An insole system based on an integrated flexible pressure sensor

Abstract

The application belongs to the field of intelligent wear, and particularly relates to a shoe-pad system based on integrated flexible pressure sensors for monitoring foot pressure distribution. The application provides a shoe-pad system based on integrated flexible pressure sensors, which comprises a smart shoe-pad, a signal acquisition and processing system and PC end software. The smart shoe-pad comprises a shoe-shaped flexible circuit board embedded with multiple integrated flexible pressure sensors and a shoe-shaped protective pad. The integrated flexible pressure sensor comprises a dielectric layer and flexible electrodes respectively bonded on the upper surface and the lower surface of the dielectric layer. The flexible electrode is a polyimide conductive film, and the dielectric layer is a polyimide ionic gel fiber. The shoe-pad system based on integrated flexible pressure sensors can be used to detect foot pressure distribution, has the characteristics of a capacitive measurement mechanism, and has the characteristics of low cost, wide measurement range and high sensitivity.

Description

Technical Field

[0001] This invention relates to the field of smart wearables, specifically to an insole system based on an integrated flexible pressure sensor for monitoring foot pressure distribution. Background Technology

[0002] The foot is the only part of the human body that comes into contact with the ground during normal activities. As physiological activities vary, the pressure felt by different parts of the foot also differs. Therefore, plantar pressure is a crucial characteristic quantity in daily life. Gait analysis generally refers to the study of human movement, revealing changes in gait patterns when human function is abnormal by studying the laws of human movement. The acquisition and detection of plantar pressure signals is of great significance for analyzing different gait characteristics, movement states, and physiological parameters of the human body.

[0003] Existing plantar pressure measurement systems are mainly divided into three categories: force plates and platforms; plantar pressure imaging technology; and force-measuring shoes and insoles. Force plates and platforms typically consist of flat, rigid pressure sensor arrays, primarily assessing static or dynamic balance based on pressure imprints and center of gravity, but are generally limited to laboratory use. Plantar pressure imaging technology can acquire information about the foot structure and pressure distribution, but its testing process is complex and costly. Force-measuring shoes and insoles often integrate flexible sensing units into the insole, with the measurement surface being the contact surface between the foot and the shoe sole. Because their testing process is not limited by time or location, their flexibility makes them the most advanced technology for plantar pressure measurement. However, these systems suffer from low measurement repeatability, poor stability, unstable signal reception, and high cost. Summary of the Invention

[0004] To address the aforementioned shortcomings, this invention provides an insole system based on an integrated flexible pressure sensor. This system collects human pressure information from the foot to analyze the wearer's physical condition. It features a capacitive measurement mechanism and is characterized by low cost, wide measurement range, and high sensitivity. Furthermore, it is unaffected by external environments, the range of human movement, or differences in foot structure, allowing for the collection of foot movement signals anytime, anywhere. Additionally, this insole boasts a long lifespan, stable acquisition frequency, and high transmission efficiency. It exhibits excellent measurement repeatability and stability.

[0005] The technical solution of this invention:

[0006] The first technical problem to be solved by the present invention is to provide an insole system based on an integrated flexible pressure sensor, including a smart insole, a signal acquisition and processing system, and PC software; the smart insole includes: a shoe-shaped flexible circuit board embedded with multiple integrated flexible pressure sensors and a shoe-shaped protective pad, wherein the integrated flexible pressure sensor includes a dielectric layer and flexible electrodes respectively bonded to the upper and lower surfaces of the dielectric layer, the flexible electrodes are polyimide conductive films, and the dielectric layer is polyimide ion gel fiber.

[0007] Furthermore, the shoe-shaped protective pad is located on the upper or lower layer of the shoe-shaped flexible circuit board embedded with multiple integrated flexible pressure sensors, near the sole of the foot; when located on the upper or lower layer, it forms a sandwich structure with the flexible circuit board, which has both protective and anti-slip functions.

[0008] Furthermore, the shoe-shaped protective pad is made of an anti-slip material, preferably a fabric or a flexible polymer material; the flexible polymer material is selected from any one of PDMS, TPU, PVP or PVA; this does not affect the stress deformation of the flexible pressure sensor.

[0009] Furthermore, the polyimide ionogel fiber is prepared by the following method: first, polyamic acid, ionic liquid, spinning aid, and solvent are mixed evenly to prepare a spinning solution; then, the spinning solution is used to prepare polyamic acid ionogel fiber by air-jet spinning; after imidization treatment, polyimide ionogel fiber is obtained; wherein, the mass of the ionic liquid accounts for 10-57% of the total solid mass, the mass of the spinning aid accounts for 18-40% of the total solid mass, the total solid mass = mass of polyamic acid + mass of ionic liquid + mass of spinning aid, and the solid content of the spinning solution is 10-30%. The solid content is the percentage of the total solid mass in the spinning solution.

[0010] Further, the ionic liquid includes one of the following: imidazole ionic liquids, piperidine ionic liquids, pyridine ionic liquids, quaternary ammonium ionic liquids, or quaternary phosphonium ionic liquids. Preferably, the ionic liquid is an imidazole ionic liquid or a quaternary phosphonium ionic liquid; more preferably, it is an imidazole ionic liquid. The ionic liquid of the present invention needs to withstand temperatures above 250°C.

