Preparation method of pressure sensor for metal matrix and pressure sensor for metal matrix

Abstract

The invention discloses a preparation method of a pressure sensor for a metal matrix and the prepared pressure sensor for the metal matrix, and the preparation method comprises the following steps: (1) preparing slurry: dispersing and mixing 5-20 parts by weight of graphene, 10-40 parts by weight of epoxy resin, 30-70 parts by weight of a solvent and 1-5 parts by weight of a dispersant to obtain graphene strain slurry; (2) metal matrix surface pretreatment: roughening the metal matrix surface and then cleaning the roughened metal matrix surface; (3) coating and curing: coating the pretreated metal matrix surface with graphene strain slurry to form a strain induction layer, and heating and curing; and (4) leading out a signal: connecting an electrode on the cured strain induction layer.

Description

Technical Field

[0001] This invention relates to a method for fabricating a pressure sensor for a metal substrate. Background Technology

[0002] Existing pressure sensors generally employ a sandwich structure of "PET / PI substrate - strain sensing layer - encapsulation layer," where PET (polyethylene terephthalate) or PI (polyimide) film serves as the core supporting substrate, supporting the sensing layer and providing mechanical strength. The specific implementation of this technology involves: first, preparing a strain sensing layer (such as a metal strain gauge or carbon-based paste layer) on the PET / PI substrate; then, attaching the substrate-supported sensing unit to the surface of the product being measured via bonding or mechanical fixation; and finally, encapsulation and signal extraction.

[0003] Its shortcomings are as follows: Poor compatibility: The chemical inertness and surface properties of PET / PI substrates result in insufficient interfacial compatibility with tested products such as metal substrates, making them prone to peeling and debonding. The adhesion grade is mostly lower than 3B (GB / T9286-1998).

[0004] Complex process: The cutting, shaping, bonding and subsequent encapsulation of the substrate increases the production process, manufacturing costs and process difficulty.

[0005] Performance limitations: The rigidity / flexibility of the substrate hinders the transmission of strain signals from the tested product to the sensing layer, resulting in sensor sensitivity generally below 0.1 kPa. -1 The response time exceeds 50ms.

[0006] Insufficient form compatibility: Rigid substrates are difficult to fit curved surfaces and irregularly shaped products, while flexible substrates, although improved, still have the problem of interface stress concentration.

[0007] The content of the background section is merely the technology known to the inventor and does not necessarily represent the prior art in this field. Summary of the Invention

[0008] In view of the above problems, the present invention discloses a method for fabricating a metal-based pressure sensor, comprising the following steps: (1) Preparation of slurry: Based on the weight ratio of each component, disperse and mix 5-20 parts of graphene, 10-40 parts of epoxy resin, 30-70 parts of solvent and 1-5 parts of dispersant to obtain graphene strain slurry. (2) Metal substrate surface pretreatment: The metal substrate surface is roughened and then cleaned; (3) Coating and curing: Graphene strain slurry is coated onto the pretreated metal substrate surface to form a strain sensing layer, and then cured by heating; (4) Signal extraction: Connect electrodes to the cured strain sensing layer.

[0009] Furthermore, in step (1): Graphene is reduced graphene oxide; and / or, Graphene sheets with a diameter of 0.5~10μm and a thickness of 0.8~10nm; and / or, The epoxy resin is a bisphenol A type epoxy resin; and / or, The solvent is one or more of N-methylpyrrolidone, ethanol, ethyl acetate, and water; and / or, The dispersant is one or more of sodium dodecylbenzenesulfonate, polyethylene glycol, and polyvinylpyrrolidone; and / or, The dispersion and mixing process consists of ultrasonic dispersion at 300-500W for 30-60 minutes and mechanical stirring at 500-1000r / min for 60-120 minutes.

[0010] Furthermore, in step (1): Graphene sheets with diameters of 1~5μm Graphene 15-16 parts, epoxy resin 22-27 parts, solvent 40-60 parts, dispersant 2-4 parts; and / or, Epoxy resin accounts for 20-30% of the total mass of the graphene strain slurry; and / or, The dispersion and mixing process consists of ultrasonic dispersion at 350-450W for 40-55 minutes and mechanical stirring at 600-800r / min for 80-100 minutes. Further, in step (2): After roughening, the surface roughness Ra of the metal substrate is 0.8~1.2 μm; and / or, The cleaning process is ultrasonic cleaning in an ethanol solution; and / or, The metal substrate is dried after cleaning.

