Sensors and Sensor Systems

Abstract

To provide a sensor capable of constantly monitoring the concentration of chemical substances in an environment more inexpensively without being attended.SOLUTION: A sensor 10 includes: an antenna 11 that loses a radio wave transmitting / receiving function by reacting with chemical substances in an environment; and a communication unit 12 that transmits and receives signals to / from an external device via the antenna 11.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a sensor and a sensor system including the same. [Background technology]

[0002] Conventionally, in treatment facilities for sewage, industrial waste, etc., the concentrations of chemical substances present in the environment have been measured in order to prevent health damage to workers, fatal accidents, etc. As a technology for measuring the concentrations of such chemical substances, for example, a sensor that detects the concentration of hydrogen sulfide based on a change in the conductivity of an electrode (metal) that has reacted with hydrogen sulfide has been proposed (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 60-230050 Summary of the Invention [Problem to be solved by the invention]

[0004] Sensors for measuring the concentration of chemical substances such as hydrogen sulfide are relatively expensive, so installing many of them within a facility can be cost prohibitive. Furthermore, methods in which workers carry sensors into the facility to measure the concentration of chemical substances make it difficult to constantly monitor the concentration of chemical substances, and the work is time-consuming and laborious, and there are also concerns about health risks to workers.

[0005] An object of the present invention is to provide a sensor and a sensor system that can monitor the concentration of chemical substances in the environment at lower cost, continuously, and unattended. [Means for solving the problem]

[0006] The present invention solves the problems by the following means. For ease of understanding, the following description will be given with reference numerals corresponding to the embodiments of the present invention, but the present invention is not limited to these. Furthermore, the configurations described with reference numerals may be modified as appropriate, and at least a portion of the configurations may be replaced with other components.

[0007] The first invention relates to a sensor (10) including an antenna (11) that loses its ability to transmit and receive radio waves by reacting with chemical substances in the environment, and a communication unit (12) that transmits and receives signals to and from an external device via the antenna.

[0008] A second aspect of the present invention is the sensor according to the first aspect of the present invention, wherein the antenna is formed from a metal whose conductivity changes when it reacts with chemical substances in the environment.

[0009] A third invention is the sensor according to the second invention, wherein the metal is silver.

[0010] A fourth aspect of the present invention is the sensor according to the second or third aspect of the present invention, wherein the metal has a nanowire shape.

[0011] The fifth invention is a sensor according to any one of the first to fourth inventions, wherein the antenna comprises a substrate (15) that is permeable to the chemical substance, an adsorption layer (17) that is provided on the front side of the substrate and adsorbs the chemical substance, and an antenna part (110) that is provided on the back side of the substrate, and the reaction rate between the antenna part and the chemical substance differs depending on the adsorption performance of the adsorption layer for the chemical substance.

[0012] A sixth aspect of the present invention relates to a sensor system including a sensor according to any one of the first to fifth aspects of the present invention, and an external device (20) that transmits and receives radio waves to and from the sensor. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a sensor and a sensor system that can monitor the concentration of chemical substances in the environment at low cost, continuously, and unmanned. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a conceptual diagram showing the configuration of a gas monitoring system 1 according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating an installation state of the sensor 10. [Figure 3] 1 is a diagram illustrating the configuration of a sensor 10. FIG. [Figure 4] 10 is a diagram showing an example of a sensor management table stored in the management server 30. FIG. [Figure 5] FIG. 2 is a cross-sectional view showing the layer structure of the antenna 11. [Figure 6] FIG. 2 is a cross-sectional view showing the layer structure of the antenna layer 16 in detail. [Figure 7A] FIG. 10 is a diagram illustrating the state of the adsorption layer 17 when the concentration of hydrogen sulfide is low. [Figure 7B] FIG. 10 is a diagram illustrating the state of the adsorption layer 17 when the concentration of hydrogen sulfide is high. [Figure 8] 2A to 2C are schematic diagrams showing the manufacturing process of the antenna 11. [Figure 9] 2A to 2C are schematic diagrams showing the manufacturing process of the antenna 11. [Figure 10] 4 is a flowchart showing the procedure of a process for monitoring the concentration of hydrogen sulfide by the gas monitoring system 1. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of a sensor and a sensor system according to the present invention will be described. Note that the drawings attached to this specification are all schematic diagrams, and the shape, scale, aspect ratio, and the like of each part have been modified or exaggerated from the actual product in consideration of ease of understanding, etc.

