JP2014160041A - Strain sensor and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a strain sensor capable of improving bonding force between a CNT film and a base material and capable of improving persistence of a sensor function.SOLUTION: The strain sensor includes a flexible substrate, a CNT film laminated on the surface side of the substrate and composed of a plurality of CNT fibers oriented in one direction and a pair of electrodes arranged on end parts of the CNT film. The substrate comprises a base material layer and a CNT impregnation layer which is laminated on a surface of the base material layer and in which a partial area of the rear side of the CNT film is impregnated. The average thickness of the CNT impregnation layer of the substrate is preferably 5 to 80% of the average thickness of the CNT film. A formation material of the CNT impregnation layer preferably contains a coupling agent with the CNT fibers composing the CNT film or dispersant having adsorptivity for the CNT fibers.

Description

  The present invention relates to a strain sensor and a manufacturing method thereof.

  A strain sensor that detects strain is configured to detect strain from a resistance change of the resistor with respect to strain (stretching). As this resistor, a metal or a semiconductor is generally used. However, since metals and semiconductors have a small amount of deformation that can be reversibly expanded and contracted, there are limitations on the applications of strain sensors.

  Therefore, devices using carbon nanotubes (CNT) as the resistor have been proposed (see JP 2011-47702 A and JP 2010-281824 A). In these devices, a CNT film composed of a plurality of CNTs oriented in a predetermined direction is used. Since the CNT film can be expanded and contracted in a direction perpendicular to the orientation direction of the CNT, it can be used as a sensor that can cope with a large strain. However, in the device, since the CNT film is only bonded to the base material by intermolecular force, the CNT film is peeled off from the base material by repeated expansion and contraction, and the followability to the base material expansion and contraction is reduced. There is a risk. Therefore, there is a disadvantage in terms of the sustainability (lifetime) of the sensor function.

JP 2011-47702 A JP 2010-281824 A

  This invention is made | formed based on the above situations, and it aims at providing the distortion sensor which can raise the joining force of a CNT film | membrane and a base material, and can improve the sustainability of a sensor function. .

The invention made to solve the above problems is
A flexible substrate;
A CNT film composed of a plurality of CNT fibers laminated on the surface side of the substrate and oriented in one direction;
A strain sensor comprising a pair of electrodes disposed at an end of the CNT film,
The substrate is
A base material layer;
And a CNT impregnated layer laminated on the surface of the base material layer and impregnated in a partial region on the back side of the CNT film.

  In the strain sensor, a part of the CNT film on the back side is impregnated into the base material, so that the CNT film and the base material are combined. Therefore, according to the strain sensor, it is possible to suppress the separation of the CNT film from the base material and to increase the sustainability of the sensor function by such combination. Further, since the base material has the base material layer and the CNT impregnated layer, the substrate can be easily and surely impregnated, and the CNT film is impregnated by adjusting the thickness of the CNT impregnated layer. The film thickness can be easily adjusted.

  The average thickness of the CNT-impregnated layer of the substrate is preferably 5% to 80% of the average thickness of the CNT film. Thus, by setting the average thickness of the CNT-impregnated layer in the above range, it is possible to increase the bonding force with the substrate while maintaining the resistance change performance of the CNT film.

  It is preferable that the material for forming the CNT impregnated layer contains a coupling agent with a CNT fiber constituting the CNT film or a dispersant having an adsorptivity to the CNT fiber. In this way, when the coupling material with the CNT fiber is included in the material for forming the CNT-impregnated layer, the CNT-impregnated layer and the CNT fiber are bonded to the crosslinked structure to further improve the bonding force between the CNT film and the substrate. Can do. In addition, when the forming material of the CNT impregnated layer contains a dispersant having an adsorptivity to CNT fibers, the bonding force between the CNT film and the substrate can be further improved. As a result, the sustainability of the sensor function of the strain sensor can be further increased.

Moreover, another invention made in order to solve the said subject is:
A flexible substrate;
A CNT film composed of a plurality of CNT fibers laminated on the surface side of the substrate and oriented in one direction;
A method of manufacturing a strain sensor comprising a pair of electrodes disposed at an end of the CNT film,
A step of laminating a CNT-impregnated layer forming material on the surface of the base material layer of the substrate;
Arranging a partial region on the back side of a plurality of CNT films inside the CNT impregnated layer forming material;
And a step of curing the CNT-impregnated layer forming material after the CNT film is disposed to obtain a CNT-impregnated layer.

  In the method for manufacturing the strain sensor, the CNT fibers are arranged in an uncured state of the CNT impregnated layer inside the CNT impregnated layer constituting the substrate, or after the CNT fibers are arranged, the CNT impregnated layer is softened, Thereafter, by curing the CNT impregnated layer, a strain sensor in which a part of the CNT film is impregnated on the substrate can be obtained easily and reliably. The strain sensor obtained by the manufacturing method of the strain sensor has high sensor function durability as described above.

