Three-dimensional flexible sensing structure capable of measuring strain direction and strain magnitude and preparation method and application thereof

Abstract

The invention discloses a three-dimensional flexible sensing structure capable of measuring the strain direction and the strain magnitude and a preparation method and application thereof.The sensing structure comprises a three-dimensional flexible substrate, a flexible conductive electrode pair, a strain sensitive material, a wire and a resistance measurement external circuit, and a plurality of flexible square stand columns are distributed on one face of a flexible thin film at equal intervals; forming a three-dimensional flexible substrate; a plurality of groups of electrode units are arranged on the surface of the flexible thin film on the periphery of the flexible square stand, each group of electrode units comprises a flexible conductive electrode pair, and a flexible strain sensitive material is assembled and embedded in the flexible thin film in the area where each flexible conductive electrode pair is located; the flexible conductive electrode pair is connected with a resistance measurement external circuit through a wire to form a strain response unit, so that the flexible directed strain sensing array is formed. According to the invention, through a simple three-dimensional sensing structure design, a traditional isotropic flexible strain material can be endowed with synchronous measurement of a strain direction and a strain size, and the method has extremely high universality.

Description

Technical Field

[0001] The invention belongs to the field of sensors and detection instruments, and specifically relates to a three-dimensional flexible sensing structure capable of measuring strain direction and strain magnitude, and a preparation method and application thereof. Background Art

[0002] Flexible strain sensors have become an indispensable component in the Internet of Things and artificial intelligence data acquisition systems due to their advantages of high sensitivity, high resolution, light weight and low cost. Their application areas include human-machine interface, medical diagnosis, intelligent sensing and many other fields. Common flexible strain sensors are composed of nano-assembled sensitive elements and elastic polymer substrates. The responsiveness of these sensitive materials depends on the changes in the intrinsic electron transport of the sensitive elements caused by deformation when subjected to external mechanical stimulation. Since mechanical stimulation in each direction will induce the intrinsic response deformation of the sensing material, most flexible strain sensors can hardly identify the strain direction. Therefore, this type of strain sensor is limited to situations where the loading direction is clear, and is also easily disturbed by additional mechanical stimulation in different directions. A small number of designs have used sensitive materials with dimensional anisotropy to construct flexible strain sensors. These devices are only sensitive to strain signals in a single axial direction, so they can effectively distinguish the specific direction of strain. However, these sensitive designs not only require the sensitive materials to have dimensional anisotropy, but also have poor selectivity in the direction corresponding to the strain. Their preparation methods also rely on complex technologies such as electrospinning and directional lithography, which limits the wide range of their material selection and increases their production costs. Therefore, how to develop a flexible sensor with simple structure, low cost, excellent performance, and the ability to simultaneously measure strain direction and strain magnitude is still a difficult problem that needs to be urgently solved in the field of flexible sensing. Summary of the invention

[0003] In order to solve the technical defect that the existing flexible strain sensors cannot accurately detect the strain direction, the present invention provides a three-dimensional flexible sensing structure that can measure the strain direction and strain magnitude, as well as its preparation method and application. In the present invention, when the flexible substrate is loaded with mechanical tensile loads in different directions, the three-dimensional pillar structure on the substrate can provide additional shear strain constraints to convert the mechanical tensile load into a local distribution of strain on the substrate surface. These locally distributed strains will induce the electrical signals of the strain-sensitive materials at different positions on the surface of the flexible substrate to produce response strains of different amplitudes. By combining the response differences of the sensitive materials at each position, the strain magnitude and direction acting on the surface of the flexible substrate can be accurately analyzed, thereby solving the technical problem that traditional strain sensors cannot distinguish the strain direction.

[0004] The technical solution adopted by the present invention is as follows:

[0005] A three-dimensional flexible sensing structure capable of measuring strain direction and strain magnitude, comprising a three-dimensional flexible substrate, a pair of flexible conductive electrodes, a strain-sensitive material, a conductor and an external resistance measurement circuit, wherein an array of multiple equally spaced flexible square columns is distributed on one side of a flexible film to form the three-dimensional flexible substrate;

[0006] A plurality of groups of electrode units are arranged on the surface of the flexible film around the flexible square pillar, and each group of electrode units includes the flexible conductive electrode pairs distributed on the surface of the flexible film, and flexible strain sensitive materials are assembled, embedded and distributed on the flexible film in the area where each flexible conductive electrode pair is located; each flexible conductive electrode pair is connected to an external resistance measurement circuit by a wire to form a strain response unit, thereby forming a flexible directional strain sensor array.

