Self-powered temperature-pressure decoupling intelligent insole based on pyroelectric hydrogel and preparation method thereof

Abstract

This application provides a self-driven temperature-pressure decoupled smart insole based on thermoelectric hydrogel and its preparation method, belonging to the field of flexible wearable sensing devices. It overcomes the defects of existing smart insoles, such as complex wiring, severe signal coupling, need for external power supply, and poor flexibility caused by the separate setting of temperature and pressure sensors. The smart insole adopts a layered encapsulation structure, which consists of an upper conductive layer, an upper insulating layer, a support layer, a lower insulating layer, and a lower conductive layer from top to bottom. The thermoelectric hydrogel sensing units with dual functions of temperature gradient response and pressure response are embedded in the support layer according to the pressure and temperature monitoring areas of the sole. By utilizing the different output signal types of thermoelectric hydrogel in open-circuit voltage mode and closed-circuit current mode, and through time-division switching between voltage acquisition mode and current acquisition mode, in-situ mode self-decoupling of temperature and pressure signals is achieved on the same sensing unit without the need for external decoupling algorithms.

Description

Technical Field

[0001] This application relates to the field of flexible wearable sensing device technology, and in particular to a self-driven temperature-pressure decoupled smart insole based on thermoelectric hydrogel and its preparation method. Background Technology

[0002] Plantar pressure and temperature are important physiological parameters reflecting the health status of the human foot and movement posture. Real-time monitoring of plantar pressure and temperature distribution has clear application needs in areas such as scientific sports training, early screening and warning of diabetic foot, evaluation of rehabilitation training effectiveness, and fall risk assessment in the elderly.

[0003] Currently, most smart insoles with foot sensing capabilities employ a discrete sensor solution, which uses separate pressure and temperature sensors to measure two physical quantities. For example, patent application CN218390007U discloses an insole for monitoring foot pressure and temperature, which collects foot pressure and temperature data using pressure and temperature sensors respectively. This approach suffers from the following significant problems: First, the large number of discrete sensors and their associated wiring leads to complex wiring and manufacturing difficulties; second, the high coupling between temperature and pressure signals necessitates complex blind source separation or machine learning algorithms for backend decoupling, increasing the system's computational burden and impacting real-time performance; third, traditional sensors require an external excitation power supply, resulting in high energy consumption.

[0004] Hydrogel materials based on the ion thermoelectric effect possess flexibility and stretchability matching biological tissues, and can autonomously generate thermoelectric voltage (thermovolt-ampere effect) using temperature gradients to achieve self-driven temperature sensing without external power excitation. Chinese invention patent application CN116869524A discloses a temperature sensor based on ion thermoelectric hydrogels, which measures temperature using the thermovolt-ampere effect of ions within the gel under a temperature gradient. Zhang et al. reported in ACS Applied Materials & Interfaces (2025, DOI: 10.1021 / acsami.5c00480) a thermoelectric composite material based on laser-induced graphene and ion hydrogels, exploring the integration of a flexible conductive layer with the hydrogel sensing material. However, the above sensors can only achieve single temperature measurement, or although they have some response to pressure, the temperature and pressure signals are highly coupled at the sensing material level, making it impossible to achieve independent sensing of the two signals on the same sensitive unit. The key challenge currently facing technology is how to achieve independent and self-driven sensing of temperature and pressure on a single sensitive material and systematically integrate it into insoles. Summary of the Invention

[0005] To overcome the drawbacks of existing smart insoles, such as complex wiring, severe signal coupling, need for external power supply, and poor flexibility caused by the separate placement of temperature and pressure sensors, this application proposes a self-driven temperature-pressure decoupled smart insole based on thermoelectric hydrogel and its preparation method. By utilizing the different output signal types of thermoelectric hydrogel in open-circuit voltage mode and closed-circuit current mode, and through time-division switching between voltage acquisition mode and current acquisition mode, in-situ mode self-decoupling of temperature and pressure signals is achieved on the same sensitive unit. No external decoupling algorithm is required, and temperature sensing is self-driven by the temperature gradient between human body temperature and the ambient temperature of the shoe sole, without the need for external power supply excitation.

