Strain Sensor

• US 20130118267A1
• Filed: 11/09/2012
• Published: 05/16/2013
• Est. Priority Date: 11/14/2011
• Status: Active Grant

• Current Assignee: National University Corporation Shizuoka University, Yamaha Corporation
• Original Assignee: National University Corporation Shizuoka University, Yamaha Corporation
• Inventors: Suzuki, Katsunori, Sakakibara, Shingo, Yataka, Koji, Terada, Yoshiki, Inoue, Yoku, Okumiya, Yasuro
• Granted Patent: US 9,212,895 B2
• Time in Patent Office: Days
• US Class Current: 73/774
• CPC Class Codes: G01B 7/18 using change in resistance

Abstract

A strain sensor includes a flexible substrate, a CNT film made of a plurality of CNT fibers aligned in an orientation direction, a pair of electrodes, and a protective coat. The electrodes are formed at the opposite ends of the CNT film in a perpendicular direction to the orientation direction of the CNT fibers. The protective coat protecting the CNT film is made of a resin, a water-based emulsion, or an oil-based emulsion. The protective coat is placed in contact with at least part of the CTN fibers on the surface of the CNT film. The strain sensor including the protective coat is able to prevent damage/breakage of the CNT film and to prevent foreign matters from entering into gaps between CNT fibers, thus improving durability in maintaining adequate sensing functionality.

Claims

1. A strain sensor comprising:

a substrate having flexibility;

a CNT film which is made of a plurality of CNT fibers aligned in an orientation direction and formed on a surface of the substrate;

a pair of electrodes which are formed at opposite ends of the CNT film in a different direction from the orientation direction of the CNT fibers; and

a protective coat, made of a resin, protecting the CNT film, wherein the protective coat is placed in contact with at least part of the CTN fibers on the surface of the CNT film.

2. The strain sensor according to claim 1, wherein the protective coat is laminated on the surface of the CNT film.

3. The strain sensor according to claim 2, wherein the protective coat is made of a water-based emulsion.

4. The strain sensor according to claim 1, wherein the protective coat is partially permeated into at least part of gaps between the CNT fibers forming the CNT film.

5. The strain sensor according to claim 4, wherein the protective coat includes a plurality of conductive additives.

6. The strain sensor according to claim 1, wherein the CNT film includes at least one cleavable part which is cleavable in the orientation direction of the CNT fibers.

7. The strain sensor according to claim 1, wherein each of the CNT fibers is made of a plurality of CNT monofilaments which are elongated in a longitudinal direction and which are partially connected together via at least one coupler.

8. The strain sensor according to claim 7, wherein the plurality of monofilaments is mutually connected together in a network structure.

9. The strain sensor according to claim 1, wherein the protective coat is formed by applying hydrophilic latex to the surface of the CNT film.

10. The strain sensor according to claim 1, wherein the protective coat includes a plurality of resin particles insoluble in a hydrophobic organic solvent.

11. The strain sensor according to claim 1, wherein the protective coat is made of an oil-based emulsion including a hydrophobic organic solvent as a dispersion medium and a plurality of resin particles as dispersoids.

12. The strain sensor according to claim 11, wherein the oil-based emulsion has solid concentration of particles ranging from 5 weight-percent to 10 weight-percent.

13. The strain sensor according to claim 1, wherein the electrodes are formed at opposite ends of the CNT film in a perpendicular direction to the orientation direction of the CNT fibers.

14. The strain sensor according to claim 1, wherein the protective coat with a thickness ranging from 10 μ

m to 3 mm is formed on the CNT film with a thickness ranging from 10 μ

m to 1 mm.