Michigan Technological University researchers are using a protein produced by mussels to create synthetic glue that can bond securely underwater. They are now devising mechanisms that will allow the glue to be turned on and off at will.

Mussels secrete a combination of natural liquid superglues and stretchy fibers, called byssal threads, that adhere equally well in saltwater and freshwater, can stick to both hard and soft surfaces and are strong enough to withstand the roughest sea conditions. The secret behind their adhesive strength is an amino acid called dihydroxyphenylalanine (DOPA), which enables their secretions to be both cohesive and adhesive—meaning they can adhere to themselves and other surfaces.

Mussels can adhere to surfaces with enough strength to withstand the roughest sea conditions. Image credit: Randy Westbrooks, Invasive Plant Control Inc., Bugwood.org, under a Creative Commons Attribution 3.0 License.To create a synthetic glue that could hold together when wet, researchers led by Dr. Bruce Lee, assistant professor of biomedical engineering, blended DOPA with polymers, including polyester and rubber. Laboratory tests demonstrated their material could attach to a variety of surfaces—metal, plastic and even flesh and bone.

Lee and his team are now attempting to devise a method using electrical currents to create a chemical “on-off” switch that temporarily changes DOPA molecules to make the synthetic adhesive sticky or non-sticky on command. So far, they have been able to accomplish this only by tweaking the glue’s pH balance.

The researchers envision multiple uses for such a "smart glue." It could bind underwater sensors and devices to the hulls of ships and submarines or help unmanned vehicles dock along rocky coastlines or in remote locations. There also are potential medical applications, such as bandages that stay attached when someone sweats or gets wet and that make it less painful to remove a dressing.