Flexible pressure sensor array for unmanned aerial vehicle airspeed measurement and method of making the same

Abstract

The application provides a flexible pressure sensor array for unmanned aerial vehicle airspeed measurement and a preparation method thereof. The sensor array comprises a net structure and a plurality of flexible pressure sensors arranged at nodes of the net structure. The sensor adopts a sandwich structure, the middle is a sensitive layer, the upper and lower are symmetrical flexible substrate layers and electrode layers, the sensitive layer is a composite conductive foam with a conductive elastomer filling skeleton, the composite conductive foam is obtained by immersing a foam in a conductive material solution for multiple times, and the sensitive layer skeleton is obtained by laser arraying through holes in the composite conductive foam and filling the through holes with a conductive elastomer. The sensor array uses a heterogeneous network porous foam with good conductivity and multilayer pressure response characteristics as the sensitive layer, has a wide pressure response range, the conductive elastomer skeleton improves the problem that the foam structure is easy to collapse under pressure deformation, prolongs the service life, and the use of the internet design reduces the Young's modulus of the overall structure and enables the sensor array to closely adhere to the curved surface of the wing leading edge.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible pressure sensors, and in particular relates to a flexible pressure sensor array for measuring the airspeed of an unmanned aerial vehicle (UAV) and a method for preparing the flexible pressure sensor array. Background Art

[0002] Pitot tubes are well-established instruments used for measurement in aerospace processes, directly and accurately measuring air velocity without the need for complex conversion or multiple probes. However, traditional pitot tubes are affected by the surrounding environment, air quality, and geometric deviations of the pitot tubes themselves, making measurements prone to errors. Furthermore, they require specific placement in locations where real-time pressure monitoring is required, making them unsuitable for all aircraft structures. Furthermore, the pitot tubes themselves are heavy, and some aircraft require two to four pitot tube speed measurement systems, increasing overall weight and complexity. Because fixed-wing UAV wing lift requires airspeed to generate a pressure differential, flight control and status also need to be adjusted accordingly based on airspeed, placing higher demands on a high-precision, lightweight airspeed measurement system.

[0003] Flexible pressure sensors, as a new type of electronic device, can convert external pressure into easily detectable physical quantities (resistance, voltage, capacitance, etc.). They also possess excellent flexibility and are widely used in fields such as human-computer interaction and healthcare. By attaching a flexible pressure sensor array to the surface of a drone's wing, the wind pressure acting on the wing during flight can be detected. A neural network model can be used to analyze the relationship between airspeed and wind pressure on the wing surface, allowing drone airspeed measurement to be performed in place of traditional pitot tubes. This novel airspeed measurement method not only reduces the overall weight of the drone but also reduces its structural complexity. Therefore, developing a flexible pressure sensor array for drone airspeed measurement, replacing pitot tubes for airspeed measurement, is of great significance.

[0004] After searching the prior art, Yanan Ma, Nishuang Liu, et al. from Huazhong University of Science and Technology published an article titled "A highly flexible and sensitive piezoresistive sensor based on MXene with greatly changed interlayer distances" in Nature Communications, 2017, 8(1):1207. The sensor they prepared exhibited high sensitivity (strain factor ~180.1) and fast response (<30ms). However, this method directly drips the MXene solution between the interdigitated electrodes and dries it to form a single-layer MXene piezoresistive layer. The lack of microstructure design results in low overall compressibility of the sensor and a small pressure detection range.

[0005] Dan Yang, Hengyu Guo et al. wrote an article titled "A flexible and wide pressure range triboelectric sensor array for real-time pressure detection and distribution mapping" in Journal of Materials Chemistry A, 2020, 8(45): 23827-23833. They prepared a flexible pressure sensor array for detecting the magnitude and distribution of pressure. However, the arraying of sensors on a whole flexible polyimide film makes the Young's modulus of the overall structure too high, resulting in insufficient overall flexibility of the sensor array. It can only be used for pressure detection on flat or simple curved surfaces, and it is difficult to achieve conformal attachment to complex curved surfaces.

