Dual-channel Fabry-Perot cavity optical fiber pressure sensor and preparation method thereof

Abstract

The invention aims to provide a dual-channel Fabry-Perot cavity optical fiber pressure sensor with high reliability and high precision and a preparation method thereof, the dual-channel Fabry-Perot cavity optical fiber pressure sensor comprises a base, a pressure-sensitive diaphragm and an optical fiber, the pressure-sensitive diaphragm is hydrogel based on a PVA-boric acid complex structure, a carbon dot fluorescent nano-material is doped in the hydrogel, and the optical fiber is doped in the carbon dot fluorescent nano-material. The dual-channel optical system comprises a pressure sensing channel for detecting the change of a Fabry-Perot cavity interference spectrum by adopting a broadband light source, and a damage monitoring channel for exciting carbon dot fluorescence by adopting an excitation light source and judging diaphragm damage through the change of fluorescence signal intensity. The pressure-sensitive diaphragm based on a PVA-boric acid complex structure has a self-repairing function and can drift for a long time; 0.5% F.S. / month, the service life of the sensor is prolonged, and the accuracy of pressure acquisition is improved; meanwhile, a carbon dot fluorescent nano-material with excellent biocompatibility is doped into the pressure-sensitive diaphragm, so that real-time self-monitoring of optical damage is realized, and the carbon dot fluorescent nano-material is used as an auxiliary function to improve the reliability of pressure acquisition of the sensor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensors, in particular to a double-channel Fabry-Perot cavity optical fiber pressure sensor and a preparation method thereof. BACKGROUND

[0002] With the rapid development of implantable medical devices, optical fiber pressure sensors can be implanted in the human body due to their small size and good biocompatibility, and can realize real-time and accurate measurement of physiological parameters such as blood pressure, intracranial pressure, and lung pressure, thereby providing an important basis for disease diagnosis and treatment. The Fabry-Perot cavity optical fiber pressure sensor is a high-precision pressure measurement device based on the Fabry-Perot interference principle. The traditional pressure-sensitive diaphragm material produces micro-cracks under cyclic pressure and cannot be sensed, resulting in inaccurate pressure detection. Moreover, when the sensor is implanted in the human body, if it fails, a secondary surgery is required, which may cause complications and other risks. SUMMARY

[0003] An object of the present application is to provide a double-channel Fabry-Perot cavity optical fiber pressure sensor with high reliability and high accuracy.

[0004] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: a double-channel Fabry-Perot cavity optical fiber pressure sensor, comprising a base, a pressure-sensitive diaphragm, and an optical fiber. The pressure-sensitive diaphragm is a hydrogel based on a PVA-boric acid complex structure, and carbon dot fluorescent nanomaterials are doped in the hydrogel. The double-channel optical system includes a pressure sensing channel that detects changes in Fabry-Perot cavity interference spectrum using a broadband light source, and a damage monitoring channel that monitors damage to the diaphragm by exciting carbon dot fluorescence using an excitation light source and judging changes in fluorescence signal intensity.

[0005] First, a hydrogel based on a PVA-boric acid complex structure is used to replace traditional rigid materials to prepare a pressure-sensitive diaphragm with high elasticity and fatigue resistance. Based on the dynamic complex bond network between PVA and borax, the hydrogel has a rapid reconfiguration ability at 37℃ physiological environment, repairs crack structures, and meets the needs of long-term implantation and stable monitoring of the sensor. Meanwhile, carbon dot fluorescent nanomaterials are doped in the hydrogel. When the hydrogel diaphragm has micro-cracks or damage, the local distribution of carbon dots and the polarity of the environment change, and the fluorescence intensity changes significantly. By exciting with ultraviolet or blue light, the fluorescence in the damaged area is enhanced or weakened, forming an obvious visual signal. The fluorescence signal is restored synchronously after the hydrogel is repaired. The fluorescence signal also reflects the accuracy of pressure measurement. Only when the pressure-sensitive diaphragm 20 is undamaged or has minor damage, the collected pressure signal is useful. When the pressure-sensitive diaphragm 20 has major damage, the collected pressure signal is not useful, which further improves the accuracy of sensor measurement and avoids blindly trusting the collected pressure signal and causing harm to the patient.

