The water-catching back of an African beetle may hold the key to saving drought-ridden countries.
Pulling water out of the air
SYDNEY // A small beetle in one of the most arid parts of Africa is helping scientists in Australia in their quest to secure reliable supplies of water in drought-hit regions. Native to the Namib Desert in southern Africa, the Stenocara beetle captures moisture on its back through tiny ridges and troughs, enabling it to convert particles of H2O in fast-moving fog that comes off the Atlantic Ocean into tiny beads of drinking water.
The insect's capacity to adapt and survive in one of the planet's most inhospitable places, where coastal areas receive less than 20mm of rain annually, has inspired academics in their search for innovative ways to fortify cities against drought. "The idea is that if we could tap into the amount of water that is already dispersed in the air we would have a huge source of drinking water at very low cost," explained Chiara Neto, an Italian-born lecturer in the School of Chemistry at the University of Sydney. "The Stenocara beetle has a very clever way of harvesting that water, basically condensing it spontaneously on the surface of its back."
The fog-catching beetle's secret lies in a series of hydrophilic - or water-loving - bumps that sit on a waxy hydrophobic, moisture-repelling background, which allows life-sustaining droplets to roll down into its mouth. "What we are trying to do is design a surface that does exactly the same thing, which harvests water from the atmosphere simply using a particular combination of chemistry and structure," said Ms Neto.
Solving the puzzle of the beetle's moisture-harnessing qualities has been occupying researchers in Australia for more than a year, although it has been a decade since a zoologist from Oxford University in Britain identified the special physiology of this African native. Since then, other scientists around the world have tried to emulate its ability to turn heavy, moist air into minute splashes of water but have mainly used methods that would be hard to reproduce on a commercial level.
The Sydney project, which is using material that should be cheap and easy to manufacture, involves biologists, chemists, engineers and mathematicians, who are all striving towards one goal: to mimic nature's genius on a large scale and to cover the roof of a house or the side of a building with plastic sheeting similar to the water-bearing surface of the Stenocara beetle. A small collection of these unique specimen are highly prized possessions in the chemistry laboratories at the University of Sydney, where Stuart Thickett, a post-doctoral researcher, has laboured for months testing two delicate synthetic films that are far thinner than a human hair, which imitate the body of the Namib Desert beetle.
"There can be weeks of work for seemingly little result then suddenly you have a big breakthrough," explained Mr Thickett. "There is so much in nature we can use for inspiration. There are many other examples of sea creatures creating nano-structures of calcium carbonate, for example, for carbon dioxide absorption. There's so many things we can do in replicating or mimicking nature's patterns with easy-to-use man-made materials. It is really quite exciting."
The research opens up a new front in the battle to safeguard water sources for a parched country, which is enduring its worst drought in memory, by capturing seemingly endless supplies from the humid air in coastal areas. "There is plenty of water - much more than we could ever use in the atmosphere at the moment. The humidity in the east coast of Australia on average is about 60 per cent, so we have more than enough water in the atmosphere. We just have to find clever, energy-efficient ways of capturing it," said Associate Professor Andrew Harris, the head of the laboratory for sustainable technology at the University of Sydney.
"If you can paint the side of your building with a material that captures that water without any energy penalty using just atmospheric conditions then you don't need to improve your existing dam [reservoir] infrastructure," Mr Harris added. Water security is a fundamental concern for Australians, who have built a highly urbanised nation on the world's driest inhabited continent, where there are fears that a long-standing drought may persist for decades while a thirsty population continues to expand.
Gordon Moyes, a member of the New South Wales state parliament who has chaired official inquiries into the scarcity of water resources, has argued that ingenious ways to guarantee supplies should be urgently pursued. "What we've got to do in Australia is think smarter and use less water," said Mr Moyes, who believes that a suite of measures should be employed, including piping water from the wet tropics to southern cities along with greater recycling and cloud seeding.
Researchers in Sydney hope their beetle-inspired work will complement existing sources and ward off the effects of serious drought. "Our method would probably aim to provide maybe 50 per cent of the water needs of a typical household, so we would still need dams," said Ms Neto. @Email:email@example.com