Inspired by a resident of one of the driest and most inhospitable places on our planet, a team of researchers based at Rice University has developed a device capable of capturing and collecting water from the atmosphere that could eventually be used to supply water to civilizations inhabiting arid areas. The study has been published in Applied Materials & Interfaces.
The Namib Desert is an extremely hostile environment; with sands that can reach 60oC (140oF), gale force winds and extremely rare rainfall, life in this region is presented with a challenge to say the least. But one insect has evolved a clever way to cope with the extreme dry- the Namib Desert beetle (Stenocara). This bug can capture drinking water from periodic early-morning fogs that sweep across the desert just twice a year using its shell.
The surface of Stenocara’s back is covered with bumps; the peaks of these bumps are smooth and attract water molecules, whereas the troughs are waxy just like a non-stick surface and repel water. It is thanks to this architecture that Stenocara is able to collect water droplets from the fog that can be subsequently guided into the beetle’s mouth.
In order to recreate this remarkable water-collecting system, scientists first generated forests of vertically aligned microscopic carbon cylinders, or carbon nanotubes. They then coated both sides of the forest with polymers, one of which was hydrophilic in order to capture the water from the air and the other superhydrophobic to prevent the collected water from escaping the system.
The result is a structure, called a “hygroscopic scaffold” that is able to draw moisture from the air without the need for an external power source, which can then be stored until it is needed. “You can squeeze the forest to take the water out and use the material again,” said first author Sehmus Ozden in a news-release.
The researchers discovered that the efficiency of the system is dependent humidity. When they tested a small piece (0.25 square cms) of the material in dry conditions it was able to draw 27.4% of its weight in water over a period of 11 hours, whereas when it was tested in a humid environment it could collect 80% of its own weight over 13 hours.
Although the team believe that this could be an efficient system to bring water to arid regions that do not experience adequate rainfall, they note that production costs will first need to be significantly reduced before it is viable. However, author Robert Vajtai told Science that scaling-up the technology “would not raise great challenges.”