[0007] Furthermore, the three-dimensional flexible substrate has a thickness of 0.05-0.1 mm, an elastic modulus of 0.1-4000 MPa, a shear modulus of 0.1-10 GPa, and is made of a high molecular polymer material;

[0008] The flexible square columns are evenly spaced in horizontal and vertical rows on the flexible film, the bottom side of the flexible square columns is a rectangle or a square, the side length of the rectangle or the square is 0.5mm-10mm, and the height of the flexible square columns is 0.5mm-5mm; the ratio between the distance between two adjacent flexible square columns and the length of the bottom side of the flexible square columns is 0.2-5:1;

[0009] The polymer material includes polydimethylsiloxane (PDMS), polyimide (PI) or polyurethane (PU), and the preparation scheme of the flexible square pillars on the flexible film is three-dimensional printing or template curing.

[0010] Furthermore, flexible conductive electrode pairs are arranged along the periphery of the four sides of the flexible square pillar, with a thickness of 50-500nm, and the material is gold, silver, copper, iron, aluminum or indium tin oxide. The conductive electrodes are printed on the three-dimensional flexible substrate, and the preparation scheme can be selected from inkjet printing, screen printing, flexible printing, magnetron sputtering or electron beam thermal evaporation coating.

[0011] Furthermore, the microscopic state of the strain sensitive material is ordered or disordered, and the resistance value is between 1-10 6 Ω, composed of flexible conductive nanostructures, optional nanostructures include metal nanoparticles, magnetic nanowires, carbon nanotubes, graphene, PVDF, chitosan or conductive ink, the flexible conductive electrode pairs and the flexible film surface in the area where they are located are covered with strain sensitive materials, and the preparation scheme is physical vapor deposition, electrospinning or chemical liquid phase synthesis.

[0012] Furthermore, the wire should have an anti-electromagnetic shielding function, and its diameter is 10-100 μm, including acetal enameled wire, polyester enameled wire or polyurethane enameled wire.

[0013] Furthermore, the acquisition frequency of the resistance measurement external circuit is 1-2000Hz, and the resistance acquisition range is 1-10 8 Ω.

[0014] The method for preparing a three-dimensional flexible sensing structure capable of measuring strain direction and strain magnitude comprises the following steps:

[0015] Step A: Select a polymer film for preparing a three-dimensional flexible substrate, the surface of which is smooth and clean without obvious scratches;

[0016] Step B: bonding a plurality of flexible square pillars of the same material evenly spaced in rows and columns to one side of the polymer film, and distributing an array of a plurality of equally spaced flexible square pillars to one side of the flexible film to form the three-dimensional flexible substrate;

[0017] Step C: printing a pair of flexible conductive electrodes on the surface of a polymer film as a three-dimensional flexible substrate along the periphery of the flexible square pillars by inkjet printing, screen printing, magnetron sputtering, flexible printing, photolithography coating or electron beam thermal evaporation coating, and the material is selected from metal gold, silver, copper, iron, aluminum or indium tin oxide;

[0018] Step D: adding a strain-sensitive material with a certain coverage rate to the polymer film in the area where the flexible conductive electrode pair is located, using a method of physical vapor deposition, electrospinning or chemical liquid phase synthesis, and the material is selected from metal nanoparticles, magnetic nanowires, carbon nanotubes CNTs, graphene, PVDF, chitosan or conductive ink;

[0019] Step E: After the strain sensitive material is deposited, the flexible conductive electrode pair is connected to the input terminal of the resistance measurement external circuit with a wire, and it is confirmed that the connection is normal.

[0020] Furthermore, the three-dimensional flexible sensing structure can measure the strain direction and strain magnitude, and the strain response unit in a certain direction is regarded as a lateral response unit, and the one perpendicular to the lateral response unit can be distinguished as a longitudinal response unit; if tensile strain is applied to the three-dimensional flexible substrate along the lateral strain unit, the flexible square pillars will provide additional shear strain resistance, hindering the deformation of the film under the flexible square pillars, and localizing the strain to the position of the lateral response unit between the flexible square pillars, while almost no strain is generated at the longitudinal response unit position. According to the differential comparison of the electrical signals between the lateral and longitudinal response units, the synchronous measurement of the strain magnitude and direction in the plane can be achieved; when tensile strain is applied in the longitudinal direction, the strain distribution on the flexible film is opposite.