[0011] Furthermore, the spinning aid includes polyacrylonitrile, polyvinylpyrrolidone, or polyethylene oxide, etc., to improve the spinnability of the spinning solution.

[0012] Furthermore, the solvent is selected from N,N-dimethylformamide (DMF), tetrahydrofuran, acetonitrile, or ethanol, etc.; the selected solvent is capable of dissolving the spinning aid and polyamic acid.

[0013] Furthermore, the integrated flexible pressure sensor is manufactured using the following method:

[0014] 1) Polyamic acid, ionic liquid, spinning aid and solvent are mixed evenly to prepare spinning solution. The spinning solution is then used to prepare polyamic acid ion gel fiber by air-jet spinning. During the air-jet spinning process, the fiber is collected using a polyamic acid conductive film as a substrate to obtain a polyamic acid conductive film carrying polyamic acid ion gel fiber.

[0015] 2) Then, two polyamic acid conductive films carrying polyamic acid ion gel fibers are stacked in the order of polyamic acid conductive film-polyamic acid ion gel fiber-polyamic acid ion gel fiber-polyamic acid conductive film, followed by compression and imidization treatment. Finally, the conductive wires are attached to the polyimide conductive film (upper and lower electrodes) to obtain the integrated flexible pressure sensor.

[0016] Furthermore, the polyamic acid conductive film is prepared by the following method: a conductive filler dispersion is thoroughly mixed with a polyamic acid solution, and then a polyamic acid conductive film is prepared by existing methods such as blade coating; the mass ratio of polyamic acid to conductive filler is 85-90:10-15%. The conductive filler includes carbon nanotubes, graphene, silver nanowires, or carbon black, etc.

[0017] Furthermore, the number of integrated flexible pressure sensors ranges from 6 to 30.

[0018] Furthermore, the integrated flexible pressure sensor is a cuboid with a length of 3mm to 10mm, a width of 3mm to 10mm, and a height of 0.05mm to 1mm; or a circle with a diameter of 3mm to 10mm. The diameter of the fiber structure in the flexible pressure sensor is generally between 800nm ​​and 2μm.

[0019] In the process of using this invention, the protective pad and the flexible circuit board embedded with multiple integrated flexible pressure sensors can be placed in the shoe along with the traditional insole; or the protective pad and the flexible circuit board embedded with multiple integrated flexible pressure sensors can be formed into an integrated smart insole by means of glue bonding or sewing.

[0020] Furthermore, the integrated smart insole is manufactured using the following method:

[0021] First, an integrated flexible pressure sensor is fabricated;

[0022] Then, multiple integrated flexible pressure sensors are embedded in appropriate positions on the shoe-shaped flexible circuit board according to monitoring needs;

[0023] Finally, protective pads are attached to the upper and lower (outer) layers of the shoe-shaped flexible circuit board, which contains an integrated flexible pressure sensor, to form an integrated smart insole.

[0024] Furthermore, the signal acquisition and processing system is used to acquire signals from the multiple integrated flexible pressure sensors, obtain multiple capacitance signals, and upload them to a network server. In this invention, the signal acquisition and processing system is connected to the sensors in the flexible circuit board of the smart insole, which is embedded with multiple integrated flexible pressure sensors, via wires. The signal acquisition and processing system is located on the outside of the shoe or on the lower leg of the person being tested, and the position of the ribbon cable connecting the signal acquisition and processing system to the insole corresponds to the arch area of ​​the insole.

[0025] Furthermore, the signal acquisition and processing system includes: a power supply for powering the device; a network unit for the processing module to acquire network signals and upload capacitance signals to a network server; a Bluetooth connection unit for connecting to the processing module via a mobile app and uploading Wi-Fi information to the processing module, enabling the processing module to acquire network signals; an acquisition unit for acquiring signals from the multiple flexible capacitive pressure-sensitive sensing units to obtain multiple capacitance signals; and a wireless transmission unit for uploading the multiple capacitance signals to a target network server via wireless communication.

[0026] Furthermore, the PC software downloads the capacitance signals uploaded to the server port to obtain foot pressure data based on the multiple capacitance signals and displays a foot pressure distribution map on the screen in real time.

[0027] Furthermore, the PC-side software includes: a data unit for downloading the multiple capacitive signals from a network server port; a processing unit for processing the multiple capacitive signals to obtain plantar force data; a storage unit for storing the multiple capacitive signals and the plantar force data; and a display unit for displaying the plantar force data on a screen using a pressure distribution map.

[0028] In this invention, existing signal acquisition and processing systems and PC software can be used.

[0029] The second technical problem to be solved by the present invention is to provide an integrated smart insole, which has a three-layer structure: an upper protective pad, a middle shoe-shaped flexible circuit board embedded with multiple integrated flexible pressure sensors, and a lower protective pad; wherein, the integrated flexible pressure sensor includes a dielectric layer and flexible electrodes respectively bonded to the upper and lower surfaces of the dielectric layer, the flexible electrodes being polyimide conductive films, and the dielectric layer being polyimide iontophoresis fibers.

[0030] Furthermore, the shoe-shaped protective pad is made of an anti-slip material, preferably a fabric or a flexible polymer material; the flexible polymer material is selected from any one of PDMS, TPU, PVP or PVA; this does not affect the stress deformation of the flexible pressure sensor.

