FINDINGS; Like Water Off a Beetle's Back
By KENNETH CHANG
Published: June 27, 2006
In making a new type of material that can trap and channel tiny amounts of liquid, researchers at the Massachusetts Institute of Technology found inspiration in a beetle.
Scientists call slick, water-repelling surfaces -- like raincoats and just-waxed car hoods -- hydrophobic: afraid of water. Some materials repel water so well that they are known as superhydrophobic; droplets bead up into spheres that barely touch the surface. Similarly, something that almost instantly attracts and disperses water is superhydrophilic: Greek for ''really, really loves water.''
Michael F. Rubner, a materials scientist, and Robert E. Cohen, a chemical engineer, wanted to make a material with abutting patterns of superhydrophobia and superhydrophilicity.
In 2001, they read in the journal Nature that the dime-size Stenocara beetle in the Namib Desert of Africa did just that. Oxford University scientists described how tiny superhydrophilic bumps on the back of the beetle gathered moisture out of the wisps of morning fog. The water droplets then slipped off the bumps into superhydrophobic channels and rolled into the beetle's mouth. ''It provided a template of success for us,'' Dr. Cohen said.
Last month, in the journal Nano Letters, Dr. Cohen and Dr. Rubner reported success in mimicking the beetle, finding a way to print superhydrophilic patterns on a superhydrophobic surface.
While Dr. Cohen and Dr. Rubner tackled the problem as a pure research challenge -- ''It hadn't been done,'' Dr. Cohen said -- the material could have practical uses. In arid regions, people may be able to harvest water from fog. KENNETH CHANG
Photos: A beetle's feat, replicated by scientists at M.I.T. (Photos by Andrew Parker/Oxford University, top; Massachusetts Institute of Technology)