Multi-dimensional strain sensor and manufacturing method thereof

Abstract

The invention discloses a multi-dimensional strain sensor, and relates to the technical field of flexible sensors, the multi-dimensional strain sensor comprises a TPU substrate layer, a first TPU oriented fiber film, a TPU spacing layer, a second TPU oriented fiber film and a TPU covering layer which are sequentially attached from top to bottom, the TPU substrate layer, the TPU spacing layer and the TPU covering layer are disordered TPU films, the first TPU oriented fiber film comprises a plurality of first TPU fibers which are parallel to one another, and the second TPU oriented fiber film comprises a plurality of second TPU fibers which are parallel to one another. The second TPU oriented fiber film comprises a plurality of second TPU fibers which are parallel to one another, conductive materials are attached to the first TPU fibers and the second TPU fibers, and the first TPU fibers and the second TPU fibers are arranged in a crossed mode. The invention further discloses a manufacturing method of the multi-dimensional strain sensor. The oriented fiber film is prepared by means of two receiving plates with a height difference. The method has high sensitivity to the stretching direction, and monitoring is more accurate and reliable.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flexible sensor, in particular to a multi-dimensional strain sensor and a manufacturing method thereof. BACKGROUND

[0002] The flexible sensor has high sensitivity, multi-modal sensing ability and good biocompatibility due to the stretchable and deformable physical characteristics, can not only work stably in a complex curved surface or dynamic environment, but also can monitor multiple types of data such as pressure, strain and physiological signals in real time; at the same time, the manufacturing process has low cost and is easy to integrate, and can be widely applied to medical health, intelligent wear, robots, human-computer interaction and other fields, bringing innovative technological breakthroughs and application expansion to various industries. The expansion of application also correspondingly improves the requirements for the performance of the sensor, such as the demand for sensitivity, adhesion and multi-dimensional force sensing of medical detection equipment, artificial limbs and the like.

[0003] The current flexible sensor includes a thermoplastic polyurethane rubber (TPU) material flexible sensor, but the TPU film thereof is formed by non-directional weaving, and finally an unordered TPU film is formed. It is found through research that this type of flexible sensor lacks sensitivity to the sensing direction due to the unordered arrangement of the TPU film (sensing layer), which further affects the monitoring accuracy. Therefore, a multi-dimensional strain sensor and a manufacturing method thereof are urgently needed to solve the above technical problems. SUMMARY

[0004] The purpose of the present application is to provide a multi-dimensional strain sensor and a manufacturing method thereof to solve the problems existing in the prior art and have higher sensitivity to the stretching direction, and monitor more accurately and reliably.

[0005] To achieve the above purpose, the present application provides the following solutions:

[0006] The present application provides a multi-dimensional strain sensor, which comprises a TPU base layer, a TPU spacing layer, a TPU cover layer, a first TPU directional fiber film and a second TPU directional fiber film. The TPU base layer, the TPU spacing layer and the TPU cover layer are all unordered TPU films. The first TPU directional fiber film comprises a plurality of first TPU fibers parallel to each other. The second TPU directional fiber film comprises a plurality of second TPU fibers parallel to each other. The first TPU fibers and the second TPU fibers are both attached with conductive materials. The TPU base layer, the first TPU directional fiber film, the TPU spacing layer, the second TPU directional fiber film and the TPU cover layer are sequentially attached from bottom to top, and the first TPU fibers and the second TPU fibers are crosswise arranged.

[0007] In some embodiments, the first TPU fibers are orthogonal to the second TPU fibers.

[0008] In some embodiments, the first TPU oriented fiber film and the second TPU oriented fiber film are both in strip shape, the areas of the TPU base layer, the TPU spacer layer and the TPU cover layer are consistent, and the areas of the first TPU oriented fiber film and the second TPU oriented fiber film are both smaller than the area of the TPU base layer.

