Artificial fibres that can collect water from the air, much like how spider silk gathers dew, could be used for large-scale water collection from fog.
In places where the availability of drinking water can be low, harvesting water from air tends to be an energy-intensive process. Condensation, a common method, usually requires a surface that is kept cooler than the air temperature.
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Now, at Beihang University in China and her colleagues have designed artificial microfibre threads covered in spiral-shaped bumps that can passively attract huge droplets of water to condense on them.
To make the bumps, a plastic microfibre is first coated with a layer of hydrophilic, or water-loving, titanium dioxide. This creates bulges in the fibre, which the researchers cracked into a helical shape using high temperatures.
The helix creates a larger surface area for a water droplet to attach to and forms stronger bonds with it, which means each bump can carry 2000 times more water than the volume of the bump itself.
Zheng and her team made a device consisting of 420 helical bumps in a 6-square-centimetre area, which, when left in a foggy environment, could collect about 0.1 litres of water per day, with the liquid dropping into a container beneath the fibres.
The device would need to be around 17 times larger, about 108 square centimetres 鈥� or about 10.4cm by 10.4cm across 鈥� to produce enough drinking water for one person, says Zheng.
The work is taking inspiration from biological processes to address the issue of water shortage, says at the University of Hong Kong. 鈥淭he smart grooves with gradient wettings are smartly constructed on spider silk for atmospheric water harvesting, it looks interesting, but highly demanding preparation is also required.鈥�
Similar artificial webs already exist, but their water collection abilities tend to decline over time. The titanium oxide bumps, however, can self-repair by reacting with water molecules when exposed to ultraviolet light. This reaction maintains the material鈥檚 hydrophilic properties, ensuring it maintains a high affinity for creating bonds with water.
Advanced Functional Materials
