Iontophoretic electro-gel and method of making and flexible self-powered thermoelectric devices

Abstract

The application belongs to the field of self-powered materials, and discloses an ionic thermoelectric gel, a preparation method thereof and a flexible self-powered thermoelectric device, comprising the following steps: adding polyvinyl alcohol, sodium alginate and calcium chloride into a mixed system of deionized water and glycerol to obtain solution A; adding sodium citrate into the solution A to obtain solution B; adding potassium ferricyanide and potassium ferrocyanide into the solution B to obtain solution C; and freezing and thawing the solution C to obtain a shaped gel; and soaking the shaped gel in a sodium citrate solution to obtain the ionic thermoelectric gel. Through the multi-dimensional innovative design of the double-network matrix construction, the sodium citrate multi-regulation and the double thermoelectric mechanism synergy, the core problems of the poor mechanical adaptability, the insufficient power transmission stability and the weak long-term service ability of the existing ionic thermoelectric gel are improved, the dynamic deformation demand of the human body movement is adapted, the continuous discharge under the small temperature difference of the human body is realized, and the long-life synergistic optimization of the mechanical properties and the power transmission performance is realized.

Description

Technical Field

[0001] This invention belongs to the field of self-powered materials, and relates to an ion thermoelectric gel, its preparation method, and a flexible self-powered thermoelectric device. Background Technology

[0002] With the development of flexible electronics and wearable technology, the demand for self-powered materials for human body sensing devices, such as physiological signal monitoring, motion sensing, and health early warning devices, is becoming increasingly urgent. Among them, ion thermogel, as a core material that can convert small temperature differences (1~5K) on the human body surface into electrical energy, has become an ideal choice for self-powered human body sensing due to its suitability for low-order waste heat recovery.

[0003] However, existing ion thermoelectric gels have the following problems in human body sensing applications, making it difficult to meet actual usage requirements: (1) Poor mechanical property adaptability. Most current ion thermoelectric gels have loose network structures, low tensile strength, limited elongation at break, and weak resistance to cyclic deformation. They are difficult to withstand dynamic stretching and bending deformations during human movement, and are prone to cracking and damage, making them unsuitable for dynamic human use scenarios. (2) Unstable power transmission performance. Current ion thermoelectric gels rely on a single thermal diffusion generator mechanism, with the potential originating from the ion concentration gradient. However, the temperature difference on the human body surface fluctuates little and tends to be stable, and the concentration gradient is easily depleted quickly, resulting in insufficient continuous discharge capacity. At the same time, during cyclic charging and discharging or switching between "with temperature difference and no temperature difference", the thermoelectric performance significantly degrades, the voltage output fluctuates greatly, and the power transmission stability is poor. (3) Insufficient long-term service capability. Most current ion thermogels have poor water retention capacity and are prone to water loss and drying in open environments worn by the human body, causing network shrinkage and cracking, resulting in a sharp drop in ion migration efficiency; in addition, they lack a long-term performance maintenance mechanism, and the output stability continues to decline during long-term use, making it difficult to meet the long-term service requirements of human body sensing devices. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an ion thermoelectric gel, its preparation method, and a flexible self-powered thermoelectric device.

[0005] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a method for preparing an ionic thermoelectric gel, comprising: adding polyvinyl alcohol, sodium alginate and calcium chloride to a mixture of deionized water and glycerol to obtain solution A; adding sodium citrate to solution A to obtain solution B; adding potassium ferrocyanide and potassium ferrocyanide to solution B to obtain solution C; allowing solution C to stand and solidify to obtain a solidified gel; freezing the solidified gel, thawing it, and immersing it in a sodium citrate solution to obtain an ionic thermoelectric gel.

[0006] Optionally, the step of adding polyvinyl alcohol, sodium alginate, and calcium chloride to a mixture of deionized water and glycerin to obtain solution A comprises: adding 1.2 to 1.6 parts by mass of polyvinyl alcohol, 0.24 to 0.32 parts by mass of sodium alginate, and 0.34 to 0.46 parts by mass of calcium chloride to a mixture of 12 to 16 parts by mass of deionized water and 5 to 7 parts by mass of glycerin to obtain solution A.

[0007] Optionally, adding sodium citrate to solution A to obtain solution B includes: adding 3.4 to 4.5 parts by mass of sodium citrate solution to solution A to obtain solution B; wherein the mass fraction of sodium citrate solution is 25 to 35 wt%.

[0008] Optionally, the step of adding potassium ferricyanide and potassium ferrocyanide to solution B to obtain solution C includes: adding 0.17 to 0.21 parts by mass of a mixture of potassium ferricyanide and potassium ferrocyanide to solution B to obtain solution C; wherein, in the mixture of potassium ferricyanide and potassium ferrocyanide, the mass ratio of potassium ferricyanide to potassium ferrocyanide is 1:0.8 to 1.2.