[0009] The application also provides a manufacturing method of a multi-dimensional strain sensor, which is implemented by a feeding device, a collecting device and a control device, wherein the collecting device comprises two receiving plates which are placed side by side and have a height difference, and the feeding device is located above the collecting device, and the method comprises the following steps:

[0010] Step one, TPU particles are dissolved in a mixed solution of tetrahydrofuran and dimethylformamide to prepare a TPU electrospinning solution with a specific mass fraction, and the TPU electrospinning solution is electrospun into fibers by using an electrospinning technology to form a TPU base layer;

[0011] Step two, a positive electrode is connected with a metal nozzle of the feeding device, conductive paper is laid on the two receiving plates, a negative electrode is connected with the conductive paper of the two receiving plates, the control device is operated to make the feeding device electrospun above the two receiving plates to form a flexible TPU film, and the flexible TPU film is dried and cut, then immersed in a carbon nanotube dispersion liquid and ultrasonically treated, and after immersion and drying, a TPU oriented fiber film is obtained;

[0012] Step three, a first TPU oriented fiber film is attached to the TPU base layer, metal wires are fixed on both ends of the first TPU oriented fiber film, the first TPU oriented fiber film and the TPU base layer are placed on the receiving plate, the TPU electrospinning solution is electrospun into fibers and covered on the first TPU oriented fiber film by using an electrospinning technology to form a TPU spacer layer, a second TPU oriented fiber film is attached to the TPU spacer layer and the second TPU fibers are perpendicular to the first TPU fibers, metal wires are fixed on both ends of the second TPU oriented fiber film, and the TPU base layer, the first TPU oriented fiber film, the TPU spacer layer and the second TPU oriented fiber film are placed on the receiving plate, the TPU electrospinning solution is electrospun into fibers and covered on the second TPU oriented fiber film by using an electrospinning technology to form a TPU cover layer;

[0013] Step four, the TPU cover layer is bonded with the TPU base layer, and the metal wires are led out, and the periphery of the TPU cover layer and the TPU base layer is electrospun by using the TPU electrospinning solution to complete the packaging.

[0014] In some embodiments, the feeding device further comprises a three-axis motion platform, the feeding device comprises a micro pump controller, a micro pump actuator, a syringe piston barrel and a syringe needle, the syringe needle is a metal nozzle, the feeding device is fixedly arranged on the three-axis motion platform, in step one, the syringe piston barrel containing the TPU electrospinning solution is hung on the Z-axis of the three-axis motion platform during the electrospinning process, a 22G syringe needle is arranged on the syringe, a receiving plate is arranged directly below the syringe needle, the receiving plate is wrapped with aluminum foil paper, the distance between the syringe needle and the aluminum foil paper below is adjusted, the power voltage is adjusted to meet the conditions for electrospinning to occur, the positive electrode of the power supply is connected to the metal part of the syringe needle, and the negative electrode is connected to the aluminum foil paper, so that a high-voltage electric field is formed between the syringe needle and the aluminum foil paper, under the joint action of the thrust of the micro pump actuator and the electrostatic field force, the deposition of nanofibers is realized, and a dense and continuous TPU film is formed on the surface of the aluminum foil paper as a TPU base layer.

[0015] In some embodiments, the flow rate of the TPU electrospinning solution sprayed by the syringe needle is 1 ml / h, the spinning time is 2 h, and the TPU base layer and the TPU cover layer can be thickened by prolonging the spinning time or spinning multiple times.

[0016] In some embodiments, the horizontal distance between the two receiving plates in step two is 4-8 cm, the angle between the line connecting the two receiving plates and the horizontal plane is 15-20°, and the syringe needle is located above the central gap between the two receiving plates.

[0017] In some embodiments, in step two, the flexible TPU film and the conductive paper are placed in an oven at 30 DEG C for 6 h, and are cut into strips, carbon nanotubes are weighed and placed in anhydrous ethanol solution to configure a carbon nanotube dispersion liquid, the strip-shaped flexible TPU film is immersed in the carbon nanotube dispersion liquid and ultrasonically treated for 15 minutes, and is immersed at room temperature for 48 h, so that the carbon nanotubes are attached to the surface of the flexible TPU film, and then the immersed flexible TPU film is placed in an oven at 30 DEG C for 4 h to obtain a dried TPU oriented fiber film.

[0018] In some embodiments, the metal wires are fixedly attached to the first TPU oriented fiber film and the second TPU oriented fiber film by conductive adhesive tape.

