A fluid wall shear-compression stress composite array sensor chip

Abstract

This invention discloses a fluid wall shear and compressive stress composite array sensor chip, belonging to the field of MEMS sensor technology. It includes several shear stress sensors and compressive stress sensors integrated on the chip. The shear stress sensors are arranged in a cross-shaped array, while the compressive stress sensors are arranged in a zigzag shape. These two arrays are concentrically superimposed to obtain a grid array layout. A pressure sensor is positioned at the center of the grid array. Several shear stress sensors are arranged radiating outwards along the cross-shaped direction with the central pressure sensor as the radiation center, used to measure two-dimensional shear stress. Several compressive stress sensors are arranged radiating outwards along the zigzag direction with the central pressure sensor as the radiation center, used to measure gradient pressure. This invention solves the problem that single-point measurements are insufficient to fully reflect the actual flow field stress distribution in complex fluid environments.

Description

Technical Field

[0001] This invention belongs to the field of MEMS sensor technology, specifically relating to a fluid wall shear-compression stress composite array sensor chip. Background Technology

[0002] Wall shear stress and wall compressive stress have long been two important physical quantities of interest in fluid dynamics research. Wall shear stress is influenced by fluid viscosity and the velocity gradient within the boundary layer, while pressure pulsations are caused by velocity field disturbances within the boundary layer. Simultaneous measurement of wall shear stress and compressive stress can effectively capture the pulsation characteristics of the boundary layer evolution process and provide insights into boundary layer flow noise, offering crucial data support for drag reduction, stealth, and noise reduction optimization design of aircraft / vehicles. However, due to the small magnitude, high dynamics, and small flow characteristic dimensions of wall shear stress and compressive stress, traditional measurement methods are limited by low sensitivity, large size, and inability to withstand high temperatures. Furthermore, a single device is insufficient to accurately measure both physical quantities simultaneously.

[0003] Optical testing technology offers significant advantages in shear stress and pressure measurement, primarily due to its non-contact measurement, high resolution, and interference resistance. First, optical testing eliminates the need for direct contact with the measured physical surface, avoiding mechanical interference and surface damage that can occur with traditional sensors, making it particularly suitable for extreme environments such as high temperatures and high-speed flows. Second, optical testing technology boasts high spatial and temporal resolution, enabling precise capture of minute stress changes and transient phenomena, meeting the high-precision measurement requirements of dynamic processes. Furthermore, optical systems are insensitive to electromagnetic interference, significantly improving the robustness of the measurement process and the reliability of the data, demonstrating irreplaceable advantages in applications requiring high precision, long-term monitoring, and complex environments.

[0004] Currently, in related technologies, individual compressive stress sensors or two-dimensional shear stress sensors are used for testing. These individual compressive stress sensors or two-dimensional shear stress sensors are usually arranged arbitrarily in an array. Since it is an array of single sensors, firstly, installation errors will occur, and secondly, single-point measurements cannot fully reflect the actual flow field stress distribution. Therefore, in complex fluid environments, individual arrays of compressive stress sensors or two-dimensional shear stress sensors cannot obtain accurate measurement results. Summary of the Invention

[0005] The technical problem to be solved:

[0006] To overcome the shortcomings of existing technologies, this invention provides a fluid wall shear-compression stress composite array sensor chip. It combines a two-dimensional shear stress sensor and a compressive stress sensor on the fluid wall into an array, resulting in an integrated shear-compression stress sensor array structure capable of measuring gradient pressure. By employing a grid array layout for the structurally similar two-dimensional shear stress sensor and compressive stress sensor, it not only reduces the size and weight of the sensor but also minimizes assembly errors. Multiple sensors can simultaneously acquire data at different locations, enabling data mutual correction and high spatial resolution measurement. This invention solves the problem that single-point measurements in complex fluid environments cannot fully reflect the actual flow field stress distribution, improving measurement accuracy. It also provides a precise testing method for stress changes in fields such as fluid mechanics, meeting the needs of multi-point stress measurement in complex fluid environments.