[0006] The material formula of the pressure-sensitive diaphragm includes, in terms of mass percentage: 8-12 wt% polyvinyl alcohol (PVA), 0.3-0.7 wt% borax, 1-3 wt% glycerol, 0.02-0.1 wt% carbon dots, 0.5-1.5 wt% polyethylene glycol diacrylate (PEGDA), 0.05-0.2 wt% lithium phenyl-2,4,6-trimethylbenzoyl phosphinate (LAP), and the rest is deionized water. Among them, the content of PVA ensures film formation and strength, borax acts as a dynamic crosslinking agent, this component can form stable physical crosslinking, PEGDA acts as a covalent crosslinking agent, glycerol acts as a plasticizer, and LAP acts as a photoinitiator. The proportion of PEGDA and LAP is matched to meet the free radical photo-crosslinking conditions, the surface of the fluorescent carbon dots is modified with carboxyl or amino groups, and the content of carbon dots is less than 0.1 wt% to avoid fluorescence quenching.

[0007] The dual-channel optical system further includes a wavelength division multiplexer (WDM) for separating the interference signal and the fluorescent signal, and a spectral analysis module. The spectral analysis module performs fast Fourier transform (FFT) demodulation on the interference signal to calculate the cavity length change, and performs peak intensity integration on the fluorescent signal to calculate the damage index.

[0008] The optical fiber is a single-mode optical fiber, which does not need to be physically separated from the cavity, has a compact structure, and different wavelength optical signals are independently transmitted in the single-mode optical fiber. The single-mode optical fiber provides better performance for the WDM due to its low dispersion, high bandwidth, high wavelength isolation, small size, high power tolerance and long-term stability, and is particularly suitable for deployment scenarios of high-precision and miniaturized sensors. The pressure sensing channel uses a 1550 nm ASE broadband light source to irradiate the sensor, collects reflected interference light, and uses a spectrometer to analyze the cavity length change. The damage monitoring channel uses a 380-420 nm laser to excite carbon dot fluorescence, the wavelength response region is 450-600 nm, and the signal is separated by a WDM module and sent to a spectrometer. The wavelength division multiplexing technology (WDM) uses different wavelength optical signals to be independently transmitted in a single-mode optical fiber without interference, and two wavelengths respectively carry different channel data or sensing signals. The dual-wavelength is used for pressure measurement and damage measurement.

[0009] A recess is provided on the base, and a pressure-sensitive diaphragm cover is provided at the opening of the recess to form an FP cavity. Reflective films are correspondingly provided at the two end faces of the FP cavity to reduce light loss and improve the stability of the interference signal. The thickness of the reflective film is 5-100 nm. The thickness of the reflective film 40 usually affects the reflectivity and interference effect. In the visible light band, a reflective film of a metal (such as gold or silver) or a high refractive index medium with a thickness of 5-100 nm can achieve high reflectivity. For example, a reflective layer with a thickness of 40-80 nm is commonly used in FP interference structures, and has good reflective performance and mechanical stability.

[0010] The base comprises a first substrate and a second substrate, the first substrate is provided with a first through hole, the first through hole, the surface of the second substrate and the surface of the pressure sensitive diaphragm jointly enclose an FP cavity, and a reflective film is arranged on the surface of the pressure sensitive diaphragm and the surface of the second substrate in the FP cavity. The base is packaged as a whole by a plurality of substrates through a bonding technology, the first substrate which needs to be provided with the first through hole is arranged as a separate substrate, and a first through hole is processed on the first substrate. Since the first through hole is all through, the problem of uneven surface caused by wet etching or ion etching method is avoided, so that the FP cavity end face reflective film has high flatness, the sensor has high precision, and the consistency of the sensor is high, so that the performance of the sensors in the same batch is stable.

[0011] The second substrate is provided with a fiber sleeve, and the inner cavity of the fiber sleeve and the surface of the second substrate enclose a fiber mounting part, and the FP cavity and the fiber mounting part are coaxial and arranged at intervals in the axial direction of the fiber. The end of the fiber abuts against the second substrate, the surface of the second substrate has high flatness, the deviation of the optical signal during reception is reduced, and the influence of signal loss is reduced.

