Flexible surface acoustic wave sensor preparation method and flexible surface acoustic wave sensor

Abstract

The invention discloses a flexible surface acoustic wave sensor preparation method and a flexible surface acoustic wave sensor, and the method comprises the steps: obtaining three substrate layers, and forming a cavity which penetrates through a second substrate layer in the thickness direction of the second substrate layer in the second substrate layer; the first substrate layer and the second substrate layer are stacked on the two sides of the second substrate layer respectively, and the cavity is filled with a heat volatilization material; the first substrate layer, the second substrate layer and the third substrate layer are laminated, and the high-temperature-resistant flexible substrate is obtained; depositing a piezoelectric film on the first surface of the high-temperature-resistant flexible substrate; and preparing the surface acoustic wave sensor on the piezoelectric film, and heating the high-temperature-resistant flexible substrate to volatilize the thermal volatilization material in the cavity. The flexible surface acoustic wave sensor is a sensing device prepared by the method. According to the invention, the high-temperature test requirement of the special-shaped component can be met, and the processing quality is ensured.

Description

Technical Field

[0001] This invention relates to the field of curved surface sensing and testing technology, and in particular to a method for preparing a flexible surface acoustic wave sensor and the flexible surface acoustic wave sensor itself. Background Technology

[0002] Hypersonic vehicles play an irreplaceable role in aerospace, defense, and other fields. During high-speed operation, friction with the air causes thermal expansion and contraction, resulting in elastic deformation of the fuselage. This severely affects the strength and rigidity of the fuselage, posing significant safety hazards. In the aerospace field, turbine blades of space engines operate in extremely harsh environments with ultra-high temperatures, strong airflow, and intense vibrations. Rapid temperature changes make the blades highly susceptible to damage, potentially shortening the equipment's lifespan and severely impacting the safety and reliability of space engines. Therefore, real-time, in-situ high-temperature safety monitoring of critical equipment in aerospace, defense, and other fields is essential.

[0003] While conventional sensors can acquire and transmit information such as temperature and pressure via cables, their sensing parameters are significantly affected by high-temperature and high-pressure environments. Furthermore, existing high-temperature resistant surface acoustic wave (SAW) sensors can acquire information in high-temperature environments, but their piezoelectric substrates are mostly made of high-temperature resistant, hard, and brittle piezoelectric single crystals, which are highly rigid and have almost no ductility, failing to meet the high-temperature testing requirements of irregularly shaped components. Therefore, there is an urgent need to overcome traditional limitations in sensor structure design and manufacturing, as well as methods for forming irregularly shaped surfaces, to achieve highly reliable operation of SAW sensing devices under complex and extreme conditions such as high temperature and high pressure. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a flexible surface acoustic wave sensor and a flexible surface acoustic wave sensor, so as to solve the problems existing in the prior art, meet the high temperature testing requirements of irregularly shaped components, and ensure the processing quality.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] This invention provides a method for fabricating a flexible surface acoustic wave sensor, comprising the following steps:

[0007] S1. A high-temperature resistant flexible substrate is prepared by means of: obtaining a first substrate layer, a second substrate layer, and a third substrate layer, wherein the first substrate layer, the second substrate layer, and the third substrate layer are all high-temperature resistant flexible substrates; forming a cavity in the second substrate layer that penetrates the second substrate layer along the thickness direction of the second substrate layer; stacking the first substrate layer and the second substrate layer on both sides of the second substrate layer respectively and filling the cavity with a heat-volatile material; laminating the first substrate layer, the second substrate layer, and the third substrate layer to obtain the high-temperature resistant flexible substrate;

[0008] S2. Deposit a piezoelectric thin film on the first surface of the high-temperature resistant flexible substrate;

[0009] S3. A surface acoustic wave sensor is fabricated on the piezoelectric film, and the high-temperature resistant flexible substrate is heated to cause the thermally volatile material in the cavity to volatilize.

