New plastic coating may shed water better than a duck's back

WASHINGTON -- Self-cleaning traffic signs and antennas and roofs that shed ice like water off a duck's back could be in the future thanks to a newly developed coating that is super at sending water on its way.

A team of Turkish materials researchers took the sacred lotus plant as their inspiration in developing the coating.

H. Yildirim Erbil, leader of the team that developed the plastic at Kocaeli University in Izmit, Turkey, said possible applications could range from water-repellent fabrics to traffic signs, cables and even ship hulls that slice easily through the ocean.

"It was marvelous," said Erbil of the sight of water drops dancing across the coating surface. Their results were reported in Friday's issue of the journal Science.

Erbil said the coating should be inexpensive if it can be made on a larger scale and can have a variety of uses. But, as it is white and not transparent, it cannot be used for windows. Other water-repelling chemicals that are clear are on the market, however.

Richey M. Davis, a professor of chemical engineering at Virginia Polytechnic Institute, said the finding "is important because it describes an elegant and simple approach to making a variety of surfaces highly nonwettable."

Mimicking nature

"In recent years, the materials science community has come up with one example after another of engineered structures that mimic the form or the chemistry of biological structures," added Davis, who was not part of the research team. "There are certainly many technologies and applications that could benefit from having a simple, inexpensive method for making a surface" resist water.

The ability of a surface to avoid becoming wet can be increased by making it rougher, the team reported, citing as an example the leaves of the lotus plant, an aquatic perennial originally from Indonesia and India. In some Asian religions, the sacred lotus is a symbol for purity.

At very small scale -- millionths of a yard -- those leaves have a roughness that forms tiny air pockets, leaving water with little plant surface to stick to. Reducing the amount of plant -- or plastic -- that comes in contact with the water lessens the water's ability to stick.

The lotus leaves have a waxy coating that the researchers studied for its self-cleaning ability to shed water and debris.

The research was driven by curiosity and not backed by any industrial company, Erbil said.

The team was "surprised and pleased" by the result, said Erbil, a chemist who studies the physical surface of materials.