[0021] Furthermore, the three-dimensional flexible substrate of the three-dimensional flexible sensing structure is fixed in a stretchable stepper motor device, and the relative resistance changes of the flexible conductive electrode pairs and strain-sensitive materials of the lateral response units and longitudinal response units on the surface of the three-dimensional flexible substrate under different strain rates are measured respectively, and a resistance change rate-strain rate curve is drawn, wherein the ordinate is the resistance change rate ΔR / R0 of the flexible conductive electrode pairs and the strain-sensitive materials, R0 is the resistance of the flexible conductive electrode pairs and the strain-sensitive materials in the original state, and ΔR is the difference between the resistance of the flexible conductive electrode pairs and the strain-sensitive materials in the stretched state and the resistance in the original state; the abscissa is the strain rate of the flexible film of the three-dimensional flexible substrate, and a linear regression curve is drawn according to the ordinate and the abscissa. The sensitivity coefficient GF of the flexible conductive electrode pairs and the strain-sensitive materials to strain can be obtained by calculating the slope of the linear regression curve, and is input into the resistance measurement external circuit to realize the calibration of the three-dimensional flexible sensing structure to strain and the distinction of different strain directions.

[0022] Furthermore, the three-dimensional flexible sensing structure is used in motion monitoring, machine operation, speech recognition or rehabilitation training.

[0023] The beneficial effects achieved by the present invention are as follows:

[0024] 1) Through a simple three-dimensional sensing structure design, the traditional isotropic flexible strain material can be given the ability to simultaneously measure the strain direction and strain magnitude, which is highly versatile. In the process of the flexible film being subjected to strain, the present invention uses flexible square columns to induce the unevenness of the strain distribution in the plane of the film, thereby inducing each strain response unit to generate response signals of different amplitudes, and finally determining the strain direction and magnitude based on the difference in response signals. This design is applicable to most strain-sensitive materials and is a universal flexible directional strain sensing design.

[0025] 2) Flexible sensitive materials can be selected according to different needs, with high adjustability and strong designability.

[0026] 3) The assembly method is simple, the material cost is low, and industrial mass production can be achieved.

[0027] This design proposes a strain sensing design based on a three-dimensional flexible sensitive structure. Strain is designed in different sizes, quantities, and column spacings to construct a sensor that can sense and distinguish the direction of strain. These three-dimensional structures are often assembled on the surface of a substrate that can undergo large deformations. The deformation of the substrate causes the resistance of the strain-sensitive material in different directions around the column to change, so that it can be used to measure the strain occurring in the substrate, as well as the micro-force and pressure applied to the substrate. Based on this, the applicant invented a three-dimensional flexible sensing structure design and application that can measure the direction and magnitude of strain. The design uses the upper layer of the three-dimensional flexible substrate to respond to the strain caused by stretching with a resistance. The design combines the three-dimensional flexible pillar structure on the basis of solidifying a flat thin layer of flexible substrate. The strain response unit in a certain direction is regarded as the lateral response unit, and the unit perpendicular to the lateral response unit can be distinguished as the longitudinal response unit. If the three-dimensional flexible substrate is subjected to tensile strain along the lateral strain unit, the flexible square pillar will provide additional shear strain, hindering the deformation of the film under the pillar, and localizing the strain to the position of the lateral response unit between the pillars, while the longitudinal response unit position almost does not produce strain. When tensile strain is applied in the longitudinal direction, the strain distribution on the flexible film is opposite. According to the differential comparison of the electrical signals between the lateral and longitudinal response units, the synchronous measurement of the strain size and direction in the plane can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the design and application of a three-dimensional flexible sensing structure capable of measuring strain direction and strain magnitude according to the present invention:

[0029] Three-dimensional flexible substrate 1, electrode 2, strain sensitive material 3, wire 4, resistance measurement external circuit 5.

[0030] Figure 2 These are the corresponding curves of the design of the present invention for the change of strain parallel to and perpendicular to the stretching direction.

[0031] Figure 3 It is a repeated test curve of the design of the present invention at different strain rates.

