Spiders can spin several different types of silks, each with different properties and functions. To create the spokes that make up the main support structures of their webs, spiders use a type of silk known as dragline silk.
In a recent study published in the Journal of Applied Physics, a team of researchers at Tamkang University and National Yang-Ming University in Taiwan have used this silk to create biolenses that could be used alongside lasers to help create high-resolution images of the inside of the human body.
“Dragline silk is an interesting natural material because of its significant features, such as high elasticity, great toughness and large tensile strength,” said Prof Cheng-Yang Liu, one of the study’s coauthors and a researcher at National Yang-Ming University.
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“Compared to its weight, the strength of dragline silk is greater than steel.”
The team collected smooth, uniform dragline silk from Pholcus phalangioides, small spiders more commonly known as long bodied cellar spiders, and dripped a special type of resin onto the silk fibre which was set using an ultraviolet light.
As the resin condensed on the fibre, the silk naturally formed into a dome shape that they found could be used as a high-precision optical lens.
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By shining a laser onto the lens they were able to generate a type of beam that capable of providing large-area, high-resolution imaging for in a range of biomedical applications known as a photonic nanojet.
By varying the length of time the silk spent under the resin drip, the team were also able to alter the size of the dome, potentially allowing the photonic nanojets to be tuned for use in a range of imaging applications within biological tissue.
Reader Q&A: Why don’t spiders get caught in their own web?
Asked by: Regan Cook, via Twitter
Spiders only put glue droplets on some of their strands of silk, and they tend to avoid these as they move around their web. Spiders also only touch the web with the tips of their feet (‘tarsi’), which have a non-stick coating.
In addition, a special claw on the end of each foot grips the web and pulls it against springy hairs. When the claw is released, the springy hairs push the web strand away, stopping it from sticking.
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