Multilayer heterogeneous integrated acoustic shielding breathable film, preparation method and application

Abstract

The invention provides a multilayer heterogeneous integrated acoustic shielding gas-permeable membrane, a preparation method and application, and belongs to the field of gas-permeable membranes of photoacoustic spectrum gas detection systems. The multilayer heterogeneous integrated acoustic shielding breathable film comprises an upper-layer structure, a middle-layer structure and a lower-layer structure, wherein the upper-layer structure, the middle-layer structure and the lower-layer structure are compounded together to form the breathable film; the upper layer structure adopts a porous support body sprayed with AF2400; the middle layer structure adopts an expanded polytetrafluoroethylene microporous membrane; and the lower-layer structure adopts an anodic aluminum oxide film. The expanded polytetrafluoroethylene microporous membrane and the anodic aluminum oxide membrane are both arranged on the mounting module, and the porous support body sprayed with the AF2400 and the mounting module are assembled through a flexible adhesive. According to the invention, oil-gas separation, gas exchange, pressure difference adaptive adjustment and acoustic shielding can be comprehensively realized, and the application in the field of photoacoustic spectrometry gas detection such as oil-soluble gas detection can be met.

Description

Technical Field

[0001] The present invention relates to the field of gas-permeable membranes for photoacoustic spectroscopy gas detection systems, and more particularly to a multi-layer heterogeneous integrated acoustic shielding gas-permeable membrane, a preparation method and an application thereof. Background Art

[0002] With the rapid development of the Internet of Things industry, gas sensors, as one of the basic sensing elements of the Internet of Things, are widely used in fields such as gas emission monitoring, atmospheric sensing, and respiratory diagnosis. According to different working principles, gas sensing technologies mainly include gas chromatography, electrochemistry, metal oxide, non-dispersive infrared absorption, photoacoustic spectroscopy, etc. Among them, photoacoustic spectroscopy has been widely used in on-line gas analysis of industrial production processes such as petrochemical, metallurgy, and power in recent years due to its advantages of low background noise, fast response speed, good gas selectivity, and high stability. As a key interface component of the photoacoustic spectroscopy sensor, the gas-permeable membrane plays roles such as selectively permeating target gas molecules, blocking pollutants such as dust and droplets, adjusting the water vapor permeability to control the humidity effect, and protecting internal optical and acoustic components in the sensor, and its performance directly affects the detection accuracy, response speed, and long-term stability of the sensor.

[0003] Patent CN202411653133.9 proposes a waterproof and breathable and differential calibration packaging device and method for a gas sensor. A waterproof and breathable membrane is installed on the top of the sensor housing, which can allow the measured gas to pass through quickly while reducing the speed of water vapor entering the test space. The fan drives the gas to flow between the test space and the absorption space, and can adsorb the water vapor or water vapor / measured gas entering the test space. If the absorption space is filled with a water-absorbing material, the slow penetration of water vapor by the waterproof and breathable membrane and the fan air flow driving function are combined to complete the removal of water vapor in the test space. The anti-interference detection of the gas sensor is realized by differentiating the output signals in the fan-on and fan-off states. Patent CN202510071989.3 discloses a preparation method of a fluorine-free waterproof and breathable membrane based on irradiation technology. The structure of the base film plus the coating improves the overall structural strength and can be placed under a certain water pressure. The pore size and pore density of the base film can be adjusted, and a pore-forming agent is added to the coating, so that the air permeability of the waterproof and breathable membrane as a whole can be flexibly adjusted according to requirements. Patent CN116337776A proposes a non-resonant CO sensor and detection method based on photoacoustic spectroscopy technology. The microporous sound-blocking and breathable membrane used is made of expanded polytetrafluoroethylene material, and billions of micron-sized pores are designed on the membrane surface. These pore diameters are more than 700 times larger than air gas molecules, ensuring reliable air permeability and pressure balance inside and outside the membrane; at the same time, the micron-sized pores make the microporous membrane have a large acoustic impedance, and the sound blocking rate is greater than 50%, ensuring the acoustic tightness of the non-resonant photoacoustic cell. Patent CN117890309A discloses a photoacoustic spectroscopy gas detection device. The air-permeable holes in the device are arranged in the photoacoustic measurement cell body; the MEMS switch is located on the inner wall of the photoacoustic measurement cell body to cover the air-permeable holes; the waterproof and breathable membrane is located on the outer wall of the photoacoustic measurement cell body to cover the air-permeable holes.