[0010] Preferably, S3 further includes: coating a high-temperature resistant adhesive layer on the second surface of the high-temperature resistant flexible substrate, the second surface being a surface on the high-temperature resistant flexible substrate that is opposite to the first surface; and after the flexible surface acoustic wave sensor is bonded to the structure to be tested by the high-temperature resistant adhesive layer, the flexible surface acoustic wave sensor is then heated to completely evaporate the thermally volatile material in the cavity.

[0011] Preferably, S3 further includes: processing an antenna structure on the portion of the first surface where the piezoelectric thin film is not deposited.

[0012] Preferably, S1 further includes: the profile dimension of the cavity cut on the second substrate layer is larger than the design value of the profile dimension of the pressure cavity of the flexible surface acoustic wave sensor by a shrinkage rate, wherein the shrinkage rate is the shrinkage rate of the second substrate layer.

[0013] Preferably, S1 further includes: a lamination method for the first substrate layer, the second substrate layer, and the third substrate layer comprising: placing the first substrate layer, the second substrate layer, and the third substrate layer, after being stacked and filled with the heat-volatile material, into a vacuum bag; first evacuating the vacuum bag; then laminating the first substrate layer, the second substrate layer, and the third substrate layer inside the vacuum bag to obtain a laminated integral structure; and cutting the laminated integral structure to obtain the high-temperature resistant flexible substrate.

[0014] Preferably, S1 further includes: the outline dimension of the high-temperature resistant flexible substrate obtained by cutting the laminated integral structure is larger than the design value of the outline dimension of the flexible substrate of the flexible surface acoustic wave sensor by a shrinkage rate, wherein the shrinkage rate is the shrinkage rate of the high-temperature resistant flexible substrate.

[0015] Preferably, the first substrate layer, the second substrate layer, and the third substrate layer are all made of green ceramic tape, and the piezoelectric film is an aluminum nitride piezoelectric film.

[0016] Preferably, the surface acoustic wave sensor includes a temperature sensing unit and a pressure sensing unit, wherein the pressure sensing unit is disposed opposite to the cavity.

[0017] Preferably, S2 further includes: depositing the piezoelectric thin film on the first surface of the high-temperature resistant flexible substrate using pulsed laser deposition technology; S3 further includes: fabricating the surface acoustic wave sensor on the piezoelectric thin film using nanoimprinting technology, and processing the antenna structure on the first surface using screen printing technology.

[0018] This invention also provides a flexible surface acoustic wave (SAW) sensor, comprising a high-temperature resistant flexible substrate, a piezoelectric thin film, and a SAW sensor; the high-temperature resistant flexible substrate comprises a first substrate layer, a second substrate layer, and a third substrate layer arranged sequentially, all of which are high-temperature resistant flexible substrates; a cavity penetrating the second substrate layer along its thickness direction is formed in the second substrate layer; the first substrate layer, the second substrate layer, and the third substrate layer are fixedly connected by lamination technology; the cavity can be filled with a thermally volatile material, which provides support for the first substrate layer and the third substrate layer during lamination; the piezoelectric thin film is disposed on the first surface of the high-temperature resistant flexible substrate; and the SAW sensor is disposed on the piezoelectric thin film.

[0019] The present invention achieves the following technical effects compared to the prior art:

[0020] This invention provides a method for fabricating a flexible surface acoustic wave (SAW) sensor and the SAW sensor itself. The method includes the following steps: S1, fabricating a high-temperature resistant flexible substrate, the fabrication method including: obtaining a first substrate layer, a second substrate layer, and a third substrate layer, all of which are high-temperature resistant flexible substrates; creating a cavity penetrating the second substrate layer along its thickness direction; stacking the first substrate layer and the second substrate layer on both sides of the second substrate layer and filling the cavity with a thermally volatile material; laminating the first substrate layer, the second substrate layer, and the third substrate layer to obtain the high-temperature resistant flexible substrate; S3, heating the high-temperature resistant flexible substrate to evaporate the thermally volatile material in the cavity, and fabricating a SAW sensor on a piezoelectric thin film.