  The “average thickness of the CNT film” refers to the average thickness of the impregnated part of the CNT film (the part in which the plurality of CNT fibers are impregnated in the substrate) and a plurality of layers (not impregnated) laminated on the surface of the substrate. It means the sum of the average thickness of a film composed of CNT fibers.

  As described above, according to the strain sensor of the present invention, the bonding force between the CNT film and the base material can be increased, and the sustainability of the sensor function can be increased.

Schematic sectional view (a) and schematic plan view (b) of the strain sensor according to the first embodiment of the present invention. Schematic diagram showing a part of the CNT film of the strain sensor of FIG. The schematic diagram which shows an example of the manufacturing method of the distortion sensor of FIG. The schematic diagram which shows an example of the CNT film | membrane formation procedure of the distortion sensor of FIG. SEM photograph showing the formation of CNT fibers in Example 1 1 is a schematic cross-sectional view of a strain sensor according to an embodiment different from that of FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a strain sensor of the present invention will be described in detail as a first embodiment and other embodiments with reference to the drawings as appropriate.

<First embodiment>
A strain sensor 1 in FIG. 1 includes a substrate 2, a CNT film 4 formed of a plurality of CNT fibers 8 provided on the surface side of the substrate 2 and oriented in one direction, and the CNT film 8 of the CNT fiber 8. It mainly includes a pair of electrodes 3 disposed at both ends in a direction A different from the orientation direction, and a protective portion 5 that protects the CNT film 4.

  The substrate 2 is a flexible plate. The substrate 2 includes a base material layer 2a mainly composed of an elastomer, and a CNT impregnated layer 2b which is laminated on the surface of the base material layer 2a and is also composed mainly of an elastomer.

  The elastomer used for the base material layer 2a is not particularly limited as long as it has flexibility, and examples thereof include rubber and synthetic resin. Among these, rubber is preferable. By using rubber, the flexibility of the base material layer 2a (substrate 2) can be further increased.

  Examples of the rubber include natural rubber (NR), butyl rubber (IIR), isoprene rubber (IR), ethylene / propylene rubber (EPDM), butadiene rubber (BR), urethane rubber (U), and styrene / butadiene rubber (SBR). , Silicone rubber (Q), chloroprene rubber (CR), chlorosulfonated polyethylene rubber (CSM), acrylonitrile butadiene rubber (NBR), chlorinated polyethylene (CM), acrylic rubber (ACM), epichlorohydrin rubber (CO, ECO), Fluoro rubber (FKM), PDMS, etc. can be mentioned. Among these, natural rubber, silicone rubber, or urethane rubber is preferable in terms of strength and the like.

  Examples of the synthetic resin include phenol resin (PF), epoxy resin (EP), melamine resin (MF), urea resin (urea resin, UF), unsaturated polyester resin (UP), alkyd resin, polyurethane (PUR), Thermosetting polyimide (PI), polyethylene (PE), high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE), polypropylene (PP), polyvinyl chloride (PVC), polyvinylidene chloride, Polystyrene (PS), polyvinyl acetate (PVAc), acrylonitrile butadiene styrene resin (ABS), acrylonitrile styrene resin (AS), polymethyl methacrylate resin (PMMA), polyamide (PA), polyacetal (POM), polycarbonate (PC) , Degeneration Polyphenylene ether (m-PPE), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), and cyclic polyolefin (COP) and the like.

  It does not specifically limit as average thickness of the base material layer 2a, For example, they are 10 micrometers or more and 5 mm or less.

  The CNT impregnated layer 2b is laminated on the surface of the base material layer 2a, and a plurality of CNT fibers 8 constituting a CNT film 4 described later are impregnated therein. As the elastomer used for the CNT impregnated layer 2b, the same elastomer as that of the base material layer 2a can be used, but an elastomer having thermoplasticity that can be easily combined with the CNT film 4 by impregnation with the CNT fibers 8 is preferable. The elastomer used for the CNT-impregnated layer 2b is preferably one having a solubility parameter (SP value) and elastic modulus close to those of the elastomer used for the base layer 2a, and the same type of elastomer as the base layer 2a is used. Particularly preferred. By making the solubility parameter and elastic modulus of the elastomer of the CNT impregnated layer 2b and the elastomer of the base material layer 2a close to each other, the affinity between the CNT impregnated layer 2b and the base material layer 2a and the continuity at the layer boundary are increased. The bonding strength and the peeling durability can be improved.

