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New shark skin-inspired hull coatings being developed by the Office of Naval Research (ONR) in the United States are said to be 'showing promise' in reducing the build-up of marine crustaceans – namely barnacles – on ships´ hulls, thus optimizing vessel performance and dramatically reducing fuel costs.

Marine growth adds weight and increases drag reducing a vessel´s fuel efficiency. The practical problem for ships is simply that biofilm can add up to 20 percent drag and barnacles over 60 percent. This therefore increases fuel consumption and greenhouse gas emissions.

"ONR-sponsored biofouling prevention coatings provide an environmentally safe alternative for protecting naval ship hulls, which could also benefit the commercial shipping industry," the ONR said in a statement.

"The ultimate solution is to stop the barnacle settlement process before it happens," said Steve McElvany, Ph.D., program manager for ONR´s Environment Quality program.

"We are really trying to look very far forward to get the ultimate solution that´s good for the U.S. Navy and the oceans."

The Naval Surface Warfare Center at Carderock estimates that biofouling reduces vessel speed by up to 10 percent. Vessels can require as much as a 40 percent increase in fuel consumption to counter the added drag. For the Navy, that translates into roughly one billion dollars annually in extra fuel costs and maintenance to keep its ships free of barnacles, oysters, algae and other debris.

High-performance naval warships and submarines rely on critical design factors such as top speed, acceleration and hydroacoustic stealth. Previous biofouling prevention methods used toxic coatings, or biocides, to clear barnacle colonies from the ship exteriors. Although effective in the short-term, biocides exact a heavy environmental burden.

"By studying the environment, researchers are learning from nature how it beats the "crusty fouler" naturally. And that´s where ONR´s investment in biofouling prevention technologies has made significant gains," the ONR said.

On the East Coast, the ONR is funding research at the University of Florida where Anthony Brennan, Ph.D., professor of material science and engineering, has been investigating why some marine animals, such as whales, harbor barnacles and others, such as sharks, stay relatively clean. Brennan discovered that the unique pattern of shark skin contributed to its ability to fend-off microorganisms.

With this insight, Brennan started modeling shark skin patterns in his lab. The idea led to the development of a new biomimetic technology called Sharklet, which is said to have shown extremely positive results in inhibiting marine growth. The significance of his work really hit home during a visit to Pearl Harbor.

"I saw a Navy ship going by ... flowing with green algae," Brennan said. "I thought that's why we are doing this research, to stop that biofouling … to give our Navy the ability to perform at a higher level."

The biodiversity of different ocean environments also creates unique challenges. So, across the country on the West Coast, ONR is working with Dr. Shaoyi Jiang Boeing-Roundhill, Professor at the University of Washington, on biofouling prevention coatings that incorporate zwitterionic or mixed-charge compounds.

"The marine environment is very complicated," said Jiang. "It is as complex as the human body." Zwitterionic compounds are stable, alternating perfectly between positive and negative charges, and easy to handle in both laboratory and field tests. They´ve shown excellent resistance to the attachment of biomolecules and microorganisms. The result is that naturally occurring proteins, bacteria, algae, barnacles and tubeworms do not bind to this unique surface.

"ONR´s innovation in hull coatings will optimize ship performance with an eye toward environmental stewardship. Inventive biofouling prevention systems will help conserve fuel, minimize the Navy´s carbon footprint, reduce the risk of transporting invasive aquatic species and prevent toxic biocides from entering surrounding environments," the ONR said. To view a video of the ONR's biofouling prevention programme, please visit the following address:

http://www.eurekalert.org/multimedia/pub/14453.php?from=138310