The results came as a great surprise.
"Most people that publish in this field always go for these perfect structures, and we are the first to show that the bad ones are the better ones," Sigmund said. "Of course this is a finding in a lab. This is not something you expect from theory."
To be sure, water-repelling surfaces or treatments are already common, spanning shoe wax to caulk to car windshield treatments. Scientists have also reproduced other biologically inspired water repelling surfaces, including ones patterned after lotus leaves.
But Sigmund said the UF surface may be the most or among the most water phobic. Close-up photographs of water droplets on dime-sized plastic squares show that the droplets maintain their spherical shape, whether standing still or moving. Droplets bulge down on most other surfaces, dragging a kind of tail as they move. Sigmund said his surface is the first to shuttle droplets with no tail.
Also, unlike many water-repelling surfaces, the UF one relies entirely on the microscopic shape and patterns of the material rather than its composition.
In other words, physics, not chemistry, is what makes it water repellent. Theoretically, that means the technique could transform even the most water-sopping materials say, sponges into water-shedding ones. It also means that Sigmund's surfaces need never slough off dangerous chemicals. Provided the surface material itself is made safe, making it water repellent introduces no new risks.
Although he hasn't published the research yet, Sigmund said a variation of the surface also repels oil, a first for the industry.
Sigmund said making the water or oil-repelling surfaces involves applying a hole-filled membrane to a polymer, heating the two, and then peeling off the membrane. Made gooey by the heat, the polymer comes out of the holes in the desire
|Contact: Wolfgang Sigmund|
University of Florida