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Monday, 7 November 2016

Mussel serve as inspiration for a new type of underwater adhesive

ARLINGTON, US: Even the strongest glues breakdown when soaked, but one scientist at Michigan Technological University (MTU) has created a nature-inspired adhesive (glue) that stays sticky when wet.

With support from the Office of Naval Research (ONR), Dr Bruce Lee, an assistant professor of biomedical engineering at MTU, uses a protein produced by mussels to create a reversible synthetic glue that not only adheres securely underwater—but also may be turned on and off with electricity.

Like barnacles, mussels stick to rocks, docks and ship hulls—a natural occurrence called biofouling. Mussels secrete a combination of natural liquid superglues and stretchy fibres, called byssal threads, that works equally well in saltwater and freshwater; can stick to both hard and soft surfaces, and is strong enough to withstand the roughest sea conditions.

The mystery behind mussels' adhesive success is an amino acid called dihydroxyphenylalanine—DOPA. A chemical relative of dopamine—the neurotransmitter that controls the human cerebrum's pleasure and reward focuses—DOPA is a basic fixing in affixing the superglues and byssal threads to an area. It additionally empowers mussel emissions to be both durable and adhesive —which means they can hold fast to themselves and other surfaces.

“Biomimetic approaches [synthetic methods that replicate natural processes] have been used before to create materials for wet adhesion,” said Dr Laura Kienker, manager of ONR’s biomaterials and bionanotechnology program.

“The exclusive aspect of Dr Lee’s research is that it intends to build up a biomimetic wet glue that can quickly and repeatedly bond to, and separate from, a variety of surfaces in response to the applied electrical current. There are both non-medical and medical applications of such a material for the Navy and Marine Corps,” added Dr Kienker.

Lee and his group combined DOPA with polymers such as polyester and rubber to create the synthetic glue that holds together when wet. Laboratory tests confirmed this material can stick to a variety of surfaces, including metal, plastic and even flesh and bone.    

"One exceptionally quality of this synthetic glue is its versatility," said Lee. "We can change the chemistry to make it as inflexible or adaptable as we need—while as yet keeping up its general quality and durability."

Lee and his group are presently attempting to make sense of how to utilise electrical currents to create a chemical “on-off” switch that temporarily changes DOPA molecules to make the synthetic adhesive sticky or non-sticky at will. So far, they’ve been able to accomplish this by tweaking the glue’s pH balance, but are still working to achieve this capability using electrical stimulation.

“This work is novel in the sense that there is no smart adhesive out there that can perform underwater,” said Lee. “The chemistry that we can potentially incorporate into the adhesive, causing it to reversibly bond and debond, is quite new.”

Lee imagines 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 possible medical applications for an adhesive that can bind and unbind at will. It could prompt to new sorts of bandages that will remain connected when someone sweats or gets wet, and make it less painful to remove a dressing. The smart glue may even be used one day to attach prosthetic limbs and biometric sensors or seal surgical wounds.

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