[0021] The device includes a high-temperature resistant flexible substrate, a piezoelectric film, and a surface acoustic wave sensor. The high-temperature resistant flexible substrate includes a first substrate layer, a second substrate layer, and a third substrate layer arranged sequentially. The first substrate layer, the second substrate layer, and the third substrate layer are all high-temperature resistant flexible substrates. The cavity can be filled with a thermally volatile material, which provides support for the first substrate layer and the third substrate layer during the lamination process.

[0022] This invention utilizes lamination technology to prepare a high-temperature resistant flexible substrate, thereby forming a flexible surface acoustic wave sensor. This sensor exhibits good ductility and can fit seamlessly with the component under test, particularly meeting the high-temperature testing requirements of irregularly shaped components. Furthermore, before laminating the first, second, and third substrate layers, a thermally volatile material is filled into the cavity. This material supports the first and third substrate layers during lamination, preventing them from sinking into the cavity and ensuring processing quality. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of the flexible surface acoustic wave sensor provided in Example 3;

[0025] Figure 2 A schematic diagram of the high-temperature resistant flexible substrate with a piezoelectric thin film deposited according to the present invention;

[0026] Figure 3 This is a schematic diagram of the structure of the surface acoustic wave sensor provided by the present invention;

[0027] Figure 4 This is a schematic diagram of the antenna structure provided by the present invention;

[0028] Figure 5 This is a block diagram illustrating the temperature compensation principle of the wireless multi-parameter integrated sensing device provided in Example 3.

[0029] In the figure: 100, flexible surface acoustic wave sensor; 1, high temperature resistant flexible substrate; 101, cavity; 2, piezoelectric film; 3, antenna structure; 4, temperature sensing unit; 5, pressure sensing unit. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] It should be noted that in the description of this invention, the terms "upper," "lower," "left," "right," "inner," "outer," "front," "rear," "center," "longitudinal," "transverse," "length," "width," "thickness," "vertical," "horizontal," "top," "bottom," "clockwise," and "counterclockwise," etc., indicating directional or positional relationships, are based on the directional or positional relationships shown in the accompanying drawings. These are merely for ease of description and do not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0032] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0033] The purpose of this invention is to provide a method for preparing a flexible surface acoustic wave sensor and a flexible surface acoustic wave sensor, so as to solve the problems existing in the prior art, meet the high temperature testing requirements of irregularly shaped components, and ensure the processing quality.

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] Example 1

[0036] like Figures 1-5 As shown, this embodiment provides a method for fabricating a flexible surface acoustic wave sensor 100, including the following steps:

[0037] S1. Preparation of a high-temperature resistant flexible substrate 1, the preparation method includes: obtaining a first substrate layer, a second substrate layer and a third substrate layer, the first substrate layer, the second substrate layer and the third substrate layer are all high-temperature resistant flexible substrates 1, a cavity 101 is opened in the second substrate layer along the thickness direction of the second substrate layer; the first substrate layer and the second substrate layer are respectively stacked on both sides of the second substrate layer and the cavity 101 is filled with a heat-volatile material, specifically: the second substrate layer can be placed on the first substrate layer first, then the heat-volatile material is filled, and then the third substrate layer is placed on the second substrate layer; the first substrate layer, the second substrate layer and the third substrate layer are laminated to obtain the high-temperature resistant flexible substrate 1; after lamination, the upper and lower ends of the cavity 101 are sealed by the first substrate layer and the third substrate layer, thereby forming a sealed cavity.

[0038] S2. Deposit a piezoelectric thin film 2 on the first surface of the high-temperature resistant flexible substrate 1;

[0039] S3. A surface acoustic wave sensor is fabricated on the piezoelectric thin film 2, and the high-temperature resistant flexible substrate 1 is heated to cause the thermally volatile material in the cavity 101 to evaporate.

[0040] In this embodiment, a high-temperature resistant flexible substrate 1 is prepared using lamination technology, thereby forming a flexible surface acoustic wave sensor 100. This sensor exhibits good ductility and can fit seamlessly with the component to be tested, especially meeting the high-temperature testing requirements of irregularly shaped components. Simultaneously, before laminating the first, second, and third substrate layers, a heat-volatile material is filled into the cavity 101. This material supports the first and third substrate layers during lamination, preventing them from sinking into the cavity 101 and ensuring processing quality.