[0019] In some embodiments, the collecting device comprises a receiving plate and a lifting frame, and the receiving plate is fixedly arranged on the top of the lifting frame.

[0020] The present application has the following technical effects compared with the prior art:

[0021] The multi-dimensional strain sensor of the present application will cause deformation of the two sensing units when the sensor is subjected to in-plane force, thereby changing the internal conductive path and leading to a change in resistance. Since the first TPU fiber and the second TPU fiber are placed in cross, both can detect the force on the X-axis and Y-axis. The directional structure of the fiber arrangement enables the sensing unit of the sensor to exhibit a high degree of difference in response to the direction of the tensile force. The directional arrangement of the fiber structure makes the internal contact points of the fiber change more complex and diversified when subjected to tensile force. When the direction of the tensile force is different, the degree of change of the contact points between the fibers also changes accordingly, resulting in a difference in response to the tensile force. This difference is the directional selectivity of the mechanical response of the directional fiber sensing unit.

[0022] On the other hand, the change in the conductive material contact path is more obvious. Due to the directional arrangement of the fiber structure, the distribution and connection mode of the conductive material between the directional fibers change greatly compared to the disordered structure: the distribution of the conductive material inside the fiber is more uniform and forms a continuous conductive network, enhancing the conductivity and sensitivity of the sensor. When subjected to tensile force in different directions, the relative displacement and deformation between the fibers are more orderly and obvious, the internal interference is significantly reduced, and the distribution of the conductive material and the change in the conductive path are more reliable and stable, thereby improving the stability and reliability of the sensor.

[0023] Moreover, during the monitoring of strain and force, due to the overlapping of the upper and lower layers of the X-axis sensing unit and the Y-axis sensing unit (the first TPU directional fiber film and the second TPU directional fiber film) of the sensor in space, the overlapping part is separated by the intermediate isolation layer (TPU spacer), thereby forming a parallel plate capacitor structure; the component of the force in space on the Z-axis will change the distance between the upper and lower layers, thereby causing a change in the capacitance value. By monitoring the change in the capacitance value, the sensor can accurately monitor the force in the Z-axis direction. The Z-axis force monitoring function based on the capacitance principle, combined with the in-plane strain monitoring function, enables the directional fiber flexible film strain sensor to monitor the strain and force in three-dimensional space simultaneously. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0025] Figure 1 The preparation schematic diagram of the TPU directional fiber film in some embodiments of the present application;

[0026] Figure 2 Structure comparison chart of non-oriented fiber film and oriented fiber film in some embodiments of the present application;

[0027] Figure 3 Mechanical property comparison chart of non-oriented fiber film and oriented fiber film in some embodiments of the present application;

[0028] Figure 4 Exploded view of multi-dimensional strain sensor in some embodiments of the present application;

[0029] Figure 5 Signal chart of multi-dimensional strain sensor applied to ankle varus monitoring in some embodiments of the present application.

[0030] In the figure: 101-TPU base layer; 102-TPU spacer layer; 103-TPU cover layer; 201-first TPU oriented fiber film; 202-second TPU oriented fiber film; 1-micro pump controller; 2-syringe piston barrel; 3-syringe needle; 4-computer control system; 5-elevator; 6-receiving plate. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0032] The purpose of the present application is to provide a multi-dimensional strain sensor and a manufacturing method thereof, to solve the problems existing in the prior art, and to have higher sensitivity in the stretching direction and more accurate and reliable monitoring.

[0033] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] Embodiment one

[0035] As Figures 1-5As shown, the application provides a multi-dimensional strain sensor, comprising a TPU base layer 101, a TPU spacer layer 102, a TPU cover layer 103, a first TPU oriented fiber film 201 and a second TPU oriented fiber film 202, the TPU base layer 101, the TPU spacer layer 102 and the TPU cover layer 103 are all disordered TPU films, the first TPU oriented fiber film 201 comprises a plurality of first TPU fibers parallel to each other, the second TPU oriented fiber film 202 comprises a plurality of second TPU fibers parallel to each other, and the first TPU fibers and the second TPU fibers are both attached with conductive material, the TPU base layer 101, the first TPU oriented fiber film 201, the TPU spacer layer 102, the second TPU oriented fiber film 202 and the TPU cover layer 103 are sequentially attached from bottom to top, and the first TPU fibers and the second TPU fibers are cross arranged.

