The next time you bungee jump off a cliff, new materials developed in the United States and Canada may be able to provide you with a smoother ride.
Based on mermaid's necklace, a gooey, stringy material snails use to protect their growing embryos, the synthetic substance could have a range of applications, from bounce-less bungee cords to replacement, artificial ligaments for knees and other joints.
"These delicate little critters are tossed around for months and months by very large breakers and manage to survive," said Herbert Waite, a professor at the University of California, Santa Barbara, and co-author of a new paper in the journal Nature Materials who is studying the mermaid's necklace.
"You could put something that delicate in a leather or plastic pouch, subject it to that same environment, and it would be very damaged."
Similar to DNA
Washed up on the beach, mermaid's necklace resembles a translucent, gooey string of pearls several feet long.
At the molecular level, mermaid's necklace resembles a twisted ladder, similar to DNA, but with three stringers instead of two.
As the twisted triple helix emerges from the whelk, a snail found on the East Coast of the United States, the creature layers the strands on top of each other, forming a small, tube-shaped casing. The 50 to 100 strands give the necklace the strength of plastic and the flexibility of rubber.
Pulled in opposite directions, mermaid's necklace stretches like a rubber band, the bonds between the coiled triple helices breaking one by one as the material elongates.
Unlike a rubber band, however, once the maximum length is reached, mermaid's necklace doesn't quickly bounce back. The triple helices slowly re-form the broken bonds, shortening the strand back to its original resting length.
Easing the landing
If a person jumped off a bridge using a cord made of mermaid's necklace, the bungee jumper would come to a gentle halt before being slowly raised back up.
Mermaid's necklace is far from the only biological material inspiring scientists to create a synthetic analog. Other biomemetic materials based on abalone shells or drag line spider silk have received extensive attention over the years.
Yet despite many attempts to create a synthetic analog of these super strong, super tough natural materials, none has fully replicated the genuine article.
Mermaid's necklace could be one of the first materials to have an effective synthetic counterpart, says Bob Shadwich, a scientist who studies biomemetic materials at the University of British Columbia.
Spider silk protein, for example, can be made from transgenic goats, but human scientists still can't weave those proteins together the way spiders can.
Mermaid's necklace proteins, on the other hand, "show a very strong propensity to self-assemble, which makes producing the material much easier," said Shadwick.
In fact, one of Shadwick's students has already electospun a synthetic version of mermaid's necklace. Electrospinning was developed decades ago to produce synthetic materials like nylon. The student "just hasn't gotten to the point of testing its material properties yet," said Shadwick.
Wide range of uses
If a synthetic version of mermaid's necklace is developed, there would be a wide range of potential applications for this material: parachute cord that provides a gentle stop instead of an abrupt jerk, rope that automatically raises a fallen climber back to his starting position, and self-healing, artificial tendons and ligaments, just to name a few.
"It's not far-fetched at all," said Shadwick. "It's just a matter of getting it done."
While many scientists are working on synthetic analogs of mermaid's necklace and spider silk for the benefit of humans, Waite says that he is focused on studying animals like the channeled whelk to help preserve them.
In the coming years, "40 percent of all marine species will become extinct due because of man-made reasons," said Waite.
"A lot of people are focused on these animals only because they are a treasure trove of applications, but those applications won't be around if these species vanish," he added.