Researchers develop crystals to harvest water from air, inspired by desert life

The design of the novel type of smart crystals, which the researchers named Janus crystals, is inspired by desert plants and animals, which can survive in arid conditions. Desert beetles and lizards, for example, have evolved to develop surface structures that have both hydrophilic and hydrophobic areas and effectively capture moisture from the air. Water is attracted to the hydrophilic areas and droplets are accumulated and transported through the hydrophobic areas.

The findings are presented in the paper titled "Efficient Aerial Water Harvesting with Self-Sensing Dynamic Janus Crystals," recently published in the Journal of the American Chemical Society. The researchers chose three chemically versatile organic compounds from which they grew elastic organic crystals. They then tested how each of these materials interacted with the airborne water, which led to the creation of the new water-collecting materials, Janus crystals, that contain both hydrophilic and hydrophobic regions on the surface level, one to capture water and one to transfer it to a receptacle for collection. The Janus crystals capture humidity from humid air with the highest-to-date water collection efficiency. The crystals' narrow and light-translucent structures enable researchers to monitor the collection and condensation of fog droplets in real time by using light.

Desalination is a widely used method to produce potable water, however an energy-intensive process is required to separate the dissolved salt in saltwater. In contrast, the process of condensation of aerial humidity or fog utilized by the Janus crystals is spontaneous under ambient conditions and can be performed without the input of energy, potentially providing an endless source of clean water. Unlike previously reported porous organic crystals, the Janus crystals combine water-collection and water-delivery functions at their surface, creating a highly efficient water harvesting process that maximizes the amount of collected water at ambient conditions.

"The earth's atmosphere contains an abundance of untapped fresh water, but we desperately need materials that can efficiently capture and collect this humidity and condense it into potable water," said Naumov. "The crystals developed by our team not only capitalize on the mechanical compliance and optical transparency of organic crystals, but also pave the way for the design of active, self-sensing, and efficient surface-active harvesters which, when used at a larger scale, can help us combat water scarcity at a societal level.