Tech Briefs Magazine - May 2021 - 40
Materials & Coatings
Smart Aerogel Turns Air into Drinking Water
This invention achieves sustainable freshwater production in a variety of climates
at minimal energy cost.
National University of Singapore
I
n the Earth's atmosphere, there is water
uously switch between attracting water
and releases the water. When there is sunthat can fill almost half a trillion
and repelling water. The smart aerogel
shine, the smart structure can further
Olympic swimming pools. But it has long
autonomously gathers water molecules
boost the water release by transitioning to
been overlooked as a source for potable
from the air, condenses them into a liquid,
a complete water-hating state.
water. Researchers now have created a
Ninety-five percent of the water
substance that extracts water from air
vapor that goes into the aerogel
without any external power source.
comes out as water. In laboratory tests,
The team created a type of aerogel
the aerogel produced water nonstop
- a solid material that weighs almost
for months. The researchers tested
nothing. Under the microscope, it
the water and found that it met World
looks like a sponge but it does not have
Health Organization standards for
to be squeezed to release the water it
drinking water.
Other scientists' work previously
absorbs from the air. It also does not
devised ways to extract water from
need a battery. In a humid environair but the designs had to be powment, one kilogram of it will produce
ered by sunlight or electricity and
17 liters of water a day.
had moving parts that had to be
The trick is in the long, snake-like
opened and closed.
molecules - known as polymers -
For more information, contact Carolyn
building up the aerogel. The long- Samples of the new aerogel absorb water vapor from
the air and turn it into water without any external
chain polymer consists of a sophisticat- power source. The plastic sample tubes contain raw Fong at carolyn@nus.edu.sg; +65 6516
5399.
ed chemical structure that can contin- ingredients that give the aerogel its special properties.
Wafer-Thin Nanopaper Changes from Firm to Soft at the
Touch of a Button
Bioinspired cellulose nanofibrils can be controlled by electricity.
Johannes Gutenberg-Universität Mainz, Mainz, Germany
A
team of researchers has developed
wafer-thin, stiff nanopaper that
instantly becomes soft and elastic at the
push of a button. The material is
equipped with a mechanism so that the
strength and stiffness can be modulated
via an electrical switch. As soon as an
electric current is applied, the nanopaper becomes soft; when the current flow
stops, it regains its strength. This switching capability could be used for damping materials.
The team was inspired by sea cucumbers, which have a special defense mechanism. When attacked by predators in
their habitat on the sea floor, sea cucumbers can adapt and strengthen their tissue so that their soft exterior immediately stiffens. The researchers mimicked the
basic principle in a modified form using
an attractive material and an equally
attractive switching mechanism.
The scientists used cellulose nanofibrils
extracted and processed from the cell wall
of trees. Nanofibrils are even finer than
the microfibers in standard paper and
result in a completely transparent, almost
glass-like paper. The material is stiff and
strong - appealing for lightweight construction. Its characteristics are comparable to those of aluminum alloys.
The team applied electricity to these cellulose nanofibril-based nanopapers. By
means of specially designed molecular
changes, the material becomes flexible.
The process is reversible and can be controlled by an on/off switch. This is relevant
for mechanical materials, which can thus
be made more resistant to fracture or for
adaptive damping materials, which could
40
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switch from stiff to compliant when overloaded, for example.
At the molecular level, the process
involves heating the material by applying
a current and thus reversibly breaking
cross-linking points. The material softens
in correlation with the applied voltage:
the higher the voltage, the more crosslinking points are broken and the softer
the material becomes.
While currently a power source is needed to start the reaction, the next goal
would be to produce a material with its
own energy storage system, so that the
reaction is essentially triggered internally
as soon as an overload occurs and damping becomes necessary.
For more information, contact Professor
Dr. Andreas Walther at andreas.walther@
uni-mainz.de; +49 6131 39-23005.
Tech Briefs, May 2021
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Tech Briefs Magazine - May 2021
Table of Contents for the Digital Edition of Tech Briefs Magazine - May 2021
Tech Briefs Magazine - May 2021 - Intro
Tech Briefs Magazine - May 2021 - Sponsor
Tech Briefs Magazine - May 2021 - Cov1
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