Method for patterning large scale nano-fibrous surfaces using capillography

• US 20060088848A1
• Filed: 05/05/2005
• Published: 04/27/2006
• Est. Priority Date: 05/05/2004
• Status: Active Grant

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Gharib, Morteza, Zhou, Jijie, Noca, Flavio, Sansom, Elijah B.
• Granted Patent: US 7,491,628 B2
• Time in Patent Office: Days
• US Class Current: 435/6
• CPC Class Codes: B82B 3/00 Manufacture or treatment of nanostructures by manipulation of individual atoms or molecules, or limited collections of atoms or molecules as discrete units
• 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: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: H01J 2201/30469 Carbon nanotubes (CNTs)
• CPC Class Codes: H01J 2329/00 Electron emission display panels, e.g. field emission display panels
• CPC Class Codes: H01J 9/025 of field emission cathodes
• CPC Class Codes: Y10S 977/742 Carbon nanotubes, CNTs

Abstract

A method of assembling large numbers of nanoscale structures in pre-determined ways using fluids or capillary lithography to control the patterning and arrangement of the individual nanoscale objects and nanostructures formed in accordance with the inventive method are provided. In summary, the current method uses the controlled dispersion and evaporation of fluids to form controlled patterns of nanoscale objects or features anchored on a substrate, such as nanoscale fibers like carbon nanotubes.

Claims

1. A method of controllably patterning a plurality of nanofeatures comprising:

providing a plurality of nanofeatures anchored on at least one end to a substrate;

disposing a quantity of a fluid onto at least a portion of the plurality of nanofeatures, wherein the fluid has a surface tension sufficiently low such that the fluid penetrates between the plurality of nanofeatures;

dissipating the fluid from the plurality of nanofeatures at a specified rate such that the nanofeatures are reoriented by the dissipating fluid to form a plurality of repeating nanostructures from the reoriented nanofeatures.

2. The method of claim 1, wherein the step of providing the nanofeatures includes growing said nanofeatures using a chemical vapor deposition technique.

3. The method of claim 1, wherein the nanofeatures are nanotubes.

4. The method of claim 3, wherein the nanotubes are made of carbon atoms.

5. The method of claim 1, wherein fluid is a high volatile liquid such that the nanofeatures are reoriented to form trench structures on the surface of the substrate during dissipation of the fluid.

6. The method of claim 5, wherein the fluid is an organic solvent.

7. The method of claim 6, wherein the fluid is one of either methanol or acetone.

8. The method of claim 1, wherein the fluid is a curable polymer material, and wherein the method further includes the step of crosslinking the polymer prior to dissipation of the fluid such that the removal of nanofeatures from the substrate during dissipation is substantially eliminated.

9. The method of claim 8, wherein the polymer is one of either a PDMS or an RTV.

10. The method of claim 8, wherein the polymer is disposed on the substrate in a layer having a height no greater than the height of the nanofeatures.

11. The method of claim 1, wherein the substrate is substantially curved.

12. The method of claim 1, wherein the substrate is substantially flexible.

13. The method of claim 12, wherein prior to the step of disposing the fluid to the nanofeatures the method further comprises the steps of:

applying a flexible adhesive material to the top surface of the nanofeatures;

removing the adhesive material such that the nanofeatures are removed from the substrate but remain attached to the adhesive material such that the adhesive material becomes the substrate for the remaining steps of the process.

14. The method of claim 1, wherein the nanostructures formed are nest structures.

15. The method of claim 14, wherein the step of dissipating the fluid further comprises controlling the rate at which the fluid dissipates from the substrate such that adjustment can be made to one aspect of the nanostructures selected from the density of nanostructures, the size of the nanostructures, or the shape of the nanostructures.

16. The method of claim 15, wherein decreasing rate of dissipation at the surface of the nanofeatures increases the density of nanostructures formed.

17. The method of claim 15, wherein decreasing rate of dissipation at the surface of the nanofeatures increases the average size of the nanostructures formed.

18. The method of claim 15, wherein decreasing rate of dissipation at the surface of the nanofeatures increases the number of fully formed nanostructures.

19. The method of claim 15, wherein the step of controlling the rate of dissipation of the fluid comprises controlling the average humidity at the surface of the nanofeatures.

20. The method of claim 15, wherein the step of controlling the rate of dissipation of the fluid comprises controlling the temperature at the surface of the nanofeatures.

21. The method of claim 15, wherein the step of controlling the rate of dissipation of the fluid comprises controlling the flow of air over the surface of the nanofeatures.

22. The method of claim 15, wherein the average size of the nanostructures can be adjusted between about 1 μ

m and 1000 μ

m.

23. The method of claim 14, wherein further comprising selecting the surface tension of the fluid to be disposed on the nanofeatures such that nanostructures of a specified size are formed.

24. The method of claim 23, wherein decreasing surface tension of the fluid increases the size of the nanostructures formed.

25. The method of claim 24, wherein the average size of the nanostructures can be adjusted between about 1 μ

m and 1000 μ

m.

26. The method of claim 23, wherein the fluid is a low molecular weight PDMS.

27. The method of claim 1, wherein the fluid is chosen such that no evaporation of the fluid occurs during dissipation.

28. The method of claim 27, wherein the fluid is a high molecular weight PDMS.

29. The method of claim 1, wherein fluid comprises a suspension of microparticles.

30. The method of claim 29, wherein the suspension comprises a mixture of polystyrene microspheres in water.

31. The method of claim 1, wherein the nanofeatures have a height of less than a micron such that sub-micron nanostructures are formed during dissipation.

32. The method of claim 1, wherein the substrate is oriented in such a manner that the gravitational pull on the individual nanofeatures is in a direction other than normal to the top surface of the substrate.

33. A material having controllably patterned nanostructures made in accordance with the method described in claim 1 disposed thereon.

34. The material of claim 33, wherein the material is designed for use as an emitter material for field emission displays, a superhydrophobic hull material for full-scale hydrodynamic vehicles, a thermal radiator material for computer chipsets, and a micro-template material for biological tissue growth.