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Hull Coating Shakes Off Marine Scum

Monday, February 4, 2013

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A novel coating will allow a ship to shed unwanted bacteria and marine scum with the flick of a switch, according to a group of engineers at Duke University.

Phanindhar Shivapooja and Qiming Wang / Duke University

The coated surface repels bacteria at a microscopic level, researchers say. This is an illustration of the material at work.

The material, which can be applied like paint to a ship’s hull, will help keep the surface free from buildup that increases drag, reduces the vessel’s energy efficiency, and blocks or clogs undersea sensors, the engineers said in a news release.

The research, funded by the U.S. Office of Naval Research, was recently published in the journal Advanced Materials.

How does it Work?

The material works by physically moving at the microscopic level, knocking the bacteria away.

Seviwurst / Wikimedia Commons

Like horses shake off pesky flies by twitching their skin, ships may soon be able to shed bacterial buildup in a similar fashion, Duke University researchers say.

“We have developed a material that ‘wrinkles’ or changes its surface in response to a stimulus, such as stretching or pressure or electricity,” said engineer Xuanhe Zhao, assistant professor in Duke’s Pratt School of Engineering.

“This deformation can effectively detach biofilms and other organisms that have accumulated on the surface.”

The development is an alternative to bacteria-killing paints, which can contain heavy metals or other toxic chemicals that might accumulate in the environment and harm fish or other marine organisms, the researchers said.

Materials with similar properties could also be used to keep artificial joint implants or water purification membranes free from biofilm.

Mimicking Nature

“Nature has offered many solutions to deal with this buildup of biological materials that we as engineers can try to recreate,” said Gabriel López, professor of biomedical engineering and mechanical engineering and materials science.

“For example, the hair-like structures known as cilia can move foreign particles from the lungs and respiratory tract,” Lopez said. “In the same manner, these types of structures are used by mollusks and corals to keep their surfaces clean. To date, however, it is been difficult to reproduce the cilia, but controlling the surface of a material could achieve the same result.”

Lopez notes that once bacteria have taken up residence on a surface, they often attract larger organisms, such as seaweed and larva of other marine life, which can led to further buildup.

“It is known that bacterial films can recruit other organisms, so stopping the accumulation process from the beginning in the first place would make a lot of sense,” Lopez said.