Flexible high-temperature resistant oil film pressure sensor based on bionic cracked beam membrane structure

Abstract

A flexible, high-temperature resistant oil film pressure sensor based on a bionic crack beam membrane structure, the sensor comprising an upper flexible sensitive film based on microcracks and a lower cavity support membrane bonded together; the upper flexible sensitive film based on microcracks comprises a polyimide substrate, a grid-like microgroove is etched on the lower surface of the polyimide substrate, the grid-like microgroove is embedded in a low-dimensional conductive material to form a conductive network, and the conductive network has distributed microcracks; electrodes are evaporated on the lower surface of the polyimide substrate; a cavity is provided on the upper surface of the lower cavity support membrane, and a secondary support structure is provided inside the cavity; the manufacturing process comprises first preparing an upper polyimide substrate and a lower cavity support structure, evaporating electrodes, filling low-dimensional conductive materials, pre-stretching to induce cracks, and bonding the upper polyimide substrate and the lower cavity support membrane; the sensor of the present invention is flexible and can be fitted inside the bearing of large equipment to detect the continuous distribution state of oil film pressure in situ, has the advantages of high temperature resistance and high frequency response, and has a simple manufacturing process.

Description

Technical Field

[0001] The present invention belongs to the technical field of micro-nano manufacturing and flexible sensors, and in particular relates to a flexible high-temperature resistant oil film pressure sensor based on a bionic cracked beam membrane structure. Background Art

[0002] In rotating machinery, oil films play a vital role in lubrication, friction reduction, and load bearing. Measuring oil film pressure and its distribution has long been a challenging issue in the field of rotor dynamics. High-temperature oil film pressure distribution testing technology is crucial for systematic research on the operating status of bearing support structures, structural design optimization, and rotor dynamics. In large rotating machinery, the oil film experiences high temperatures, heavy loads, complex distribution, and rapid changes. Therefore, real-time oil film pressure measurement places extremely high demands on sensors. Traditional measurement methods primarily include two: one involves drilling pressure-conducting holes in bearings or bushings and installing pressure gauges for oil pressure testing. This drilling method reduces component stiffness, alters the original oil film pressure characteristics, and results in significant measurement errors. Another method involves installing fiber optic or MEMS sensors. While this method is more sensitive and accurate, the number of sensors that can be installed is limited, making it impossible to measure the continuous distribution of oil film pressure. Therefore, conformal, in-situ mounting of arrayed flexible thin-film sensors is an effective solution for continuous oil film pressure measurement.

[0003] Current flexible thin film sensors still face technical difficulties in terms of material temperature resistance, pressure bearing capacity and high-frequency response, making them difficult to apply to high-temperature, high-pressure and rapidly changing oil film pressure monitoring environments. Therefore, there is an urgent need for a high-temperature and high-pressure resistant, fast-response flexible thin film pressure sensor to achieve accurate detection of the real-time distribution status of oil film pressure. Summary of the Invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a flexible, high-temperature resistant oil film pressure sensor based on a bionic cracked beam membrane structure. The sensor can be conformally attached to the surface of the rotating machinery support structure to realize the detection of the continuous distribution state of the oil film pressure, and has the advantages of high temperature resistance, high pressure resistance and high frequency response; the manufacturing process is simple and easy to implement, and the repeatability is high.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A flexible high-temperature resistant oil film pressure sensor based on a bionic cracked beam membrane structure comprises an upper flexible sensitive film based on microcracks and a lower cavity support membrane, wherein the upper flexible sensitive film based on microcracks and the lower cavity support membrane are bonded to form an integral film by an adhesive;

[0007] The upper layer of the flexible sensitive film based on microcracks includes a polyimide substrate, a grid-like micro-groove is etched on the lower surface of the polyimide substrate, a low-dimensional conductive material is embedded in the grid-like micro-groove to form a conductive network, and microcracks are distributed in the conductive network; an electrode is evaporated on the lower surface of the polyimide substrate, and the electrode is connected to the conductive network;

[0008] A cavity is provided on the upper surface of the lower cavity support membrane, and a secondary support structure is provided inside the cavity.

[0009] The thickness of the upper layer of flexible sensitive film based on microcracks is 10 μm to 50 μm.

[0010] The thickness of the lower cavity support membrane is 50 μm to 200 μm.

[0011] The grid-like microchannels and the secondary support structure are both formed by patterned micromachining of polyimide.

[0012] The grid-like microchannel has a line width of 2 μm to 10 μm, a period of 50 μm to 200 μm, and a depth of 2 μm to 20 μm.