[0012] Another object of the present application is to provide a preparation method of a double-channel Fabry-Perot cavity optical fiber pressure sensor with high reliability and high precision.

[0013] In order to achieve the above object, the technical scheme adopted by the present application is as follows: a preparation method of a double-channel Fabry-Perot cavity optical fiber pressure sensor, a pressure sensitive diaphragm with a reflective film and a base with a reflective film are prepared, the base and the pressure sensitive diaphragm are bonded, the fiber sleeve is bonded with the base, the fiber is inserted into the fiber sleeve to be fixed and packaged, the wavelength is 365 nm, the intensity is 60 mW / cm², the time is 20 s, the axial and radial fixation is realized, finally the entire Fabry-Perot cavity structure (including the fixed fiber, the base, the reflective film and the like) is isolated from the external environment through the packaging layer, and the protective layer or the shell is used to prevent the influence of external factors (such as humidity, dust, chemical corrosion and mechanical impact) on the performance of the sensor.

[0014] The preparation steps of the pressure sensitive diaphragm include: A1) solution preparation: PVA is dissolved in deionized water and heated to 80-100 DEG C, the uniformity of the solution is improved, after cooling to room temperature, carbon dots, borax, glycerol, polyethylene glycol diacrylate (PEGDA) and phenyl-2, 4, 6-trimethyl benzoyl lithium phosphate (LAP) are added in proportion and stirred uniformly; because high temperature may cause aggregation of carbon dots or degradation of surface functional groups, resulting in decreased fluorescence performance, the addition of carbon dots after cooling can ensure uniform dispersion of carbon dots under mild conditions, also can avoid inactivation of LAP in the heating stage, ensure the smooth progress of subsequent photopolymerization reaction, and prevent pre-polymerization or self-crosslinking of PEGDA at high temperature, and ensure the controllability of crosslinking reaction.

[0015] A2) Spin coating: drop the solution on the clean substrate surface, spin coating with a spin coater, speed 1000-4000 rpm, time 45-70 s; A3) Crosslinking and curing: irradiate with 365 nm UV light for 3-6 min to complete the crosslinking reaction and curing; the free radical polymerization of PEGDA forms a chemical crosslinking main chain, and the dynamic crosslinking of PVA-borax and the hydrogen bonding of glycerol form a physical crosslinking side chain, and the carbon dots are uniformly dispersed in the network to form a double-continuous phase structure, which has high strength (contribution of chemical crosslinking) and self-repairing ability (reversibility of physical crosslinking).

[0016] A4) Laser cutting and edge treatment: cut out a circular film piece using an ultraviolet cutting machine, and clean the edge of the film piece with ethanol ultrasonic for 4-6 min, and plasma polish in argon environment, power 10-25 w, time 20-50 s, to obtain a pressure-sensitive film piece; A5) Reflective layer plating: magnetron sputtering of 5-100 nm reflective layer, sputtering speed 0.1-1 Å / s, substrate temperature controlled at 20-50°C.

[0017] The preparation steps of the base are: B1) Main body preparation: take the first substrate and the second substrate, cut the first through hole on the first substrate using a CO2 laser, and surface plasma polish, power 15-35 w, time 30-60 s; B2) Reflective layer plating: magnetron sputtering of 5-100 nm reflective layer on the second substrate, sputtering speed 0.1-1 Å / s, substrate temperature controlled at 20-50°C; B3) Base bonding: low-temperature plasma bonding of the first substrate with a through hole and the second substrate in a nitrogen environment, power 25-45 w, which can balance the activation efficiency and material protection; pressure 2-5 kPa, which can maintain the stable ionization state of the plasma and improve the surface modification effect; time 45-70 s, bonding strength > 6 MPa, which can meet the long-term stability requirements and ensure that the material does not delaminate or fall off in the body; The base, pressure-sensitive film piece bonding steps are: C1) Surface pretreatment: oxygen plasma treatment of the pressure-sensitive film piece and the first substrate, which can introduce oxygen-containing functional groups on the surface of the material, and these polar groups can enhance the chemical interaction (such as hydrogen bonding, van der Waals force) between the surface and the adhesive, thereby improving the adhesion. Preferably, power 30-80 W, time 50-80 s; C2) Dispensing: apply a PEGDA / LAP solution containing 0.1% light absorber to the bonding area of the first substrate, width 0.05-0.2 mm; since the pressure-sensitive film piece also contains PEGDA / LAP components, using PEGDA / LAP solution as an adhesive can enhance the bonding strength.

