Researchers are developing a potentially eco-friendly method to control the ability of shellfish to attach to the hulls of ships, which increases drag and can hike fuel consumption by as much as 50%.

Shellfish are impressive in their ability to affix themselves to nearly any surface, including Teflon. As a result, ships are often painted with a copper-based "antifouling" paint to thwart attachment by animals such as oysters, mussels and barnacles. But the copper leaches from the paint into the water, killing animals in their larval stages.

A mussel attached to a sheet of Teflon. Image credit: Purdue University/Jonathan Wilker.A mussel attached to a sheet of Teflon. Image credit: Purdue University/Jonathan Wilker. "Current antifouling coatings function by releasing biocidal copper, essentially killing everything in the waters around a ship," says Jonathan Wilker, professor of chemistry and materials engineering at Purdue University, who is leading the research. "All major ports in the world are polluted with high copper levels. There is great demand for environmentally benign approaches to defeating biological adhesion."

Studying how these sea animals produce such strong adhesion, Wilker's research team concluded that they use oxidative chemistry—or the removal of an electron from protein molecules.

"If you remove an electron, the protein becomes more reactive and wants to connect with other proteins that have more electrons. This oxidative coupling is what cures the adhesive," Wilker says.

To overcome this tendency, the team's method hinges on interfering with the oxidation chemistry of bio-adhesion by creating surfaces with antioxidants. Finding coatings capable of drying properly without consuming the antioxidant and also remaining attached to the underlying panels while underwater proved to be challenging. The team tried numerous systems, eventually discovering combinations of antioxidants and a coating that worked well.

Their results showed that, in coatings with a 25% concentration of antioxidants, the bio-adhesion was reduced by more than one-quarter.

"The adhesion went down significantly, but not all the way to zero," Wilker says. "The main goal here was to test the idea that, with oxidative chemistry being key to formation of biological glues, reducing surfaces could decrease the bond strengths. After demonstrating this concept, we can now move on to refining the approach for making coatings that will prove to be useful on ships."

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