[0032] Figure 4 It is the real-time response curve of the design of the present invention to human joint activities. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0034] Example 1

[0035] A flexible sensor with a three-dimensional pillar structure that can measure strain direction and strain magnitude was prepared. The preparation steps are as follows:

[0036] 1) A flexible polymer film is used as the three-dimensional flexible substrate 1, the selected film is a PDMS film, the film thickness is 0.5 mm, the film elastic modulus is 3 MPa, and the surface is clean and smooth without obvious scratches;

[0037] 2) Multiple flexible square columns of the same material are solidified and bonded to the upper surface of the three-dimensional flexible substrate 1. The flexible square columns are made of PDMS, with an elastic modulus of 3MPa and a height of 1mm. The bottom of the flexible square column is a square with a side length of 8mm. The distance between two adjacent flexible square columns is 20mm. Figure 1 In the figure, nine flexible square pillars are solidified and bonded on the upper surface of the three-dimensional flexible substrate 1, arranged in three horizontal directions and three vertical directions.

[0038] 3) Printing flexible conductive electrode pairs 2 on the upper surface of the three-dimensional flexible substrate 1 along the corresponding positions near the four sides of the flexible square pillar, Figure 1 In the figure, four flexible conductive electrode pairs 2 are printed around the four sides of the flexible square column.

[0039] The flexible conductive electrode pair 2 used is a forked electrode with an electrode gap of 0.2 mm, prepared by vacuum mask evaporation process, the electrode material is silver, the thickness is 400 nm, the electrode resistance is 10Ω, and each pair of forked electrodes is insulated;

[0040] 4) Strain sensitive material 3 with the same coverage should be added on the surface of the three-dimensional flexible substrate in the area where each flexible conductive electrode pair 2 is located. The material used for the strain sensitive material 3 is Pd nanoparticle lattice, and the deposition process used is nanocluster beam deposition. The atoms generated by sputtering of a metal palladium target with a purity of 99.999% are nucleated and grown into palladium clusters after colliding with the buffer gas, and are deposited between the interdigitated electrodes; the particle size of the deposited nanoclusters is controlled to be 3-5nm, the coverage rate in the area where the two conductive electrodes 2 are located is 70%, and the resistance is 10 6 Ω.

[0041] 5) The three-dimensional flexible substrate 1 on which the Pd nanocluster lattice is deposited is placed in a normal pressure environment, and the flexible conductive electrode pairs 2 and the input terminals of the resistance measurement external circuit 5 are connected one by one by wires 4 (wires 4 are enameled wires).

[0042] 6) The three-dimensional flexible substrate 1 connected with the wire 4 and the resistance measurement external circuit 5 is placed in an environment of normal temperature and pressure, and the three-dimensional flexible substrate 1 is fixed in a stretchable stepper motor device. The stretching distance of the stepper motor is changed through the Labview program, and then the corresponding response behaviors of the flexible conductive electrode pair 2 and the strain sensitive material 3 are tested within the strain rate range of 0-5%. The stretching direction is regarded as the parallel stretching direction, and the direction perpendicular to the parallel stretching direction is the vertical stretching direction.

[0043] By applying a tensile force in a parallel tensile direction to the three-dimensional flexible substrate 1, the strain rate of the PDMS film of the three-dimensional flexible substrate 1 is made within the strain rate range of 0-5%, and the relative resistance changes of the flexible conductive electrode pair 2 and the strain sensitive material 3 in the parallel tensile direction and the perpendicular tensile direction on the surface of the three-dimensional flexible substrate 1 under different strain rates are measured respectively, and the resistance change rate-strain rate curve is plotted. The results are shown in FIG. Figure 2 As shown in the figure, the relative resistance change curves of the flexible conductive electrode pair 2 and the strain sensitive material 3 on the surface of the three-dimensional flexible substrate 1 parallel to and perpendicular to the stretching direction are shown, wherein the abscissa is the strain rate of the PDMS film strain, and the ordinate is the change rate of the resistance of the conductive electrode 2 and the strain sensitive material 3. A linear regression curve is drawn according to the ordinate and the abscissa, and the sensitivity coefficient GF to strain is obtained by calculating the slope of the linear regression curve.

[0044] The sensitivity coefficient is Figure 2 It can be reflected in the strain curve, that is, the slope of the linear regression curve of the resistance-strain curve, expressed by GF. The larger the value, the higher the sensitivity within the strain range.

[0045] 7) The three-dimensional flexible substrate 1 connected with the wire 4 and the resistance measurement external circuit 5 is placed in an environment of normal temperature and pressure, and the three-dimensional flexible substrate 1 is fixed in a stretchable stepper motor device. The stretching distance of the stepper motor is changed through the Labview program, and the corresponding repeated response behaviors of the flexible conductive electrode pair 2 and the strain sensitive material 3 are tested at strain rates of 0.1%, 0.2%, 0.5%, 0.8%, and 1%, and the resistance change rate curve is plotted as shown in FIG. Figure 3 shown.