[0006] The technical solution adopted in this application is: a self-driven temperature-pressure decoupling smart insole based on thermoelectric hydrogel. The smart insole adopts a layered encapsulation structure. The layered encapsulation structure consists of an upper conductive layer, an upper insulating layer, a support layer, a lower insulating layer, and a lower conductive layer from top to bottom. The upper insulating layer is used to achieve flexible insulating encapsulation between the upper conductive layer and the support layer, and the lower insulating layer is used to achieve flexible insulating encapsulation between the lower conductive layer and the support layer. The support layer has multiple through holes arranged according to the pressure and temperature monitoring areas of the sole. Each through hole contains a thermoelectric hydrogel sensing unit that has both temperature gradient response and pressure response functions. The upper end electrode of all thermoelectric hydrogel sensing units is led out from the upper conductive layer, and the lower end electrode of all thermoelectric hydrogel sensing units is led out from the lower conductive layer. A circuit board is also installed on the support layer, integrating a back-end signal acquisition circuit. This back-end signal acquisition circuit includes a voltage acquisition circuit module, a current acquisition circuit module, and a wireless transmission and core control module. The voltage acquisition circuit module is electrically connected to the upper and lower conductive layers and is used to acquire the voltage signals generated by each thermoelectric hydrogel sensing unit under the action of a temperature gradient in open-circuit mode to obtain foot temperature distribution information. The current acquisition circuit module is also connected to the upper and lower conductive layers and is used to acquire the current signals generated by each thermoelectric hydrogel sensing unit under the action of external pressure in closed-circuit mode to obtain foot pressure distribution information. The wireless transmission and core control module is electrically connected to both the voltage and current acquisition circuit modules, and is used to control the switching between voltage and current acquisition modes, and to perform analog-to-digital conversion, signal processing, and wireless transmission of the acquired voltage and current signals.

[0007] Furthermore, both the upper and lower conductive layers are made of polyimide substrates. The upper and lower surface electrodes of each thermoelectric hydrogel sensing unit are led out by a graphene conductive film formed on the polyimide substrate by laser induction.

[0008] Furthermore, both the upper and lower insulating layers are made of thermoplastic polyurethane film with a thickness of 20~100μm.

[0009] Furthermore, the support layer is made of polyurethane foam with a thickness of 2-8 mm, a pore size of 5-15 mm to accommodate through holes, and a density of 40-120 kg / m³. 3 .

[0010] Furthermore, the graphene patterns of the upper and lower conductive layers include multiple conductive leads and electrode contacts corresponding to the positions of each thermoelectric hydrogel sensitive unit. The conductive leads connect each electrode contact and extend to the edge of the insole to form an external interface.

[0011] Furthermore, the thermoelectric hydrogel sensing unit is a dual-network pressure-resistant hydrogel, which is composed of a dual-network skeleton of polyacrylamide and gelatin, and contains ferricyanide / ferrous cyanide redox couple ions. The Seebeck coefficient of the thermoelectric hydrogel sensing unit is 1.0~5.0mV / K, and the current response sensitivity under the pressure range of 0~500kPa is 0.1~1.0μA / kPa.

[0012] Furthermore, the voltage acquisition circuit module includes a multi-channel analog-to-digital converter chip and a multi-channel analog switch, used to poll and acquire voltage signals from each channel in open-circuit mode; the current acquisition circuit module includes a current sampling resistor, a multi-channel analog signal switch, a signal conditioning circuit, and an analog-to-digital converter. The multi-channel analog signal switch controls the connection and disconnection of the current sampling resistor in the measurement circuit. When current flows through the sampling resistor, a voltage drop is generated, indirectly realizing current measurement; the wireless transmission and core control modules are integrated into the same chip, including a microcontroller and a Bluetooth Low Energy module.

[0013] A method for preparing the aforementioned self-driven temperature-pressure decoupled smart insole based on thermoelectric hydrogel includes the following steps: Step S1, Preparation of dual-network anti-pressure hydrogel sensitive unit: Acrylamide monomer, gelatin and crosslinking agent are mixed evenly in solvent to obtain precursor solution. The precursor solution is injected into mold, initiator and catalyst are added, and the mixture is formed by thermally initiated free radical polymerization reaction. After demolding, the obtained dual-network anti-pressure hydrogel is immersed in electrolyte containing ferricyanide / ferrous cyanide redox couple to impart temperature-pressure sensitive properties to the gel, thus obtaining dual-network anti-pressure hydrogel sensitive unit; Step S2, prepare the upper conductive layer and the lower conductive layer: take a polyimide film, use a laser to scan and induce a preset pattern on the surface of the polyimide film in an air atmosphere, so that a patterned graphene conductive layer is formed on its surface, and the upper conductive layer and the lower conductive layer are obtained respectively. Step S3, prepare the support layer: take a polyurethane foam board and process multiple through holes according to a preset array layout to obtain a support layer for embedding thermoelectric hydrogel sensitive units. Step S4, lamination and encapsulation: From bottom to top, a lower conductive layer, a lower insulating layer, a support layer containing thermoelectric hydrogel sensitive units and a back-end signal acquisition circuit, an upper insulating layer, and an upper conductive layer are stacked sequentially, so that the upper and lower end faces of each thermoelectric hydrogel sensitive unit make contact with the corresponding electrode contacts on the upper and lower conductive layers, respectively, and the back-end signal acquisition circuit makes contact with the corresponding electrode contacts on the upper and lower conductive layers. An integrated flexible insole structure is formed by hot pressing or bonding processes.

