Reinforcement defended superhydrophobic materials from abrasive

Chinese and Finnish
material engineers
increased
stability of nanostructured
superhydrophobic
material, adding reinforcing
the pyramidal microstructure.
This
by the way, you can make superhydrophobic metal surface, silicon, glass
and
ceramics,
and
superhydrophobic
properties are stored
even after 1000 cycles
abrasive
processing.
Results
research published
in the journal Nature.

Superhydrophobic
called a surface with boundary angle
wettingwith water
more
150 degrees. Such
materials are always
stay dry
not populated with microorganisms and
can also self-clean that
makes them very attractive for
use in medicine and technology.
Superhydrophobicity
is achieved through a combination of
strong
surface tension
at the boundary liquid-solid
body, and also due to the texturing
surface, which minimizes
area
contact
with
the liquid phase. Texturizing nanostructures (tiny
the roughness of the surface) are very fragile
so
superhydrophobic materials quickly
lose their properties under various
mechanical influences.

Xu
Deng (Xu
Deng)
from
The Chinese University of electronic
Sciences
and technology and
Robin RAS (Robin H. A. Ras) from
The University of Aalto in Finland together
with his colleagues managed to do
superhydrophobic materials mechanical
stable.
For
this video
textured
surface on two levels, adding
to ensure water repellency
nanostructures of larger
of the microstructure.
The latter had to serve as a
armor that protects fragile
nanostructures from mechanical
effects.
For
to make
the material is durable and at the same time not
to lose water needed
to correctly calculate the geometry of the reinforcing
microstructures. For
evaluation
hydrophobicity
textured surface authors
used
the ratio
Cassie-Baxter

cos
θ =
f*(1 + cos θy)
− 1

Where
θ

angle,
f
— share
contact between solid and liquid,
and θy

Jungian
the wetting angle of the material
which is determined from the ratio
the three surface energies (solid
body — liquid, solid — gas, and
liquid — gas). Option
θy
for
each material is constant, while
as f
depends
from texturing: the smaller it is,
the
more hydrophobic
will
surface
(if
very heavily textured surface
to reduce f,
can be done even initially hydrophobic
hydrophilic material, however, such
the surface will be very unstable).
For
microstructure in the form of the same
geometrically correct projections, f
will
decrease with the decrease in the tilt angle
α
side
faces of the protrusion to the surface and
will reach a maximum when the protrusion will
perpendicular (see figure). In
the same time, the decrease in the angle α will make the microstructure
less durable.
With
using the simulation method
finite element the authors found,
what is the optimal
ratio of strength and hydrophobicity
can be achieved when tilting the verge
guide
about
125
degrees.

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