[0011] Furthermore, in step (2): The ethanol solution concentration is 95%; and / or The ultrasonic cleaning is performed at 500W power for 15 minutes; and / or, The drying process involves drying in a 60°C forced-air drying oven for 30 minutes.

[0012] Furthermore, in step (3): The coating method is one of the following processes: spraying, scraping, dipping, or screen printing; and / or, The strain-sensing layer formed after coating is 5~50μm thick; and / or, The curing process involves treating at 80~120℃ for 0.5~2 hours.

[0013] Furthermore, in step (3): Spraying pressure is 0.2~0.5MPa, nozzle distance is 10~30cm; and / or, Use #5~#20 wire rods for scraping; and / or, The strain-sensing layer formed after coating is 15~40μm thick; and / or, The curing process is carried out at 90~110℃ for 0.8~1.5 hours. Further, in step (4): Electrode fabrication methods include conductive silver paste printing or metal foil bonding; and / or, The electrodes adopt an interdigitated structure.

[0014] Furthermore, in step (4): The electrodes are connected to the signal acquisition device by welding or conductive adhesive bonding; and / or, The width of the interdigitated electrode teeth is 1~3mm, and the spacing between adjacent teeth is 0.5~1mm.

[0015] The present invention also discloses a pressure sensor for use on a metal substrate prepared by the above-described method for preparing a pressure sensor for use on a metal substrate.

[0016] To address the shortcomings of existing pressure sensors, such as poor compatibility, complex processes, limited performance, and insufficient form factor adaptability due to their reliance on PET / PI substrates, the present invention aims to provide a method for fabricating a pressure sensor for metal-based substrate-free encapsulation.

[0017] The core breakthroughs of this invention compared to existing technologies are as follows: Substrate-free design: Abandoning the traditional PET / PI support substrate, the slurry directly bonds with the product under test to form a sensing layer, which solves the problems of poor compatibility and strain transmission caused by the substrate, while simplifying the process and reducing costs; Interface control innovation: By selectively choosing organic resins (metal-epoxy resin), a stable bond is achieved between the slurry and the metal-based material product, with an adhesion grade of ≥4B, breaking through the material compatibility limitations of existing sensors. Synergistic optimization of components: The synergistic effect of graphene and organic resin utilizes the high conductivity and mechanical properties of graphene to ensure sensing sensitivity (0.1~0.5kPa). -1 Furthermore, the interface is firmly bonded through the cross-linking and curing of the resin, with a response time of ≤50ms; Flexible process adaptability: It supports multiple coating methods such as spraying and scraping, and can be adapted to products with different shapes such as flat and curved surfaces, thus expanding the application scenarios of pressure sensors.

[0018] The present invention achieves the following technical effects through the above technical solution, all of which have been verified by experiments: Simplified process and reduced costs: Eliminating steps such as substrate preparation, bonding, and encapsulation shortens the production process by more than 30% and reduces material costs by 25-40%; Strong adhesion: Interface adhesion grade ≥4B (GB / T9286-1998), no peeling or signal drift (≤2%) after 1000 bends (flexible products) or 24h static pressure test. High-performance sensing: Pressure detection range 0~1000kPa, sensitivity 0.1~0.5kPa -1 (20-50% improvement over traditional sensors), response time ≤50ms, strong temperature adaptability (sensitivity change rate ≤5% within the range of -20~60℃). Improved form adaptability: It can be directly fabricated on curved and irregularly shaped product surfaces, solving the problem that traditional substrate sensors are difficult to fit into complex product shapes. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 A schematic diagram of the preparation process of the preparation method of the present invention. Detailed Implementation

[0020] In the following description, only certain exemplary embodiments are depicted simply. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0021] Unless otherwise defined herein, scientific and technical terms used in conjunction with this invention will have the meaning commonly understood by one of ordinary skill in the art. Furthermore, unless the context otherwise requires, singular terms shall include plural forms, and plural terms shall include singular forms. More specifically, as used in this specification and the appended claims, unless the context explicitly indicates otherwise, the singular forms “a,” “an,” and “the” include plural indicators. In this application, unless otherwise stated, the use of “or” means “and / or.” Furthermore, the use of the term “comprising” and other forms such as “including” and “containing” is not limiting. Moreover, the scope provided in the specification and the appended claims includes all values ​​between endpoints. Preferred embodiments of the invention are described below; it should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the invention.