[0014] Furthermore, the mechanical properties of the dual-network anti-compression hydrogel are controlled by at least one of the following three methods: (a) controlling the proportion of gelatin in the total mass of acrylamide monomer and gelatin, ranging from 5% to 30%; (b) adding sodium pyrrolidone carboxylate to the precursor solution, with an addition amount of 1% to 10% of the mass of acrylamide monomer; (c) immersing the polymerized dual-network anti-compression hydrogel in ammonium sulfate or sodium citrate solution for Hofmannster salting-out treatment for 1 to 6 hours.

[0015] Furthermore, the laser in step S2 is a CO2 laser or an ultraviolet laser. The CO2 laser has a wavelength of 10.6 μm and a power of 2~10 W, while the ultraviolet laser has a wavelength of 355 nm and a power of 1~5 W. The laser scanning speed is 100~500 mm / s.

[0016] The advantages of this application over the prior art are as follows: 1. This application utilizes the different output signal types of thermoelectric hydrogels in two working modes: open-circuit voltage mode (temperature sensing, high input impedance, almost no current flow) and closed-circuit current mode (pressure sensing, measuring ion current). By switching between voltage acquisition mode and current acquisition mode in a time-division manner, in-situ mode self-decoupling of temperature and pressure signals is achieved on the same thermoelectric hydrogel sensing unit. This eliminates the need for subsequent complex multivariate blind source separation and decoupling algorithms, simplifies the system architecture, and improves real-time performance.

[0017] 2. The temperature sensing in this application utilizes the temperature gradient between human body temperature and the ambient temperature of the shoe sole to autonomously generate a voltage signal through the thermoelectric hydrogel's thermal voltage effect, without the need for external power supply excitation, effectively reducing system power consumption; the pressure sensing utilizes the active piezoresistive effect of the thermoelectric hydrogel, without the need for external power supply excitation, and the overall power consumption is far lower than that of traditional piezoresistive sensing solutions.

[0018] 3. The 16 thermoelectric hydrogel sensing units of this application share two laser-induced graphene conductive layers as signal lead-out networks. The multi-channel analog switch time-division selection method is adopted, which greatly reduces the number of leads. All thermoelectric hydrogel sensing units are integrated into the same insole structure, which is compact and highly integrated.

[0019] 4. This application uses thermoelectric hydrogel (elastic modulus 10~100kPa), polyurethane foam, thermoplastic polyurethane film and laser-induced graphene conductive layer, all of which are flexible materials. The whole has the flexibility and conformity to fit the curved surface of the foot, making it comfortable to wear, and avoiding the mechanical mismatch problem between rigid sensors and flexible substrates.

[0020] 5. Laser-induced graphene conductive layers are formed on polyimide films in one step by laser direct writing, without the need for complex processes such as photolithography, vapor deposition, or printing; thermoelectric hydrogels can be formed by simple mold casting, making them suitable for mass production.

[0021] 6. This application can obtain real-time temperature and pressure distribution information at 16 points on the sole of the foot, and is applicable to application scenarios such as sports training monitoring, early screening of diabetic foot (early warning by monitoring abnormal high pressure areas and abnormal temperature changes on the sole of the foot), rehabilitation gait assessment, and fall warning for the elderly. Attached Figure Description

[0022] The following description, in conjunction with the accompanying drawings, further illustrates this application: Figure 1 This is an exploded view of the smart insole structure provided in an embodiment of this application; Figure 2 This is a schematic diagram of the array layout of the hydrogel sensing unit provided in an embodiment of this application; Figure 3 This is a schematic diagram illustrating the temperature-pressure self-decoupling principle of the thermoelectric hydrogel sensing unit provided in the embodiments of this application; Figure 4 A schematic diagram of the pattern structure of the upper and lower conductive layers (laser-induced graphene) provided in an embodiment of this application; Figure 5 A schematic block diagram of the back-end signal acquisition circuit provided in the embodiments of this application; In the diagram: 1 is the thermoelectric hydrogel sensing unit, 2 is the upper conductive layer, 3 is the upper insulating layer, 4 is the support layer, 5 is the lower insulating layer, 6 is the lower conductive layer, and 7 is the back-end signal acquisition circuit. Detailed Implementation

[0023] like Figures 1 to 5 As shown, this application provides a self-driven temperature-pressure decoupled smart insole based on thermoelectric hydrogel, including multiple thermoelectric hydrogel sensing units 1, a layered encapsulation structure and a back-end signal acquisition circuit 7. The multiple thermoelectric hydrogel sensing units 1 are arranged in an array inside the insole. Each thermoelectric hydrogel sensing unit 1 has dual functions of temperature gradient response and pressure response. Under the action of temperature gradient, a voltage signal is generated at its two ends, and under the action of external pressure, a current signal is generated. Through time-division switching between voltage acquisition mode and current acquisition mode, the temperature signal and pressure signal modes are self-decoupled on the same thermoelectric hydrogel sensing unit 1.

