Robert Cohen, Michael Rubner, and colleagues in MIT's material science and engineering department have an interesting material that will alternately attract and repel water. This has some nifty practical applications.
Link (via Neatorama)
Robert Cohen, Michael Rubner, and colleagues started by assembling a nano-structured film made of alternating layers of positively and negatively charged polymers and silica nanoparticles. The film's structure and a coating of waxy fluorinated silane cause water to bead on it, forming near-perfect spheres that easily roll off. To add the superhydrophilic regions (to which water droplets cling), the researchers applied a naturally hydrophilic polymer to selected areas.
In dry regions of the world, without easy access to clean water, such a material could be used for collecting water. In this application, the hydrophilic areas of the material would attract moisture in the air, collecting water drops that accumulate, until they spill over into the hydrophobic regions and roll into a collecting channel. Currently, in countries with limited access to clean water, the inhabitants typically use large polypropylene fiber meshes to harvest water from fog. …
Rubner's lab is also taking the technique further. "When we harvest water, we have chemistry built into the hydrophilic area so that it has an antibacterial agent to kill off bacteria and other things that cause harm," Rubner says. This decontaminates the water as it accumulates so that the collected water is safe for use. Applying this technique, the researchers have been able to kill common harmful bacteria in four minutes, he says.