[0006] Li, X., Li, S., et al., in their article "Multifunctional polyether block amides / carbon nanostructures piezoresistive foams with largely linear range, enhanced and humidity-regulated microwave shielding," published in Chemical Engineering Journal, 2023, 455:140860, used a conductive polymer foam composed of polyether block amide (PEBA) and carbon nanotubes as a pressure sensor. However, PEBA has a low Young's modulus. When pressure is high, the sensitive layer reaches its upper compressible limit and its impedance no longer changes, making it difficult to achieve wide-range pressure detection. Furthermore, in order to meet the demand for drone airspeed measurement, which requires the sensor to bear pressure for a long time, the foam structure suffers from structural collapse during compression deformation.

[0007] Therefore, in response to the needs of UAV airspeed measurement, especially fixed-wing UAV airspeed measurement, existing flexible pressure sensors have problems such as small pressure detection range, easy collapse of foam structure, and poor conformal adhesion due to insufficient array softness. Summary of the Invention

[0008] In response to the defects and gaps in the existing technology, the present invention provides a highly flexible, wide-range flexible pressure sensor array for UAV airspeed measurement and a method for preparing the flexible pressure sensor array, which can effectively improve the pressure detection range, service life, softness and conformal attachment capability of the sensor array. At the same time, it meets the airspeed measurement needs of fixed-wing UAVs and provides a feasible solution for overall structural optimization and lightweight design.

[0009] To achieve the above objectives, the technical solutions provided by the present invention are:

[0010] On the one hand, a flexible pressure sensor array for measuring the airspeed of a UAV is provided, comprising a mesh structure and a plurality of flexible pressure sensors arranged at a plurality of nodes of the mesh structure in a one-to-one correspondence;

[0011] The mesh structure is used to attach to the leading edge of the drone's wing. It is made of a material that can be processed into a soft, waterproof, and insulating film. The nodes of the mesh structure are provided with hollow parts. The flexible pressure sensor is located in the hollow part, and the mesh film serves as an encapsulation layer.

[0012] Each flexible pressure sensor adopts a sandwich structure, with a sensitive layer in the middle and symmetrical flexible base layers and electrode layers on the top and bottom. The electrode layers are bonded and electrically connected to the sensitive layer. The sensitive layer is a composite conductive foam with a conductive elastomer-filled skeleton. The composite conductive foam of the sensitive layer is obtained by repeatedly dipping the foam in a conductive material solution. The skeleton of the sensitive layer is obtained by laser arraying through holes in the composite conductive foam and filling the through holes with conductive elastomer.

[0013] Furthermore, the foam of the sensitive layer adopts one or more of polyurethane, melamine, polystyrene and polypropylene; the conductive material of the sensitive layer adopts one or more of MXene, AgNW, CNT, rGO and conductive polymer; the conductive elastomer of the sensitive layer adopts one or more of PDMS / CNT, TPU / AgNWs and SEBS / CNT.

[0014] Further, the encapsulation layer is made of one or more of PET, PDMS and PI.

[0015] Furthermore, the flexible substrate layer is a flexible PI film, and the electrode layer is made of metallic silver deposited by magnetron sputtering.

[0016] Furthermore, the mesh structure is an interconnected diamond mesh structure and includes nine nodes.

[0017] Furthermore, the hollow parts in the nodes of the mesh structure and the flexible pressure sensors therein are circular, and the parts connecting the nodes are long strips.

[0018] Furthermore, the thickness of the packaging layer is 100-200 μm, the thickness of the flexible substrate layer is 50-300 μm, the thickness of the electrode layer is 10-500 μm, the thickness of the sensitive layer is 0.1-2.0 mm, and the single pressure sensor is circular with a diameter of 1-5 cm.