[0022] This invention discloses a method for fabricating a metal-based pressure sensor, such as... Figure 1 As shown, the composition of the graphene strain slurry (weight ratios of each component) is as follows: Sensing body: 5-20 parts of graphene, such as 5, 8, 10, 13, 15, 18, 20 (preferably reduced graphene oxide, with a sheet diameter of 1-10 μm and a thickness of 1-10 nm). Interface modifier: 10~40 parts epoxy resin, for example 10, 15, 20, 25, 30, 35, 40; Solvent: 30-70 parts, for example 30, 35, 40, 45, 50, 55, 60, 65, 70 (one or more of N-methylpyrrolidone, ethanol, ethyl acetate, and deionized water); Dispersant: 1 to 5 parts, for example 1, 2, 3, 4, 5 (one or more of sodium dodecylbenzenesulfonate, polyethylene glycol, and polyvinylpyrrolidone).

[0023] Preparation steps and key conditions: Step 1 (Slurry Preparation): Mix the above components and ultrasonically disperse them at 300~500W, for example, 300W, 350W, 400W, 450W, 500W for 30~60min, for example, 30min, 35min, 40min, 45min, 50min, 55min, 60min; then mechanically stir at 500~1000r / min, for example, 500r / min, 600r / min, 700r / min, 800r / min, 900r / min, 1000r / min for 60~120min, for example, 60min, 70min, 80min, 90min, 100min, 110min, 120min to obtain a uniform and stable graphene strain slurry. Step 2 (Surface Pretreatment): Targeted treatment for metal-based products: sandpaper roughening + ultrasonic cleaning with ethanol; Step 3 (coating without substrate): Use spraying (0.2~0.5MPa, nozzle distance 10~30cm), scraping (#5~#20 wire bar), dip coating or screen printing processes to form a strain sensing layer with a thickness of 5~50μm; Step 4 (Curing Treatment): Adjust the curing conditions according to the type of epoxy resin (epoxy resin 80~120℃ / 0.5~2h); Step 5 (Signal Extraction): Electrodes are prepared by printing conductive silver paste or attaching metal foil, and wires are connected to the signal acquisition device by welding or conductive adhesive bonding.

[0024] To further improve performance, the preferred solutions include: The graphene used is reduced graphene oxide with a sheet diameter of 1~5μm, and the epoxy resin accounts for 20~30% of the total mass of the graphene strain slurry, which can optimize the interfacial bonding force and sensing sensitivity. The coating process should preferably use spraying (for curved products) or scraping (for flat products), and the curing temperature should be controlled at 80~120℃, such as 80℃, 90℃, 100℃, 110℃, 120℃; taking into account both adhesion and production efficiency. The electrodes adopt an interdigitated structure (tooth width 1~3mm, spacing between adjacent teeth 0.5~1mm), which can improve signal stability.

[0025] Example The invention generally described herein will be more readily understood by referring to the following examples, which are provided by way of illustration and are not intended to limit the invention. Furthermore, unless otherwise specified, the experimental methods in the following examples are conventional methods. Unless otherwise specified, the raw materials, reagents, and other materials used in the following examples are commercially available products.

[0026] This section elaborates on the fabrication process of the metal-based substrate-free encapsulated pressure sensor of the present invention through four specific embodiments. Each embodiment includes the applicable scenario, slurry formulation design logic, process parameter selection basis, and performance verification results, comprehensively verifying the feasibility and advantages of the technical solution. All steps and data have been verified by actual experiments and can be repeatedly implemented by those skilled in the art.

[0027] Example 1: I. Slurry Formulation and Preparation By weight, the core raw materials selected are: 10 parts of reduced graphene oxide (sheet diameter 1~5μm, thickness 1~3nm), which has both high conductivity and mechanical strength, and is suitable for the rigid requirements of metal equipment; 25 parts of bisphenol A type epoxy resin; 45 parts of N-methylpyrrolidone as solvent, which has excellent solubility in epoxy resin and can effectively disperse graphene and avoid agglomeration; and 3 parts of polyethylene glycol as dispersant, whose hydrophilic end can adsorb hydroxyl groups on the surface of graphene, and whose hydrophobic end is compatible with epoxy resin, so as to achieve synergistic dispersion.

[0028] Slurry preparation steps: Add the above raw materials to a mixing tank in sequence, first ultrasonically disperse at 300W power for 45 minutes to break up the graphene agglomerates (control the temperature ≤40℃ during ultrasonication to prevent solvent evaporation); then mechanically stir at 800r / min for 90 minutes to ensure uniform mixing of resin and graphene, finally obtaining a solid content of about 35% and a viscosity of 500~800mPa. The uniform slurry showed no stratification after standing for 24 hours.

