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New Polymer-Coated Cotton Absorbs 340 Percent Its Own Weight

January 21, 2013
Image Caption: (Left) At temperatures above 93.2 degrees Fahrenheit the PNIPAAm-cotton has a closed structure at the microscopic level. (Right) At low temperatures the structure of PNIPAAm-cotton is open, allowing for absorption. Credit: Eindhoven University of Technology

Lawrence LeBlond for redOrbit.com – Your Universe Online

Bringing water to the extremely arid regions of the planet has been a hard-fought battle for millennia. Ancient cultures searched out inventive ways of rerouting water to arid habitats. And through ever-evolving processes, modern cultures have found similar ways of doing the same.

A new study, however, could change how this millennia-old practice of water relocation has been conducted, offering insight into a new age, potentially providing the driest regions of earth with water.

Researchers at Eindhoven University of Technology (TU/e) along with colleagues from Hong Kong Polytechnic University (PolyU), have developed a special treatment for cotton that allows it to absorb massive amounts of water from misty air.

The treatment, a polymer known as PNIPAAm, was applied to the cotton fabric allowing it to absorb 340 percent of its own weight. But without this PNIPAAm coating, the cotton is only able to soak up 18 percent of its own weight.

Ahead of publishing the work in next month´s scientific journal Advanced Materials, the researchers demonstrate how this polymer-coated, highly-hydrophilic cotton can sponge up water at temperatures up to 93.2 degrees Fahrenheit. Once temperatures surge past 93.2F, the cotton is able to release the water by itself, without the need for human interference. And best of all, this water being released is totally pure of impurities.

The researchers said this process can be repeated many times on a single-coated cotton fabric.

The team said the research was inspired from nature. Beetles in desert regions can collect and drink water from fogs, capturing tiny droplets of water on their bodies, which then roll into their mouths. Some spiders have been observed engaging in similar activities, capturing humidity on their networks of silk. The researchers drew on this nature-made technology to develop a material that can implement a capture-release system.

The team said this material may prove suitable in providing water to desert or mountain regions, where the air is most often misty at night.

Dr. Catarina Esteves, a researcher at TU/e and coauthor of the study said using cotton is advantageous where it is cheap and can be easily and locally produced. The polymer would increase the cost slightly, but with current conditions the amount required is only about 12 percent.

Fog harvesting nets´ are already being used in some mountain regions and arid coastal regions, but are based on different principles. Water is collected from the misty air as droplets form on the nets and then fall to the ground or a suitable vessel below. However, this system depends on strong air flow.

The polymer-coated cotton can work without wind, and the absorbed water doesn´t need to be immediately drained, but can be held as long as the temperatures remains below 93.2F. The cotton can be distributed directly where water is needed as well.

This technology could also be used to keep perspiring athletes dry.

Jon Xin, a study coauthor from PolyU, said the team now intends to investigate how they can optimize the quality of the new material. For one, they hope they can increase the amount of water absorbed by the cotton. Another goal is to also adjust the temperature (lowering it) at which the material changes from a water-absorbing to water-releasing state.


Source: Lawrence LeBlond for redOrbit.com - Your Universe Online



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