For an arachnophobe, the sight of a spider making its way up a wall sparks fear. For a materials scientist, however, it can provide inspiration. In the current issue of the journal Smart Materials and Structures, researchers describe just how a spider manages to stick to ceilings in apparent defiance of gravity. The discovery could point the way to novel adhesives.

“We carried out this research to find out how these spiders have evolved to stick to surfaces, and found that it was all down to a microscopic force between molecules,” says lead author Antonia Kesel of the Institute of Technical Zoology and Bionics in Germany. Using a scanning electron microscope, the team obtained images of the foot of a jumping spider (Evarcha arcuata).



The spider’s ability to cling, the team reports, stems from tiny hairs called setules that cover larger hairs comprising a tuft on each foot. The researchers then used atomic force microscopy to measure the strength of adhesion between the spider’s feet and a surface. “We found out that when all 600,000 tips are in contact with an underlying surface the spider can produce an adhesive force of 170 times its own weight,” explains study co-author Andrew Martin, also at the Institute of Technical Zoology and Bionics. “That’s like Spiderman clinging to the flat surface of a window on a building by his fingertips and toes only, whilst rescuing 170 adults who are hanging on to his back.”



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