Researchers at Brigham Young University have created a super hydrophobic surface that makes a water droplet "bounce like a ball" before it rolls off a ramp.
Super-hydrophobic surfaces are in high demand because of their real-life applicability. Manufacturers are constantly looking for materials that provide superior water-proof qualities. Catering to this growing demand, researchers from Brigham Young University have created a super hydrophobic surface that makes a water droplet "bounce like a ball" before it rolls off a ramp.
After spending decades studying super-hydrophobic surfaces, Julie Crockett and her collegue Dan Maynes found that surfaces with a pattern of microscopic ridges or posts, combined with a hydrophobic coating, produces an even higher level of water resistance - depending on how the water hits the surface.
"Our research is geared toward helping to create the ideal super-hydrophobic surface," Crockett said in a press statement. "By characterizing the specific properties of these different surfaces, we can better pinpoint which types of surfaces are most advantageous for each application.
Rather than applications for super-hydrophobic surfaces, the team of researchers aims at providing a solution for cleaner and more efficient energy generation. Currently, power plants generate energy by burning coal to turn water into steam, which rotates a turbine. This steam is then condensed to its liquid form so that it can be used again. Researchers said that if optimal super-hydrophobic material is used to build these condensers, the process can take place faster, saving time as well as lowering the cost of energy generation.
"If you have these surfaces, the fluid isn't attracted to the condenser wall, and as soon as the steam starts condensing to a liquid, it just rolls right off," Crockett said. "And so you can very, very quickly and efficiently condense a lot of gas."
Currently, researchers are testing super-hydrophobic surfaces that have with micro posts or ribs and cavities that are one tenth the size of a human hair. These micro-structured surfaces are created through a process that is similar to the one used during photo film development. Patterns are etched on CD-sized wafers. A thin water-resistant film is added to the surface of these wafers. Researchers then use ultra-high-speed cameras to document the way water interacts when dropped, jetted or boiled on them.
Researchers have noticed that even small alternations made to surface ribs and cavities can alter how water responds to the surface.
"People know about these surfaces, but why they cause droplets or jets to behave the way they do is not particularly well known," Crockett said. "If you don't know why the phenomena are occurring, it may or may not actually be beneficial to you."
Hydrophobia is measured as a function of relative locations of the "hydraulic jump" that occurs when you direct a jet of water at a surface. To see a hydraulic jump in action, head to your sink and turn on the water. Where the stream hits the stainless steel of the sink, you'll see a circle of flatness where water is shooting outwards from the impact site. The jump is where that radiating water loses energy and bunches up in a relatively thick band of water.
As hydrophobicity increases, you'll see the radius of the pre-jump circle increases, such that the water can travel laterally across the surface for longer without losing energy. If you were to take a variety of surfaces and put them under that faucet stream-the back of a duck, a piece of cardboard, a dirty dish-you could, in a very crude sense, do your own hydrophobicity measurements.
Findings of the current study were published in the academic journal Physics of Fluids.