  Further, the CNT impregnated layer 2b may contain a coupling agent. Since the CNT impregnated layer 2b contains a coupling agent, the elastomer constituting the CNT impregnated layer 2b and the CNT fibers 8 can be cross-linked, and the bonding force between the CNT film 4 and the substrate 2 can be improved.

  As said coupling agent, amino coupling agents, such as an aminosilane coupling agent, an amino titanium coupling agent, and an amino aluminum coupling agent, a silane coupling agent, etc. can be used, for example.

  As a minimum of content with respect to 100 mass parts of CNT impregnation layers of a coupling agent, 0.1 mass part is preferred and 0.5 mass part is more preferred. On the other hand, as an upper limit of content with respect to 100 mass parts of CNT impregnation layers of a coupling agent, 10 mass parts is preferable and 5 mass parts is more preferable. When the content of the coupling agent is less than the lower limit, the formation of a crosslinked structure between the CNT fibers 8 and the elastomer may be insufficient. On the other hand, when the content of the coupling agent exceeds the upper limit, residual amine that does not form a crosslinked structure increases, and the quality of the strain sensor 1 may be deteriorated.

  Further, the CNT impregnated layer 2 b may contain a dispersant having an adsorptivity to the CNT fibers 8. Examples of the dispersing agent having an adsorptive property include an interaction with an adsorbing group having a salt structure (for example, an alkylammonium salt) or a hydrophobic group (for example, an alkyl chain or an aromatic ring) of the CNT fiber 8. What has a hydrophilic group (for example, polyether etc.) which can be used in a molecule | numerator etc. can be used.

  As a minimum of content with respect to 100 mass parts of CNT impregnation layers of the above-mentioned dispersing agent, 0.1 mass part is preferred and 1 mass part is more preferred. On the other hand, as an upper limit of content with respect to 100 mass parts of CNT impregnation layers of a dispersing agent, 5 mass parts is preferable and 3 mass parts is more preferable. When the content of the dispersant is less than the lower limit, the bonding force between the CNT fiber 8 and the elastomer may be insufficient. On the contrary, when the content of the dispersant exceeds the upper limit, the dispersant that does not contribute to the bonding with the CNT fibers 8 increases, and the quality of the strain sensor 1 may be deteriorated.

  The lower limit of the average thickness of the CNT impregnated layer 2b is preferably 1 μm, and more preferably 2 μm. On the other hand, the upper limit of the average thickness of the CNT impregnated layer 2b is preferably 5 μm, and more preferably 4 μm. When the average thickness of the CNT impregnated layer 2b is less than the lower limit, the amount of CNT fibers 8 impregnated in the CNT impregnated layer 2b decreases, and the bonding force between the substrate 2 and the CNT film 4 may not be improved. Conversely, if the average thickness of the CNT impregnated layer 2b exceeds the above upper limit, the amount of CNT fibers 8 impregnated in the CNT impregnated layer 2b becomes excessive, so that the conductivity of the CNT film 4 is impaired and the sensor function is reduced or May disappear.

  The size of the substrate 2 on which the base material layer 2a and the CNT impregnated layer 2b are laminated is not particularly limited, and for example, the width can be 1 mm or more and 5 cm or less, and the length can be 1 cm or more and 20 cm or less.

  The pair of electrodes 3 are disposed at both end portions in the longitudinal direction A (direction substantially perpendicular to the orientation direction of the CNT fibers 8) on the surface side of the substrate 2. Specifically, each electrode 3 is disposed on the surface of a pair of conductive layers 6 that are spaced apart from each other in the longitudinal direction A of the surface of the substrate 2.

  The conductive layer 6 is laminated on the surface of the base material layer 2 a and the CNT film 4 to enhance electrical connectivity between the electrode 3 and the CNT film 4. The material for forming the conductive layer 6 is not particularly limited as long as it has conductivity, and for example, a conductive rubber adhesive can be used. By using the adhesive as the conductive layer 6 in this way, the adhesion of both ends of the substrate 2, the electrode 3, and the CNT film 4 can be enhanced, and the durability of the strain sensor 1 can be enhanced.

  The electrode 3 has a strip shape. The pair of electrodes 3 are arranged in parallel to each other in the width direction of the substrate 2. It does not specifically limit as a material which forms the electrode 3, For example, metals, such as copper, silver, aluminum, etc. can be used.

  The shape of the electrode 3 is not particularly limited and can be, for example, a film shape, a plate shape, a mesh shape, or the like, but a mesh shape is preferable. By using the mesh-like electrode 3 in this manner, the adhesion and adhesion with the conductive layer 6 can be enhanced. As such a mesh-like electrode 3, a metal mesh or a non-woven fabric obtained by vapor deposition or sputtering of metal can be used. The electrode 3 may be formed by applying a conductive adhesive or the like.

