Super Sticky Coating has 'Mussel'

Oct. 18, 2007 -- Mussels have a remarkable strategy for staying put in surf zones, despite the crashing waves: they secrete a fluid that can bond to virtually any surface.

Now scientists have developed a coating that mimics the tenacious adhesion of a mussel. The coating could improve biosensors, medical devices, marine and medical anti-fouling coatings, purify water contaminated with heavy metals, and advance manufacturing methods for flexible displays.

"We demonstrated something like twenty-five different materials that this would work on," said Phillip Messersmith, professor of biomedical engineering at Northwestern University in Evanston, Ill.

He and his team report their findings in today's issue of Science.

The coating is made from dopamine, a molecule more commonly known for it neurotransmitting abilities. Although it does not exist in mussels, dopamine contains two key chemical groups that are present in the crustacean's holdfast -- the part that helps it cling to surfaces. By capitalizing on these chemical properties, Messersmith and his team were able to mimic the mussel's steadfast stickiness.

Creating the coating involves a relatively simple procedure free of the expensive, chemically sophisticated techniques often necessary to produce other coatings. The scientists dissolve the dopamine in water and then adjust the pH level to match a marine environment. When they do that, a chemical reaction occurs that produces a polymer in the solution.

Now any object can be dipped into and coated with the polymer, or conversely the solution can be sprayed or painted onto any surface. And like the mussel secretion, this polymer sticks to virtually any surface.

What makes it even more interesting is that a second layer of just about any other coating can be applied on top of the polymer and, in most cases, stick.

These secondary coatings can be anything from a thin metal layer on electronic circuitry to surfaces that promote stem cell growth to coatings that prevent bacteria from attaching to medical implants or prevent barnacles from adhering to ship hauls.