Large container ships are some of the heaviest polluters on the planet. They burn 1,600 gallons of pollutant-laden heavy fuel oil an hour and each ship can emit over 150,000 tons of CO2 every year along with sulfur and other particulates that cause a whole host of health problems. The EPA estimates that as many as 60,000 coastal deaths each year can be attributed to the pollution. Because of this, many ship operators are increasingly looking for ways to cut down on emissions, as well as save themselves a boatload of money — quite literally.
In this vein, research being conducted by scientists at the Universities of Bonn, Rostock and Karlsruhe in Germany has unlocked the mysteries of how some types of ferns are so good at shedding water, and, in turn, how those properties can be used to make a synthetic coating for boat hulls that allows them to glide more efficiently through the water — potentially reducing heavy oil consumption by as much as 10%.
The secret lies in the tiny hairs found on the surface of the water fern, salvinia molesta. The hairs give the plant the extraordinary property of ‘superhydrophobia,’ so that even when the leaves are completely submerged for weeks on end they never get wet. The hairs create an ultra thin skirt of air around the leaves and never let the water touch the leaf surface. When the leaves are pulled out of the water, all of it runs off immediately.
If this kind of property could be applied to ship hulls, the amount of friction a boat has to overcome when cutting through water would decrease drastically. More than 50% of the propulsion energy a boat generates is used to overcome this friction, so you can imagine how even small changes in it could lead to huge results.
As it turns out, the hairs accomplish this feat with a one-two punch. It has been known for years that the hairs themselves are superhydrophobic — meaning they repel water extremely well. But when scientists tried to replicate just the hairs’ superhydrophobic properties in the lab with synthetic materials, the skirt of air proved to be very unstable and only lasted for, at most, several hours.
The researchers responsible for the current findings discovered that, in addition to the hairs themselves being superhydrophobic, the tips of the hairs have a material that is actually hydrophilic — meaning they attract water very well. The combination of the hydrophobic and hydrophilic properties in the same hair is what leads to their stability over long times. “They plunge into the surrounding liquid and basically staple the water to the plant at regular intervals,” explained Professor Wilhelm Barthlott from the University of Bonn in a statement. “The air layer situated beneath [the hair] can therefore not escape so easily.”
Not only does the discovery of how this Fern sheds water have application to boat hulls, imagine if olympic swimmers had suits made of the material… we would surely enter a whole new era of record breaking. The researchers are currently working on developing a commercial version of the material, but for now they are calling it one of the most important discoveries ever in the field of bionics. “Probably one per cent of the fuel consumption worldwide could be saved this way,” said Professor Barthlott. His colleague, Professor Dr. Alfred Leder from the University of Rostock, added, “Surfaces modelled on the water fern could revolutionise shipbuilding.”
Image Credits: From the journal article