[0009] Optionally, the step of freezing and thawing the molded gel and immersing it in a sodium citrate solution includes: freezing the molded gel at a freezing temperature of -25 to -15°C for 2 to 4 hours, thawing it at room temperature for 4 to 8 hours, and then immersing it in a saturated sodium citrate solution for 4 to 8 hours.

[0010] Optionally, the step of adding polyvinyl alcohol, sodium alginate, and calcium chloride to a mixture of deionized water and glycerin to obtain solution A includes: adding polyvinyl alcohol, sodium alginate, and calcium chloride to a mixture of deionized water and glycerin, and stirring continuously at 80-100°C for 1-4 hours to obtain solution A.

[0011] Optionally, the degree of alcoholysis of the polyvinyl alcohol is 85-90 mol%, and the viscosity of the polyvinyl alcohol is 600-1500 mPa. s, the viscosity of the sodium alginate is 180~250 mPa. s.

[0012] In a second aspect, the present invention provides an ion thermoelectric gel prepared based on the above-described method for preparing ion thermoelectric gels.

[0013] In a third aspect, the present invention provides a flexible self-powered thermoelectric device, comprising a plurality of stacked and connected lattice units, wherein a gas-liquid phase change layer is disposed between adjacent lattice units; the lattice unit comprises a plurality of lattice-distributed and parallel-connected basic units; the basic unit comprises the aforementioned ion thermoelectric gel and flexible electrodes disposed at the upper and lower ends of the ion thermoelectric gel.

[0014] Optionally, the gas-liquid phase change layer includes a connected accommodating cavity and a flexible microchannel heat dissipation structure; the accommodating cavity is provided with a phase change working fluid that can undergo gas-liquid phase change within the operating temperature range of the flexible self-powered thermoelectric device; the flexible microchannel heat dissipation structure is disposed on the side of the flexible self-powered thermoelectric device; the flexible electrode is a gold foil, silver foil, copper foil, or carbon electrode.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method for preparing ionothermal gels, employing a dual-network structure of polyvinyl alcohol (PVA) and sodium alginate to construct the gel matrix. PVA forms a rigid network containing crystalline regions and hydrogen bonds to bear the main stress, while sodium alginate forms additional hydrogen bonds and dynamic ionic crosslinks with PVA through carboxyl groups, constituting a flexible buffer network that effectively disperses stress concentration. This is combined with the Ca²⁺ released from calcium chloride. + Coordination and crosslinking with sodium alginate carboxyl groups further strengthens the dual-network framework; simultaneously, sodium citrate promotes interchain hydrogen bonding of polyvinyl alcohol, improving the interfacial compatibility of the dual-network and achieving network densification. Through the synergistic effect of these improvements, the tensile strength of the ionic thermoelectric gel reaches 2.3 MPa, the elongation at break exceeds 500%, and the recovery rate after 100 cycles of stretching (100% stretching) is ≥80%. This effectively improves the problems of low tensile strength and weak resistance to cyclic deformation in existing ionic thermoelectric gels, allowing it to withstand dynamic stretching and bending deformations during human movement, reducing the risk of cracking and breakage, and better adapting to dynamic human usage scenarios. Furthermore, based on the dual thermoelectric mechanism of redox pair dominance and thermal diffusion assistance achieved by potassium ferrocyanide and potassium ferrocyanide, the reversible redox system composed of potassium ferrocyanide and potassium ferrocyanide can form a continuous current through directional electron transfer under small temperature differences (1~5K), without relying on easily depleted ion concentration gradients, improving the insufficient continuous discharge capability of existing technologies; the large amount of free Na released by the dissociation of sodium citrate... +It provides ample charge carriers for the thermal diffusion mechanism and forms complementary transport channels with redox pairs, improving ionic conductivity and ensuring voltage output stability. Testing showed that with an initial hot-charge voltage of 40mV, it could maintain 8mV after discharging for 1 hour with an external 500Ω resistor. Furthermore, after multiple cycles of switching between "with temperature difference" and "without temperature difference," the voltage output amplitude and discharge power showed no significant attenuation, significantly improving the existing problems of performance degradation and large voltage fluctuations in gel cyclic charge-discharge. Furthermore, the addition of glycerol to the system, which forms hydrogen bonds with the molecular chains of polyvinyl alcohol and sodium alginate, significantly reduces the rate of water evaporation, effectively solving the defects of existing ionic thermoelectric gels such as weak water retention and easy dehydration. Simultaneously, glycerol synergistically works with the dual-network structure to maintain the integrity of the porous structure of the ionic thermoelectric gel, preventing network shrinkage and cracking and a decrease in ion migration efficiency due to water loss. In addition, sodium citrate exhibits excellent biocompatibility with both polyvinyl alcohol and sodium alginate, posing no risk of skin sensitization, making it suitable for long-term wear scenarios. This achieves long-term synergistic stability of mechanical and electrical performance, ensuring that output stability does not decline during long-term use, meeting the core requirement of long-term reliable service for human sensor devices. In summary, this invention, through multi-dimensional innovative design involving dual-network matrix construction, multiple regulation of sodium citrate, and synergistic dual thermoelectric mechanisms, specifically addresses the core problems of poor mechanical adaptability, insufficient electrical stability, and weak long-term service capability of existing ionic thermoelectric gels. Attached Figure Description