[0004] The breathable membrane, or gas exchange membrane, as the core component of the micro-integrated photoacoustic spectroscopy sensor, significantly improves the detection performance and stability of the system through functions such as rapid gas exchange, isolation of external noise, and anti-pollution. The sensor uses the method of free gas diffusion to detect gas concentration, and the performance of the breathable membrane directly determines the response time and signal quality of the sensor. The better the air permeability of the breathable membrane, the faster the gas exchange speed between the gas inside the sensor photoacoustic cell and the outside gas, and the shorter the response time of the sensor. However, for the photoacoustic spectroscopy system, the selection of the breathable membrane cannot only focus on its air permeability. The photoacoustic cell needs to operate in an environment with good airtightness to maintain stable acoustic boundary conditions, so that the photoacoustic signal does not leak and the influence of external noise is weakened. Therefore, the sound insulation ability of the gas exchange membrane is also a major consideration.

[0005] At present, existing breathable membrane materials still face challenges in aspects such as the selective trade-off between breathability and sound insulation ability, long-term stability, and complex environmental adaptability. Developing high-performance breathable membrane materials and optimizing their structural design has become one of the key research directions for improving the performance of photoacoustic spectroscopy sensors. Summary of the Invention

[0006] In view of the above technical problems, the present invention proposes a multi-layer heterogeneous integrated acoustic shielding breathable membrane, a preparation method thereof, and a specific application.

[0007] The technical solution adopted by the present invention is as follows:

[0008] One of the purposes of the present invention is to propose a multi-layer heterogeneous integrated acoustic shielding breathable membrane, which includes an upper layer structure, a middle layer structure, and a lower layer structure. The upper layer structure, the middle layer structure, and the lower layer structure are combined together to form a breathable membrane;

[0009] The upper layer structure uses a porous support sprayed with AF2400; the middle layer structure uses an expanded polytetrafluoroethylene microporous membrane; the lower layer structure uses an anodic aluminum oxide membrane.

[0010] Preferably, both the expanded polytetrafluoroethylene microporous membrane and the anodic aluminum oxide membrane are arranged on the installation module, and the porous support sprayed with AF2400 is assembled with the installation module through a flexible adhesive.

[0011] Preferably, the pore diameter of the expanded polytetrafluoroethylene microporous membrane is between 0.1 and 1.0 micrometers; the porosity of the anodic aluminum oxide membrane is 50% - 80%.

[0012] Preferably, the porous support sprayed with AF2400 is prepared by the following process:

[0013] Take the AF2400 solution in a high-pressure spray head, turn on the rotating table and air pump to start spraying; let the sprayed porous support stand at room temperature, and then heat it step by step to remove the solvent, and finally cool it naturally to room temperature.

[0014] Preferably, the expanded polytetrafluoroethylene microporous membrane is prepared by the following process:

[0015] Mix polytetrafluoroethylene dispersion powder with a liquid hydrocarbon lubricant by low-temperature vacuum stirring, prepare a uniform preform through a granulator, then perform vertical axial extrusion, then perform pre-sintering treatment in a nitrogen environment, raise the temperature to remove the lubricating liquid, perform biaxial stretching to form pores, and finally perform constrained-state heat treatment at a temperature higher than the melting point of polytetrafluoroethylene to obtain it.

[0016] Preferably, the anodic aluminum oxide membrane is prepared by the following process:

[0017] First, grow a highly ordered Al2O3 nanopore array on the surface of the aluminum foil, then perform oxidation. Next, immerse the anodized composite into a mixed solution of copper chloride and hydrochloric acid for corrosion. Then, use phosphoric acid for pore opening and pore expansion. Finally, cool down and let it stand still to obtain the product.

[0018] The second object of the present invention is to provide a preparation method of the above-mentioned multi-layer heterogeneous integrated acoustic shielding breathable membrane, which comprises the following steps:

[0019] (1) First, separately prepare a porous support sprayed with AF2400, an expanded polytetrafluoroethylene microporous membrane, and an anodic aluminum oxide membrane;

[0020] (2) Place the expanded polytetrafluoroethylene microporous membrane and the anodic aluminum oxide membrane on the installation module, and the expanded polytetrafluoroethylene microporous membrane is above the anodic aluminum oxide membrane. Assemble the porous support sprayed with AF2400 and the installation module through a flexible adhesive, and the porous support sprayed with AF2400 is above the expanded polytetrafluoroethylene microporous membrane.

