A dual-response hydrogel-based wet / thermal generator and its preparation method

Abstract

This invention discloses a dual-response hydrogel-based wet / thermal generator and its preparation method. The preparation method includes: mixing lauryl methacrylate, lithium chloride, tannic acid, lithium dodecyl sulfonate, phytic acid, glycerol, pure water, acrylamide, and 2-acrylamide-2-methylpropanesulfonic acid in a specific ratio, and stirring at 60°C to dissolve and obtain a premixed solution; adding a photoinitiator and a crosslinking agent to the premixed solution, mixing thoroughly, and then injecting into a mold; and polymerizing under 365nm ultraviolet light to obtain a dual-response hydrogel; this hydrogel can be matched and assembled with hydrophobic carbon cloth or graphite plates to construct a wet / thermal generator with three working modes: wet power generation, thermal power generation, and wet / thermal synergistic power generation. This generator combines wet power generation and ion thermoelectric functions and can be applied to self-powered human body sensor systems, motion monitoring, and information transmission.

Description

Technical Field

[0001] This invention relates to the field of low-grade energy capture and conversion technology, specifically to a dual-response hydrogel-based wet / thermal generator and its preparation method. Background Technology

[0002] The gradient distribution of humidity or temperature in the environment contains low-grade energy that can be utilized as a resource. Devices specifically designed to capture and convert such gradient energy are defined as Moisture-Electric Generators (MEGs) and Thermoelectric Generators (TEGs), respectively. In the field of low-grade energy resource utilization, the selection and design of functional materials are crucial. Among them, hydrogel-based materials have become ideal core materials for energy conversion devices due to their core advantages such as high water content, excellent flexibility, stretchability, and biocompatibility. In addition, by introducing ionic monomers and electrolyte components into the hydrogel system, it can be endowed with the ability to accommodate a large number of hydrated free ions, further expanding its application potential in the field of energy conversion.

[0003] Based on these characteristics, hydrogel-based materials occupy a core position in both MEG and TEG energy conversion devices. In the field of temperature-driven thermoelectric conversion, hydrogel-based ion thermoelectric (I&TE) generators can achieve high Seebeck coefficients and efficient response to temperature gradients by utilizing the free ions enriched within them and the ion migration rate selectivity achieved through polymer network structure modulation (derived from differences in ion type and size). Existing research has focused on strategies to improve the output performance of hydrogel-based I&TE generators, primarily including introducing salt compounds with significant differences in the mass of anions and cations into the hydrogel system, or doping with temperature-sensitive monomers and performing polymerization modification; furthermore, the thermoelectric potential induced by temperature difference can also achieve efficient energy capture by constructing built-in redox pairs within the hydrogel.

[0004] In the field of wet gas power generation, the three-dimensional network structure of hydrogels possesses excellent moisture retention properties, which can enhance the water vapor adsorption process and induce the formation of an ion concentration gradient within it. This ion concentration gradient is the core driving force of wet gas power generation. To further improve the performance of hydrogel-based MEGs, existing optimization strategies include introducing highly hygroscopic salts, photosensitizers, or constructing an asymmetric distribution structure of the polyelectrolyte network. These strategies can effectively enhance power generation performance or improve the long-term service stability of the device.

[0005] A comprehensive analysis of the mechanisms by which hydrogel-based materials function in MEGs and TEGs reveals that the directional migration of free ions in a gradient field (humidity / temperature), and the enhancement of the system's ion density and conductivity through the introduction of electrolyte monomers / inorganic components, are two core elements that have similar synergistic effects on both wet gas power generation and thermoelectric conversion. Based on this, designing and constructing a hydrogel-based device that can synergistically integrate wet gas power generation and ion thermoelectric conversion (i.e., a wet thermal generator IT&MEG) is theoretically feasible.

[0006] However, no such synergistically integrated devices have yet appeared in the current technology, and related research has not focused on the core principle of synergistic energy supply between moisture and heat—the direction of output from moisture power generation and ion thermoelectric conversion must be the same. Specifically, within the temperature and humidity range of the target operating environment, if the electromotive forces generated by moisture power generation and ion thermoelectric conversion are in opposite directions, the output performance will be mutually antagonistic, and synergistic energy supply cannot be achieved; only when the electromotive forces generated by the two are in the same direction can synergistic efficiency be achieved.