[0024] The layered encapsulation structure comprises, from top to bottom, an upper conductive layer 2, an upper insulating layer 3, a support layer 4, a lower insulating layer 5, and a lower conductive layer 6. The upper conductive layer 2 is a graphene conductive film formed by laser induction on a polyimide substrate, used to lead out the upper end face electrodes of each thermoelectric hydrogel sensing unit 1. The upper insulating layer 3 is a thermoplastic polyurethane film, disposed between the upper conductive layer 2 and the support layer 4. The support layer 4 is polyurethane foam, on which are formed through holes corresponding to multiple thermoelectric hydrogel sensing units 1. Each thermoelectric hydrogel sensing unit 1 is embedded in the corresponding through hole. The polyurethane foam is used to provide cushioning support for the insole, while isolating adjacent sensing units and reducing mechanical coupling and electrical signal crosstalk between units. The lower insulating layer 5 is a thermoplastic polyurethane film, disposed between the support layer 4 and the lower conductive layer 6. The lower conductive layer 6 is a graphene conductive film formed by laser induction on a polyimide substrate, used to lead out the lower end face electrodes of each thermoelectric hydrogel sensing unit 1. The upper insulating layer 3 and the lower insulating layer 5 are used to achieve flexible insulating encapsulation between the conductive layer and the support layer 4.

[0025] The back-end signal acquisition circuit 7 includes a voltage acquisition circuit module, a current acquisition circuit module, and a wireless transmission and core control module. The voltage acquisition circuit module is electrically connected to the upper conductive layer 2 and the lower conductive layer 6, and is used to acquire the voltage signals generated by each thermoelectric hydrogel sensitive unit 1 under the action of the temperature gradient in open circuit mode to obtain foot temperature distribution information. The current acquisition circuit module is connected to the upper conductive layer 2 and the lower conductive layer 6, and is used to acquire the current signals generated by each thermoelectric hydrogel sensitive unit 1 under the action of external pressure in closed circuit mode to obtain foot pressure distribution information. The wireless transmission and core control module is electrically connected to the voltage acquisition circuit module and the current acquisition circuit module respectively, and is used to control the switching between voltage acquisition mode and current acquisition mode, and to perform analog-to-digital conversion, signal processing, and wireless transmission on the acquired voltage and current signals.

[0026] The thermoelectric hydrogel sensing unit 1 comprises 16 units, with 8 arranged in the forefoot region, 4 in the arch region, and 4 in the heel region, to cover the main pressure and temperature monitoring areas of the sole of the foot. Figure 2 As shown.

[0027] The thermoelectric hydrogel sensing unit 1 is a dual-network pressure-resistant hydrogel, which is composed of a dual-network skeleton of polyacrylamide and gelatin. It contains ferricyanide / ferrousyanide redox couple ions, and its Seebeck coefficient is 1.0~5.0mV / K. Its current response sensitivity under pressure range of 0~500kPa is 0.1~1.0μA / kPa.

[0028] The graphene patterns of the upper conductive layer 2 and the lower conductive layer 6 include multiple conductive leads and electrode contacts corresponding to the positions of each thermoelectric hydrogel sensitive unit 1. The conductive leads connect each electrode contact and extend to the edge of the insole to form an external interface.

[0029] The thickness of the support layer 4 is 2~8mm, the pore size for accommodating through holes is 5~15mm, and the density of the polyurethane foam used in the support layer 4 is 40~120kg / m³. 3 .

[0030] The upper insulating layer 3 and the lower insulating layer 5 are made of thermoplastic polyurethane film with a thickness of 20~100μm.

[0031] The voltage acquisition circuit module includes a 16-channel analog-to-digital converter chip and a multi-channel analog switch, which is used to poll and acquire the voltage signals of each channel in open-circuit mode. The current acquisition circuit module includes a current sampling resistor, a 16-channel analog signal switch, a signal conditioning circuit and an analog-to-digital converter. The 16-channel analog signal switch controls the connection and disconnection of the current sampling resistor in the measurement circuit. When the current flows through the sampling resistor, a voltage drop is generated, which indirectly realizes the current measurement.

[0032] The wireless transmission and core control modules are integrated into the same chip, including a microcontroller and a Bluetooth Low Energy module. The voltage acquisition circuit module, current acquisition circuit module, and wireless transmission and core control module are arranged on a rigid printed circuit board with a length of 37mm and a width of 17mm. This circuit board is embedded in the arch area of ​​the support layer 4. Since the arch area is not a major stress area, the circuit board arrangement can reduce the impact on the flexibility of the insole and wearing comfort while ensuring signal acquisition function.