[0013] The cavity depth is 30 μm to 100 μm, the cavity pattern includes square, circle and other polygons, and the characteristic size of the cavity pattern is 2 mm to 10 mm.

[0014] The secondary support structure includes micro cylinders and prisms, with characteristic dimensions of 100 μm to 500 μm and a center distance of 200 μm to 2 mm.

[0015] The thickness of the electrode is 100nm to 300nm.

[0016] The low-dimensional conductive material is carbon nanotube or graphene; the adhesive is polyimide or epoxy glue; and the electrode material is gold, platinum, silver or copper.

[0017] The manufacturing process of the flexible high-temperature resistant oil film pressure sensor based on the bionic cracked beam membrane structure comprises the following steps:

[0018] The first step is the preparation of the upper polyimide substrate and the lower cavity support structure: the upper polyimide substrate and the lower cavity support film adopt the same patterning process. First, an aluminum mask is deposited on the polyimide film by evaporation or sputtering. Then, the process is carried out in sequence: coating, pre-baking, exposure, development, post-baking, aluminum etching, debonding, etching, and aluminum removal to obtain the respective micro-pattern structures.

[0019] The second step is electrode evaporation: under the cover of a hollow mask, metal electrode patterns are deposited on both ends of the upper polyimide substrate;

[0020] The third step is filling low-dimensional conductive materials: a low-dimensional conductive material dispersion is filled into the grid-like micro-channels of the upper polyimide substrate by a doctor blade method. After the solvent evaporates, an embedded and continuously distributed conductive network is formed.

[0021] Step 4: Pre-stretching to induce cracks: By pre-stretching the upper polyimide substrate in a directional and quantitative manner, microcracks are induced in the conductive network formed by the low-dimensional conductive material;

[0022] The fifth step is to bond the upper polyimide substrate and the lower cavity support film: using an adhesive, the upper polyimide substrate and the lower cavity support film are bonded into an integrated film by a rolling method.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) The sensor of the present invention utilizes the opening and closing changes of microcracks distributed in low-dimensional conductive materials to achieve pressure sensing. It has a very high response frequency, overcomes the slow response and hysteresis characteristics of traditional flexible resistive pressure sensors, and is suitable for detecting rapidly changing oil film pressure.

[0025] (2) The sensor of the present invention can be conformally attached and detect the continuous distribution state of the oil film pressure in situ, which is of great significance for analyzing the working state of rotating machinery and fault detection and diagnosis; the sensor of the present invention has a flexible thin film structure and is easy to realize array distribution; the sensor of the present invention is light, thin and compact, and can be conformally attached to the narrow space of supporting components such as bearings and bushings without destroying the bearing structure and the original distribution state of the oil film.

[0026] (3) The sensor of the present invention is resistant to high temperature and high pressure. The polyimide substrate, adhesive and low-dimensional conductive material used have good thermal stability and are suitable for high-temperature oil film pressure detection of rotating machinery that operates continuously for a long time. The designed cavity support structure can still ensure the recovery of the sensitive layer of the sensor after being subjected to high pressure, so it can detect extremely high pressure and has a wide detection range. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a structural cross-sectional view of the oil film pressure sensor of the present invention.

[0028] Figure 2 This is a working principle diagram of the oil film pressure sensor of the present invention.

[0029] Figure 3 Schematic diagram of the upper layer of the flexible sensitive film based on microcracks of the present invention.

[0030] Figure 4 Schematic diagram of the lower cavity support structure of the present invention.

[0031] Figure 5This is an SEM image of the microcrack morphology formed in the carbon nanotube conductive network after the upper flexible sensitive film of the present invention is pre-stretched. DETAILED DESCRIPTION

[0032] The present invention will be described in detail below with reference to the following examples and accompanying drawings. The following examples are intended to help those skilled in the art better understand the present invention, but are not intended to limit the present invention in any way. It should be noted that, without inventive effort, those skilled in the art may make variations or improvements in materials or structures based on the basic concept of the present invention, and these variations or improvements fall within the scope of protection of the present invention.

[0033] like Figure 1 、 Figure 2 As shown, a flexible high-temperature resistant oil film pressure sensor based on a bionic cracked beam membrane structure includes an upper flexible sensitive film based on microcracks and a lower cavity support membrane 7. The upper flexible sensitive film based on microcracks and the lower cavity support membrane 7 are bonded into an integral film by an epoxy adhesive 6 with high strength, high temperature resistance and good chemical stability.

