Super-strong mussel fibers could inspire earthquake-proof buildings

M. edulis
A blue mussel specimen, Mytilus edulis, is attached to a rock on the shoreline near Boston.

When they're not starring in some warm Boston chowder, blue mussels can be found clinging onto rocks and sea decks all along the coast of New England. They're anchored in place by a stringy outcrop of cabling that emerges from between their twin shells. Usually, even the most vicious of high tides can't pry them loose.

The secret to their tenacity is the special design of the rope-like strands that bind them, researchers now find. They're got a bit of stiffness and a bit of flexibility, they report in the July 23 issue of Nature Communications, and that's what keeps the mussels sticking around.

"If you're an engineer, you're trying to fix things very rigidly," Markus Buehler, professor of civil and environmental engineering at MIT, told NBC News. "But nature has taught us here that to make things resilient in the long term, there needs [to be] a flexible structure."

M. edulis attached to the surface of a piece of clay, after being caged in the Boston harbor for three weeks
Zhao Qin and Markus Buehler grew mussels on slabs of clay in the Boston harbor. Then, using a machine with a clamp, they slowly pried the animal away from the clay, to watch how the threads reacted to the force.

Twenty percent of the cabling that holds the bivalves in place is strong, but flexible. The rest is stiff. When it's tugged away by the force of a crashing wave, the flexible bits help the structure give, just a little bit, dissipating some of the stress on them. Construction materials made of a similar blend of firm and flexible parts could help buildings withstand high-stress forces during an earthquake, Buehler said.

Materials with a stiff and soft gradient are hard to manufacture, but 3-D printing could aid engineers with such specific needs. The mussel fibers are helped along by a biological glue that stays sticky when wet or dry, and unlike engineering glues, aren't made of toxic chemicals.

Buehler's made a career of studying extra-strong materials. He's previously explained how spider webs, though gossamer-thin, are built to last, and what it is about the microstructure of bones that makes them sturdy.

Markus Buehler and Zhao Qin are authors of "Impact tolerance in mussel thread networks by heterogeneous material distribution" published in Nature Communications on July 23.

Nidhi Subbaraman writes about science and technology. Follow her on Facebook, Twitter and Google+.