Carbon nanotube-based sensor and method for continually sensing changes in a structure

• US 7,194,912 B2
• Filed: 07/13/2004
• Issued: 03/27/2007
• Est. Priority Date: 07/13/2004
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Oglesby, Donald M., Jordan, Jeffrey D., Ingram, JoAnne L., Watkins, Anthony Neal
• Primary Examiner(s): RAEVIS, ROBERT R
• Application Number:
  US10/890,843
• Publication Number:
  US 20060010996A1
• Time in Patent Office: 987 Days
• Field of Search: 737/67, 737/68, 737/74, 737/75, 737/79, 737/80, 374/100, 374/163, 374183-185
• US Class Current: 73/774
• CPC Class Codes: B82Y 15/00 Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: G01M 5/0041 by determining deflection or stress
• CPC Class Codes: G01M 5/0083 by measuring variation of impedance, e.g. resistance, capacitance, induction

Abstract

A sensor has a plurality of carbon nanotube (CNT)-based conductors operatively positioned on a substrate. The conductors are arranged side-by-side, such as in a substantially parallel relationship to one another. At least one pair of spaced-apart electrodes is coupled to opposing ends of the conductors. A portion of each of the conductors spanning between each pair of electrodes comprises a plurality of carbon nanotubes arranged end-to-end and substantially aligned along an axis. Because a direct correlation exists between resistance of a carbon nanotube and carbon nanotube strain, changes experienced by the portion of the structure to which the sensor is coupled induce a change in electrical properties of the conductors.

Claims

1. A sensor for detecting changes experienced by a structure, comprising:

a substrate adapted to be coupled to a portion of a structure;

a plurality of carbon nanotube (CNT)-based conductors operatively positioned on said substrate and arranged side-by-side to one another;

at least one pair of spaced-apart electrodes coupled to opposing ends of said plurality of CNT-based conductors with said plurality of CNT-based conductors electrically coupling each pair of said spaced-apart electrodes to one another;

a CNT attraction material deposited on said substrate, bonded to said plurality of CNT-based conductors, and spanning between said at least one pair of spaced-apart electrodes; and

a portion of each of said plurality of CNT-based conductors spanning between said at least one pair of spaced-apart electrodes comprising a plurality of carbon nanotubes arranged end-to-end and substantially aligned along an axis, wherein upon said substrate being coupled to the portion of the structure, changes experienced by the portion of the structure induce a change in electrical properties of said plurality of CNT-based conductors.

2. A sensor as in claim 1 wherein said substrate is flexible such that the strain experienced by the portion of the structure causes relative strain in said substrate.

3. A sensor as in claim 1 wherein said at least one pair of spaced-apart electrodes comprises one spaced-apart electrode pair positioned on said substrate, with said opposing ends of said plurality of CNT-based conductors being positioned on said spaced-apart electrode pair.

4. A sensor as in claim 1 wherein said at least one pair of spaced-apart electrodes comprises two pairs of spaced-apart electrodes positioned on the opposing ends of said plurality of CNT-based conductors.

5. A sensor as in claim 1 wherein said at least one pair of spaced-apart electrodes comprises:

a first pair of spaced-apart electrodes positioned on said substrate, with said opposing ends of said plurality of CNT-based conductors being positioned on said first pair of spaced-apart electrodes; and

a second pair of spaced-apart electrodes positioned on the opposing ends of each of said plurality of CNT-based conductors.

6. A sensor as in claim 1 wherein each of said plurality of carbon nanotubes is a single-wall carbon nanotube.

7. A sensor as in claim 1 wherein each of said at least one pair of spaced-apart electrodes comprises parallel electrodes.

8. A sensor as in claim 1 wherein the CNT-based conductors are arranged substantially parallel to one another.

9. A sensor as in claim 1 further comprising said CNT attraction material being deposited on a portion of said at least one pair of spaced apart electrodes.

