Skin made of air against friction

Special bionic surfaces should hold air layer

Bristles of the water spider in close-up Uni Bonn
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In the future ships might be able to glide through the water much more smoothly and thus save energy than before, and even swimmers could benefit from special surface structures modeled on nature. The trick: A layer of air to make this vision possible - so at least the idea of ‚Äč‚Äčscientists at the University of Bonn.

When she dives, the water hunt spider slips into a silvery shiny dress: her body then covers herself with a skin of air that prevents the spider from getting wet. Countless small bristles trap the layer of air so that the stream of water can not carry it away. For the predator, the layer serves as an oxygen cylinder in its hunt for fish: it always carries its air supply even under water.

"We are interested in one reason for this phenomenon, " explains Zdenek Cerman from the Bonn Nees Institute for Biodiversity of Plants. "Thin layers of air can drastically reduce surface friction and are therefore of interest, for example, for shipbuilding or for the construction of low-friction pipelines." The problem: So far no materials can be produced that can hold air in flowing water for a longer period of time. "Some plants and animals can but apparently; we wanted to find out why. "

The bionics around professor dr. Wilhelm Barthlott have about 25

Plant and animal species under closer scrutiny. They came upon interesting structures: So found on the body of the water spider numerous short bristles, which lay through the pressure of water like the brackets of a trap iron on the air layer and prevent it from being washed away. display

The aim now is to artificially produce similar surfaces.

Already today, for example, there are ships in which a compressor flows around its hull with numerous fine nozzles during the journey. Thanks to this "microbubble technology", energy consumption is reduced by around 10 percent - a head start that is largely eroded by the power-consuming compressor. "Our approach is different, " explains Cerman; "Our surfaces should hold the air passively, so you would not have to renew the layer permanently."

In addition, "air-coated" materials do not get wet - an advantage that also makes them interesting for the production of textiles, for example for the production of quick-drying bathing suits. Cerman and his colleagues, in cooperation with the Institute for Textile and Process Engineering in Denkendorf, have already been able to produce a fabric that is completely dry even after four days when it is pulled out of the water - ten times longer than today's high-tech textiles. For further developments, however, Cerman still literally breathes: "This is a very first prototype, which was created in a pilot study; There's a lot to be done to that. "

(University of Bonn, March 10, 2005 - NPO)