Spider silk boasts of amazing properties, such as being incredibly tough and never sagging even with intense, numerous stretching. Now, scientists have created an artificial version that could potentially serve soft robotics and biotechnology.

Researchers from the University of Oxford and Marie Curie University in France probed a spider’s "capture silk," the sticky silk composing the spiral of its web, not the radial spokes holding the structure together.

They found that the silk stretched like a spring, but stayed taut once compressed instead of sagging in the middle like any ordinary thread might. This phenomenon proved itself to be rather extraordinary.

"You can go up to 95 per cent and it remains taut, it seems to adapt its length. We know of materials that behave like this, but these are not solids, they are liquids," said study author Arnaud Antkowiak in a New Scientist report.

The capture silk adapts its size to the space that needs to be filled, like in the case of a soap film that is suspended in between two walls – the film contracting once the walls are brought together, and breaking if they are separated. These properties seem to be caused by a dual nature, where the spiral silk acts as a hybrid material comprising both solid and liquid.

The spider silk is made up of filaments decorated by tiny glue droplets, where the filament buckles as the silk becomes compressed and spools itself around the droplets as it keeps the thread taut overall.

The team mimicked the behavior and used plastic filaments that have been coated with liquids like silicone oil, producing a "liquid wire" technique akin to spiders' webs. Their laboratory-produced composite fibers, like the capture silk, appeared to extend like a solid and compress like a liquid. This provided insight into new bio-inspired technology.

"These new insights could lead to a wide range of applications, such as microfabrication of complex structures, reversible micro-motors, or self-tensioned stretchable systems," explained first author Dr. Herve Elettro, assuring that their hybrid threads could be created from virtually any component.

The team has experimented hundreds of times using various liquids and materials. They found that they could coil, buckle, and spool practically every filament enclosed in any droplet given that the drop’s capillary force went beyond the threshold for buckling of the thread, said Antkowiak.

Spider silk has been known to be an outstanding material for about four decades now, but continues to offer potential benefits in medicine, engineering, and material science.

The findings were published in the journal PNAS.

Photo: Ryan McDonough | Flickr

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