[0016] Figure 1 This is a flowchart of the ion thermogel preparation method according to an embodiment of the present invention.

[0017] Figure 2 This is a morphological diagram of the ion thermoelectric gel prepared in Example 1 of the present invention.

[0018] Figure 3 The images are SEM images of the ion thermogel prepared in Example 1 of this invention at different magnifications; Figure (a) is a 500x SEM image, Figure (b) is a 2000x SEM image, and Figure (c) is a 3000x SEM image.

[0019] Figure 4 The thermo-voltage response diagram of the ion thermoelectric gel prepared in Example 1 of the present invention under different temperature differences.

[0020] Figure 5 The graph shows the thermoelectric potential test results of the ion thermoelectric gel prepared in Example 1 of this invention.

[0021] Figure 6 The thermo-voltage response diagram of the ion thermoelectric gel prepared in Example 1 of the present invention under 6 cycles of heating and cooling.

[0022] Figure 7The figure shows the discharge test results of the ion thermoelectric gel prepared in Example 1 of the present invention with an external 500Ω resistor.

[0023] Figure 8 The image shows the tensile stress-strain curve of the ion thermogel prepared in Example 1 of this invention.

[0024] Figure 9 The stress-strain curve of the ion thermogel prepared in Example 1 of the present invention after being stretched 100 times at 100% strain.

[0025] Figure 10 This is a schematic diagram of the flexible self-powered thermoelectric device according to an embodiment of the present invention.

[0026] Wherein: 1-flexible electrode; 2-ion thermoelectric gel; 3-gas-liquid phase change layer. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0028] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0029] The present invention will now be described in further detail with reference to the accompanying drawings: See Figure 1 In one embodiment of the present invention, a method for preparing ionic thermoelectric gel is provided, specifically a method for preparing ionic thermoelectric gel with deformation resistance and long lifespan.

[0030] Specifically, the method for preparing ion thermoelectric gel of the present invention includes the following steps: S1: Polyvinyl alcohol, sodium alginate, and calcium chloride are added to a mixture of deionized water and glycerol to obtain solution A.

[0031] S2: Add sodium citrate to solution A to obtain solution B.

[0032] S3: Add potassium ferricyanide and potassium ferrocyanide to solution B to obtain solution C.

[0033] S4: Allow solution C to stand and solidify to obtain a shaped gel.

[0034] S5: After freezing the molded gel, thaw it and soak it in sodium citrate solution to obtain ion thermoelectric gel.

[0035] Explanatoryly, the method for preparing ion thermoelectric gel of the present invention firstly uses polyvinyl alcohol and sodium alginate as raw materials, dissolves them in a deionized water-glycerol mixture, and adds calcium chloride for crosslinking to obtain a homogeneous mixed solution. Then, using this mixed solution as a matrix, it is subjected to salting-out regulation and performance optimization with sodium citrate solution to obtain an ion-regulated mixed solution. Subsequently, the ion-regulated mixed solution is used as a dispersion and carrier matrix, and is compounded with a redox pair formed by potassium ferrocyanide and potassium ferrocyanide to obtain a thermoelectric functional mixed solution. Finally, the thermoelectric functional mixed solution is poured into a mold and allowed to stand to form. After freeze-thaw strengthening and soaking in sodium citrate solution for a period of time, an ion thermoelectric gel with deformation resistance, long life and excellent thermoelectric performance is obtained.