[0036] The multi-dimensional strain sensor of the embodiment will cause deformation of the two sensing units when the sensor is subjected to in-plane force, thereby changing the internal conductive path and causing resistance change. Since the first TPU fibers and the second TPU fibers are cross arranged, they can detect the force components on the X axis and the Y axis. The directional arrangement of the fibers can make the sensing units of the sensor show high difference in response to the direction of the tensile force. The directional arrangement of the fiber structure makes the internal contact points of the fibers change more complex and diversified when subjected to tensile force. When the tensile direction is different, the degree of change of the contact points between the fibers will also change accordingly, thereby causing the difference in response to the tensile force. This difference is the direction selectivity of the mechanical response of the directional fiber sensing unit.

[0037] On the other hand, the change of the conductive material contact path is more obvious. Due to the directional arrangement of the fiber structure, compared with the disordered structure, the distribution and connection mode of the conductive material between the directional fibers change greatly: the distribution of the conductive material inside the fiber is more uniform and forms a continuous conductive network, enhancing the conductivity and sensitivity of the sensor. When subjected to tensile force in different directions, the relative displacement and deformation between the fibers are more orderly and obvious, the internal interference is significantly reduced, and the distribution of the conductive material and the change of the conductive path are more reliable and stable, thereby improving the stability and reliability of the sensor.

[0038] Moreover, in the process of strain and force monitoring, due to the upper and lower two-layer structure of the X-axis sensing unit and the Y-axis sensing unit (the first TPU oriented fiber film 201 and the second TPU oriented fiber film 202) of the sensor, there is an overlapping part in space, which is separated by the intermediate isolation layer (TPU spacing layer 102), thereby forming a parallel plate capacitor structure; the component of the force in space on the Z-axis on the sensor will change the distance between the upper and lower two layers, thereby causing a change in the capacitance value. By monitoring the change of the capacitance value, the sensor can realize accurate monitoring of the force in the Z-axis direction. Based on the Z-axis force monitoring function of the capacitor principle, in combination with the in-plane strain monitoring function, the oriented fiber flexible film strain sensor can monitor the strain and force in three-dimensional space at the same time, and is suitable for Figure 5 The ankle joint movement signal monitoring and more complex mechanical environment, has good practical prospect.

[0039] Moreover, the TPU film has high elasticity, corrosion resistance and strong wear resistance, and the structure and performance can remain stable under large tensile or compressive deformation of the sensor. The TPU material is suitable for making outdoor equipment and sports equipment. The oriented fiber flexible film structure and material characteristics provided by the application can be applied to clothes to realize limb movement monitoring and thus analyze dynamic stress of the limbs.

[0040] In some embodiments, the first TPU fiber and the second TPU fiber are orthogonally arranged. The orthogonal arrangement makes the mechanical responses of the X-axis and Y-axis direction sensing units (the first TPU oriented fiber film 201 and the second TPU oriented fiber film 202) not interfere with each other, and can independently capture the tensile force or strain along the X-axis and Y-axis directions. When the sensor receives a diagonal force, the two orthogonal groups of fibers can clearly distinguish the force components in the X-axis and Y-axis directions, accurately analyze the mechanical parameters in the two directions through the difference in resistance change, and avoid signal coupling and complex calculation problems that may occur in non-orthogonal arrangement. Under the orthogonal arrangement, the resistance change of the X-axis and Y-axis has a more explicit linear relationship (or a predictable functional relationship) with the strain in the corresponding direction, without the need for complex algorithms for direction decoupling. Compared with non-orthogonal intersection (such as 60°, 45°, etc.), the signal mapping relationship of the orthogonal structure is simpler, which facilitates the rapid calculation of the mechanical parameters in the two directions, and improves the real-time performance and practicality of the sensor.