[0007] The human body's microenvironment, due to the combined effects of sweat evaporation / exhaled moisture release and the maintenance of a constant body temperature, typically exhibits higher temperature and humidity compared to the external environment, making it an ideal operating environment for IT&MEG devices. Existing research indicates that the positive electrode of common hydrogel-based humidification devices is often located on the side with lower humidity. Therefore, it can be inferred that to achieve the co-current superposition of thermoelectric electromotive force and humidified voltage, the thermoelectric conversion unit must have the lower-temperature side as the positive electrode, requiring the use of P-type thermoelectric materials to construct the ion thermoelectric conversion module. However, current technologies have neither developed P-type hydrogel-based materials suitable for this requirement nor formed a device structure capable of achieving synergistic humidification and thermal energy supply, significantly limiting the efficient capture and utilization of low-grade energy from the human body's surroundings. Summary of the Invention

[0008] To address the shortcomings of existing technologies, such as the lack of hydrogel-based devices that integrate wet power generation and ion thermoelectric conversion, the failure to consider the unidirectionality of output direction which prevents synergistic energy supply, and the difficulty in adapting to the low-grade energy capture requirements of the human microenvironment, this invention proposes a dual-response hydrogel-based wet / thermal generator and its preparation method.

[0009] To achieve the above objectives, the core technology of this invention lies in: by precisely controlling the raw material ratio and preparation process of the hydrogel, and combining the appropriate combination of the hydrogel and the electrode, the synergistic integration of moisture power generation and ion thermoelectric conversion and efficient energy output can be realized.

[0010] The specific technical concept of this invention is as follows: AM, AMPS, and LMA are selected as comonomers, LiCl and LDS are ion-conducting components, and PA and TA are functional modifiers. A water-glycerol binary mixed solvent system is used to construct a composite hydrogel with both high ion mobility and stable ion concentration gradient induction capability. Through a step-by-step process of "precise weighing of raw materials - pre-stirring and mixing - introduction of initiator / crosslinking agent - photo-initiated polymerization - demolding and molding", the integrity of the polymer network structure and the uniform dispersion of functional components are ensured. At the same time, key conditions such as stirring rate, reaction temperature, and photopolymerization parameters are strictly controlled to ensure the stability of hydrogel performance. The prepared dual-response hydrogel is adapted and bonded to the electrode to form a stable and efficient wet / thermal generator, in which the hydrogel is the core energy conversion unit. By adjusting the amount of comonomer added or replacing the ion-conducting components, a series of comparative hydrogel samples are prepared to achieve directional control and optimization of the device's energy conversion performance.

[0011] The technical solution of this invention also specifies the accuracy requirements for key process parameters: the raw material weighing accuracy is not less than 0.001g and the measurement accuracy is not less than 0.1mL; the temperature control accuracy during the pre-stirring stage is ±1℃ and the rotation speed control accuracy is ±10r / min; the ultraviolet lamp power fluctuation range during the photo-initiated polymerization stage is not more than ±1W and the irradiation time control accuracy is ±5min. The above-mentioned accuracy control ensures the repeatability of the preparation process and the consistency of product performance.

[0012] The technical solution adopted in this invention is as follows:

[0013] A method for preparing a dual-responsive hydrogel includes the following steps:

[0014] (1) Mix lauryl methacrylate, lithium chloride, tannic acid, lithium dodecyl sulfonate, phytic acid, glycerol and pure water, and add acrylamide and 2-acrylamide-2-methylpropanesulfonic acid. Stir and dissolve at 60°C to obtain a premixed solution.

[0015] (2) Add the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone and the crosslinking agent polyethylene glycol diacrylate to the premixed solution obtained in step (1), stir and mix evenly at room temperature to obtain a prepolymer solution;

[0016] (3) The prepolymer solution obtained in step (2) is transferred to a mold and photoinitiated polymerization is carried out under 365nm ultraviolet light to obtain a dual-response hydrogel.

[0017] In step (1), the amount of lauryl methacrylate is 3-9 parts by weight, the amount of lithium chloride is 30-90 parts by weight, the amount of tannic acid is 15-45 parts by weight, the amount of lithium dodecyl sulfonate is 7-21 parts by weight, the amount of phytic acid is 25-150 parts by weight, the amount of glycerol is 0-500 parts by weight, the amount of pure water is 500-1000 parts by weight, the amount of acrylamide is 35-200 parts by weight, and the amount of 2-acrylamide-2-methylpropanesulfonic acid is 0-500 parts by weight.

[0018] In step (2), the amount of the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone is 1 to 3 parts by weight, and the amount of the crosslinking agent polyethylene glycol diacrylate is 3 to 9 parts by weight.

