Piezoelectric mechanoluminescence self-energized optical fiber pressure sensor and preparation method thereof

Abstract

The invention discloses a piezoelectric type mechanoluminescence self-energized optical fiber pressure sensor and a preparation method thereof. The sensor comprises a coupling optical fiber, a sensing layer and a pressure-resistant protection layer, the coupling optical fiber comprises a fiber core and a cladding and is used for guiding a fluorescence signal, the cladding wraps the fiber core, and the fiber core is made of a hard polymer; one end of the coupling optical fiber is of a conical structure; the sensing layer wraps the outer side of the conical structure of the coupling optical fiber, the sensing layer comprises a piezoelectric type mechanoluminescent material and a piezoelectric type polymer, and the piezoelectric type mechanoluminescent material is dispersed in the piezoelectric type polymer; and the pressure-resistant protective layer wraps the outer layer of the sensing layer and is a hard polymer. The optical fiber sensor prepared by compounding the piezoelectric mechanoluminescent material and the piezoelectric polymer realizes self-energized sensing, can stably operate under a large pressure detection condition, realizes an in-situ real-time pressure sensing function, and has important application value in the fields of scientific research, industrial production, building safety and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of fiber optic pressure sensing, and particularly relates to a piezoelectric force-induced luminescence self-powered fiber optic pressure sensor and a preparation method thereof. Background Art

[0002] Pressure sensors have important application values in the fields of scientific research, industrial production, building safety, traffic safety, etc. Fiber optic-based pressure sensors have advantages such as anti-electromagnetic interference, in-situ monitoring, and high sensitivity, and have become important devices for safety accident prevention and equipment fault diagnosis. However, existing fiber optic pressure sensors require additional external power supply devices, resulting in complex systems and high costs. Fiber optic sensors based on the composite of piezoelectric force-induced luminescence materials can achieve self-power supply, effectively solve the above problems, and have the advantages of high sensitivity, self-power supply, and pressure resistance.

[0003] In previous research on the combination of force-induced luminescence materials and optical fibers (Adv. Intell. Syst., 5: 2300113, Adv. Intell. Syst., 3: 2100035, Chinese invention patent: CN202011023913.7), flexible force-induced luminescence optical fibers prepared by compounding force-induced luminescence materials with elastomeric materials, based on the triboelectric force-induced luminescence principle, integrating the functions of sensing and transmission, can achieve axial tensile strain sensing. However, when pressure acts on the optical fiber, the elastomeric material optical fiber deforms severely, resulting in the failure of the sensing and light guiding functions. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a piezoelectric force-induced luminescence self-powered fiber optic pressure sensor and a preparation method thereof. The present invention combines a piezoelectric force-induced luminescence material with a piezoelectric polymer, and under the protection of a hard polymer pressure-resistant protective layer, high-sensitivity, self-powered, stable and reliable pressure sensing is achieved.

[0005] Different from the existing triboelectric force-induced luminescence principle, the optical fiber of the present invention is based on a piezoelectric force-induced luminescence material, compounded with a piezoelectric polymer substrate, and under the protection of a hard polymer epoxy resin pressure-resistant protective layer, has small deformation under pressure, emits fluorescence, and at the same time the structure remains stable, and can perceive pressure stably for a long time; the optical fiber structure is different, and one end of the optical fiber is a tapered structure, with higher fluorescence coupling efficiency.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] The present invention provides a piezoelectric force-induced luminescence self-powered fiber optic pressure sensor, including: a coupling optical fiber 1, a sensing layer 2, and a pressure-resistant protective layer 3;

[0008] The coupling optical fiber 1 includes a core 1-1 and a cladding 1-2. The cladding 1-2 wraps around the core 1-1, and the core 1-1 is a rigid polymer. One end of the coupling optical fiber 1 is a tapered structure 1-3, which is used to receive and guide fluorescence and effectively couple the force-induced fluorescence generated by the sensing layer.