[0007] The technical solution of this invention is: a fluid wall shear and compressive stress composite array sensor chip, comprising several shear stress sensors and compressive stress sensors integrated on the chip. The overall arrangement of the shear stress sensors is in a cross shape, and the overall arrangement of the compressive stress sensors is in an X shape. The two arrays are concentrically superimposed to obtain a grid array layout. The center position of the grid array is a pressure sensor. Several shear stress sensors are arranged radially outward along the cross direction with the central pressure sensor as the radiation center to measure two-dimensional shear stress. Several compressive stress sensors are arranged radially outward along the X direction with the central pressure sensor as the radiation center to measure gradient pressure.

[0008] A further technical solution of the present invention is that the shear stress sensor and the compressive stress sensor are integrated and synchronously processed on a chip using MEMS processing technology.

[0009] A further technical solution of the present invention is: both the shear stress sensor and the compressive stress sensor include a support layer, a cavity and a structural layer, the upper surface of the support layer and the lower surface of the structural layer are provided with a reflective film, and the surface of the cavity is provided with an anti-reflective coating.

[0010] A further technical solution of the present invention is: the support layer of the compressive stress sensor has multiple through holes for positioning and fixing of the optical fiber, and its inner reflective film is a metal reflective film.

[0011] A further technical solution of the present invention is: the structural layer of the shear stress sensor is a floating structure, and its inner reflective film is a grating film; the floating structure includes an elastic beam, a floating element, and a fixed anchor point, and the floating element is connected to the fixed anchor point through the circumferentially arranged elastic beam, which can drive the grating film installed on the lower surface of the floating element to generate displacement.

[0012] A further technical solution of the present invention is: the reflective film consists of a silicon nitride film, a chromium film layer and a gold film layer from bottom to top, and a multilayer dielectric film with alternating low and high refractive indices is deposited on the surface of the gold film layer, in the order of low refractive dielectric layer / high refractive dielectric layer / low refractive dielectric layer / high refractive dielectric layer, with each layer having a thickness of λ / 4.

[0013] A further technical solution of the present invention is: the low refractive medium layer of the dielectric multilayer film is Al2O3, and the high refractive medium layer is ZrO2, in the order of 120nmAl2O3 / 100nmZrO2 / 120nmAl2O3 / 100nmZrO2.

[0014] A gradient pressure measurement method for a fluid wall shear-compression composite array sensor chip, the specific steps of which are as follows:

[0015] Multiple compressive stress sensors are arranged in an X-shape on the chip, and the spacing between adjacent compressive stress sensors in a single radial arrangement direction is equal.

[0016] Experiments revealed that the measured values ​​of each level of compressive stress sensor, from the central compressive stress sensor outwards, exhibit a linear gradient variation.

[0017] Based on the gradient descent variation pattern, outliers and systematic errors are identified, and the measurement points that generate error values ​​are determined.

[0018] After identifying and confirming the errors, the pressure data at each measurement point are corrected using interpolation or weighted average methods to obtain accurate measurement values.

[0019] A further technical solution of the present invention is: the method for identifying outliers and systematic errors is as follows:

[0020] The identification of outliers involves comparing the measurement difference between adjacent compressive stress sensors located in the same radiation direction with a threshold obtained based on the linear gradient descent law. If the difference exceeds the threshold, it is judged as an outlier. For compressive stress sensors located in the same circumferential gradient level, the measured values ​​should be consistent. If there are differences, that point is judged as an outlier.

[0021] The identification of systematic errors involves comparing the identified outliers with normal values, filtering the deviation range to distinguish between true errors and transient anomalies caused by noise or environmental interference, and identifying the measurement points of true errors as systematic errors.

[0022] A further technical solution of the present invention is: the method for correcting the pressure data of each measurement point is to perform interpolation between the measurement point identified as an anomaly and the adjacent normal value measurement points on both sides, and determine the true pressure value of the anomaly through multi-point interpolation; and correct each anomaly using this method to obtain an effective test of the pulsating characteristics of the turbulent boundary layer formation and separation process.

