Sea Mussels Hold Secret to Better Glue

New research is revealing how sea mussels attach themselves to marine surfaces, giving scientists better ways to fix the human body and other things.

The detailed findings of the study were published online July 23 in the journal Nature Communications.

Unlike barnacles, which fasten themselves tightly to surfaces such as rocks, piers or the hulls of ships, mussels use silky fibers called byssus threads to loosely attach to surfaces while maintaining the ability to move with the tides and absorb nutrients in the water.

Scientists at the Massachusetts Institute of Technology , otherwise known as MIT, used laboratory tests and computer models to discover that an estimated 80 percent of every byssus thread - the material that connects the ends of the roughly oval-shaped mussels to hard surfaces - is composed of stiff material, whereas the remaining material connected to the mussel itself is soft and stretchy.

The new evidence suggests the combination between the more and less rigid properties actually helps the mussels adhere to their surfaces of choice.

"It turns out that the ... 20 percent of softer, more extensible material is critical for mussel adhesion," Zhao Qin, a research scientist at MIT, said in a statement.

And as researchers unravel the secret of the thin, bungee-like cords, they are learning how to create more effective glues and other synthetic biomedical materials.

Researchers have studied byssus threads before, but Qin and his team sought to observe how such threads and connecting parts work in simulated wave conditions.

"We figured there must be something else going on," Markus Buehler, head of MIT's department of civil and environmental engineering, said in a statement. "The adhesive is strong, but it's not sufficient."

So, the research team positioned an underwater cage with glass, ceramic, wood and clay surfaces in Boston Harbor for three weeks to test how mussels attached themselves to the various surfaces. Back in a laboratory setting, the scientists used a tensile machine to test the strength of the byssus threads as they were pulled and deformed.

It was shown that although byssus threads have both stiff and stretchy properties, the thread filaments are made of a protein material very similar to collagen. From that, the scientists reasoned the distribution of stiffness along the length of the threads is critical to their effectiveness.

Better understanding the physics of byssus threads will likely help scientists design synthetic materials with similarly flexible characteristics, like surgical stitches that connect tissues together, and comparable strengths, such as new building materials, sensors for underwater vehicles and other equipment resistant to extreme conditions.