[0036] This invention discloses a method for preparing ionothermal gels, employing a dual-network structure of polyvinyl alcohol (PVA) and sodium alginate to construct the gel matrix. PVA forms a rigid network containing crystalline regions and hydrogen bonds to bear the main stress, while sodium alginate forms additional hydrogen bonds and dynamic ionic crosslinks with PVA through carboxyl groups, constituting a flexible buffer network that effectively disperses stress concentration. This is combined with the Ca²⁺ released from calcium chloride. + Coordination and crosslinking with sodium alginate carboxyl groups further strengthens the dual-network framework; simultaneously, sodium citrate promotes interchain hydrogen bonding of polyvinyl alcohol, improving the interfacial compatibility of the dual-network and achieving network densification. Through these synergistic improvements, the tensile strength of the ionic thermoelectric gel reaches 2.3 MPa, the elongation at break exceeds 500%, and the recovery rate after 100 cycles of stretching (100% stretching) is ≥80%. This effectively improves the low tensile strength and weak resistance to cyclic deformation of existing ionic thermoelectric gels, allowing them to withstand dynamic stretching and bending deformations during human movement, reducing the risk of cracking and breakage, and better adapting to dynamic human usage scenarios. Furthermore, based on the redox-dominant heating diffusion-assisted dual thermoelectric mechanism achieved by potassium ferrocyanide and potassium ferrocyanide, the reversible redox system composed of potassium ferrocyanide and potassium ferrocyanide can form a continuous current through directional electron transfer under small temperature differences (1~5K), without relying on easily depleted ion concentration gradients, improving the insufficient continuous discharge capability of existing technologies; the large amount of free Na released by the dissociation of sodium citrate... +It provides ample charge carriers for the thermal diffusion mechanism and forms complementary transport channels with redox pairs, improving ionic conductivity and ensuring voltage output stability. Testing showed that with an initial hot-charge voltage of 40mV, it could maintain 8mV after discharging for 1 hour with an external 500Ω resistor. Furthermore, after multiple cycles of switching between "with temperature difference" and "without temperature difference," the voltage output amplitude and discharge power showed no significant attenuation, significantly improving the existing problems of performance degradation and large voltage fluctuations in gel cyclic charge-discharge. Furthermore, the addition of glycerol to the system, which forms hydrogen bonds with the molecular chains of polyvinyl alcohol and sodium alginate, significantly reduces the rate of water evaporation, effectively solving the defects of existing ionic thermoelectric gels such as weak water retention and easy dehydration. Simultaneously, glycerol synergistically works with the dual-network structure to maintain the integrity of the porous structure of the ionic thermoelectric gel, preventing network shrinkage and cracking and a decrease in ion migration efficiency due to water loss. In addition, sodium citrate exhibits excellent biocompatibility with both polyvinyl alcohol and sodium alginate, posing no risk of skin sensitization, making it suitable for long-term wear scenarios. This achieves long-term synergistic stability of mechanical and electrical performance, ensuring that output stability does not decline during long-term use, meeting the core requirement of long-term reliable service for human sensor devices. In summary, this invention, through multi-dimensional innovative design involving dual-network matrix construction, multiple regulation of sodium citrate, and synergistic dual thermoelectric mechanisms, specifically addresses the core problems of poor mechanical adaptability, insufficient electrical stability, and weak long-term service capability of existing ionic thermoelectric gels.

[0037] In one feasible embodiment, the step of adding polyvinyl alcohol, sodium alginate, and calcium chloride to a mixture of deionized water and glycerol to obtain solution A comprises: adding 1.2 to 1.6 parts by mass of polyvinyl alcohol, 0.24 to 0.32 parts by mass of sodium alginate, and 0.34 to 0.46 parts by mass of calcium chloride to a mixture of 12 to 16 parts by mass of deionized water and 5 to 7 parts by mass of glycerol to obtain solution A.

[0038] In one feasible embodiment, the step of adding sodium citrate to solution A to obtain solution B includes: adding 3.4 to 4.5 parts by mass of sodium citrate solution to solution A to obtain solution B; wherein the mass fraction of sodium citrate solution is 25 to 35 wt%.

[0039] In one feasible embodiment, the step of adding potassium ferricyanide and potassium ferrocyanide to solution B to obtain solution C comprises: adding 0.17 to 0.21 parts by mass of a mixture of potassium ferricyanide and potassium ferrocyanide to solution B to obtain solution C; wherein, in the mixture of potassium ferricyanide and potassium ferrocyanide, the mass ratio of potassium ferricyanide to potassium ferrocyanide is 1:0.8 to 1.2.

[0040] In one feasible embodiment, the step of freezing and thawing the molded gel and immersing it in a sodium citrate solution includes: freezing the molded gel at a freezing temperature of -25 to -15°C for 2 to 4 hours, thawing it at room temperature for 4 to 8 hours, and then immersing it in a saturated sodium citrate solution for 4 to 8 hours.

[0041] In one feasible embodiment, the step of adding polyvinyl alcohol, sodium alginate, and calcium chloride to a mixture of deionized water and glycerin to obtain solution A includes: adding polyvinyl alcohol, sodium alginate, and calcium chloride to a mixture of deionized water and glycerin, and stirring continuously at 80-100°C for 1-4 hours to obtain solution A.

[0042] The following explains the selection criteria for each material in the preparation method of the ion thermogel of this invention.

