By Liat Clark, Wired UK

A US startup is developing a self-filling water bottle that sucks moisture from the atmosphere to create condensation, in the same way the humble Namib desert beetle does.

The beetle, endemic to Africa's Namib desert—where there is just 1.3cm of rainfall a year—has inspired a fair few proof-of-concepts in the academic community, but this is the first time a self-filling water bottle has been proposed. The beetle survives by collecting condensation from the ocean breeze on the hardened shell of its wings. The shell is covered in tiny bumps that are water attracting (hydrophilic) at their tips and water-repelling (hydrophobic) at their sides. The beetle extends and aims the wings at incoming sea breezes to catch humid air; tiny droplets 15 to 20 microns in diameter eventually accumulate on its back and run straight down towards its mouth.

NBD Nano, made up of two biologists, an organic chemist and a mechanical engineer, is building on past studies that constructed structurally superior synthetic copies of the shell. An earlier incarnation of the material was first constructed in 2006 by an MIT team—they dipped glass or plastic substrates into solutions of charged polymer chains over and over again to manipulate the surface make-up. Silica nanoparticles were then added to create a rougher, water-trapping texture, and a Teflon-like substance sealed it. Charged polymers and nanoparticles were then layered in patterns to create a contrast between rough and porous surfaces.

NBD Nano says it has achieved proof of concept with its dual water-attracting (superhydrophilic) and water-repelling (superhydrophobic) bottle design, and is currently working on a prototype and seeking funding. Incredibly, the team predicts that the bottle could collect between half a litre and three litres of water per hour, depending on the local environment.

"Dry places like the Atacama Desert or Gobi Desert don't have access to a lot of sources of water," cofounder Miguel Galvez told the BBC. "So if we're creating [several] litres per day in a cost-effective manner, you can get this to a community of people in Sub-Saharan Africa and other dry regions of the world. And if you can do it cheaply enough, then you can really create an impact on the local environment."

However it's not likely it will immediately be used in arid environments such as the Namib, but instead on green roofs and greenhouses. It may also be used by the military, before eventually becoming a portable, self-filling water bottle for rain-poor nations. The latter is "a conceptual design that one day could be feasible, although it could be years away" state NBD Nano. However, it is unlikely it could fulfill all a community's needs, from home use and cooking to farming, but would perhaps instead act as an emergency device.

The Namib beetle had already inspired the 2011 International Dyson Award-winner, Edward Linacre, who designed the Airdrop—an irrigation system that pumps then cools air through underground pipes to create condensation at plant roots.

Source: Wired.co.uk