[0041] In some embodiments, the first TPU oriented fiber film 201 and the second TPU oriented fiber film 202 are both in the shape of a strip, the areas of the TPU base layer 101, the TPU spacer layer 102 and the TPU cover layer 103 are consistent, the areas of the first TPU oriented fiber film 201 and the second TPU oriented fiber film 202 are both smaller than the area of the TPU base layer 101, the first TPU oriented fiber film 201 is placed in the center of the TPU base layer 101, and the second TPU oriented fiber film 202 is placed in the center of the TPU spacer layer 102. The edges of the oriented fiber film in the shape of a strip and with a smaller area can be completely wrapped by the base layer, the spacer layer and the cover layer with a larger area, avoiding the interference of additional deformation of the edges of the sensor caused by external force (such as shear force, local stress concentration when bending) on the sensing unit. The oriented fiber film is only stressed in the middle effective area, ensuring that the resistance change and the capacitance change are only caused by the force or strain in the target direction (X, Y and Z axes), reducing the stray signals in the non-target direction and improving the accuracy of the monitoring data.

[0042] Embodiment two

[0043] The embodiment also provides a manufacturing method of a multi-dimensional strain sensor, which is implemented by a feeding device, a collecting device and a control device (the control device adopts a computer control system 4), wherein the collecting device includes two receiving plates 6 which are placed side by side and have a height difference, the feeding device is located above the collecting device, and the method includes the following steps:

[0044] Step one, dissolve TPU particles in a mixed solution of tetrahydrofuran and dimethylformamide to prepare a TPU electrospinning solution with a specific mass fraction, and use electrospinning technology to electrospin the TPU electrospinning solution into a filament to form a TPU base layer 101;

[0045] Step two, connect the positive electrode to the metal nozzle of the feeding device, lay conductive paper on the two receiving plates 6, connect the negative electrode to the conductive paper of the two receiving plates 6, and operate the control device to make the feeding device electrospin above the two receiving plates 6 to form a flexible TPU film, then immerse the flexible TPU film in a carbon nanotube dispersion liquid after drying and cutting, and perform ultrasonic treatment, and obtain a TPU oriented fiber film after immersion, drying and cutting;

[0046] Step three, the first TPU oriented fiber film 201 is attached to the TPU base layer 101, and metal wires are fixed at both ends of the first TPU oriented fiber film 201, the first TPU oriented fiber film 201 and the TPU base layer 101 are placed on the receiving plate 6, which can be directly placed and adhered and fixed by using the self-adhesion of the TPU film, and then the TPU electrospinning solution is electrospun into a silk and covered on the first TPU oriented fiber film 201 by using the electrospinning technology to form a TPU spacing layer 102, the second TPU oriented fiber film 202 is attached to the TPU spacing layer 102 and the second TPU fiber is perpendicular to the first TPU fiber, and metal wires are fixed at both ends of the second TPU oriented fiber film 202, the TPU base layer 101, the first TPU oriented fiber film 201, the TPU spacing layer 102 and the second TPU oriented fiber film 202 are placed on the receiving plate 6, and the TPU electrospinning solution is electrospun into a silk and covered on the second TPU oriented fiber film 202 by using the electrospinning technology to form a TPU covering layer 103;

[0047] Step four, the TPU covering layer 103 is adhered to the TPU base layer 101, and the metal wires are led out, and the TPU electrospinning solution is used to electrospun the outer periphery of the TPU covering layer 103 and the TPU base layer 101 to complete the packaging.

[0048] In step two, because there is a certain distance between the two receiving plates 6 in the horizontal direction, the TPU fibers sprayed by the metal spray head will swing back and forth on the two receiving plates 6, and the receiving plates 6 have a height difference, so that the fibers are arranged in a specific direction (parallel to the connecting line of the two plates) under the joint action of the electrostatic field force and the potential difference of the receiving plate 6, realizing the directional growth of the TPU fibers, and finally the film formed between the two receiving plates 6 is a flexible TPU oriented fiber film; subsequent immersion of carbon nanotubes and ultrasonic treatment can make the conductive material uniformly adhere to the surface and gap of the oriented fibers to form a continuous and direction-specific conductive network.

[0049] Further specifically, the preparation method of the TPU electrospinning solution is as follows: first, 2g of TPU particles is weighed, and then the particles are immediately put into a 10ml composite solution of tetrahydrofuran (THF) and dimethylformamide (DMF) in a ratio of 3:2, and stirred at a speed of 300rpm for 4h to make the TPU particles completely and uniformly dissolved, and the spinning solution of the TPU base layer 101, the TPU spacing layer 102, the TPU covering layer 103, the first TPU oriented fiber film 201 and the second TPU oriented fiber film 202 all adopt the above ratio.