[0043] (1) Matrix material. Polyvinyl alcohol (PVA): A rigid network containing crystalline regions and hydrogen bonds, balancing mechanical strength and structural stability, with excellent biocompatibility, and readily forming an interpenetrating double network with sodium alginate, providing a basic channel for ion migration. Sodium alginate (SA): The carboxyl groups of the molecular chain can form hydrogen bonds and dynamic ionic crosslinks with PVA, improving the gel's elongation at break and cycle recovery, and the weak electrostatic effect avoids Na+. + It aggregates and releases free-state charge carriers, and its biocompatibility meets the needs of skin contact.

[0044] (2) Solvent materials. Deionized water: As the core dissolving medium, it has high purity and is free from impurities, which can fully disperse PVA, sodium alginate and various functional components, ensuring the homogeneity of the system and providing a stable environment for the formation of the double network and ion migration. Glycerol: It has high chemical stability, forms hydrogen bonds with polymer chains to lower the glass transition temperature and improve gel flexibility; at the same time, it reduces water evaporation, avoids the degradation of mechanical and thermoelectric properties under dry conditions, and ensures the long-term service capability of the material.

[0045] (3) Structure-regulating materials. Sodium citrate (Na3Cit): High dissociation efficiency, releasing a large amount of Na. + As a charge carrier; Cit³ - It can promote hydrogen bond cross-linking between PVA chains, enhance the interfacial compatibility between PVA and sodium alginate, achieve network densification, and has excellent biocompatibility with no risk of skin sensitization. Calcium chloride (CaCl2): releases Ca... 2+ Coordination and crosslinking with sodium alginate carboxyl groups strengthens the dual-network gel framework, replenishes ion carriers, and improves gel mechanical stability and ion migration efficiency.

[0046] (4) Redox relationship of materials. Potassium ferricyanide (K3[Fe(CN)6]): stable oxidizing property, reduced to Fe(CN)6 under thermal gradient. 4-It exhibits good compatibility with gel networks, meeting the continuous discharge requirements under small temperature differences in the human body. Potassium ferrocyanide (K4[Fe(CN)6]): It is reducingly stable and is oxidized to Fe(CN)6 under a thermal gradient. 3- It has good compatibility with gel networks and is suitable for the continuous discharge needs of the human body under small temperature differences.

[0047] The preparation method of the ion thermoelectric gel of the present invention is illustrated below with specific embodiments.

[0048] Example 1 Step 1, Mixing and Dissolving: Add 1.4 g of polyvinyl alcohol, 0.28 g of sodium alginate and 0.4 g of calcium chloride to a mixture of 14 g of deionized water and 6 g of glycerol, and stir continuously at 95 °C for 2 hours to obtain a colorless, transparent and homogeneous solution A.

[0049] Step 2, sodium citrate adjustment: Slowly add 3.4 g of 25 wt% sodium citrate solution dropwise to solution A while stirring for 0.5 hours to obtain solution B.

[0050] Step 3, Introduce redox pairs: Add 0.1 g of potassium ferricyanide and 0.09 g of potassium ferrocyanide to solution B, and continue stirring for 0.5 hours to obtain solution C.

[0051] Step 4, let it stand and form: Pour solution C into a sheet mold and let it stand at room temperature for 6 hours to initially form a hydrogel preform and obtain a shaped gel.

[0052] Step 5, freeze-thaw strengthening: Freeze the shaped gel at -18℃ for 2 hours and thaw at room temperature for 6 hours to obtain the freeze-thawed hydrogel.

[0053] Step 6, Immersion strengthening: Immerse the freeze-thawed hydrogel in a saturated sodium citrate solution for 6 hours to finally obtain the ion thermoelectric gel.

[0054] Example 2 Step 1, Mixing and Dissolving: Add 1.2 g of polyvinyl alcohol, 0.24 g of sodium alginate and 0.34 g of calcium chloride to a mixture of 12 g of deionized water and 5 g of glycerol, and stir continuously at 80 °C for 4 hours to obtain a colorless, transparent and homogeneous solution A.

[0055] Step 2, sodium citrate adjustment: Slowly add 4.4 g of 30 wt% sodium citrate solution dropwise to solution A while stirring for 0.5 hours to obtain solution B.

[0056] Step 3, Introduce redox pairs: Add 0.09 g of potassium ferricyanide and 0.08 g of potassium ferrocyanide to solution B, and continue stirring for 0.4 hours to obtain solution C.

[0057] Step 4, let it stand and form: Pour solution C into a strip mold and let it stand at room temperature for 5 hours to initially form a hydrogel blank and obtain a shaped gel.

[0058] Step 5, freeze-thaw strengthening: Freeze the molded gel at -25°C for 3 hours and thaw at room temperature for 8 hours to obtain the freeze-thawed hydrogel.