[0018] C3) Pre-pressure alignment: Align the pressure-sensitive diaphragm with the first through hole using a six-axis micro-motion stage, and apply a pre-pressure of 3-6 N; ensure full fit between the base and the pressure-sensitive diaphragm, eliminate gaps, and avoid stress concentration.

[0019] C4) UV curing: 365 nm UV light penetrates the sapphire to complete cross-linking, with a power density of 15-30 mW / cm² and a time of 40-70 s.

[0020] In the above scheme, the pressure-sensitive diaphragm based on the PVA-boric acid complex structure has a self-healing function and a long-term drift of <0.5%FS / month, which improves the service life of the sensor and the accuracy of pressure acquisition. At the same time, the pressure-sensitive diaphragm incorporates biocompatible carbon dot fluorescent nanomaterials to achieve real-time self-monitoring of optical damage, which serves as an auxiliary function to improve the reliability of the sensor's pressure acquisition. Attached Figure Description

[0021] Figure 1 Schematic diagram of the sensing system; Figure 2 This is a schematic diagram of the structure of a Fabry-Perot cavity fiber optic pressure sensor; Figure 3 for Figure 2 Schematic diagram of the middle section; Figure 4 This is a frequency response curve of the sensor in this application; Figure 5 This is a temperature offset curve of the sensor in this application; Figure 6 This is a graph showing the linear relationship between the sensor output and pressure change, as well as the hysteresis error curve in this application. Detailed Implementation

[0022] To make the objectives, technical solutions, and beneficial effects of the present invention clearer, embodiments of fiber optic pressure sensors prepared under the same component formulation but different process conditions are given below.

[0023] Example 1 Preparation of pressure-sensitive membrane 20: 10 wt% PVA was dissolved in deionized water and heated to 90°C, and after cooling to room temperature, 0.5 wt% borax, 2 wt% glycerol, 0.05 wt% carbon dots, 1 wt% polyethylene glycol diacrylate (PEGDA), 0.1 wt% lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) were added and stirred uniformly; the solution was dropped onto the surface of a clean substrate and spin-coated into a film using a spin coater at a speed of 3000 rpm for 60 s; 365 nm ultraviolet light was used for irradiation for 5 min to complete the cross-linking reaction and curing; a circular membrane was cut out using an ultraviolet cutting machine, the edges of the membrane were cleaned with ethanol for 5 min using ultrasonic cleaning, and plasma polishing was performed in an argon environment at a power of 15 w for 30 s to obtain the pressure-sensitive membrane 20; a 50 nm reflective layer was magnetron sputtered at a sputtering speed of 0.5 Å / s with the substrate temperature controlled at 30°C.

[0024] Preparation of base 10: take the first substrate 11 and the second substrate 12, cut the first through hole 111 on the first substrate 11 using a CO2 laser, and perform surface plasma polishing at a power of 20 w for 40 s; a 50 nm reflective layer was magnetron sputtered on the second substrate 12 at a sputtering speed of 0.5 Å / s with the substrate temperature controlled at 30°C; the first substrate 11 with the through hole and the second substrate 12 were low-temperature plasma bonded in a nitrogen environment at a power of 35 w, a pressure of 3 kPa, and a time of 60 s, and the bonding strength was 7 MPa.

[0025] Precise assembly of the assembly: the pressure-sensitive membrane 20 and the first substrate 11 were subjected to oxygen plasma treatment at a power of 50 W for 60 s; a PEGDA / LAP solution containing 0.1% light absorber was coated on the bonding area of the first substrate 11 with a width of 0.05-0.2 mm; the pressure-sensitive membrane 20 was aligned with the first through hole 111 by a six-axis micro-motion stage, and a pre-pressure of 5 N was applied; cross-linking was completed by 365 nm ultraviolet light penetrating the sapphire at a power density of 20 mW / cm² for 60 s.

