A MEMS fiber optic gas and temperature integrated sensor and a method of manufacturing the same

Abstract

The application relates to the technical field of optical fiber sensors, in particular to a MEMS optical fiber gas and temperature integrated sensor and a preparation method thereof, a three-stage ladder structure is arranged at one end of a quartz support base, a F-P micro-cantilever beam diaphragm is fixed on a first ladder plane, and a filter-permeation membrane composite structure is arranged on a second ladder plane layer; three function cavities are arranged in the quartz support base: a fiber collimating lens and an optical sound cell are arranged in a first accommodating cavity, the outgoing light of the fiber collimating lens is irradiated onto the F-P micro-cantilever beam diaphragm through the optical sound cell; a first ceramic fiber ferrule is arranged in a second accommodating cavity, the fiber ferrule is tightly attached to the rear end of a temperature sensing crystal, and the front end of the temperature sensing crystal is parallel to the first ladder plane; a second ceramic fiber ferrule is arranged in a third accommodating cavity, and the outgoing light of the fiber ferrule is reflected back to the fiber after irradiating onto the F-P micro-cantilever beam diaphragm. The gas, temperature and micro-water multi-parameter high-sensitivity synchronous detection is realized, and the anti-vibration interference advantage is achieved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of MEMS fiber sensors, in particular to a MEMS fiber gas and temperature integrated sensor based on a Fabry-Perot (F-P) micro cantilever beam. BACKGROUND

[0002] The fiber gas and temperature integrated sensor belongs to the technical field of precise optical sensing, and is mainly applied to industrial process monitoring (such as SF6 gas detection of power equipment), environmental monitoring (atmospheric pollutant analysis), medical equipment (anesthetic gas concentration monitoring), smart grid (micro water detection in transformer oil) and aerospace (propellant leakage monitoring) and the like. With the development of the Internet of Things and industrial 4.0, the market has a growing demand for multi-parameter sensors with high sensitivity, anti-electromagnetic interference and remote monitoring. The current mainstream technologies in the field of fiber sensing include fiber grating technology (temperature / strain measurement through Bragg wavelength shift, but the gas sensitivity is insufficient and an external sensitive film is needed for assistance), Fabry-Perot interference technology (pressure / temperature measurement through air cavity length change, but there is a temperature-stress cross-sensitivity problem) and micro cantilever beam technology (gas adsorption through beam bending detection, but the MEMS package is easily disturbed by mechanical vibration).

[0003] However, the prior art has the following defects: firstly, the multi-parameter detection capability is insufficient, for example, the Honeywell HGS series adopts a discrete sensor group, resulting in a large system volume (>200 cm3) and high cost (>500 US dollars / set); secondly, the environmental adaptability is defective, the traditional packaging structure (such as Siemens SIP packaging) causes fiber coupling failure due to the creep of adhesive and the mismatch of the thermal expansion coefficients of metal and glass under strong vibration (>5g) and high humidity (>85%RH) working conditions; thirdly, the temperature drift problem, the temperature error of the Omron D6T series reaches ±2%FS / ℃, which is mainly due to the insufficient thermal stability of the glass transition temperature (Tg≈250℃) of the sensitive material (such as polyimide). SUMMARY

[0004] The application aims to overcome the technical bottlenecks of the prior art fiber sensor in multi-parameter integration, environmental adaptability and temperature stability, and provides a MEMS fiber gas and temperature integrated sensor based on a Fabry-Perot (F-P) micro cantilever beam and a packaging method thereof.

[0005] The object of the application can be achieved by the following technical solutions:

[0006] As a first aspect of the present application, a MEMS fiber gas and temperature integrated sensor is provided, comprising a quartz support base provided with a three-stage stepped structure at one end, wherein a first stepped plane is fixed with a F-P micro-cantilever beam diaphragm, and a second stepped plane layer is fixed with a filter-permeable membrane composite structure;

[0007] The quartz support base is internally provided with three functional cavities:

[0008] A first accommodating cavity is provided with a fiber collimating lens and an optoacoustic cell, and the outgoing light of the fiber collimating lens is irradiated onto the F-P micro-cantilever beam diaphragm through the optoacoustic cell;

[0009] A second accommodating cavity is provided with a first ceramic fiber ferrule, which is tightly attached to the rear end of a temperature sensing crystal, and the front end of the temperature sensing crystal is parallel to the first stepped plane; the outgoing light of the first ceramic fiber ferrule is irradiated onto the temperature sensing crystal and reflected back to the fiber;

[0010] A third accommodating cavity is provided with a second ceramic fiber ferrule, and the outgoing light of the second ceramic fiber ferrule is irradiated onto the F-P micro-cantilever beam diaphragm and reflected back to the fiber.