[0023] Beneficial effects

[0024] The beneficial effects of this invention are as follows: Firstly, the fluid wall shear and compressive stress composite array sensor chip of this invention utilizes MEMS technology to integrate a two-dimensional fluid wall shear stress sensor and a compressive stress sensor onto a single millimeter-scale chip using an integrated synchronous manufacturing process, simplifying the manufacturing process. Secondly, the grid-array layout not only reduces the size and weight of the sensors but also lowers assembly errors; multiple sensors can also simultaneously acquire data at different locations, enabling data mutual correction and high spatial resolution measurement. This not only improves measurement accuracy but also provides a precise testing method for stress changes in fields such as fluid mechanics, meeting the needs of multi-point stress measurement in complex fluid environments. Specific advantages are analyzed below:

[0025] 1. The grid array design can acquire pressure data from multiple spatial points and calculate the pressure gradient through differential calculation. The shear stress sensor at the center line position can measure two-dimensional shear stress in the orthogonal direction, thereby comprehensively acquiring the stress distribution in the fluid.

[0026] 2. The chip has no internal circuitry, making it suitable not only for extreme high-temperature environments but also for measuring underwater fluid stress. This is applicable to the study of complex flow phenomena, effectively testing the pulsating characteristics of turbulent boundary layer formation and separation processes, and laying the foundation for effectively evaluating the frictional drag and flow noise of aircraft / vehicle aerodynamic structures.

[0027] 3. Pressure gradient measurement directly reflects pressure changes in fluids at different spatial locations, providing fundamental data for analyzing flow characteristics. In complex flow fields, pressure gradients often influence fluid direction, velocity distribution, and boundary layer characteristics, playing a crucial role in the study of turbulence and separation phenomena. Therefore, measuring pressure gradients allows for a more accurate understanding of fluid dynamics, which is particularly important for fields like aerospace where aerodynamic characteristics and flow control are critical. This invention utilizes a multi-point layout of a grid array sensor for pressure gradient measurement, achieving high spatial resolution monitoring and enabling the system to acquire detailed pressure change information. Furthermore, the grid array layout allows for data cross-correction, effectively reducing single-point measurement errors through multi-point sampling and differential calculation, thus improving measurement accuracy and data reliability. This method not only enhances the comprehensiveness of the measurement but also reduces the impact of external interference on the measurement results through self-calibration, making it particularly suitable for precise monitoring in complex environments. Attached Figure Description

[0028] Figure 1 This is a top view of a fluid wall shear-compression stress composite array sensor chip according to an embodiment of the present invention;

[0029] Figure 2 This is a top view of the floating structure layer of the shear stress sensor in an embodiment of the present invention;

[0030] Figure 3 This is a top view of the support layer for the floating shear stress sensor in an embodiment of the present invention;

[0031] Figure 4 This is a bottom view of the compressive stress sensor structure layer in an embodiment of the present invention;

[0032] Figure 5 This is a top view of the compressive stress sensor support layer in an embodiment of the present invention;

[0033] Figure 6 This is a cross-sectional view (AA) of a fluid wall shear-compression stress composite array sensor chip according to an embodiment of the present invention;

[0034] Figure 7 This is a schematic diagram of a 4×4 grid array structure in an embodiment of the present invention.

[0035] Explanation of reference numerals in the attached figures: 1. Compressive stress sensor; 2. Shear stress sensor; 3. Elastic beam; 4. Floating element; 5. Cavity; 6. Grating film; 7. Fixed anchor point; 8. Metal reflective film; 9. Through hole; 10. Floating structure; 11. Structural layer; 12. Support layer. Detailed Implementation

[0036] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0037] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to 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.