[0033] This application also provides a method for preparing a self-driven temperature-pressure decoupled smart insole based on thermoelectric hydrogel, comprising the following steps: Step S1, Preparation of dual-network anti-pressure hydrogel sensing unit 1: Acrylamide monomer, gelatin and crosslinking agent are mixed evenly in a solvent to obtain a precursor solution. The precursor solution is injected into a mold, an initiator and a catalyst are added, and the mixture is formed by thermally initiated free radical polymerization. After demolding, the obtained dual-network anti-pressure hydrogel is immersed in an electrolyte containing a ferricyanide / ferrous cyanide redox couple to impart temperature-pressure sensitive properties to the gel, thus obtaining dual-network anti-pressure hydrogel sensing unit 1. Step S2, prepare the upper conductive layer 2 and the lower conductive layer 6: take a polyimide film, use a laser to scan and induce a preset pattern on the surface of the polyimide film in an air atmosphere, so that a patterned graphene conductive layer is formed on its surface, and the upper conductive layer 2 and the lower conductive layer 6 are obtained respectively. Step S3, prepare support layer 4: Take polyurethane foam board and process multiple through holes according to the preset array layout to obtain support layer 4 for embedding thermoelectric hydrogel sensitive unit 1. Step S4, lamination and encapsulation: From bottom to top, the lower conductive layer 6, the lower insulating layer 5, the support layer 4 with the embedded thermoelectric hydrogel sensitive unit 1 and the back-end signal acquisition circuit 7, the upper insulating layer 3 and the upper conductive layer 2 are stacked sequentially, so that the upper and lower end faces of each thermoelectric hydrogel sensitive unit 1 are in contact with the corresponding electrode contacts on the upper conductive layer 2 and the lower conductive layer 6 respectively, and the back-end signal acquisition circuit 7 is in contact with the corresponding electrode contacts on the upper conductive layer 2 and the lower conductive layer 6. The integrated flexible insole structure is formed by hot pressing or bonding process.

[0034] In step S1, the crosslinking agent is N,N'-methylenebisacrylamide, the initiator is ammonium persulfate, the catalyst is tetramethylethylenediamine, the temperature for thermally initiating the free radical polymerization reaction is 60~80℃, and the time is 2~4 hours; the ferricyanide ion source in the electrolyte is potassium ferricyanide, the ferrocyanide ion source is potassium ferrocyanide, the concentration ratio of ferricyanide to ferrocyanide is 1:0.5~1:2, and the soaking time is 12~48 hours.

[0035] The mechanical properties of the dual-network anti-compression hydrogel were controlled by at least one of the following three methods: (a) controlling the proportion of gelatin in the total mass of acrylamide monomer and gelatin, ranging from 5% to 30%; (b) adding sodium pyrrolidone carboxylate to the precursor solution, with an addition amount of 1% to 10% of the mass of acrylamide monomer; (c) immersing the polymerized dual-network anti-compression hydrogel in ammonium sulfate or sodium citrate solution for Hofmann salting-out treatment for 1 to 6 hours.

[0036] The laser in step S2 is a CO2 laser or an ultraviolet laser. The CO2 laser has a wavelength of 10.6 μm and a power of 2~10 W, while the ultraviolet laser has a wavelength of 355 nm and a power of 1~5 W. The laser scanning speed is 100~500 mm / s.

[0037] The hot pressing process in step S4 has a temperature of 80~160℃, a pressure of 0.1~0.5MPa, and a time of 30~120 seconds.

[0038] Through the above technical solution, this application utilizes the thermoelectric voltage response and pressure current response characteristics of the thermoelectric hydrogel sensing unit 1 to realize time-division acquisition of temperature and pressure and mode self-decoupling on the same sensing unit, reducing the number of discrete sensors and wiring complexity; at the same time, the temperature detection process of the thermoelectric hydrogel has self-driving characteristics, which can reduce system power consumption and facilitate the realization of thin, flexible and comfortable smart insoles for foot health monitoring.

[0039] The present application will be further described below with reference to specific embodiments. Example 1

[0040] The self-driven temperature-pressure decoupled smart insole based on thermoelectric hydrogel includes 16 thermoelectric hydrogel sensing units 1, a layered encapsulation structure, and a back-end signal acquisition circuit 7.