[0011] As a preferred technical solution, the fiber collimating lens, the first ceramic fiber ferrule and the second ceramic fiber ferrule are all internally encapsulated with single-mode optical fibers to form optical transmission channels.

[0012] As a preferred technical solution, the first ceramic fiber ferrule and the second ceramic fiber ferrule are made of zirconia ceramic material.

[0013] The quartz support base and the first ceramic fiber ferrule are matched in terms of thermal expansion coefficient to realize temperature drift self-correction.

[0014] As a preferred technical solution, the F-P micro-cantilever beam diaphragm comprises a silicon-based cantilever beam body and a gold film mirror surface, and the surface of the silicon-based cantilever beam body is provided with a nano-indentation array structure.

[0015] As a preferred technical solution, the filter-permeable membrane composite structure comprises a porous stainless steel air-permeable filter and a high-molecular selective permeable membrane which are stacked and fixed; the porosity of the porous stainless steel air-permeable filter is 50-70%, and the pore size distribution is 5-20 μm; the high-molecular selective permeable membrane is a polytetrafluoroethylene modified membrane.

[0016] As a preferred technical solution, the F-P micro-cantilever beam diaphragm is fixed to the quartz support base by ultraviolet curing glue.

[0017] The ultraviolet curing glue is an epoxy acrylate type photosensitive glue, and after curing, the refractive index is 1.48-1.52, and the glass transition temperature is greater than or equal to 120℃.

[0018] As a preferred technical solution, the photoacoustic cell is a cylindrical cavity with a diameter of 2-3 um, and the average roughness Ra of the inner surface of the photoacoustic cell is less than or equal to 0.05 um.

[0019] As a preferred technical solution, the outer surface of the quartz support base is provided with a stainless steel protective shell, and an annular vibration isolation buffer layer is arranged between the quartz support base and the inner wall of the stainless steel protective shell. The stainless steel protective shell is provided with a fixed end cap at one end corresponding to the three-stage stepped structure.

[0020] As a preferred technical solution, the vibration isolation buffer layer 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 set of less than 10%.

[0021] As a second aspect of the present application, a preparation method of the MEMS optical fiber gas and temperature integrated sensor is provided, and the preparation method is as follows:

[0022] For the quartz support base, a three-stage step is formed by reactive ion etching, and three accommodating cavities are processed inside the quartz support base;

[0023] For the Fabry-Perot micro-cantilever beam diaphragm, a double-side polished SOI silicon wafer is used as a substrate, a hexagonal pit array is etched on the surface of the cantilever beam, and a gold reflecting layer is plated on the end of the beam by magnetron sputtering;

[0024] For the filter-membrane composite structure, a porous stainless steel air-permeable filter is formed into a honeycomb-shaped through hole by punching, and after electrochemical polishing, a thick titanium nitride wear-resistant layer is plated on the surface; a high-molecular selective permeation membrane is prepared into a composite membrane by electrospinning a polytetrafluoroethylene and perfluorosulfonic acid resin blended solution, and is heat-pressed and shaped;

[0025] In a vacuum glove box, the following steps are sequentially performed: the Fabry-Perot micro-cantilever beam diaphragm is fixed on the first step plane by ultraviolet curing glue; the porous stainless steel air-permeable filter and the high-molecular selective permeation membrane are superimposed and placed on the second step plane, and are fused with the interface by heat pressing; ultraviolet curing glue is injected into the second accommodating cavity, a second ceramic plug for temperature detection is inserted, and curing is performed multiple times by a rotary curing table;

[0026] The optical fiber collimating lens is embedded into the first accommodating cavity, and the perpendicularity of the optical axis and the cantilever beam reflecting surface is calibrated;

[0027] The cylindrical cavity is engraved inside the quartz support base, and the inner wall of the cylindrical cavity is polished to a specified roughness;

[0028] The preformed silicon-based elastomer vibration isolation buffer layer is sleeved into the quartz support base, and a pre-tightening force is applied after being loaded into the stainless steel protective shell;

[0029] Coat the threaded part of the stainless steel protective shell with perfluoroether lubricating grease, and screw the fixed end cap to the set torque;

[0030] Temperature compensation calibration is performed: the sensor is placed in a high-low temperature chamber to record the thermal-optical coefficient change curve of the temperature sensing crystal; the temperature drift of the resonance frequency of the photoacoustic cell is measured; and a temperature-frequency compensation algorithm is written in the FPGA chip.

