bacteria

Wrinkly coating can shimmy off bacteria

DUKE (US) — Applied to the hull of a ship like paint, a new material could shake off scum by moving in response to an electric current.

Bacterial buildup on ships increases drag and reduces the energy efficiency of the vessel, as well as blocking or clogging undersea sensors.

The material works by physically moving at the microscopic level, knocking the bacteria away. This avoids the use of bacteria-killing paints, which can contain heavy metals or other toxic chemicals that might accumulate in the environment and unintentionally harm fish or other marine organisms.

An artist’s conception of the anti-fouling material (gray) shows it dislodging a sheet of bacterial biofilm (green) after an electrical current has been applied.” (Credit: Duke)

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The researchers say similar types of materials could be used in other settings where bacterial biofilms present problems, such as on the surfaces of artificial joint implants or water purification membranes.

“We have developed a material that ‘wrinkles,’ or changes its surface in response to a stimulus, such as stretching or pressure or electricity,” says engineer Xuanhe Zhao, assistant professor in Duke University’s Pratt School of Engineering. “This deformation can effectively detach biofilms and other organisms that have accumulated on the surface.”

The results of the studies appear online in Advanced Materials. Zhao has already demonstrated the ability of electric current to deform, or change, the surface of polymers.

“Nature has offered many solutions to deal with this buildup of biological materials that we as engineers can try to recreate,” says 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 says. “In the same manner, these types of structures are used by mollusks and corals to keep their surfaces clean. To date, however, it has been difficult to reproduce the cilia, but controlling the surface of a material could achieve the same result.”

The researchers tested their approach in the laboratory with simulated seawater and barnacles and with the help of Daniel Rittschof at the Duke University Marine Lab in Beaufort, North Carolina.

Keeping bacteria from attaching to ship hulls or other submerged objects can prevent a larger cascade of events that can reduce performance or efficiency, Rittschof explains.

Once biofilms have taken up residence on a surface, they often attract larger organisms, such as seaweed and larva of other marine organisms, including worms, bivalves, barnacles, and mussels.

“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 says.

The US Office of Naval Research and the MRSEC funded the study. López also serves as director of Research Triangle Materials Research Science and Engineering Center (MRSEC), which is funded by the National Science Foundation.

Source: Duke University

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