[0009] The sensing layer 2 wraps around the outside of the tapered structure 1-3 of the coupling optical fiber 1. The sensing layer 2 includes a piezoelectric force-induced luminescence material and a piezoelectric polymer, and the piezoelectric force-induced luminescence material is dispersed in the piezoelectric polymer. Under an external force, corresponding intensity of force-induced fluorescence is generated, and the luminescence intensity can be restored and is linearly related to the magnitude of the pressure. The force-induced fluorescence is collected by the coupling optical fiber and transmitted along the optical fiber to the distal end for detection and demodulation.

[0010] The pressure-resistant protective layer 3 wraps around the outside of the sensing layer 2. The pressure-resistant protective layer 3 is a rigid polymer, which can withstand pressure without obvious deformation and is used to protect the device safety of the sensor under pressure conditions.

[0011] Preferably, the refractive indices of the core 1-1 and the cladding 1-2 of the coupling optical fiber 1 satisfy the total reflection condition. The fluorescence transmitted in the coupling optical fiber is transmitted at the core-cladding interface in the form of total internal reflection.

[0012] Further preferably, the refractive index of the material of the cladding 1-2 is lower than that of the material of the core 1-1.

[0013] Preferably, the rigid polymers of the core 1-1 and the pressure-resistant protective layer 3 are epoxy resin and polymethyl methacrylate.

[0014] Preferably, the cladding 1-2 is a polymer, and the polymer is epoxy resin, polymethyl methacrylate, polyvinylidene fluoride, polysiloxane or silicone rubber.

[0015] Preferably, the coupling optical fiber 1 is cylindrical.

[0016] Preferably, the mass fraction of the piezoelectric force-induced luminescence material in the sensing layer 2 is 25%-50%.

[0017] Preferably, the piezoelectric force-induced luminescence material is an oxide, sulfide, sulfur oxide, titanate, phosphate, aluminate, silicate, niobate doped with transition metal ions or rare earth ions, or methylammonium lead bromide perovskite, cesium lead bromide perovskite, tetraphenylethylene.

[0018] Preferably, the piezoelectric polymer of the sensing layer 2 is polyvinylidene fluoride, polyvinylidene fluoride-trifluoroethylene copolymer, polyamide, polylactic acid, epoxy resin, polymethyl methacrylate or polyvinylidene fluoride.

[0019] Preferably, the sensing layer 2 is cylindrical or film-shaped and coaxial with the coupling optical fiber 1.

[0020] Preferably, the pressure-resistant protective layer 3 is cylindrical or film-shaped and coaxial with the coupling optical fiber 1.

[0021] The present invention also provides a preparation method of the above piezoelectric type force-induced luminescence self-powered optical fiber pressure sensor, including the following steps:

[0022] Step 1: Prepare the core 1-1 by using the mold method. Fill the hard polymer precursor into the mold, then cure and take out to obtain the core 1-1.

[0023] Step 2: Uniformly coat a polymer outside the core 1-1 to obtain the cladding 1-2.

[0024] Step 3: Prepare the sensing layer. Mix the piezoelectric polymer and the piezoelectric type force-induced luminescence material evenly, and place them in a vacuum environment for degassing treatment; then prepare a sensing layer 2 with uniform size on the outside of the coupling optical fiber 1 by the spin coating method or the mold method.

[0025] Step 4: Prepare the pressure-resistant protective layer 3 by using the mold method. Inject the hard polymer precursor into the mold, and coaxially insert the coupling optical fiber 1 containing the sensing layer 2 into the mold, and carry out thermal curing at 60 °C - 120 °C for 1 - 4 hours to form the pressure-resistant protective layer 3, and then take out the obtained piezoelectric type force-induced luminescence self-powered optical fiber pressure sensor.

[0026] Preferably, the mold in Step 1 is a cylindrical mold with a conical structure at one end.

[0027] The beneficial effects of the present invention are as follows:

[0028] The present invention provides a highly sensitive, self-powered, stable and reliable optical fiber pressure sensor, which realizes the effective perception of pressure based on the combination of the piezoelectric type force-induced luminescence material and the polymer optical fiber. Description of the Drawings

[0029] Figure 1 is a schematic structural diagram of the conical end piezoelectric type force-induced luminescence self-powered optical fiber pressure sensor in the embodiment of the present invention.

