New Coating Mimics Dolphin Skin

Studies of dolphins triggered some surprisingly good ideas about techniques for keeping the ship hulls clean. Karen L. Wooley, Ph.D., professor of chemistry at Washington University in St. Louis (USA), has noted the shape and texture of dolphin skin and how it naturally prevents marine creatures from clinging to it. The observation fits into her study of finding ways to mediate interactions between biological systems and synthetic materials, designing chemical "functionalities," or groups of atoms, that either promote or discourage binding between them.

Wooley is currently is developing a group of nontoxic "antifouling" coatings that may one day inhibit marine organisms such as barnacles, tube worms and zoo spores from attaching to the hulls of ships. The key to Wooley's antifouling agents is, perhaps counter-intuitively, their three-dimensional topography, which mimics such naturally occurring hydrodynamic surfaces as the skin of a dolphin. Using high-powered electron microscopy, researchers have found that dolphin skin, for all its seeming smoothness, is slightly rippled on the nanometer scale. Still, these ripples are not large enough to hinder movement through the water but are small enough that they leave few "niches" for marine creatures to grip.

"For a long time antifouling work was geared toward making super-smooth surfaces," explained Wooley. "It was thought that if the surfaces were super-smooth and had less surface energy then the organisms couldn't attach. "In fact, that's completely false," she continued. Her current antifouling project "completely goes against the grain of what was being done. I think that I generally like to do that -- just try the completely opposite approach and see what happens."

The key is the complex surface, which makes it difficult for marine organisms to establish a toehold. "When the polymer surface is first prepared, it looks like a bunch of sub-microscopic mountains but when it's placed under artificial sea water, the entire surface swells and gives us this inverted structure," Wooley explained. "I think this is really exciting because what it means is that we can 'tune' the size of the surface features and determine whether our hypothesis is really correct -- do surface feature sizes influence the attachment of marine organisms?"
If she's right, the implications could be straight out of science fiction: man-made ships protected by layers of synthetic dolphin skin. Mother Nature, it seems, may have some competition.