Water is a vital resource, but there are many times when we need to keep something completely dry—not by soaking it up with a cloth, but by repelling it entirely. We've seen some fascinating examples of superhydrophobic surfaces in the past, but researchers at the University of Rochester have just written a new chapter by creating a metal surface so efficient that it doesn't require any additional coating.
Consider someone washing a frying pan. They place it on the stove, pour a little oil into it, and wait for it to heat up. Chances are, a few drops of water remain on the surface. When those drops reach their boiling point, that's when everyone must run for their lives. It might seem logical to use a Teflon pan and pay much more attention to drying it thoroughly, but that's just a simple example of what happens when water ends up in the wrong place. From the effects of rust to the frozen wing of an aircraft, there are times when water simply plays a nasty trick on us. Previously, several coatings and treatments have been developed to help surfaces repel liquids, but what they've just accomplished at the University of Rochester is sensational.
From Superhydrophilic to Superhydrophobic
The work of Professor Chunlei Guo began with the creation of a superhydrophilic surface—in other words, one that attracts water. It was so efficient that water could climb the metal surface against gravity. From there, his goal was to go in the opposite direction and create a superhydrophobic metal. The technique is based on a previous university technology that uses laser pulses to turn any metal black. This time, the laser pulses are applied in such a way that they generate micro- and nanoscale structures.
The new surface repels water with such intensity that droplets can be seen bouncing off and being ejected, almost as if they had a genuine fear of contact. The best part is that during their escape, the water droplets carry away dust particles and other materials, leaving the surface not only dry, but also clean.
Guo's development requires no chemicals and doesn't wear out over time. Compared to Teflon, which requires a 70-degree tilt before water begins to slide off, Guo's surface needs only five degrees or less. Guo has highlighted the potential of the laser hydrophobic surface in fields such as health and hygiene. This could lead to more efficient water collection systems, and toilets with a drastic reduction in water usage.
Does that sound familiar? That's right—the Gates Foundation has provided support to Guo and his team.
