A humidity sensing film and its application in a fiber probe manufacturing process

Abstract

The application belongs to the field of optical fiber sensing, and particularly relates to a kind of optical fiber probe preparation process and its application humidity sensing film.The application has low cost, corrosion resistance, and is not affected by electromagnetic interference.A kind of optical fiber probe preparation process provided by the application comprises an optical fiber head, the optical fiber head comprises a core layer and a cladding layer, the cladding layer is coated outside the core layer, and a coating layer is further arranged outside the cladding layer of the optical fiber head.A kind of humidity sensing film is further provided by the application, comprising an epoxy resin film and an optical fiber;the optical fiber is arranged on the epoxy resin film, and a plurality of light humidity sensors are arranged on the optical fiber.The application can make the cylindrical optical fiber head uniformly heated by using the photo-thermal and photo-pressure effects of laser, thereby obtaining uniform coating effect on the side surface of the optical fiber sensing structure.The uniform coating effect can effectively guarantee the sensitivity of the optical fiber probe.The uniform coating effect of the process has extremely high repeatability, which lays a good foundation for industrial production, and reduces the rate of defective products after mass production.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic sensing, specifically relating to a fiber optic probe fabrication process and its application in a humidity sensing film. Background Technology

[0002] Existing humidity-sensitive elements mainly fall into two categories: resistors and capacitors. Resistors are characterized by a film made of a moisture-sensitive material coated on a substrate. When water vapor in the air is adsorbed onto the moisture-sensitive film, the resistivity and resistance of the element change, allowing for humidity measurement. Capacitors, on the other hand, are generally made of polymer film capacitors. Commonly used polymer materials include polystyrene, polyimide, and cellulose acetate butyrate. When the ambient humidity changes, the dielectric constant of the humidity-sensitive capacitor changes, causing its capacitance to change as well. The change in capacitance is directly proportional to the relative humidity.

[0003] Existing humidity sensors, whether resistive or capacitive, generally suffer from poor corrosion resistance, susceptibility to electromagnetic interference, and high cost. This is especially problematic in fields with high precision requirements, such as aircraft piping systems, where the environment is harsh and complex, demanding comprehensive pipeline monitoring with extremely high accuracy and sensitivity – requirements that traditional humidity sensors struggle to meet. Summary of the Invention

[0004] The present invention provides a fiber optic probe fabrication process and a humidity sensing film for its application, which can effectively solve the problems existing in the prior art, and is low in cost, corrosion resistant, and unaffected by electromagnetic interference.

[0005] This invention provides a fiber optic probe fabrication process, including a fiber optic head. The fiber optic head includes a core layer and a cladding layer, with the cladding layer covering the core layer. A coating layer is also provided outside the cladding layer of the fiber optic head. The preparation of the coating layer includes the following steps:

[0006] A1: Add 0.3-0.6g of polyvinyl alcohol to 10ml of graphene oxide dispersion and mix and stir to form a film-forming coating;

[0007] A2: Immerse the fiber head in the film-forming coating, and keep the temperature of the film-forming coating at 70-90℃;

[0008] A3: Inject 20mW-40mW of laser into the fiber head and continue for 30-45 minutes to coat the fiber head surface with film-forming coating to form a coating layer.

[0009] A4: Dry the coating layer on the fiber optic head.

[0010] As a further optimization of this method, step A4 involves natural drying at room temperature.

[0011] As a further optimization of this method, the drying time for step A4 is 48-72 hours.

[0012] The present invention also provides a humidity sensing film, comprising an epoxy resin film and an optical fiber; the optical fiber is disposed on the epoxy resin film, and a plurality of photosensitive humidity sensors are disposed on the optical fiber, the photosensitive humidity sensors being fabricated using the aforementioned optical fiber probe fabrication process.

[0013] As a further optimization of the present invention, a capacitive humidity sensor is also provided on the optical fiber, and the capacitive humidity sensor and the photosensitive humidity sensor are alternately distributed on the optical fiber.

[0014] As a further optimization of the present invention, the preparation of the epoxy resin film includes the following steps:

[0015] B1: Add 100g of epoxy resin and 25-60g of alumina powder to 5-10g of reactive diluent and stir evenly;

[0016] B2: Add 25-40g of epoxy resin curing agent to the mixture of B1 and mix well;

[0017] B3: The mixture of B2 is poured into a mold and left to stand to form an epoxy resin film.

[0018] As a further optimization of the present invention, the epoxy resin is selected from any one of the E51, E44, and E42 types.

[0019] As a further optimization of the present invention, the active diluent is selected from one or a mixture of two of n-butyl glycidyl ether, cresol glycidyl ether, and butanediol diglycidyl ether.

[0020] As a further optimization of the present invention, the epoxy resin curing agent is selected from one or a mixture of two of the following: 593 curing agent, T31 curing agent, and polyetheramine curing agent.

[0021] As a further optimization of the present invention, the settling environment in step B3 is 40°C and the settling time is 8 hours.