[0029] II. Surface Pretreatment Metal products typically have an oxide layer and oil stains on their surface, which directly affect the adhesion of the slurry. Therefore, a three-step treatment of "roughening-cleaning-drying" is adopted: First, use 400-grit sandpaper to polish the surface in the same direction to form a fine texture (roughness Ra is controlled at 0.8~1.2μm to increase the contact area); then, place the polished product in an ethanol solution (concentration 95%) and ultrasonically clean it with a power of 500W for 15 minutes to remove surface oil stains and wear debris; finally, place it in a 60℃ forced-air drying oven for 30 minutes to completely remove surface moisture (residual moisture will cause blistering of the sensing layer after curing).

[0030] III. Coating and Curing The sensing layer was prepared by spraying. Since most metal products are flat or have regular curved surfaces, spraying can achieve uniform coverage. The spraying pressure was set to 0.3 MPa (too low a pressure will result in uneven coating, while too high a pressure will waste slurry), the nozzle was 20 cm away from the product surface (too close a distance will cause accumulation, while too far a distance will result in a thin coating), the spraying speed was 10 cm / s, and the coating was sprayed twice in the horizontal direction. After natural leveling for 5 minutes, the thickness of the sensing layer was measured to be 20 μm (this thickness takes into account both conductivity and strain sensitivity; too thin a layer is prone to breakage, while too thick a layer will cause strain transmission lag).

[0031] Curing is achieved through a thermosetting process. The coated product is placed in an 80℃ forced-air drying oven and kept at this temperature for 2 hours. At this temperature, the epoxy resin and curing agent fully cross-link, forming a three-dimensional network structure. This ensures strong adhesion to the stainless steel surface while preventing secondary oxidation of the metal surface due to high temperatures. After curing, the surface of the sensing layer is smooth, without cracks or bubbles.

[0032] IV. Signal Extraction and Performance Testing Signal lead-out: Use a screen printing machine (200 mesh screen) to print conductive silver paste electrodes at both ends of the sensing layer. The electrode size is 5mm×2mm (5mm width to ensure current stability, 2mm length to reduce signal loss). Place in an 80℃ oven to dry for 30 minutes to cure the silver paste. Use a soldering process to solder 0.2mm diameter copper wires to the electrodes. Wrap the lead-out ends of the wires with polytetrafluoroethylene insulating tape to prevent short circuits.

[0033] Performance test results: According to GB / T9286-1998, the cross-cut adhesion test showed an adhesion grade of 5B (no peeling after cross-cut), significantly better than the traditional 3B grade with a PET substrate sensor; testing with a universal testing machine (model UTM-2000, the same for other examples and comparative examples) showed a sensitivity of 0.35 kPa. -1 (Pressure range 0~800kPa), response time 35ms, which can meet the needs of real-time monitoring.

[0034] Example 2: I. Slurry Formulation and Preparation By weight, the core raw materials selected are: 20 parts of reduced graphene oxide (sheet diameter 6~10μm, thickness 6~9nm), which has higher mechanical strength and is suitable for the rigid requirements of metal equipment; 30 parts of bisphenol A type epoxy resin; 60 parts of ethyl acetate as solvent, which has high solubility for epoxy resin and can effectively disperse graphene and avoid agglomeration; and 4 parts of polyvinylpyrrolidone as dispersant.

[0035] Slurry preparation steps: Add the above raw materials to a mixing tank in sequence, first ultrasonically disperse at 400W power for 50 minutes to break up the graphene agglomerates (control the temperature ≤40℃ during ultrasonication to prevent solvent evaporation); then mechanically stir at 1000r / min for 100 minutes to ensure uniform mixing of resin and graphene, finally obtaining a solid content of about 30% and a viscosity of 300~600mPa. The uniform slurry showed no stratification after standing for 24 hours.

[0036] II. Surface Pretreatment Metal products typically have an oxide layer and oil stains on their surface, which directly affect the adhesion of the slurry. Therefore, a three-step treatment of "roughening-cleaning-drying" is adopted: First, use 400-grit sandpaper to polish the surface in the same direction to form a fine texture (roughness Ra is controlled at 0.8~1.2μm to increase the contact area); then, place the polished product in an ethanol solution (concentration 95%) and ultrasonically clean it with a power of 500W for 15 minutes to remove surface oil stains and wear debris; finally, place it in a 60℃ forced-air drying oven for 30 minutes to completely remove surface moisture (residual moisture will cause blistering of the sensing layer after curing).

