MEMS optical fiber gas and temperature integrated sensor and preparation method thereof

Abstract

The invention relates to the technical field of optical fiber sensors, in particular to an MEMS optical fiber gas and temperature integrated sensor and a preparation method thereof.The MEMS optical fiber gas and temperature integrated sensor is characterized in that a three-stage stepped structure is arranged at one end of a quartz supporting base, a Fabry-Perot micro-cantilever diaphragm is fixed to a first stepped plane, and a filter disc-permeable membrane composite structure is arranged on a second stepped plane layer; three functional cavities are arranged in the quartz supporting base. An optical fiber collimating lens and a photoacoustic cell are installed in a first containing cavity, and emergent light of the optical fiber collimating lens is irradiated to the Fabry-Perot micro-cantilever diaphragm through the photoacoustic cell. A first ceramic optical fiber insertion core is mounted in the second accommodating cavity, the optical fiber insertion core is tightly attached to the rear end of the temperature sensing crystal, and the front end of the temperature sensing crystal is parallel to the first step plane; a second ceramic optical fiber ferrule is installed in the third containing cavity, and emergent light of the optical fiber ferrule irradiates the Fabry-Perot micro-cantilever diaphragm and then is reflected back to the optical fiber. The multi-parameter high-sensitivity synchronous detection of gas, temperature and micro water is realized, and the device has the advantage of vibration interference resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of MEMS optical fiber sensors, and in particular to a MEMS optical fiber gas and temperature integrated sensor based on a Fabry-Perot (FP) microcantilever beam. Background Art

[0002] The fiber-optic integrated gas and temperature sensor described in this invention belongs to the field of precision optical sensing technology and is primarily used in industrial process monitoring (such as SF6 gas detection in power equipment), environmental monitoring (atmospheric pollutant analysis), medical equipment (anesthetic gas concentration monitoring), smart grids (transformer oil moisture detection), and aerospace (propellant leak monitoring). With the development of the Internet of Things and Industry 4.0, market demand for highly sensitive, electromagnetic interference-resistant, and remotely monitored multi-parameter sensors continues to grow. Current mainstream technologies in the fiber-optic sensing field include fiber Bragg grating (FBG) technology (which uses Bragg wavelength shift to achieve temperature / strain measurement, but has limited gas sensitivity and requires an external sensitive film), Fabry-Perot interferometry (which uses changes in air cavity length to measure pressure / temperature, but suffers from temperature-stress cross-sensitivity), and microcantilever technology (which uses beam bending to detect gas adsorption, but MEMS packaging is susceptible to mechanical vibration).

[0003] However, existing technologies have significant flaws: First, multi-parameter detection capabilities are insufficient. For example, the Honeywell HGS series uses a discrete sensor group, resulting in a large system size (>200 cm³) and high cost (>US$500 per set). Second, environmental adaptability is insufficient. Traditional packaging structures (such as Siemens SIP packages) experience fiber coupling failure due to adhesive creep and metal / glass thermal expansion coefficient mismatch under strong vibration (>5g) and high humidity (>85%RH) conditions. Third, temperature drift is a problem. Products such as the Omron D6T series have a temperature error of ±2%FS / °C, which is mainly attributed to the insufficient thermal stability caused by the insufficient glass transition temperature (Tg≈250°C) of sensitive materials (such as polyimide). Summary of the Invention

[0004] The purpose of the present invention is to overcome the technical bottlenecks of the above-mentioned existing optical fiber sensors in multi-parameter integration, environmental adaptability and temperature stability, and to provide a MEMS optical fiber gas and temperature integrated sensor based on Fabry-Perot (FP) microcantilever and its packaging method.

[0005] The purpose of the present invention can be achieved by the following technical solutions: As a first aspect of the present invention, a MEMS fiber optic gas and temperature integrated sensor is provided, comprising a quartz support base having a three-step structure at one end, wherein a Fabry-Perot microcantilever diaphragm is fixed on the first step plane, and a filter-permeable membrane composite structure is fixed on the second step plane layer; The quartz support base is provided with three functional cavities: The first accommodating cavity is equipped with a fiber collimating lens and a photoacoustic cell, and the output light of the fiber collimating lens is irradiated onto the Fabry-Perot microcantilever diaphragm through the photoacoustic cell; The second accommodating cavity is provided with a first ceramic optical fiber ferrule, the first ceramic optical fiber ferrule is tightly fitted to the rear end of the temperature-sensitive crystal, and the front end of the temperature-sensitive crystal is parallel to the first stepped plane; the output light of the first ceramic optical fiber ferrule is irradiated by the temperature-sensitive crystal and then reflected back to the optical fiber; The third accommodating cavity is provided with a second ceramic optical fiber ferrule. The outgoing light of the ceramic optical fiber ferrule is irradiated by the Fabry-Perot micro-cantilever beam diaphragm and then reflected back to the optical fiber.