[0016] Fig. 1 is a conceptual diagram showing the configuration of a gas monitoring system 1 according to this embodiment. Fig. 2 is a diagram illustrating the installation state of a sensor 10. Fig. 3 is a diagram illustrating the configuration of the sensor 10. Fig. 4 is a diagram illustrating an example of a sensor management table stored in the management server 30.

[0017] In this embodiment, an example will be described in which the gas monitoring system 1 is applied to a system for monitoring the concentration of hydrogen sulfide in a sewer tunnel. A sewer tunnel is one type of sewer pipe included in a sewage treatment facility. 1, the gas monitoring system 1 is made up of sensors 10a to 10c, a relay device 20, a management server 30, and a communication network 40. Of these, the sensors 10a to 10c and the relay device 20 represent one embodiment of a sensor system according to the present invention.

[0018] The sensors 10a, 10b, and 10c are wireless IC tags configured to maintain or lose their ability to transmit and receive radio waves depending on the concentration of hydrogen sulfide (a chemical substance). As will be described later, the sensor 10 is capable of transmitting and receiving radio waves when the concentration of hydrogen sulfide is low, and is unable to transmit and receive radio waves when the concentration of hydrogen sulfide is high. As shown in FIG. 2, the sensors 10a to 10c are attached to the inner wall W of the sewer tunnel by, for example, an adhesive sheet (not shown). The sensors 10a to 10c may also be attached to the inner wall W of the sewer tunnel by, for example, anchor bolts. The sensors 10a to 10c are installed in the sewer tunnel at intervals of, for example, several tens to 100 meters.

[0019] In this embodiment, as an example, a case where three sensors 10a to 10c are installed in a sewer tunnel will be described, but the number of sensors to be installed is not limited to this example. Only one sensor may be installed in a facility to be monitored, or tens to hundreds of sensors may be installed. In the following description, sensors 10a to 10c may also be referred to as "sensor 10" or "each sensor 10."

[0020] As shown in FIG. 3, the sensor 10 includes an antenna 11, a communication unit 12, and a battery 13. The antenna 11 is an antenna that transmits and receives data to and from the relay device 20 via radio waves. The antenna 11 is configured as an antenna for radio waves that conforms to, for example, LPWA (Low Power Wide Area) in order to enable low power consumption and long-distance communication. An example of a radio wave that conforms to LPWA is a radio wave with a center frequency in the 920 MHz band. In this case, the data communication speed is, for example, about 100 to 250 bps. The communication distance of the radio waves is, for example, about 10 to 50 km.

[0021] Furthermore, antenna 11 is configured so that it loses its radio wave transmission and reception function when it reacts with chemical substances in the environment. Specifically, antenna 11 is configured so that it can transmit and receive data when the concentration of hydrogen sulfide in the sewer tunnel is low, but cannot transmit and receive data when the concentration of hydrogen sulfide is high. In this way, antenna 11 functions both as an antenna that transmits and receives data and as a sensor that detects the concentration of hydrogen sulfide.

[0022] As shown in Fig. 3, the antenna 11 of this embodiment is configured as a dipole antenna. The antenna 11 is attached to a sensor plate 130 that serves as the base of the sensor 10. An end of the antenna 11 is electrically connected to a communication unit 12 (described later) provided on a circuit board 120. Note that the type and antenna pattern of the antenna 11 are merely examples and are not limited to the example shown in Fig. 3. The antenna 11 is not limited to a dipole type and may be any type of antenna as long as it can transmit and receive data to and from the relay device 20 via radio waves. For example, the antenna 11 may be a monopole antenna, a patch antenna, or the like.

[0023] The communication unit 12 is an electronic component that transmits and receives data (signals) to and from the relay device 20 via the antenna 11. The communication unit 12 includes a rectifier circuit, an amplifier circuit, an IC chip, and the like (none of which are shown). An identification number unique to each sensor 10 is stored in the IC chip of the communication unit 12. When the communication unit 12 receives a response request signal from the relay device 20, it transmits its own identification number, which is stored in the memory of the IC chip, as a response signal to the relay device 20 via the antenna 11.

[0024] Battery 13 is a power source for communication that supplies power to communication unit 12. For example, a button battery is used as battery 13. Note that the type of battery 13 is not limited to a button battery, and may be, for example, a rechargeable lithium ion battery or a non-rechargeable dry cell battery. As shown in FIG. 3, the battery 13 and the communication unit 12 are mounted on a circuit board 120, which is attached to a sensor plate 130 together with the antenna 11.