[0038] Based on the existing technology that uses separate compressive stress sensors or two-dimensional shear stress sensors for testing, installation errors can occur, and it is difficult to fully reflect the actual flow field stress distribution, resulting in inaccurate measurement results. Therefore, this invention provides a fluid wall shear-compressive stress composite array sensor chip, including several shear stress sensors and compressive stress sensors integrated on the chip. The overall array of the shear stress sensors is arranged in a cross shape, and the overall array of the compressive stress sensors is arranged in an X shape. The two arrays are concentrically superimposed to obtain a grid array layout. The center position of the grid array is a pressure sensor. Several shear stress sensors are arranged radiating outwards along the cross direction with the central pressure sensor as the radiation center to measure two-dimensional shear stress. Several compressive stress sensors are arranged radiating outwards along the X direction with the central pressure sensor as the radiation center to measure gradient pressure.

[0039] Specifically, the chip is a composite of an optical compressive stress sensor and a shear stress sensor. The two sensors have similar structures, each including a support layer, a cavity, and a structural layer from bottom to top. The structures can be integrated and synchronously fabricated using MEMS technology. A reflective film is provided on the upper surface of the support layer to reduce crosstalk from external light sources. An anti-reflective coating is provided on the surface of the cavity to enhance the contrast of the reflective film, and the area of ​​the anti-reflective coating is larger than that of the reflective film. A reflective film is provided on the lower surface of the structural layer for receiving and reflecting optical signals.

[0040] Specifically, the reflective film of the compressive stress sensor is a metal reflective film, and the reflective film of the shear stress sensor is a grating film structure. Both the metal reflective film and the grating film structure can be simultaneously processed using MEMS patterned sputtering metal thin film technology. Using a high-reflectivity metal thin film as a grating can improve the sensor's sensitivity. However, at a high temperature of 350℃, the electrostatic repulsion between gold molecules in the gold grating film weakens, while the interaction forces, such as van der Waals forces, strengthen, thus promoting molecular attraction and forming clusters and agglomerates, affecting the intensity of reflected light. To suppress the gold agglomeration effect and further improve the reflection efficiency of the grating film at high temperatures, a dielectric layer film is deposited on the gold grating. Based on the theory of the metal-dielectric reflective film model, a dielectric multilayer film with alternating high and low refractive indices and a thickness of λ / 4 is deposited on the metal thin film to improve the reflectivity and high-temperature resistance of the gold grating film. In practical applications, low-refractive-index aluminum oxide (Al2O3) and high-refractive-index (ZrO2) can be used together. This sensor has 120nm Al2O3 / 100nm ZrO2 / 120nm Al2O3 / 100nm ZrO2 deposited on the gold grating film to ensure that the gold grating film does not agglomerate at temperatures above 400℃ and still has high reflectivity.

[0041] Specifically, the pressure sensor has several through holes in the support layer for positioning and fixing the optical fiber. The structural layer of the shear stress sensor has a floating structure, and the floating structure is located above the cavity.

[0042] This invention discloses a gradient pressure measurement method for a fluid wall shear-compression composite array sensor chip, the specific steps of which are as follows:

[0043] Step 1: Arrange multiple compressive stress sensors in an X-shape on the chip, with the spacing between adjacent compressive stress sensors in a single radial arrangement direction being equal;

[0044] Step 2: Through experiments, it was found that the measured values ​​of each level of compressive stress sensor from the central compressive stress sensor outwards exhibit a linear gradient variation.

[0045] Step 3: Identify outliers and systematic errors based on the gradient descent variation pattern, and determine the measurement points that generate error values;

[0046] Specifically, for the identification of outliers, for compressive stress sensors located in the same radiation direction, the measurement difference between adjacent compressive stress sensors is compared with a threshold obtained based on the linear gradient descent law. If the difference exceeds the threshold, it is judged as an outlier. For compressive stress sensors located in the same circumferential gradient level, the measured values ​​should be consistent. If there are differences, the point is judged as an outlier.

[0047] The identification of systematic errors involves comparing the identified outliers with normal values, filtering the deviation range to distinguish between true errors and transient anomalies caused by noise or environmental interference, and identifying the measurement points of true errors as systematic errors.

[0048] Step 4: After identifying and confirming the error, correct the pressure data of each measurement point by interpolation or weighted average method to obtain accurate measurement values.