[0021] The third object of the present invention is to provide the application of the multi-layer heterogeneous integrated acoustic shielding breathable membrane as described above in photoacoustic spectroscopy gas detection.

[0022] The beneficial technical effects of the present invention are as follows:

[0023] The breathable membrane of the present invention can comprehensively achieve oil-gas separation, gas exchange, differential pressure self-adaptive regulation, and acoustic shielding by compounding the upper porous support sprayed with AF2400, the middle expanded polytetrafluoroethylene microporous membrane, and the lower anodic aluminum oxide membrane, meeting the application in the field of photoacoustic spectroscopy gas detection such as oil-soluble gas detection.

[0024] Among them, the porous support sprayed with AF2400 can play a good role in oil-gas separation. The middle expanded polytetrafluoroethylene microporous membrane and the lower anodic aluminum oxide membrane cooperate synergistically to achieve the comprehensive effect of gas exchange and sound insulation, and achieve the balance of the two aspects. Description of the Drawings

[0025] Figure 1 is a schematic diagram of a multi-layer heterogeneous integrated acoustic shielding breathable membrane of the present invention;

[0026] Figure 2 is a schematic diagram of the structural layout of the lower anodic aluminum oxide membrane;

[0027] Figure 3 is a schematic diagram of the case where the anodic aluminum oxide membrane is used as a breathable membrane;

[0028] Figure 4 is a schematic diagram of the structural layout of the middle polytetrafluoroethylene membrane;

[0029] Figure 5 Schematic diagram of the case where a polytetrafluoroethylene membrane is used as a breathable membrane;

[0030] Figure 6 Schematic diagram of the oil-gas separation equilibrium time achieved by a porous support sprayed with AF2400 on the upper layer;

[0031] Figure 7 Comparison chart of the photoacoustic signal amplitudes of different membrane-encapsulated photoacoustic cells. Specific implementation manners

[0032] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0033] Reference Figure 1 , a multi-layer heterogeneous integrated acoustic shielding breathable membrane applied to photoacoustic spectroscopy gas detection, including a porous support 1 sprayed with AF2400 on the upper layer, an expanded polytetrafluoroethylene (ePTFE) microporous membrane 2 in the middle layer, an anodic aluminum oxide (AAO) membrane 3 in the lower layer, and an installation module 4.

[0034] The expanded polytetrafluoroethylene microporous membrane 2 and the anodic aluminum oxide membrane 3 are both arranged on the installation module 4, and the porous support 1 sprayed with AF2400 is assembled with the installation module 4 through a flexible adhesive. The installation module 4 is a rigid-flexible hybrid gas exchange module with corrosion resistance and temperature change resistance, so as to be applied to extreme working conditions and improve the stability of gas exchange and acoustic shielding of the membrane.

[0035] The porous support 1 sprayed with AF2400 is prepared through the following process:

[0036] Adjust the high-pressure nozzle, ceramic, and rotating table to keep them centered; set the air pump pressure to 0.2 MPa; take 5 mL of AF2400 solution (DuPont AF2400, 1 wt%, solvent: FC-40) in the high-pressure nozzle, turn on the rotating table and turn on the air pump to start spraying; secondly, let the sprayed ceramic stand at room temperature for 20 min to evaporate most of the solvent, then stand and heat at a temperature 5 °C above the boiling point of the solvent (@165 °C) for 10 min, and then stand and heat at a temperature 5 °C above the glass transition temperature of AF2400 (@245 °C) for 20 min to remove the last organic solvent. Finally, to improve the film-forming quality of the AF2400 layer and enhance its bonding strength with the ceramic layer, further stand and heat at 330 °C for 10 min and then naturally cool to room temperature. It should be noted that when performing high-temperature baking, heating above 360 °C should be avoided to prevent complete damage to the AF2400 film layer.

[0037] The expanded polytetrafluoroethylene microporous membrane 2 is prepared through the following process:

[0038] (1) An ultrafine PTFE dispersion powder and a liquid hydrocarbon lubricant are subjected to low-temperature (-15°C) vacuum stirring and mixing to prepare a uniform preform through a granulator, and the shear rate is controlled to avoid premature fibril breakage.

[0039] (2) Vertical axial extrusion is carried out at a pressure of 35 MPa and a temperature of 50°C. Through a die orifice design with a compression ratio of 10:1, a green body with a molecular chain orientation is formed.