[0019] On the other hand, a method for preparing the flexible pressure sensor array for measuring the airspeed of a UAV is provided, comprising the following steps:

[0020] Step 1: Clean and treat the film serving as the flexible base layer, and magnetron sputter a layer of metal on the surface of the film as an electrode layer;

[0021] Step 2, preparing multiple composite conductive foams with conductive elastomer-filled skeletons as sensitive layers, including the following sub-steps:

[0022] Step 2.1, after low-pressure oxygen plasma modification of the high-porosity open-cell foam, the composite conductive foam is obtained by soaking and drying the foam in a conductive material solution and repeating the cycle multiple times;

[0023] Step 2.2, etching arrayed through holes on the composite conductive foam, cleaning the hole walls with oxygen plasma, preparing a conductive elastomer solution, injecting the solution into the etched through holes, and curing it with ultraviolet light to complete the preparation of the sensitive layer;

[0024] Step 3: sandwiching each sensitive layer between two flexible substrate layers and electrode layers connected with wires, electrically connecting and bonding them, thereby obtaining a plurality of flexible pressure sensors to be packaged;

[0025] Step 4: preparing a packaging mold with a network structure, wherein the mold as a whole is a network structure, including node casting grooves and connecting casting grooves connecting the node casting grooves to each other;

[0026] Step 5: Prepare a solution for forming an encapsulation layer, inject part of the solution into the mold, and after semi-solidification, place the multiple pressure sensors to be encapsulated into different node casting grooves in the mold, place the wires into the mold, and then inject the remaining solution so that each sensor is completely wrapped. After curing, a flexible pressure sensor array is obtained.

[0027] Furthermore, the composite conductive foam obtained in step 2.1 is a PU-MXene composite conductive foam; step 2.2 includes: using a CO2 laser to etch arrayed through holes on the PU-MXene composite conductive foam, cleaning the pore walls with oxygen plasma, preparing a PDMS / CNT mixed solution, adding fumed silica to enhance thixotropy, and then adding a photoinitiator 2-hydroxy-2-methylpropiophenone to prepare a thixotropic-photocurable PDMS / CNT slurry, injecting the mixed slurry into the through holes using a syringe, and rapidly curing it using ultraviolet light to obtain a MXene-PDMS / CNT heterogeneous network porous foam as a sensitive layer.

[0028] Furthermore, in step 1, a PI film is used as a flexible substrate layer, and a layer of metallic silver is magnetron sputtered on the surface of the PI film to complete the preparation of the PI-Ag electrode; step 3 includes: using silver paste to connect the silver wire to the Ag side of the PI-Ag electrode, and then sandwiching the prepared MXene-PDMS / CNT heterogeneous network porous foam between two layers of PI-Ag electrode layers connected with the wires, and bonding them with silver paste.

[0029] The advantages of the present invention are:

[0030] The flexible pressure sensor array for measuring the airspeed of unmanned aerial vehicles (UAVs) proposed in the present invention comprises a mesh structure and a plurality of flexible pressure sensors housed within hollow portions at multiple nodes of the mesh structure. The flexible pressure sensors are sandwich-shaped, with a symmetrical flexible substrate layer and an electrode layer on top and bottom, and a sensitive layer in the middle comprising a composite conductive foam with a conductive elastomer-filled skeleton. Therefore, when the flexible pressure sensor array of the present invention is attached to the leading edge of a wing to record pressure at multiple angles and directions within the three-dimensional space of the wing surface, when the pressure is low, the contact resistance change of the porous composite conductive foam dominates the response, increasing the contact area and the number of conductive paths, thereby improving the conductivity. At the same time, when the multi-layer conductive material attached to the foam is compressed, the layer spacing decreases, further improving the conductivity of the composite material. When the pressure is high, the tunneling effect of the conductive elastomer skeleton filled in the foam dominates the response, the spacing between the conductive fillers decreases, and electrons tunnel through the insulating elastomer matrix barrier to form a tunneling current, thereby converting the difficult-to-measure large-scale pressure changes into easily detectable changes in physical impedance. Therefore, the conductive elastomer serves as the "skeleton" of the sensitive layer, and the porous composite conductive foam serves as the "nerve" of the sensitive layer, forming a synergistic conductive network to achieve multi-level pressure response and expand the pressure detection range; at the same time, the array-filled conductive elastomer skeleton improves the problem of easy collapse of the foam structure under compressive deformation, thereby extending the service life of the sensor array.