[0041] Sixteen thermoelectric hydrogel sensing units 1 are arranged in an array inside the insole: eight in the forefoot area (in a 3-3-2 three-row distribution), four in the arch area (in a 2×2 matrix distribution), and four in the heel area (in a 2×2 matrix distribution). Each thermoelectric hydrogel sensing unit 1 is a cylinder made of double-network pressure-resistant hydrogel, with a diameter of 10 mm and a height of 5 mm. In preparation, 1.8 g of acrylamide monomer, 0.2 g of gelatin (gelatin accounting for 10% of the total mass of monomer and gelatin), and 0.02 g of N,N'-methylenebisacrylamide crosslinking agent were weighed and dissolved in 6.5 mL of deionized water. The mixture was magnetically stirred for 30 minutes in a 50°C water bath to ensure complete dissolution and mixing. Then, 0.02 g of ammonium persulfate initiator and 15 μL of tetramethylethylenediamine catalyst were added and rapidly stirred until homogeneous. The mixture was then poured into a cylindrical mold with an inner diameter of 20 mm and a height of 5 mm. The mold was placed in a 60°C oven for polymerization reaction for 3 hours to form a polyacrylamide-gelatin dual-network hydrogel. After demolding, the dual-network hydrogel was immersed in an electrolyte containing 0.1 M potassium ferricyanide and 0.1 M potassium ferrocyanide (concentration ratio 1:1) for 24 hours to allow the ferricyanide / ferrocyanide redox couple ions to penetrate into the gel network, giving it temperature-pressure sensitive properties. The Seebeck coefficient was tested to be 1.2 mV / K, and the current response sensitivity in the pressure range of 0~200 kPa was 0.35 μA / kPa.

[0042] Graphene patterns of upper conductive layer 2 and lower conductive layer 6 were fabricated using a CO2 laser with a wavelength of 10.6 μm and a power of 2~10 W.

[0043] The layered encapsulation structure, from top to bottom, includes an upper conductive layer 2, an upper insulating layer 3, a support layer 4, a lower insulating layer 5, and a lower conductive layer 6. After aligning the layers, they are placed in a hot press and hot-pressed at 100°C and 0.3MPa for 60 seconds to melt the thermoplastic polyurethane film and form a reliable bond between the layers. After cooling to room temperature, an integrated flexible insole body is obtained. After hot-pressing and encapsulation, elastic sealant is applied to the edges of the insole and the seams of each layer for secondary sealing to prevent hydrogel dehydration and external sweat penetration. The upper and lower end faces of each thermoelectric hydrogel sensing unit 1 are in contact with the corresponding electrodes on the upper conductive layer 2 and lower conductive layer 6 through micropores on the upper insulating layer 3 and lower insulating layer 5, respectively. After the thermoelectric hydrogel sensing unit 1 is embedded, the micropores on the upper insulating layer 3 and lower insulating layer 5 form a self-sealing effect with the insulating layer through the viscoelasticity of the gel itself, further reducing moisture evaporation. The back-end signal acquisition circuit 7 is mounted on a rigid printed circuit board with a length of 37mm and a width of 17mm. The circuit board is embedded in the arch area of ​​the support layer 4 (the arch is not a major stress area, and the embedding of the circuit board does not affect the wearing comfort).

[0044] Before initial use, the smart insoles undergo factory calibration: the insoles are placed on a constant temperature platform, with five temperature gradient points (ΔT = 0, 2, 5, 8, 10℃) and five pressure points (0, 50, 100, 150, 200 kPa) set. The voltage and current outputs of each channel are recorded, establishing temperature-voltage and pressure-current calibration curves for each channel. The calibration coefficients are stored in the microcontroller's non-volatile memory. During normal operation, the microcontroller performs online compensation on the raw data of each channel based on the calibration coefficients to eliminate performance differences between channels.

[0045] Performance test results show that the temperature resolution of each channel is better than 0.05℃, and it can output stably within the range of 30~40℃; the pressure detection range is 5~200kPa, and the detection resolution is better than 1kPa. The 16-channel temperature and pressure data show regular changes with the gait cycle, and the correlation coefficient R with the results of commercial pressure plates and infrared thermal imagers is [missing data]. 2 Greater than 0.95. In the stability test of continuous operation for 24 hours, the Seebeck coefficient change rate of each thermoelectric hydrogel sensitive unit 1 was less than 5%, and the current response sensitivity change rate was less than 8%. After 10,000 cycles of treading (pressure range 20~200kPa, frequency 1Hz), the sensitivity retention rate of each channel was greater than 85%, indicating that it has the durability to meet the actual use requirements. Example 2

[0046] The difference between this embodiment and Embodiment 1 lies in the mechanical property control method and laser processing parameters of the dual-network anti-compression hydrogel.

