Super water-repellent materials are now durable enough for the real
world

Date:
June 3, 2020
Source:
Aalto University
Summary:
Superhydrophobic materials have long promised surfaces that never
needed cleaning, or medical equipment that no microbe could ever
possibly stick to -- but have always been let down by the fact
they are very easily damaged. A new armor-plated water repelling
material can withstand anything the scientists throw at it.



FULL STORY ========================================================================== Superhydrophobic surfaces repel water like nothing else. This makes
them extremely useful for antimicrobial coatings -- as bacteria,
viruses and other pathogens cannot cling to their surfaces. However, superhydrophobic surfaces have one major flaw -- they are extremely
susceptible to cuts, scratches or dents. If a superhydrophobic surface
gets damaged, the damaged area can trap liquids and the benefits of the
coating are lost. Now, however, a collaboration between researchers
in China and Finland has developed an armour-plated superhydrophobic
surface which can take repeated battering from sharp and blunt objects,
and still repel liquids with world-record effectiveness.


==========================================================================
The research -- which is the cover feature of this week's issue of Nature
- - has designed superhydrophobic surfaces that can be made out of metal, glass, or ceramic. The superhydrophobic properties of the surface come
from nano-sized structures spread all over it. The trick is to pattern
the surface of the material with a honeycomb-like structure of tiny
inverted pyramids. The fragile water-repellent chemical is then coated
on the inside the honeycomb. This prevents any liquid from sticking to
the surface, and the fragile chemical coating is protected from damage
by the pyramid's walls.

"The armour can be made from almost any material, it's the interconnection
of the surface frame that makes it strong and rigid," says Professor
Robin Ras, a physicist at Aalto University whose research group was
part of the project. "We made the armour with honeycombs of different
sizes, shapes and materials. The beauty of this result is that it is a
generic concept that fits for many different materials, giving us the flexibility to design a wide range of durable waterproof surfaces."
As well as their useful antimicrobial properties for biomedical
technology, superhydrophobic surfaces can also be used more generally
in any application requiring a liquid-repellent surface. One example
is photovoltaics, where the build-up of moisture and dirt over time
blocks the amount of light they can absorb, which reduces electricity production. Making a solar panel out of a superhydrophobic glass surface
would maintain their efficiencies over long periods of time. Furthermore,
as solar cells are often on roof tops and other difficult to reach
locations, the repellent coatings would cut down the amount of cleaning
that is needed.

"By using the decoupled design, we introduce a new approach for designing
a robust superhydrophobic surface. Our future work would be to push
this method further, and to transfer robust superhydrophobic surfaces to different materials and its commercialization" said Professor Xu Deng,
the leader of the group at the University of Electronic Science and
Technology of China in Chengdu who took part in this research.

Other desirable applications for superhydrophobic surfaces include
in machines and on vehicles, where conditions can be very tough for
brittle materials for long periods of time. To simulate these working environments, the researchers subjected their new surfaces to extreme conditions, including baking them at 100 DEGC nonstop for weeks,
immersing them in highly corrosive liquids for hours, blasting them
with high-pressure water jets, and subjecting them to physical exertion
in extreme humidity. The surfaces were still able to repel liquid as effectively as before.

Now that the strengths of this new material design have been
demonstrated, future research will explore its broad potential in
real-world applications.


========================================================================== Story Source: Materials provided by Aalto_University. Note: Content may
be edited for style and length.


========================================================================== Journal Reference:
1. Dehui Wang, Qiangqiang Sun, Matti J. Hokkanen, Chenglin Zhang,
Fan-Yen
Lin, Qiang Liu, Shun-Peng Zhu, Tianfeng Zhou, Qing Chang, Bo
He, Quan Zhou, Longquan Chen, Zuankai Wang, Robin H. A. Ras, Xu
Deng. Design of robust superhydrophobic surfaces. Nature, 2020;
582 (7810): 55 DOI: 10.1038/s41586-020-2331-8 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200603132539.htm https://www.sciencedaily.com/releases/2020/06/200603132539.htm

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