[0050] In some embodiments, a three-axis motion platform is further included, and the feeding device includes a micro pump controller 1, a micro pump actuator, a syringe piston barrel 2, and a syringe needle 3 which is a metal nozzle. The feeding device is fixedly arranged on the three-axis motion platform. In step one, the syringe piston barrel 2 containing the TPU electrospinning solution is hung on the Z-axis of the three-axis motion platform during the electrospinning process. The 22G syringe needle 3 is arranged on the syringe. The receiving plate 6 is arranged directly below the syringe needle 3, and the aluminum foil paper is wrapped on the receiving plate 6. The distance between the syringe needle 3 and the aluminum foil paper below is adjusted, the power voltage is adjusted, and the conditions for electrospinning are met. The positive electrode of the power supply is connected to the metal part of the syringe needle 3, and the negative electrode is connected to the aluminum foil paper, so as to form a high-voltage electric field between the syringe needle 3 and the aluminum foil paper. Under the combined action of the thrust of the micro pump actuator and the electrostatic field force, the deposition of nanofibers is realized, and a dense and continuous TPU film is formed on the surface of the aluminum foil paper as a TPU base layer 101. The TPU electrospinning solution is used throughout the preparation of the base layer, and the materials of the subsequent TPU spacer layer 102 and TPU cover layer 103 are the same, which can realize the physical fusion (not just mechanical adhesion) between the layers through electrospinning, enhance the interlayer bonding force, and reduce the risk of layering of the sensor in repeated deformation.

[0051] In some embodiments, the flow rate of the TPU electrospinning solution sprayed by the syringe needle 3 is 1 ml / h, the spinning time is 2 h, and the TPU base layer 101 and the TPU cover layer 103 can be thickened by extending the spinning time or spinning multiple times. Specifically, three times of spinning can be performed on the same receiving plate 6, and three times of spinning can obtain a thicker non-oriented TPU base layer 101. The thicker non-oriented TPU base layer 101 (disordered fiber interweaving structure) can provide stronger mechanical support and has flexibility and tear resistance. As the bottom structure of the sensor, it can effectively bear the weight of the functional layers such as the oriented fiber film and the spacer layer above, reduce the interference of its own deformation on the sensing unit when the sensor is subjected to stretching, bending and other deformations, and ensure the stability of the overall structure.

[0052] In some embodiments, the horizontal distance between the two receiving plates 6 in step two is 4-8 cm, preferably 5 cm, and the angle between the line connecting the two receiving plates 6 and the horizontal plane is 15-20°, preferably 15°. The specific horizontal distance and the angle between the line and the horizontal plane can be flexibly adjusted as needed, and the needle 3 of the syringe is located above the center of the gap between the two receiving plates 6. The 5 cm spacing provides a suitable space for the directional stretching of the fibers under the action of the electrostatic field force and the potential difference between the receiving plates 6. Too small a spacing can cause the fibers to squeeze and entangle each other when deposited, destroying the orientation; too large a spacing can weaken the electric field gradient between the two plates, reducing the driving force for the fibers to arrange along the line direction. The 5 cm distance can ensure that the fibers are fully stretched during flight and deposited in a directional manner along the line connecting the two plates, forming first and second TPU fibers with high parallelism. The slight inclination of the line to the horizontal plane, combined with the height difference between the two plates, can assist in fiber orientation through the gravitational component. When the fibers move towards the receiving plates 6 under the dominant electrostatic field force, a component along the line direction will be generated due to the inclination angle, further guiding the fibers to arrange along the target direction (the line connecting the two plates), reducing the proportion of disordered fibers, and improving the parallelism of the oriented fibers, thereby enhancing the response specificity of the sensor to specific directional forces in subsequent sensing