[0006] As a preferred technical solution, the optical fiber collimating lens, the first ceramic optical fiber ferrule and the second ceramic optical fiber ferrule are all encapsulated with single-mode optical fibers to form an optical transmission channel.

[0007] As a preferred technical solution, the first ceramic optical fiber ferrule and the second ceramic optical fiber ferrule are made of zirconium oxide ceramic material; The quartz support base is arranged to match the thermal expansion coefficient of the first ceramic optical fiber ferrule to achieve temperature drift self-correction.

[0008] As an optimal technical solution, the Fabry-Perot microcantilever diaphragm comprises a silicon-based cantilever body and a gold film reflective mirror, and a nanoindentation array structure is provided on the surface of the silicon-based cantilever body.

[0009] As a preferred technical solution, the filter-permeable membrane composite structure includes a stacked and fixed porous stainless steel breathable filter and a polymer selective permeable membrane; the porous stainless steel breathable filter has a porosity of 50-70% and a pore size distribution of 5-20 μm; the polymer selective permeable membrane adopts a polytetrafluoroethylene modified membrane.

[0010] As a preferred technical solution, the Fabry-Perot micro-cantilever diaphragm is fixed to the quartz support base by ultraviolet curing adhesive; The UV curing adhesive is an epoxy acrylate type photosensitive adhesive, the refractive index of which after curing is 1.48-1.52, and the glass transition temperature is greater than or equal to 120°C.

[0011] As a preferred technical solution, the photoacoustic cell is a cylindrical cavity with a diameter of 2-3 μm, and the average roughness Ra of the inner surface of the photoacoustic cell is less than or equal to 0.05 μm.

[0012] As an optimal technical solution, a stainless steel protective shell is provided on the outer surface of the quartz support base, an annular vibration isolation buffer lining is provided between the quartz support base and the inner wall of the stainless steel protective shell, and a fixed end cap is provided at the end of the stainless steel protective shell corresponding to the three-level stepped structure.

[0013] As a preferred technical solution, the vibration isolation buffer lining is a preformed silicone-based elastomer bushing with a sawtooth waveform structure in cross section, a Shore hardness of HA50-70, and a compression permanent deformation rate of less than 10%.

[0014] As a second aspect of the present invention, a method for preparing the above-mentioned MEMS optical fiber integrated gas and temperature sensor is provided, which is specifically as follows: For the quartz support base, reactive ion etching is used to form three steps, and three accommodating cavities are processed inside the quartz support base; For the Fabry-Perot microcantilever diaphragm, a double-sided polished SOI silicon wafer is used as the substrate, an array of hexagonal pits is etched on the surface of the cantilever, and a gold reflective layer is plated on the end of the beam using magnetron sputtering; For the filter-permeable membrane composite structure, the porous stainless steel breathable filter is punched to form honeycomb-shaped through-holes, and after electrochemical polishing, a thick titanium nitride wear-resistant layer is plated on the surface; the polymer selective permeable membrane is prepared by electrospinning a blend of polytetrafluoroethylene and perfluorosulfonic acid resin into a composite membrane, and then hot-pressed to shape; In a vacuum glove box, the following steps are performed: a Fabry-Perot microcantilever membrane is fixed to the first step plane using UV-curing adhesive; a porous stainless steel air-permeable filter and a polymer selective permeable membrane are stacked and placed on the second step plane, where they are fused to the interface through hot pressing; UV-curing adhesive is injected into the second receiving cavity, a second ceramic insert for temperature detection is inserted, and the mixture is cured multiple times on a rotary curing table; Embed the optical fiber collimating lens into the first accommodating cavity and calibrate the perpendicularity between the optical axis and the reflecting surface of the cantilever beam; Carve a cylindrical cavity inside the quartz support base, and polish the inner wall of the cylindrical cavity to a set roughness; The preformed silicone-based elastomer vibration isolation buffer liner is inserted into the quartz support base, and then installed into the stainless steel protective shell and pre-tightened. Apply perfluoroether grease to the threaded parts of the stainless steel protective shell and tighten the end cap to the set torque; Perform temperature compensation calibration: Place the sensor in a high and low temperature chamber to record the thermo-optical coefficient change curve of the temperature-sensitive crystal; measure the temperature drift of the resonant frequency of the photoacoustic cell; and write the temperature-frequency compensation algorithm into the FPGA chip.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention proposes a MEMS fiber-optic integrated gas and temperature sensor. Three functional cavities are located within a three-channel quartz base. The first cavity houses a fiber-optic collimating lens and a photoacoustic cell for acoustic pressure signal sensing. The second and third cavities, respectively, house a zirconia ceramic fiber ferrule for temperature detection and a ceramic fiber ferrule for gas / moisture detection. Single-mode optical fibers are encapsulated within the ferrules to form an optical channel. Light emitted from the temperature ceramic fiber ferrule is directed to a temperature-sensing crystal. The thermo-optic effect of the temperature-sensing crystal alters the optical fiber transmission phase. Combined with the temperature dependence of the photoacoustic cell's resonant frequency (temperature sensitivity 0.1 kHz / °C), this enables dual-mode temperature cross-validation. Furthermore, utilizing the water molecule selectivity of the permeable membrane, trace moisture detection is achieved through humidity-induced changes in the FP cavity's refractive index. Through a coupled optical-mechanical-thermal multi-physics design, this invention achieves high-precision multi-parameter detection and environmental robustness at the MEMS scale, providing a next-generation fiber-optic sensing solution for the Industrial Internet of Things.

