of Halle on the Saale. However he may be fiercely interested in the outstanding research which has been accomplished at the Weinberg Campus. Did Peter Parker, who was bitten by a radioactive spider when he was young, endowing him with special powers, develop a web sprayer that would enable him to weave various types of spider webs in the blink of an eye to hunt down criminals?

Spider-Man, the well-known name given to this man, has a particularly tear resistant web at his disposal whose secrets have not yet come to light. A major competitive edge for the superhero.  Yet this may soon become passé.

Because Dr. Mato Knez from the Max Planck Institute for Microstructure Physics might now also be able to stop a fleeing car travelling at 100 km per hour - at least in theory. A five millimetre thick thread would be enough at a distance of 20 metres. A natural spider's web, strengthened by metal. Knez and his research team have been able to considerably improve the mechanical properties of the spider's web. The treated material can withstand strong tension and hefty stretching and can absorb ten times more energy than its natural counterpart before it tears.

Spider’s web holding up a 27.5 gram block on a hook that has been wound four times and infiltrated. Image: Max Planck Institute for Microstructure Physics

Scientists have added the metals using a special infiltration method (Multiple Pulsed Vapour Phase Infiltration). Using electromicroscopic images, some of which were taken at the Institute of Physics at MLU, the scientists are obtaining clues as to how the metal atoms penetrate into the interior of the spider's silk and why this give the threads more strength. Proper sample preparation is indispensible for this. "You have to avoid so-called preparation artefacts," says Dr. Gerd Hause, department head of "Imaging Techniques" at MLU's Biocentre. "The artefacts would lead to images that do not correspond to reality." Hause and his colleagues have added their expertise to Mato Knez's project. They prepared the modified spider's threads so that they could be moulded into epoxy resin blocks at the end. This made it possible to cut them into 100 nanometre thick slices.

The results of the investigation, published in "Science", make the scientists optimistic about its further development and practical relevance. However spider's silk treated with metal is not going to raise elevators or strengthen bearing surfaces in the future according to Mato Knez. "It is probably nearly impossible to produce spider's silk in large quantities." But with this applied method, other biomaterials can be made more tear-resistant and elastic. "We are also counting on being able to improve the properties of synthetic materials that imitate natural ones with our method." Applications in the aeroplane, automobile or space industry are imaginable. The decisive material properties are: light, strong and flexible.

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