Nature works with nanotechnology to extract water from thin air

A team of chemical researchers from the University of Sydney has honed in on a new technology that could lead to the ability to capture water from moist air.

The technology is inspired by an example of natural engineering, the surface structure on the back of a beetle native to the Namib Desert in southern Africa.

The researchers, from the School of Chemistry and Australian Institute for Nanoscale Science and Technology (AINST), which launched last year, have taken inspiration from this natural structure to design a viable coating technology for atmospheric water capture, to be used in circumstances of drought, emergency or isolation from the main water grid.

The results were published recently in the American Chemical Society journal Applied Materials & Interfaces.

The Physosterna cribripes desert beetle has a microstructured elytra enabling it to collect atmospheric moisture: the surface of the beetle’s back is covered in a number of microscopic bumps that are water-loving, in a background that is waxy and water-repellent.

This particular structure and chemistry allows the beetle to nucleate water droplets condensing from the moist winds blowing at dawn from the desert, and then to get the droplet to slide to its mouth.

Co-author and leader of the AINST domain in Molecular Nanoscience, Associate Professor Chiara Neto, said her team’s approach used the spontaneous formation of micropatterns in thin polymer films from nanoscale intermolecular forces that lead to the instability, and were therefore intrinsically low-cost and up-scalable.

“We have been working in the area of biomimetic material for a few years now, and the idea of biomimetic water capture is particularly interesting for its potential to benefit the sustainable use of resources,” Associate Professor Neto said.

“In our most recent paper, we have refined our pattern formation approach using specific solvents for the polymer molecules in use, and made the approach even more amenable to large scale use.

“Importantly, we have identified the micropattern size and distribution that are most effective in nucleating and collecting water droplets without any energy input.

“Some of the patterns that we have designed are able to collect substantially more water (57% more in volume) than flat plastic sheets under harsh circumstances, for example under low humidity or with no active cooling of the surface. In practice, what this means is that exposing our micropatterned surfaces to the night sky will result in more dew events than on a flat plastic sheet.

“In an emergency or drought situation, this difference could literally mean the difference between life and death.”

Dr Omar Al-Khayat, who completed his PhD thesis on this topic late last year, said he had already applied and tested these patterns to large three-dimensional tubes.

“In the future, we can envisage applying these patterns to large sheets exposed to the night sky, to collect water from humid air, for irrigation or drinking,” Dr Al-Khayat said.