Anisotropic nanotube fabric layers and films and methods of forming same
View Patent ↗Methods for forming anisotropic nanotube fabrics are disclosed. In one aspect, a nanotube application solution is rendered into a nematic state prior to its application over a substrate. In another aspect, a pump and narrow nozzle assembly are employed to realize a flow induced alignment of a plurality of individual nanotube elements as they are deposited onto a substrate element. In another aspect, nanotube adhesion promoter materials are used to form a patterned nanotube application layer, providing narrow channels over which nanotube elements will self align during an application process. Specific dip coating processes which are well suited for aiding in the creation of anisotropic nanotube fabrics are also disclosed.
1. A method of forming an anisotropic nanotube fabric layer over a substrate element, which comprises:
forming a layer of a nanotube adhesion averter material over said substrate element;
depositing a photoresist mask over said layer of nanotube adhesion averter material such that at least one region of said layer of nanotube adhesion averter material is covered by said photoresist mask and at least one region of said layer of nanotube adhesion averter material is not covered by said photoresist mask;
etching away the at least one region of said layer of nanotube adhesion averter material not covered by said photoresist mask to form at least one gap within said layer of nanotube adhesion averter material;
backfilling said at least one gap within said layer of nanotube adhesion averter material with a nanotube adhesion promoter material to foam at least one nanotube adhesion structure;
stripping away said photoresist mask to leave a patterned application surface comprising the remaining nanotube adhesion averter material and the at least one nanotube adhesion structure;
depositing a layer of nanotube elements over said patterned application surface; and
washing said layer of nanotube elements such that substantially all nanotube elements not in physical contact with said at least one nanotube adhesion structure are removed.
2. The method of claim 1 wherein said layer of nanotube adhesion averter material is a self assembled monolayer.
3. The method of claim 1 wherein said layer of nanotube adhesion averter material is comprised of bis(trimethoxy silyl methyl)benzene.
4. The method of claim 1 wherein said photoresist mask is deposited in a predetermined pattern over said layer of nanotube adhesion averter material.
5. The method of claim 1 wherein the step of etching is performed via a reactive plasma etch process.
6. The method of claim 1 wherein said nanotube adhesion promoter material is aminopropyltriethoxysilane.
7. The method of claim 1 wherein said nanotube adhesion structures are narrow with respect to said substrate element.
8. The method of claim 7 wherein said nanotube adhesion structures range in width from about 1 nm to about 10 nm.
9. The method of claim 1 wherein said patterned application surface is substantially planar.
10. The method of claim 1 wherein said layer of nanotube elements is applied via a dip coating process.
11. The method of claim 10 wherein said dip coating process uses an air-liquid interface.
12. The method of claim 10 wherein said dip coating process uses a liquid-liquid interface.
13. The method of claim 10 wherein said dip coating process uses a nanotube application solution comprising nanotube elements.
14. The method of claim 13 wherein the concentration of the nanotube elements in said nanotube application solution is optimized to promote the formation of an anisotropic nanotube fabric layer over said at least one nanotube adhesion structure.
15. The method of claim 13 wherein said nanotube application solution is rendered into a nematic state to promote the formation of an anisotropic nanotube fabric layer over said at least one nanotube adhesion structure.
16. The method of claim 13 , wherein the nematic state comprises a concentration of the nanotube elements in said nanotube application solution greater than 0.05 g/ml.
17. The method of claim 10 wherein the speed of the dip coating process is optimized to form an anisotropic nanotube fabric layer over said at least one nanotube adhesion structure.
18. The method of claim 17 , wherein the speed of the dip coating process is in the range of about 5.4 microns/second to about 54 microns/second.
19. The method of claim 10 wherein the ambient temperature during the dip coating process is optimized to form an anisotropic nanotube fabric layer over said at least one nanotube adhesion structure.
20. The method of claim 19 wherein the ambient temperature comprises room temperature.
21. The method of claim 1 wherein said layer of nanotube elements is applied via a spin coating process.
22. The method of claim 1 wherein said layer of nanotube elements is applied via a spray coating process.
23. The method of claim 1 wherein the substrate element is selected from the group consisting of a silicon wafer, semiconductors, plastic, glass, a flexible polymer, a flexible substrate, and a transparent substrate.
24. The method of claim 1 , wherein the thickness of the nanotube fabric layer comprises about 50 nm to about 200 nm.