[0059] Step 6, Immersion strengthening: Immerse the freeze-thawed hydrogel in a saturated sodium citrate solution for 4 hours to finally obtain the ion thermoelectric gel.

[0060] Example 3 Step 1, Mixing and Dissolving: Add 1.6 g of polyvinyl alcohol, 0.32 g of sodium alginate and 0.46 g of calcium chloride to a mixture of 16 g of deionized water and 7 g of glycerin, and stir continuously at 100 °C for 1 hour to obtain a colorless, transparent and homogeneous solution A.

[0061] Step 2, sodium citrate adjustment: Slowly add 4.5 g of 35 wt% sodium citrate solution dropwise to solution A while stirring for 0.5 hours to obtain solution B.

[0062] Step 3, Introduce redox pairs: Add 0.11 g of potassium ferricyanide and 0.1 g of potassium ferrocyanide to solution B, and continue stirring for 0.5 hours to obtain solution C.

[0063] Step 4, let it stand and solidify: Pour solution C into a customized mold and let it stand at room temperature for 6 hours to initially form a hydrogel blank, thus obtaining a solidified gel.

[0064] Step 5, freeze-thaw strengthening: Freeze the molded gel at -15℃ for 4 hours, then thaw at room temperature for 4 hours to obtain the freeze-thawed hydrogel.

[0065] Step 6, Immersion strengthening: Immerse the freeze-thawed hydrogel in a saturated sodium citrate solution for 8 hours to finally obtain the ion thermoelectric gel.

[0066] The following describes the material information of each material in each embodiment of the ion thermogel preparation method of the present invention.

[0067] (1) Polyvinyl alcohol: degree of hydrolysis 87.0~89.0 mol%, viscosity 800~1200 mPa·s. (2) Sodium alginate: viscosity 200±20 mPa·s. (3) Glycerol: analytical grade (AR), purity 99%, MW=92.09. (4) Sodium citrate: purity ≥98%, MW=258.07. (5) Calcium chloride: purity ≥99.99%, MW=110.98. (6) Potassium ferricyanide: analytical grade (AR), purity ≥99.5%, MW=329.25. (7) Potassium ferrocyanide: analytical grade (AR), purity 99.0%, MW=368.34.

[0068] Explanatoryly, in this invention, the degree of alcoholysis of polyvinyl alcohol can be adjusted within the range of 85.0~90.0 mol%, and the viscosity can be adjusted within the range of 600~1500 mPa. The viscosity of sodium alginate can be adjusted within the range of s; the viscosity can be adjusted from 180 to 250 mPa. Fine-tuning within the range of s can achieve similar technical results.

[0069] See Figure 2 The image shows the morphology of the ion thermoelectric gel prepared in Example 1. It can be seen that the ion thermoelectric gel is uniform in shape, free of impurities and bubbles, with a smooth surface and good flexibility, and excellent macroscopic forming effect.

[0070] See Figure 3 The microstructure of the ion thermoelectric gel prepared in Example 1 is shown by SEM (scanning electron microscope) at different magnifications. It can be seen that the gel has a connected porous structure with uniform pore size, dense double network cross-linking, and no pore collapse or component aggregation.

[0071] See Figure 4 The figure shows the thermoelectric voltage response of the ion thermoelectric gel prepared in Example 1 under different temperature differences. It can be seen that the thermoelectric voltage responds sensitively to the temperature difference without hysteresis. The larger the temperature difference, the higher the corresponding thermoelectric voltage response amplitude.

[0072] See Figure 5 The results of thermoelectric potential testing of the ion thermoelectric gel prepared in Example 1 are shown. It can be seen that the thermoelectric potential is highly linearly positively correlated with the temperature difference, the coefficient of determination of the fitting curve is high, the Seebeck coefficient is 1.46mV / K, and the output is regular and stable.

[0073] See Figure 6 The thermo-voltage response of the ion thermoelectric gel prepared in Example 1 under 6 cycles of heating and cooling is shown. It can be seen that the thermo-voltage curve does not show significant decay after six heating-cooling cycles, and the cycle stability is good.

[0074] See Figure 7 The results of the discharge test of the ion thermoelectric gel prepared in Example 1 with an external 500Ω resistor are shown. It can be seen that the gel discharge voltage drops steadily and slowly without sudden drop, and there is still a stable voltage output after 1 hour of continuous discharge.

[0075] See Figure 8 The tensile stress-strain curve of the ion thermoelectric gel prepared in Example 1 is shown. It can be seen that the gel has excellent tensile mechanical properties, with a tensile strength of 2.3 MPa and an elongation at break of over 500%.