[0053] In some embodiments, the TPU oriented fiber film in step two also uses a flow rate of 1 ml / h, and the flexible TPU film and the conductive paper are placed together in an oven at 30°C for 6 h, and are cut into strips. Carbon nanotubes are weighed and placed in anhydrous ethanol solution to form a carbon nanotube dispersion. The flexible TPU film is immersed in the carbon nanotube dispersion and ultrasonically treated for 15 minutes, and then is immersed at room temperature for 48 h to allow the carbon nanotubes to adhere to the surface of the flexible TPU film. The immersed flexible TPU film is then placed in an oven at 30°C for 4 h to obtain a dried TPU oriented fiber film. The size of the flexible TPU film after cutting is about 1 cm x 5 cm, and the dispersion of the carbon nanotubes is prepared by weighing 0.6 g of carbon nanotubes and placing them in 30 ml of anhydrous ethanol solution.

[0054] In some embodiments, the metal wires are fixed by conductive tape on both the first TPU oriented fiber film 201 and the second TPU oriented fiber film 202. Specifically, the metal wires are placed at the ends of the first TPU oriented fiber film 201 and the second TPU oriented fiber film 202, and the connection is fixed with conductive tape, and then the spinning of the other layers in the middle is performed. After the overall packaging of the sensor is completed, the junction between the wires and the sensor is reinforced again with conductive tape.

[0055] In some embodiments, the collecting device comprises a receiving plate 6 and a lifting frame, the receiving plate 6 is fixedly arranged on the top of the lifting frame, and the specific lifting frame can comprise a motor and a screw elevator 5. The screw elevator 5 realizes lifting through screw pair transmission, has extremely high displacement precision (usually up to millimeter or even micron level), cooperates with the precise control of the motor (such as the angle subdivision can be realized by a stepping motor), can accurately adjust the height of the receiving plate 6, can accurately control the distance between the receiving plate 6 and the needle 3 of the syringe (a key parameter of spinning), ensures the stability of the high-voltage electric field strength, avoids the distance fluctuation to cause the uneven fiber diameter and deposition density, and guarantees the uniformity and consistency of the TPU base layer 101, the spacing layer and the like structure.

[0056] The principles and implementation manners of the present application are described by using specific examples in the present application, and the above embodiment description is only used to help understand the method of the present application and the core idea thereof; meanwhile, for the person skilled in the art, according to the idea of the present application, the specific implementation manner and application range will be changed. In conclusion, the content of the present description should not be understood as the limitation of the present application.

Claims

1. A multidimensional strain sensor, characterized in that: The device includes a TPU base layer, a TPU spacer layer, a TPU cover layer, a first TPU oriented fiber film, and a second TPU oriented fiber film. The TPU base layer, the TPU spacer layer, and the TPU cover layer are all disordered TPU films. The first TPU oriented fiber film includes multiple parallel first TPU fibers, and the second TPU oriented fiber film includes multiple parallel second TPU fibers. Both the first and second TPU fibers are coated with conductive material. The TPU base layer, the first TPU oriented fiber film, the TPU spacer layer, the second TPU oriented fiber film, and the TPU cover layer are sequentially bonded from bottom to top, and the first and second TPU fibers are arranged intersectingly.

2. The multidimensional strain sensor according to claim 1, characterized in that: The first TPU fiber and the second TPU fiber are orthogonally arranged.

3. The multidimensional strain sensor according to claim 1, characterized in that: Both the first TPU oriented fiber film and the second TPU oriented fiber film are strip-shaped. The TPU base layer, the TPU spacer layer, and the TPU cover layer have the same area. The areas of the first TPU oriented fiber film and the second TPU oriented fiber film are both smaller than the area of ​​the TPU base layer.