[0031] Furthermore, the material of the flexible circuit board is selected from any one of PDMS, TPU, PVP, or PVA. The flexible circuit board of this invention uses a flexible polymer material as the matrix, and conductive metals (copper wires, silver wires, etc.) are arranged and distributed inside the polymer material. One end has reserved connection points for the positive and negative electrodes of the sensing unit, and the other end is integrated into the arch of the insole for connecting the positive and negative electrodes of the integrated flexible pressure sensor to the signal acquisition and processing module.

[0032] Furthermore, the polyimide ionogel fiber is prepared by the following method: first, polyamic acid, ionic liquid, spinning aid, and solvent are mixed evenly to prepare a spinning solution; then, the spinning solution is used to prepare polyamic acid ionogel fiber by air-jet spinning; after imidization treatment, polyimide ionogel fiber is obtained; wherein, the mass of the ionic liquid accounts for 10-57% of the total solid mass, the mass of the spinning aid accounts for 18-40% of the total solid mass, the total solid mass = mass of polyamic acid + mass of ionic liquid + mass of spinning aid, and the solid content of the spinning solution is 10-30%. The solid content is the percentage of the total solid mass in the spinning solution.

[0033] Furthermore, the number of integrated flexible pressure sensors ranges from 6 to 30.

[0034] The third technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned integrated smart insole, wherein the method is as follows:

[0035] (1) First, an integrated flexible pressure sensor is fabricated;

[0036] (2) Then embed multiple integrated flexible pressure sensors into appropriate positions on the shoe-shaped flexible circuit board according to monitoring needs;

[0037] (3) Finally, protective pads are attached to the upper and lower (outer) layers of the shoe-shaped flexible circuit board embedded with multiple integrated flexible pressure sensors to form an integrated smart insole.

[0038] Furthermore, the method for fabricating the integrated flexible pressure sensor in step (1) is as follows:

[0039] 1) Polyamic acid, ionic liquid, spinning aid and solvent are mixed evenly to prepare spinning solution. The spinning solution is then used to prepare polyamic acid ion gel fiber by air-jet spinning. During the air-jet spinning process, the fiber is collected using a polyamic acid conductive film as a substrate to obtain a polyamic acid conductive film carrying polyamic acid ion gel fiber.

[0040] 2) Then, two polyamic acid conductive films carrying polyamic acid ion gel fibers are stacked in the order of polyamic acid conductive film-polyamic acid ion gel fiber-polyamic acid ion gel fiber-polyamic acid conductive film, followed by compression and imidization treatment. Finally, the conductive wires are attached to the polyimide conductive film (upper and lower electrodes) to obtain the integrated flexible pressure sensor.

[0041] Furthermore, step (2) involves embedding multiple integrated flexible pressure sensors into suitable positions on a traditional insole according to monitoring needs by bonding the positive and negative electrodes of the integrated flexible pressure sensors to the positive and negative pins on the flexible circuit board using silver wires and conductive silver paste.

[0042] Furthermore, in step (2), the plurality of integrated flexible pressure sensors are located in at least one of the following regions of the flexible circuit board: the inner heel region, the outer heel region, the outer midfoot region, the metatarsal region, or the toe region.

[0043] Furthermore, in step (2), twenty-eight flexible pressure sensors are embedded in a shoe-shaped flexible circuit board, with four sensors distributed at the first to fourth toes, twelve sensors evenly distributed at the forefoot, four sensors distributed at the arch of the foot, and the last eight sensors distributed at the main pressure points of the heel; that is, the flexible pressure sensors are distributed at the main pressure points of the foot.

[0044] Furthermore, step (3) forms an integrated smart insole by using glue or sewing.

[0045] The beneficial effects of this invention are:

[0046] The insole system based on an integrated flexible pressure sensor provided by this invention can be used to detect the pressure distribution on the sole of the foot. It features a capacitive measurement mechanism and is characterized by low cost, wide measurement range, and high sensitivity. Furthermore, it is not limited by external environment, range of motion, or differences in foot structure, and can collect foot motion signals anytime, anywhere. The insole used also has a long service life, stable acquisition frequency, and high transmission efficiency; it exhibits good measurement repeatability and stability.

[0047] The integrated flexible sensor used in this invention also has the following advantages:

[0048] (1) The integrated flexible sensor prepared by the present invention can overcome the problems of fatigue under complex stress, interface delamination, encapsulation, and unstable sensing signal caused by the multi-layer and multi-material characteristics of other flexible sensors. The present invention proposes a fiber layered structure, characterized by the rapid evaporation of solvent during air-jet spinning to form an overlapping interface. Different functional layers of the same substrate can form an integrated sensor device with a stable welding interface.

[0049] (2) The integrated flexible sensor prepared by the present invention has excellent resistance to high and low temperatures, radiation resistance, and good mechanical properties, and can be used to address the sensor failure problem under extreme working conditions, high and low temperature shock and scenario applications.

[0050] (4) The flexible compressible multifunctional integrated micro-nanofiber sensor prepared by the present invention has the performance of being sensitive to multiple forces such as pressure, bending and stretching. The three-dimensional porous nanofiber scaffold and elastic structure provide more contact electricity for the pressure sensor and have a large deformation space and rebound performance, thereby achieving high sensitivity, short response time, wide detection range, wide temperature range and high stability sensing performance.