[0041] In this specific embodiment, S3 further includes: coating a high-temperature resistant adhesive layer on the second surface of the high-temperature resistant flexible substrate 1, wherein the second surface is a surface on the high-temperature resistant flexible substrate 1 that is opposite to the first surface; after the flexible surface acoustic wave sensor 100 is bonded to the structure to be tested by the high-temperature resistant adhesive layer, the flexible surface acoustic wave sensor 100 is then heated to completely evaporate the heat-volatile material in the cavity 101. Heating not only allows the heat-volatile material to completely evaporate, forming an absolute pressure cavity for pressure detection by the flexible surface acoustic wave sensor 100, but also strengthens the adhesion of the high-temperature resistant adhesive layer, increasing the bonding strength between the flexible surface acoustic wave sensor 100 and the irregularly shaped structure surface.

[0042] In this specific embodiment, S3 further includes: before heating the thermally volatile material in the cavity 101, processing an antenna structure 3 on the portion of the first surface where the piezoelectric thin film 2 is not deposited. The surface acoustic wave sensor and the data processing module can wirelessly transmit data through the antenna structure 3, solving the problems of complex wiring, easy aging and short circuits of cables, and large losses due to excessive length in traditional cable transmission.

[0043] In this specific embodiment, S1 further includes: the outline dimension of the cavity 101 cut on the second substrate layer is larger than the designed outline dimension of the pressure cavity 101 of the flexible surface acoustic wave sensor 100 by a shrinkage rate, where the shrinkage rate is the shrinkage rate of the second substrate layer, to ensure that the pressure sensing unit 5 of the surface acoustic wave sensor can be located inside the pressure cavity 101 after the second substrate layer shrinks at high temperature. The designed outline dimension of the pressure cavity 101 is the final outline dimension of the pressure cavity 101 of the flexible surface acoustic wave sensor 100.

[0044] In this specific embodiment, S1 further includes: a lamination method for the first base layer, the second base layer, and the third base layer includes: placing the first base layer, the second base layer, and the third base layer, which are stacked and filled with a heat-volatile material, into a vacuum bag; first, evacuating the vacuum bag; then, laminating the first base layer, the second base layer, and the third base layer inside the vacuum bag to obtain a laminated integral structure; and cutting the laminated integral structure to obtain a high-temperature resistant flexible substrate 1.

[0045] In this specific embodiment, S1 further includes: the outline dimension of the high-temperature resistant flexible substrate 1 obtained by cutting the laminated integral structure is larger than the designed outline dimension of the flexible substrate of the flexible surface acoustic wave sensor 100 by a shrinkage rate, where the shrinkage rate is the shrinkage rate of the high-temperature resistant flexible substrate 1. The designed outline dimension of the flexible substrate of the flexible surface acoustic wave sensor 100 is the outline dimension value of the flexible substrate of the flexible surface acoustic wave sensor 100 after final processing.

[0046] In this specific embodiment, the first, second, and third substrate layers are all made of green ceramic tape, and the piezoelectric film 2 is an aluminum nitride (AlN) piezoelectric film. As a preferred embodiment, the green ceramic tape is an HTCC (High Temperature Co-fired Ceramic) green ceramic tape; more preferably, the green ceramic tape is of type ESL (44007-G) with a thickness of 130 μm. The thermally volatile material filler is a carbon film.

[0047] In this specific embodiment, the surface acoustic wave sensor includes a temperature sensing unit 4 and a pressure sensing unit 5, with the pressure sensing unit 5 disposed opposite to the cavity 101. When subjected to pressure, the piezoelectric film 2 at the corresponding position in the cavity 101 deforms, causing a change in the propagation speed of the surface acoustic wave passing through this portion of the piezoelectric film 2. The pressure sensing unit 5, disposed opposite to the cavity 101, enables accurate sensing of pressure parameters.

