Fluid handling device with directionally-biased wetting surface
View Patent ↗A fluid handling device with an anisotropic wetting surface including a substrate with a multiplicity of asymmetric substantially uniformly shaped asperities thereon. Each asperity has a first asperity rise angle and a second asperity rise angle relative to the substrate. The asperities are structured to present a desired retentive force ratio (f 1 /f 2 ) greater or less than unity caused by asymmetry between the first asperity rise angle and the second asperity rise angle according to the formula: f 3 /f 2 =sin(ω 3 +½Δθ 0 )/sin(ω 2 +½Δθ 0 ).
1. A fluid handling device having an anisotropic wetting surface portion, the anisotropic wetting surface portion comprising:
a substrate with a multiplicity of asymmetric substantially uniformly shaped microscale or nanoscale asperities thereon, each asperity defining a first asperity rise angle and a second opposing asperity rise angle relative to the substrate, the asperities being structured to present a retentive force ratio (f 3 /f 2 ) greater or less than unity when the retentive force ratio (f 3 /f 2 ) is determined according to the formula:
f 3 /f 2 =sin(ω 3 +½Δθ 0 )/sin(ω 2 +½Δθ 0 )
where ω 2 is the first asperity rise angle in degrees, ω 3 is the second asperity rise angle in degrees, and Δθ 0 =(θ a,0 −θ r,0 ) where θ a,0 is a true advancing contact angle of a fluid in contact with the surface in degrees, and θ r,0 is a true receding contact angle of the fluid on the surface in degrees.
2. The fluid handling device of claim 1 , wherein the asperities are projections.
3. The fluid handling device of claim 2 , wherein the asperities are polyhedrally shaped.
4. The fluid handling device of claim 2 , wherein each asperity has a generally square transverse cross-section.
5. The fluid handling device of claim 2 , wherein the asperities are cylindrical, cylindroidal, conical or frusto-conical in shape.
6. The fluid handling device of claim 1 , wherein the asperities are cavities formed in the substrate.
7. The fluid handling device of claim 1 , wherein the asperities are positioned in a substantially uniform array.
8. The fluid handling device of claim 7 , wherein the asperities are positioned in a rectangular array.
9. The fluid handling device of claim 1 , wherein the fluid handling device is a microfluidic device.
10. The fluid handling device of claim 1 , wherein the fluid handling device is a fuel cell component.
11. A method of providing an anisotropic wetting surface on a fluid handling device, the method comprising:
providing a fluid handling device presenting a surface; and
disposing a multiplicity of substantially uniformly shaped microscale or nanoscale asperities on the surface of the fluid handling device to form the anisotropic wetting surface, each asperity having a first asperity rise angle and a second asperity rise angle relative to the surface, wherein the asperities are structured and disposed so as to present a retentive force ratio (f 3 /f 2 ) greater or less than unity when the retentive force ratio (f 3 /f 2 ) is determined according to the formula:
f 3 /f 2 =sin(ω 3 +½Δθ 0 )/sin(ω 2 +½Δθ 0 )
where ω 2 is the first asperity rise angle in degrees, ω 3 is the second asperity rise angle in degrees, and Δθ 0 =(θ a,0 −θ r,0 ) where θ a,0 is a true advancing contact angle of a fluid in contact with the surface in degrees, and θ r,0 is a true receding contact angle of the fluid on the surface in degrees.
12. The process of claim 11 , wherein the asperities are disposed using a photolithography process.
13. The process of claim 11 , wherein the asperities are disposed using 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 parallel carbon nanotubes on the substrate.
14. A fluid handling device comprising an anisotropic wetting surface with a multiplicity of asymmetric substantially uniformly shaped asperities thereon, each asperity defining a first asperity rise angle and a second opposing asperity rise angle relative to the substrate, the asperities being structured to present a retentive force ratio (f 3 /f 2 ) greater or less than unity when the retentive force ratio (f 3 /f 2 ) is determined according to the formula:
f 3 /f 2 =sin(ω 3 +½Δθ 0 )/sin(ω 2 +½Δθ 0 )
where ω 2 is the first asperity rise angle in degrees, ω 3 is the second asperity rise angle in degrees, and Δθ 0 =(θ a,0 −θ r,0 ) where θ a,0 is a true advancing contact angle of a fluid in contact with the surface in degrees, and θ r,0 is a true receding contact angle of the fluid on the surface in degrees.
15. The fluid handling device of claim 14 , wherein the fluid handling device is tubular in shape.
16. The fluid handling device of claim 14 , wherein the fluid handling device is a valve.
17. The fluid handling device of claim 14 , wherein the fluid handling device is a microfluidic device.
18. The fluid handling device of claim 1 , wherein the fluid handling device is a fuel cell component.
19. A method of cleaning a fluid handling device, comprising:
providing a fluid handling device presenting an anisotropic wetting surface, the anisotropic wetting surface comprising a substrate with a multiplicity of asymmetric substantially uniformly shaped asperities thereon, each asperity defining a first asperity rise angle and a second opposing asperity rise angle relative to the substrate, the asperities being structured to present a retentive force ratio (f 3 /f 2 ) greater or less than unity when the retentive force ratio (f 3 /f 2 ) is determined according to the formula:
f 3 /f 2 =sin(ω 3 +½Δθ 0 )/sin(ω 2 +½Δθ 0 )
where ω 2 is the first asperity rise angle in degrees, ω 3 is the second asperity rise angle in degrees, and Δθ 0 =(θ a,0 −θ r,0 ) where θ a,0 is a true advancing contact angle of a fluid in contact with the anisotropic wetting surface in degrees, and θ r,0 is a true receding contact angle of the fluid on the anisotropic wetting surface in degrees; and
contacting the anisotropic wetting surface with the fluid.
20. The method of claim 19 , further comprising imparting a force to the fluid handling device or the fluid to cause the fluid to move on the anisotropic wetting surface.