[0016] 2) The present invention features a multi-level composite sensing structure and environmentally robust packaging design. The quartz support base is 3D-printed from optical-grade quartz material and precision-machined using photolithography. The front end is designed as a three-step structure. The first step plane secures the Fabry-Perot microcantilever membrane, and the deformation of the cantilever causes changes in reflected light to calculate gas concentration. The second step plane secures a porous stainless steel gas-permeable filter and a modified polytetrafluoroethylene permeable membrane to form a selective permeation barrier for gas molecules. The modular structural design, three-channel quartz base, threaded package, and composite filter membrane significantly improve reliability and maintenance efficiency, making it suitable for complex environments and multiple scenarios such as industrial monitoring and medical diagnosis.

[0017] 3) This invention utilizes the viscoelastic damping effect of a sawtooth-shaped lining to dissipate vibration energy into heat. The CTE difference between the quartz support base and the stainless steel protective housing is absorbed by an annular buffer lining (silicon-based elastomer), preventing package cracking caused by temperature cycling. This enables highly sensitive, simultaneous detection of multiple parameters, including gas, temperature, and trace moisture, while offering both vibration immunity and temperature self-calibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 An exploded view of a MEMS fiber optic gas and temperature sensor based on a Fabry-Perot microcantilever provided in an embodiment of the present invention; Figure 2 An exploded right view of a MEMS fiber optic gas and temperature sensor based on a Fabry-Perot microcantilever provided in an embodiment of the present invention; Figure 3 An exploded top view of a MEMS fiber optic gas and temperature sensor based on a Fabry-Perot microcantilever provided in an embodiment of the present invention; Figure 4A three-dimensional diagram of a MEMS fiber optic gas and temperature sensor based on a Fabry-Perot microcantilever provided in an embodiment of the present invention; The numbers in the figure are as follows: 1. Stainless steel protective shell; 2. Vibration isolation buffer lining; 3. Quartz support base; 4. Fiber optic collimating lens; 5. Photoacoustic cell; 6. First ceramic fiber optic ferrule; 7. Second ceramic fiber optic ferrule; 8. Single-mode optical fiber; 9. Temperature-sensing crystal; 10. Acoustic waveguide cavity; 11. Fabry-Perot microcantilever beam diaphragm; 12. Porous stainless steel breathable filter; 13. Polymer selective permeability membrane; 14. Fixed end cap. DETAILED DESCRIPTION

[0019] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0020] Example 1 The present invention aims to solve the technical bottlenecks of existing optical fiber sensors in terms of multi-parameter integration, environmental adaptability and temperature stability, and proposes a MEMS optical fiber gas and temperature integrated sensor based on Fabry-Perot (FP) microcantilever and its packaging method.

