06-May-2010 - Rheinische Friedrich-Wilhelms-Universität Bonn

Bionic coating could help ships to economize on fuel

Materials based on water ferns could reduce fuel consumption massively

The hairs on the surface of water ferns could allow ships to have a 10 per cent decrease in fuel consumption. The plant has the rare ability to put on a gauzy skirt of air under water. Researchers at the University of Bonn, Rostock and Karlsruhe now show in the journal Advanced Materials (doi: 10.1002/adma.200904411) how the fern does this. Their results can possibly be used for the construction of new kinds of hulls with reduced friction.

The water fern salvinia molesta is exremely hydrophobic. If it is submerged and subsequently pulled out the liquid immediately drips off it. After that it is completely dry again. Or to be more precise: it was never really wet. For the fern surrounds itself by a flimsy skirt of air. This layer prevents the plant from coming into contact with liquid. And that even with a dive lasting weeks.

Materials researchers call this behaviour 'superhydrophobic'. This property is of interest for many applications such as rapidly drying swimsuits or simply for fuel-efficient ships. Meanwhile, it is possible to construct superhydrophobic surfaces modelled on nature. However, these 'replicas' have a disadvantage: the layer that forms on them is too unstable. In moving water it disappears after several hours at the latest.

The researchers from Bonn, Rostock und Karlsruhe have now deciphered the trick the water fern uses to pin down its airy skirt. It has been known for some years now that on the surface of its leaves there are tiny whisk-like hairs. These are hydrophobic. They keep water in the surroundings at a distance.

Water is 'stapled in place'

But this is only one side of the coin: 'We were able to show that the outermost tips of these whisks are hydrophilic, i.e. they love water,' Professor Wilhelm Barthlott from the University of Bonn explains. 'They plunge into the surrounding liquid and basically staple the water to the plant at regular intervals. The air layer situated beneath it can therefore not escape so easily.'

Professor Barthlott is head of the Nees Institute of Biodiversity of Plants in Bonn. There the experiments began which are continued today in conjunction with the Chair of Fluid Dynamics at the University of Rostock and the Institute of Applied Physics at the University of Karlsruhe. 'After the solving of the self-cleansing of the lotus leaf twenty years ago, the discovery of the salvinia effect is one of the most important new discoveries in bionics,' Professor Thomas Schimmel from the University of Karlsruhe says.

Fuel saved world wide: one per cent

And it is one with huge technical potential to boot. Up to now with container ships more than half of the propulsion energy is lost through friction of the water at the hull. With an air layer this loss could be reduced by ten per cent according to the researchers' estimate. Since ships are huge fuel guzzlers, the total effect would be enormous. 'Probably one per cent of the fuel consumption worldwide could be saved this way, is Professor Barthlott's prognosis. 'Surfaces modelled on the water fern could revolutionise shipbuilding,' Professor Dr. Alfred Leder from the University of Rostock concurs.

Lotus and the water fern salvinia are only two of maybe twenty million species populating our planet. They all have their secrets, and Bonn, Rostock and Karlsruhe are working on unlocking these.

Facts, background information, dossiers
  • bionics
More about Universität Bonn
  • News

    "Heavy" hydrogen stabilizes drugs

    Researchers at the University of Bonn have presented a method that allows the heavier hydrogen "brother" deuterium to be introduced specifically into many different molecules. The deuterated compounds obtained in this way are more stable against degradation by certain enzymes. Drugs produce ... more

    Chemists design "molecular sea of flags"

    Researchers at the University of Bonn have developed a molecular structure that can cover graphite surfaces with a sea of tiny flagged "flagpoles". The properties of this coating are highly variable. It may provide a basis for the development of new catalysts. The compounds could also be su ... more

    Kekulé's shattered dream: snakes become ladders

    Researchers from the Universities of Bonn and Regensburg move packets of energy along a molecular ladder made of hundreds of benzene rings. Such polymers can potentially be used to design new displays based on organic light-emitting diodes, or for solar cells. The extraordinary material is ... more

More about Uni Rostock
  • News

    Laser takes pictures of electrons in crystals

    Microscopes of visible light allow us to see tiny objects such living cells and their interior. Yet, they cannot discern how electrons are distributed among atoms in solids. Now researchers around Prof. Eleftherios Goulielmakis of the Extreme Photonics Labs at the University of Rostock and ... more

    Taking the temperature of the periodic system

    It took almost a century until the spectral lines, first discovered by William H. Wollaston and Joseph von Fraunhofer at the onset of the 19th century, were explained by Niels Bohr with his famous atomic model. Quantum mechanics then provided the tools to calculate the atomic spectral lines ... more

    Added Disorder Drives Transition to Photonic Topological Insulator

    As the journal Nature reported recently, a research group led by the Rostock physicist Professor Alexander Szameit, in collaboration with colleagues in Israel and the U.S., experimentally demonstrated that a messy topological insulator can be restored in its properties by inducing random di ... more

More about Uni Karlsruhe