Humidity-capturing crystals may help with Earth's freshwater poverty

A novel method of harvesting water from naturally occurring sources, such as fog and dew, has been reported in a new study published in Nature Chemistry on March 16.

With water scarcity presently affecting hundreds of millions worldwide- estimated to reach 1.8 billion people by 2025- the discovery at least inspires new technology trying to tackle some of the planet's most pressing water problems.

A 'new underlying principle of water collection'

Researchers Patrick Commins and Marieh B. Al-Handawi at NYU Abu Dhabi (NYUAD) noticed for the first time how water spontaneously condensed from vapor to liquid form and moved across the surface of an organic crystal that was slowly sublimating. 

Sublimation is when a substance can change from a solid to a gas without becoming liquid.

They found this process to be brought on by alterations in the width of tiny channels that form over time on the surface of the crystal and direct the condensed water across its surface.

In the paper, they describe this process on crystals of 'hexachlorobenzene,' a compound that is often used as a fungicide. 

Due to sublimation, the surface of this substance has a rigid topography with well-defined parallel channels. Dust and even metallic nanoparticles were seen to move autonomously through the channels.

It was discovered that the condensed aerial water, which migrates along the channels as their cross-section and width change over time, is responsible for these particles' mobility.

Previous attempts at achieving autonomous water flow have involved either surface chemical alterations or carefully engineered microchannels, as well as on the surfaces of some natural systems, including some plants or insects. 

"The motion of water on solid surfaces is one of the most fundamental phenomena found in nature," said co-author Panče Naumov in a press release.

"Through millennia-long evolutionary processes, surfaces of natural organisms have been optimized for efficient transport of water for a variety of life-supporting functions. Plants have been seen to do this by moving water against gravity." 

The results of this new study have the potential to direct the development of new technologies to exploit water that is presently exclusively utilized by a few desert plants and animals, such as dew and fog, for survival.

"Our team has discovered a new way to move water across a dynamic solid surface, a fundamentally new underlying principle of water collection. This can provide inspiration for emerging technologies that could potentially maximize the efficiency of experimental systems used for the collection of aerial humidity," Naumov concluded. 

The complete study was published in Nature Chemistry on March 16 and can be found here.