[0021] like Figure 1 As shown in the figure, the gas and temperature integrated sensor proposed by the present invention consists of a stainless steel protective housing 1, a vibration isolation buffer liner 2, a quartz support base 3, a fiber collimating lens 4, a photoacoustic cell 5, a first ceramic fiber optic ferrule 6 (temperature), a second ceramic fiber optic ferrule 7 (gas, micro-water), a single-mode optical fiber 8, a temperature-sensitive crystal 9, an acoustic waveguide cavity 10, a Fabry-Perot microcantilever diaphragm 11, a porous stainless steel gas permeable filter 12, a polymer selective permeable membrane 13, and a fixed end cap 14. Figure 2-Figure 3 As shown, the specific configuration is as follows: the front end of the quartz support base 3 is composed of a Fabry-Perot microcantilever beam diaphragm 11, a porous stainless steel air filter 12, and a polymer selective permeation membrane 13, which are fixed with UV curing glue, and the fixed end cap 14 is fixed to the stainless steel protective shell 1 through a threaded structure; The quartz support base 3 is designed with three hollow structures, which serve as the fixing structure and light propagation channel for the optical fiber collimating lens 4, the first ceramic optical fiber ferrule 6 (temperature), and the second ceramic optical fiber ferrule 7 (gas, micro-water). The output light of the optical fiber collimating lens 4 is irradiated onto the Fabry-Perot micro-cantilever diaphragm 11 through the photoacoustic cell 5. The output light of the first ceramic optical fiber ferrule 6 (temperature) is irradiated onto the temperature-sensitive crystal 9 and then reflected back into the optical fiber. The output light of the second ceramic optical fiber ferrule 7 (gas, micro-water) is irradiated onto the Fabry-Perot micro-cantilever diaphragm 11 and then reflected back into the optical fiber. The sensor proposed in the present invention can achieve high-sensitivity simultaneous detection of multiple parameters of gas, temperature, and micro-water, and has the advantages of anti-vibration interference and temperature self-correction. Its modular structural design (three-channel quartz base, threaded packaging, and composite filter membrane) greatly improves reliability and maintenance efficiency, and is suitable for multiple scenarios in complex environments such as industrial monitoring and medical diagnosis. The following is a detailed explanation from three aspects: structural composition, technical principles, and implementation methods: 1. Structural composition and technical means This sensor proposes a multi-level composite sensing structure and environmental robustness packaging design, as follows: Quartz support base 3: Optical grade quartz material (CTE = 0.55 × 10⁻ 6 / ℃) is 3D printed and precision-machined using photolithography technology. The front end is designed as a three-step structure (step height difference 0.2-0.5mm) to achieve a modular layout of functional components.

[0022] First step plane: The Fabry-Perot microcantilever diaphragm 11 is fixed with UV-curing glue. It consists of a silicon-based cantilever body (thickness 100-200μm, with a nanoindentation array on the surface) and a gold film reflective mirror (magnetron sputtering, thickness 1μm). When the detection gas expands in the photoacoustic cell 5, it will cause the cantilever to deform. The gas concentration is calculated by the change in reflected light caused by the deformation of the cantilever.

[0023] Second step plane: A porous stainless steel breathable filter 12 (porosity 50-70%, pore size 5-20 μm) and a polytetrafluoroethylene modified permeable membrane (thickness 50-100 μm) are fixed by laminating with UV curing adhesive, which not only forms a selective permeation barrier for gas molecules but also plays a role in isolating pollution.

[0024] Among them, the UV curing adhesive adopts epoxy acrylate type photosensitive adhesive, the refractive index of which after curing is 1.48-1.52 and the glass transition temperature is ≥120℃.

[0025] Three functional cavities are set up inside: The first chamber houses a fiber collimating lens 4 (to improve beam coupling efficiency) and a photoacoustic cell 5 for acoustic pressure signal sensing. The cell 5 is a cylindrical cavity with a diameter of 2-3 μm, its inner surface chemically polished to a surface roughness of Ra ≤ 0.05 μm. The gas being detected enters the cell through a polymeric selective permeable membrane 13, where it is excited by the photoacoustic spectroscopy effect.

[0026] The second and third cavities house a first zirconia ceramic fiber ferrule 6 (temperature detection) and a second ceramic fiber ferrule 7 (gas / moisture detection), respectively. The ferrule end faces are polished (to a tolerance of ±0.5μm). A single-mode optical fiber 8 is encapsulated within the ferrule to form an optical channel. Light emitted from the first ceramic fiber ferrule 6 (temperature) is directed to a temperature-sensing crystal 9. Because the gallium arsenide temperature-sensing crystal absorbs incident light of varying wavelengths at different temperatures, unabsorbed wavelengths are reflected back to the device. By analyzing the spectrum of the reflected light, the temperature parameter at the probe can be determined.