  The CNT film 4 has a rectangular shape in plan view, and both end portions in the longitudinal direction A are connected to the electrode 3 through the conductive layer 6. In the strain sensor 1, the CNT impregnated layer 2b is impregnated with a part of the CNT film 4 (back surface side). Specifically, some of the plurality of CNT fibers 8 constituting the CNT film 4 are present in the CNT impregnated layer 2b. Further, both end portions of the CNT film 4 are fixed while being sandwiched between the conductive layer 6 and the base material layer 2a.

  The CNT film 4 is composed of a plurality of CNT fibers 8 oriented in one direction (a direction different from the facing direction A of the pair of electrodes 3). When the CNT fibers 8 are oriented in this way and strain is applied in the direction in which the pair of electrodes 3 are separated (direction A), the contact state between the CNT fibers 8 changes, and the strain sensor 1 causes resistance. Change can be obtained. In order to detect strain more efficiently, it is desirable that the CNT film 4 has the CNT fibers 8 oriented in a direction substantially perpendicular to the facing direction A of the pair of electrodes 3, preferably in the perpendicular direction.

  Each CNT fiber 8 includes a plurality of CNT single fibers 9 as shown in FIG. Here, the CNT single fiber 9 refers to one long CNT. Moreover, the CNT fiber 8 has the connection part 10 which the edge parts of the CNT single fiber 9 connect. The CNT single fibers 9 are connected to each other in the longitudinal direction B of the CNT single fibers 9. Thus, in the CNT film 4, by using the CNT fiber 8 in which the CNT single fibers 9 are connected in the longitudinal direction B, the CNT film 4 having a wide width in the alignment direction of the CNT fiber 8 can be formed. As a result, the resistance value of the CNT film 4 can be lowered, and variations in the resistance value can also be reduced.

  Further, the plurality of CNT fibers 8 form a network structure as shown in FIG. Specifically, the plurality of CNT fibers 8 are connected or contacted in a mesh shape by the connecting portion 10 or the like. At this time, in the connecting portion 10, the end portions of three or more CNT single fibers 9 may be combined as in the connecting portion 10 a, or the end portions of the two CNT single fibers 9 in the connecting portion 10 b The intermediate part of the other CNT single fiber 9 may couple | bond. When the plurality of CNT fibers 8 form such a network structure, the CNT fibers 8 are in close contact with each other, and the resistance of the CNT film 4 can be reduced.

  At this time, the CNT fibers 8 can function as a doubly supported beam structure by connecting or contacting neighboring CNT fibers 8 with the connecting portions 10a and 10b as main base points. The connection between the CNT fibers 8 means that the connection portions 10a, 10b, etc. and the CNT fibers 8 are electrically connected, and the case where the non-connection portions of the CNT fibers 8 are electrically connected is also included in the connection. . The contact between the CNT fibers 8 means that the connection portions 10a, 10b, etc. and the CNT fibers 8 are touched but not electrically connected, and the portions that are not the connection portions of the CNT fibers 8 are in contact with each other. Even if they are not connected, they are included in the contact. The CNT fiber 8 that functions as a doubly supported beam has a large spring constant. Therefore, the CNT fiber 8 has a structure that is difficult to expand and contract in the direction perpendicular to the orientation direction B (longitudinal direction A of the CNT film 4). Accordingly, the rigidity of the CNT film 4 is increased in the direction perpendicular to the alignment direction B of the CNT fibers 8 (longitudinal direction A of the CNT film 4). Can be detected sensitively, and the linearity can be further improved. In addition, the connection part 10 of the CNT fiber 8 serves as a main base point, and may be connected or contacted with not only the adjacent CNT fibers 8 but also some CNT fibers 8 jumped over. As described above, the CNT film 4 made of the complex network-like CNT fiber 8 has a lower resistance value and can be a strain sensor having a high rigidity in a direction perpendicular to the CNT fiber 8.

  The CNT fibers 8 are in a state in which each CNT single fiber 9 is substantially oriented in the longitudinal direction B of the CNT fibers 8 and is not twisted. By using such a CNT fiber 8, the uniformity of the CNT film 4 can be enhanced and the linearity as a strain sensor can be enhanced.

  Moreover, in the said connection part 10, each CNT single fiber 9 is couple | bonded by the intermolecular force. For this reason, even when a plurality of CNT fibers 8 are connected in a mesh shape by the connecting portion 10, an increase in resistance due to the presence of the connecting portion 10 is suppressed.

  The lower limit of the width of the CNT film 4 is preferably 1 mm, and more preferably 1 cm. On the other hand, the upper limit of the width of the CNT film 4 is preferably 10 cm, and more preferably 5 cm. Thus, by making the width of the CNT film 4 relatively large, it is possible to reduce the resistance value of the CNT film 4 as described above, and to reduce variations in the resistance value.