[0022] As a further optimization of the present invention, step B3 also includes the step of pre-embedding the optical fiber in the mold.

[0023] This invention has at least the following beneficial effects:

[0024] 1. By utilizing the photothermal and photopressure effects of lasers, the cylindrical fiber optic tip can be heated uniformly, resulting in a uniform coating effect on the side surface of the fiber optic sensing structure. This uniform coating effectively ensures the sensitivity of the fiber optic probe.

[0025] 2. This process produces a uniform coating effect and has extremely high repeatability, laying a solid foundation for industrial mass production and reducing the defect rate after mass production.

[0026] 3. The coating equipment used in this coating process is simple, the raw materials are inexpensive, and the process is simple, which can significantly reduce the production cost of industrial mass production.

[0027] 4. This humidity sensor has a short humidity response time and is highly sensitive, enabling it to quickly provide early warning of liquid leakage. It also has advantages such as corrosion resistance and no electromagnetic interference.

[0028] 5. This coating process uses polymer doping, which can improve the flexibility of the sensor, meet the needs of complex working conditions, and enable it to be used even with defects. Attached Figure Description

[0029] Figure 1 This is the flowchart of Example 1. Detailed Implementation

[0030] Example 1

[0031] Raw graphite is hydrophobic. After oxidation, numerous oxygen-containing groups, such as carboxyl, hydroxyl, and epoxy groups, form on the graphite surface, giving graphene oxide excellent hydrophilicity. Following ultrasonic oscillation, it can be dispersed into graphene oxide. The polar groups also increase the compatibility of graphene oxide with certain polar polymers. Stably dispersed graphene oxide can be mixed with polymer materials via solution methods to prepare nanocomposites with excellent electrical and mechanical properties, making graphene oxide an excellent reinforcing filler for nanocomposites. Due to the excellent properties of graphene oxide, its reinforcing effect on the mechanical and thermal properties of polymer materials is superior to other inorganic reinforcing fillers, while requiring less addition to the polymer matrix than traditional reinforcing fillers. Furthermore, graphene oxide exhibits excellent photoresponsiveness, characterized by high sensitivity, fast response speed, and good repeatability.

[0032] Polyvinyl alcohol (PVA) is a hydrophilic, biodegradable polymer and an excellent membrane material. Containing numerous hydrophilic groups, PVA exhibits excellent hydrophilicity and film-forming properties. It is a linear polymer molecule that can form a large molecular network structure through crosslinking. Intermolecular interactions, such as hydrogen bonds, enhance the thermal stability of PVA.

[0033] This embodiment provides a fiber optic probe fabrication process that fully utilizes the properties of graphene oxide and polyvinyl alcohol to create a film-forming coating. This coating is then applied to the surface of the fiber optic head using a photopolymerization method. When the coating is affected by ambient humidity, the refractive index of the optical path within the fiber changes, thus achieving humidity detection. The fiber optic head refers to a short segment of optical fiber, comprising a core and a cladding. The cladding covers the core, and a coating layer is also provided outside the cladding. The fabrication of this coating layer includes the following steps:

[0034] S1: Add 0.3-0.6g of polyvinyl alcohol to 10ml of graphene oxide dispersion (concentration of 1mg / ml-1.5mg / ml) and mix and stir to form a film coating. In this embodiment, magnetic stirring is used.

[0035] A2: Immerse the fiber optic head in the film-forming coating. Before immersion, the fiber optic head should also be cleaned with alcohol.

[0036] A2: The film-forming coating is deposited on the surface of the fiber optic head using a photopolymerization method. Specifically, a laser with a power of 20mW-40mW is injected into the fiber optic head using a laser source. During the injection process, an optical power meter is used to monitor the laser power to ensure its stability. The injection time is maintained at 30-45 minutes, and the temperature of the film-forming coating is maintained at 70-80℃ during the coating process.

[0037] This process utilizes lasers to generate photopressure and photothermal effects, adsorbing the molecules of the film-forming coating onto the side surface of the sensing structure.

[0038] A3: Dry the coating on the fiber optic head. Drying refers to the process of removing solvents while retaining solid content. Drying can be done by heating or natural drying. In this embodiment, natural drying at room temperature for 48-72 hours is used.

[0039] The coating principle of this embodiment is as follows:

[0040] When a laser of a certain power passes through the fiber optic head, the laser is coupled into the cladding of the fiber optic head, generating a large amount of heat at the cladding. Simultaneously, photopressure is generated on the side surface of the fiber optic head. During light transmission, the fiber optic head is immersed in a film-forming coating. The photopressure and photothermal effects generated by the laser cause the molecules of the material to be coated to be adsorbed onto the side surface of the fiber optic sensing structure, achieving a uniform coating effect. The uniformity of the coating actually affects the accuracy of the sensing, because the more uniform the film, the higher the sensing accuracy.

[0041] Therefore, the combination of film-forming coating and optical fiber in this embodiment can greatly improve humidity sensitivity and sensing efficiency.