[0051] (5) The flexible, compressible, multifunctional integrated micro / nanofiber sensor prepared by the present invention can be applied to human health detection and detection of human movement in the full range. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of an insole system based on an integrated flexible pressure sensor according to an embodiment of the present invention, wherein: 1-integrated flexible pressure sensor, 2-flexible circuit board shaped like an insole, 3-signal acquisition and processing equipment.

[0053] Figure 2 This is a schematic diagram of the insole of the present invention, wherein: 2-1 refers to the upper protective pad (anti-slip layer), 2-2 refers to the flexible circuit board embedded with 28 integrated flexible pressure sensors, 2-3 refers to the lower protective pad (anti-slip layer), 2-4 refers to the traditional insole, and 2-5 refers to the sole.

[0054] Figure 3 This is a schematic diagram of the structure of each integrated flexible pressure sensor in the insole system based on the integrated flexible pressure sensor of the present invention.

[0055] Figure 4 This is a functional flowchart of the signal acquisition and processing system in the insole system based on the integrated flexible pressure sensor of the present invention.

[0056] Figure 5 This is a schematic diagram showing the positional distribution of the integrated flexible pressure sensor in the smart insole of the present invention.

[0057] Figure 6This is a schematic diagram of the use of the insole system based on the integrated flexible pressure sensor in an embodiment of the present invention. During use, the pressure distribution map is displayed on the PC software screen.

[0058] Figure 7 The image shown is a SEM image of the fiber structure obtained in Example 1 of this invention. Figure 7 It can be seen that the fiber structure obtained by the present invention is uniform and has high porosity.

[0059] Figure 8 This is a SEM image of the fiber-to-fiber welding point obtained in Example 1 of the present invention; (The image is derived from...) Figure 8 It can be seen that a stable integrated interface is formed between the polyimide ionogel fibers in the sensing unit prepared by the method of the present invention.

[0060] Figure 9 This is a SEM image of the fiber-electrode film welding point obtained in Example 1 of the present invention; (The image is from...) Figure 9 It can be seen that a stable integrated interface is formed between the fiber and the electrode layer.

[0061] Figure 10 This is a sensitivity performance diagram of the sensor obtained in Example 1 of the present invention; (The diagram is from...) Figure 10 It can be seen that the flexible sensor of the present invention has excellent sensitivity.

[0062] Figure 11 This is a response time signal diagram of the sensor obtained in Example 1 of the present invention; from Figure 11 It can be seen that the response speed of the flexible sensor of the present invention is higher than that of human skin.

[0063] Figure 12 This is a cyclic response stability performance diagram of the sensor obtained in Example 1 of the present invention; by Figure 12 It can be seen that the flexible sensor of the present invention has service stability under ultra-high pressure.

[0064] Figure 13 This is a schematic diagram illustrating the principle of airflow spinning in this invention.

[0065] Figure 14 Gait analysis diagrams for different foot types; by Figure 14 It can be seen that the flexible sensing insole of the present invention can monitor the gait and pressure distribution of different foot types in real time. Detailed Implementation

[0066] This invention provides an insole system based on an integrated flexible pressure sensor, including a smart insole, a signal acquisition and processing system, and PC-based software. The smart insole includes a flexible circuit board embedded with multiple integrated flexible pressure sensors and a protective pad, which can be placed on the upper and lower layers of the flexible circuit board. Each integrated flexible pressure sensor includes a dielectric layer and flexible electrodes bonded to the upper and lower surfaces of the dielectric layer, respectively. The flexible electrodes are polyimide conductive films, and the dielectric layer is polyimide iontophoresis fibers. In the sensor of this invention, the iontophoresis dielectric layer enables the sensor to obtain excellent high signals, the polyimide matrix provides excellent mechanical properties and signal stability, and the fibers and electrodes form stable welding interfaces, thereby giving the resulting three-dimensional iontophoresis fiber sensor high structural stability. Consequently, the insole made using this sensor for detecting plantar pressure distribution has a wide measurement range and high sensitivity.

[0067] In this invention, during the fabrication of a pressure sensor, ionic liquids act as functional fillers within the polymer material, achieving fiber functionalization. Polyimide serves as the structural matrix of the fiber, providing excellent mechanical properties for the three-dimensional structure, typically ranging from 2 MPa to 8 GPa. Spinning aids are used to enhance the spinnability of the ionogel, resulting in stable fiber output. In this invention, different functional fillers are added to polyamic acid to achieve various functionalization processes; conductive fillers are added as the electrode layer, and ionic liquids are added as the dielectric layer. The ultra-high porosity ionogel fibers prepared by air-jet spinning exhibit excellent structural properties. Polyimide, as a high-modulus polymer material, provides superior mechanical properties to the structure. Simultaneously, during the high-temperature imidization process of polyamic acid, structurally similar polyimide matrices may form thermally welded interfaces, resulting in excellent interfacial toughness. This allows the sensor to maintain high signal stability even under complex stress conditions.