[0031] 2. The sensor array designed in the present invention has a mesh structure. Compared with the traditional sensor array prepared on a whole flexible substrate, the design of the Internet is used to greatly reduce the Young's modulus of the overall structure of the sensor array, and improve the conformal adhesion ability to the curved surface of the leading edge of the drone wing, effectively solving the problem of poor conformal adhesion ability of existing array sensors due to insufficient softness of the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and / or other features and advantages of the present invention will become more readily understood through the following description with reference to the accompanying drawings, which are not drawn to scale and in which some features are exaggerated or minimized to show details of particular components.

[0033] Figure 1 This is a diagram of the overall structure of the flexible pressure sensor array for UAV airspeed measurement and a schematic diagram of the sensor microstructure of the present invention;

[0034] Figure 2 Schematic diagram of the preparation process of the flexible pressure sensor of the present invention;

[0035] Figure 3 Schematic diagram of the preparation process of the heterogeneous network porous foam of the flexible pressure sensor of the present invention;

[0036] Figure 4is a schematic diagram of the structural change of the heterogeneous network porous foam of the flexible pressure sensor in the application when the heterogeneous network porous foam is pressed;

[0037] Figure 5 is a schematic diagram of the change of the hierarchical spacing of the multilayer conductive material of the flexible pressure sensor in the application when the multilayer conductive material is pressed;

[0038] Figure 6 is a schematic diagram of the flexible pressure sensor array of the application attached to the leading edge of the fixed-wing unmanned aerial vehicle wing.

[0039] In the figure: 1-net structure; 2-flexible pressure sensor; 3-flexible base layer; 4-electrode layer; 5-sensitive layer, 51-polyurethane (PU) foam, 52-PU-MXene composite conductive foam, 53-MXene-PDMS / CNT heterogeneous network porous foam; 100-flexible pressure sensor array; 200-fixed-wing unmanned aerial vehicle, 201-leading edge of the wing. DETAILED DESCRIPTION

[0040] The application will be described in detail below with reference to the accompanying drawings by means of exemplary embodiments of the application. It should be pointed out that the following detailed description of the application is for illustrative purposes only and is not limiting on the application.

[0041] The application provides a flexible pressure sensor array for unmanned aerial vehicle airspeed measurement and a preparation method of the flexible pressure sensor array, which is used to be attached to the surface of the leading edge of the unmanned aerial vehicle wing, records the pressure received by the wing surface in three-dimensional space at multiple angles and directions, uses a neural network model to complete the analysis and prediction of the relationship between the pressure value and the airspeed, and realizes the airspeed measurement during flight instead of the traditional airspeed tube.

[0042] Reference Figure 1 The flexible pressure sensor array for unmanned aerial vehicle airspeed measurement provided by the application is in a net structure and includes a net structure and a plurality of flexible pressure sensors 2 arranged one-to-one at a plurality of nodes of the net structure 1. The net structure 1 is used to be attached to the leading edge of the unmanned aerial vehicle wing, and the flexible pressure sensor 2 is used to record the pressure received by the wing surface.

[0043] In the embodiment shown in the application, the net structure 1 is an interconnected diamond net structure and includes five rows of nine nodes, specifically, one node is arranged at the top vertex and the middle of the diamond and the middle of the four edges, however, this does not limit the application, and different sensor array structures can be designed according to the complexity and shape of the different curved surfaces to which the sensor array is attached. The net structure 1 is made of a material capable of being processed into a soft waterproof insulating film, which is one or more of PET, PDMS and polyimide (PI), and is preferably made of a PDMS film.

