Nanostructured friction enhancement using fabricated microstructure

• US 7,799,423 B2
• Filed: 11/16/2005
• Issued: 09/21/2010
• 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
• Primary Examiner(s): Tarazano; D. Lawrence
• Assistant Examiner(s): Matzek; Matthew D
• Application Number:
  US11/281,768
• Publication Number:
  US 20060202355A1
• Time in Patent Office: 1,770 Days
• Field of Search: 428/357, 428/364, 428/343
• US Class Current: 428/343
• 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_oR²(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 plurality of nano-fibers pack together into one or more clumps of mutually-supporting nano-fibers when not in contact with the contact surface, wherein the clumps break apart when the nano-fibers in the clumps come into contact with the contact surface;

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 biased at an angle θ

_o relative to the substrate when the nano-fibers are not clumped together,

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

_oR²(E/w)^1/2 with θ

_o in radians,

and 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.

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 μ

m and 1 μ

m.

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 plurality of nano-fibers is disposed on the substrate in a square-lattice configuration.

6. 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.

7. The fabricated microstructure of claim 6, wherein the ratio of the length L to the radius R is greater than 20 to 1.

8. 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 the portion of their length.

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

10. The fabricated microstructure of claim 1, wherein θ

_o is between 0.35 and 1.22 radians, and wherein the nano-fibers are disposed on the substrate with a linear spacing greater than 0.188(L/R)²(w/E)^1/2.

11. The fabricated microstructure of claim 1, wherein radius R is between 0.1 μ

m and 0.3 μ

m.

12. 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 plurality of nano-fibers pack together into one or more clumps of mutually-supporting nano-fibers when not in contact with the contact surface, wherein the clumps break apart when the nano-fibers in the clumps come into contact with the contact surface,

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 biased at an angle θ

_o relative to the substrate when the nano-fibers are not clumped together, wherein θ

_o is between 0.35 and 1.22 radians,

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

_oR²(E/w)^1/2 with θ

_o in radians, 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.

13. The fabricated microstructure of claim 12, wherein the nano-fibers are disposed on the substrate with a linear spacing greater than 0.188(L/R)²(w/E)^1/2.

14. The fabricated microstructure of claim 13, wherein, radius R is between 0.025 μ

m and 1 μ

m, and wherein the length L of the nano-fiber is greater than 5 microns.

15. The fabricated microstructure of claim 12, wherein the plurality of nano-fibers are disposed on the substrate in a square-lattice configuration.