[0076] See Figure 9The stress-strain curve of the ion thermoelectric gel prepared in Example 1 after 100 cycles of stretching at 100% strain is shown. It can be seen that after 100 cycles of stretching at 100% strain, the mechanical properties of the gel do not decrease significantly, and the cyclic recovery performance is excellent.

[0077] In another embodiment of the present invention, an ionic thermoelectric gel is provided, which is prepared by the above-described ionic thermoelectric gel preparation method.

[0078] See Figure 10 In another embodiment of the present invention, a flexible self-powered thermoelectric device is provided, which is prepared based on the above-mentioned ion thermoelectric gel 2 and achieves adjustable voltage and power and long-term stable power supply through structural innovation.

[0079] Specifically, the flexible self-powered thermoelectric device of the present invention includes several lattice units stacked in series, and a gas-liquid phase change layer 3 is provided between adjacent lattice units; the lattice unit includes several basic units distributed in lattice and connected in parallel; the basic unit includes the above-mentioned ion thermoelectric gel 2, and flexible electrodes 1 disposed at the upper and lower ends of the ion thermoelectric gel 2.

[0080] In one feasible embodiment, the gas-liquid phase change layer 3 includes a connected accommodating cavity and a flexible microchannel heat dissipation structure; the accommodating cavity is provided with a phase change working fluid that can undergo gas-liquid phase change within the operating temperature range of the flexible self-powered thermoelectric device, and the flexible microchannel heat dissipation structure is disposed on the side of the flexible self-powered thermoelectric device; the flexible electrode 1 is a gold foil, silver foil, copper foil, or carbon electrode.

[0081] Explained, the flexible self-powered thermoelectric device of this invention uses an ionogenic thermoelectric gel 2 with a dual network of polyvinyl alcohol and sodium alginate as the core functional layer. Flexible electrodes 1, such as alloy foil, silver foil, and carbon electrodes, are attached to opposite ends of the ionogenic thermoelectric gel 2, and fixed with conductive adhesive to form a basic "electrode-gel-electrode" sandwich unit. A hybrid structure of "parallel lattice connection + stacked series connection" is adopted: first, multiple basic units are arranged in parallel in a lattice pattern to achieve parallel connection, increasing the total current and output power; then, several parallel unit groups are stacked along the thickness direction to achieve series connection, increasing the total voltage. By adjusting the number and combination of units, the voltage and power requirements of different devices can be adapted as needed.

[0082] In this design, the outer surfaces of the upper and lower lattice units in the stacked structure are dual hot ends, adapting to the switching between the natural high temperatures of the outside world during the day (such as in summer without air conditioning) and the body temperature at night. A gas-liquid phase change layer 3 is added between adjacent lattice units as a constant-temperature cold end. The gas-liquid phase change layer 3 contains a low-boiling-point phase change working fluid and a flexible microchannel heat dissipation structure on the side. Through a closed-loop cycle of "evaporation heat absorption - flow heat dissipation - condensation reflux", the cold end temperature is kept constant, ensuring the stability of the temperature difference between the hot and cold ends. The overall device retains its flexible characteristics and can be cut into sheet, strip, or customized forms according to the application scenario to adapt to dynamic wearable and complex installation requirements.

[0083] This invention's flexible self-powered thermoelectric device can be applied in two typical scenarios. Scenario 1: Daily wearable multi-parameter physiological monitoring sensor. Fitting the wrist, arm, and other frequently used parts of the body, it generates electricity using the stable small temperature difference between the body surface and the phase-change constant-temperature cold junction, specifically for daily health monitoring. Based on a "parallel dot matrix for power enhancement + stacked series for voltage boosting" structure, it precisely matches the power and voltage requirements of simultaneous monitoring of multiple modules such as heart rate, movement trajectory, and body temperature fluctuations, eliminating the need for an external power source. The gel's anti-cyclic deformation and long-lasting water retention properties allow it to withstand daily stretching and bending movements, preventing performance degradation over long-term wear and ensuring continuous and stable sensor operation. Scenario 2: Dedicated self-powered device for extreme outdoor environments. Integrated into polar scientific research sensors, outdoor adventure recorders, and intelligent protective equipment for high-temperature operations, it addresses complex environments such as drastic day-night temperature differences and extreme high and low temperatures (e.g., -10~40℃). By switching between "external high temperature during the day / human body temperature at night" on a dual-heat end, coupled with a phase-change constant-temperature cold end, the temperature difference is ensured to be stable; the series-parallel hybrid structure can flexibly adjust the output parameters to adapt to the power threshold of the equipment; the flexible and customizable characteristics of the gel can adapt to complex installation forms, and the long-term water retention and deformation resistance can achieve stable self-powering without external power supply and in all weather conditions, solving the power supply problem in extreme environments.