[0047] Regarding the regulation of gel mechanical properties, two of the three methods were combined: (1) increasing the gelatin content to 20% (acrylamide 1.6g, gelatin 0.4g) to enhance the physical crosslinking density of the dual-network structure; (2) immersing the polymerized dual-network hydrogel in 1M ammonium sulfate solution for 2 hours for Hoffmann salting-out treatment to further densify the gel network. After the above combined regulation, the compressive modulus of the dual-network hydrogel increased by about 3 times compared with Example 1, and the Seebeck coefficient increased to 1.5mV / K. Regarding laser processing parameters, an ultraviolet laser (wavelength 355nm, power 1.5W, scanning speed 300mm / s) was used to process the polyimide film. Compared with the CO2 laser, the heat-affected zone of the ultraviolet laser is smaller, and the linewidth resolution of the laser-induced graphene can reach 50μm, which is beneficial to improving the fineness of the conductive pattern and is suitable for making higher density sensitive unit arrays.

[0048] The remaining steps are the same as in Example 1. Example 3

[0049] The difference between this embodiment and Embodiment 1 lies in the processing method of the support layer 4 and the interlayer connection process.

[0050] Regarding the processing method of support layer 4, 3D printing (fused deposition modeling) is used to directly print a customized support layer 4 with 16 accommodating through holes using flexible thermoplastic polyurethane filaments. This method can be personalized according to the arch shape and gait characteristics of different users, achieving better fit and comfort. In terms of interlayer bonding, thermoplastic polyurethane hot melt adhesive film is used instead of thermoplastic polyurethane insulating film. Bonding between layers can be achieved at a low temperature of 60 to 80°C, avoiding the impact of high-temperature hot pressing on the water content of the thermoelectric hydrogel sensitive unit 1, thus maintaining the ionic conductivity and thermoelectric properties of the thermoelectric hydrogel.

[0051] The remaining steps are the same as in Example 1.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A self-driven temperature-pressure decoupled smart insole based on thermoelectric hydrogel, characterized in that: The smart insole adopts a layered encapsulation structure, which consists of an upper conductive layer (2), an upper insulating layer (3), a support layer (4), a lower insulating layer (5), and a lower conductive layer (6) from top to bottom. The upper insulating layer (3) is used to achieve flexible insulating encapsulation between the upper conductive layer (2) and the support layer (4), and the lower insulating layer (5) is used to achieve flexible insulating encapsulation between the lower conductive layer (6) and the support layer (4). The support layer (4) is provided with multiple through holes according to the pressure and temperature monitoring area array of the foot sole. Each through hole contains a thermoelectric hydrogel sensing unit (1) that has both temperature gradient response and pressure response functions. The upper end face electrode of all thermoelectric hydrogel sensing units (1) is led out from the upper conductive layer (2), and the lower end face electrode of all thermoelectric hydrogel sensing units (1) is led out from the lower conductive layer (6). A circuit board is also provided on the support layer (4), and a back-end signal acquisition circuit (7) is integrated on the circuit board. The back-end signal acquisition circuit (7) includes a voltage acquisition circuit module, a current acquisition circuit module and a wireless transmission and core control module. The voltage acquisition circuit module is electrically connected to the upper conductive layer (2) and the lower conductive layer (6) and is used to acquire the voltage signal generated by each thermoelectric hydrogel sensitive unit (1) under the action of the temperature gradient in the open circuit mode in order to obtain the foot temperature distribution information. The current acquisition circuit module is connected to the upper conductive layer (2) and the lower conductive layer (6) to acquire the current signal generated by each thermoelectric hydrogel sensitive unit (1) under the action of external pressure in closed-circuit mode, so as to obtain the foot pressure distribution information. The wireless transmission and core control module is electrically connected to the voltage acquisition circuit module and the current acquisition circuit module, respectively. It is used to control the switching between voltage acquisition mode and current acquisition mode, and to perform analog-to-digital conversion, signal processing and wireless transmission on the acquired voltage and current signals.

2. The self-driven temperature-pressure decoupling smart insole based on thermoelectric hydrogel according to claim 1, characterized in that: Both the upper conductive layer (2) and the lower conductive layer (6) are made of polyimide substrate. The upper and lower surface electrodes of each thermoelectric hydrogel sensitive unit (1) are led out by a graphene conductive film formed by laser induction on the polyimide substrate through a laser.

3. The self-driven temperature-pressure decoupling smart insole based on thermoelectric hydrogel according to claim 1, characterized in that: Both the upper insulating layer (3) and the lower insulating layer (5) are made of thermoplastic polyurethane film with a thickness of 20~100μm.

4. The self-driven temperature-pressure decoupling smart insole based on thermoelectric hydrogel according to claim 1, characterized in that: The support layer (4) is made of polyurethane foam with a thickness of 2~8mm, a pore size of 5~15mm to accommodate through holes, and a density of 40~120kg / m³. 3 .