[0031] Compared with the prior art, the present application has the following beneficial effects:

[0032] 1) The present application proposes a MEMS fiber-optic gas and temperature integrated sensor, three functional cavities are arranged in the three-channel quartz support base: a first accommodating cavity installs a fiber collimating lens and a photoacoustic cell, which are used for sensing sound pressure signals; a second and a third accommodating cavity respectively install a temperature detection zirconia ceramic fiber ferrule and a gas / micro-water detection ceramic fiber ferrule, a single-mode optical fiber is packaged in the ferrule to form an optical channel, and the emitted light of the temperature ceramic fiber ferrule irradiates a temperature sensing crystal. The thermo-optic effect of the temperature sensing crystal changes the phase of the fiber transmission, and the temperature dependence of the resonance frequency of the photoacoustic cell (temperature sensitivity 0.1 kHz / ℃) is combined to realize double-mode temperature cross verification. And by using the water molecule selectivity of the permeation membrane, the micro-water detection is realized by the refractive index change of the F-P cavity caused by humidity. The present application realizes the unification of high-precision multi-parameter detection and environmental robustness on the MEMS scale through the design of light-mechanical-thermal multi-physical field coupling, and provides a new generation of fiber-optic sensing solution for industrial Internet of Things.

[0033] 2) The present application has a multi-level composite sensing structure and an environmental robustness packaging design, the quartz support base is 3D printed from optical-grade quartz material and precisely processed using photolithography technology, and the front end is designed as a three-level stepped structure; a first stepped plane fixes a Fabry-Perot micro cantilever beam film, and the deformation of the cantilever beam causes the change of reflected light to calculate the gas concentration. A second stepped plane fixes a porous stainless steel air permeable filter and a polytetrafluoroethylene modified permeation membrane to form a gas molecule selective permeation barrier. Through the modular structure design, the three-channel quartz base, threaded packaging and composite filter membrane greatly improve the reliability and maintenance efficiency, and are suitable for complex environmental multi-scene requirements such as industrial monitoring and medical diagnosis.

[0034] 3) The present application uses the viscoelastic damping effect of the sawtooth waveform lining layer to convert vibration energy into heat energy dissipation; the CTE difference between the quartz support base and the stainless steel protective shell is absorbed by the annular buffer lining (silicon-based elastomer), avoiding the cracking of the packaging structure caused by temperature cycling. The present application realizes the high-sensitivity synchronous detection of gas, temperature and micro-water multi-parameters, and has the advantages of anti-vibration interference and temperature self-correction. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1A decomposition view of a MEMS fiber gas and temperature sensor based on a Fabry-Perot micro cantilever beam is provided for an embodiment of the present application.

[0036] Figure 2 A decomposition right view of a MEMS fiber gas and temperature sensor based on a Fabry-Perot micro cantilever beam is provided for an embodiment of the present application.

[0037] Figure 3 A decomposition top view of a MEMS fiber gas and temperature sensor based on a Fabry-Perot micro cantilever beam is provided for an embodiment of the present application.

[0038] Figure 4 A perspective view of a MEMS fiber gas and temperature sensor based on a Fabry-Perot micro cantilever beam is provided for an embodiment of the present application.

[0039] The figure shows: 1, a stainless steel protective shell; 2, a vibration isolation buffer layer; 3, a quartz support base; 4, a fiber collimating lens; 5, a photoacoustic cell; 6, a first ceramic fiber ferrule; 7, a second ceramic fiber ferrule; 8, a single-mode optical fiber; 9, a temperature sensing crystal; 10, an acoustic waveguide cavity; 11, a Fabry-Perot micro cantilever beam diaphragm; 12, a porous stainless steel air permeable filter; 13, a high molecular selective permeation membrane; 14, a fixed end cap. DETAILED DESCRIPTION

[0040] The present application will be described in detail below with reference to the accompanying drawings and specific embodiments. The present embodiment is implemented on the basis of the technical solution of the present application, and gives a detailed implementation and specific operation process, but the protection scope of the present application is not limited to the following embodiments.

