For years, scientists seeking stronger glues have been looking to nature for inspiration, trying to figure out what keeps barnacles anchored on rocks and how geckos climb effortlessly up walls. All that attention to mimicking adhesives may be missing
For years, scientists seeking stronger glues have been looking to nature for inspiration, trying to figure out what keeps barnacles anchored on rocks and how geckos climb effortlessly up walls. All that attention to mimicking adhesives may be missing the whole picture, though, according to a study that finds that when it comes to mussels rooted to rocks or boat hulls, the strength of the glue is only part of the story.
Researchers at the Massachusetts Institute of Technology were initially interested in the adhesive patches that mussels use to anchor themselves, even in rough surf. The glue turns out to use an elegant, simple mechanism to adhere -- it is made up of proteins that form bonds like the ones found in water molecules. But by itself, the glue didn’t appear to be strong enough to account for mussels’ tenacity and ability to stick to surfaces.
“When we computed the adhesion strength of these mussels and we compared it to the forces we’d expect from these waves, we found the wave would be way stronger than the strength of the adhesion bonds, and they should break immediately — which they don’t, in nature,” said Markus Buehler, a professor of civil and environmental engineering at MIT who led the research.
So Buehler got interested in the web of “byssus threads” that connect the adhesive to the mussel, tethering the mollusk to a rock or ship’s hull like an anchor. Perhaps, they thought, those threads had special properties that had not been fully appreciated.
Research scientist Zhao Qin dropped a type of underwater cage into Boston Harbor and returned three weeks later to harvest mussels that could then be systematically studied in the laboratory to understand the strength of the bond of the byssus threads.
In a study published in the journal Nature Communications on Tuesday, the researchers found that the byssus threads’ unusual composition — made up of 80 percent stiff materials and 20 percent soft and stretchy materials — accounted for their remarkable ability to cling to surfaces. The majority of the length of the thread is stiff, researchers found, with the flexible part of the thread attaching to the mussel.
Buehler thinks that engineers can take inspiration from mussels. Usually, he said, engineers approach problems by taking dispara