[0044] Each node of the mesh structure 1 has a hollow portion, within which the flexible pressure sensor 2 is located. The thin film of the mesh structure 1 serves as an encapsulation layer, which can be 100 to 200 μm thick. Preferably, the hollow portion within the nodes of the mesh structure 1 and the individual flexible pressure sensors 2 therein are circular. Generally, the diameter of the circle is greater than the thickness, and can be 1 to 5 cm. The portion connecting the nodes is an elongated strip, which, along with the encapsulation layer at the bottom of the flexible pressure sensor, adheres to the drone surface.

[0045] Each flexible pressure sensor 2 utilizes a sandwich structure, with a sensitive layer 5 in the center and symmetrical flexible substrate layers 3 and electrode layers 4 above and below. The electrode layer 4 is bonded and electrically connected to the sensitive layer 5. The thickness of the flexible substrate layer 3 can optionally be 50 to 300 μm, and the thickness of the electrode layer 4 can be 10 to 500 μm. In some embodiments, the flexible substrate layer 3 is a flexible PI film, and the electrode layer 4 is made of metallic silver deposited by magnetron sputtering.

[0046] The sensitive layer 5 is a composite conductive foam with a conductive elastomer-filled skeleton. It has a relatively thin thickness, particularly 0.1 to 2.0 mm. The composite conductive foam of the sensitive layer 5 is obtained by repeatedly dipping the foam into a conductive material solution. The skeleton of the sensitive layer 5 is formed by laser-forming through-holes in the composite conductive foam and then filling the through-holes with the conductive elastomer. According to the present invention, the foam of the sensitive layer 5 is made of one or more of polyurethane (PU), melamine, polystyrene, and polypropylene; the conductive material of the sensitive layer 5 can be made of one or more of MXene, AgNW, CNT, rGO, and a conductive polymer; and the conductive elastomer of the sensitive layer 5 is made of one or more of PDMS / CNT, TPU / AgNWs, and SEBS / CNT. The former is an insulating elastomer matrix, and the latter is a conductive filler. According to the present invention, it is preferred to use polyurethane as the foam of the sensitive layer, MXene as the conductive material of the sensitive layer, and PDMS / CNT as the conductive elastomer of the sensitive layer. Alternatively, polyimide foam can be used as the porous network structure of the sensitive layer and immersed in a silver nanowire solution to prepare a composite conductive foam sensitive layer. Polyimide foam can withstand high temperatures up to 400°C and is suitable for pressure detection in high-temperature environments such as the aerospace industry and high-temperature industrial equipment.

[0047] The sensor array of the present invention has a mesh structure. Compared with the traditional sensor array prepared on a whole flexible substrate, the design of the Internet is used to greatly reduce the Young's modulus of the overall structure of the sensor array, making it easier to conformally attach to the leading edge surface of the drone wing, thereby improving the conformal attachment capability to the leading edge surface of the wing.

[0048] The method for preparing the flexible pressure sensor array for measuring the airspeed of a UAV provided by the present invention may include the following steps:

[0049] Step S1, cleaning and treating the film serving as the flexible base layer, and magnetron sputtering a layer of metal on the surface of the film as an electrode layer;

[0050] Step S2, preparing a plurality of composite conductive foams with a conductive elastomer-filled skeleton as a sensitive layer;

[0051] Step S3, sandwiching each sensitive layer between two flexible substrate layers and electrode layers connected with wires, and electrically connecting and bonding them, thereby obtaining a plurality of flexible pressure sensors to be packaged;

[0052] Step S4, preparing a packaging mold with a network structure, wherein the mold as a whole is a network structure, including node casting grooves and connecting casting grooves connecting the node casting grooves to each other;

[0053] Step S5: prepare a solution for forming an encapsulation layer, inject part of the solution into the mold, and after semi-solidification, place the multiple pressure sensors to be encapsulated into different node casting grooves in the mold, place the wires into the mold, and then inject the remaining solution so that each sensor is completely wrapped. After curing, a flexible pressure sensor array is obtained.