[0041] Embodiment 1

[0042] The present application aims to solve the technical bottlenecks of existing fiber sensors in multi-parameter integration, environmental adaptability and temperature stability, and proposes a MEMS fiber gas and temperature integrated sensor based on a Fabry-Perot (F-P) micro cantilever beam and a packaging method thereof.

[0043] As shown in Figure 1 The gas and temperature integrated sensor proposed by the present application is composed of a stainless steel protective shell 1, a vibration isolation buffer layer 2, a quartz support base 3, a fiber collimating lens 4, a photoacoustic cell 5, a first ceramic fiber ferrule 6 (temperature), a second ceramic fiber ferrule 7 (gas, micro water), a single-mode optical fiber 8, a temperature sensing crystal 9, an acoustic waveguide cavity 10, a Fabry-Perot micro cantilever beam diaphragm 11, a porous stainless steel air permeable filter 12, a high molecular selective permeation membrane 13, and a fixed end cap 14. Figures 2-3As shown, it is specifically set as follows: the front end of the quartz support base 3 is provided with a Fabry-Perot micro-cantilever beam diaphragm 11, a porous stainless steel air-permeable filter 12 and a high-molecular selective permeation membrane 13, which are fixed by using ultraviolet curing glue, and a fixed end cap 14 is fixed on the stainless steel protective shell 1 through a threaded structure;

[0044] The quartz support base 3 is internally designed with three hollow structures, which are respectively used as fixing structures and light propagation channels of a fiber collimating lens 4, a first ceramic fiber ferrule 6 (temperature) and a second ceramic fiber ferrule 7 (gas and micro water); the outgoing light of the fiber collimating lens 4 is irradiated onto the Fabry-Perot micro-cantilever beam diaphragm 11 through the photoacoustic cell 5; the outgoing light of the first ceramic fiber ferrule 6 (temperature) is irradiated onto the temperature-sensing crystal 9 and then reflected back to the fiber; and the outgoing light in the second ceramic fiber ferrule 7 (gas and micro water) is irradiated onto the Fabry-Perot micro-cantilever beam diaphragm 11 and then reflected back to the fiber. The sensor proposed in the application can realize high-sensitivity synchronous detection of gas, temperature and micro water, and has the advantages of anti-vibration interference and temperature self-correction; the modular structure design (three-channel quartz base, threaded packaging and composite filter membrane) greatly improves the reliability and maintenance efficiency, and is suitable for complex environment multi-scene requirements such as industrial monitoring and medical diagnosis. The following will be specifically described from three aspects of structure composition, technical principle and implementation mode:

[0045] I. Structure composition and technical means

[0046] The sensor proposes a multi-level composite sensing structure and environmental robust packaging design, which is specifically as follows:

[0047] Quartz support base 3: made of optical-grade quartz material (CTE=0.55×10⁻ 6 / ℃) by 3D printing and precisely processed by photolithography technology, and the front end is designed as a three-step structure (step height difference 0.2-0.5mm), realizing modular layout of functional components.

[0048] First step plane: the Fabry-Perot micro-cantilever beam diaphragm 11 is fixed by ultraviolet curing glue, which is composed of a silicon-based cantilever beam main body (thickness 100-200μm, provided with a nano-indentation array on the surface) and a gold film mirror surface (magnetron sputtering plating, thickness 1μm), when the detected gas expands in the photoacoustic cell 5, the deformation of the cantilever beam will be caused, and the change of the reflected light caused by the deformation of the cantilever beam is used to calculate the gas concentration.

[0049] Second step plane: the porous stainless steel air-permeable filter 12 (porosity 50-70%, pore size 5-20μm) and the polytetrafluoroethylene modified permeation membrane (thickness 50-100μm) are fixed by ultraviolet curing glue layering, which not only forms a gas molecule selective permeation barrier, but also can isolate pollution.

[0050] The ultraviolet curing adhesive is an epoxy acrylate type photosensitive adhesive, and has a refractive index of 1.48-1.52 and a glass transition temperature of greater than or equal to 120 DEG C after curing.

[0051] Three functional cavities are arranged inside:

[0052] The first accommodating cavity is provided with a fiber collimating lens 4 (for improving the light beam coupling efficiency) and a photoacoustic cell 5 for sensing sound pressure signals.