[0040] (3) Pre-sintering treatment is carried out in a nitrogen environment. The lubricating liquid is removed by heating at 200°C, partial crystallization is achieved at 200 - 300°C, and heat preservation is carried out at 330°C for 1 h.

[0041] (4) It is changed to 200°C for biaxial stretching to form pores.

[0042] (5) Constraint state heat treatment is carried out at a temperature higher than the melting point of PTFE, that is, 350°C, and thus obtained.

[0043] A porous alumina film with a three-dimensional cross-linked pore structure is prepared by coupling anodic oxidation and chemical etching techniques.

[0044] Specifically, the lower-layer anodic aluminum oxide (AAO) film 3 is prepared through the following process:

[0045] (1) The two-step anodic oxidation method is adopted. In the first stage, 0.3 M oxalic acid is used at 6°C to grow a highly ordered Al2O3 nanopore array on the surface of 99.99% high-purity aluminum foil through a 40 V DC voltage. In the second stage, the oxidation time is regulated to 150 min to obtain a hexagonal stack structure with a pore diameter of 200 um and a pore spacing of 10 um. That is, the first stage is the growth stage for growing alumina, and the second stage is the pore diameter formation stage for obtaining the hexagonal structure.

[0046] (2) The anodized composite is immersed in a mixed solution of copper chloride and hydrochloric acid, and selective etching is carried out at 25°C. Real-time impedance analysis is carried out at a sampling rate of 100 kHz to control the etching end point, and the separation of the substrate and the AAO film is achieved.

[0047] (3) 5% phosphoric acid is used for pore opening and pore expansion. First, etching is carried out at 60°C for 15 min for pore diameter expansion, then etching is carried out at 80°C for 5 min to form cross-linked nodes, and finally the temperature is lowered and left standing for 30 min to inhibit over-etching, and thus obtained.

[0048] The mass ratio of the above-mentioned copper chloride to hydrochloric acid is 1:1. Of course, the mixing ratio can also be changed according to needs.

[0049] Considering the structural characteristics of different gas exchange membranes, the present invention separately prepares a porous support 1 sprayed with AF2400 on the upper layer, an expanded polytetrafluoroethylene (ePTFE) microporous membrane 2 in the middle layer, and an anodic aluminum oxide (AAO) membrane 3 in the lower layer, and then composites them. In particular, the present invention realizes the balance between gas exchange and sound insulation through the combination of the expanded polytetrafluoroethylene (ePTFE) microporous membrane 2 in the middle layer and the anodic aluminum oxide (AAO) membrane 3 in the lower layer.

[0050] The composites between the above layers can be specifically carried out by hot melt bonding. For example, the composite can be carried out under the conditions of argon protection at a temperature of 300 °C and a pressure of 10 MPa through a hot pressing bonding process.

[0051] The following is a supplementary description of the upper, middle and lower layer structures:

[0052] For the porous support 1 sprayed with AF2400, an AF2400 separation layer is constructed on the surface of the porous support by spray deposition technology, and the precise regulation of the separation membrane structure is realized through a gas-liquid two-phase co-deposition process. This technology utilizes the dynamic balance characteristics of the two-phase interface to form a gradient densified coating of AF2400 polymer on the surface of the porous substrate, thereby significantly increasing the interfacial resistance of the solution penetration path and effectively improving the liquid blocking performance of the separation system.

[0053] The expanded polytetrafluoroethylene (ePTFE) microporous membrane 2 has the following characteristics: microporous structure: there are billions of micropores per square centimeter, and the pore diameter is between 0.1 and 1.0 microns, much smaller than liquid water droplets but much larger than gas molecules. Hydrophobic and oleophobic: It can effectively block liquid water, oil stains and dust, while allowing gases to pass freely. Chemical inertness: resistant to strong acids and alkalis, anti-ultraviolet, resistant to high and low temperatures (-40 °C to 150 °C). In a waterproof and breathable structure, the ePTFE membrane is usually combined with an installation module to form a differential pressure self-adaptive adjustment mechanism: when the internal air pressure increases (when the gas in the photoacoustic cell absorbs light to generate an acoustic signal), the air pressure pushes the ePTFE membrane to deform outward, and the micropores are partially closed due to stretching, reducing the gas escape rate. When the internal air pressure decreases (when the internal gas concentration is low and the acoustic signal is weak), the external air pressure makes the ePTFE membrane retract inward, and the micropores expand, promoting the entry of external air to balance the pressure. The ePTFE (expanded polytetrafluoroethylene) microporous membrane 2 can form a microporous network with a pore size of 0.1 to 10 microns through a stretching process, allowing gas molecules (such as CO2, O2, etc.) to pass freely, while blocking liquid water, oil stains and particulate matter, and the air permeability per unit area can reach 1000 to 5000 mL / (cm 2 ·h), meeting the requirements of rapid gas exchange (such as the real-time response of a photoacoustic spectroscopy sensor).

