Mesh that captures moisture from fog

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Shreerang Chhatre of the Massachusetts Institute of Technology designed a fog-harvesting material that mimics the fog-harvesting strategy of the Namibian desert beetle. The beetle moves to a spot where the fog rolls in, raises its wings, and the fog condenses on the wings and rolls to the mouth. The wings have bumps that attract water and troughs that repel it; this way, drops collect on the bumps, then run off through the troughs without being absorbed, so that the water reaches the beetle’s mouth. Chhatre's design started with a mesh, rather than a solid surface like the beetle's. This is one improvement over nature for the purpose of capturing more water than the beetle would need. Chhatre boosted water output by refining the materials that the mesh is made from, attempting to strike a balance between hydrophilic materials that attract water droplets, and hydrophobic materials that then send them on their way down into the collection container.In some field tests, fog harvesters have captured one liter of water (roughly a quart) per one square meter of mesh, per day. Finding ways for local people without access to enough clean water will help the poor in many nations, and free up time from an often long process of hauling water. Fog-harvesting results in clean water, reducing the need for desalination plants in some areas.Source: Dizikes P. 2011. Out of thick air. MIT News

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To build larger fog harvesters, researchers generally use mesh, rather than a solid surface like a beetle’s shell, because a completely impermeable object creates wind currents that will drag water droplets away from it. In this sense, the beetle’s physiology is an inspiration for human fog harvesting, not a template. “We tried to replicate what the beetle has, but found this kind of open permeable surface is better,” Chhatre says. “The beetle only needs to drink a few micro-liters of water. We want to capture as large a quantity as possible.”

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Out of thick airMIT NewsApril 21, 2011
Peter Dizikes

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