[0034] like Figure 1 、 Figure 2 、 Figure 3 As shown, the upper layer of the flexible sensitive film based on microcracks includes a polyimide substrate 1, a grid of microgrooves is etched on the lower surface of the polyimide substrate 1, and carbon nanotubes 2 are embedded in the grid of microgrooves to form a conductive network. The conductive network is distributed with microcracks 8; an electrode 3 is evaporated on the lower surface of the polyimide substrate 1, and the electrode 3 is connected to the conductive network. The electrode 3 is formed by evaporating 200nm of gold on the polyimide substrate 1;

[0035] like Figure 1 、 Figure 2 、 Figure 4 As shown, a cavity 4 is provided on the upper surface of the lower cavity support membrane 7 , and a secondary support structure 5 is provided inside the cavity 4 .

[0036] The thickness of the upper layer of flexible sensitive film based on microcracks is 30 μm.

[0037] The thickness of the lower cavity support membrane 7 is 100 μm.

[0038] The grid-like micro-channels and the secondary support structure 5 are both formed by patterned micro-machining of polyimide.

[0039] The grid-like microchannel has a line width of 10 μm, a period of 100 μm, and a depth of 10 μm.

[0040] The cavity 4 has a depth of 100 μm, a pattern of the cavity 4 is a square, and a characteristic dimension of the pattern of the cavity 4, namely a side length, is 10 mm.

[0041] The secondary support structure 5 is in the shape of a micro cylinder, and its characteristic dimensions, namely, radius, is 100 μm and center distance is 2 mm.

[0042] The thickness of the electrode 3 is 200 nm.

[0043] The working principle of the sensor of the present invention is as follows: Figure 2 As shown in the figure, when the oil film pressure acts on the sensor surface, the polyimide substrate 1 will undergo a concave deformation under the action of pressure. Under the action of bending strain, the width of the microcracks 8 of the conductive network formed by the carbon nanotubes 2 embedded in the grid-like micro-grooves of the polyimide substrate 1 increases, resulting in a reduction in the charge path and an increase in resistance. The sensor can detect the size of the oil film pressure based on the resistance. The cavity 4 of the lower cavity support film 7 provides a deformation space for the upper flexible sensitive film based on microcracks. On the one hand, the secondary support structure 5 causes stress concentration in the upper flexible sensitive film based on microcracks, thereby opening the microcracks 8 in the conductive network of the carbon nanotubes 2 to a greater extent, causing a greater resistance change, thereby improving the sensitivity of the sensor. On the other hand, the secondary support structure 5 effectively supports the upper flexible sensitive film based on microcracks to prevent it from completely collapsing under a smaller pressure, thereby improving the pressure resistance of the sensor and broadening the pressure measurement range of the sensor.

[0044] The preparation process of the flexible high-temperature resistant oil film pressure sensor based on the bionic cracked beam membrane structure comprises the following steps:

[0045] The first step is to prepare the upper polyimide substrate and the lower cavity support membrane: the patterning process used for the upper polyimide substrate and the lower cavity support membrane is the same. First, a 200nm aluminum mask is deposited on the polyimide film by evaporation or sputtering, and then the photoresist EPG535 is applied at a speed of 1000r / min for 40s, followed by pre-baking on a 95℃ hot plate for 5min; after the pre-baking is completed, it is exposed on a photolithography machine for 8s, followed by development in a 0.5% sodium hydroxide deionized water solution for about 15s; then The film was then post-baked on a 95°C hot plate for 30 minutes to prevent the photoresist from falling off during the subsequent aluminum etching process. After the post-baking was completed, the film was immersed in a 70°C aluminum etching solution for 40 seconds to etch away the aluminum on the structure to be etched. The film was then immersed in ethanol and ultrasonically treated for 30 minutes to remove the resist, forming a patterned aluminum mask. Oxygen dry etching was then used to etch grid-like micro-grooves and cavity support structures on the upper and lower polyimide films, respectively. Finally, all aluminum on the film was removed using the aforementioned aluminum etching method, thereby obtaining respective micro-pattern structures.

[0046] The second step is to evaporate gold electrodes: Under the cover of a hollow mask, evaporate 200nm gold electrode patterns on both ends of the upper polyimide substrate;

[0047] The third step is filling the low-dimensional conductive material: 10% carbon nanotube aqueous dispersion is evenly filled into the grid-like micro-channels of the upper polyimide substrate by doctor blade coating. The mixture is left at room temperature for about 10 minutes. After the solvent evaporates, the carbon nanotube film on the surface is wiped off, forming an embedded and continuously distributed conductive network in the grid-like micro-channels.