[0019] A dual-response hydrogel was prepared by the above-described preparation method.

[0020] A dual-response hydrogel-based wet / thermal generator includes electrodes and the aforementioned dual-response hydrogel disposed in contact with the electrodes.

[0021] The electrode is any one of hydrophobic carbon cloth, carbon nanotube film, graphene paper, conductive nonwoven fabric, and graphite plate; the generator also includes copper wire as a hot-end auxiliary conductive electrode.

[0022] The dual-response hydrogel is fixed to the electrode surface or sandwiched between the two electrodes.

[0023] The dual-response hydrogel-based wet / thermal generator has wet power generation and / or ion thermoelectric functions.

[0024] The above-mentioned dual-response hydrogels and dual-response hydrogel-based wet / thermal generators are used in the fabrication of self-powered sensors.

[0025] A self-powered sensor comprising the aforementioned dual-response hydrogel or dual-response hydrogel-based wet / thermal generator.

[0026] The present invention has the following advantages:

[0027] (1) The dual-response hydrogel of the present invention adopts a water-glycerol binary mixed solvent system. With the help of the low mass characteristics of lithium ions and protons, it can obtain a high migration and diffusion rate in the ion transport channel formed by the anion polymer network. At the same time, it utilizes the characteristic that the anion polymer network can induce the formation of ion concentration gradient in a humid environment to achieve synergistic effect of humid power generation and ion thermoelectric conversion and comprehensive energy output. It breaks through the technical bottleneck of the existing technology that cannot synergistically utilize low-grade energy from multiple sources of temperature and humidity gradients, and greatly improves the capture and utilization rate and integrated utilization efficiency of low-grade energy in the environment.

[0028] (2) The dual-response hydrogel-based wet / thermal generator of the present invention can simultaneously achieve wet power generation and ion thermoelectric conversion performance under normal climatic conditions. In an environment with a relative humidity of 80%, the open-circuit voltage of the device in the single wet power generation mode can reach 0.634V, and the short-circuit current density can reach 38.54μA / cm. 2 Furthermore, the device boasts an ion thermoelectric Seebeck coefficient as high as 15.4 mV / K, demonstrating excellent energy conversion performance and providing reliable performance support for practical industrial applications.

[0029] (3) The core functional material of the dual-response hydrogel-based wet / thermal generator of the present invention, namely the dual-response hydrogel, has excellent biocompatibility. It can be used to build a human self-powered sensor system, which is adapted to the energy harvesting requirements of the temperature and humidity gradient of the microenvironment of the human skin surface. It can be widely used in wearable application scenarios such as motion sensing, Morse code communication, and low-grade energy harvesting around the human body. It has rich application scenarios, strong adaptability, and expands the application boundaries of wearable self-powered technology.

[0030] (4) This invention focuses on the resource utilization of low-grade energy in the temperature and humidity gradient between the environmental medium and the microenvironment of human skin surface and the external atmosphere. It is in line with the industrial development trend of low-grade energy resource utilization and green energy development, and at the same time meets the development needs of wearable self-powered technology. The technical solution is highly practical and has broad industrialization prospects, providing a new technical solution and implementation path for the field of low-grade energy resource utilization and wearable self-powered technology. Attached Figure Description

[0031] Figure 1 : Technical flowchart of the present invention.

[0032] Figure 2 Example 4: Biocompatibility of dual-response hydrogels.

[0033] Figure 3 Example 4: Scanning electron microscope (SEM) image of the cross section of the dual-response hydrogel.

[0034] Figure 4 Ionic thermo-voltage response curves of the dual-response hydrogel-based wet / thermal generator in Example 4 under the thermal power generation mode test configuration.

[0035] Figure 5 The effect of the number of units in series on the open-circuit voltage of the dual-response hydrogel-based wet / thermal generator in Example 4 under the wet power generation mode test configuration and a physical diagram of the 24-unit series connection.

[0036] Figure 6 The effect of external load resistance on the power density of the dual-response hydrogel-based wet / thermal generator in Example 4 under the wet power generation mode test configuration.

[0037] Figure 7 The effect of temperature difference on the open-circuit voltage, temperature monitoring values ​​of various parts, and additional ionic thermal voltage of the dual-response hydrogel-based wet / thermal generator in the test configuration of the wet and heat co-generation mode in Example 4.

[0038] Figure 8 The effects of compressive strain and temperature on the rate of change of current and cycle stability of the dual-response hydrogel-based wet / thermal generator in the wet power generation mode test configuration of Example 4.

