Evrim Yazgin
Cosmos science journalist
A sponge-like device produced by engineers in Australia and China can capture water from thin air. The researchers say it could be used in arid regions of the world to collect water.
A device, described in a paper published in the Journal of Cleaner Production, works in areas of low humidity where other technologies such as fog harvesting or radiative cooling struggle.
The new design is effective in humidity levels of 30% to 90% and temperatures from 5°C to 55°C.
The spongy material is based on that schooltime favourite, balsa wood. The wood’s naturally spongy structure was modified with lithium chloride, iron oxide nanoparticles, a carbon nanotube layer and other specialised features. The composite material can absorb water and release it on demand.
“Billions of people around the world lack access to drinkable water, and millions die from water-borne diseases every year,” says corresponding author Derek Hao, from RMIT University in Melbourne.
“The main component, balsa wood, is widely available, biodegradable and cheap, and the manufacturing process is not complex, which could enable mass production,” Hao says. “The demonstrated stable performance over multiple cycles and in various environmental conditions indicates longevity and cost-effectiveness.”
The water-from-air device absorbed about 2mL of water per gram of material at 90% relative humidity under laboratory conditions and released nearly all the water within 10 hours under sun exposure. This doesn’t seem like a lot, but it is higher than most other known methods and at less cost.
“In outdoor tests, our device captured 2.5 milliliters of water per gram overnight and released most of it during the day, achieving a daily water collection efficiency of 94%,” says senior author Junfeng Hou from Zhejiang A&F University in China.
“At 30% humidity, our device absorbed water at about 0.6 mL per gram. These results highlight its potential use in off-grid, solar-driven water harvesting systems.”
“The device retained its flexibility and water-absorbing function even after being stored at −20°C for 20 days, demonstrating excellent freeze resistance,” says Hao. “Its moisture absorption–release performance was stable across 10 consecutive cycles, with less than 12% decline in efficiency.”
The current invention is a lab-based prototype.
“The demonstration unit size is 15 cubic millimeters. It would be very easy to prepare a larger unit, or we can use the units to form an array,” Hao says.
“Its ability to harvest potable water from the atmosphere using only sunlight makes it invaluable in disaster-stricken areas where traditional water sources are compromised. The system’s portability and reliance on renewable energy further enhance its applicability in such contexts.”