[0037] III. Coating and Curing The sensing layer was prepared by spraying. Since most metal products are flat or regular curved surfaces, spraying can achieve uniform coverage. The spraying pressure was set to 0.4 MPa (too low a pressure will easily lead to uneven coating, while too high a pressure will waste slurry), the nozzle distance from the product surface was 15 cm (too close a distance will easily cause accumulation, while too far a distance will result in a thin coating), the spraying speed was 10 cm / s, and the coating was sprayed back and forth 3 times in the horizontal direction. After natural leveling for 5 minutes, the thickness of the sensing layer was measured to be 25 μm (this thickness takes into account both conductivity and strain sensitivity; too thin a layer is easy to break, while too thick a layer will cause strain transmission lag).

[0038] Curing is achieved through a thermosetting process. The coated product is placed in a 120℃ forced-air drying oven and kept at this temperature for 1 hour. At this temperature, the epoxy resin and curing agent fully cross-link, forming a three-dimensional network structure. This ensures strong adhesion to the stainless steel surface while preventing secondary oxidation of the metal surface due to high temperatures. After curing, the surface of the sensing layer is smooth, without cracks or bubbles.

[0039] IV. Signal Extraction and Performance Testing Signal extraction: Adhesive electrodes are used. Copper foil with a thickness of 0.05mm is cut into 4mm×2mm electrodes. Conductive adhesive is applied to the contact area between the electrode and the sensing layer. After pressing for 30 seconds, it is left to stand for 1 hour to cure. Silver wires with a diameter of 0.1mm are selected and are bonded to the copper foil with conductive adhesive to avoid soldering.

[0040] Performance test results: According to GB / T9286-1998, the cross-cut adhesion test showed an adhesion grade of 5B (no peeling after cross-cut), significantly better than the traditional 3B grade with a PET substrate sensor; tested using a universal testing machine (model UTM-2000), the sensitivity reached 0.47 kPa. -1 (Pressure range 0~1000kPa), response time 25ms, which can meet the needs of real-time monitoring.

[0041] Example 3: I. Slurry Formulation and Preparation By weight, the core raw materials selected are: 5 parts of reduced graphene oxide (3~7μm in diameter and 4~7nm in thickness), which has higher mechanical strength and is suitable for the rigid requirements of metal equipment; 40 parts of bisphenol A epoxy resin; 70 parts of deionized water as solvent, which has high solubility for epoxy resin and can effectively disperse graphene and prevent agglomeration; and 1 part of sodium dodecylbenzenesulfonate as dispersant.

[0042] Slurry preparation steps: Add the above raw materials to a mixing tank in sequence, first ultrasonically disperse at 350W for 60 minutes to break up the graphene agglomerates (control the temperature ≤40℃ during ultrasonication to prevent solvent evaporation); then mechanically stir at 500r / min for 120 minutes to ensure uniform mixing of resin and graphene, finally obtaining a solid content of about 8% and a viscosity of 100~300mPa. The uniform slurry showed no stratification after standing for 24 hours.

[0043] II. Surface Pretreatment Metal products typically have an oxide layer and oil stains on their surface, which directly affect the adhesion of the slurry. Therefore, a three-step treatment of "roughening-cleaning-drying" is adopted: First, use 400-grit sandpaper to polish the surface in the same direction to form a fine texture (roughness Ra is controlled at 0.8~1.2μm to increase the contact area); then, place the polished product in an ethanol solution (concentration 95%) and ultrasonically clean it with a power of 500W for 15 minutes to remove surface oil stains and wear debris; finally, place it in a 60℃ forced-air drying oven for 30 minutes to completely remove surface moisture (residual moisture will cause blistering of the sensing layer after curing).

[0044] III. Coating and Curing The dip coating process is adopted: the pretreated metal product is slowly immersed in the slurry at a speed of 5cm / s (too fast a speed will easily generate bubbles, too slow a speed will result in an excessively thick coating). After 10s, it is taken out at a uniform speed and allowed to level naturally for 10min. The thickness of the sensing layer is measured to be 15μm. High-temperature thermal curing is adopted: the product is kept at 120℃ in a forced-air drying oven for 0.5h to form a sensing layer that is tightly bonded to the metal surface.

[0045] IV. Signal Extraction and Performance Testing Signal extraction: Adhesive electrodes are used. Copper foil with a thickness of 0.05mm is cut into 3mm×2mm electrodes. Conductive adhesive is applied to the contact area between the electrode and the sensing layer. After pressing for 30 seconds, it is left to stand for 1 hour to cure. Silver wires with a diameter of 0.1mm are selected and are bonded to the copper foil with conductive adhesive to avoid soldering.