5. The self-driven temperature-pressure decoupling smart insole based on thermoelectric hydrogel according to claim 2, characterized in that: The graphene patterns of the upper conductive layer (2) and the lower conductive layer (6) include multiple conductive leads and electrode contacts corresponding to the positions of each thermoelectric hydrogel sensitive unit (1). The conductive leads connect each electrode contact and extend to the edge of the insole to form an external interface.

6. The self-driven temperature-pressure decoupling smart insole based on thermoelectric hydrogel according to claim 1, characterized in that: The thermoelectric hydrogel sensing unit (1) is a double-network pressure-resistant hydrogel, which is composed of a double-network skeleton of polyacrylamide and gelatin. It contains ferricyanide / ferrous cyanide redox couple ions. The Seebeck coefficient of the thermoelectric hydrogel sensing unit (1) is 1.0~5.0mV / K, and the current response sensitivity under the pressure range of 0~500kPa is 0.1~1.0μA / kPa.

7. The self-driven temperature-pressure decoupling smart insole based on thermoelectric hydrogel according to claim 1, characterized in that: The voltage acquisition circuit module includes a multi-channel analog-to-digital converter chip and a multi-channel analog switch, which are used to poll and acquire the voltage signals of each channel in open-circuit mode; The current acquisition circuit module includes a current sampling resistor, a multi-channel analog signal switch, a signal conditioning circuit, and an analog-to-digital converter. The multi-channel analog signal switch controls the connection and disconnection of the current sampling resistor in the measurement circuit. When current flows through the sampling resistor, a voltage drop is generated, which indirectly realizes the current measurement. The wireless transmission and core control modules are integrated into the same chip, including a microcontroller and a Bluetooth Low Energy module.

8. A method for preparing a self-driven temperature-pressure decoupled smart insole based on thermoelectric hydrogel as described in any one of claims 1-7, characterized in that: Includes the following steps: Step S1, Preparation of dual-network anti-pressure hydrogel sensitive unit (1): Acrylamide monomer, gelatin and crosslinking agent are mixed evenly in solvent to obtain a precursor solution. The precursor solution is injected into a mold, an initiator and a catalyst are added, and the mixture is formed by thermally initiated free radical polymerization reaction. After demolding, the obtained dual-network anti-pressure hydrogel is immersed in an electrolyte containing ferricyanide / ferrous cyanide redox couple to impart temperature-pressure sensitive properties to the gel, thus obtaining dual-network anti-pressure hydrogel sensitive unit (1). Step S2, prepare the upper conductive layer (2) and the lower conductive layer (6): take a polyimide film, use a laser to scan and induce a preset pattern on the surface of the polyimide film in an air atmosphere, so that a patterned graphene conductive layer is formed on its surface, and the upper conductive layer (2) and the lower conductive layer (6) are obtained respectively. Step S3, prepare the support layer (4): take a polyurethane foam board and process multiple through holes according to the preset array layout to obtain the support layer (4) for embedding the thermoelectric hydrogel sensitive unit (1). Step S4, lamination and encapsulation: from bottom to top, the lower conductive layer (6), the lower insulating layer (5), the support layer (4) with the thermoelectric hydrogel sensitive unit (1) and the back-end signal acquisition circuit (7) are stacked sequentially, the upper insulating layer (3) and the upper conductive layer (2) are stacked, so that the upper and lower end faces of each thermoelectric hydrogel sensitive unit (1) are in contact with the corresponding electrode contacts on the upper conductive layer (2) and the lower conductive layer (6) respectively, and the back-end signal acquisition circuit (7) is in contact with the corresponding electrode contacts on the upper conductive layer (2) and the lower conductive layer (6) respectively. The integrated flexible insole structure is formed by hot pressing or bonding process.

9. The method for preparing a self-driven temperature-pressure decoupled smart insole based on thermoelectric hydrogel according to claim 8, characterized in that: The mechanical properties of the dual-network anti-compression hydrogel were controlled by at least one of the following three methods: (a) controlling the proportion of gelatin in the total mass of acrylamide monomer and gelatin, ranging from 5% to 30%; (b) adding sodium pyrrolidone carboxylate to the precursor solution, with an addition amount of 1% to 10% of the mass of acrylamide monomer; (c) immersing the polymerized dual-network anti-compression hydrogel in ammonium sulfate or sodium citrate solution for Hofmann salting-out treatment for 1 to 6 hours.

10. The method for preparing a self-driven temperature-pressure decoupled smart insole based on thermoelectric hydrogel according to claim 8, characterized in that: The laser in step S2 is a CO2 laser or an ultraviolet laser. The CO2 laser has a wavelength of 10.6 μm and a power of 2~10 W, while the ultraviolet laser has a wavelength of 355 nm and a power of 1~5 W. The laser scanning speed is 100~500 mm / s.

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