[0046] Figure 3 One peak in the graph represents stretch recovery, which indicates the number of stretches during which the measuring device records the electrical signal value of the sample.

[0047] Example 2

[0048] This example tests the ability of the flexible sensor prepared in Example 1 to monitor the strain magnitude and strain direction in real time. During the test, the maximum length reached by the sensor when it is not stretched is taken as the initial value, and the current of the flexible conductive electrode pair 2 and the strain sensitive material 3 in the sensor in this state is taken as the initial current I0. Thereafter, the sensor is placed on the skin at the joint of the human body, and the strain magnitude and strain direction are different from the initial state by repeating the joint bending action of different amplitudes and directions. Figure 4The sensor sample was attached to the wrist and the changes in the sensor's output signal were recorded when the wrist joint was swung downward. It was found that during the wrist swing, the strain caused by the joint movement was concentrated in one direction, causing the electrode signal parallel to this direction to change significantly, while the signal change of the electrode in the other direction was not obvious, indicating that the design has a distinguishing effect on the strain direction; and the degree of wrist bending also has a direct impact on the amplitude of change of the electrode signal. The greater the degree of bending, the greater the tensile strain of the sensor, so the magnitude of the strain can be determined based on the amplitude of change of the electrical signal.

[0049] The above experiments prove that the design of the present invention can synchronously measure the strain direction and strain magnitude.

[0050] The contents described in this specification are merely an enumeration of implementation forms of the inventive concept, and the protection scope of the present invention should not be regarded as being limited to the specific forms described in the embodiments.

Claims

1. A three-dimensional flexible sensing structure capable of measuring strain direction and strain magnitude, characterized in that It comprises a three-dimensional flexible substrate (1), a pair of flexible conductive electrodes (2), a strain-sensitive material (3), a conductor (4) and an external resistance measurement circuit (5), wherein an array consisting of a plurality of equally spaced flexible square pillars is distributed on one side of the flexible film to form the three-dimensional flexible substrate (1); A plurality of groups of electrode units are arranged on the surface of the flexible film around the flexible square pillar, each group of electrode units includes the flexible conductive electrode pairs (2) distributed on the surface of the flexible film, and a flexible strain sensitive material (3) is assembled, embedded and distributed on the flexible film in the area where each flexible conductive electrode pair (2) is located; each flexible conductive electrode pair (2) is connected to an external resistance measurement circuit (5) by a wire (4) to form a strain response unit, thereby forming a flexible directional strain sensor array.

2. A three-dimensional flexible sensing structure capable of measuring strain direction and strain magnitude as claimed in claim 1, characterized in that The three-dimensional flexible substrate (1) has a thickness of 0.05-0.1 mm, an elastic modulus of 0.1-4000 MPa, and a shear modulus of 0.1-10 GPa, and is made of a high molecular polymer material; The flexible square columns are evenly arranged in horizontal and vertical rows on the flexible film, the bottom side of the flexible square columns is a rectangle or a square, the side length of the rectangle or the square is 0.5 mm to 10 mm, and the height of the flexible square columns is 0.5 mm to 5 mm; the ratio between the spacing between two adjacent flexible square columns and the length of the bottom side of the flexible square columns is 0.2 to 5:1; The polymer material includes polydimethylsiloxane (PDMS), polyimide (PI) or polyurethane (PU), and the preparation scheme of the flexible square pillars on the flexible film is three-dimensional printing or template curing.

3. A three-dimensional flexible sensing structure capable of measuring strain direction and strain magnitude as claimed in claim 1, characterized in that The flexible conductive electrode pair (2) is arranged along the periphery of the flexible square pillar, has a thickness of 50-500nm, and is made of gold, silver, copper, iron, aluminum or indium tin oxide. The conductive electrode (2) is printed on the three-dimensional flexible substrate (1). The preparation method can be inkjet printing, screen printing, flexible printing, magnetron sputtering or electron beam thermal evaporation coating.

4. A three-dimensional flexible sensing structure capable of measuring strain direction and strain magnitude as claimed in claim 1, characterized in that The strain sensitive material (3) is in an ordered or disordered microscopic state, and its resistance value is between 1 and 10 6 Ω, composed of flexible conductive nanostructures, the optional nanostructures include metal nanoparticles, magnetic nanowires, carbon nanotubes, graphene, PVDF, chitosan or conductive ink, the flexible conductive electrode pair (2) and the flexible film surface in the area where they are located are covered with strain sensitive material (3), and the preparation scheme is physical vapor deposition, electrostatic spinning or chemical liquid phase synthesis.