[0025] Returning to FIG. 1, the configuration of the gas monitoring system 1 will now be described. The relay device 20 is a communication device that transfers data between the sensor 10 and a management server 30 (described later). In this embodiment, the relay device 20 corresponds to an external device that transmits and receives radio waves to and from the sensor 10. The relay device 20 converts the data format of a response request signal transmitted from the management server 30, which is a higher-level device, into a data format that conforms to the communication standard of the sensor 10 and transmits the signal to the sensor 10. The relay device 20 also converts the data format of a response signal transmitted from the sensor 10 into a data format that conforms to the communication standard of the management server 30 and transmits the signal to the management server 30.

[0026] As described above, data is transmitted and received between the relay device 20 and the sensor 10 using radio waves with a center frequency of, for example, 920 MHz. Data is also transmitted and received between the relay device 20 and the management server 30 using a wireless communication method for mobile phones, such as 3G, LTE (registered trademark), 4G, or 5G. When transmitting and receiving data using a wireless communication method for mobile phones, the relay device 20 connects to a communication network 40 via a base station 50. The communication network 40 is an internet line that interconnects the relay device 20 and the management server 30. In the following description of data transmission and reception between the sensor 10 and the management server 30, the base station and the communication network 40 will be omitted as appropriate.

[0027] Although not shown, the relay device 20 is also installed on the inner wall of the sewer tunnel, similar to the sensors 10. If one relay device 20 cannot cover communications with all of the sensors 10, a router for relaying may be installed, or multiple relay devices 20 may be installed.

[0028] The management server 30 is a server managed and operated by a sewage treatment facility operator or the like. The management server 30 stores data relating to the communication status of each sensor 10 in a sensor management table. As shown in FIG. 4, the sensor management table stores the identification number (sensor No.) of the sensor that transmitted the response request signal, the presence or absence of a response signal (◯ or ×), and the time when the response request signal was transmitted (or the time when the response signal was received), in association with each other. Note that the data items in the sensor management table shown in FIG. 4 are an example, and are not limited to this example.

[0029] When a predetermined time arrives, the management server 30 transmits a response request signal to each sensor 10 via the relay device 20. The management server 30 then receives a response signal from each sensor 10 via the relay device 20 and stores the response signal in the sensor management table. The management server 30 analyzes the data stored in the sensor management table in real time or periodically. The management server 30 extracts the identification number included in the response signal and updates the data for the corresponding sensor 10 in the sensor management table. If the management server 30 does not receive a response signal from a sensor 10, the management server 30 notifies the administrator of the identification number of the sensor 10 along with message data indicating an abnormality. In FIG. 4, since the management server 30 has not received a response signal from the sensor 10 with sensor number AA00003, the management server 30 notifies the administrator that an abnormality has occurred in the sensor 10 with sensor number AA00003. The transmission of the response request signal to each sensor 10 may be performed at multiple preset times or at predetermined time intervals.

[0030] Next, the layer structure of the antenna 11 will be described. Fig. 5 is a cross-sectional view showing the layer structure of the antenna 11. Fig. 6 is a cross-sectional view showing the layer structure of the antenna layer 16 in detail. In Figs. 5 and 6, the vertical direction of the drawings will be described as the thickness direction Z. In the thickness direction Z, the upper side in the drawings is the Z1 side (front side), and the lower side is the Z2 side (back side). Note that the layer structure of the antenna 11 shown in Fig. 5 is an example, and is not limited to the example shown in Fig. 5. Also, Figs. 5 and 6 show the thickness of each layer schematically, and differ from the actual thickness. 5, the antenna 11 includes a first substrate 15, an antenna layer 16, an adsorption layer 17, an adhesive layer 18, and a second substrate 19. The antenna 11 is formed as a single sheet-like member in which the above layers are laminated.

[0031] The first substrate 15 is a film material that supports the antenna layer 16 and the adsorption layer 17. The first substrate 15 is made of a material that is highly permeable to hydrogen sulfide. For example, triacetyl cellulose (TAC), polyethylene terephthalate (PET), cycloolefin polymer (COP), polycarbonate (PC), etc. can be used as the first substrate 15. The first substrate 15 is not limited to being in the form of a sheet or film, and may also be in the form of a thinner layer (for example, an acrylic layer).

[0032] The antenna layer 16 is a layer on which the antenna section 110 is formed. The antenna layer 16 is provided on the back side (Z2 side) of the first base material 15. In the antenna layer 16, the portion constituting the antenna section 110 (the portion of the antenna pattern) includes conductive fibers 161 and a resin portion 162, as shown in FIG. 6. Note that the portion constituting the antenna section 110 only needs to include the conductive fibers 161, and does not necessarily need to include the resin portion 162. The conductive fibers 161 are disposed within the resin portion 162. In this specification, a "conductive fiber" is defined as a fiber that is conductive and has a shape whose length is sufficiently longer than its thickness (for example, its diameter). For example, a fiber whose length is approximately five times or more its thickness is included in the conductive fiber.