  The average thickness of the CNT film 4 is not particularly limited. For example, the lower limit of the average thickness of the CNT film 4 is preferably 1 μm, and more preferably 10 μm. On the other hand, the upper limit of the average thickness of the CNT film 4 is preferably 5 mm, and more preferably 1 mm. If the average thickness of the CNT film 4 is less than the lower limit, it may be difficult to form such a thin film, the resistance may increase excessively, or the CNT impregnated layer 2b may not be sufficiently impregnated with the CNT film 4. When the CNT film 4 is impregnated, the sensor function of the strain sensor 1 may be reduced or lost. Conversely, when the average thickness of the CNT film 4 exceeds the upper limit, the sensitivity to strain may be reduced.

  The lower limit of the average thickness of the impregnated portion of the CNT film 4 in the CNT-impregnated layer 2b is preferably 5% of the average thickness of the CNT film 4 and more preferably 10%. On the other hand, the upper limit of the average thickness of the impregnated portion is preferably 80% of the average thickness of the CNT film 4 and more preferably 50%. When the average thickness of the impregnated portion of the CNT film 4 is less than the lower limit, the bonding force between the substrate 2 and the CNT film 4 may not be improved. On the contrary, when the average thickness of the impregnated portion of the CNT film 4 exceeds the upper limit, the amount of the CNT fibers 8 impregnated in the CNT impregnated layer 2b becomes excessive, so that the sensor function of the strain sensor 1 may be reduced or lost. There is.

The lower limit of the density of the CNT film 4 is preferably ^{1.0g / cm 3, 0.8g / cm} 3 is more preferable. On the other hand, the upper limit of the density of the CNT film 4 is preferably ^{1.8g / cm 3, 1.5g / cm} 3 is more preferable. When the density of the CNT film 4 is less than the lower limit, the resistance value of the CNT film 4 may be increased. On the contrary, when the density of the CNT film 4 exceeds the upper limit, there is a possibility that a sufficient resistance change cannot be obtained.

  Note that the CNT film 4 may have a single-layer structure in which the CNT fibers 8 are arranged substantially in parallel in a planar shape, or may have a multilayer structure. However, in order to ensure a certain degree of conductivity, a multilayer structure is preferable.

  Moreover, it is preferable to apply a conductive rubber adhesive to the surface of the CNT film 4. By applying the conductive rubber-based adhesive, the CNT fibers 8 are electrically joined, so that the sensor function of the strain sensor 1 can be improved. The conductive rubber-based adhesive is not particularly limited as long as it has conductivity, and for example, an adhesive containing carbon black, silver nanoparticles, or the like can be suitably used.

  The coating amount of the conductive rubber-based adhesive is preferably 5% by mass or more and 10% by mass or less in terms of solid content with respect to the mass of the CNT film 4. When the application amount of the conductive rubber-based adhesive is less than the above range, the effect of improving the electrical bonding degree may not be sufficiently obtained. On the contrary, when the application amount of the conductive rubber adhesive exceeds the above range, the flexibility of the strain sensor 1 may be reduced. The conductive rubber-based adhesive is preferably applied in multiple steps in order to form a film uniformly on the surface of the CNT film 4.

  As the CNT single fiber 9 (CNT), either single-wall single-wall nanotubes (SWNT) or multi-wall multi-wall nanotubes (MWNT) can be used, but MWNT is preferable from the viewpoint of conductivity and heat capacity. MWNT having a diameter of 1.5 nm or more and 100 nm or less is more preferable.

  The CNT single fiber 9 (CNT) can be manufactured by a known method, for example, CVD method, arc method, laser ablation method, DIPS method, CoMoCAT method and the like. Among these, it is preferable to manufacture by a CVD method using iron as a catalyst and ethylene gas from the viewpoint that CNT (MWNT) having a desired size can be efficiently obtained. In this case, a CNT crystal having a desired length can be obtained which is obtained by forming an iron or nickel thin film serving as a catalyst on a substrate such as a quartz glass substrate or a silicon substrate with an oxide film and then vertically growing.

  The protection part 5 has a film shape and is laminated on the surface of the CNT film 4. Specifically, as shown in FIG. 1, the protection unit 5 covers a part of the surfaces of the CNT film 4 and the pair of conductive layers 6. A part of the pair of conductive layers 6 has an exposed portion for laminating the electrode 3 that is not covered with the protective portion 5. By laminating the protective part 5 in this way, the protective part 5 is in contact with at least a part of the surface of the CNT fiber 8 and protects the CNT film 4. In particular, according to the strain sensor 1, the protective part 5 is laminated on the surface of the CNT film 4, so that the CNT film 4 is damaged due to unexpected contact or the like, foreign matter is mixed into the gap between the CNT fibers 8, Alternatively, it is possible to suppress adhesion of moisture or floating gas to the CNT fibers 8.