5. A three-dimensional flexible sensing structure capable of measuring strain direction and strain magnitude as claimed in claim 1, characterized in that The wire (4) should have an anti-electromagnetic shielding function, and its diameter is 10-100 μm, including acetal enameled wire, polyester enameled wire or polyurethane enameled wire.

6. A three-dimensional flexible sensing structure capable of measuring strain direction and strain magnitude as claimed in claim 1, characterized in that The resistance measurement external circuit (5) has a collection frequency of 1-2000 Hz and a resistance collection range of 1-10 8 Ω.

7. A method for preparing a three-dimensional flexible sensing structure capable of measuring strain direction and strain magnitude as claimed in claim 1, characterized in that The following steps are involved: Step A: Selecting a polymer film for preparing a three-dimensional flexible substrate (1) whose surface is smooth and clean without obvious scratches; Step B: bonding a plurality of flexible square pillars of the same material evenly spaced in rows and columns to one side of the polymer film, and distributing an array of a plurality of flexible square pillars at equal intervals on one side of the flexible film to form the three-dimensional flexible substrate (1); Step C: printing a pair of flexible conductive electrodes (2) on the surface of a high molecular polymer film as a three-dimensional flexible substrate (1) along the periphery of the flexible square pillars by inkjet printing, screen printing, magnetron sputtering, flexible printing, photolithography coating or electron beam thermal evaporation coating, with the material selected from metals such as gold, silver, copper, iron, aluminum or indium tin oxide; Step D: adding a certain coverage of strain sensitive material (3) on the polymer film in the area where the flexible conductive electrode pair (2) is located, using a physical vapor deposition, electrostatic spinning or chemical liquid phase synthesis method, and the material is selected from metal nanoparticles, magnetic nanowires, carbon nanotubes CNTs, graphene, PVDF, chitosan or conductive ink; Step E: After the strain sensitive material (3) is deposited, the flexible conductive electrode pair (2) is connected to the input end of the resistance measurement external circuit (5) by a wire (4), and it is confirmed that the connection is normal.

8. Application of the three-dimensional flexible sensing structure as claimed in claim 1, characterized in that The three-dimensional flexible sensing structure can measure the strain direction and strain magnitude. The strain response unit in a certain direction is regarded as a transverse response unit, and the one perpendicular to the transverse response unit can be distinguished as a longitudinal response unit. If tensile strain is applied to the three-dimensional flexible substrate (1) along the transverse strain unit, the flexible square column will provide additional shear strain resistance to hinder the deformation of the film below the flexible square column, localize the strain to the position of the transverse response unit between the flexible square columns, and almost no strain is generated at the longitudinal response unit. According to the differential comparison of the electrical signals between the transverse and longitudinal response units, the synchronous measurement of the strain magnitude and direction in the plane can be realized. When tensile strain is applied in the longitudinal direction, the strain distribution on the flexible film is opposite.

9. The use according to claim 8, characterized in that The three-dimensional flexible substrate (1) of the three-dimensional flexible sensing structure is fixed in a stretchable stepper motor device, and the relative resistance changes of the flexible conductive electrode pair (2) and the strain sensitive material (3) of the lateral response unit and the longitudinal response unit on the surface of the three-dimensional flexible substrate (1) are measured respectively under different strain rates, and a resistance change rate-strain rate curve is drawn, wherein the ordinate is the resistance change rate ΔR / R0 of the flexible conductive electrode pair (2) and the strain sensitive material (3), R0 is the resistance of the flexible conductive electrode pair (2) and the strain sensitive material (3) in the original state, and ΔR is the difference between the resistance of the flexible conductive electrode pair (2) and the strain sensitive material (3) in the stretched state and the resistance in the original state; the abscissa is the strain rate of the flexible film of the three-dimensional flexible substrate (1), and a linear regression curve is drawn according to the ordinate and the abscissa. By calculating the slope of the linear regression curve, the sensitivity coefficient GF of the flexible conductive electrode pair (2) and the strain sensitive material (3) to strain can be obtained, and input into the resistance measurement external circuit (5), so as to realize the calibration of the three-dimensional flexible sensing structure to strain and the distinction of different strain directions.

10. The use according to claim 8, characterized in that The three-dimensional flexible sensing structure is used in motion monitoring, machine operation, speech recognition or rehabilitation training.

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