Nanostructured friction enhancement using fabricated microstructure

• US 20060202355A1
• Filed: 11/16/2005
• Published: 09/14/2006
• Est. Priority Date: 11/19/2004
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Groff, Richard, Fearing, Ronald S., Majidi, Carmel
• Granted Patent: US 7,799,423 B2
• Time in Patent Office: Days
• US Class Current: 257/783
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C09J 2301/31 the adhesive effect being based on a Gecko structure
• CPC Class Codes: C09J 7/00 Adhesives in the form of films or foils
• CPC Class Codes: C09J 7/10 without carriers
• CPC Class Codes: Y10T 428/23957 Particular shape or structure of pile
• CPC Class Codes: Y10T 428/28 Web or sheet containing structurally defined element or component and having an adhesive outermost layer
• CPC Class Codes: Y10T 428/29 Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
• CPC Class Codes: Y10T 428/2913 Rod, strand, filament or fiber

Abstract

Described herein are fabricated microstructures to adhere in shear to a contact surface. A fabricated microstructure comprises a substrate and a plurality of nano-fibers attached to the substrate. The nano-fibers have an elasticity modulus E, an interfacial energy per unit length of contact w, a length L, a radius R, and are oriented at an angle θ_o relative to the substrate. The length L of the nano-fibers is greater than 0.627θ_o R²(E/w)^1/2 with θ_o in radians. Also described herein is a method of forming a fabricated microstructure to adhere in shear to a contact surface and a method of adhering in shear a fabricated microstructure to a contact surface.

Claims

1. A fabricated microstructure to adhere in shear to a contact surface, the fabricated microstructure comprising:

a substrate; and

a plurality of nano-fibers attached to the substrate,

wherein the nano-fibers have an elasticity modulus E, an interfacial energy per unit length of contact w, a length L, a radius R, and are oriented at an angle θ

_o relative to the substrate, and

wherein the length L of the nano-fibers is greater than 0.627θ

_o R²(E/w)^1/2 with θ

_o in radians.

2. The fabricated microstructure of claim 1, wherein the nano-fibers are disposed on the substrate with a linear spacing greater than 0.188(L/R)²(w/E)^1/2.

3. The fabricated microstructure of claim 2, wherein the angle θ

_o is between 0.35 and 1.22 radians, radius R is between 0.025 um and 1 um.

4. The fabricated microstructure of claim 3, wherein the length L of the nano-fiber is greater than 5 microns.

5. The fabricated microstructure of claim 1, wherein the nano-fibers are disposed on the substrate with a linear spacing greater than 0.445(L/W)²(w/E)^1/2.

6. The fabricated microstructure of claim 1, wherein the plurality of nano-fibers are disposed on the substrate in a square-lattice configuration.

7. The fabricated microstructure of claim 1, wherein a ratio of the length L to the radius R is equal to a ratio of shear force to normal pull-off force.

8. The fabricated microstructure of claim 7, wherein the ratio of the length L to the radius R is greater than 20 to 1.

9. The fabricated microstructure of claim 1, wherein each nano-fiber includes a first end attached to the substrate and a free second end opposite the first end, and wherein a portion of the length of the nano-fibers contact the contact surface.

10. The fabricated microstructure of claim 1, wherein, when the nano-fibers adhere in shear to the contact surface, the nano-fibers bend and adhere along a portion of their length.

11. The fabricated microstructure of claim 1, wherein the nano-fibers include T-shaped ends that contact the contact surface to resist peeling.

12. The fabricated microstructure of claim 1, wherein the nano-fibers are cylindrical.

13. A method of forming a fabricated microstructure to adhere in shear to a contact surface, comprising:

forming a substrate; and

forming a plurality of nano-fibers attached to the substrate,

wherein the nano-fibers have an elasticity modulus E, an interfacial energy per unit length of contact w, a length L, a radius R, and are oriented at an angle θ

_o relative to the substrate, and

wherein the length L of the nano-fibers is greater than 0.627θ

_o R²(E/w)^1/2 with θ

_o in radians.

14. The method of claim 13, wherein the nano-fibers are disposed on the substrate with a linear spacing greater than 0.188(L/R)²(w/E)^1/2.

15. The method of claim 14, wherein the angle θ

_o is between 20 and 70 degrees, radius R is between 0.025 um and 1 um.

16. The method of claim 15, wherein the length L of the nano-fiber is greater than 5 microns.

17. The method of claim 13, wherein the nano-fibers are disposed on the substrate with a linear spacing greater than 0.445(L/W)²(w/E)^1/2.

18. The method of claim 13, wherein the plurality of nano-fibers are disposed on the substrate in a square-lattice configuration.

19. The method of claim 13, wherein a ratio of the length L to the radius R is equal to a ratio of shear force to normal pull-off force.

20. A method of adhering in shear a fabricated microstructure to a contact surface, comprising:

obtaining a a substrate having a plurality of nano-fibers attached to the substrate, wherein the nano-fibers have an elasticity modulus E, an interfacial energy per unit length of contact w, a length L, a radius R, and are oriented at an angle θ

_o relative to the substrate, and wherein the length L of the nano-fibers is greater than 0.627θ

_o R²(E/w)^1/2 with θ

_o in radians; and

placing the substrate having the plurality of nano-fibers on the contact surface.