A microscopic image of the mushroom-shaped silicone surface used in the experiment. Photo: Lars Heepe

For most of history, the only way to keep ship and boat hulls from fouling with barnacles was to put some sort of material toxic to marine growth on vessel hulls. Copper sheathing was one of the first effective, albeit costly, forms of antifouling. Copper and other sheathing worked well on wooden ships but caused galvanic corrosion of iron and steel vessels. The development of antifouling paint in the 20th century was a big step forward, although environmental concerns have been raised in recent decades over the toxicity of the coatings.

Scientists have recently been experimenting with textured coatings which make it difficult for barnacle larvae to attach themselves to the hull surface. The New York Times reports:  

Researchers who study the physics of sticky biological structures at Kiel University in Germany reported last week in the Journal of the Royal Society Interface that one option may involve texture, rather than chemicals. Covering surfaces with microscopic structures shaped like mushrooms, they find, keeps barnacles from getting a firm foothold.

Part of what makes barnacles so difficult to dislodge is that they secrete a liquid glue that makes close contact with the hull’s surface and then hardens into a cement-like substance. If they could develop structures that kept the glue from attaching smoothly, it could compromise the animals’ grip.

So far tests with a mushroom textured coating have been encouraging: The team also put a sample of the mushroom coating on a sailboat belonging to the Kieler Yacht Club that subsequently sailed through the Baltic and the North Sea for seven months, covering about 1,800 miles. When it returned, the patch was clear of barnacles.

Considerable research is still required to optimize the textures to be applied.