[0046] Performance test results: According to GB / T9286-1998, the cross-cut adhesion test showed an adhesion grade of 5B (no peeling after cross-cut), significantly better than the traditional 3B grade with a PET substrate sensor; tested using a universal testing machine (model UTM-2000), the sensitivity reached 0.13 kPa. -1 (Pressure range 0~1000kPa), response time 50ms, which can meet the needs of real-time monitoring.

[0047] Example 4: I. Slurry Formulation and Preparation By weight, the core raw materials selected are: 15 parts of reduced graphene oxide (sheet diameter 5~8μm, thickness 1~4nm) to meet the rigid requirements of metal equipment; 15 parts of bisphenol A epoxy resin; 40 parts of ethanol as solvent, which has high solubility for epoxy resin and can effectively disperse graphene and avoid agglomeration; and 5 parts of polyethylene glycol as dispersant.

[0048] Slurry preparation steps: Add the above raw materials to a mixing tank in sequence, first ultrasonically disperse at 500W power for 40 minutes to break up the graphene agglomerates (control the temperature ≤40℃ during ultrasonication to prevent solvent evaporation); then mechanically stir at 800r / min for 60 minutes to ensure uniform mixing of resin and graphene, finally obtaining a solid content of about 40% and a viscosity of 800~1200mPa. The uniform slurry showed no stratification after standing for 24 hours.

[0049] II. Surface Pretreatment Metal products typically have an oxide layer and oil stains on their surface, which directly affect the adhesion of the slurry. Therefore, a three-step treatment of "roughening-cleaning-drying" is adopted: First, use 400-grit sandpaper to polish the surface in the same direction to form a fine texture (roughness Ra is controlled at 0.8~1.2μm to increase the contact area); then, place the polished product in an ethanol solution (concentration 95%) and ultrasonically clean it with a power of 500W for 15 minutes to remove surface oil stains and wear debris; finally, place it in a 60℃ forced-air drying oven for 30 minutes to completely remove surface moisture (residual moisture will cause blistering of the sensing layer after curing).

[0050] III. Coating and Curing The screen printing process is adopted: a 200-mesh nylon screen is selected, the squeegee pressure is 0.2MPa (too low pressure will result in an unclear pattern, too high pressure will damage the screen), the printing speed is 6cm / s, and an induction layer with a thickness of 18μm is formed; the curing temperature is 100℃, and the temperature is maintained for 1 hour to form an induction layer that is tightly bonded to the metal surface.

[0051] IV. Signal Extraction and Performance Testing Signal lead-out: Use a screen printing machine (200 mesh screen) to print conductive silver paste electrodes at both ends of the sensing layer. The electrode size is 5mm×2mm (5mm width to ensure current stability, 2mm length to reduce signal loss). Place in a 120℃ oven to dry for 30 minutes to cure the silver paste. Use a soldering process to solder 0.2mm diameter copper wires to the electrodes. Wrap the lead-out ends of the wires with polytetrafluoroethylene insulating tape to prevent short circuits.

[0052] Performance test results: According to GB / T9286-1998, the cross-cut adhesion test showed an adhesion grade of 5B (no peeling after cross-cut), significantly better than the traditional 3B grade with a PET substrate sensor; tested using a universal testing machine (model UTM-2000), the sensitivity reached 0.24 kPa. -1 (Pressure range 0~600kPa), response time 30ms, which can meet the needs of real-time monitoring.

[0053] Comparative Example 1: I. Slurry Formulation and Preparation By weight, the core raw materials selected are: 20 parts of reduced graphene oxide (sheet diameter 8~11μm, thickness 10~13nm); 50 parts of bisphenol A type epoxy resin; 20 parts of N-methylpyrrolidone is selected as the solvent, which has high solubility for epoxy resin and can effectively disperse graphene and avoid agglomeration; and 8 parts of polyethylene glycol is selected as the dispersant.

[0054] Slurry preparation steps: Add the above raw materials to a mixing tank in sequence, first ultrasonically disperse at 500W power for 40 minutes to break up the graphene agglomerates (control the temperature ≤40℃ during ultrasonication to prevent solvent evaporation); then mechanically stir at 600r / min for 90 minutes to ensure uniform mixing of resin and graphene, finally obtaining a solid content of approximately 35% and a viscosity of 600~1000mPa. The uniform slurry showed no stratification after standing for 24 hours.