[0030] Figure 2 is a schematic structural diagram of the cylindrical mold used to prepare the core with a conical structure at one end in the embodiment of the present invention.

[0031] Figure 3 is a graph of the relationship between the stress and fluorescence intensity of the conical end piezoelectric type force-induced luminescence self-powered optical fiber in the embodiment of the present invention.

[0032] Figure 4 is a graph of the repeated experiment results of the conical end piezoelectric type force-induced luminescence self-powered optical fiber in the embodiment of the present invention.

[0033] Figure 5 It is a schematic structural diagram of a cylindrical - end piezoelectric type force - induced luminescence self - powered optical fiber pressure sensor in an embodiment of the present invention.

[0034] Figure 6 It is a schematic structural diagram of a cylindrical mold for preparing a cylindrical core in an embodiment of the present invention.

[0035] Figure 7 It is a relationship diagram of stress and fluorescence intensity of a cylindrical - end piezoelectric type force - induced luminescence self - powered optical fiber pressure sensor in an embodiment of the present invention.

[0036] Reference numerals in the figure: 1 - coupling optical fiber, 1 - 1 - core, 1 - 2 cladding, 1 - 3 tapered structure, 2 - sensing layer, 3 - pressure - resistant protective layer, 4 - cylindrical mold. Detailed implementation manners

[0037] The following further describes the specific implementation of the present invention in conjunction with the accompanying drawings and embodiments, but the implementation and protection of the present invention are not limited thereto. It should be noted that for the processes not specifically described in detail below, those skilled in the art can implement or understand them with reference to the prior art. The reagents or instruments without indicating the manufacturer are regarded as conventional products that can be obtained through commercial purchase.

[0038] Embodiment 1

[0039] A piezoelectric type force - induced luminescence self - powered optical fiber pressure sensor, as Figure 1 shown, includes: a coupling optical fiber 1, a sensing layer 2, and a pressure - resistant protective layer 3;

[0040] The coupling optical fiber 1 contains a core 1 - 1 and a cladding 1 - 2. The cladding 1 - 2 wraps around the core 1 - 1, and the core 1 - 1 is a hard polymer; one end of the coupling optical fiber 1 is a tapered structure 1 - 3, which is used to receive and guide fluorescence, and effectively couple the force - induced fluorescence generated by the sensing layer;

[0041] Specifically, the refractive indices of the core 1 - 1 and the cladding 1 - 2 of the coupling optical fiber 1 satisfy the total reflection condition. The fluorescence transmitted in the coupling optical fiber is transmitted in the form of total internal reflection at the core - cladding interface, and the refractive index of the cladding 1 - 2 material is lower than that of the core 1 - 1 material.

[0042] Specifically, the hard polymer of the core 1 - 1 is epoxy resin;

[0043] Specifically, the cladding 1 - 2 is a polymer, and the polymer is epoxy resin, polymethyl methacrylate, polyvinylidene fluoride, polysiloxane, polydimethylsiloxane, or silicone rubber.

[0044] Specifically, the coupling optical fiber 1 is cylindrical.

[0045] The sensing layer 2 is wrapped around the outer side of the tapered structure 1-3 of the coupling optical fiber 1. The sensing layer 2 contains a piezoelectric type force-induced luminescence material and a piezoelectric type polymer, and the piezoelectric type force-induced luminescence material is dispersed in the piezoelectric type polymer. Under the action of an external force, force-induced fluorescence of corresponding intensity is generated, and the luminescence intensity is recoverable and linearly related to the magnitude of the pressure. The force-induced fluorescence is collected by the coupling optical fiber and transmitted along the optical fiber to the distal end for detection and demodulation.

[0046] Specifically, the mass fraction of the piezoelectric type force-induced luminescence material in the sensing layer 2 is 25%-50%.

[0047] Specifically, the piezoelectric type force-induced luminescence material is an oxide, sulfide, sulfur oxide, titanate, phosphate, aluminate, silicate, niobate doped with transition metal ions or rare earth ions, or methylammonium lead bromide perovskite, cesium lead bromide perovskite, tetraphenylethylene.