[0033] It is preferable that a plurality of conductive fibers 161 are present in the portion of the antenna layer 16 that constitutes the antenna portion 110. The conductive fibers 161 are in contact with each other in the thickness direction (Z direction) of the antenna layer 16 so as to enable electrical conduction on the surface on the front side (Z1 side) of the antenna layer 16 (in other words, so as to enable reaction with hydrogen sulfide that has permeated the first base material 15).

[0034] In the antenna layer 16, it is preferable that the conductive fibers 161 present in the portion constituting the antenna unit 110 contact each other to form a network structure (mesh structure) in the planar direction (two-dimensional direction). When the conductive fibers 161 form a network structure, a conductive path can be formed in the planar direction along the antenna pattern of the antenna unit 110 (see FIG. 3).

[0035] The film thickness of the antenna layer 16 is preferably less than 300 nm, for example. By making the film thickness of the antenna layer 16 less than 300 nm, some of the conductive fibers 161 come into contact with the interface with the first substrate 15, allowing for a greater reaction with hydrogen sulfide that has permeated through the first substrate 15. If the film thickness of the antenna layer 16 is 300 nm or more, the film thickness of the resin portion 162 becomes too thick, and most of the conductive fibers 161 are buried in the resin portion 162, which may make it difficult for the conductive fibers 161 to react with hydrogen sulfide near the interface with the first substrate 15. When the film thickness of the resin portion 162 is increased, a conductive auxiliary agent mainly composed of silver may be added to the resin portion 162.

[0036] In the antenna layer 16, the surface resistivity (Ω / □) of the portion constituting the antenna unit 110 can be adjusted by the amount of conductive fibers 161 arranged in the antenna layer 16. If the fiber diameter, fiber length, material, etc. of the conductive fibers 161 are the same, the surface resistivity can be increased by reducing the amount of conductive fibers 161. Furthermore, the surface resistivity can be decreased by increasing the amount of conductive fibers 161. In the antenna layer 16, the surface resistivity of the portion constituting the antenna unit 110 is preferably 100 Ω / □ or less.

[0037] The surface resistivity (Ω / □) of the portion constituting the antenna portion 110 can be measured, for example, in an environment of a temperature of 23±5°C and a relative humidity of 30% or more and 70% or less using a contact resistivity meter (product name "Loresta AX MCP-T370 type", manufactured by Mitsubishi Chemical Analytech Co., Ltd., terminal shape: ASP probe) and a non-destructive (eddy current method) resistivity meter (product name "EC-80P", manufactured by Napson Co., Ltd.) that conforms to JIS K 7194:1994 (resistivity test method using the four-probe method for conductive plastics).

[0038] The fiber diameter of the conductive fiber 161 is preferably 100 nm or less. The fiber length of the conductive fiber 161 is preferably 1 μm or more. If the fiber length of the conductive fiber 161 is 1 μm or more, an antenna unit 110 having sufficient conductive performance can be formed. The upper limit of the fiber length of the conductive fiber 161 may be 100 μm or less, 30 μm or less, or 20 μm or less. The lower limit of the fiber length of the conductive fiber 161 may be 3 μm or more, 5 μm or more, or 10 μm or more.

[0039] In this embodiment, silver, which reacts with hydrogen sulfide to reduce its conductivity, is used as the metal constituting the conductive fibers 161. Silver reacts with hydrogen sulfide in the air to form silver oxide (AgS), as represented by the following formula (1): H2S+2Ag→Ag2S+H2 (1) When silver reacts with hydrogen sulfide and turns into silver oxide, its resistance increases, its conductivity decreases, and current flow becomes more difficult. The reaction rate between silver and hydrogen sulfide depends mainly on the concentration of hydrogen sulfide. That is, when the concentration of hydrogen sulfide is low, the reaction rate is slow (or almost nonexistent), and when the concentration of hydrogen sulfide is high, the reaction rate becomes faster. Therefore, an antenna pattern (antenna unit 110) made of silver does not increase in resistance and can pass a specified current when the concentration of hydrogen sulfide is low. Therefore, the antenna pattern can maintain its ability to transmit and receive radio waves. On the other hand, when the concentration of hydrogen sulfide is high, the resistance of an antenna pattern made of silver increases, making it more difficult for current to flow. Therefore, as the reaction progresses, the antenna pattern loses its ability to transmit and receive radio waves. In this way, an antenna pattern made of silver functions as both an antenna for transmitting and receiving data and a sensor for detecting the concentration of hydrogen sulfide.