[0054] Step S2 specifically includes the following sub-steps:

[0055] Step S2.1, after low-pressure oxygen plasma modification of the high-porosity open-cell foam, the composite conductive foam is subjected to a soaking-drying cycle in a conductive material solution and repeated multiple times;

[0056] Step S2.2, etching arrayed through holes on the composite conductive foam, cleaning the hole walls with oxygen plasma, preparing a conductive elastomer solution, and injecting the solution into the etched through holes, and curing it with ultraviolet light to complete the preparation of the sensitive layer.

[0057] Reference Figure 2 In the embodiment shown in the present invention, the preparation method is specifically implemented by the following steps:

[0058] In the first step, a polyimide (PI) film with a diameter of 3 cm was prepared by laser cutting and surface treatment was performed using oxygen plasma. The PI film was then fixed on a substrate holder in a vacuum chamber and the vacuum pump was started to reduce the pressure to 1.3x10 -3 Pa, then high-purity argon (Ar) is filled as the working gas, and magnetron sputtering is started to sputter a layer of metallic silver on the surface of the PI film to complete the preparation of the PI-Ag electrode;

[0059] Step 2: Refer to Figure 3As shown in FIG, first, a 0.1 mm thick, high-porosity, open-cell polyurethane (PU) foam 51 is exposed to 50 Pa of low-pressure oxygen and discharged in a plasma chamber to complete oxygen plasma surface treatment to obtain a modified polyurethane foam. By low-pressure oxygen plasma treatment, polar groups can be introduced on the PU surface, making the PU foam have good hydrophilicity and improving the adhesion between PU and MXene. Then, the modified PU foam is immersed in a multilayer MXene (Ti3C2T X ) solution, and then immersed again after drying, and five immersion-drying cycles were performed to make a layer of MXene (Ti3C2T X ) forming a PU-MXene composite conductive foam 52;

[0060] In the third step, a CO2 laser is used to process the PU-MXene composite conductive foam 52 prepared in the previous step, and arrayed through-holes are laser-etched. The pore walls are then cleaned with oxygen plasma to enhance the bonding strength. A PDMS / CNT mixed solution is prepared with a ratio of 10:1 between the PDMS prepolymer and the curing agent and a CNT addition amount of 5% of the PDMS mass. 1% of the total mass of PDMS is added with fumed silica to enhance the thixotropy and achieve shear thinning, thereby solving the problem of poor fluidity of high-viscosity materials during injection. At the same time, the viscosity is quickly restored after shearing is stopped to prevent the material from penetrating the porous structure. 2-hydroxy-2-methylpropiophenone, a photoinitiator, is then added to 1% of the total mass of PDMS. The mixed thixotropic-photocurable PDMS / CNT slurry is injected into the through-holes using a syringe and rapidly cured using ultraviolet light, completing the preparation of the MXene-PDMS / CNT heterogeneous network porous foam 53.

[0061] In the fourth step, silver paste was used to bond the silver wire to the silver-plated side of the PI-Ag electrode, and then the MXene-PDMS / CNT heterogeneous network porous foam 53 was sandwiched between the two PI-Ag electrodes and bonded with silver paste to complete the preparation of a single sensor.

[0062] Step 5: Prepare a packaging mold with a diamond-shaped network structure. The mold as a whole is a network structure, including multiple circular casting grooves and rectangular casting grooves connecting the circular grooves.

[0063] In the sixth step, a PDMS solution is prepared in a ratio of 10:1 between the base polymer and the cross-linking agent, and the PDMS solution is introduced into a mold of an interconnected diamond network structure. After semi-curing, the prepared multiple sensors are placed one by one into the circular grooves of the mold. After drying, the interconnected diamond network structure flexible pressure sensor array is completed.

