Self-cleaning superhydrophobic surface

• US 8,580,371 B2
• Filed: 01/18/2010
• Issued: 11/12/2013
• Est. Priority Date: 01/06/2005
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Strauss, Dennis R.
• Primary Examiner(s): Chen, Vivian
• Application Number:
  US12/689,035
• Publication Number:
  US 20100116669A1
• Time in Patent Office: 1,394 Days
• Field of Search: None
• US Class Current: 428/142
• CPC Class Codes: B05D 5/086 having an anchoring layer
• CPC Class Codes: B05D 7/14 to metal, e.g. car bodies involving a chemical reaction between the metal and the coating C23
• CPC Class Codes: B64C 21/10 using other surface properties, e.g. roughness
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: Y02T 50/10 Drag reduction
• CPC Class Codes: Y10T 428/24355 Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
• CPC Class Codes: Y10T 428/24364 with transparent or protective coating
• CPC Class Codes: Y10T 428/24413 Metal or metal compound
• CPC Class Codes: Y10T 428/265 1 mil or less
• CPC Class Codes: Y10T 428/269 including synthetic resin or polymer layer or component
• CPC Class Codes: Y10T 428/2913 Rod, strand, filament or fiber
• CPC Class Codes: Y10T 428/2933 Coated or with bond, impregnation or core
• CPC Class Codes: Y10T 428/2935 Discontinuous or tubular or cellular core
• CPC Class Codes: Y10T 428/2938 Coating on discrete and individual rods, strands or filaments
• CPC Class Codes: Y10T 428/2975 Tubular or cellular
• CPC Class Codes: Y10T 428/3154 Of fluorinated addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31544 Addition polymer is perhalogenated
• CPC Class Codes: Y10T 428/31678 Of metal

Abstract

A superhydrophobic structure that may have a titanium substrate and nanoporous titanium oxide layer grown on the titanium substrate by anodization. The titanium oxide layer may have a plurality of nano-tube structures that create a microscopically rough surface on the titanium substrate. A hydrophobic coating may be deposited over the titanium oxide layer to create a superhydrophobic surface on the titanium substrate. The titanium oxide layer may provide a photocatalytic reaction with oxygen in surrounding air to oxidize organic contaminants on the superhydrophobic surface.

Claims

1. A superhydrophobic aircraft structure comprising:

a titanium substrate forming a functional surface portion of the aircraft structure;

a nanoporous titanium oxide layer grown on the titanium substrate by anodization, the titanium oxide layer comprising a plurality of nano-tube structures that create a microscopically rough surface on the titanium substrate; and

a conformal hydrophobic coating deposited over the titanium oxide layer to create a superhydrophobic surface on the titanium substrate, whereby the titanium oxide layer provides a photocatalytic reaction with oxygen in surrounding air to oxidize organic contaminants on the superhydrophobic surface; and

wherein the hydrophobic coating that is deposited over the titanium oxide layer includes a thickness of approximately 1 to 10 nanometers.

2. The aircraft structure of claim 1, wherein the titanium oxide layer is grown by coating the titanium substrate with a hydrofluoric acid electrolyte and applying a DC voltage across the titanium substrate such that current flows through the titanium substrate and the hydrofluoric acid electrolyte to grow the titanium oxide layer.

3. The aircraft structure of claim 2, wherein the voltage applied comprises a DC voltage between 1 and 20 volts.

4. The aircraft structure of claim 2, wherein the titanium oxide layer is grown by polishing the surface of the titanium substrate prior to applying the coating of hydrofluoric acid.

5. The aircraft structure of claim 1, wherein the hydrophobic coating comprises one of polytetrafluoroethylene, a fluorocarbon and fluorinated alkylsilane.

6. A superhydrophobic aircraft structure comprising:

a titanium substrate forming a functional surface portion of the aircraft structure;

a nanoporous titanium oxide layer grown on the titanium substrate by coating the titanium substrate with a hydrofluoric acid electrolyte and applying a voltage of at least about 1 volt DC to no more than about 20 volts DC across the titanium substrate such that current flows through the titanium substrate and the hydrofluoric acid electrolyte to grow the titanium oxide layer, the titanium oxide layer comprising a plurality of nano-tube structures that create a microscopically rough surface on the titanium substrate, and the nano-tube structures having diameters of approximately 16 nanometers; and

a conformal hydrophobic coating deposited over the titanium oxide layer to create a superhydrophobic surface on the titanium substrate.

7. The superhydrophobic aircraft structure of claim 6, wherein the titanium oxide layer provides a photocatalytic reaction with oxygen in surrounding air to oxidize organic contaminants on the superhydrophobic surface.

8. The superhydrophobic aircraft structure of claim 6, wherein the hydrophobic coating is deposited over the titanium oxide layer in a coating layer approximately no greater than about 10 nanometers in thickness.

9. The superhydrophobic aircraft structure of claim 6, wherein the hydrophobic coating is deposited over the titanium oxide layer in a coating layer having a thickness of at least about 1 nanometer in thickness.

10. The superhydrophobic aircraft structure of claim 9, wherein the coating layer has a thickness of at least about 1 nanometer in thickness, and no more than about 10 nanometers in thickness.

11. The superhydrophobic aircraft structure of claim 6, wherein the hydrophobic coating comprises one of polytetrafluoroethylene, a fluorocarbon and fluorinated alkylsilane.

12. The superhydrophobic aircraft structure of claim 6, wherein the titanium oxide layer comprises a polished surface resulting from polishing of the titanium substrate prior to applying the coating of hydrofluoric acid.

13. A superhydrophobic aircraft structure comprising:

a titanium substrate forming a functional surface portion of the aircraft structure;

a nanoporous titanium oxide layer grown on the titanium substrate by coating the titanium substrate with a hydrofluoric acid electrolyte and applying an electrical signal of at least about 1 volt DC to no more than about 20 volts DC across the titanium substrate to grow the titanium oxide layer;

the titanium oxide layer comprising a plurality of nano-tube structures each having a diameter of about 16 nanometers that create a microscopically rough surface on the titanium substrate; and

a conformal hydrophobic coating having a thickness of between about 1-10 nanometers deposited over the titanium oxide layer to create a superhydrophobic surface on the titanium substrate, the hydrophobic coating being comprised of at least one of;

a polytetrafluoroethylene;

a fluorocarbon; and

a fluorinated alkylsilane.

14. The superhydrophobic aircraft structure of claim 13, wherein the wherein the titanium oxide layer provides a photocatalytic reaction with oxygen in surrounding air to oxidize organic contaminants on the superhydrophobic surface.

15. The superhydrophobic aircraft structure of claim 13, wherein the electrical signal comprises a DC voltage that is applied across the titanium substrate.

16. The superhydrophobic aircraft structure of claim 13, wherein the electrical signal comprises a DC voltage signal.