[0054] The anodic aluminum oxide (AAO) membrane 3 has a highly ordered pore structure and adjustable physicochemical properties. The pore diameter can be precisely controlled through the oxidation process to meet the selective permeation requirements of different gas molecules. The pores are arranged in a parallel hexagonal close-packed pattern, with short gas transmission paths and low resistance, resulting in high gas permeability efficiency. The porosity can reach 50% - 80%, balancing high gas permeability and mechanical strength. It has a melting point as high as 2000°C and can operate stably for a long time below 500°C, providing assistance for the application of photoacoustic spectroscopy gas sensors under extreme working conditions.

[0055] The installation module 4 is a rigid-flexible hybrid gas exchange module on the shell of the photoacoustic spectroscopy gas sensor that resists corrosion and temperature changes. Both the ePTFE (expanded polytetrafluoroethylene) microporous membrane 2 and the anodic aluminum oxide (AAO) membrane 3 are located at this pore position. The porous support 1 sprayed with AF2400 and the installation module 4 are assembled through a flexible adhesive, which not only serves to combine the porous support 1 with the installation position 4. Moreover, the combination through the flexible adhesive can prevent damage to the entire gas exchange module caused by high temperature and external vibration, improving the structural stability.

[0056] The present invention also conducted relevant experiments, which are as follows:

[0057] As Figure 2 、 Figure 3 As shown, when only the AAO membrane in the present invention is selected as the gas exchange membrane, at pore diameters of 350nm, 450nm, and 500nm, the sensor response speeds are similar. As the pore diameter increases, the fluctuations in the collected signals also increase. All three have slight noise interference during the ventilation process, indicating that the AAO membrane does not completely shield noise. When the pore diameter increases to 800nm, the amplitude of the photoacoustic signal drops significantly, indicating that the photoacoustic signal leaks at this time, and the sound shielding effect during the ventilation process weakens, resulting in obvious noise interference. As a rigid membrane, the AAO membrane is relatively fragile and not waterproof, which is not conducive to the long-term use stability of the sensor.

[0058] Refer to Figure 4 、 Figure 5 When only the PTFE membrane is used as the gas exchange membrane, as the membrane pore diameter increases from 100nm, 220nm to 450nm, the response speed of the sensor gradually increases, and the response speed is stronger than that of the AAO membrane, indicating that the PTFE membrane has a faster gas exchange speed than the AAO membrane. As the pore diameter increases, the photoacoustic signal decreases significantly, proving that the uniform pore diameter of the AAO membrane can better suppress the loss of low-frequency photoacoustic signals than the filamentous pore diameter of the PTFE, and the signal quality is poor. Even the smallest 100nm pore diameter PTFE membrane has a poor noise shielding ability, and the signal noise is relatively high under stable conditions.

[0059] Refer to Figure 6, the three-layer structure involved in the present invention, in which a porous support 1 sprayed with AF2400 is used for oil and gas separation. As shown in the figure, the oil and gas separation equilibrium time is reduced from the hour level to the minute level (40 min).