[0039] Figure 9 Example 4: Motion sensing response diagram of a dual-response hydrogel-based wet / thermal generator attached to different joints of the human body under the wet power generation mode test configuration.

[0040] Figure 10 Example 4: Morse code communication signal output diagram of the dual-response hydrogel-based wet / thermal generator when it is attached to the joint of a human finger under the wet power generation mode test configuration. Detailed Implementation

[0041] The technical solutions of the present invention will be described in detail below through embodiments. The following embodiments are merely exemplary and can only be used to explain and illustrate the technical solutions of the present invention, and should not be construed as limiting the technical solutions of the present invention.

[0042] The dual-response hydrogel-based wet / thermal generator of this invention refers to a functional device that uses the dual-response hydrogel of this invention as the core power generation unit, and achieves wet power generation, thermal power generation, or wet / thermal synergistic power generation by constructing an asymmetric hygroscopic structure or temperature gradient structure. Performance is characterized using the following three configurations according to different operating modes:

[0043] Wet power generation mode test configuration and performance testing: The dual-response hydrogel was cut into 3mm thick square sheets, and a hydrophobic carbon cloth of matching size was selected as the current collector. The hydrogel sheet was flatly attached to one side of the hydrophobic carbon cloth, and after gently pressing to remove interfacial air bubbles, it was placed at room temperature for 1 hour to allow the hydrogel sheet and the hydrophobic carbon cloth to bond firmly, thus obtaining the wet power generation mode test sample. The test sample was placed in a constant temperature and humidity chamber at 25℃ and 80% relative humidity, and exposed for 15 minutes to allow the system to reach humidity equilibrium. The open-circuit voltage and short-circuit current density of the generator were recorded using an electrochemical workstation.

[0044] Thermal power generation mode test configuration and performance testing: A 3mm thick square sheet of dual-response hydrogel was cut, and two matching graphite plates were selected as current collector electrodes. The hydrogel sheet was smoothly attached between the two graphite plate electrodes. After gently pressing to remove air bubbles at the interface, the gaps on all four sides between the two graphite plates were sealed with silicone rubber sealant, extending the sealant to cover the edges of the upper and lower graphite plates to form a complete edge seal to isolate external interference, thus obtaining the thermal power generation mode test sample. The test sample was placed in a constant temperature and humidity chamber, with the chamber environment adjusted to a relative humidity of 80% and the temperature at the cold end operating temperature. One graphite plate electrode of the test sample served as the hot end, maintained at a constant temperature of 37℃ by an electric heater; the other graphite plate electrode served as the cold end, with its temperature precisely regulated by a Peltier-circulating water cooling temperature control system. The thermally induced open-circuit voltage was recorded when the temperature difference between the hot and cold ends was ΔT = 0K, 10K, 20K, and 30K. During measurement, the hot and cold electrodes were first adjusted to a preset temperature. After both electrode temperatures stabilized, the constant temperature gradient was maintained for 1 hour to allow the thermal diffusion of mobile ions inside the hydrogel to reach a steady-state equilibrium. The open-circuit voltage was then recorded using the cold end as the positive voltage electrode. The slope of the obtained straight line, which was linearly fitted to the temperature difference ΔT using the thermally induced open-circuit voltage, is the ion thermoelectric Seebeck coefficient of the generator.

[0045] Test configuration and performance of the humid-heat co-generation mode: The dual-response hydrogel was cut into 3mm thick square sheets. A copper wire was selected as the hot-end electrode, and a hydrophobic carbon cloth of matching size was selected as the cold-end electrode and thermally conductive layer. An electric heater was placed in a constant temperature and humidity chamber with its heating surface facing upwards and an insulating thermally conductive protective layer (such as an insulating thermally conductive silicone pad) was attached to it. One end of the copper wire was placed on the upper surface of the insulating thermally conductive protective layer, and the other end was led out to the electrochemical workstation outside the chamber. The lower surface of the hydrogel sheet was flatly attached to the surface of the insulating thermally conductive protective layer and covered the contact end of the copper wire. The upper surface was flatly attached to the surface of the hydrophobic carbon cloth. After gently and evenly pressing to remove air bubbles at each interface, the upper surface of the hydrophobic carbon cloth was completely exposed to the ambient air, thus obtaining the humid-heat co-generation test sample. The test sample was placed in a constant temperature and humidity chamber, and the environment was adjusted to a temperature of 17℃ and a relative humidity of 80%. After the temperature and humidity inside the chamber stabilized, the hot end was heated to 37℃ by the electric heater and kept constant. After the temperature and humidity of the system stabilized, the state was maintained for another 1 hour to allow the migration of mobile ions inside the hydrogel to reach steady-state equilibrium. The open-circuit voltage and short-circuit current density of the generator were recorded using an electrochemical workstation.

