MIT scientists have dramatically reduced the time it takes for water droplets to rebound from superhydrophobic materials (water-shedding surfaces). Specially designed macroscopic ridges cause water droplets to split and recoil from the surface, reducing contact times by up to 40% compared with other hydrophobic materials. The research team believes this could help to prevent the build-up of ice on aeroplane wings and water on turbine blades.
“If you can make the blades stay dry longer, you get a bump up in efficiency”, says Kripa Varanasi, the Doherty Associate Professor of Mechanical Engineering at MIT, who co-authored a paper on the findings for Nature.
The self-cleaning, non-corrosive and non-rusting characteristics of superhydrophobic materials could also keep structures in pristine conditions for greater lengths of time, without the need for environmentally detrimental materials such as detergents or tin and copperbased anti-fouling paint.
Professor Ivan Parkin, Materials and Inorganic Chemistry Professor at UCL, believes they have the potential to be used in a wide range of applications.
“They could be used in a new generation of self-cleaning paints, in water transport by reducing friction in pipes and, in the longer term, in superhydrophobic hulls for ships, which would reduce drag and the energy required for transportation.”
Presently, the largest obstacle facing the technology is maintaining the strength of the material. The nano-sized rough surfaces needed to repel the water are easily destroyed by even small amounts of abrasion. Despite this shortcoming, the technology has already begun to appear on the consumer market, with companies such as NeverWet producing superhydrophobic sprays.
Once perfected, the technology could theoretically be applied to countless objects and processes. It might also lead to improvements in desalination and hygiene by providing cheap, clean drinking water and reducing the transmission of infectious diseases: the self-cleaning nature of hydrophobic materials means that water does not remain on them long enough to stagnate. Such superhydrophobic materials could potentially benefit millions of lives, including those of the most marginalised.
Varanasi’s team are confident that contact times can be further reduced for their superhydrophobic material by refining the surface textures. “I hope we can manage to get a 70 - 80% reduction”, he says. – John Duffy
Photo credit: Flickr pranav