Ultraphobic surface for high pressure liquids
View Patent ↗A durable ultraphobic surface that is capable of retaining ultraphobic properties at liquid pressures of one atmosphere and above. The surface generally includes a substrate portion with a multiplicity of projecting regularly shaped microscale or nanoscale asperities disposed so that the surface has a predetermined contact line density measured in meters of contact line per square meter of surface area equal to or greater than a contact line density value “Λ L ” determined according to the formula: Λ L = - 10 , 330 γcos ( θ a , 0 + ω - 90 ° ) where γ is the surface tension of the liquid in Newtons per meter, θ a,0 is the experimentally measured true advancing contact angle of the liquid on the asperity material in degrees, and ω is the asperity rise angle in degrees.
1. An ultraphobic surface comprising:
a substrate having a surface with a multiplicity of substantially uniformly shaped asperities thereon, each asperity having a common asperity rise angle relative to the substrate, the asperities positioned so that the surface has a contact line density measured in meters of contact line per square meter of surface area equal to or greater than a contact line density value “Λ L ” determined according to the formula:
Λ
L
=
-
10
,
330
γcos
(
θ
a
,
0
+
ω
-
90
°
)
where γ is the surface tension of a liquid in contact with the surface in Newtons per meter, θ a,0 is the experimentally measured true advancing contact angle of the liquid on the asperity material in degrees, and ω is the asperity rise angle in degrees, wherein the surface exhibits a liquid-solid-gas interface with the liquid at a pressure of at least one atmosphere.
2. The surface of claim 1 , wherein the asperities are projections.
3. The surface of claim 2 , wherein the asperities are polyhedrally shaped.
4. The surface of claim 2 , wherein each asperity has a generally square transverse cross-section.
5. The surface of claim 2 , wherein the asperities are cylindrical or cylindroidally shaped.
6. The surface of claim 1 , wherein the asperities are cavities formed in the substrate.
7. The surface of claim 1 , wherein the asperities are positioned in a substantially uniform array.
8. The surface of claim 7 , wherein the asperities are positioned in a rectangular array.
9. The surface of claim 1 , wherein the asperities have a substantially uniform asperity height relative to the substrate portion, and wherein the asperity height is greater than a critical asperity height value “Z c ” in meters determined according to the formula:
Z
c
=
d
(
1
-
cos
(
θ
a
,
0
+
ω
-
180
°
)
)
2
sin
(
θ
a
,
0
+
ω
-
180
°
)
where d is the distance in meters between adjacent asperities, θ a,0 is the experimentally measured true advancing contact angle of the liquid on the asperity material in degrees, and ω is the asperity rise angle in degrees.
10. A process of making an ultraphobic surface adapted for repelling a liquid at a pressure of at least one atmosphere in contact with the surface, the process comprising:
providing a substrate having an outer surface; and
forming a multiplicity of substantially uniformly shaped asperities on the outer surface of the substrate, each asperity having a common asperity rise angle relative to the substrate portion, the asperities positioned so that the surface has a contact line density measured in meters of contact line per square meter of surface area equal to or greater than a contact line density value “Λ L ” determined according to the formula:
Λ
L
=
-
10
,
330
γcos
(
θ
a
,
0
+
ω
-
90
°
)
where γ is the surface tension of the liquid in Newtons per meter, is the experimentally measured true advancing contact angle of the liquid on the asperity material in degrees, and ω is the asperity rise angle in degrees.
11. The process of claim 10 , wherein the asperities are formed by photolithography.
12. The process of claim 10 , wherein the asperities are formed by a process selected from the group consisting of nanomachining, microstamping, microcontact printing, self-assembling metal colloid monolayers, atomic force microscopy nanomachining, sol-gel molding, self-assembled monolayer directed patterning, chemical etching, sol-gel stamping, printing with colloidal inks, and disposing a layer of carbon nanotubes on the substrate.
13. A process for producing a surface having ultraphobic properties at liquid pressures up to a predetermined pressure value, the process comprising:
selecting an asperity rise angle;
determining a critical contact line density “Λ L ” value according to the formula:
Λ
L
=
-
P
γcos
(
θ
a
,
0
+
ω
-
90
°
)
where P is the predetermined pressure value, γ is the surface tension of the liquid, θ a,0 is the experimentally measured true advancing contact angle of the liquid on the asperity material in degrees, and ω is the asperity rise angle;
providing a substrate member; and
forming a multiplicity of projecting asperities on the substrate so that the surface has an actual contact line density equal to or greater than the critical contact line density.
14. The process of claim 13 , wherein the asperities are formed using photolithography.
15. The process of claim 13 , wherein the asperities are formed using wherein the asperities are formed using nanomachining, microstamping, microcontact printing, self-assembling metal colloid monolayers, atomic force microscopy nanomachining, sol-gel molding, self-assembled monolayer directed patterning, chemical etching, sol-gel stamping, printing with colloidal inks, or by disposing a layer of carbon nanotubes on the substrate.
16. The process of claim 13 , further comprising the step of selecting a geometrical shape for the asperities.
17. The process of claim 13 , further comprising the step of selecting an array pattern for the asperities.
18. The process of claim 13 , further comprising the steps of selecting at least one dimension for the asperities and determining at least one other dimension for the asperities using an equation for contact line density.
19. The process of claim 13 , further comprising the step of determining a critical asperity height value “Z c ” in meters according to the formula:
Z
c
=
d
(
1
-
cos
(
θ
a
,
0
+
ω
-
180
°
)
)
2
sin
(
θ
a
,
0
+
ω
-
180
°
)
where d is the distance in meters between adjacent asperities, θ a,0 is the true advancing contact angle of the liquid on the surface in degrees, and ω is the asperity rise angle in degrees.