Cotton with special coating collects water from fogs in desert
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| Eindhoven University of Technology |
Researchers at Eindhoven University of Technology (TU/e)
together with researchers at the Hong Kong Polytechnic University (PolyU), have
developed a special treatment for cotton fabric that allows the cotton to
absorb exceptional amounts of water from misty air: 340% of its own weight.
What makes this 'coated cotton' so interesting is that the cotton releases the
collected water by itself, as it gets warmer. This property makes of the coated
cotton materials a potential solution to provide water to the desert regions,
for example for agricultural purposes. The results of this research will be
published next month in the scientific journal Advanced Materials.
The
researchers applied a coating of PNIPAAm, a polymer, to the cotton fabric. At
lower temperatures, this cotton has a sponge-like structure at microscopic
level. Up to a temperature of 34°C it is highly hydrophilic, in other words it
absorbs water strongly. Through this property the cotton can absorb 340 % of
its own weight of water from misty air -- compared with only 18% without the
PNIPAAm coating.
Totally
pure water
In
contrast, once the temperature raises the material becomes hydrophobic or
water-repellant, and above 34°C the structure of the PNIPAAm-coated cotton is
completely closed. When these high temperatures are reached the cotton has
released all the absorbed water, which is totally pure. The research shows that
this cycle can be repeated many times.
Inspiration
from Nature
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.
Low-cost
material
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 TU/e researcher dr. Catarina Esteves a further advantage is that
the basic material -- cotton fabric -- is cheap and can be easily and locally
produced. The polymer coating increases the cost slightly, but with the current
conditions the amount required is only about 12%. In addition, the polymer used
is not particularly costly.
 |
| Eindhoven University of Technology |
Placed directly on the soil
Fine-mesh
'fog harvesting nets' are already being used in some mountains and dry coastal
areas, but these use a different principle: they collect water from misty air,
by droplets that gradually form on the nets and fall to the ground or a
suitable recipient. But this system depends on a strong air flow, wind. The
coated cotton developed the research team can also work without wind. In
addition, cotton fibers coated with this polymer can be laid directly where the
water is needed, for example on cultivated soil. The researchers are also
considering completely different applications such as camping tents that
collect water at night, or sportswear that keeps perspiring athletes dry.
Further
optimization
The
research was led by professor John Xin at PolyU and dr. Catarina Esteves at
TU/e. They now intend to investigate further how they can optimize the quality
of the new material. For example they hope to increase the amount of water
absorbed by the coated-cotton. Moreover they also expect to be able to adjust
the temperature at which the material changes from water-collecting to the
water-releasing state, towards lower temperatures.
Source: Eindhoven
University of Technology
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Posted by Unknown
on Wednesday, January 23, 2013.
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