[0060] Reference Figure 7 , the three-layer structure involved in the present invention, in which the middle layer is an expanded polytetrafluoroethylene (ePTFE) microporous membrane 2 and the lower layer is an anodic aluminum oxide (AAO) membrane 3. The permeability of the middle layer expanded polytetrafluoroethylene microporous membrane at 7 kPa is 1500 mL / min·cm 2 . It helps to dustproof and waterproof the whole sensor and effectively isolates external noise. The thickness of the lower rigid anodic aluminum oxide membrane is 50 μm, and the center distance of the pores is 450 nm. Since a double-pass AAO membrane is used, the pore diameters on both sides are uniformly 350 nm, which can effectively prevent the rapid movement of gas, and at the same time has a small impact on the free diffusion of air in a long time, and has a certain inhibitory effect on the loss of low-frequency photoacoustic signals, which helps to form a quasi-sealed photoacoustic cell. Figure 7 For the performance test of photoacoustic cells encapsulated with different breathable membranes, it can be seen that when there is no breathable membrane covering the air holes of the photoacoustic cell, since the photoacoustic signal completely leaks, no sine waveform is generated, and since the external sound is not isolated, the noise signal is serious; when the air holes are covered with a PTFE membrane, a sine waveform of the photoacoustic signal can be generated, but due to the high permeability of the PTFE membrane, the measured signal is only 0.4932 V of the peak-to-peak value; in contrast, when the air holes are covered with a double-layer AAO-PTFE membrane, the peak value increases to 0.9365 V, and the complete sine waveform of the photoacoustic signal is retained, and the effect is good; after the photoacoustic cell is completely sealed, the overall peak value reaches 1.2784 V. However, if the photoacoustic cell is completely sealed and no gas exchange can occur outside, the gas sensing function cannot be realized.

Claims

1. A multi-layer heterogeneous integrated acoustic shielding breathable membrane, characterized in that: It includes an upper structure, a middle structure and a lower structure, and the upper structure, the middle structure and the lower structure are combined together to form a breathable membrane; The upper structure uses a porous support sprayed with AF2400; the middle structure uses an expanded polytetrafluoroethylene microporous membrane; the lower structure uses an anodic aluminum oxide membrane.

2. The multi-layer heterogeneous integrated acoustic shielding breathable film according to claim 1, wherein: Both the expanded polytetrafluoroethylene microporous membrane and the anodic aluminum oxide membrane are arranged on the installation module, and the porous support sprayed with AF2400 is assembled with the installation module through a flexible adhesive.

3. The multi-layer heterogeneous integrated acoustic shielding breathable film according to claim 1, wherein: The pore diameter of the expanded polytetrafluoroethylene microporous membrane is between 0.1 and 1.0 microns; the porosity of the anodic aluminum oxide membrane is 50% - 80%.

4. The multi-layer heterogeneous integrated acoustic shielding breathable film according to claim 1, characterized in that The porous support sprayed with AF2400 is prepared by the following process: Take the AF2400 solution in a high-pressure nozzle, turn on the rotating table and air pump to start spraying; let the sprayed porous support stand at room temperature, then heat it step by step to remove the solvent, and finally cool it naturally to room temperature.

5. A multi-layer heterogeneous integrated acoustic shielding breathable membrane according to claim 1, characterized in that, The expanded polytetrafluoroethylene microporous membrane is prepared by the following process: Use polytetrafluoroethylene dispersion powder and liquid hydrocarbon lubricant to carry out low-temperature vacuum stirring and mixing, prepare a uniform preform through a granulator, then carry out vertical axial extrusion, then carry out pre-sintering treatment in a nitrogen environment, raise the temperature to remove the lubricating liquid, carry out biaxial stretching to form pores, and finally carry out constrained-state heat treatment at a temperature higher than the melting point of polytetrafluoroethylene to obtain it.

6. The multi-layer heterogeneous integrated acoustic shielding breathable film according to claim 1, characterized in that, The anodic aluminum oxide membrane is prepared by the following process: First, grow a highly ordered Al2O3 nanopore array on the surface of the aluminum foil, then carry out oxidation, then immerse the anodized composite body in a mixed solution of copper chloride and hydrochloric acid for corrosion, then use phosphoric acid for pore opening and pore expansion, and finally cool it down and let it stand to obtain it.

7. The preparation method of the multi-layer heterogeneous integrated acoustic shielding breathable film according to any one of claims 1 to 6, characterized in that, It includes the following steps: (1) First, separately prepare a porous support sprayed with AF2400, an expanded polytetrafluoroethylene microporous membrane and an anodic aluminum oxide membrane; (2) Arrange both the expanded polytetrafluoroethylene microporous membrane and the anodic aluminum oxide membrane on the installation module, and the expanded polytetrafluoroethylene microporous membrane is above the anodic aluminum oxide membrane. Assemble the porous support sprayed with AF2400 with the installation module through a flexible adhesive, and the porous support sprayed with AF2400 is above the expanded polytetrafluoroethylene microporous membrane.

8. The multi-layer heterogeneous integrated acoustic shielding breathable membrane according to any one of claims 1 to 6 can be applied in photoacoustic spectroscopy gas detection.

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