[0040] In the antenna layer 16, the conductive fibers 161 are preferably metal fibers from the viewpoint of their ease of reaction with chemical substances, and are preferably in the form of nanowires from the viewpoint of their even greater ease of reaction with chemical substances. In this embodiment, an example will be described in which silver nanowires are used as the conductive fibers 161 that constitute the antenna layer 16.

[0041] Silver nanowires can be synthesized by the liquid-phase reduction of a silver salt (e.g., silver nitrate) in the presence of a polyol (e.g., ethylene glycol) and poly(vinylpyrrolidone). Mass production of uniformly sized silver nanowires can be achieved, for example, by following the methods described in Xia, Y. et al., Chem. Mater. (2002), 14, 4736-4745 and Xia, Y. et al., Nanoletters (2003) 3(7), 955-960.

[0042] There is no particular limitation on the means for producing silver nanowires, and known means such as a liquid phase method or a vapor phase method can be used. There is also no particular limitation on the specific production method, and known production methods can be used. For example, Adv. Mater., 2002, 14, 833-837; Chem. Mater., 2002, 14, 4736-4745, etc., can be used as references for producing silver nanowires. The method for producing an antenna 11 made of silver nanowires will be described later.

[0043] The resin portion 162 covers the conductive fibers 161 in order to prevent the conductive fibers 161 from falling off from the antenna layer 16 and to improve the durability and abrasion resistance of the antenna layer 16. There are no particular limitations on the material suitable for the resin portion 162, but for example, a polymer of a polymerizable compound, a plastic resin, or the like can be used.

[0044] Referring again to FIG. 5, the configuration of antenna 11 will be described. The adsorption layer 17 is a layer capable of adsorbing hydrogen sulfide. The adsorption layer 17 is provided on the front side (Z1 side) of the first base material 15. For example, acrylic resin, urethane resin, silicone resin, etc. can be used as the adsorption layer 17. As will be described later, by appropriately setting the adsorption performance of the adsorption layer 17 for hydrogen sulfide, the reaction rate between the antenna portion 110 (silver nanowires) and hydrogen sulfide can be controlled.

[0045] For example, by setting the hydrogen sulfide adsorption capacity of the adsorption layer 17 high, the reaction rate between the silver nanowires and hydrogen sulfide can be slowed. By setting the hydrogen sulfide adsorption capacity of the adsorption layer 17 high in this way, the gradual accumulation of hydrogen sulfide in the antenna layer 16 is suppressed when the hydrogen sulfide concentration is low. This makes it possible to suppress the problem of the hydrogen sulfide accumulated in the antenna layer 16 reacting with the silver nanowires. On the other hand, by setting the hydrogen sulfide adsorption capacity of the adsorption layer 17 low, the reaction rate between the silver nanowires and hydrogen sulfide can be increased. By setting the hydrogen sulfide adsorption capacity of the adsorption layer 17 low in this way, the reaction between the silver nanowires and hydrogen sulfide can be made to proceed linearly, thereby enabling faster detection of an abnormality when the hydrogen sulfide concentration suddenly increases.

[0046] The adhesive layer 18 is a layer that bonds the antenna layer 16 and the second substrate 19. The adhesive layer 18 is provided on the back side (Z2 side) of the antenna layer 16. The adhesive layer 18 may be made of any material that is impermeable to or has low permeability to hydrogen sulfide, and may be appropriately selected from various known materials and materials that exhibit adhesive strength. By selecting such a material, the adhesive layer 18 can suppress the reaction between hydrogen sulfide that has permeated from the back side (Z2 side) of the sensor 10 and the silver nanowires of the antenna layer 16. For example, acrylic, rubber, silicone, etc. may be used for the adhesive layer 18. Note that the adhesive layer 18 is necessary when the antenna layer 16 is patterned by punching, but may be omitted when the antenna layer 16 is patterned by laser etching.

[0047] The second substrate 19 is a member that serves as the base of the antenna 11. The second substrate 19 is provided on the back side (Z2 side) of the adhesive layer 18. The second substrate 19 is made of a material that is impermeable to or has low permeability to hydrogen sulfide. By selecting such a material, the second substrate 19 can suppress a reaction between hydrogen sulfide that has permeated from the back side (Z2 side) of the sensor 10 and the silver nanowires of the antenna layer 16. For example, polyethylene terephthalate (PET), polycarbonate (PC), etc. can be used as the second substrate 19. In this embodiment, the adhesive layer 18 and the second substrate 19 function as a protective layer that suppresses a reaction between hydrogen sulfide and the silver nanowires. The antenna 11 and the communication unit 12 are attached to the sensor plate 130 via an adhesive layer (not shown) provided on the back side (Z2 side) of the second substrate 19.

