Water-Harvesting Cotton Could Help Sustain Agriculture in Arid Places

In arid areas, clean flowing water is always in short supply. However, once temperatures cool at night, mists and fogs nourish plant and animal life. Inspired by species of beetles and spiders that have adapted to gather droplets from the air, a team from the Eindhoven University of Technology (TU/e) and the Hong Kong Polytechnic University (PolyU) have developed a cotton fabric coated with a special polymer that collects and retains moisture. The team, who will publish their results in the journal, Advanced Materials later this month, found that with the coating the fabric was able to absorb 340% of its own weight as compared to 18% without the polymer. Up to 93 degrees Fahrenheit, the material strongly attracts water. Once above that threshold, the microstructure changes, becoming completely closed and releasing pure water wherever it is placed. The cotton coated with the PNIPAAm compound has the further advantage of also being inexpensive. As a basic material, cotton can be grown and processed locally, and the coating can be added for roughly 12% of the entire cost of production under current conditions. Able to be placed directly on the ground to irrigate plants, the coated cotton does not need to rely on wind to drive moisture collection.

Researchers are also considering altering the the fabric for use in camping equipment and sportswear. Led by John Xin at PolyU and Dr. Catarina Esteves at TU/e, the scientists plan to further maximize the efficacy of the material and expect to be able to adjust the temperature at which the material switches from a water-collecting to a water-releasing state. The coated cotton has great implications for irrigation and hydration of arid regions, eliminating the need to transport water over long distances, purification systems, or containers.