[0048] Step 4: Pre-stretching to induce cracks: The upper polyimide substrate is pre-stretched by 5% for about 30 times to induce microcracks in the conductive network formed by carbon nanotubes. The morphology of the microcracks after pre-stretching is as follows: Figure 5 As shown;

[0049] The fifth step is to bond the upper polyimide substrate and the lower cavity support membrane: use high temperature resistant epoxy glue to bond the upper polyimide substrate and the lower cavity support membrane into an integrated film by rolling.

Claims

1. A flexible, high-temperature-resistant oil film pressure sensor based on a bionic cracked beam membrane structure, used to measure the continuous distribution state of oil film pressure, characterized by: The invention comprises an upper flexible sensitive film based on microcracks and a lower cavity support film, wherein the upper flexible sensitive film based on microcracks and the lower cavity support film are bonded to form an integral film by an adhesive; The upper layer of the flexible sensitive film based on microcracks includes a polyimide substrate, the lower surface of the polyimide substrate is etched with a grid of micro-grooves, the grid-shaped micro-grooves have a line width of 2μm to 10μm, a period of 50μm to 200μm, and a depth of 2μm to 20μm; a low-dimensional conductive material is embedded in the grid-shaped micro-grooves to form a conductive network, and the conductive network is distributed with microcracks; the lower surface of the polyimide substrate is evaporated with electrodes, and the electrodes are connected to the conductive network; A cavity is provided on the upper surface of the lower cavity support membrane, and a secondary support structure is provided inside the cavity.

2. The flexible high-temperature resistant oil film pressure sensor based on the bionic cracked beam membrane structure according to claim 1, characterized in that: The thickness of the upper layer of flexible sensitive film based on microcracks is 10 μm to 50 μm.

3. The flexible high-temperature resistant oil film pressure sensor based on the bionic cracked beam membrane structure according to claim 1 is characterized in that: The thickness of the lower cavity support membrane is 50 μm to 200 μm.

4. The flexible high-temperature resistant oil film pressure sensor based on the bionic cracked beam membrane structure according to claim 1, characterized in that: The grid-like microchannels and the secondary support structure are both formed by patterned micromachining of polyimide.

5. The flexible high-temperature resistant oil film pressure sensor based on the bionic cracked beam membrane structure according to claim 1 is characterized in that: The cavity depth is 30 μm to 100 μm, the cavity pattern includes square, circle and other polygons, and the characteristic size of the cavity pattern is 2 mm to 10 mm.

6. The flexible high-temperature resistant oil film pressure sensor based on the bionic cracked beam membrane structure according to claim 1, characterized in that: The secondary support structure includes micro cylinders and prisms, with characteristic dimensions of 100 μm to 500 μm and a center distance of 200 μm to 2 mm.

7. The flexible high-temperature resistant oil film pressure sensor based on the bionic cracked beam membrane structure according to claim 1, characterized in that: The thickness of the electrode is 100nm to 300nm.

8. The flexible high-temperature resistant oil film pressure sensor based on the bionic cracked beam membrane structure according to claim 1, characterized in that: The low-dimensional conductive material is carbon nanotube or graphene; the adhesive is polyimide or epoxy glue; and the electrode material is gold, platinum, silver or copper.

9. The manufacturing process of the flexible high-temperature resistant oil film pressure sensor based on the bionic cracked beam membrane structure according to claim 1 is characterized in that: The following steps are involved: The first step is the preparation of the upper polyimide substrate and the lower cavity support structure: the upper polyimide substrate and the lower cavity support film adopt the same patterning process. First, an aluminum mask is deposited on the polyimide film by evaporation or sputtering. Then, the process is carried out in sequence: coating, pre-baking, exposure, development, post-baking, aluminum etching, debonding, etching, and aluminum removal to obtain the respective micro-pattern structures. The second step is electrode evaporation: under the cover of a hollow mask, metal electrode patterns are deposited on both ends of the upper polyimide substrate; The third step is filling low-dimensional conductive materials: a low-dimensional conductive material dispersion is filled into the grid-like micro-channels of the upper polyimide substrate by a doctor blade method. After the solvent evaporates, an embedded and continuously distributed conductive network is formed. Step 4: Pre-stretching to induce cracks: By pre-stretching the upper polyimide substrate in a directional and quantitative manner, microcracks are induced in the conductive network formed by the low-dimensional conductive material; The fifth step is to bond the upper polyimide substrate and the lower cavity support film: using an adhesive, the upper polyimide substrate and the lower cavity support film are bonded into an integrated film by a rolling method.

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