[0049] Specifically, the method for correcting the pressure data at each measurement point is to perform interpolation between the measurement point identified as an anomaly and the adjacent normal measurement points on both sides, and determine the true pressure value of the anomaly through multi-point interpolation; and correct each anomaly using this method to obtain an effective test of the pulsating characteristics of the turbulent boundary layer formation and separation process.

[0050] The above technical solution will be further explained below with reference to examples and accompanying drawings:

[0051] Reference Figure 1 As shown, this embodiment discloses a fluid wall shear-compression composite array sensor chip, comprising multiple compressive stress sensors 1 and shear stress sensors 2. These sensors are arranged in a 3×3 grid array on the same millimeter-scale chip. The compressive stress sensors 1 are positioned diagonally across the grid array, with each sensor unit capable of independently measuring the pressure at its location. By precisely controlling the position and spacing of each sensor unit in the array, pressure data from multiple spatial points can be acquired. Differential calculations of these data yield the pressure changes of the fluid at different locations, thus enabling the measurement of pressure gradients. The shear stress sensors 2 are positioned along the two center lines in the X and Y directions of the array structure. These shear stress sensors should be arranged vertically in the grid array structure according to their sensitive directions to achieve two-dimensional shear stress measurement.

[0052] Reference Figure 6 As shown, the pressure sensor 1 and the shear stress sensor 2 each include a support layer 12, a cavity 5, and a structural layer 11 from bottom to top. The support layer 12 and the structural layer 11 are connected by anodic bonding. A reflective film is provided on the lower surface of the structural layer 11 for receiving and reflecting light signals. The reflective film of the pressure stress sensor 1 is a metal reflective film 8, and the reflective film of the shear stress sensor 2 is a grating film 6. The metal reflective film 8 and the grating film 6 can be patterned by photolithography using the same photomask and sputtered with a metal film.

[0053] In this embodiment, the structural layer 11 of the shear stress sensor 2 is made of 40-50µm silicon, as shown in the reference. Figure 2As shown, the shear stress sensor 2 has a floating structure 10 on the structural layer 11, located above the cavity 5. The floating structure 10 consists of several elastic beams 3, a floating element 4, and several fixed anchor points 7. The floating element 4 is movably mounted on the fixed anchor points 7 via the elastic beams 3. The thickness of the floating element 4 is 20-30 μm, and the lower surface of the floating element has a grating film 6 with a thickness of 320-420 nm. The grating film 6 is composed of a 100-120 nm silicon nitride film, a 20-50 nm chromium film layer, and a 200-250 nm gold film layer. The lower surface of the structural layer 11 has a cavity 5 with a depth of 20-30 μm, and the area of ​​the cavity 5 is larger than that of the floating element 4. The area of ​​the floating element 4 is larger than that of the grating film 6.

[0054] In this embodiment, the structural layer 11 of the compressive stress sensor 1 is made of 40-50 μm silicon, and a cavity 5 is provided on the lower surface of the structural layer 11. The depth of the cavity 5 is 20-30 μm. (Refer to...) Figure 4 As shown, the lower surface of the structural layer 11 is further provided with a 320-420 nm thick metal reflective film 8. The metal reflective film 8 is composed of a 100-120 nm silicon nitride film, a 20-50 nm chromium film layer, and a 200-250 nm gold film layer, and the area of ​​the cavity 5 is larger than that of the metal reflective film 8. (Refer to...) Figure 5 As shown, the support layer 12 of the pressure sensor 1 has several through holes 9 for positioning and fixing the optical fiber.

[0055] In this embodiment, refer to Figure 3 and Figure 5 As shown, the support layer 12 of the compressive stress sensor 1 and the shear stress sensor 2 can be made of Borofloat 33 with a thickness of 300-500 μm. Its surface has a grating film 6 and a metal reflective film 8 with a thickness of 220-300 nm. Both the grating film 6 and the metal reflective film 8 are composed of a 100-120 nm silicon nitride film, a 20-50 nm chromium film layer, and a 200-250 nm gold film layer (or composed of a 20-50 nm chromium film layer and a 200-250 nm gold film layer). The area of ​​the cavity 5 is larger than the area of ​​the grating film 6, and the area of ​​the cavity 5 is larger than the area of ​​the metal reflective film 8. The support layer 12 also has several through holes 9 with a diameter of 800 μm-1000 μm, such as... Figure 3 and Figure 5 As shown.

