The development of a new inexpensive treatment for cotton fabric could help boost efforts to collect water from fog or mists in desert regions, as it is not only remarkably effective in absorbing water but also releases it just as easily.
In extremely arid regions, fog or mist harvesters can be a fairly effective method for collecting water but they generally require a strong air flow to function. This new treated fabric is effective without the need for wind, and can also be used to collect and release water where it is most needed for agricultural purposes -- directly on the ground.
Researchers at Eindhoven University of Technology (TU/e), working together with researchers at the Hong Kong Polytechnic University (PolyU), found that when a coating of a polymer, PNIPAAm, is applied to cotton fabric, it allows the fabric to absorb large amounts of water (up to 340% of its own weight).
The treated fabric is much more hydrophilic than the fabric by itself (which only absorbs about 18% of its own weight), and yet when the temperature gets warmer, the fabric becomes hydrophobic and releases all of the absorbed water (as pure water) without any other further action. Researchers say the process can be repeated over and over without further treatment.
"The reversible switching between absorbing-superhydrophilic/releasing-superhydrophobic states results from structural changes of a temperature-responsive polymer grafted on the very rough fabric-surface. This material and concept presents a breakthrough into simple and versatile solutions for collection, uni-directional flow, and purification of water captured from the atmosphere." - Advanced Materials
According to Dr Catarina Esteves, a TU/e researcher, the basic cotton fabric is cheap and easy to produce locally, and the polymer used for the treatment is not particularly costly, so this could be an inexpensive and effective solution for harvesting atmospheric water vapor in arid regions.
In addition, the fabric treatment may also eventually find its way into athletic or outdoor gear, where managing moisture is a concern. The results of the team's research are published in the journal Advanced Materials: Temperature-Triggered Collection and Release of Water from Fogs by a Sponge-Like Cotton Fabric.