  The protection part 5 is made of an elastomer. Examples of the elastomer include rubbers and synthetic resins exemplified as the material of the substrate 2, and among these, rubber is preferable. By using rubber, a sufficient protective function can be exhibited even against large strains.

  The protective part 5 is preferably formed from an aqueous emulsion. An aqueous emulsion refers to an emulsion in which the main component of the dispersion medium is water. CNT is highly hydrophobic. Therefore, when the protective part 5 is formed from an aqueous emulsion, for example, when the protective part 5 is provided by coating or dipping, the protective part 5 is not impregnated in the CNT film 4 and is laminated on the surface of the CNT film 4 can do. By doing in this way, it suppresses that the elastomer which forms the protection part 5 penetrates into the CNT film 4 and affects the resistance change of the CNT film 4, and the strain sensitivity of the CNT film 4 due to the presence of the protection part 5 is suppressed. The decrease can be suppressed. The aqueous emulsion can be made a more stable protective part 5 through a drying process.

  The main component of the dispersion medium of the aqueous emulsion is water, but other hydrophilic dispersion medium such as alcohol may be contained. Further, the dispersoid of the emulsion is usually an elastomer, and the above-described rubber, particularly natural rubber is preferable. Examples of the preferable emulsion include so-called latex in which the dispersion medium is water and the rubber is a dispersoid, and natural rubber latex is preferable. By using natural rubber latex, a thin and strong protective film can be formed.

  It does not specifically limit as average thickness of the protection part 5, For example, they are 10 micrometers or more and 3 mm or less.

  The CNT film 4 has a portion 11 that can be cleaved along the orientation direction B of the CNT fiber 8. Thus, by forming the portion 11 that can be cleaved along the alignment direction B of the CNT fiber 8 in the CNT film 4, the transient response of the resistance change is enhanced, and it is excellent against a larger strain (stretching). The sensor function can be demonstrated. In this case, the protective portion 5 that contacts the cleavable portion 11 is greatly deformed, while the protective portion 5 that is in contact with the non-cleavable portion is less deformed. The cleavable portion 11 may be formed by being inserted up to the portion impregnated in the CNT impregnated layer 2b.

  According to the strain sensor 1, since the CNT film 4 is provided in this manner, the CNT film 4 is distorted (stretched / contracted) in accordance with the strain of the substrate 2, and the resistance of the CNT film 4 changes. It can function as a sensor for detecting distortion. The distortion of the substrate 2 includes not only expansion and contraction in the longitudinal direction A but also deformation in the normal direction of the substrate 2 and twisting about the longitudinal direction. According to the strain sensor 1, such a strain of the substrate 2 can also be detected. In addition, according to the strain sensor 1, since the substrate 2 (CNT-impregnated layer 2b) is impregnated with a part of the CNT film 4 (back surface side), peeling of the CNT film 4 from the base material 2 is suppressed, The sustainability of the sensor function can be increased.

(Production method)
Although it does not specifically limit as a manufacturing method of the distortion sensor 1, For example, it can manufacture with the following manufacturing processes.

(1-1) As shown in FIG. 3A, a base material layer 2a is formed on a release plate such as a slide glass. Specifically, the slide glass X is immersed in a latex or an elastomer solution and then dried. Thereby, the base material layer 2a made of an elastomer and having a rectangular shape in a plan view can be formed on the surface of the slide glass X. In addition, as a release plate, you may use other board | plate materials, such as synthetic resins other than a slide glass.

(1-2) As shown in FIG. 3B, an elastomer solution, which is a material for forming the CNT impregnated layer 2b, is applied to the surface of the base material layer 2a.

(1-3) As shown in FIG. 3C, the CNT film 4 is formed while impregnating the CNT fibers 8 on the surface of the forming material of the uncured CNT impregnated layer 2b. Specifically, CNT paper (film) composed of a plurality of CNT fibers 8 oriented in one direction is disposed from the surface of the CNT impregnated layer 2b, and the back side thereof is impregnated into the CNT impregnated layer 2b. At this time, the orientation of the CNT paper is adjusted so that the CNT fibers 8 are oriented in a direction substantially perpendicular to the opposing direction (longitudinal direction) of the pair of electrodes 3 stacked in the subsequent process.

(1-4) The material for forming the uncured CNT impregnated layer 2b impregnated with the CNT fibers 8 is cured to form the CNT impregnated layer 2b. Specifically, after disposing the CNT paper, the uncured CNT impregnated layer 2b is cured by drying or heating.