[0056] In this embodiment, the structural layer 11 and the support layer 12 are connected by anodic bonding. The thickness of the wafer is 340-550 μm. Figure 6 The image shown is an AA cross-sectional view of the fluid wall shear-compression stress composite array sensor chip.

[0057] The aforementioned fluid wall shear and compressive stress composite array sensor chip achieves several advantages. Firstly, by employing MEMS technology, a two-dimensional shear stress sensor and a compressive stress sensor are integrated onto a single millimeter-scale chip using a unified, synchronous manufacturing process, simplifying the manufacturing process. Secondly, the grid-array layout not only reduces the sensor's size and weight but also allows multiple sensors to simultaneously acquire data at different locations, enabling data cross-correction and high spatial resolution measurements. The grid-array design also allows for the acquisition of pressure data from multiple spatial points, and the differential calculation of pressure gradients. The shear stress sensor at the centerline can measure two-dimensional shear stress in orthogonal directions, thus comprehensively acquiring the stress distribution in the fluid. Furthermore, the chip contains no internal circuitry, making it suitable for measuring stress in high-temperature environments and underwater fluids. This is applicable to the study of complex flow phenomena, laying the foundation for effectively evaluating the frictional drag and flow noise of aircraft / vehicle aerodynamic structures.

[0058] In this embodiment, the pressure sensors on the diagonal of the "nine-square grid" array structure achieve self-calibration through the following three steps, as detailed below:

[0059] Step 1: Error Identification: First, the pressure sensors on the diagonal compare their data with that of sensors at adjacent locations. When the difference between a sensor's measurement and that of its neighboring sensors is too large and exceeds a preset threshold, it is determined that an error may exist. This error may originate from system drift or random factors. The error identification process aims to accurately detect these outliers for subsequent correction.

[0060] Step 2: Data Comparison: Next, the diagonal sensor will repeatedly compare data from adjacent sensors to further filter detected deviations. This step effectively distinguishes between true errors and transient anomalies caused by noise or environmental interference. By comparing normal and abnormal values ​​from adjacent sensors, the source and magnitude of the error can be more accurately identified, providing fundamental data for the calibration process.

[0061] Step 3: Error Calibration: After identifying and confirming the error, the system uses multi-point measurements from the array to correct the error value through multi-point interpolation or weighted averaging. Sensors affected by the error will correct their own data based on the average or interpolation results of adjacent sensors to more closely approximate the actual pressure value. This process ensures the accuracy of the sensor data and improves the measurement consistency of the entire array.

[0062] Through self-calibration, the system can accurately identify and correct measurement errors. By comparing data from adjacent sensors, the system can detect and correct outliers, effectively reducing noise interference and avoiding errors caused by environmental factors, sensor drift, or external interference. This process significantly improves measurement accuracy, ensuring data reliability and consistency, especially under dynamic or extreme high-temperature conditions. Self-calibration also enhances the system's robustness, enabling it to adapt to complex environmental conditions, including high temperatures and underwater environments, ensuring long-term stable operation. Furthermore, the nine-grid array structure improves the system's spatial resolution through data fusion from multiple sensor points. Sensors at different locations can simultaneously acquire data, covering more measurement points. This not only enhances the comprehensive perception of pressure distribution but also allows the system to accurately capture minute pressure changes, further improving its responsiveness to fluid pressure gradients. By calculating pressure gradients differentially, the system can provide more detailed and accurate fluid characteristic analysis. This high-precision data support provides a solid foundation for the analysis of complex flow phenomena, especially significant for the study of turbulence, boundary layers, and flow separation.