[0053] The second and third accommodating cavities are respectively provided with a zirconia first ceramic fiber ferrule 6 (for temperature detection) and a second ceramic fiber ferrule 7 (for gas / micro-water detection), the end face of the ferrule is ground into a plane (with a tolerance of ±0.5 um), a single-mode optical fiber 8 is packaged inside to form an optical channel, the outgoing light of the first ceramic fiber ferrule 6 (for temperature detection) irradiates a temperature sensing crystal 9, and the temperature sensing crystal 9 is made of gallium arsenide material which can absorb incident light of different wavelengths at different temperatures, and the light of wavelengths not absorbed is reflected back to the device. By analyzing the spectrum of the reflected light, the temperature parameter at the probe can be obtained.

[0054] The first ceramic fiber ferrule 6 (for temperature detection) and the second ceramic fiber ferrule 7 (for gas / micro-water detection) are made of zirconia ceramic material, the end face is ground into a plane without inclination angle, the outer diameter tolerance of the ferrule is controlled within ±0.5 um, the first ceramic fiber ferrule 6 (for temperature detection) is tightly attached 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 stepped plane.

[0055] Environmental protection system:

[0056] The stainless steel protective shell 1 is connected with the fixed end cap 14 through a precision thread (IP65 waterproof), a sawtooth wave vibration isolation buffer layer 2 (Shao hardness HA50-70, compression deformation rate <10%) is arranged between the shell and the quartz base, and the mechanical vibration can be attenuated by more than 80%.

[0057] Temperature control compensation structure: the temperature sensing crystal 9 is tightly attached to the temperature detection ferrule, and the temperature drift self-correction is realized through the thermal expansion coefficient matching design (quartz-CTE 0.55x10⁻ 6 / ℃ vs zirconia-CTE 10.5x10⁻ 6 / ℃).

[0058] II. Technical principles and innovative ideas

[0059] Multi-parameter detection coordination mechanism:

[0060] Gas detection: target gas molecules enter the sound guide cavity after being screened by the permeable membrane, and the corresponding gas molecules absorb the energy of the light irradiated by selecting different wavelengths (photoacoustic spectroscopy effect), causing the beam to bend and change the F-P cavity length (sensitivity 0.15 nm / μg·m⁻³), and the gas concentration is inversely calculated by the displacement of the reflected light interference fringes.

[0061] Temperature detection: the thermo-optic effect of the temperature sensing crystal 9 changes the optical fiber transmission phase, combined with the temperature dependence of the resonance frequency of the photoacoustic cell 5 (temperature sensitivity 0.1 kHz / ℃), to realize double-mode temperature cross verification.

[0062] Micro-water detection: using the water molecule selectivity of the permeable membrane, the F-P cavity refractive index change caused by humidity (resolution 0.1 ppm) is used to realize micro-water detection.

[0063] Environmental interference suppression principle:

[0064] Vibration suppression: the viscoelastic damping effect of the sawtooth wave vibration isolation buffer layer 2 can convert 20-2000Hz vibration energy into heat energy dissipation (vibration transmission rate <5%).

[0065] Thermal stress elimination: the CTE difference between the quartz support base 3 and the stainless steel protective shell 1 is absorbed by the annular vibration isolation buffer layer 2 (silicon-based elastomer), avoiding the cracking of the packaging structure caused by temperature cycling.

[0066] Three, implementation and technical effects

[0067] Packaging process:

[0068] In the vacuum glove box (humidity <10%RH), the following steps are completed in sequence:

[0069] a) UV curing positioning of the micro-cantilever beam (365nm light source, irradiation intensity 15mW / cm²);

[0070] b) Filter-permeable membrane hot pressing (temperature 120℃, pressure 5MPa, pressure holding time 30s);

[0071] c) Rotational curing packaging of the optical fiber ferrule (rotation speed 30rpm, three times of curing to reduce internal stress).

[0072] Performance index:

[0073] Detection range: gas generally 0-10000ppm (resolution up to 1ppm), temperature -40~150℃ (accuracy ±0.1℃), micro-water 0-50ppm (error ±2%).

[0074] Environmental adaptability: long-term work under 5g vibration and 85%RH humidity, signal drift <1%FS.