[0084] In summary, the flexible self-powered thermoelectric device of this invention, based on ion thermoelectric gel 2, adopts a hybrid structure of "parallel lattice and stacked series". By adjusting the number and combination of basic units, the total voltage and output power can be optimized as needed to adapt to the power and voltage requirements of different human body sensing devices. This flexible self-powered thermoelectric device retains its flexible characteristics and can be cut into sheet, strip, or customized shapes to adapt to the complex installation requirements of different human body parts such as wrists and arms, as well as outdoor extreme environment devices. At the same time, the dual hot end switching and phase change constant temperature cold end design further broaden the application range of the material in multiple scenarios such as daily wearables, polar scientific research, and high-temperature operations. Compared with the limitation of the single application scenario of existing technologies, it has stronger practical value and promotion potential.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method of preparing an ionic pyroelectric gel, characterized by, include: Solution A is obtained by adding polyvinyl alcohol, sodium alginate and calcium chloride to a mixture of deionized water and glycerol; Sodium citrate is added to solution A to obtain solution B; Potassium ferricyanide and potassium ferrocyanide were added to solution B to obtain solution C; Solution C was allowed to stand and solidify to obtain a gel. The molded gel was frozen, thawed, and then soaked in sodium citrate solution to obtain an ion thermoelectric gel.

2. The method of claim 1, wherein the ionic thermoelectric gel is prepared by mixing the ionic thermoelectric material and the gel material in a ratio of 1 : 1 to 1 :

10. The process of adding polyvinyl alcohol, sodium alginate, and calcium chloride to a mixture of deionized water and glycerol to obtain solution A includes: By weight, 1.2-1.6 parts of polyvinyl alcohol, 0.24-0.32 parts of sodium alginate and 0.34-0.46 parts of calcium chloride are added to a mixture of 12-16 parts of deionized water and 5-7 parts of glycerol to obtain solution A.

3. The method of claim 2, wherein the ionothermogel is prepared by the steps of: The step of adding sodium citrate to solution A to obtain solution B includes: Add 3.4 to 4.5 parts by weight of sodium citrate solution to solution A to obtain solution B; The sodium citrate solution has a mass fraction of 25-35 wt%.

4. The method of claim 3, wherein the ionic thermoelectric gel is prepared by mixing the ionic thermoelectric material and the gel material in a ratio of 1 : 1 to 1 :

10. The step of adding potassium ferrocyanide and potassium ferrocyanide to solution B to obtain solution C includes: By mass, 0.17 to 0.21 parts of a mixture of potassium ferricyanide and potassium ferrocyanide are added to solution B to obtain solution C; wherein, the mass ratio of potassium ferricyanide to potassium ferrocyanide in the mixture is 1:0.8 to 1.

2.

5. The method of claim 1, wherein the ionothermogel is prepared by the steps of: The step of freezing the shaped gel, thawing it, and then soaking it in a sodium citrate solution includes: The molded gel is frozen at -25 to -15°C for 2 to 4 hours, thawed at room temperature for 4 to 8 hours, and then soaked in a saturated sodium citrate solution for 4 to 8 hours.

6. The method of claim 1, wherein the ionothermogel is prepared by the steps of: The process of adding polyvinyl alcohol, sodium alginate, and calcium chloride to a mixture of deionized water and glycerol to obtain solution A includes: Polyvinyl alcohol, sodium alginate, and calcium chloride are added to a mixture of deionized water and glycerol, and stirred continuously at 80-100°C for 1-4 hours to obtain solution A.

7. The method for preparing ion thermoelectric gel according to claim 1, characterized in that, The alcoholysis degree of the polyvinyl alcohol is 85~90 mol%, the viscosity of the polyvinyl alcohol is 600~1500 mPa s, and the viscosity of the sodium alginate is 180~250 mPa s.

8. An ionic pyroelectric gel, characterized in that, It was prepared according to the method for preparing ion thermoelectric gel according to any one of claims 1 to 7.

9. A flexible self-powered thermoelectric device, characterized in that, It includes several stacked and connected lattice units, with a gas-liquid phase change layer between adjacent lattice units; The lattice unit includes several basic units that are distributed in a lattice and connected in parallel with each other; The basic unit includes the ion thermoelectric gel as described in claim 8, and flexible electrodes disposed at the upper and lower ends of the ion thermoelectric gel.

10. The flexible self-powered pyroelectric device of claim 9, wherein, The gas-liquid phase change layer includes a connected accommodating cavity and a flexible microchannel heat dissipation structure; the accommodating cavity is provided with a phase change working fluid that can undergo gas-liquid phase change within the operating temperature range of the flexible self-powered thermoelectric device, and the flexible microchannel heat dissipation structure is provided on the side of the flexible self-powered thermoelectric device. The flexible electrode is a gold foil, silver foil, copper foil, or carbon electrode.

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