[0048] In this specific embodiment, S2 further includes: depositing a piezoelectric thin film 2 on the first surface of the high-temperature resistant flexible substrate 1 using pulsed laser deposition technology; S3 further includes: fabricating a surface acoustic wave sensor on the piezoelectric thin film 2 using nanoimprinting technology, and processing an antenna structure 3 on the first surface using screen printing technology.

[0049] Example 2

[0050] This embodiment provides a method for fabricating a flexible surface acoustic wave sensor 100, including the following steps:

[0051] I. Preparation of a high-temperature resistant flexible substrate 1, the preparation method includes:

[0052] ESL (44007-G) HTCC (High Temperature Co-fired Ceramic) green ceramic tape with a thickness of 130 μm was selected. The green ceramic tape was sliced, punched, stacked, and laminated to obtain a high-temperature resistant flexible substrate 1. Specifically:

[0053] Step 1: Slicing and Punching. HTCC green ceramic tape is in roll form. It is cut into 8×8-inch diaphragms, and then a punching machine is used to create positioning holes at the four corners of each diaphragm. The diameter of the positioning holes is 3.00 mm. The high-temperature resistant flexible substrate 1 consists of three substrate layers, i.e., three diaphragm layers are required. A cavity 101 with a shrinkage rate larger than the pressure cavity 101 of the actually processed flexible surface acoustic wave sensor 100 is cut from the second substrate layer. The shrinkage rate of HTCC green ceramic tape is 15.8%. Taking the cavity 101 as a cylindrical cavity as an example, the diameter of the cavity 101 processed on the diaphragm is 15.8% larger than the diameter of the pressure cavity 101 of the actually processed flexible surface acoustic wave sensor 100.

[0054] Step 2: Stacking and Lamination. Remove the PET film from the green ceramic belt. Stack the three layers of film according to the positioning holes. Fill the cavity 101 of the second base layer with carbon film, making the carbon film the same size as the cavity 101. Cover both sides of the stacked structure with the reverse side of the PET film and place it on a steel plate. Put it into a vacuum packaging bag and evacuate the vacuum packaging bag in a vacuum chamber. Then, place it in a water-cooled press for lamination. Specifically, preheat the press at 75°C for 10 minutes, then apply pressure at 21 MPa for 5 minutes to bond the three films together to form a block.

[0055] Step 3: Marking and Cutting. The bar block is marked with marking lines by increasing the size of the final required flexible surface acoustic wave sensor 100 by a shrinkage rate. The cutting machine parameters such as the blade depth are adjusted, and the bar block is cut along the marking lines to finally obtain the high-temperature resistant flexible substrate 1.

[0056] 2. An AlN piezoelectric thin film 2 oriented along the c-axis is deposited on the surface of the fabricated high-temperature resistant flexible substrate 1. Compared with other semiconductor materials, AlN thin films have good chemical stability and high melting point; they have high acoustic wave propagation speed and high-performance piezoelectric response, and can be used to fabricate high-performance surface acoustic wave devices; the c-axis oriented AlN piezoelectric thin film 2 has very good piezoelectricity and high-speed propagation performance of surface acoustic waves, with the highest sound transmission speed among inorganic non-ferrous piezoelectric materials.

[0057] AlN thin films were deposited on a high-temperature resistant flexible substrate using pulsed laser deposition (PLD). The PLD system consisted of a laser and a vacuum deposition chamber. The laser was a KrF excimer laser manufactured by Coherent Instruments, specifically a COMPex201F model, with a pulsed wavelength of 248 nm. The deposition system was a PLD-450B device provided by Shenyang Scientific Instruments. The system achieved a maximum ultimate vacuum of 6.67 × 10⁻⁶. -6 Pa is maintained by a mechanical pump and a high-vacuum molecular pump; the maximum temperature of the substrate heating furnace in the vacuum deposition chamber is 800℃; the substrate and target stage have an adjustment range of 30-90mm and can be externally controlled; the substrate tray can rotate continuously and is controlled by a motor-driven magnetic coupling mechanism.