[0068] The integrated flexible pressure sensor of the present invention can be prepared by the following method, including the following steps:

[0069] 1) Stir the ionic liquid and polyamic acid solution at room temperature for 0.5 to 1 hour to obtain an ionic liquid / polyamic acid mixture solution; the polyamic acid solution described in this invention is generally a thermoplastic polyimide precursor solution, preferably an ether anhydride type polyimide;

[0070] 2) Stir the spinning aid and solvent at room temperature for 2-5 hours to obtain a spinning aid solution;

[0071] 3) Add the spinning aid solution to the ionic liquid / polyamic acid mixed solution in step 1), and stir thoroughly at room temperature for 2-3 hours to obtain the spinning solution;

[0072] 4) The spinning solution obtained in step 3) is used to prepare ionogel fibers by air-jet spinning. During the spinning process, a polyamic acid conductive film is used as a substrate to collect the fibers, thereby obtaining a polyamic acid conductive film carrying polyamic acid ionogel fibers. The air pressure at the jet nozzle is 0.05-0.5 MPa, and the distance from the nozzle to the receiving device (receiving cage) is 10-25 cm. The air-jet spinning process is as follows: the obtained spinning solution is added to an injection pump with a needle orifice diameter of 0.05-0.4 mm and a feeding rate of 0.01-0.05 ml / min. The air pressure at the jet nozzle is 0.05-0.5 MPa, and the distance from the nozzle to the receiving device (receiving cage) is adjusted to 10-25 cm. After collecting for 0.5-1 h, the fibers are obtained. The obtained fibers are left to stand at room temperature for 1-2 h to allow the solvent to evaporate completely.

[0073] 5) Using the polyamic acid conductive membranes with polyamic acid ion gel fibers obtained in step 4), stack them in the order of polyamic acid conductive membrane-polyamic acid ion gel fiber-polyamic acid ion gel fiber-polyamic acid conductive membrane, and then perform compression and imidization treatment; finally, attach the conductive wires to the upper and lower polyimide conductive membranes to obtain an integrated polyimide-based flexible pressure sensor.

[0074] The integrated flexible pressure sensor prepared using this invention can be used to measure the pressure at various points on the sole of the foot. It is a capacitive pressure sensor that can convert changes in human body pressure into electrical signals of capacitance changes, which are used to measure the pressure exerted on the insole at various points on the sole of the foot. The flexible capacitive pressure sensor has a certain degree of flexibility and a large pressure response range and sensitivity. Through wide-range pressure sensing, it can realize functions such as accurate pressure distribution measurement and weight measurement on the sole of the foot. Through extremely sensitive pressure sensing, it can realize the function of measuring the wearer's heart rate.

[0075] In the insole of this invention, the capacitance value of the integrated flexible pressure sensor changes under stress, and the stress condition can be determined based on the change in resistance and capacitance. The signal acquisition and processing module can detect the capacitance change of the sensor in real time and obtain the capacitance signal. Then, by analyzing and processing the capacitance signal, the plantar force data can be obtained, so as to perform gait feature analysis, motion state analysis, physiological data acquisition, etc. based on the plantar force data.

[0076] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0077] Example 1

[0078] The fabrication steps of an integrated flexible pressure sensor are as follows:

[0079] I. Electrode Preparation

[0080] 1) Add 2g of carbon nanotubes to 198g of N,N-dimethylformamide solvent and sonicate for 2h; to obtain a 1wt% carbon nanotube dispersion.

[0081] 2) Take 22g of carbon nanotube dispersion and add it to 10g of polyamic acid solution, and stir magnetically for 3 hours;

[0082] 3) Apply the stirred solution to a 500-micron film using a film coating machine, and then place it in 100... o The polyamic acid conductive film was obtained by drying it in a forced-air oven at C for 1 hour and then removed for use.

[0083] II. Preparation of spinning solution:

[0084] 1) Add 0.49 g of 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid to 1.5 g of polyamic acid solution with a mass concentration of 18%, and stir at room temperature for 0.5 to 1 h to obtain a mixed solution of ionic liquid / polyamic acid solution;

[0085] 2) Add 1g of polyacrylonitrile to 9g of N,N-dimethylformamide solvent and stir at room temperature for 2-5 hours to obtain a spinning aid solution;

[0086] 3) Add 2.2g of the spinning aid solution to the mixed solution of ionic liquid / polyamic acid solution in step 1), and stir thoroughly at room temperature for 2-3 hours to obtain the spinning solution of ion gel composite material;

[0087] III. Preparation of ultra-high porosity three-dimensional polymer ionogel fibers and fabrication of flexible pressure sensors:

[0088] 1) Add the spinning solution to the micro-injection pump, with a needle orifice diameter of 0.05-0.4 mm and a solution feed rate of 0.05 ml / min;

[0089] 2) Set the air pressure of the jet nozzle to 0.05-0.5 MPa and adjust the distance from the nozzle to the receiving cage to 10-25 cm. During the spinning process, use the polyamic acid conductive film as a substrate to collect the fibers. After collecting for 0.5-1 h, a polyamic acid conductive film carrying polyamic acid ion gel fibers is obtained (a two-layer structure of three-dimensional ion gel fibers and polyamic acid conductive film).

