Even the strongest artificial glues are completely useless when you try to apply them underwater, but somehow shellfish are able to hold fast to rocks to deter predators from trying to carry them away. Clearly, nature has already figured out how to make glues that work underwater, and now researchers may have discovered the secret.
In a paper recently published in the journal Applied Materials and Interfaces, researchers at Purdue University detail a new "biomimetic" glue, inspired by the observation that shellfish like mussels stick incredibly well to rocks, despite the crashing ocean constantly trying to undo their efforts.
It turns out that mussels are able to stick to surfaces, even while under water, using tiny hairs covered in a natural glue containing proteins rich in the amino acid DOPA. While most adhesives interact with water, compounds in DOPA, called catechols, don't. Instead, they work right through it to bind to the surface of other materials. When the researchers added these amino acids, along with other mussel proteins, to an artificial polymer they'd made, it became one of the strongest underwater glues ever created.
Surprisingly, bond tests showed the new adhesive, known chemically as poly(catechol-styrene), to be about 17 times stronger than the natural glues used by the mussels. However, the researchers didn't pat themselves on the back for totally one-upping Mother Nature. They believe that mussels naturally limit the strength of their adhesives so that it's easier for them to break free when it's time to relocate.
Once perfected, mussel-inspired glue could lead to new ways to manufacture vehicles, or structures, that are subjected to water all the time. It could also make performing underwater repairs, either temporary or permanent, considerably easier, given how complicated processes like welding underwater can be. And just maybe, it will lead to easy repair kits that don't require you to drain an entire swimming pool just to deal with a small crack.