From: Allison Winter, ENN
Published July 25, 2013 01:03 PM

Mussel Strength: Byssus Threads May Hold the Key to Better Glues and Biomedical Interfaces

With a name like 'mussel' one would expect that these bivalves must have one strong muscle to help them attach to rocks in order to prevent the risk of being torn by crashing waves and currents. But what helps these mussels stay attached to their home base is actually a collection of fine filaments known as byssus threads.

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And the secret to the strength of these byssus threads has now been unraveled by MIT research scientist Zhao Qin and professor of civil and environmental engineering Markus Buehler.

Researchers found that the byssus threads are composed of a well-designed combination of soft, stretchy material on one end and much stiffer material on the other. Both materials, despite their different mechanical properties, are made of a protein closely related to collagen, a main constituent of skin, bone, cartilage and tendons.

"Many researchers have studied mussel glue before," Qin says, referring to the sticky substance that anchors byssus threads to a surface. But the static strength of the glue, and of the thread itself, "is not sufficient to withstand the impact by waves," he says. It's only by measuring the system's performance in simulated wave conditions that he and Buehler could determine how it accomplishes its amazing tenacity.

The distribution of stiffness along the threads is key, Qin and Buehler found, suggesting that the distribution of intrinsic material properties and the overall architecture of the mussel attachment are important.

The distribution of stiffness in the mussels' threads enables them to be subjected to very large impact forces from waves. About 80 percent of the length of the byssus threads is made of stiff material, while 20 percent is softer and stretchier. This precise ratio may be critical, the researchers found: The soft and stretchy portions of the threads attach to the mussel itself, while the stiffer portion attaches to the rock. "It turns out that the ... 20 percent of softer, more extensible material is critical for mussel adhesion," Qin says.

These findings could help in the design of synthetic materials like surgical sutures used in blood vessels or intestines that are subjected to pulsating or irregular flows of liquid. Scientists may also use this discovery in helping attach tendon to bone. In addition, the researchers say there may also be applications for materials to attach instruments to buildings, or sensors to underwater vehicles or sensing equipment in extreme conditions.

Their findings appear this week in the journal Nature Communications.

Read more at MIT News.

Mussel image via Shutterstock.

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