[0090] 3) Two polyamic acid conductive films carrying polyamic acid iontophoresis fibers are stacked in the following order: polyamic acid conductive film (electrode) - polyamic acid iontophoresis fiber - polyamic acid iontophoresis fiber - polyamic acid conductive film (electrode). After pre-compression, they are placed in a muffle furnace for imidization treatment. The heating program is as follows: 80℃ for 0.5h, 100℃ for 0.5h, 150℃ for 0.5h, 200℃ for 0.5h, 250℃ for 0.5h, and 300℃ for 1h. Finally, the sample is cut into 1cm×1cm sizes, and conductive silver wires are attached to the upper and lower polyimide conductive films to obtain the polyimide-based iontophoresis fiber integrated flexible pressure sensor.

[0091] The fibers obtained in Example 1 were characterized using scanning electron microscopy, and the results are as follows: Figure 7 As shown, by Figure 7 It can be seen that the ionogel fiber obtained by this invention has an ultra-high porosity of 95%, and the fiber diameter is between 0.8 and 2 micrometers. The fiber structure was cut into samples of 0.7cm × 0.7cm × 0.9mm, and the porosity was tested and calculated using the water displacement method. Using the formula P = [(V0 - V) / V0] * 100%, V0 = 0.9 cm3, and 0.042 ml of water was displaced, the porosity P was calculated to be 95.33%. Figure 8 Figures 9 and 9 respectively show the stable fusion interfaces between dielectric layer fibers and between dielectric layer fibers and electrode layer films in the samples.

[0092] The capacitance of the flexible pressure sensor changes with pressure using a universal tensile testing machine and an LCR bridge. This reflects the sensitivity signal, response time, and cyclic stability of the fabricated flexible pressure sensor. Figure 10 , Figure 11 and Figure 12 As shown in the figure, the sensitivity can reach 158 kPa. -1 The response time is within 5ms, and it maintains high signal and structural stability under 2000kPa cyclic pressure.

[0093] Figure 13 The air-jet spinning process is shown.

[0094] IV. Preparation of Insoles:

[0095] Cut the aforementioned integrated flexible pressure sensor to a specific size (0.5cm × 0.5cm × 0.9mm), and arrange the twenty-eight sensors according to... Figure 5As shown, the sensor is soldered to the flexible circuit board using silver wires and conductive silver paste. Then, a cotton cloth layer is used as a protective pad to cover the upper and lower layers of the flexible circuit board with the integrated sensor. The integrated flexible smart insole is then fabricated by bonding or sewing to detect the pressure distribution on the sole of the foot.

[0096] The use of insoles:

[0097] Users wear athletic shoes with built-in integrated flexible smart insoles (integrated smart insole - traditional insole - sole), attach the signal acquisition and processing device to the ankle or calf, and turn on the device. At this point, the smart insole's signal acquisition and processing device is in a network connection-ready state. By collecting the target Wi-Fi username and password from the app, the device activates after 3 seconds, uploading the capacitance signal to a designated server in real time. Users can then download the capacitance signal from the server in real time via a browser client on their mobile phone or computer. The software analyzes and processes the data, and the client screen displays a real-time foot pressure distribution map.

[0098] The software interface includes the following buttons: Start button: Clicking Start will begin reading and saving the downloaded data; Pause button: Clicking Pause will stop saving the downloaded data points; Clear data button: Clicking Clear data will clear all downloaded data points, and the data points will be downloaded again from the next moment; Save data button: Clicking Save data will save all measured data to a document; Historical data button: Clicking Historical Data will open the browser in the background, and the screen will display a graph of the capacitance signal of a single sensor changing over time.

[0099] Analysis of pressure distribution maps can yield data such as total duration, total steps, average cadence, average walking speed, and total energy consumption. By analyzing different pressure distributions, data such as the test subject's foot type, walking posture, and foot pressure points can be obtained.

[0100] User 1 wears athletic shoes with built-in integrated flexible smart insoles, and fixes the signal acquisition and processing device to the ankle or calf area. The ribbon cable connecting the signal acquisition and processing device to the smart insole is positioned corresponding to the arch area of ​​the insole. The device is then powered on and connected to the network. During normal walking, the sensors in the flexible insole deform under the pressure of the human body, resulting in changes in capacitance signals. These capacitance signals are analyzed and processed to correlate with pressure distribution, such as... Figure 14 As shown, the walking process is divided into five stages: foot landing, foot lifting, foot lifting, foot landing, and foot landing. The foot pressure distribution map clearly shows that the foot pressure of the test subject is mainly concentrated on the inner side of both feet, which is identified as pigeon toeing. Through the analysis of the foot pressure distribution map, the walking posture of the test subject can be corrected in a reasonable and evidence-based manner.

[0101] User 2 puts on athletic shoes with built-in integrated flexible smart insoles, attaches the signal acquisition and processing equipment to the ankle or calf, turns on the module's power switch, and connects to the network. During normal walking, the sensing units in the flexible insole deform under the pressure of the human body, resulting in changes in capacitance signals. These capacitance signals are analyzed and processed to correlate with pressure distribution, such as... Figure 5 As shown, the walking process is divided into five stages: foot landing, foot lifting, foot lifting, foot landing, and foot landing. The foot pressure distribution map clearly shows that the foot pressure of the test subject is mainly concentrated on the outer side of both feet, which is identified as outward toeing. Through the analysis of the foot pressure distribution map, the walking posture of the test subject can be corrected in a reasonable and evidence-based manner.