[0048] Next, we will explain the function of the adsorption layer 17 provided on the front side (Z1 side) of the antenna 11. Fig. 7A is a diagram illustrating the state of the adsorption layer 17 when the concentration of hydrogen sulfide is low. Fig. 7B is a diagram illustrating the state of the adsorption layer 17 when the concentration of hydrogen sulfide is high. As shown in FIG. 7A, when the concentration of hydrogen sulfide is low, most of the hydrogen sulfide (molecules M) is adsorbed by the adsorption layer 17, and therefore, the hydrogen sulfide hardly reaches the antenna layer 16. As such, when the concentration of hydrogen sulfide is low, the silver nanowires contained in the antenna layer 16 hardly react with hydrogen sulfide, and the conductivity of the antenna layer 16 does not decrease, so the radio wave transmission and reception function is not impaired. Therefore, when the sensor 10 receives a response request signal from the relay device 20, it can transmit a response signal (identification number) to the relay device 20. As such, when the administrator receives response signals from each sensor 10 after transmitting the response request signal, the administrator can determine that the concentration of hydrogen sulfide is low (i.e., the impact on the human body is small) around each sensor 10 that received the response signal.

[0049] On the other hand, as shown in FIG. 7B, when the concentration of hydrogen sulfide is high, the inside of the adsorption layer 17 becomes saturated with the adsorbed hydrogen sulfide, and the hydrogen sulfide that cannot be adsorbed penetrates the first substrate 15 and reaches the antenna layer 16. As a result, the silver nanowires contained in the antenna layer 16 react with the hydrogen sulfide, reducing their conductivity and causing a loss of their ability to transmit and receive radio waves. Therefore, even if a response request signal is transmitted from the relay device 20, the sensor 10 cannot receive the response request signal or transmit a response signal (identification number) to the relay device 20. In this way, if there is a sensor 10 that has transmitted a response request signal but has not received a response signal, the administrator can determine that the concentration of hydrogen sulfide is high (highly harmful to the human body) around the corresponding sensor 10.

[0050] Next, a method for manufacturing the antenna 11 will be described. The method for manufacturing the antenna 11 described below is one example, and the antenna 11 can also be manufactured by other manufacturing methods. Figures 8 and 9 are schematic diagrams showing manufacturing steps (A) to (D) of the antenna 11. 8(A), a conductive fiber-containing composition containing conductive fibers 161 and a dispersion medium is applied to the first surface 15A of the first substrate 15 and dried to arrange a plurality of conductive fibers 161 on the first surface 15A of the first substrate 15. The conductive fiber-containing composition may contain a resin component made of a thermoplastic resin or a polymerizable compound in addition to the conductive fibers 161 and the dispersion medium.

[0051] After arranging a plurality of conductive fibers 161 on the first surface 15A of the first substrate 15, a composition for a light-transmitting resin containing a polymerizable compound and a solvent is applied and dried to form a coating film 160 of the composition for a light-transmitting resin, as shown in Fig. 8(B). The composition for a light-transmitting resin contains a polymerizable compound and a solvent, and may also contain a polymerization initiator or a reaction inhibitor, if necessary.

[0052] 9(C), the coating film 160 is irradiated with ionizing radiation I such as ultraviolet light to polymerize (crosslink) the polymerizable compound, thereby hardening the coating film 160 and forming a resin portion 162. As a result, the antenna layer 16 is formed on the first surface 15A of the first substrate 15. Furthermore, the antenna layer 16 is patterned by a method such as laser etching or punching to form an antenna pattern. 9(D), an adsorption layer 17 is formed on the second surface 15B of the first substrate 15. A laminate of an adhesive layer 18 and a second substrate 19 is attached to the surface opposite to the first substrate 15, thereby obtaining a sheet-like antenna 11.

[0053] Next, an overview of the process of monitoring the concentration of hydrogen sulfide in the gas monitoring system 1 including the sensor system of this embodiment will be described with reference to Fig. 10. Fig. 10 is a flowchart showing the procedure of the process of monitoring the concentration of hydrogen sulfide by the gas monitoring system 1. It should be noted that the process of the flowchart shown in Fig. 10 is executed at predetermined time intervals.