[0026] Curing and packaging of the optical fiber: the optical fiber 30 was inserted into the sleeve, the UV glue was cured, and finally the entire Fabry-Perot cavity structure (including the fixed optical fiber, the base, the reflective film, etc.) was isolated from the external environment by the packaging layer.

[0027] Example 2 Preparation of pressure-sensitive membrane 20: 10 wt% PVA was dissolved in deionized water and heated to 90°C, and after cooling to room temperature, 0.5 wt% borax, 2 wt% glycerol, 0.02 wt% carbon dots, 0.5 wt% polyethylene glycol diacrylate (PEGDA), 0.1 wt% lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) were added and stirred uniformly; the solution was dropped onto the surface of a clean substrate and spin-coated into a film using a spin coater at a speed of 3000 rpm for 60 s; 365 nm UV light was used for irradiation for 6 min to complete the cross-linking reaction and curing; a circular membrane was cut out using an ultraviolet cutting machine, the edges of the membrane were cleaned with ethanol for 5 min using ultrasonic cleaning, and plasma polishing was performed in an argon environment at a power of 15 w for 30 s to obtain the pressure-sensitive membrane 20; a 80 nm reflective layer was magnetron sputtered at a sputtering speed of 0.5 Å / s with the substrate temperature controlled at 30°C.

[0028] Preparation of base 10: take the first substrate 11 and the second substrate 12, cut the first through hole 111 on the first substrate 11 using a CO2 laser, and perform surface plasma polishing at a power of 20 w for 40 s; a 80 nm reflective layer was magnetron sputtered on the second substrate 12 at a sputtering speed of 0.5 Å / s with the substrate temperature controlled at 30°C; the first substrate 11 with the through hole and the second substrate 12 were low-temperature plasma bonded in a nitrogen environment at a power of 35 w, a pressure of 3 kPa, and a time of 60 s, with a bonding strength of 7 MPa.

[0029] Precise assembly of components: the pressure-sensitive membrane 20 and the first substrate 11 were subjected to oxygen plasma treatment at a power of 50 W for 60 s; a PEGDA / LAP solution containing 0.1% light absorber was coated on the bonding area of the first substrate 11 with a width of 0.05-0.2 mm; the pressure-sensitive membrane 20 was aligned with the first through hole 111 by a six-axis micro-motion stage, and a pre-pressure of 5 N was applied; cross-linking was completed by 365 nm ultraviolet light penetrating the sapphire at a power density of 20 mW / cm² for 60 s.

[0030] Curing and packaging of optical fiber: the optical fiber 30 was inserted into the sleeve, the UV glue was cured, and finally the entire Fabry-Perot cavity structure (including the fixed optical fiber, base, reflective film, etc.) was isolated from the external environment by the packaging layer.

[0031] Example 3 Preparation of pressure sensitive membrane 20: 12wt% PVA was dissolved in deionized water and heated to 90°C, after cooling to room temperature, 0.5wt% borax, 1wt% glycerol, 0.05wt% carbon dots, 1wt% polyethylene glycol diacrylate (PEGDA), 0.1wt% lithium phenyl-2,4,6-trimethylbenzoyl phosphite (LAP) were added and stirred uniformly; the solution was added dropwise on the surface of a clean substrate and spin-coated into a film using a spin coater at a speed of 3000 rpm for 60 s; using 365 nm ultraviolet light for 5 min to complete the cross-linking reaction and curing; using an ultraviolet cutting machine to cut out a circular membrane, the edge of the membrane was cleaned with ethanol for 5 min, and plasma polished in an argon environment at a power of 25w for 30s to obtain the pressure sensitive membrane 20; a 50nm reflective layer was magnetron sputtered at a sputtering speed of 0.5Å / s and a substrate temperature of 30°C.