[0064] Reference Figure 4When the flexible pressure sensor array of the present invention is used to measure the airspeed of a drone, when the pressure is low, the contact resistance change of the porous composite conductive foam is the dominant response, the contact area increases, the conductive path increases, and the conductivity is improved. At the same time, when the multi-layer conductive material attached to the foam is compressed, the layer spacing will decrease, further improving the conductivity of the composite material; when the pressure is high, the tunneling effect of the conductive elastomer skeleton filled in the foam is the dominant response, the spacing between the conductive fillers is reduced, and electrons tunnel through the insulating elastomer matrix barrier to form a tunneling current, thereby converting the difficult-to-measure large-scale pressure changes into changes in the physical quantity impedance that is easy to detect. Thus, the conductive elastomer acts as the "skeleton" of the sensitive layer and the porous composite conductive foam acts as the "nerve" of the sensitive layer, forming a synergistic conductive network, achieving multi-level pressure response and expanding the pressure detection range; at the same time, the arrayed filled conductive elastomer skeleton improves the problem of easy collapse of the foam structure under pressure deformation, thereby extending the service life of the sensor array.

[0065] Reference Figure 5 After a conductive material such as MXene is attached to a foam such as PU, when the sensitive layer of the pressure sensor is compressed, the external force will cause the MXene hierarchical structure to change, reducing the interlayer spacing and thereby increasing the MXene conductivity and reducing the impedance. Therefore, after PU and MXene are compounded, the high compressibility of the PU foam itself and the pressure-induced layer change characteristics of MXene can be combined to improve the sensitivity of pressure detection.

[0066] Reference Figure 6 The flexible pressure sensor array 100 can be conformally and tightly attached to the curved surface of the leading edge 201 of the wing of the fixed-wing UAV 200. Multiple pressure sensors form a dense pressure sensing array distributed from top to bottom on the leading edge of the wing, which can effectively detect the pressure on the surface of the UAV wing in different directions during flight, and obtain the wind pressure distribution during flight in a three-dimensional range. The detected pressure distribution data is used to train and verify the convolutional neural network model, and a convolutional neural network model that can accurately predict the airspeed during flight is obtained, thereby replacing the traditional pitot tube to complete the airspeed measurement.

[0067] The mesh structure of the flexible pressure sensor array of the present invention can be modified in various ways. For example, when monitoring leg exercise pressure for sports health, because the leg muscles have a large range of activity, the sensor array can be designed as an interconnected serpentine mesh structure. The curved serpentine connection design improves the stretchability of the structure. When facing a variety of complex and large-scale leg movements, it can still maintain good adhesion performance to achieve long-term and reliable pressure monitoring.

[0068] Finally, it should be noted that features mentioned and / or shown in the above description of exemplary embodiments of the application can be combined with one or more other embodiments, either in the same or in different embodiments, than those in which the features are described. These combinations of features should also be considered as being within the scope of the application.

Claims

1. A flexible pressure sensor array for measuring airspeed of unmanned aerial vehicles, characterized by: It comprises a mesh structure and a plurality of flexible pressure sensors arranged at a plurality of nodes of the mesh structure in a one-to-one correspondence; The mesh structure is used to be attached to the leading edge of the drone's wing and is made of a material that can be processed into a soft waterproof insulating film. The nodes of the mesh structure are provided with hollow parts, and the flexible pressure sensor is located in the hollow part. The film of the mesh structure serves as an encapsulation layer. Each flexible pressure sensor adopts a sandwich structure, with a sensitive layer in the middle and symmetrical flexible base layers and electrode layers on the top and bottom. The electrode layers are bonded and electrically connected to the sensitive layer. The sensitive layer is a composite conductive foam with a conductive elastomer-filled skeleton. The composite conductive foam of the sensitive layer is obtained by repeatedly dipping the foam in a conductive material solution, and the skeleton of the sensitive layer is obtained by laser arraying through holes in the composite conductive foam and filling the through holes with conductive elastomer.

2. The flexible pressure sensor array for UAV airspeed measurement according to claim 1, characterized in that: The foam of the sensitive layer is made of one or more of polyurethane, melamine, polystyrene and polypropylene; The conductive material of the sensitive layer is one or more of MXene, AgNW, CNT, rGO and conductive polymer; The conductive elastomer of the sensitive layer is one or more of PDMS / CNT, TPU / AgNWs and SEBS / CNT.