4. A method for manufacturing a multidimensional strain sensor, characterized in that: The process is implemented by a feeding device, a collecting device, and a control device. The collecting device includes two receiving plates placed side-by-side with a height difference. The feeding device is located above the collecting device. The process includes the following steps: Step 1: Dissolve TPU particles in a mixed solution of tetrahydrofuran and dimethylformamide to prepare a TPU electrospinning solution with a specific mass fraction. Use electrospinning technology to electrospin the TPU electrospinning solution into filaments to form a TPU base layer. Step 2: Connect the positive electrode to the metal nozzle of the feeding device, lay conductive paper on the two receiving plates, connect the negative electrode to the conductive paper on the two receiving plates, operate the control device to make the feeding device perform electrospinning above the two receiving plates to form a flexible TPU film, dry the flexible TPU film, cut it, immerse it in carbon nanotube dispersion and ultrasonically treat it, and after impregnation and drying, obtain a TPU oriented fiber film. Step 3: Attach the first TPU oriented fiber film to the TPU substrate layer and fix metal wires to both ends of the first TPU oriented fiber film. Place the first TPU oriented fiber film and the TPU substrate layer on the receiving plate. Electrospinning technology is used to electrospin the TPU electrospinning solution into filaments and cover the first TPU oriented fiber film to form a TPU spacer layer. Attach the second TPU oriented fiber film to the TPU spacer layer with the second TPU fibers perpendicular to the first TPU fibers. Fix metal wires to both ends of the second TPU oriented fiber film. Place the TPU substrate layer, the first TPU oriented fiber film, the TPU spacer layer, and the second TPU oriented fiber film on the receiving plate. Electrospinning technology is used to electrospin the TPU electrospinning solution into filaments and cover the second TPU oriented fiber film to form a TPU covering layer. Step four: Bond the TPU capping layer to the TPU base layer and lead out the metal wires. Use TPU electrospinning solution to electrospin the outer periphery of the TPU capping layer and the TPU base layer to complete the encapsulation.

5. The method for manufacturing a multidimensional strain sensor according to claim 4, characterized in that: It also includes a three-axis motion platform. The feeding device includes a micro-pump controller, a micro-pump actuator, a syringe piston cylinder, and a syringe needle. The syringe needle is a metal nozzle. The feeding device is fixedly installed on the three-axis motion platform. In step one, during the electrospinning process, a syringe piston cylinder containing TPU electrospinning solution is suspended on the Z-axis of the three-axis motion platform. A 22G syringe needle is mounted on the syringe. A receiving plate is located directly below the syringe needle, and aluminum foil is wrapped on the receiving plate. The distance between the syringe needle and the aluminum foil is adjusted, and the power supply voltage is adjusted to meet the conditions for electrospinning. The positive terminal of the power supply is connected to the metal part of the syringe needle, and the negative terminal is connected to the aluminum foil, thereby forming a high-voltage electric field between the syringe needle and the aluminum foil. Under the combined action of the thrust of the micro-pump actuator and the electrostatic field force, nanofibers are deposited, resulting in a dense and continuous TPU film on the surface of the aluminum foil, which serves as the TPU base layer.

6. The method for manufacturing a multidimensional strain sensor according to claim 5, characterized in that: The TPU electrospinning solution ejected from the syringe needle has a flow rate of 1 ml / h and a spinning time of 2 h. The thickness of the TPU base layer and the TPU cover layer can be increased by extending the spinning time or spinning multiple times.

7. The method for manufacturing a multidimensional strain sensor according to claim 5, characterized in that: In step two, the horizontal distance between the two receiving plates is 4-8 cm, and the angle between the line connecting the two receiving plates and the horizontal plane is 15-20°. The syringe needle is positioned above the center of the gap between the two receiving plates.

8. The method for manufacturing a multidimensional strain sensor according to claim 4, characterized in that: In step two, the flexible TPU film and conductive paper are baked together in an oven at 30°C for 6 hours and then cut into strips. Carbon nanotubes are weighed and placed in anhydrous ethanol solution to prepare a carbon nanotube dispersion. The strip-shaped flexible TPU film is immersed in the carbon nanotube dispersion and ultrasonically treated for 15 minutes. It is then soaked at room temperature for 48 hours to allow the carbon nanotubes to adhere to the surface of the flexible TPU film. Finally, the soaked flexible TPU film is placed in an oven at 30°C for 4 hours to obtain a dry TPU oriented fiber film.

9. The method for manufacturing a multidimensional strain sensor according to claim 4, characterized in that: The metal wires are fixed to the first TPU oriented fiber film and the second TPU oriented fiber film by conductive adhesive tape.

10. The method for manufacturing a multidimensional strain sensor according to claim 4, characterized in that: The collecting device includes a receiving plate and a lifting frame, with the receiving plate fixedly mounted on the top of the lifting frame.

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