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Barnacle busters: Tackling a shipping industry headache

December 28, 2006 By Paroma Basu

Scientists at the University of Wisconsin–Madison have devised a potentially ingenious solution to the multi-million dollar problem known as “biofouling,” a chronic headache that has plagued the shipping world for centuries.

In biofouling, marine organisms such as mollusks and barnacles firmly latch on to submerged boat hulls like secret underwater stowaways. Writing this month in the journal “Biofouling,” UW–Madison researchers report promising results from early tests of their idea-to stave off aquatic hitchhikers by shooting tiny electric jolts through the undersides of boats. In preliminary experiments, the scientists write, such electric zaps curbed the accumulation of marine life by up to 50 percent.

“It’s unlikely we would be able to prevent biofouling entirely due to the enormous diversity of fauna in the seas,” says lead author Rodolfo Perez, a UW–Madison doctoral candidate of civil and environmental engineering. “But even reducing the hull-cleaning cycle by just a bit would be a huge, tremendous advance.”

Biofouling has been a raging issue because aquatic organisms that cling onto boat hulls end up going wherever the boats go. That has spelled ecological trouble worldwide – including in Wisconsin – as ships unwittingly ferry invasive species into lakes, rivers and oceans where they don’t belong.

The carpet of sea life that steadily grows on standing or moving boat hulls also causes a kind of drag effect in water, which means that ships need a lot more fuel-up to 30 percent more, by some estimates-to compensate. “The problem of biofouling goes back several centuries,” says co-author Marc Anderson, a UW–Madison professor of civil and environmental engineering. “Right back to when Columbus sailed the seven seas.”

The U.S. Navy alone has poured millions into the search for effective anti-fouling measures. Until recently, naval and commercial shipping lines have largely relied on a type of anti-fouling paint that reduces biofouling when coated onto a boat’s hull. However, the paint contains a chemical known as tributyltin, which is known to be toxic to marine life. Studies have linked the chemical to unnatural sex changes in mollusks, for example, and deformations in oysters.

Scientists around the world have been exploring other anti-fouling alternatives. Some are working on a “non-stick” organic polymer, for example, that organisms would be unable to latch onto.

Meanwhile, scientists at UW–Madison have taken a radically different approach. Their vision is to coat the hulls of boats with thousands of microscopic electrodes – basic terminals that conduct electricity – that would gently zap any organisms that come near. Made of a metal known as titanium, the electrodes would be placed only a tiny distance apart – between 8 to 25 microns – where 1 micron measures a millionth of a meter.

In small-scale tests, Perez evaluated the anti-fouling power of the electrodes and confirmed the huge potential of the UW–Madison concept. But now the researchers say they must understand why their idea actually works. Other challenges also remain, such as determining how to produce a “blanket” of electrodes that would cover and adhere to a boat’s entire hull.

But if they succeed in their goal, the UW–Madison technology will not only start a revolution in biofouling prevention, but can be of use in many other fields, Anderson says. “This technology has applications beyond boat hulls as it could be used for optical sensors, food packaging, piping, and filters, to name a few possibilities.”

Other researchers contributing to the study include Daniel Noguera, UW–Madison professor of civil and environmental engineering; Dean Tompkins, UW–Madison associate scientist of environmental chemistry and technology; and Maggie Paulose and Craig Grimes of the Electrical Engineering & Materials Research Institute at Pennsylvania State University.

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