[0032] Preparation of base 10: take the first substrate 11 and the second substrate 12, cut the first through hole 111 on the first substrate 11 using CO2 laser, surface plasma polishing, power 20w, time 40s; magnetron sputtering a 50nm reflective layer on the second substrate 12 at a sputtering speed of 0.5Å / s and a substrate temperature of 30°C; low temperature plasma bonding of the first substrate 11 with the through hole and the second substrate 12 in a nitrogen environment, power 35w, pressure 3kPa, time 60s, bonding strength 7MPa.

[0033] Precise assembly of components: oxygen plasma treatment of the pressure sensitive membrane 20 and the first substrate 11, power 50W, time 60s; coating the PEGDA / LAP solution containing 0.1% light absorber on the bonding area of the first substrate 11, width 0.05-0.2mm; aligning the pressure sensitive membrane 20 with the first through hole 111 through a six-axis micro stage, applying a 5N pre-pressure; cross-linking by 365nm ultraviolet light penetrating the sapphire, power density 30mW / cm², time 60s.

[0034] Curing and packaging of optical fiber: the optical fiber 30 is inserted into the sleeve, the UV glue is cured, and finally the entire Fabry-Perot cavity structure (including the fixed optical fiber, base, reflective film, etc.) is isolated from the external environment by the packaging layer.

[0035] Comparative example Preparation of pressure sensitive membrane: etching a pressure sensitive membrane on a single crystal silicon wafer using ICP; Preparation of the base: take the first substrate and the second substrate, cut the first through hole on the first substrate by CO2 laser, surface plasma polishing, power 15-35w, time 30-60s; magnetron sputtering 5-100nm reflective layer on the second substrate, sputtering speed 0.1-1 Å / s, substrate temperature control at 20-50℃; low temperature plasma bonding of the first substrate with through hole and the second substrate in nitrogen environment, power 25-45w, pressure 2-5kPa, time 45-70s, bonding strength >6 MPa.

[0036] Precise assembly of the assembly: the pressure sensitive diaphragm is bonded with the base by direct bonding technology.

[0037] Curing and packaging of the optical fiber: the optical fiber is inserted into the sleeve, the UV glue is cured, and finally the entire Fabry-Perot cavity structure (including the fixed optical fiber, base, reflective film, etc.) is isolated from the external environment by the packaging layer.

[0038] In order to make the purpose, technical scheme and beneficial effects of the present application clearer, Table 1 shows the performance comparison of sensors with the same structure and size prepared by the preparation methods of Examples 1-3 and Comparative Examples.

[0039] Table 1 Performance Example 1 Example 2 Example 3 Comparative Example Sensitivity (kPa-1) 0.082 0.071 0.089 0.065 Damage detection performance (min) 1 3 2 / Self-repairing performance (times) >10 >5 >8 / Biocompatibility (%) >95 >90 >92 >80 Long-term stability (% F.S. / 24 h) <0.5 <0.7 <0.4 >1 As can be seen from Table 1, the silicon wafer system used in the comparative example is relatively stable at high pressure, but its sensitivity is low in the case of small pressure change, mainly due to the limited displacement of the diaphragm caused by the rigid structure, and the small change of the interference signal. In addition, the outer surface is not modified by biological inertness, and the biocompatibility test shows that the hydrogel structure in the present application.

[0040] In Examples 1-3, the carbon dot fluorescence attenuation or enhancement can be used to identify diaphragm damage within 1-3min window, and multiple repairs can be performed, and the drift is <0.4%F.S. / 24h, which indicates that structure / packaging optimization can significantly prolong the effective monitoring period.

[0041] In this paper, the test method of each performance of the sensor is as follows:

[0042] Use the air pressure cavity to apply 0-10 kPa pressure, the spectrometer detects the wavelength shift Δλ, and calculates the sensitivity: k=PΔλ (target value ≥0.08nm / kPa).

[0043] Damage monitoring performance test: Apply microcracks or sharp scratches on the surface of the diaphragm, and observe the change of fluorescence intensity and the boundary of damage identification area; Use confocal fluorescence microscope and image processing algorithm to analyze the fluorescence image; The monitoring indicators include the amplitude of fluorescence intensity decrease (>30% is determined as damage), fluorescence signal discontinuity, damage area, and edge sharpness. If the damage causes the fluorescence signal to drop instantaneously and remain irreversibly for more than 5 minutes, it is determined as irreversible damage, and the device needs to be replaced.