[0027] The first ceramic fiber optic ferrule 6 (temperature) and the second ceramic fiber optic ferrule 7 (gas, trace water) are made of zirconia ceramic material. Their end faces are polished into flat surfaces without tilt angles. The outer diameter tolerance of the ferrule is controlled within the range of ±0.5μm. The first ceramic fiber optic ferrule 6 (temperature) is tightly fitted to the rear end of the temperature-sensing crystal 9, and the front end of the temperature-sensing crystal 9 is parallel to the first step plane.

[0028] Environmental protection system: Stainless steel protective shell 1: connected to the fixed end cap 14 through precision threads (IP65 waterproof), a sawtooth corrugated vibration isolation buffer lining 2 (Shore hardness HA50-70, compression deformation rate <10%) is set between the shell and the quartz base, which can attenuate mechanical vibration by more than 80%.

[0029] Temperature control compensation structure: The temperature sensing crystal 9 is tightly fitted with the temperature detection insert, and the thermal expansion coefficient is matched (quartz - CTE 0.55×10⁻ 6 / ℃ vs Zirconia-CTE 10.5×10⁻ 6 / ℃) to achieve temperature drift self-correction.

[0030] 2. Technical Principles and Innovative Concepts Multi-parameter detection coordination mechanism: Gas detection: Target gas molecules are filtered through a permeable membrane and enter the acoustic cavity. By irradiating light of different wavelengths, the corresponding gas molecules absorb the light energy and expand (photoacoustic spectroscopy effect), causing the beam to bend and the FP cavity length to change (sensitivity 0.15nm / μg·m⁻³). The gas concentration is inverted by the displacement of the reflected light interference fringes.

[0031] Temperature detection: The thermo-optical effect of the temperature-sensing crystal 9 changes the optical fiber transmission phase. Combined with the temperature dependence of the resonant frequency of the photoacoustic cell 5 (temperature sensitivity 0.1kHz / °C), dual-mode temperature cross-validation is achieved.

[0032] Trace moisture detection: Utilizing the water molecule selectivity of the permeable membrane, trace moisture detection is achieved through the change in the FP cavity refractive index caused by humidity (resolution 0.1ppm).

[0033] Principle of environmental interference suppression: Vibration suppression: The viscoelastic damping effect of the sawtooth corrugated vibration isolation buffer lining 2 can convert 20-2000Hz vibration energy into heat energy dissipation (vibration transmission rate <5%).

[0034] Thermal stress relief: The CTE difference between the quartz support base 3 and the stainless steel protective shell 1 is absorbed by the annular vibration isolation buffer liner 2 (silicon-based elastomer), avoiding cracking of the packaging structure caused by temperature cycling.

[0035] 3. Implementation Methods and Technical Effects Packaging process: Complete the following in a vacuum glove box (humidity <10% RH): a) UV curing positioning of microcantilever (365nm light source, irradiation intensity 15mW / cm²); b) Hot pressing of filter disc and permeable membrane (temperature 120°C, pressure 5 MPa, holding pressure 30 seconds); c) Rotary curing and packaging of the optical fiber ferrule (rotation speed 30 rpm, curing in three steps to reduce internal stress).

[0036] Performance indicators: Detection range: Gas is generally 0-10000ppm (resolution can reach 1ppm), temperature -40~150℃ (accuracy ±0.1℃), trace water 0-50ppm (error ±2%).

[0037] Environmental adaptability: Signal drift <1%FS when working for a long time under 5g vibration and 85%RH humidity.

[0038] 4. Differences from existing technologies Structural Innovation: The stepped quartz support base 3 enables integrated detection of three parameters: gas, temperature, and trace moisture (traditional solutions require three independent sensors). The sawtooth-shaped vibration isolation buffer liner 2 overcomes the vibration suppression bottleneck of traditional O-ring seals (vibration attenuation is increased by three times).

[0039] Material innovation: PTFE-modified permeable membranes (gas selectivity coefficient > 100) offer significantly improved performance compared to traditional PDMS membranes (coefficient ≈ 20). UV-curable adhesives (Tg ≥ 120°C) address the high-temperature creep issue of traditional epoxy resin adhesives (Tg ≈ 80°C).