[0075] Four, difference from the prior art

[0076] Structural innovation: stepped quartz support base 3 realizes integrated detection of three parameters of gas / temperature / micro-water (traditional scheme requires three independent sensors). The sawtooth wave vibration isolation buffer layer 2 breaks through the vibration suppression bottleneck of the traditional O-ring seal (vibration attenuation rate is increased by 3 times).

[0077] Material innovation: polytetrafluoroethylene modified permeable membrane (gas selectivity coefficient >100) has significantly improved performance compared to traditional PDMS membrane (coefficient ≈20). The ultraviolet curing glue (Tg≥120℃) solves the high temperature creep problem of traditional epoxy resin glue (Tg≈80℃).

[0078] The present application realizes the unification of high-precision multi-parameter detection and environmental robustness on the MEMS scale through the design of light-mechanical-thermal multi-physical field coupling, and provides a new generation of optical fiber sensing solution for industrial Internet of Things.

[0079] Example 2

[0080] The preferred embodiments of the present application are described in detail in conjunction with the accompanying drawings. The present application takes the simultaneous monitoring of SF6 gas concentration and transformer oil temperature as an application scenario, and demonstrates the specific preparation process of the sensor:

[0081] I. Core component preparation

[0082] 1.1. Quartz support base 3 processing

[0083] Material: JGS2 grade optical quartz glass (purity >99.99%, CTE=0.55×10⁻ 6 / ℃) is selected.

[0084] Processing steps:

[0085] Step 1.1.1: Define the stepped structure pattern on the surface of the quartz substrate through the photoetching process, and use reactive ion etching (RIE) to form three levels of steps (step height difference 0.3mm, transition surface inclination angle 45°±1°).

[0086] Step 1.1.2: Use an ultra-precision drilling machine to process the inside of the base:

[0087] First accommodating cavity (diameter 3.2mm): used for mounting the optical fiber collimating lens 4 and the photoacoustic cell 5;

[0088] Second accommodating cavity (diameter 2.0mm): fixed first ceramic optical fiber ferrule 6 for temperature detection;

[0089] Third accommodating cavity (diameter 2.5mm): positioning second ceramic optical fiber ferrule 7 for gas / micro-water detection.

[0090] Step 1.1.3: Surface polishing treatment: Chemical mechanical polishing (CMP) is used to make the base surface roughness Ra < 0.01 μm.

[0091] 1.2. Fabrication of Fabry-Perot micro-cantilever membrane diaphragm 11

[0092] Substrate: Double-side polished 4-inch SOI silicon wafer (device layer thickness 150 μm, buried oxide layer 2 μm).

[0093] Process flow:

[0094] Step 1.2.1: Nano-indentation processing: A hexagonal pit array (depth 200 nm) with a period of 500 nm is etched on the cantilever surface by focused ion beam (FIB).

[0095] Step 1.2.2: Gold film deposition: A 1 μm thick gold reflective layer (reflectivity > 95% @ 1550 nm) is plated on the end of the beam by magnetron sputtering.

[0096] Step 1.2.3: Release process: The back silicon substrate is removed by XeF2 vapor etching, leaving the cantilever beam structure (size: length 2 mm x width 0.5 mm x thickness 150 μm).

[0097] 1.3. Filter-permeable membrane composite structure

[0098] Porous stainless steel air-permeable filter 12:

[0099] Material: 316L stainless steel, laser-drilled to form a honeycomb-shaped through-hole with a pore size of 10 ± 2 μm (porosity 60%).

[0100] Post-processing: Electrochemical polishing to remove burrs, and plating a 3 μm thick titanium nitride wear-resistant layer on the surface.

[0101] Polymer selective permeable membrane 13:

[0102] Raw material: A blended solution of polytetrafluoroethylene (PTFE) and perfluorosulfonic acid resin (mass ratio 7:3).

[0103] Membrane forming process: A composite membrane with a thickness of 80 μm is prepared by electrospinning, and is heat-pressed and shaped at 180°C.

[0104] II. Sensor assembly

[0105] 2.1. Assembly in a vacuum environment

[0106] Assemble in the following order in a nitrogen-filled glove box (humidity < 8% RH, oxygen content < 10 ppm):

[0107] Step 2.1.1: Place the Fabry micro-cantilever membrane 11 on the first stage plane, spot the epoxy acrylate UV glue (Norland NOA81, refractive index 1.51), and cure it using a 365 nm UV light source (intensity 20 mW / cm2) for 60 seconds.