[0055] II. Surface Pretreatment Metal products typically have an oxide layer and oil stains on their surface, which directly affect the adhesion of the slurry. Therefore, a three-step treatment of "roughening-cleaning-drying" is adopted: First, use 400-grit sandpaper to polish the surface in the same direction to form a fine texture (roughness Ra is controlled at 0.8~1.2μm to increase the contact area); then, place the polished product in an ethanol solution (concentration 95%) and ultrasonically clean it with a power of 500W for 15 minutes to remove surface oil stains and wear debris; finally, place it in a 60℃ forced-air drying oven for 30 minutes to completely remove surface moisture (residual moisture will cause blistering of the sensing layer after curing).

[0056] III. Coating The induction layer was prepared by spraying. Since most metal products are flat or regular curved surfaces, spraying can achieve uniform coverage. The spraying pressure was set to 0.4 MPa (too low a pressure will easily lead to uneven coating, while too high a pressure will waste slurry), the nozzle was 20 cm away from the product surface (too close a distance will easily cause accumulation, while too far a distance will result in a thin coating), the spraying speed was 10 cm / s, and the coating was sprayed three times in the horizontal direction. After natural leveling for 5 minutes, the thickness of the induction layer was measured to be 30 μm.

[0057] IV. Signal Extraction and Performance Testing Signal lead-out: Use a screen printing machine (200 mesh screen) to print conductive silver paste electrodes at both ends of the sensing layer. The electrode size is 4mm×2mm (4mm width to ensure current stability, 2mm length to reduce signal loss). Place in a 100℃ oven to dry for 30 minutes to cure the silver paste. Use a soldering process to solder 0.2mm diameter copper wires to the electrodes. Wrap the lead-out ends of the wires with polytetrafluoroethylene insulating tape to prevent short circuits.

[0058] Performance test results: According to GB / T9286-1998, the adhesion grade was 4B (no peeling after crossing the grid); tested with a universal testing machine (model UTM-2000), the sensitivity reached 0.08 kPa. -1 (Pressure range 0~800kPa), response time 60ms.

[0059] Comparative Example 2: I. Slurry Formulation and Preparation By weight, the core raw materials selected are: 5 parts of reduced graphene oxide (sheet diameter 3~7μm, thickness 13~17nm); 20 parts of bisphenol A type epoxy resin; 80 parts of deionized water is selected as the solvent, which has high solubility for epoxy resin and can effectively disperse graphene and avoid agglomeration; and 1 part of polyvinylpyrrolidone is selected as the dispersant.

[0060] Slurry preparation steps: Add the above raw materials to a mixing tank in sequence, first ultrasonically disperse at 300W power for 60 minutes to break up the graphene agglomerates (control the temperature ≤40℃ during ultrasonication to prevent solvent evaporation); then mechanically stir at 1000r / min for 60 minutes to ensure uniform mixing of resin and graphene, finally obtaining a solid content of about 5% and a viscosity of 300~600mPa. The uniform slurry showed no stratification after standing for 24 hours.

[0061] II. Surface Pretreatment Metal products typically have an oxide layer and oil stains on their surface, which directly affect the adhesion of the slurry. Therefore, a three-step treatment of "roughening-cleaning-drying" is adopted: First, use 400-grit sandpaper to polish the surface in the same direction to form a fine texture (roughness Ra is controlled at 0.8~1.2μm to increase the contact area); then, place the polished product in an ethanol solution (concentration 95%) and ultrasonically clean it with a power of 500W for 15 minutes to remove surface oil stains and wear debris; finally, place it in a 60℃ forced-air drying oven for 30 minutes to completely remove surface moisture (residual moisture will cause blistering of the sensing layer after curing).

[0062] III. Coating and Curing The dip coating process is adopted: the pretreated metal product is slowly immersed in the slurry at a speed of 5cm / s (too fast a speed will easily generate bubbles, too slow a speed will result in an excessively thick coating). After 15s, it is taken out at a uniform speed and allowed to level naturally for 10min. The thickness of the sensing layer is measured to be 20μm. High-temperature thermal curing is adopted: the product is kept at 100℃ in a forced-air drying oven for 1h to form a sensing layer that is tightly bonded to the metal surface.

[0063] IV. Signal Extraction and Performance Testing Signal extraction: Adhesive electrodes are used. Copper foil with a thickness of 0.08mm is cut into 3mm×3mm electrodes. Conductive adhesive is applied to the contact area between the electrode and the sensing layer. After pressing for 30 seconds, it is left to stand for 1 hour to cure. Copper wires with a diameter of 0.2mm are selected and are bonded to the copper foil with conductive adhesive to avoid soldering.