[0048] Specifically, the piezoelectric polymer of the sensing layer 2 is polyvinylidene fluoride, polyvinylidene fluoride-trifluoroethylene copolymer, polyamide, polylactic acid, epoxy resin, polymethyl methacrylate or polyvinylidene fluoride.

[0049] Specifically, the sensing layer 2 is a cylindrical or thin film shape coaxial with the coupling optical fiber 1.

[0050] The pressure-resistant protective layer 3 is wrapped around the outer layer of the sensing layer 2. The pressure-resistant protective layer 3 is a hard polymer, which is used to protect the device safety of the sensor under pressure conditions.

[0051] Specifically, the pressure-resistant protective layer 3 is a cylindrical or thin film shape coaxial with the coupling optical fiber 1.

[0052] Specifically, the hard polymer of the pressure-resistant protective layer 3 is epoxy resin. The epoxy resin has good pressure resistance, which can avoid the deformation and damage of the device caused by pressure. The sensor has good repeatability and good pressure tolerance.

[0053] The preparation method of the above piezoelectric type force-induced luminescence self-powered optical fiber pressure sensor includes the following steps:

[0054] Step 1: Prepare the fiber core 1-1 by the mold method. Fill the hard polymer precursor into the mold, then cure and take it out to obtain the fiber core 1-1.

[0055] Step 2: Uniformly coat a polymer outside the fiber core 1-1 to obtain the cladding 1-2.

[0056] Step 3: Prepare the sensing layer. Mix the piezoelectric type polymer and the piezoelectric type force-induced luminescence material evenly, and place them in a vacuum environment for degassing treatment. Then, prepare a sensing layer 2 with uniform size on the outer side of the coupling optical fiber 1 by the spin coating method or the mold method.

[0057] Step 4: Prepare the pressure-resistant protective layer 3 by the mold method. Inject the hard polymer precursor into the mold, and coaxially insert the coupled optical fiber 1 with the sensing layer 2 into the mold. Perform thermal curing at 60°C - 120°C for 1 - 4 hours to form the pressure-resistant protective layer 3, and then take out the obtained piezoelectric force-induced luminescence self-powered optical fiber pressure sensor.

[0058] Specifically, the mold described in Step 1 is a cylindrical mold with a conical structure at one end.

[0059] Example 2

[0060] A preparation method of a piezoelectric force-induced luminescence self-powered optical fiber pressure sensor includes the following steps:

[0061] Step 1: Prepare the fiber core by the mold method. Fill the epoxy resin (specifix-40) precursor into a cylindrical mold with a conical structure at one end. The total length of the mold is 5 cm, the inner diameter is 380 μm, the length of the conical structure is 1 cm, and the inner diameter of the end is 200 μm. As Figure 2 shown, then cure and take out.

[0062] Step 2: Uniformly coat the polymer precursor outside the fiber core and then cure to obtain the cladding. The refractive index of the cladding material is lower than that of the fiber core material. In this example, the polymer is polydimethylsiloxane, and the cladding thickness is 120 μm.

[0063] Step 3: Prepare the sensing layer. First, prepare the sensing layer material. Mix the required mass of the piezoelectric polymer material and the piezoelectric force-induced luminescence material evenly. The mass fraction of the piezoelectric force-induced luminescence material is 25% - 50%. In this example, it is a mixture of polyvinylidene fluoride and ZnS:Mn 2+ prepared according to a mass ratio of 1:1 and placed in a vacuum environment for degassing treatment; then, on the outer side of the conical structure end of the coupled optical fiber, prepare a sensing layer with uniform dimensions by the spin coating method or the mold method. The sensing layer is wrapped on the outer side of the conical structure of the coupled optical fiber. The sensing layer is a cylindrical or film-shaped coaxial with the coupled optical fiber. In this example, the mold method is selected, and the sensing layer is a cylindrical coaxial with the coupled optical fiber, with an inner diameter of 760 μm and a length of 2 cm.