[0108] Step 2.1.2: After stacking the filter with the permeable membrane, place it on the second stage plane, apply a pressure of 5 MPa, and heat press at 120°C for 30 seconds to achieve interface fusion.

[0109] Step 2.1.3: Inject UV glue into the third holding cavity, insert a ceramic core for temperature detection, and cure it in three times (each time 10 seconds of irradiation, with 2 minutes of stress release interval) through a rotating curing table (rotation speed 20 rpm).

[0110] 2.2. Optical system integration

[0111] Fiber collimating lens 4 installation: Embed a gradient refractive index lens (GRIN lens, focal length 2 mm) into the first holding cavity, and calibrate the perpendicularity of the optical axis and the cantilever beam reflecting surface through a six-axis adjusting frame (error <0.1°).

[0112] Photoacoustic cell 5 processing: Use a femtosecond laser to carve a cylindrical cavity with a diameter of 2.5 μm inside the quartz base, and polish the inner wall to Ra=0.03 μm with hydrofluoric acid vapor.

[0113] 2.3. Protective system packaging

[0114] Vibration isolation liner installation: Fit the pre-formed silicon-based elastomer liner (Shore hardness HA60, sawtooth depth 0.5 mm) into the quartz base, and apply a pre-tightening force of 5 N after being installed in the stainless steel shell.

[0115] End cap sealing: Apply perfluoroether grease to the threaded part of the shell, and tighten the fixed end cap 14 to a torque of 0.8 N·m to achieve IP65 level sealing.

[0116] III. Calibration and testing

[0117] 3.1. Temperature compensation calibration

[0118] Place the sensor in a high-low temperature chamber (-40°C~150°C), and establish a compensation model through the following steps:

[0119] Step 3.1.1: Record the thermal-optical coefficient change curve of the temperature-sensitive crystal (material: LiNbO3) (dλ / dT=0.01 nm / ℃).

[0120] Step 3.1.2: Measure the temperature drift of the resonance frequency of the photoacoustic cell 5 (Δf=12 Hz / ℃).

[0121] Step 3.1.3: Write temperature-frequency compensation algorithm in FPGA chip to achieve a temperature measurement accuracy of ±0.05℃.

[0122] 3.2. Gas sensitivity test

[0123] Calibration with standard SF6 gas (concentration 0-1000ppm):

[0124] Step 3.2.1: Pass different concentrations of gas and record the deflection of the micro-cantilever beam (resolution 0.1nm) and the amount of interference fringe movement.

[0125] Step 3.2.2: Establish concentration-wavelength shift relationship curve (sensitivity 0.18nm / ppm, linearity R²>0.999).

[0126] Step 3.2.3: Verify the selectivity of the permeation membrane: cross-sensitivity to CH4, CO2 <0.5%.

[0127] 3.3. Vibration interference test

[0128] On an electromagnetic vibration table (frequency 20-2000Hz, acceleration 5g):

[0129] Step 3.3.1: Compare the signal fluctuation before and after adding the vibration isolation liner: the fluctuation amplitude is ±3% without vibration isolation, and it is reduced to ±0.5% after vibration isolation.

[0130] Step 3.2.2: Check the fiber coupling loss after 8 hours of continuous vibration: the insertion loss change is less than 0.2dB.

[0131] As can be understood by those skilled in the art, other similar connection methods can also achieve the present application. For example, welding, bonding or screwing, etc.

[0132] The above describes in detail the preferred embodiments of the present application. It should be understood that those skilled in the art can make many modifications and changes without creative labor according to the concept of the present application. Therefore, any technical solution that can be obtained by logical analysis, reasoning or limited experiment based on the existing technology according to the concept of the present application should be within the protection scope determined by the claims.