[0040] Through the optical-mechanical-thermal multi-physics field coupling design, the present invention achieves the unification of high-precision multi-parameter detection and environmental robustness on the MEMS scale, providing a new generation of fiber optic sensing solutions for the Industrial Internet of Things.

[0041] Example 2 The following describes in detail the preferred embodiment of the present invention in conjunction with the accompanying drawings. This example uses the synchronous monitoring of SF6 gas concentration and transformer oil temperature as an application scenario to demonstrate the specific preparation process of the sensor: 1. Preparation of core components 1.1. Quartz support base 3 processing Material: JGS2 grade optical quartz glass (purity>99.99%, CTE=0.55×10⁻ 6 / ℃).

[0042] Processing steps: Step 1.1.1: Define a staircase structure pattern on the surface of the quartz substrate using a photolithography process. Use reactive ion etching (RIE) to form three steps (step height difference 0.3 mm, transition surface inclination angle 45° ± 1°).

[0043] Step 1.1.2: Use an ultra-precision drilling machine to process the inside of the base: The first accommodating cavity (3.2 mm in diameter): used to install the optical fiber collimating lens 4 and the photoacoustic cell 5; The second accommodating cavity (diameter 2.0 mm): fixed with the first ceramic optical fiber ferrule 6 for temperature detection; The third accommodating cavity (diameter 2.5 mm): for positioning the second ceramic optical fiber ferrule 7 for gas / micro-water detection.

[0044] Step 1.1.3: Surface polishing: Chemical mechanical polishing (CMP) is used to reduce the surface roughness of the substrate to Ra < 0.01 μm.

[0045] 1.2. Fabrication of Fabry-Perot Microcantilever Diaphragm Substrate: Double-sided polished 4-inch SOI silicon wafer (device layer thickness 150μm, buried oxide layer 2μm).

[0046] Process flow: Step 1.2.1: Nanoindentation processing: A hexagonal pit array (depth 200 nm) with a period of 500 nm was etched on the cantilever surface using a focused ion beam (FIB).

[0047] Step 1.2.2: Gold film deposition: Use magnetron sputtering to deposit a 1 μm thick gold reflective layer (reflectivity > 95% at 1550 nm) on the end of the beam.

[0048] Step 1.2.3: Release process: Remove the back silicon substrate by XeF2 vapor phase etching, leaving the cantilever beam structure (size: 2 mm long × 0.5 mm wide × 150 μm thick).

[0049] 1.3. Filter-permeable membrane composite structure Porous stainless steel breathable filter 12: Material: 316L stainless steel, laser punched to form honeycomb holes with a pore size of 10±2μm (porosity 60%).

[0050] Post-processing: electrochemical polishing to eliminate burrs, and 3μm thick titanium nitride wear-resistant layer is plated on the surface.

[0051] Polymer selective permeable membrane 13: Raw materials: polytetrafluoroethylene (PTFE) and perfluorosulfonic acid resin (mass ratio 7:3) blend solution.

[0052] Film forming process: A composite film with a thickness of 80 μm was prepared by electrospinning and then hot-pressed at 180 °C for shaping.

[0053] 2. Sensor Assembly 2.1. Vacuum environment assembly Assemble in the following order in a nitrogen-filled glove box (humidity <8% RH, oxygen content <10 ppm): Step 2.1.1: Place the Fabry-Perot microcantilever membrane 11 on the first step plane, apply epoxy acrylate UV adhesive (Norland NOA81, refractive index 1.51), and cure it using a 365 nm UV light source (intensity 20 mW / cm²) for 60 seconds.

[0054] Step 2.1.2: After overlapping the filter disc and the permeable membrane, place them on the second step plane, apply a pressure of 5 MPa and hot press at 120°C for 30 seconds to achieve interface fusion.

[0055] Step 2.1.3: Inject UV glue into the third cavity, insert the ceramic ferrule for temperature detection, and cure it in three steps (10 seconds each time, followed by 2 minutes of stress release) on a rotary curing station (20 rpm).

[0056] 2.2. Optical system integration Installation of fiber collimating lens 4: embed the gradient refractive index lens (GRIN lens, focal length 2 mm) into the first accommodation cavity, and calibrate the perpendicularity between the optical axis and the cantilever beam reflection surface using a six-axis adjustment frame (error <0.1°).