[0064] Step 4: Preparation of the pressure-resistant protective layer. By the mold method, inject the epoxy resin (specifix-40) precursor into the mold, and coaxially insert the coupled optical fiber with the sensing layer into the mold. The inner diameter of the mold is 1600 μm and the length is 2 cm. The pressure-resistant protective layer covers the sensing layer. Perform thermal curing at 80°C for 3 hours, and take out to obtain a piezoelectric force-induced luminescence self-powered optical fiber pressure sensor with a hard pressure-resistant protective layer.

[0065] The fluorescence spectra of the above pressure sensor under different pressure conditions are as Figure 3As shown in a of [reference], it can be seen that the relative fluorescence intensities under pressures of 1000 N and 1500 N are 22 and 53 respectively.

[0066] The relationship between pressure and luminescence fluorescence intensity is as Figure 3 shown in b of [reference]. It can be seen that the luminescence intensity increases with the increase of pressure, and the luminescence intensity is linearly correlated with the magnitude of pressure.

[0067] The results of multiple repeated experiments of the above pressure sensor under different pressure conditions are as Figure 4 shown. It can be seen that the luminescence intensity can be restored and has good repeat stability.

[0068] Example 3

[0069] The difference between this example and Example 2 lies in the different fiber optic structures. For comparison, the fiber optic end face is cylindrical and does not have a tapered structure, as Figure 5 shown, including: coupling optical fiber 1, sensing layer 2, and pressure-resistant protective layer 3. The coupling optical fiber 1 includes a core 1-1 and a cladding 1-2. The preparation process is as follows:

[0070] Step 1: Prepare the core by the mold method. Fill the epoxy resin (specifix-40) precursor into a cylindrical mold, as Figure 6 shown. The cylindrical mold is 5 cm long and has an inner diameter of 380 μm. Then cure it and take it out;

[0071] Step 2: Uniformly coat the polymer precursor outside the core and then cure it to obtain the cladding. The cladding material is polydimethylsiloxane, and its refractive index is lower than that of the core material. The thickness is 120 μm;

[0072] Step 3: Prepare the sensing layer. First, prepare the sensing layer material. Mix the required mass of ZnS:Mn 2+ and polyvinylidene fluoride in a mass ratio of 1:1, and place it in a vacuum environment for degassing treatment; then prepare a sensing layer with uniform size on the outside of one end of the coupling optical fiber by the spin coating method or the mold method. The sensing layer is wrapped outside the tapered structure of the coupling optical fiber. In this example, the mold method is selected. The sensing layer is a cylindrical shape coaxial with the coupling optical fiber, with an inner diameter of 760 μm and a length of 2 cm;

[0073] Step 4: Preparation of the pressure-resistant protective layer. Using the mold method, inject the epoxy resin (specifix-40) precursor into the mold, and coaxially insert the coupling optical fiber containing the sensing layer into the mold. The inner diameter of the mold is 1600 μm and the length is 2 cm. Carry out thermal curing at 80 °C for 3 hours. The pressure-resistant protective layer covers the sensing layer. After taking it out, a piezoelectric force-induced luminescence self-powered fiber optic pressure sensor with a hard pressure-resistant protective layer is obtained, as Figure 5 shown. Except for the different coupling optical fiber structures from Example 2, other parameters are the same.

[0074] A pressure test was carried out, and the relationship between different pressures and the fluorescence intensity is as Figure 7 shown. The relative fluorescence intensities under 1000 N and 1500 N pressures are 17 and 39 respectively. It can be seen that the fluorescence intensity of the cylindrical optical fiber structure is weak under the same conditions. The conical structure effectively improves the coupling efficiency, increases the fluorescence intensity, and is beneficial to pressure detection.

[0075] Therefore, a piezoelectric type force-induced luminescence self-powered optical fiber pressure sensor provided by the present invention can achieve self-power supply, high-sensitivity pressure sensing, has a simple preparation process, good repeatability, and low cost, and can be widely applied in industrial production, safety detection and other fields.