[0044] Self-repair performance test: Place the damaged hydrogel film in a 37°C PBS solution and observe the repair time and fluorescence recovery degree. Multiple damage-repair cycle experiments verify the durability of self-repair.

[0045] Biocompatibility test: According to ISO 10993 standards, cytotoxicity test (MTT method) and hemolysis rate detection (target value <5%) are performed.

[0046] Long-term stability test: Apply constant pressure (e.g. 5KPa) continuously in constant temperature (37°C) physiological saline or simulated body fluid, and monitor the drift of sensor output signal (more than 72h).

[0047] Objective: Signal drift rate <1% F.S. / 24h.

[0048] Significance: Verify the stability of the sensor in long-term implantation environment, avoid data distortion caused by material creep or packaging failure.

[0049] Dynamic response characteristic test: Use invasive blood pressure simulator to simulate physiological pressure fluctuation, record the frequency response curve of the sensor.

[0050] Objective: Measure response time and recovery time.

[0051] Significance: Ensure that the sensor can accurately capture dynamic pressure changes in cardiovascular and other scenarios.

[0052] Temperature drift test: Measure the change of zero point output and sensitivity with temperature in the range of 30-45°C (step 5°C), calculate the temperature coefficient (e.g. nm / kPa / ℃).

[0053] Objective: Temperature drift <0.05% F.S. / ℃.

[0054] Significance: Quantify the impact of temperature on measurement, provide basis for algorithm compensation.

[0055] Linearity and hysteresis test: The pressure was loaded in a stepwise increasing / decreasing manner over the full scale (0-10 kPa) and the linearity error (R² ≥ 0.999) and hysteresis error (< 1% F.S.) were calculated.

[0056] Significance: Verify linearity of sensor output vs. pressure change and hysteresis error.

Claims

1. A dual channel Fabry-Perot cavity optical fiber pressure sensor comprising a base (10), a pressure sensitive diaphragm (20) and an optical fiber (30), characterized in that: The pressure-sensitive diaphragm (20) is a hydrogel based on a PVA-boric acid complex structure, and carbon dot fluorescent nanomaterials are doped in the hydrogel; the dual-channel optical system includes a pressure sensing channel for detecting changes in Fabry-Perot cavity interference spectrum by using a broadband light source, and a damage monitoring channel for monitoring damage to the diaphragm by exciting carbon dot fluorescence by using an excitation light source and judging damage by changes in fluorescence signal intensity.

2. The dual-channel Fabry-Perot cavity optical fiber pressure sensor of claim 1, wherein, The material formula of the pressure-sensitive diaphragm (20) includes, by mass percentage, 8-12 wt% polyvinyl alcohol (PVA), 0.3-0.7 wt% borax, 1-3 wt% glycerol, 0.02-0.1 wt% carbon dots, 0.5-1.5 wt% polyethylene glycol diacrylate (PEGDA), 0.05-0.2 wt% lithium phenyl-2,4,6-trimethylbenzoyl phosphite (LAP), and the remainder is deionized water.

3. The dual-channel Fabry-Perot cavity optical fiber pressure sensor of claim 1, wherein: The dual-channel optical system further includes a wavelength division multiplexer (WDM) for separating the interference signal and the fluorescence signal, and a spectrum analysis module for performing fast Fourier transform (FFT) demodulation of the interference signal to obtain changes in cavity length, and performing peak intensity integration of the fluorescence signal to calculate a damage index.

4. The dual-channel Fabry-Perot cavity optical fiber pressure sensor of claim 1, wherein: The optical fiber (30) is a single-mode optical fiber, the broadband light source has a wavelength of 1550 nm, the excitation light source has a wavelength of 380-420 nm, and the fluorescence signal has a wavelength of 450-600 nm; the optical signals of different wavelengths are independently transmitted in the single-mode optical fiber.