[0058] The prepared high-temperature resistant flexible substrate 1 is transferred to the substrate tray inside the vacuum chamber 101 of the PLD and fixed to the substrate tray. The substrate tray rotation button is turned on, causing the substrate tray to rotate and drive the high-temperature resistant flexible substrate 1 to ensure good uniformity of the deposited film thickness. The energy of the laser is adjusted. Typically, lasers have two modes: constant voltage and constant energy. The constant voltage is set to 22KV and the frequency to 3Hz. The pressure inside the cavity is maintained by mechanical pumps and molecular pumps. The target and substrate tray rotation switch is turned on, and the high-energy laser bombards the target block to deposit a thin film on the surface of the high-temperature resistant flexible substrate 1.

[0059] III. Surface Acoustic Wave Sensor and Antenna Structure (Graphical)

[0060] Nanoimprint lithography was used to pattern surface acoustic wave (SAW) high-frequency devices. Screen printing was used to pattern the surface of antenna structure 3.

[0061] Nanoimprint lithography includes: template preparation, substrate cleaning, coating, nanoimprint lithography, etching, and other subsequent processes. The specific process flow is as follows:

[0062] ① Substrate cleaning: The high-temperature resistant flexible substrate 1 on which the piezoelectric thin film 2 is deposited is cleaned to remove surface impurities. The moisture is dried with nitrogen gas.

[0063] ② Template preparation: Surface acoustic wave (SAW) silicon templates were prepared using electron beam etching. The SAW silicon templates were cleaned, treated to prevent sticking, and then an intermediate polymer template (IPS) was imprinted.

[0064] The surface acoustic wave (SAW) silicon template is pre-baked at 140℃ for 90 seconds; the adhesive is homogenized; then post-baked at 140℃ for 120 seconds; the SAW silicon template is imprinted using a stepped pressure method; after imprinting, it is peeled off to obtain the required IPS soft template.

[0065] ③ The surface acoustic wave sensor is imprinted on the piezoelectric film 2 using an IPS soft template, and the surface residue is removed by RIE (reactive ion etching) to obtain the desired surface acoustic wave structure.

[0066] IV. Surface-mounted sticker-type structural forming of irregularly shaped components

[0067] A layer of high-temperature silicone sealant is coated on the bottom surface (second surface) of a high-temperature resistant flexible substrate 1 with a piezoelectric thin film 2, and then it is adhered to the surface of any irregularly shaped structure to be tested. The entire structure is sintered at temperature step by temperature using a laser high-temperature gun, removing organic matter from the silicone sealant and carbon film, and causing the carbon film to volatilize. The carbon film is drained before the ceramic particles in the green ceramic belt become dense, forming a complete sealed cavity 101 (absolute pressure cavity) inside the green ceramic belt, and the ceramic particles are tightly bonded together by an inorganic adhesive. At this point, the silicone sealant and the green ceramic belt are firmly adhered to the surface of the irregularly shaped structure, like a sticker.

[0068] This embodiment enables real-time wireless acquisition of multiple parameters of irregularly shaped components under harsh environments such as high temperature and high pressure, providing solutions and references for the manufacturing and application of highly flexible sensors.

[0069] Example 3

[0070] This embodiment provides a flexible surface acoustic wave (SAW) sensor 100, including a high-temperature resistant flexible substrate 1, a piezoelectric thin film 2, and a SAW sensor. The high-temperature resistant flexible substrate 1 includes a first substrate layer, a second substrate layer, and a third substrate layer arranged sequentially. A cavity 101 is formed in the second substrate layer, penetrating the second substrate layer along its thickness direction. The first substrate layer, the second substrate layer, and the third substrate layer are fixedly connected by lamination technology. The cavity 101 can be filled with a thermally volatile material, which provides support for the first substrate layer and the third substrate layer during lamination. The piezoelectric thin film 2 is disposed on the first surface of the high-temperature resistant flexible substrate 1. The SAW sensor is disposed on the piezoelectric thin film 2.

[0071] In this specific embodiment, an antenna structure 3 is fabricated on the portion of the first surface where the piezoelectric thin film 2 is not deposited, and the surface acoustic wave sensor is communicatively connected to the antenna module.