  In the CNT paper, a catalyst layer is formed on a growth base material, a plurality of CNT fibers 8 oriented in a certain direction are grown by a CVD method, and are drawn as they are without twisting as shown in FIG. It can be obtained by taking out a necessary amount of sheet-like CNT fibers 8 after being wound around the plate material or cylinder material. This CNT paper is disposed on the surface of the CNT impregnated layer 2b.

  Further, after the CNT film 4 is formed, it is preferable to spray the CNT film 4 with a solvent such as isopropyl alcohol or ethanol, or soak it in this solvent and then dry it. Through this step, the adhesion between the CNT film 4 and the CNT impregnated layer 2b can be further increased, and the CNT fibers 8 constituting the CNT film 4 can be densified. In addition, by increasing the density of the CNT fibers 8 in this way, the contact area between the CNT fibers can be increased in advance, and the effect of lowering the power consumption by reducing the resistance of the CNT film 4 and the resistance when strain is applied. An effect of increasing the sensitivity of change can be obtained.

(1-5) A conductive rubber adhesive is applied to the surface of the CNT film 4. Thereafter, the conductive rubber adhesive is cured by drying at room temperature for 30 minutes. The number of times of applying the conductive rubber adhesive is preferably 2 times or more.

(1-6) As shown in FIG. 3D, a conductive rubber adhesive is applied to both ends of the substrate 2 in the longitudinal direction to form a conductive layer 6. At this time, the conductive layer 6 is formed so that the conductive layer 6 covers a part of the CNT film 4.

(1-7) As shown in FIG. 3 (e), the protective part 5 is laminated on the surfaces of the CNT film 4 and the conductive layer 6. Specifically, the protective part 5 is formed by immersing the entire glass including the slide glass in latex or applying latex to the surface of the CNT film 4. Thus, the protective part 5 can be laminated | stacked on the CNT film | membrane 4 surface by using latex. At this time, the protective portion 5 is formed so that a part of the conductive layer 6 is exposed so that the electrode 3 can be disposed. As described above, the latex is an aqueous emulsion and has hydrophilicity.

  In addition, it can also be set as the strain sensor which the protection part 5 exists in at least one part of the clearance gap between the CNT fibers 8 which comprise the CNT film | membrane 4 by using an oil-based emulsion instead of the said water-based emulsion.

(1-8) As shown in FIG. 3 (f), the electrode 3 is laminated on the surface of each conductive layer 6.

(1-9) After stacking the electrodes 3, at least one pair of strain sensors 1 can be obtained by cutting out these stacked bodies from both sides of the slide glass. You may cut off the both ends of the width direction in a slide glass. Moreover, the some distortion sensor 1 can also be manufactured from one side by dividing in a longitudinal direction. In addition, after cutting out from the slide glass, the strain sensor 1 can be extended in the direction opposite to the electrode 3 to form a cleavable portion 11 in the CNT film 4 or the protective film 5.

  In addition, the above-mentioned (1-2)-(1-4) which is the lamination | stacking procedure of the CNT film | membrane 4 can also be set as the following procedures.

(1-2 ') An elastomer solution, which is a material for forming the CNT impregnated layer 2b, is applied to the surface of the base material layer 2a, and is cured by drying or heating.

(1-3 ′) As shown in FIG. 4, the CNT fiber 8 is wound on a slide glass (CNT-impregnated layer 2 b). By doing in this way, the CNT film | membrane 4 which consists of several CNT fiber 8 oriented in one direction (a direction perpendicular to the opposing direction of a pair of electrode 3) can be obtained. At this time, the CNT fiber 8 can be wound by sandwiching both ends of the slide glass (substrate 2) with a pair of supporters 13 and rotating the slide glass (substrate 2) around the longitudinal direction. In addition, you may mask the width direction both ends of the slide glass with the masking tape 12 grade | etc.,.

(1-4 ') When the winding amount of the CNT fiber 8 reaches a certain value (amount to be impregnated into the CNT impregnated layer 2b), the CNT impregnated layer 2b is heated with an iron or the like to be softened and wound. 8 is impregnated into the CNT impregnated layer 2b. Thereafter, the CNT impregnated layer 2b is again cured by drying or heating, and the remaining CNT fibers 8 are wound on the CNT impregnated layer 2b to form the CNT film 4.

  The CNT fibers 8 can be obtained by pulling out crystals of CNT single fibers 9 (CNT) vertically grown on the substrate by the CVD method as described above without twisting them (see FIG. 5). The CNT fiber 8 obtained in this way is composed of a plurality of CNT single fibers 9, and has a structure having a connecting portion for connecting the CNT single fibers 9 to each other in the longitudinal direction.