[0054] In step S11 shown in FIG. 10, the management server 30 transmits a response request signal to each sensor 10 via the relay device 20 or the like. In step S12, each sensor 10 that has received the response request signal transmits its own identification number as a response signal to the relay device 20 via the antenna 11. The response signal from the sensor 10 is transmitted to the management server 30 via the relay device 20 or the like. If the concentration of hydrogen sulfide is low, the antenna 11 of each sensor 10 maintains its ability to transmit and receive radio waves, and therefore the response signal from each sensor 10 is transmitted to the management server 30 via the relay device 20 or the like. On the other hand, if the concentration of hydrogen sulfide increases and the antenna 11 of any sensor 10 loses its ability to transmit and receive radio waves, the response signal from that sensor 10 will not be transmitted to the relay device 20.

[0055] In step S13, the management server 30 updates the sensor management table (see FIG. 4) based on the received response signal. In step S14, the management server 30 refers to the updated sensor management table and determines whether there are any sensors 10 from which a response signal has not been received. If the determination in step S14 is NO, the process of this flowchart ends. On the other hand, if the determination in step S14 is YES, the process proceeds to step S15. In step S15, the management server 30 notifies the administrator of the identification number of the sensor 10 from which the response signal has not been received, along with message data indicating the occurrence of an abnormality, and ends the processing of this flowchart.

[0056] The sensor 10 and gas monitoring system 1 of the present embodiment described above provide the following advantages, for example. The sensor 10 of this embodiment includes an antenna 11 that loses its ability to transmit and receive radio waves when it reacts with chemical substances in the environment, and a communication unit 12 that transmits and receives signals to and from the relay device 20 via the antenna 11. According to this configuration, when the concentration of chemical substances is high, the antenna 11 loses its ability to transmit and receive radio waves when it reacts with the chemical substances, and is therefore unable to receive a response request signal from or transmit a response signal to the relay device 20. Therefore, the administrator can determine the concentration of chemical substances in the environment based on the presence or absence of a response signal from the sensor 10.

[0057] In the sensor 10 of this embodiment, the antenna unit 110 (antenna 11) is formed of a metal antenna pattern, and therefore can be manufactured relatively inexpensively compared to sensors that measure the concentrations of hydrogen sulfide, oxygen, etc. using electrical or chemical methods. Therefore, even if a large number of sensors 10 are installed within a facility, the cost burden can be reduced. Furthermore, since the sensor 10 can be used while remaining installed within the facility, the concentration of chemical substances can be monitored at all times, day or night. Moreover, monitoring chemical substances does not require much effort or time, and there is no need to have workers waiting within or near the facility. Therefore, the sensor 10 of this embodiment and the gas monitoring system 1 including the sensor 10 can monitor the concentrations of chemical substances in the environment at low cost and continuously in an unmanned manner.

[0058] The sensor 10 of this embodiment uses silver as the metal constituting the antenna unit 110 (antenna 11), and is therefore suitable for monitoring the concentration of hydrogen sulfide, which easily reacts with silver. Furthermore, because the silver constituting the antenna unit 110 has a nanowire shape, the surface area of ​​the antenna unit 110 can be increased compared to when the antenna unit 110 is formed from silver paste, for example. Therefore, the antenna unit 110 of this embodiment can more quickly react with hydrogen sulfide when the concentration of hydrogen sulfide increases.

[0059] In the sensor 10 of this embodiment, the antenna 11 includes the adsorption layer 17 capable of adsorbing hydrogen sulfide, and the reaction rate between the antenna 11 and hydrogen sulfide can be slowed or accelerated by appropriately setting the adsorption performance of the adsorption layer 17. In this way, the sensor 10 of this embodiment can optimize its detection sensitivity for chemical substances such as hydrogen sulfide depending on the location and purpose of use.

[0060] The gas monitoring system 1 of this embodiment is equipped with a relay device 20 that transmits and receives radio waves to and from each sensor 10, so even if multiple sensors 10 are installed within a facility, these multiple sensors 10 can be managed centrally.

[0061] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and variations, such as those described below, are possible, and are also within the technical scope of the present invention. Furthermore, the effects described in the embodiments are merely a list of the most preferable effects resulting from the present invention, and are not limited to those described in the embodiments. Note that the above-described embodiments and the modifications described below can also be used in appropriate combinations, but detailed description thereof will be omitted.

[0062] (Variations) In the embodiment, an example has been described in which silver is used as the metal whose conductivity decreases upon reaction with hydrogen sulfide, but this is not limiting. For example, copper, copper alloy, aluminum bronze, etc. may also be used as the metal whose conductivity decreases upon reaction with hydrogen sulfide. Furthermore, in the embodiment, an example has been described in which the antenna portion 110 (see FIG. 4) of the antenna layer 16 is made of silver nanowires, but this is not limiting. The antenna layer 16 may be patterned using silver paste or nanoparticles.