[0057] Photoacoustic cell 5 processing: A cylindrical cavity with a diameter of 2.5 μm was engraved inside the quartz base using a femtosecond laser, and the inner wall was polished to Ra = 0.03 μm using hydrofluoric acid vapor.

[0058] 2.3. Protection system packaging Installation of the vibration isolation lining: Insert the preformed silicone-based elastomer bushing (Shore hardness HA60, serration depth 0.5mm) into the quartz base, install it into the stainless steel housing, and apply a 5N preload force.

[0059] End cap sealing: Apply perfluoroether grease to the threaded part of the housing and tighten the end cap 14 to a torque of 0.8 N·m to achieve IP65 grade sealing.

[0060] 3. Calibration and testing 3.1. Temperature compensation calibration Place the sensor in a high and low temperature box (-40℃~150℃) and establish a compensation model through the following steps: Step 3.1.1: Record the thermo-optical coefficient change curve (dλ / dT = 0.01 nm / °C) of the temperature-sensitive crystal (material: LiNbO3).

[0061] Step 3.1.2: Measure the temperature drift of the resonant frequency of the photoacoustic cell 5 (Δf = 12 Hz / °C).

[0062] Step 3.1.3: Write the temperature-frequency compensation algorithm into the FPGA chip to achieve a temperature measurement accuracy of ±0.05°C.

[0063] 3.2. Gas sensitivity test Calibration using standard SF6 gas (concentration 0-1000ppm): Step 3.2.1: Introduce different gas concentrations and record the deflection of the microcantilever (resolution 0.1 nm) and the movement of the interference fringes.

[0064] Step 3.2.2: Construct a concentration-wavelength shift curve (sensitivity 0.18 nm / ppm, linearity R² > 0.999).

[0065] Step 3.2.3: Verify membrane selectivity: cross sensitivity to CH4 and CO2 is <0.5%.

[0066] 3.3. Vibration interference test Performed on an electromagnetic vibration table (frequency 20-2000 Hz, acceleration 5g): Step 3.3.1: Compare the signal fluctuations before and after installing the vibration isolation lining: the fluctuation amplitude is ±3% without vibration isolation, and it drops to ±0.5% after vibration isolation.

[0067] Step 3.2.2: After 8 hours of continuous vibration, check the fiber coupling loss: the insertion loss change should be less than 0.2 dB.

[0068] Those skilled in the art will appreciate that other similar connection methods may also be used to implement the present invention, such as welding, bonding, or screwing.

[0069] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A MEMS optical fiber gas and temperature integrated sensor, characterized in that: It comprises a quartz support base (3), one end of which is provided with a three-step structure, wherein a Fabry-Perot micro-cantilever beam membrane (11) is fixed on the first step plane, and a filter-permeable membrane composite structure is fixed on the second step plane layer; The quartz support base (3) is provided with three functional cavities inside: The first accommodating cavity is provided with a fiber collimating lens (4) and a photoacoustic cell (5), wherein the output light of the fiber collimating lens (4) is irradiated onto the Fabry-Perot microcantilever diaphragm (11) through the photoacoustic cell (5); The second accommodating cavity is provided with a first ceramic optical fiber ferrule (6), the first ceramic optical fiber ferrule (6) is tightly fitted to the rear end of the temperature-sensitive crystal (9), and the front end of the temperature-sensitive crystal (9) is parallel to the first step plane; the outgoing light of the first ceramic optical fiber ferrule (6) is irradiated by the temperature-sensitive crystal (9) and then reflected back to the optical fiber; The third accommodating cavity is provided with a second ceramic optical fiber ferrule (7), and the outgoing light of the second ceramic optical fiber ferrule (7) is irradiated onto the center of the cantilever beam end on the Fabry-Perot micro-cantilever beam diaphragm (11) and then reflected back to the optical fiber.

2. A MEMS optical fiber integrated gas and temperature sensor according to claim 1, characterized in that: The optical fiber collimating lens (4), the first ceramic optical fiber ferrule (6) and the second ceramic optical fiber ferrule (7) are all encapsulated with a single-mode optical fiber (8) to form an optical transmission channel.

3. The MEMS optical fiber integrated gas and temperature sensor according to claim 1, characterized in that: The first ceramic optical fiber ferrule (6) and the second ceramic optical fiber ferrule (7) are made of zirconium oxide ceramic material; The thermal expansion coefficients of the quartz support base (3) and the first ceramic optical fiber ferrule (6) are matched to achieve temperature drift self-correction.