Claims

1. A MEMS fiber optic gas and temperature integrated sensor, characterized in that, It includes a quartz support base (3), one end of which is provided with a three-level stepped structure, wherein a Faber microcantilever 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) has three functional cavities inside: The first cavity is equipped with an optical fiber collimating lens (4) and a photoacoustic cell (5). The light emitted from the optical fiber collimating lens (4) is irradiated onto the Faber microcantilever beam diaphragm (11) through the photoacoustic cell (5). The second cavity is equipped with a first ceramic fiber ferrule (6), which is tightly fitted to the rear end of the temperature sensing crystal (9). The front end of the temperature sensing crystal (9) is parallel to the first stepped plane. The light emitted from the first ceramic fiber ferrule (6) is reflected back into the optical fiber after irradiating the temperature sensing crystal (9). The third cavity is equipped with a second ceramic fiber ferrule (7). The light emitted from the second ceramic fiber ferrule (7) is reflected back to the fiber after hitting the center of the cantilever beam end on the Fapper microcantilever beam diaphragm (11).

2. The MEMS fiber optic gas and temperature integrated 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 single-mode optical fiber (8) to form an optical transmission channel.

3. The MEMS fiber optic gas and temperature integrated sensor according to claim 1, characterized in that, The first ceramic fiber ferrule (6) and the second ceramic 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 fiber optic gas and temperature integrated sensor according to claim 1, characterized in that, The Faber microcantilever beam diaphragm (11) comprises a silicon-based cantilever beam body and a gold film reflective mirror, wherein the surface of the silicon-based cantilever beam body is provided with a nano-indentation array structure.

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

6. The MEMS fiber optic gas and temperature integrated sensor according to claim 1, characterized in that, The Fabry-Perot microcantilever diaphragm (11) is fixed to the quartz support base (3) by UV-curing adhesive; The UV-curable adhesive is an epoxy acrylate photosensitive adhesive with a refractive index of 1.48-1.52 and a glass transition temperature of ≥120℃ after curing.

7. The MEMS fiber optic gas and temperature integrated 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 0.05 μm.

8. The MEMS fiber optic gas and temperature integrated 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 layer (2) is provided between the quartz support base (3) and the inner wall of the stainless steel protective shell (1). A fixed end cap (14) is provided at one end of the stainless steel protective shell (1) corresponding to the three-stage stepped structure.

9. A MEMS fiber optic gas and temperature integrated sensor according to claim 8, characterized in that, The vibration isolation buffer liner (2) is a pre-formed silicon-based elastomer bushing with a sawtooth waveform structure in cross section, a Shore hardness of HA50-70, and a compression set of less than 10%.

10. A method for fabricating a MEMS fiber optic gas and temperature integrated sensor as described in any one of claims 1-9, characterized in that, Specifically as follows: For the quartz support base (3), a three-level step is formed by reactive ion etching, and three cavities are processed inside the quartz support base (3); For the Faber microcantilever beam film (11), a double-sided polished SOI silicon wafer is used as the substrate, a hexagonal pit array is etched on the surface of the cantilever beam, and a gold reflective layer is deposited at the end of the beam by magnetron sputtering. For the filter-permeable membrane composite structure, the porous stainless steel breathable filter (12) is formed into a honeycomb through hole by perforation. After electrochemical polishing, a thick titanium nitride wear-resistant layer is plated on the surface. The polymer selective permeable membrane (13) is prepared into a composite membrane by electrospinning of a polytetrafluoroethylene and perfluorosulfonic acid resin blend solution and hot pressing. The following steps were performed in a vacuum glove box: the Fapper microcantilever membrane (11) was fixed to the first stepped plane with UV-curing adhesive; the porous stainless steel breathable filter (12) and the polymer selective permeation membrane (13) were stacked and placed on the second stepped plane, and fused with the interface by hot pressing; UV-curing adhesive was injected into the second receiving cavity, the second ceramic insert for temperature detection was inserted, and the mixture was cured multiple times by rotating the curing table; The fiber collimating lens (4) is embedded in the first receiving cavity to calibrate the perpendicularity of the optical axis to the cantilever beam reflecting surface; A cylindrical cavity is carved inside the quartz support base (3), and the inner wall of the cylindrical cavity is polished to a set roughness. The pre-formed silicon-based elastomer vibration isolation buffer liner (2) is fitted into the quartz support base (3), and then a pre-tightening force is applied after the stainless steel protective shell (1) is installed. Apply perfluoroether grease to the threaded portion of the stainless steel protective housing (1) and tighten the fixing cap (14) to the set torque; Temperature compensation calibration: Place the sensor in a high and low temperature chamber and record the thermo-optic coefficient change curve of the temperature-sensing crystal (9); measure the temperature drift of the resonant frequency of the photoacoustic cell (5); write the temperature-frequency compensation algorithm into the FPGA chip.

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