[0063] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A fluid wall shear-compression stress composite array sensor chip, characterized in that: The system includes several shear stress sensors and compressive stress sensors integrated on a chip. The overall array of shear stress sensors is arranged in a cross shape, and the overall array of compressive stress sensors is arranged in an X shape. The two arrays are concentrically superimposed to obtain a grid array layout. The center position of the grid array is a pressure sensor. Several shear stress sensors are arranged radially outward along the cross direction with the central pressure sensor as the radiation center to measure two-dimensional shear stress. Several compressive stress sensors are arranged radially outward along the X direction with the central pressure sensor as the radiation center to measure gradient pressure.

2. The fluid wall shear-compression stress composite array sensor chip according to claim 1, characterized in that: The shear stress sensor and compressive stress sensor are integrated and synchronously fabricated on a chip using MEMS processing technology.

3. The fluid wall shear-compression stress composite array sensor chip according to claim 2, characterized in that: Both the shear stress sensor and the compressive stress sensor include a support layer, a cavity, and a structural layer. The upper surface of the support layer and the lower surface of the structural layer are provided with a reflective film, and the surface of the cavity is provided with an anti-reflective coating.

4. The fluid wall shear-compression stress composite array sensor chip according to claim 3, characterized in that: The support layer of the compressive stress sensor has multiple through holes for positioning and fixing the optical fiber, and its inner reflective film is a metal reflective film.

5. The fluid wall shear-compression stress composite array sensor chip according to claim 4, characterized in that: The shear stress sensor has a floating structure with an inner reflective film that is a grating film. The floating structure includes an elastic beam, a floating element, and a fixed anchor point. The floating element is connected to the fixed anchor point through the circumferentially arranged elastic beam, which can drive the grating film installed on the lower surface of the floating element to move.

6. The fluid wall shear-compression stress composite array sensor chip according to claim 5, characterized in that: The reflective film consists of a silicon nitride film, a chromium film layer, and a gold film layer from bottom to top. A multilayer dielectric film with alternating low and high refractive indices is deposited on the surface of the gold film layer in the following order: low refractive medium layer / high refractive medium layer / low refractive medium layer / high refractive medium layer, with each layer having a thickness of λ / 4.

7. The fluid wall shear-compression stress composite array sensor chip according to claim 6, characterized in that: The low-refractive-index dielectric layer of the dielectric multilayer film is Al2O3, and the high-refractive-index dielectric layer is ZrO2, with the following order: 120nm Al2O3 / 100nm ZrO2 / 120nm Al2O3 / 100nm ZrO2.

8. A method for measuring gradient pressure using a fluid wall shear-compression stress composite array sensor chip according to any one of claims 1-7, characterized in that... The specific steps are as follows: Multiple compressive stress sensors are arranged in an X-shape on the chip, and the spacing between adjacent compressive stress sensors in a single radial arrangement direction is equal. Experiments revealed that the measured values ​​of each level of compressive stress sensor, from the central compressive stress sensor outwards, exhibit a linear gradient variation. Based on the gradient change pattern, outliers and systematic errors are identified, and the measurement points that generate error values ​​are determined. After identifying and confirming the errors, the pressure data at each measurement point are corrected using interpolation or weighted average methods to obtain accurate measurement values.

9. The gradient pressure measurement method according to claim 8, characterized in that: The method for identifying outliers and systematic errors is as follows: The identification of outliers involves comparing the measurement difference between adjacent compressive stress sensors located in the same radiation direction with a threshold obtained based on the linear gradient change law. If the difference exceeds the threshold, it is judged as an outlier. For compressive stress sensors located in the same circumferential gradient level, the measured values ​​should be consistent. If there are differences, that point is judged as an outlier. The identification of systematic errors involves comparing the identified outliers with normal values, filtering the deviation range to distinguish between true errors and transient anomalies caused by noise or environmental interference, and identifying the measurement points of true errors as systematic errors.

10. The gradient pressure measurement method according to claim 8, characterized in that: The method for correcting the pressure data at each measurement point is to interpolate between the measurement point identified as an anomaly and the adjacent normal measurement points on both sides, and determine the true pressure value of the anomaly through multi-point interpolation; and correct each anomaly using this method to obtain an effective test of the pulsating characteristics of the turbulent boundary layer formation and separation process.

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