Silk, that luxurious material spun by insects and arachnids, is one of the most important natural fibers on Earth due to its high tensile strength, smooth texture, and insulating properties.
Now, scientists have discovered another silk superpower—the ability to withstand the cold temperatures of outer space.
This property, called cryogenic toughness, is rare in complex polymer materials like silk. When these materials are exposed to frigid temperatures approaching -200°C (-328°F), they typically become cracked and brittle. But some silks actually became stronger and more stretchable in the cold, according to a study published on Thursday in the journal Materials Chemistry Frontiers.
The team, which included silk biologist Fritz Vollrath of Oxford University, said the discovery could lead to new applications for silk in chilly environments such as outer space.
”No-one would have thought that ductility and toughness at cryogenic temperatures would be among [silk’s] properties,” Vollrath and his colleagues said in the study.
“We envision that our study will lead to the design and fabrication of new families of tough structural composites using natural silk or silk-inspired filaments for testing applications even at Arctic or indeed outer-space conditions,” the team concluded.
The researchers exposed silk threads from spiders and silkworms to liquid nitrogen chilled to −196°C, and found that the cryogenic toughness differed from species to species. Dragline silks spun by Nephila orb-weaving spiders and cocoon threads from the domestic silkmoth Bombyx mori increased in strength as temperature dropped down to about −60 °C, but became weaker by the time they were exposed to cryogenic temperatures of −196°C.
Threads from the wild silkworm species Antheraea pernyi, however, gradually increased in tensile strength all the way down to the lowest temperatures tested by the researchers. The team thinks this particular silk’s resistance to cracking in the cold is due to the tiny fibre structures, called nano-fibrils, inside its threads.
In an email, Vollrath said that the “size, great incipient strength, and changing stiffness with temperature” of the A. pernyi nano-fibrils all play into its unique properties, adding that the team hopes to “explore in much more detail how the system works” in future research.
The discovery could lead to the development of silk materials for use at the poles, outer space, or other planets. But perhaps the most dazzling possibility, suggested in a press release, is the idea of “giant webs spun by robot spiders to catch astro-junk in space.”
It remains to be seen if this very Ziggy Stardust vision will come to pass, but web-weaving robot space spiders is definitely great science fiction fodder in the meantime.