[0063] In the embodiment, the adsorption layer 17 is provided on the front side (Z1 side) of the first base material 15, but the present invention is not limited to this. Instead of the adsorption layer 17, a permeable layer capable of adjusting the permeability of hydrogen sulfide may be provided, or the adsorption layer 17 and the permeable layer may be laminated together.

[0064] In the sensor 10 of the embodiment, the first substrate 15, the antenna layer 16, the adsorption layer 17, etc. may be made optically transparent. With this configuration, it becomes possible to visually check the state of the antenna part 110 (antenna 11) that has turned black due to a reaction with hydrogen sulfide. In the sensor 10 of the embodiment, by appropriately selecting the material of the sensor plate 130 (see FIG. 3), it is possible to impart flexibility to the sensor 10. By imparting flexibility to the sensor 10, it is possible to stably attach the sensor 10 to, for example, a convex or concave surface.

[0065] In the sensor 10 of the embodiment, the power source for communication may be provided externally. For example, a power line may be laid inside the sewer tunnel, and each sensor 10 may be individually connected to the power line with a dedicated cable. Alternatively, the sensor 10 may be a passive type, and the power supply radio waves received by the antenna 11 may be converted into electric power.

[0066] In the gas monitoring system 1 of the embodiment, an example has been described in which the relay device 20 is an external device, but this is not limiting. The external device may be a terminal device (e.g., a laptop computer, a tablet terminal, etc.) held by the worker while the worker is waiting within a distance where radio waves can be transmitted and received between the worker and the sensor 10. In this case, if the worker manages data related to the sensor 10 using only the terminal device, the relay device 20, management server 30, and communication network 40 may be omitted.

[0067] In the gas monitoring system 1 of the embodiment, communication between the antenna 11 and the relay device 20 is not limited to transmitting and receiving data using radio waves conforming to LPWA, but may also transmit and receive data using radio waves conforming to short-range communication standards such as Wi-Fi (registered trademark), Bluetooth (registered trademark), ZigBee (registered trademark), etc. In this way, data may be transmitted and received between the antenna 11 and the relay device 20 using any type of radio waves as long as wireless communication is possible.

[0068] In the embodiment, an example has been described in which the gas monitoring system 1 is applied to a system that monitors the concentration of hydrogen sulfide generated in a sewer tunnel, but the application is not limited thereto. The gas monitoring system 1 can also be applied to systems that monitor the concentration of chemical substances in facilities such as sewage / sludge treatment facilities, industrial waste treatment facilities, incineration plants, food processing plants, underground trenches, tunnels, pits, shafts, manholes, mines, and coal mines. Furthermore, in the embodiment, an example has been described in which the gas monitoring system 1 is used to monitor the concentration of hydrogen sulfide, but the application is not limited thereto. For example, if the antenna unit 110 is made of aluminum, its conductivity changes due to chlorine, etc., so that the concentration of hydrogen chloride can also be monitored. [Explanation of symbols]

[0069] 1 Gas monitoring system 10(10a~10c) Sensor 11 Antenna 12 Communications Department 13 Batteries 15 First base material 16 Antenna Layer 17 Adsorption layer 18 Adhesive layer 19 Second base material 20 Relay device 30 Management Server 110 Antenna section 161 Conductive Fiber 162 Resin part

Claims

1. Antennas that lose their ability to send and receive radio waves when they react with chemicals in the environment, a communication unit that transmits and receives signals to and from an external device via the antenna; Equipped with the antenna has an antenna portion having an antenna pattern formed by a single antenna layer in which a plurality of conductive fibers each having a nanowire shape are arranged, The sensor has an antenna portion that reacts with the chemical substance.

2. 2. The sensor of claim 1, The antenna is formed of a metal whose conductivity changes by reacting with chemicals in the environment. Sensor.

3. 3. The sensor according to claim 2, The metal is silver. Sensor.

4. The sensor according to any one of claims 1 to 3, The antenna is a substrate that is permeable to the chemical substance; an adsorption layer provided on the front side of the substrate and adsorbing the chemical substance; The antenna portion is provided on the back side of the base material, a reaction rate between the antenna part and the chemical substance differs depending on the adsorption performance of the adsorption layer for the chemical substance; Sensor.

5. A sensor according to any one of claims 1 to 4; an external device that transmits and receives radio waves to and from the sensor; A sensor system comprising:

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