The Atacama Desert on the coast of Chile is home to one of the driest regions on Earth. Researchers at MIT's School of Engineering, along with colleagues at the Pontifical University of Chile in Santiago, are attacking the problem with some pretty unconventional means. By deploying a system of mesh structures, erected on high ground consistently cloaked in fog, they have been able to collect fog and convert it into potable drinking water that can also be used for agriculture.
The fog-collecting system is a wonderful application of biomimicry. As noted in the group's 2013 findings, researchers including MIT mechanical engineering professor Gareth McKinley looked to organisms native to arid regions, like the Namib beetle (S. gracilipes), that are able to collect fog for hydration.
The Namib beetle, found in the Namib desert of South Africa, uses its shell to collect morning fog. Its hardened wings feature both hydrophilic (water-attracting) bumps and hydrophobic (repelled by water) troughs, which researchers mimicked with their mesh system's coatings.
Researchers also cited as inspiration Stipagrostis sabulicola grass, found in the same region, which "employs an anisotropic microstructure on its thin long leaves to direct water droplets towards its roots," and Pinus radiata and Casuarina equisetfolia tree canopies with slender leaves that "also harvest water from fog."
In an effort to find the most efficient fog-collection system, researchers have experimented with variations in mesh spacing, as well as with its size and the mesh fibers' "wettability." Woven polyolefin, a common and inexpensive plastic, collects about 2 percent of fog, while finer mesh can collect as much as 10 percent.
In their 2013 findings, researchers reported that laboratory experiments suggest the best wettability performances can be found in a mesh made of stainless-steel filaments roughly three or four times the thickness of human hair, and with spacing twice as wide. If this mesh is properly coated, it would collect even more water. According to MIT, which just released video of the harvesters in action, such optimization efforts have improved efficiency by 500 percent.
Since these mesh-based fog harvesters are inexpensive to make—and their passive design means no direct operating costs—they could be set up in deserts and other arid regions around the world with relative ease. Currently, the systems in Atacama Desert yield two litres of water (desalinated by the sun) a day per each square meter of mesh. Researchers believe they can get that figure up to twelve litres per day. This estimation, combined with the mesh's cheap manufacture, bodes well for those making their homes in arid regions.