4. The MEMS optical fiber integrated gas and temperature sensor according to claim 1, characterized in that: The Fabry-Perot microcantilever diaphragm (11) comprises a silicon-based cantilever main body and a gold film reflective mirror surface, and a nano-indentation array structure is provided on the surface of the silicon-based cantilever main body.

5. The MEMS optical fiber integrated gas and temperature sensor according to claim 1, characterized in that: The filter-permeable membrane composite structure comprises a stacked and fixed porous stainless steel air permeable filter (12) and a polymer selective permeable membrane (13); the porous stainless steel air permeable filter (12) has a porosity of 50-70% and a pore size distribution of 5-20 μm; the polymer selective permeable membrane (13) is a polytetrafluoroethylene modified membrane.

6. The MEMS optical fiber integrated gas and temperature sensor according to claim 1, characterized in that: The Fabry-Perot micro-cantilever diaphragm (11) is fixed to the quartz support base (3) via ultraviolet curing adhesive; The UV curing adhesive is an epoxy acrylate type photosensitive adhesive, the refractive index of which after curing is 1.48-1.52, and the glass transition temperature is greater than or equal to 120°C.

7. The MEMS optical fiber integrated gas and temperature sensor according to claim 1, characterized in that: The photoacoustic cell (5) is a cylindrical cavity with a diameter of 2-3 μm, and the average roughness Ra of the inner surface of the photoacoustic cell (5) is less than or equal to the surface roughness of 0.05 μm.

8. The MEMS optical fiber integrated gas and temperature sensor according to claim 1, characterized in that: The outer surface of the quartz support base (3) is provided with a stainless steel protective shell (1), an annular vibration isolation buffer lining (2) is provided between the quartz support base (3) and the inner wall of the stainless steel protective shell (1), and a fixed end cap (14) is provided at one end of the stainless steel protective shell (1) corresponding to the three-step structure.

9. The MEMS optical fiber integrated gas and temperature sensor according to claim 8, characterized in that: The vibration isolation buffer lining (2) is a preformed silicon-based elastomer bushing with a sawtooth waveform structure in cross section, a Shore hardness of HA50-70, and a compression permanent deformation rate of less than 10%.

10. A method for preparing a MEMS optical fiber integrated gas and temperature sensor according to any one of claims 1 to 9, characterized in that: The details are as follows: For the quartz support base (3), reactive ion etching is used to form three steps, and three accommodating cavities are processed inside the quartz support base (3); For the Fabry-Perot microcantilever diaphragm (11), a double-sided polished SOI silicon wafer was used as the substrate, a hexagonal pit array was etched on the cantilever surface, and a gold reflective layer was plated on the end of the beam by magnetron sputtering; For the filter-permeable membrane composite structure, a porous stainless steel air-permeable filter (12) is punched to form honeycomb-shaped through-holes, and after electrochemical polishing, a thick titanium nitride wear-resistant layer is plated on the surface; a polymer selective permeable membrane (13) is prepared by electrostatic spinning a mixed solution of polytetrafluoroethylene and perfluorosulfonic acid resin into a composite membrane, and then hot-pressed to shape; The following steps are carried out in a vacuum glove box: fixing the Fabry-Perot microcantilever beam membrane (11) on the first step plane by means of UV curing adhesive; laminating the porous stainless steel air permeable filter (12) and the polymer selective permeable membrane (13) and placing them on the second step plane, and fusing them with the interface by means of hot pressing; injecting UV curing adhesive into the second receiving cavity, inserting the second ceramic insert for temperature detection, and curing them multiple times by means of a rotating curing table; Embed the optical fiber collimating lens (4) into the first accommodating cavity to calibrate the verticality between the optical axis and the cantilever beam reflection surface; Carving a cylindrical cavity inside the quartz support base (3), and polishing the inner wall of the cylindrical cavity to a set roughness; The preformed silicon-based elastomer vibration isolation buffer lining (2) is inserted into the quartz support base (3), and then installed into the stainless steel protective shell (1) and a pre-tightening force is applied; Apply perfluoroether grease to the threaded portion of the stainless steel protective housing (1), and tighten the fixed end cap (14) to the set torque; Perform temperature compensation calibration: place the sensor in a high and low temperature box to record the thermo-optical coefficient change curve of the temperature-sensitive crystal (9); measure the temperature drift of the resonant frequency of the photoacoustic cell (5); and write the temperature-frequency compensation algorithm into the FPGA chip.

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