5. The dual-channel Fabry-Perot cavity optical fiber pressure sensor of claim 1, wherein: The base (10) is provided with a recessed cavity, and the pressure-sensitive diaphragm (20) is arranged on the opening of the recessed cavity to form an FP cavity; two end faces of the FP cavity are provided with reflective films (40), and the thickness of the reflective films (40) is 5-100 nm.

6. The dual-channel Fabry-Perot cavity optical fiber pressure sensor of claim 1, wherein: The base (10) includes a first substrate (11) and a second substrate (12); the first substrate (11) is provided with a first through hole (111); the first through hole (111), the surface of the second substrate (12), and the surface of the pressure-sensitive diaphragm (20) jointly enclose the FP cavity; and the reflective films (40) are arranged on the surface of the pressure-sensitive diaphragm (20) and the surface of the second substrate (12) in the FP cavity.

7. The dual-channel Fabry-Perot cavity optical fiber pressure sensor of claim 6, wherein: The second substrate (12) is provided with an optical fiber sleeve (50), and the inner cavity of the optical fiber sleeve (50) and the surface of the second substrate (12) jointly enclose an optical fiber mounting portion; the FP cavity and the optical fiber mounting portion are coaxial and spaced apart in the axial direction of the optical fiber (30).

8. The method for preparing a dual-channel Fabry-Perot cavity fiber-optic pressure sensor according to any one of claims 1 to 7, characterized in that: The pressure-sensitive diaphragm (20) with the reflective films (40) and the base (10) with the reflective films (40) are prepared, the base (10) and the pressure-sensitive diaphragm (20) are bonded, the optical fiber sleeve (50) and the base (10) are bonded, and the optical fiber (30) is inserted into the optical fiber sleeve (50) to be fixed and packaged; The preparation steps of the pressure-sensitive diaphragm (20) include: A1) solution preparation: polyvinyl alcohol (PVA) is dissolved in deionized water and heated to 80-100°C; after cooling to room temperature, carbon dots, borax, glycerol, polyethylene glycol diacrylate (PEGDA), and lithium phenyl-2,4,6-trimethylbenzoyl phosphite (LAP) are added in proportion and stirred uniformly; A2) Spin coating: drop the solution on the cleaned substrate surface, spin coating with a spin coater, speed 1000-4000 rpm, time 45-70 s; A3) Cross-linking and curing: irradiation with 365 nm UV light for 3-6 min to complete the cross-linking reaction and curing; A4) Laser cutting and edge treatment: cutting out a circular film piece using an ultraviolet cutting machine, the film piece edge is cleaned with ethanol ultrasonic for 4-6 min, plasma polishing in argon environment, power 10-25 w, time 20-50 s, to get a pressure sensitive film piece (20); A5) Reflective layer plating: magnetron sputtering 5-100 nm reflective layer, sputtering speed 0.1-1 Å / s, substrate temperature control at 20-50℃.

9. The method of claim 8, wherein: The preparation steps of the base (10) are: B1) Main body preparation: take the first substrate (11) and the second substrate (12), cut the first through hole (111) on the first substrate (11) using CO2 laser, surface plasma polishing, power 15-35 w, time 30-60 s; B2) Reflective layer plating: magnetron sputtering 5-100 nm reflective layer on the second substrate (12), sputtering speed 0.1-1 Å / s, substrate temperature control at 20-50℃; B3) Base bonding: low temperature plasma bonding of the first substrate (11) and the second substrate (12) with through holes in nitrogen environment, power 25-45 w, pressure 2-5 kPa, time 45-70 s, bonding strength > 6 MPa.

10. The method of claim 8, wherein: The bonding steps of the base (10) and the pressure sensitive film piece (20) are: C1) Surface pretreatment: oxygen plasma treatment of the pressure sensitive film piece (20) and the first substrate (11), power 30-80 W, time 50-80 s; C2) Dispensing: coating PEGDA / LAP solution containing 0.1% light absorber on the bonding area of the first substrate (11), width 0.05-0.2 mm; C3) Pre-pressing alignment: aligning the pressure sensitive film piece (20) with the first through hole (111) by a six-axis micro stage, applying a pre-pressing force of 3-6 N; C4) UV curing: cross-linking by 365 nm UV light penetrating sapphire, power density 15-30 mW / cm², time 40-70 s.

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