[0064] Performance test results: According to GB / T9286-1998, the cross-cut adhesion test showed an adhesion grade of 4B (no peeling after cross-cut); tested with a universal testing machine (model UTM-2000), the sensitivity reached 0.05 kPa. -1 (Pressure range 0~400kPa), response time 80ms.

[0065] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention. Furthermore, although the elements of the present invention can be described or claimed individually, it is also conceivable to have multiple elements, unless explicitly limited to a single element.

Claims

1. A method for fabricating a pressure sensor based on a metal substrate, characterized in that, Includes the following steps: (1) Preparation of slurry: Based on the weight ratio of each component, disperse and mix 5-20 parts of graphene, 10-40 parts of epoxy resin, 30-70 parts of solvent and 1-5 parts of dispersant to obtain graphene strain slurry. (2) Metal substrate surface pretreatment: The metal substrate surface is roughened and then cleaned; (3) Coating and curing: Graphene strain slurry is coated onto the pretreated metal substrate surface to form a strain sensing layer, and then cured by heating; (4) Signal extraction: Connect electrodes to the cured strain sensing layer.

2. The method for fabricating a metal-based pressure sensor according to claim 1, characterized in that, In step (1): Graphene is reduced graphene oxide; and / or, The epoxy resin is a bisphenol A type epoxy resin; and / or, The solvent is one or more of N-methylpyrrolidone, ethanol, ethyl acetate, and water; and / or, The dispersant is one or more of sodium dodecylbenzenesulfonate, polyethylene glycol, and polyvinylpyrrolidone.

3. The method for fabricating a metal-based pressure sensor according to claim 2, characterized in that, In step (1): Graphene sheets with a diameter of 0.5~10μm and a thickness of 0.8~10nm; and / or, The dispersion and mixing process consists of ultrasonic dispersion at 300-500W for 30-60 minutes and mechanical stirring at 500-1000r / min for 60-120 minutes.

4. The method for fabricating a metal-based pressure sensor according to claim 3, characterized in that, In step (1): Graphene sheets with diameters of 1~5μm The components are: graphene (15-16 parts), epoxy resin (22-27 parts), solvent (40-60 parts), and dispersant (2-4 parts).

5. The method for fabricating a metal-based pressure sensor according to claim 4, characterized in that, In step (1): Epoxy resin accounts for 20-30% of the total mass of the graphene strain slurry; and / or, The dispersion and mixing process consists of ultrasonic dispersion at 350~450W for 40~55min and mechanical stirring at 600~800r / min for 80~100min.

6. The method for fabricating a metal-based pressure sensor according to claim 1, characterized in that, In step (2): After roughening, the surface roughness Ra of the metal substrate is 0.8~1.2 μm; and / or, The cleaning process is ultrasonic cleaning in an ethanol solution; and / or, The metal substrate is dried after cleaning.

7. The method for fabricating a metal-based pressure sensor according to claim 6, characterized in that, In step (2): The ethanol solution concentration is 95%; and / or The ultrasonic cleaning is performed at 500W power for 15 minutes; and / or, The drying process involves drying in a 60°C forced-air drying oven for 30 minutes.

8. The method for fabricating a metal-based pressure sensor according to claim 1, characterized in that, In step (3): The coating method is one of the following processes: spraying, scraping, dipping, or screen printing; and / or, The strain-sensing layer formed after coating is 5~50μm thick; and / or, The curing process involves treating at 80~120℃ for 0.5~2 hours.

9. The method for fabricating a metal-based pressure sensor according to claim 8, characterized in that, In step (3): Spraying pressure is 0.2~0.5MPa, nozzle distance is 10~30cm; and / or, Use #5~#20 wire rods for scraping.

10. The method for fabricating a metal-based pressure sensor according to claim 8, characterized in that, In step (3): The strain-sensing layer formed after coating is 15~40μm thick; and / or, The curing process involves treating at 90~110℃ for 0.8~1.5 hours.

11. The method for fabricating a metal-based pressure sensor according to claim 1, characterized in that, In step (4): Electrode fabrication methods include conductive silver paste printing or metal foil bonding; and / or, The electrodes adopt an interdigitated structure.

12. The method for fabricating a metal-based pressure sensor according to claim 11, characterized in that, In step (4): The electrodes are connected to the signal acquisition device by welding or conductive adhesive bonding; and / or, The width of the interdigitated electrode teeth is 1~3mm, and the spacing between adjacent teeth is 0.5~1mm.

13. A pressure sensor for a metal substrate prepared by the method for preparing a pressure sensor for a metal substrate as described in any of the preceding claims.

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