[0102] Therefore, this invention, through the analysis of pressure distribution maps, can obtain data such as total duration, total steps, average cadence, average gait, and total energy consumption. By analyzing different pressure distributions, data on the subject's foot type, gait posture, and foot pressure points can be obtained. This has great application potential for health rehabilitation, foot deformity correction, and disease prediction.

[0103] Comparative Example 1

[0104] I. Preparation of spinning solution:

[0105] 1) Add 0.7 g of 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid to 1.5 g of polyamic acid solution with a mass concentration of 18%, and stir at room temperature for 0.5 to 1 h to obtain a mixed solution of ionic liquid / polyamic acid solution;

[0106] 2) Add 1g of polyacrylonitrile to 9g of N,N-dimethylformamide solvent and stir at room temperature for 2-5 hours to obtain a spinning aid solution;

[0107] 3) Add 2.2g of the spinning aid solution to the mixed solution of ionic liquid / polyamic acid solution in step 1), and stir thoroughly at room temperature for 2-3 hours to obtain the spinning solution of ion gel composite material;

[0108] II. Preparation of ultra-high porosity three-dimensional polymer ionogel fibers:

[0109] 1) Add the spinning solution to the micro-injection pump, with a needle orifice diameter of 0.05-0.4 mm and a solution feed rate of 0.05 ml / min;

[0110] 2) Set the airflow pressure at the nozzle to 0.05-0.5 MPa, and adjust the distance from the nozzle to the receiving cage to 10-25 cm;

[0111] As a result, the spinning solution failed to form a fiber structure under the limited preparation parameters; the reason was that the ionic liquid content was too high, and the spinning effect of the spinning solution could not meet the requirements of airflow spinning.

[0112] Comparative Example 2

[0113] 1) Add 0.49 g of 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid to 1.5 g of polyamic acid solution, wherein the concentration of polyamic acid solution is 18%, and stir at room temperature for 0.5 to 1 h to obtain a mixed solution of ionic liquid / polyamic acid solution;

[0114] 2) Add 1g of polyacrylonitrile to 9g of N,N-dimethylformamide solvent and stir at room temperature for 2-5 hours to obtain a spinning aid solution;

[0115] 3) Add 1.5g of the spinning aid solution to the mixed solution of ionic liquid / polyamic acid solution in step 1), and stir thoroughly at room temperature for 2-3 hours to obtain the spinning solution of ion gel composite material;

[0116] II. Preparation of ultra-high porosity three-dimensional polymer ionogel fibers:

[0117] 1) Add the spinning solution to the micro-injection pump, with a needle orifice diameter of 0.05-0.4 mm and a solution feed rate of 0.05 ml / min;

[0118] 2) Set the airflow pressure at the nozzle to 0.05-0.5 MPa, and adjust the distance from the nozzle to the receiving cage to 10-25 cm;

[0119] As a result, the spinning solution failed to form a fiber structure under the limited preparation parameters. The reason was that too little spinning aid was added, and the spinning solution had poor spinning effect under the influence of high ionic liquid content, and could not form a stable fiber structure.

Claims

1. A shoe insole system based on an integrated flexible pressure sensor, characterized in that, The insole system includes a smart insole, a signal acquisition and processing system, and PC software. The smart insole includes a shoe-shaped flexible circuit board embedded with multiple integrated flexible pressure sensors and a shoe-shaped protective pad. The integrated flexible pressure sensor includes a dielectric layer and flexible electrodes bonded to the upper and lower surfaces of the dielectric layer, respectively. The flexible electrodes are polyimide conductive films, and the dielectric layer is polyimide ionomer fiber. The shoe-shaped protective pad is located on the upper or lower layers of the shoe-shaped flexible circuit board embedded with multiple integrated flexible pressure sensors, near the sole of the foot. The integrated flexible pressure sensor is prepared by the following method: 1) Polyamic acid, ionic liquid, spinning aid, and solvent are mixed evenly to prepare a spinning solution, and then the spinning solution is used to obtain polyamic acid through airflow spinning. Ion gel fibers are collected during air-jet spinning using a polyamic acid conductive film as a substrate to obtain a polyamic acid conductive film carrying polyamic acid ion gel fibers; 2) Then, two polyamic acid conductive films carrying polyamic acid ion gel fibers are stacked in the order of polyamic acid conductive film-polyamic acid ion gel fiber-polyamic acid ion gel fiber-polyamic acid conductive film, and then compressed and imidized. Finally, the conductive wires are attached to the polyimide conductive film to obtain an integrated flexible pressure sensor; The polyamic acid conductive film is prepared by the following method: the conductive filler dispersion is thoroughly mixed with the polyamic acid solution, and then a polyamic acid conductive film is obtained by coating; the mass ratio of polyamic acid to conductive filler is 85-90:10-15%.

2. The insole system based on an integrated flexible pressure sensor according to claim 1, characterized in that, The shoe-shaped protective pad is made of anti-slip material.

3. The insole system based on an integrated flexible pressure sensor according to claim 2, characterized in that, The anti-slip material is fabric or flexible polymer material.

4. The insole system based on an integrated flexible pressure sensor according to claim 3, characterized in that, The flexible polymer material is selected from any one of PDMS, TPU, PVP or PVA.