<Other embodiments>
The strain sensor of the present invention is not limited to the above embodiment. For example, in the present invention, the electrodes 3 may be disposed at both ends of the orientation direction (direction A) of the CNT fibers 8 as in the strain sensor 101 shown in FIG. In the strain sensor 101, when a strain is applied in a direction in which the pair of electrodes 3 are separated (direction A), the CNT fiber 8 is deformed (stretched) in the longitudinal direction, and a resistance change can be obtained. In the case of the strain sensor 101 in which the strain sensing direction is the orientation direction of the CNT fibers 8, it is preferable to impregnate the CNT film 4 with the protective layer 5, and the density of the CNT fibers 8 in the CNT film 4 is first. It may be smaller than the embodiment. Further, the CNT fibers 8 tend to exist as a plurality of bundles, and the protective layer 5 impregnates the gaps between the plurality of bundles in the CNT film 4, thereby increasing the strength of the CNT fibers 8. It is possible to prevent cutting due to strain in the orientation direction.

  The strain sensor may have a configuration in which a conductive layer is provided on the back surface and the front surface of the electrode. Specifically, a pair of first conductive layers are provided on the surface of the substrate so as to be spaced apart at both ends in the longitudinal direction A, and a part of the CNT film and a pair of electrodes are provided on the surface of the first conductive layer. A pair of second conductive layers is provided so as to cover the CNT film and a part of the surface of the electrode. As a result, both end portions of the CNT film in the longitudinal direction are sandwiched between the first conductive layer and the second conductive layer. By providing such a conductive layer, the electrical connectivity between the electrode and the CNT film can be improved.

  Furthermore, in the strain sensor, the protective part only needs to be in contact with at least a part of the CNT fiber surface, for example, only the vicinity of the surface of the CNT film is impregnated with an elastomer that forms a protective film only on a part of the CNT film. It may be. Furthermore, the protection part may be laminated | stacked on the CNT film | membrane, having a protection part in at least one part of the clearance gap between CNT fibers. Also in such a strain sensor, since the CNT film is protected by the protection unit, the sustainability of the strain sensor can be improved.

  Further, the substrate is not limited to a plate-like body made of a complete rectangular parallelepiped, and can be used by being deformed. For example, the use of the strain sensor can be expanded by using a cylindrical shape or a wave shape. As the CNT fiber, a CNT fiber obtained by spinning CNT may be used. Furthermore, in the CNT film, a further pair of electrodes facing each other in the direction perpendicular to the facing direction of the pair of electrodes may be provided. By providing two pairs of electrodes orthogonal to each other in this way, the strain sensor can be used as a two-dimensional sensor. In addition, by covering the surface of the strain sensor with an adhesive resin, the strain sensor can be easily attached to a place where it is desired to detect strain such as a human body or a structure.

  As described above, the strain sensor of the present invention is excellent in sustainability because a part of the CNT film is impregnated in the substrate, and also functions sufficiently as a sensor, such as a pressure sensor, load cell, torque sensor, position It can be widely used as a sensor or the like.

DESCRIPTION OF SYMBOLS 1,101 Strain sensor 2 Board | substrate 2a Base material layer 2b CNT impregnation layer 3 Electrode 4 CNT film | membrane 5 Protection part 6 Conductive layer 8 CNT fiber 9 CNT single fiber 10, 10a, 10b Connection part 11 Cleavageable part 12 Masking tape 13 Support Ingredients

Claims (4)

A flexible substrate;
A CNT film composed of a plurality of CNT fibers laminated on the surface side of the substrate and oriented in one direction;
A strain sensor comprising a pair of electrodes disposed at an end of the CNT film,
The substrate is
A base material layer;
A strain sensor comprising: a CNT impregnated layer laminated on a surface of the base material layer and impregnated in a partial region on the back side of the CNT film.   The strain sensor according to claim 1, wherein the average thickness of the CNT-impregnated layer of the substrate is 5% or more and 80% or less of the average thickness of the CNT film.   The strain sensor according to claim 1, wherein the material for forming the CNT impregnated layer contains a coupling agent with a CNT fiber constituting the CNT film or a dispersant having an adsorptivity to the CNT fiber. A flexible substrate;
A CNT film composed of a plurality of CNT fibers laminated on the surface side of the substrate and oriented in one direction;
A method of manufacturing a strain sensor comprising a pair of electrodes disposed at an end of the CNT film,
A step of laminating a CNT-impregnated layer forming material on the surface of the base material layer of the substrate;
Arranging a partial region on the back side of a plurality of CNT films inside the CNT impregnated layer forming material;
And a step of curing the CNT-impregnated layer forming material after the CNT film is disposed to obtain a CNT-impregnated layer.

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