[0076] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A piezoelectric type force-induced luminescence self-powered optical fiber pressure sensor, characterized in that, Including: Coupled optical fiber (1), sensing layer (2), pressure-resistant protective layer (3); The coupled optical fiber (1) includes a core (1-1) and a cladding (1-2), the cladding (1-2) wraps around the core (1-1), and the core (1-1) is a hard polymer; one end of the coupled optical fiber (1) is a tapered structure (1-3); The sensing layer (2) wraps around the outside of the tapered structure (1-3) of the coupled optical fiber (1), and the sensing layer (2) includes a piezoelectric type force-induced luminescence material and a piezoelectric polymer, and the piezoelectric type force-induced luminescence material is dispersed in the piezoelectric polymer; The pressure-resistant protective layer (3) wraps around the outside of the sensing layer (2), and the pressure-resistant protective layer (3) is a hard polymer.

2. The piezoelectric type force-induced luminescence self-powered optical fiber pressure sensor according to claim 1, characterized in that, The refractive indices of the core (1-1) and the cladding (1-2) of the coupled optical fiber (1) satisfy the total reflection condition.

3. The piezoelectric type force-induced luminescence self-powered optical fiber pressure sensor according to claim 2, wherein The refractive index of the material of the cladding (1-2) is lower than the refractive index of the material of the core (1-1).

4. The piezoelectric type force-induced luminescence self-powered optical fiber pressure sensor according to claim 1, characterized in that The hard polymers of the core (1-1) and the pressure-resistant protective layer (3) are epoxy resin and polymethyl methacrylate; The cladding (1-2) is a polymer, and the polymer is epoxy resin, polymethyl methacrylate, polyvinylidene fluoride, polysiloxane, polydimethylsiloxane or silicone rubber.

5. The piezoelectric type force-induced luminescence self-powered optical fiber pressure sensor according to claim 1, wherein, The coupled optical fiber (1) is cylindrical.

6. The piezoelectric type force-induced luminescence self-powered optical fiber pressure sensor according to claim 1, characterized in that The mass fraction of the piezoelectric type force-induced luminescence material in the sensing layer (2) is 25%-50%.

7. The piezoelectric type force-induced luminescence self-powered optical fiber pressure sensor according to claim 1, characterized in that, The piezoelectric type force-induced luminescence material is an oxide, sulfide, sulfur oxide, titanate, phosphate, aluminate, silicate, niobate doped with transition metal ions or rare earth ions, or methylammonium lead bromide perovskite, cesium lead bromide perovskite, tetraphenylethylene.

8. The piezoelectric type force-induced luminescence self-powered optical fiber pressure sensor according to claim 1, characterized in that The piezoelectric polymer of the sensing layer (2) is polyvinylidene fluoride, polyvinylidene fluoride-trifluoroethylene copolymer, polyamide, polylactic acid, epoxy resin, polymethyl methacrylate or polyvinylidene fluoride.

9. The piezoelectric type force-induced luminescence self-powered optical fiber pressure sensor according to claim 1, characterized in that, The sensing layer (2) is cylindrical or film-shaped coaxial with the coupled optical fiber; The pressure-resistant protective layer (3) is cylindrical or film-shaped coaxial with the coupled optical fiber (1).

10. The preparation method of the piezoelectric type force-induced luminescence self-powered optical fiber pressure sensor according to any one of claims 1-9, characterized in that, Including the following steps: Step 1: Fill the hard polymer precursor into a mold, then cure and take out to obtain the core (1-1); Step 2: Uniformly coat a polymer outside the core (1-1) and then cure to obtain the cladding (1-2); Step 3: Mix the piezoelectric polymer and the piezoelectric type force-induced luminescence material evenly, and perform degassing treatment in a vacuum environment; Subsequently, prepare a sensing layer (2) with uniform size on the outside of the coupled optical fiber (1) by spin coating method or mold method; Step 4: Inject the hard polymer precursor into the mold, and coaxially insert the coupled optical fiber (1) containing the sensing layer (2) into the mold, and perform thermal curing at 60°C - 120°C for 1 - 4 hours to form the pressure-resistant protective layer (3), and then take out the obtained piezoelectric type force-induced luminescence self-powered fiber pressure sensor.

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