3. The flexible pressure sensor array for UAV airspeed measurement according to claim 1 or 2, characterized in that: The encapsulation layer is made of one or more of PET, PDMS and PI.

4. The flexible pressure sensor array for UAV airspeed measurement according to claim 1 or 2, characterized in that: The flexible substrate layer is a flexible PI film, and the electrode layer is made of metallic silver deposited by magnetron sputtering.

5. The flexible pressure sensor array for UAV airspeed measurement according to claim 1 or 2, characterized in that: The mesh structure is an interconnected diamond mesh structure and includes nine nodes.

6. The flexible pressure sensor array for UAV airspeed measurement according to claim 1 or 2, characterized in that: The hollow parts in the nodes of the mesh structure and the flexible pressure sensors therein are circular, and the parts connecting the nodes are long strips.

7. The flexible pressure sensor array for UAV airspeed measurement according to claim 1 or 2, characterized in that: The thickness of the packaging layer is 100-200 μm, the thickness of the flexible base layer is 50-300 μm, the thickness of the electrode layer is 10-500 μm, the thickness of the sensitive layer is 0.1-2.0 mm, and a single pressure sensor is circular with a diameter of 1-5 cm.

8. A method for preparing a flexible pressure sensor array for measuring airspeed of an unmanned aerial vehicle according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1: Clean and treat the film serving as the flexible base layer, and magnetron sputter a layer of metal on the surface of the film as an electrode layer; Step 2, preparing multiple composite conductive foams with conductive elastomer-filled skeletons as sensitive layers, including the following sub-steps: Step 2.1, after low-pressure oxygen plasma modification of the high-porosity open-cell foam, the composite conductive foam is obtained by soaking and drying the foam in a conductive material solution and repeating the cycle multiple times; Step 2.2, etching arrayed through holes on the composite conductive foam, cleaning the hole walls with oxygen plasma, preparing a conductive elastomer solution, injecting the solution into the etched through holes, and curing it with ultraviolet light to complete the preparation of the sensitive layer; Step 3: sandwiching each sensitive layer between two flexible substrate layers and electrode layers connected with wires, electrically connecting and bonding them, thereby obtaining a plurality of flexible pressure sensors to be packaged; Step 4: preparing a packaging mold with a network structure, wherein the mold as a whole is a network structure, including node casting grooves and connecting casting grooves connecting the node casting grooves to each other; Step 5: Prepare a solution for forming an encapsulation layer, inject part of the solution into the mold, and after semi-solidification, place the multiple pressure sensors to be encapsulated into different node casting grooves in the mold, place the wires into the mold, and then inject the remaining solution so that each sensor is completely wrapped. After curing, a flexible pressure sensor array is obtained.

9. The preparation method according to claim 8, characterized in that The composite conductive foam obtained in step 2.1 is a PU-MXene composite conductive foam; step 2.2 includes: using a CO2 laser to etch arrayed through holes on the PU-MXene composite conductive foam, cleaning the pore walls with oxygen plasma, preparing a PDMS / CNT mixed solution, adding fumed silica to enhance thixotropy, and then adding a photoinitiator 2-hydroxy-2-methylpropiophenone to prepare a thixotropic-photocurable PDMS / CNT slurry. The mixed slurry is injected into the through holes using a syringe, and is rapidly cured using ultraviolet light to obtain a MXene-PDMS / CNT heterogeneous network porous foam as a sensitive layer.

10. The preparation method according to claim 9, characterized in that In step 1, PI film is used as the flexible substrate layer, and a layer of metallic silver is magnetron sputtered on the surface of the PI film to complete the preparation of the PI-Ag electrode; step 3 includes: using silver paste to connect the silver wire to the Ag side of the PI-Ag electrode, and then sandwiching the prepared MXene-PDMS / CNT heterogeneous network porous foam between two layers of PI-Ag electrode layers connected with the wires, and bonding them with silver paste.

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