Coating helps cotton soak mist water in bulk

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Amsterdam, Jan 23 (IANS) A revolutionary coating permits cotton to absorb roughly three-and-a-half times its own weight of water from misty air or fog.

The coated cotton releases the collected water by itself, as it gets warmer, making the material a potential solution to provide water to desert regions, especially for agricultural purposes.

Researchers from the Eindhoven University of Technology, the Netherlands, and Hong Kong Polytechnic University, applied a coating of PNIPAAm, a polymer, to the cotton fabric, the journal Advanced Materials reports.

At lower temperatures, this cotton has a sponge-like structure at microscopic level. Up to a temperature of 34 degrees Celsius it is highly hydrophilic; in other words, it absorbs water strongly, according to a Eindhoven and Hong Kong Polytechnic statement.

Through this property the cotton can absorb 340 percent of its own weight of water from misty air compared with only 18 percent minus PNIPAAm coating.

Conversely, once the temperature rises, the material becomes hydrophobic or water-repellant, and above 34 degrees Celsius, the cotton releases all the absorbed water, which is totally pure. The research shows that this cycle can be repeated many times.

Beetles in desert areas can collect and drink water from fogs, by capturing water droplets on their bodies, which roll into their mouths. Similarly, some spiders capture humidity on their silk network. This was the inspiration for this new coated-cotton material, which collects and releases water from misty environments simply as the temperature changes throughout the day.

This property implies that the material may potentially be suitable for providing water in deserts or mountain regions, where the air is often misty at night. According to Eindhoven researcher Catarina Esteves, a further advantage is that cotton fabric is cheap and can be easily and locally produced.

The polymer used is not particularly costly.

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