STRAIN SENSORS AND METHODS OF MANUFACTURE AND USE

• US 20160153762A1
• Filed: 10/02/2014
• Published: 06/02/2016
• Est. Priority Date: 10/02/2013
• Status: Active Grant

• Current Assignee: Florida State University Research Foundation, Inc. (State University System of Florida)
• Original Assignee: Florida State University Research Foundation, Inc. (State University System of Florida)
• Inventors: Li, Shu, Liang, Zhiyong
• Granted Patent: US 9,618,403 B2
• Time in Patent Office: Days
• CPC Class Codes: G01B 7/18 using change in resistance
• CPC Class Codes: G01L 1/00 Measuring force or stress, in general measuring force due to impact G01L5/00
• CPC Class Codes: G01L 1/18 using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
• CPC Class Codes: G01L 1/22 using resistance strain gauges

Abstract

Strain sensors are provided that include a flexible substrate, a sheet affixed to the flexible substrate, and two or more microelectrodes printed at spaced locations onto either the sheet or the flexible substrate, wherein the sheet includes a carbon nanotube network, the sheet having a top side and an opposing second side. The two or more microelectrodes are printed at spaced locations onto the top side of the sheet or onto a side of the flexible substrate facing the second side of the sheet. Methods are provided for fabricating a strain sensor wherein the sheet is arranged between the printed microelectrodes and the flexible substrate or wherein the second side of the sheet is arranged atop or across the printed microelectrodes. Methods are also provided for measuring strain in a structure via the strain sensors affixed or integrated therein.

Claims

1. A strain sensor comprising:

a flexible substrate;

a sheet which comprises a carbon nanotube network affixed to the flexible substrate, the sheet having a top side and an opposing second side; and

two or more microelectrodes printed at spaced locations onto;

(i) the top side of the sheet, such that the sheet is arranged between the printed microelectrodes and the flexible substrate;

or

(ii) a side of the flexible substrate facing the second side of the sheet, such that the printed microelectrodes are between the second side of the sheet and the flexible substrate.

2. The strain sensor of claim 1, wherein the sheet is affixed to the substrate with an epoxy resin between the second side of the sheet and the flexible substrate.

3. The strain sensor of claim 1, wherein the substrate comprises a polyimide, polyethylene terephthalate, polybutylene terephthalate, polycarbonate, or a combination thereof.

4. The strain sensor of claim 1, wherein the carbon nanotube network comprises carbon nanotubes that are substantially aligned with one another.

5. The strain sensor of claim 1, wherein the microelectrodes are aerosol jet printed microelectrodes.

6. The strain sensor of claim 1, wherein the microelectrodes are printed at spaced locations onto the top side of the sheet, such that the sheet is between the printed microelectrodes and the flexible substrate.

7. The strain sensor of claim 6, wherein the strain sensor yields a positive gauge factor from about 6 to about 20.

8. The strain sensor of claim 1, wherein the microelectrodes are printed at spaced locations onto the side of the flexible substrate facing the second side of the sheet, such that the printed microelectrodes are between the second side of the sheet and the flexible substrate.

9. The strain sensor of claim 8, wherein the strain sensor yields a negative gauge factor from about 15 to about 40.

10. The strain sensor of claim 1, wherein the spaced locations comprises locations which are spaced about 30 μ

m to about 1 cm from each other.

11. The strain sensor of claim 1, wherein the sheet is a buckypaper.

18. A method for measuring strain in a structure comprising:

subjecting the structure, which has at least one strain sensor according to claim 1 affixed thereon or integrated therein, to external forces effective to induce strain in the structure;

detecting a change in electrical resistance of the strain sensor, wherein the change is generated and transferred as an output voltage signal; and

determining, from the output voltage signal, the strain in the structure caused by the external forces.

19. The method of claim 18, wherein the microelectrodes are printed at spaced locations onto the top side of the sheet, such that the sheet is between the printed microelectrodes and the flexible substrate.

20. The method of claim 19, wherein the strain sensor yields a positive gauge factor of about 6 to about 20.

21. The method of claim 18, wherein the microelectrodes are printed at spaced locations onto the side of the flexible substrate facing the opposing second side of the sheet, such that the printed microelectrodes are between the opposing second side of the sheet and the flexible substrate.

22. The method of claim 21, wherein the strain sensor yields a negative gauge factor of about 15 to about 40.

12. A method for making a strain sensor, the method comprising:

bonding a sheet comprising a carbon nanotube network to a flexible substrate, the sheet having a top side and an opposing second side; and

printing two or more microelectrodes at spaced locations onto the top side of the sheet,

wherein the sheet is arranged between the printed microelectrodes and the flexible substrate.

13. The method of claim 12, wherein the printing electrodes comprises aerosel jet printing of the electrodes.

14. The method of claim 12, wherein the spaced locations are spaced about 30 μ

m to about 1 cm from each other.

15. A method for making a strain sensor, the method comprising:

printing two or more microelectrodes at spaced locations onto a flexible substrate; and

bonding a sheet comprising a carbon nanotube network to the flexible substrate, the sheet having a top side and an opposing second side, wherein the second side of the sheet is arranged atop or across the printed microelectrodes.

16. The method of claim 15, wherein the printing electrodes comprises aerosel jet printing of the electrodes.

17. The method of claim 15, wherein the spaced locations are spaced about 30 μ

m to about 1 cm from each other.