10. A sensor for detecting changes experienced by a structure, comprising:

a flexible substrate adapted to be coupled to a portion of a structure;

a plurality of carbon nanotube (CNT)-based conductors and operatively positioned on said substrate and arranged side-by-side to one another; and

at least one air of spaced-apart electrodes positioned on and across opposing ends of said plurality of CNT-based conductors, thereby anchoring said ends to said flexible substrate, with said plurality of CNT-based conductors electrically coupling each pair of said spaced-apart electrodes to one another;

a portion of each of said plurality of CNT-based conductors spanning between said at least one pair of spaced-apart electrodes comprising a plurality of carbon nanotubes arranged end-to-end and substantially aligned along an axis, wherein upon said flexible substrate being coupled to the portion of the structure, changes experienced by the portion of the structure induce a change in electrical properties of said plurality of CNT-based conductors; and

wherein said at least one pair of spaced-apart electrodes comprises;

a first pair of spaced-apart electrodes positioned on said substrate; and

a second pair of spaced-apart electrodes positioned on and across the opposing ends of each of said plurality of CNT-based conductors.

11. A method of detecting changes experienced by a structure, said method comprising the steps of:

coupling at least one sensor to a portion of the structure, each said sensor comprising (i) a plurality of carbon nanotube (CNT)-based conductors arranged side-by-side to one another, and (ii) at least one pair of spaced-apart electrodes electrically coupled to opposing ends of said plurality of CNT-based conductors with a portion of each of said plurality of CNT-based conductors spanning between each pair of said spaced-apart electrodes comprising a plurality of carbon nanotubes arranged end-to-end and substantially aligned along an axis;

monitoring electrical properties of said plurality of CNT-based conductors when the portion of the structure is experiencing baseline levels of at least one of the parameters of strain, temperature, and pressure to establish a baseline response; and

continually monitoring the electrical properties over time to identify any change from the baseline response, wherein a change in the electrical properties of said plurality of CNT-based conductors is indicative of changes in the at least one parameter experienced by the portion of the structure.

12. A method according to claim 11 wherein said step of coupling comprises the step of embedding said at least one sensor in the structure.

13. A method according to claim 11 wherein said step of coupling comprises the step of coupling said at least one sensor to a surface of the structure.

14. A method according to claim 11 wherein said at least one sensor comprises a plurality of sensors, and wherein said step of coupling comprises the steps of:

embedding a portion of said plurality of sensors in the structure; and

coupling a remainder of said plurality of sensors to a surface of the structure.

15. A method according to claim 11 wherein said at least one sensor comprises a plurality of sensors, and wherein said step of coupling comprises the step of arranging said plurality of sensors such that the axis associated with each one of said plurality of sensors is at an orientation unique to the axis of each of the other of said plurality of sensors.

16. A method according to claim 11 wherein each of said plurality of carbon nanotubes is a single-wall carbon nanotube.

17. A method of detecting changes experienced by a structure, said method comprising the steps of:

coupling at least one sensor to a portion of the structure, each said sensor comprising (i) a substrate adapted to be coupled to a portion of a structure, (ii) a plurality of carbon nanotube (CNT)- based conductors operatively positioned on said substrate and arranged side-by-side to one another, and (iii) at least one pair of spaced-apart electrodes electrically coupled to opposing ends of said plurality of CNT-based conductors with a portion of each of said plurality of CNT-based conductors spanning between each pair of said spaced-apart electrodes comprising a plurality of carbon nanotubes arranged end-to-end and substantially aligned along an axis;

monitoring electrical properties of said plurality of CNT-based conductors when the portion of the structure is experiencing baseline levels of at least one of the parameters of strain, temperature, and pressure to establish a baseline response; and

continually monitoring the electrical properties over time to identify any change in the electrical properties from the baseline response, wherein a change in the electrical properties of said plurality of CNT-based conductors is indicative of changes in the at least one parameter experienced by the portion of the structure.

18. A method according to claim 17 wherein said step of coupling comprises the step of embedding said at least one sensor in the structure.

19. A method according to claim 17 wherein said step of coupling comprises the step of coupling said at least one sensor to a surface of the structure.

20. A method according to claim 17 wherein said at least one sensor comprises a plurality of sensors, and wherein said step of coupling comprises the steps of:

embedding a portion of said plurality of sensors in the structure; and

coupling a remainder of said plurality of sensors to a surface of the structure.

21. A method according to claim 17 wherein said at least one sensor comprises a plurality of sensors, and wherein said step of coupling comprises the step of arranging said plurality of sensors such that the axis of sensitivity associated with each one of said plurality of sensors is at an orientation unique to the axis of sensitivity of each of the other of said plurality of sensors.

22. A method according to claim 17 wherein said substrate is flexible such that strain experienced by the portion of the structure causes relative strain in said substrate.

23. A method according to claim 17 wherein each of said plurality of carbon nanotubes is a single-wall carbon nanotube.