5. A shoe insole system based on an integrated flexible pressure sensor according to claim 1 or 2, characterized in that, The polyimide ionogel fiber is prepared by the following method: first, polyamic acid, ionic liquid, spinning aid and solvent are mixed evenly to prepare a spinning solution, and then the spinning solution is used to prepare polyamic acid ionogel fiber by air-jet spinning. After imidization treatment, polyimide ionogel fiber is obtained; wherein, the mass of ionic liquid accounts for 10-57% of the total solid mass, the mass of spinning aid accounts for 18-40% of the total solid mass, the total solid mass = mass of polyamic acid + mass of ionic liquid + mass of spinning aid, and the solid content of the spinning solution is 10-30%.

6. The insole system based on an integrated flexible pressure sensor according to claim 1, characterized in that, The ionic liquid includes one of the following: imidazole ionic liquid, piperidine ionic liquid, pyridine ionic liquid, quaternary ammonium ionic liquid, or quaternary phosphonium ionic liquid.

7. A shoe insole system based on an integrated flexible pressure sensor according to claim 6, characterized in that, The ionic liquid is an imidazole-based ionic liquid or a quaternary phosphonium-based ionic liquid.

8. The insole system based on an integrated flexible pressure sensor according to claim 1, characterized in that, The spinning aid includes: polyacrylonitrile, polyvinylpyrrolidone, or polyethylene oxide.

9. A shoe insole system based on an integrated flexible pressure sensor according to claim 1, characterized in that, The solvent is selected from N,N-dimethylformamide, tetrahydrofuran, acetonitrile, or ethanol.

10. A shoe insole system based on an integrated flexible pressure sensor according to claim 1 or 2, characterized in that, The number of integrated flexible pressure sensors ranges from 6 to 30.

11. A shoe insole system based on an integrated flexible pressure sensor according to claim 1 or 2, characterized in that, The integrated flexible pressure sensor is a cuboid with a length of 3mm to 10mm, a width of 3mm to 10mm, and a height of 0.05mm to 1mm; or a circle with a diameter of 3mm to 10mm.

12. A shoe insole system based on an integrated flexible pressure sensor according to claim 1 or 2, characterized in that, The signal acquisition and processing system is used to acquire signals from the multiple integrated flexible pressure sensors, obtain multiple capacitance signals, and upload them to the network server; the PC software downloads the capacitance signals uploaded to the server port to obtain foot pressure data based on the multiple capacitance signals and displays a foot pressure distribution map on the screen in real time.

13. An integrated smart insole, characterized in that, The integrated smart insole has a three-layer structure: an upper protective pad, a middle shoe-shaped flexible circuit board embedded with multiple integrated flexible pressure sensors, and a lower protective pad. The integrated flexible pressure sensor includes a dielectric layer and flexible electrodes bonded to the upper and lower surfaces of the dielectric layer, respectively. The flexible electrodes are polyimide conductive films, and the dielectric layer is polyimide ionogel fiber. The integrated flexible pressure sensor is manufactured using the following method: 1) Polyamic acid, ionic liquid, spinning aid, and solvent are mixed evenly to prepare a spinning solution. The spinning solution is then used to prepare polyamic acid ion gel fibers by air-jet spinning. During the air-jet spinning process, the fibers are collected using a polyamic acid conductive film as a substrate to obtain a polyamic acid conductive film carrying polyamic acid ion gel fibers. 2) Two polyamic acid conductive films carrying polyamic acid ion gel fibers are then stacked in the order of polyamic acid conductive film-polyamic acid ion gel fiber-polyamic acid ion gel fiber-polyamic acid conductive film, followed by compression and imidization treatments. Finally, conductive wires are adhered to the polyimide conductive film to obtain an integrated flexible pressure sensor. The polyamic acid conductive film is prepared by the following method: a conductive filler dispersion is thoroughly mixed with a polyamic acid solution, and then a polyamic acid conductive film is prepared by coating. The mass ratio of polyamic acid to conductive filler is 85-90:10-15%.

14. The integrated smart insole according to claim 13, characterized in that, The preparation method is as follows: (1) First, an integrated flexible pressure sensor is fabricated; (2) Then embed multiple integrated flexible pressure sensors into appropriate positions on the shoe-shaped flexible circuit board according to monitoring needs; (3) Finally, protective pads are attached to the upper and lower layers of the shoe-shaped flexible circuit board embedded with multiple integrated flexible pressure sensors to form an integrated smart insole.

15. An integrated smart insole according to claim 14, characterized in that, In step (2), the plurality of integrated flexible pressure sensors are located in at least one of the following regions of the flexible circuit board: the inner heel region, the outer heel region, the outer midfoot region, the metatarsal region, or the toe region.

16. An integrated smart insole according to claim 14, characterized in that, In step (2), twenty-eight flexible pressure sensors are embedded in a shoe-shaped flexible circuit board, with four sensors distributed at the first to fourth toes, twelve sensors evenly distributed at the forefoot, four sensors distributed at the arch of the foot, and eight sensors distributed at the heel.

17. An integrated smart insole according to claim 14, characterized in that, Step (3) The method of forming an integrated smart insole is: to use glue or stitching.

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