[0072] In this specific embodiment, the surface acoustic wave sensor includes a temperature sensing unit 4 and a pressure sensing unit 5. The pressure sensing unit 5 is disposed opposite to the cavity 101, forming a wireless multi-parameter integrated sensing device. Since temperature and other physical quantities can interfere with each other in complex environments, the temperature data detected by the temperature sensing unit 4 in this embodiment can also be used for temperature compensation.

[0073] Specifically, a multi-parameter decoupling algorithm and a temperature compensation algorithm based on multi-sensor data fusion technology can be used to solve the problem of mutual coupling between multiple parameters at high temperatures, thereby improving the accuracy of integrated multi-parameter measurement. Specifically, ambient temperature simultaneously affects the detection of both temperature sensing unit 4 and pressure sensing unit 5, and the temperature drift of the surface acoustic wave (SAW) sensor is greater than the change caused by vibration within its measurement range. Therefore, in practical applications involving combined temperature and high pressure environments, it is necessary to perform temperature compensation decoupling on the temperature and pressure sensing units to ensure accurate pressure signal acquisition under varying temperature conditions. Temperature calibration tests can be performed using a standard temperature sensor (preferably a standard thermocouple) placed in the same location as the multi-parameter integrated sensing device. Together with the multi-parameter surface acoustic wave (SAW) integrated sensing device, they form a multi-sensor measurement system. The standard temperature sensor outputs a voltage signal, while the multi-parameter integrated sensing device outputs a frequency signal, and both are acquired in real time. By performing data fusion processing on the two types of input data (data from the standard temperature sensor and data from the multi-parameter SAW integrated sensing device), temperature compensation and temperature calibration of the SAW multi-parameter integrated sensing device can be achieved.

[0074] The multi-parameter decoupling algorithm proposes to use data fusion technology to solve the temperature cross-coupling problem in the multi-parameter integrated surface acoustic wave (SAW) sensor, thereby improving the sensor's temperature stability. The block diagram of the temperature compensation principle of the SAW temperature-pressure dual-parameter integrated sensor based on data fusion technology is shown below. Figure 5 As shown.

[0075] Establish the equation:

[0076]

[0077] Where, Δf P =f P -f 0P , Δf T =f T -f 0T After obtaining the coefficient matrix K through least squares calibration, the solution is:

[0078]

[0079] Where, Δf T Frequency shift caused by pure temperature; f 0T f is the initial frequency at temperature. T The output frequency is the temperature; Δf P Frequency shift caused by pure pressure; f 0P f is the initial frequency of the pressure. P This refers to the pressure output frequency.

[0080] The multi-parameter decoupling algorithm and temperature compensation algorithm based on multi-sensor data fusion technology in this embodiment are existing technologies. For example, the parameter compensation decoupling method in the patent application No. 202310206291.9, which describes a device and method for real-time in-situ simultaneous measurement of temperature and mechanical parameters, can be used. This method can establish the state equation and observation equation of the temperature system, describing the temperature change law and the relationship between temperature and other observable parameters. The initial state estimate, covariance matrix, and other parameters of the Kalman filter algorithm are determined. Temperature is predicted based on the state equation, and then the prediction result is updated based on new observation data to obtain a more accurate temperature estimate. Related parameters are compensated based on temperature changes. Kalman filtering, Bayesian algorithms, and other algorithms are used to effectively remove noise from the data, improve data accuracy, and perform comprehensive analysis and processing to correct measurement deviations. Further details are omitted here.

[0081] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for fabricating a flexible surface acoustic wave sensor, characterized in that: Includes the following steps: S1. A high-temperature resistant flexible substrate is prepared by means of: obtaining a first substrate layer, a second substrate layer, and a third substrate layer, wherein the first substrate layer, the second substrate layer, and the third substrate layer are all high-temperature resistant flexible substrates; forming a cavity in the second substrate layer that penetrates the second substrate layer along the thickness direction of the second substrate layer; stacking the first substrate layer and the second substrate layer on both sides of the second substrate layer respectively and filling the cavity with a heat-volatile material; laminating the first substrate layer, the second substrate layer, and the third substrate layer to obtain the high-temperature resistant flexible substrate; S2. Deposit a piezoelectric thin film on the first surface of the high-temperature resistant flexible substrate; S3. A surface acoustic wave sensor is fabricated on the piezoelectric film, and the high-temperature resistant flexible substrate is heated to cause the thermally volatile material in the cavity to volatilize.