[0042] Example 2

[0043] This embodiment provides a humidity-sensing film based on Embodiment 2, comprising an epoxy resin film and an optical fiber. The optical fiber is disposed on the epoxy resin film; specifically, the optical fiber can be densely distributed in a wavy pattern, and several photosensitive humidity sensors are disposed on the optical fiber. The photosensitive humidity sensors are prepared using the above-described coating process.

[0044] The preparation of the epoxy resin film includes the following steps:

[0045] B1: Add 100g of epoxy resin and 25-60g of alumina powder to 5-10g of reactive diluent and stir evenly. A mixer can be used for stirring. The epoxy resin can be any one of E51, E44, or E42 types; the reactive diluent can be one or a mixture of two of n-butyl glycidyl ether, cresol glycidyl ether, and butanediol diglycidyl ether.

[0046] B2: Add 25-40g of epoxy resin curing agent to the mixture in B1 and mix thoroughly. The epoxy resin curing agent can be one or a mixture of two of the following: 593 curing agent, T31 curing agent, and polyetheramine curing agent.

[0047] B3: The mixture of B2 is introduced into a mold and left to stand to form an epoxy resin film. Specifically, after the mixture of B2 is introduced into the mold, it is left to stand at 40°C for 8 hours to form an epoxy resin film. This step also includes embedding an optical fiber in the mold. After cooling, the optical fiber containing the photosensitive humidity sensor and the epoxy resin film form a whole, becoming a humidity-sensing film.

[0048] Preferably, a capacitive humidity sensor is also provided on the optical fiber, with the capacitive humidity sensor and the photosensitive humidity sensor alternately distributed on the optical fiber. Using the B3 fabrication process, the optical fiber containing the photosensitive humidity sensor and the capacitive humidity sensor ultimately forms a humidity-sensing film with the epoxy resin film.

[0049] The principle of a light-sensitive humidity sensor is that when the air humidity changes, the refractive index of the sensor changes, thus modulating the light. The change in the output light signal can then characterize the humidity change. The principle of a capacitive sensor is that when the humidity changes, the dielectric constant of the capacitor changes, thus sensing the humidity change through a change in the output electrical signal. Alternating between these two types of sensors can significantly shorten the response time and improve the accuracy of locating humidity changes.

[0050] This embodiment is applied to aircraft piping systems, employing distributed multi-point monitoring with no blind spots, providing complete and comprehensive coverage of the entire aircraft piping system and accurately locating leak points. This embodiment boasts high sensitivity, achieving high-precision identification and early warning of pipeline system leaks based on the temperature difference effect.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A humidity-sensing film, comprising an optical fiber head, the optical fiber head including a core layer and a cladding layer, the cladding layer covering the core layer, characterized in that, The cladding of the optical fiber head is further coated with a coating layer, and the preparation of the coating layer includes the following steps: A1: Add 0.3-0.6g of polyvinyl alcohol to 10ml of graphene oxide dispersion and mix and stir to form a film-forming coating; A2: Immerse the fiber head in the film-forming coating, and keep the temperature of the film-forming coating at 70-90℃; A3: Inject 20mW-40mW of laser into the fiber head and continue for 30-45 minutes to coat the fiber head surface with film-forming coating to form a coating layer. A4: Dry the coating layer on the fiber optic head; It also includes an epoxy resin film and optical fiber; the optical fiber is placed on the epoxy resin film, and several optical fiber heads are provided on the optical fiber as photosensitive humidity sensors. The optical fiber is also equipped with a capacitive humidity sensor, and the capacitive humidity sensor and the photosensitive humidity sensor are alternately distributed on the optical fiber.

2. The humidity-sensing film according to claim 1, characterized in that, Step A4 involves air drying at room temperature for 48-72 hours.

3. The humidity-sensing film according to claim 1, characterized in that, The preparation of epoxy resin film includes the following steps: B1: Add 100g of epoxy resin and 25-60g of alumina powder to 5-10g of reactive diluent and stir evenly; B2: Add 25-40g of epoxy resin curing agent to the mixture of B1 and mix well; B3: The mixture of B2 is poured into a mold and left to stand to form an epoxy resin film.

4. A humidity-sensing film according to claim 3, characterized in that, The epoxy resin can be any one of the E51, E44, or E42 types.

5. A humidity-sensing film according to claim 3, characterized in that, The active diluent is selected from one or a mixture of two of the following: n-butyl glycidyl ether, cresol glycidyl ether, and butanediol diglycidyl ether.

6. A humidity-sensing film according to claim 3, characterized in that, The epoxy resin curing agent is selected from one or a mixture of two of the following: 593 curing agent, T31 curing agent, and polyetheramine curing agent.

7. A humidity-sensing film according to claim 3, characterized in that, The settling environment in step B3 is 40℃, and the settling time is 8 hours.

8. A humidity-sensing film according to claim 3, characterized in that, Step B3 also includes the step of pre-embedding the optical fiber in the mold.

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