Manufactured Article with a Nanostructured Surface
The present invention concerns a manufactured article comprising at least one 1 nanostructured surface, wherein: said nanostructured surface is made of a material having a surface energy of less than 25 m J/m 2 , preferably less than 20 m J/m 2 , and comprises an array of contiguous cells defining cavities, the cavities of the cells being separated from each other by intermediate solid 20 material walls, and the cavities have an average height (H) and an average radius (R) which meet the conditions: R≧5 nm, preferably R≧10 nm; 2 R≦250 nm, preferably R≦200 nm, better R≦150 nm and more preferably R≦100 nm; and H≦3R. The invention concerns also a method for designing a nanostructured surface comprising an array of juxtaposed cells defining cavities separated from each other by solid 30 intermediate walls.
1 .- 16 . (canceled)
17 . A manufactured article comprising at least one nanostructured surface, wherein:
the nanostructured surface is made of a material having a surface energy of less than 25 mJ/m 2 , and comprises an array of contiguous cells defining cavities; and
the cavities of the cells are separated from each other by intermediate solid material walls and open to the environment; and
the cavities have an average height (H) and an average radius (R) wherein:
R≧5 nm;
R≧250 nm; and
H≧3R.
18 . The manufactured article of claim 17 , wherein:
R≧10 mm; and
R≦200 mm.
19 . The manufactured article of claim 18 , wherein R≦150 mm.
20 . The manufactured article of claim 18 , wherein R≦100 mm.
21 . The manufactured article of claim 17 having a sinking (α) equal to or lower than 50%, wherein:
α
(
%
)
=
h
H
100
where h is a wetting height by a liquid of the cavity intermediate wall and H is an average height of the cavity.
22 . The manufactured article of claim 21 , wherein sinking (α) is from 10% to less than 30% and cavity average height H≦1.5 R.
23 . The manufactured article of claim 21 , wherein sinking (α) is less than 10% and cavity average height H≦0.5 R.
24 . The manufactured article of claim 21 , wherein sinking (α) is determined by freezing a liquid or hardening a fluid while keeping a same surface tension for the fluid as the liquid to probe and measure the sinking by checking shape of the solidified liquid by SEM (scanning electron microscopy).
25 . The manufactured article of claim 21 , wherein sinking (α) is calculated using the theoretical model:
α
=
(
1
+
R
H
f
(
θ
adv
)
)
(
P
a
+
2
γ
cos
θ
adv
R
)
-
V
i
V
0
P
0
P
a
+
2
γ
cos
θ
adv
R
wherein:
γ is liquid surface tension;
P a is hydrostatic pressure→P a =P 0 +ρgz+ΔP;
P 0 is atmospheric pressure;
ρgz is pressure caused by gravity of a liquid drop;
ΔP is external pressure applied onto the drop;
R is average radius of the cavity;
H is average height of the cavity;
d is average distance between two cavities;
θ adv is advancing angle of the liquid onto a flat surface, made of a same material;
V 0 is geometrical volume of one cavity→V 0 =πR 2 H;
Vi is total volume of the cavity including the volume of air trapped by the liquid when it contacts the surface
->
Vi
=
π
R
2
H
+
3
2
(
2
R
+
d
)
2
wherein e is a thickness of an air layer trapped by a liquid; and
f(θ): coefficient→ for cylindrical cavity:
f
(
θ
)
=
1
-
sin
θ
6
cos
θ
[
3
+
(
1
-
sin
θ
)
2
cos
θ
2
]
wherein the liquid is linoleic acid and ΔP=2.5 10 4 Pa, and wherein, if the cavities have a wall side profile forming an angle β (different than 90°) with an horizontal plane of the nanostructured surface, θ adv is replaced by (θ adv +π/2−β).
26 . The manufactured article of claim 17 , wherein H>0.20 R
27 . The manufactured article of claim 17 , wherein a geometrical solid fraction (φ) of the cell array is equal to or lower than 0.7, the geometrical solid fraction (φ) is defined as from nanostructure top view perspective as a ratio of a solid surface area to total surface area of the nanostructured surface.
28 . The manufactured article of claim 27 , wherein the geometrical solid fraction (φ) of the sell array is equal to/or lower than 0.5.
29 . The manufactured article of claim 27 , wherein the geometrical solid fraction (φ) of the cell array is equal or lower than 0.3
30 . The manufactured article of claim 17 , wherein the array is a periodical array.
31 . The manufactured article of claim 17 , wherein the nanocavities are cylindrical.
32 . The manufactured article of claim 17 , wherein the nanostructured surface has been submitted to a hydrophobic and/or oleophobic treatment.
33 . The manufactured article of claim 32 , wherein the hydrophobic and/or oleophobic treatment consists of depositing a hydrophobic and/or oleophobic coating on the manufactured surface.
34 . The manufactured article of claim 33 , wherein the hydrophobic and/or oleophobic coating comprises fluorinated compounds.
35 . The manufactured article of claim 17 , wherein the manufactured article is a transparent article.
36 . The manufactured article of claim 35 , wherein the transparent article is an optical article.
37 . The manufactured article of claim 36 , wherein the transparent article is an ophthalmic lens.
38 . A method for designing a nanostructured surface comprising an array of juxtaposed cells defining cavities separated from each other by solid intermediate walls, the method comprising:
obtaining a map of areas of different values of a sinking (α) as a function of a radius (R) and a height (H) of the cavities, the values of the sinking (α) calculated using the theoretical model:
α
=
(
1
+
R
H
f
(
θ
adv
)
)
(
P
a
+
2
γ
cos
θ
adv
R
)
-
V
i
V
0
P
0
P
a
+
2
γ
cos
θ
adv
R
wherein:
γ is liquid surface tension;
P a is hydrostatic pressure→P a =P0±ρgz+ΔP;
P 0 is atmospheric pressure;
ρgz is pressure caused by gravity of a liquid drop;
ΔP is external pressure applied onto the drop;
R is average radius of the cavity;
H is average height of the cavity;
d is average distance between two cavities;
θ adv is advancing angle of the liquid onto a flat surface, made of a same materials;
V 0 is geometrical volume of one cavity→V 0 =πR 2 H;
Vi is total volume of the cavity including the volume of air trapped by the liquid when it contacts the surface
->
Vi
=
π
R
2
H
+
3
2
(
2
R
+
d
)
2
wherein e is a thickness of an air layer trapped by a liquid; and
f(θ): coefficient→ for cylindrical cavity:
f
(
θ
)
=
1
-
sin
θ
6
cos
θ
[
3
+
(
1
-
sin
θ
)
2
cos
θ
2
]
wherein the liquid is linoleic acid and ΔP=2.5 10 4 Pa, and wherein,if the cavities have a wall side profile forming an angle β (different than 90°) with an horizontal plane of the nanostructured surface θ adv is replaced by (θ adv +π/2−β);
selecting values of radius (R) and height (H) for the cavities of a desired sinking value; and
forming the cell array with the selected values for the radius (R) and height (H) of the cavities.