2. The method for fabricating a flexible surface acoustic wave sensor according to claim 1, characterized in that: S3 further includes: coating a high-temperature resistant adhesive layer on the second surface of the high-temperature resistant flexible substrate, wherein the second surface is a surface on the high-temperature resistant flexible substrate that is opposite to the first surface; after the flexible surface acoustic wave sensor is bonded to the structure to be tested by the high-temperature resistant adhesive layer, the flexible surface acoustic wave sensor is heated to completely evaporate the thermally volatile material in the cavity.

3. The method for fabricating a flexible surface acoustic wave sensor according to claim 1, characterized in that: S3 further includes: fabricating an antenna structure on the portion of the first surface where the piezoelectric thin film is not deposited.

4. The method for fabricating a flexible surface acoustic wave sensor according to claim 2, characterized in that: S1 further includes: the profile dimension of the cavity cut on the second substrate layer is larger than the design value of the profile dimension of the pressure cavity of the flexible surface acoustic wave sensor by a shrinkage rate, wherein the shrinkage rate is the shrinkage rate of the second substrate layer.

5. The method for fabricating a flexible surface acoustic wave sensor according to claim 2, characterized in that: S1 further includes: a lamination method for the first base layer, the second base layer, and the third base layer comprising: placing the first base layer, the second base layer, and the third base layer, after being stacked and filled with the heat-volatile material, into a vacuum bag; first evacuating the vacuum bag; then laminating the first base layer, the second base layer, and the third base layer within the vacuum bag to obtain a laminated integral structure; and cutting the laminated integral structure to obtain the high-temperature resistant flexible substrate.

6. The method for fabricating a flexible surface acoustic wave sensor according to claim 5, characterized in that: S1 further includes: the outline dimension of the high-temperature resistant flexible substrate obtained by cutting the laminated integral structure is larger than the design value of the outline dimension of the flexible substrate of the flexible surface acoustic wave sensor by a shrinkage rate, wherein the shrinkage rate is the shrinkage rate of the high-temperature resistant flexible substrate.

7. The method for fabricating a flexible surface acoustic wave sensor according to claim 1, characterized in that: The first substrate layer, the second substrate layer, and the third substrate layer are all made of green ceramic tape, and the piezoelectric film is an aluminum nitride piezoelectric film.

8. The method for fabricating a flexible surface acoustic wave sensor according to claim 1, characterized in that: The surface acoustic wave sensor includes a temperature sensing unit and a pressure sensing unit, with the pressure sensing unit positioned opposite to the cavity.

9. The method for fabricating a flexible surface acoustic wave sensor according to claim 3, characterized in that: S2 further includes: depositing the piezoelectric thin film on the first surface of the high-temperature resistant flexible substrate using pulsed laser deposition technology; S3 further includes: fabricating the surface acoustic wave sensor on the piezoelectric thin film using nanoimprinting technology, and processing the antenna structure on the first surface using screen printing technology.

10. A flexible surface acoustic wave sensor, characterized in that: The device includes a high-temperature resistant flexible substrate, a piezoelectric thin film, and a surface acoustic wave (SAW) sensor. The high-temperature resistant flexible substrate comprises a first substrate layer, a second substrate layer, and a third substrate layer arranged sequentially. All three substrate layers are high-temperature resistant flexible substrates. A cavity penetrating the second substrate layer along its thickness direction is formed in the second substrate layer. The first, second, and third substrate layers are fixedly connected by lamination technology. The cavity can be filled with a thermally volatile material, which provides support for the first, second, and third substrate layers during lamination. The piezoelectric thin film is disposed on the first surface of the high-temperature resistant flexible substrate. The SAW sensor is disposed on the piezoelectric thin film.

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