[0046] Example 1:

[0047] A method for preparing a dual-responsive hydrogel includes the following steps:

[0048] S1: Preparation of premixed solution: Mix 3.8 parts by weight of lauryl methacrylate (LMA), 30 parts by weight of lithium chloride (LiCl), 15 parts by weight of tannic acid (TA), 13.6 parts by weight of lithium dodecyl sulfonate (LDS), 150 parts by weight of phytic acid (PA), 250 parts by weight of glycerol and 250 parts by weight of pure water, then add acrylamide (AM) and 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and stir magnetically at 600 r / min for 2 h at 60 °C to obtain the premixed solution.

[0049] S2: Preparation of prepolymer solution: Add 1 part by weight of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone (I2959) and 3 parts by weight of polyethylene glycol diacrylate (PEGDA) to the premixed solution obtained in step S1, and stir magnetically at 600 r / min for 15 min at room temperature to obtain the prepolymer solution.

[0050] S3: The prepolymer solution obtained in step S2 is injected into a glass mold and irradiated for 2 hours at room temperature under a UV lamp with a wavelength of 365nm and a power of 24W to obtain P(AM-co-AMPS-co-LMA)@PA / TA / LDS / LiCl composite hydrogel, i.e., a dual-response hydrogel.

[0051] To investigate the effects of AM and AMPS dosage on the power generation performance of a dual-response hydrogel-based wet / thermal generator, the dosages of LMA, LiCl, TA, LDS, PA, glycerol, pure water, I2959, and PEGDA were kept constant. Only the dosages of AM and AMPS were adjusted to prepare a series of dual-response hydrogels with different formulations. The performance of the corresponding hydrogel-based wet / thermal generators in Example 1 was characterized according to the aforementioned wet power generation and thermal power generation test configurations. The test results are shown in the table below. With the increase of AMPS dosage and the decrease of AM dosage, the wet power generation open-circuit voltage of the generator showed a trend of first increasing and then decreasing, reaching a peak of 0.714V when AMPS = 170 parts by weight and AM = 116.5 parts by weight. The wet power generation short-circuit current density gradually increased, reaching a maximum value of 50.04 μA·cm when AMPS = 510 parts by weight and AM = 0 parts by weight. -2As the amount of AM increases and the amount of AM decreases, the Seebeck coefficient of the ion thermoelectric generator initially increases, reaching a maximum positive value of 15.89 mV / K when AM = 58 parts by weight and AM = 340 parts by weight. Further increasing the amount of AM and decreasing the amount of AM causes the ion thermoelectric Seebeck coefficient to turn negative. This confirms that the dual-response hydrogel exhibits typical characteristics of a p-type ion thermoelectric material, where internal cations preferentially migrate and accumulate towards the cold end under the drive of a temperature gradient, thus forming a positive potential at the cold end. When the amount of AM is further increased to 510 parts by weight and the amount of AM is 0 parts by weight, the ion thermoelectric Seebeck coefficient turns negative, and the material exhibits n-type ion thermoelectric characteristics. At this ratio, the electromotive force generated by moisture power generation and ion thermoelectric conversion is in opposite directions, leading to antagonistic output performance and preventing the realization of synergistic moisture-heat energy supply. The ratio of AM=58 parts by weight and AMPS=340 parts by weight achieves optimal positive ion thermoelectric performance while maintaining a high wet power generation open-circuit voltage and wet power generation short-circuit current density, making it the best ratio for achieving wet and heat co-generation.

[0052]

[0053] Example 2:

[0054] A method for preparing a dual-responsive hydrogel includes the following steps:

[0055] S1: Preparation of premixed solution: Mix LMA, 30 parts by weight of LiCl, 15 parts by weight of TA, 13.6 parts by weight of LDS, 150 parts by weight of PA, 250 parts by weight of glycerol and 250 parts by weight of pure water, then add 58 parts by weight of AM and 340 parts by weight of AMPS, and stir magnetically at 600 r / min for 2 h at 60℃ to obtain the premixed solution.

[0056] S2: Preparation of prepolymer solution: Add 1 part by weight of I2959 and 3 parts by weight of PEGDA to the premixed solution obtained in step S1, and stir magnetically at 600 r / min for 15 min at room temperature to obtain the prepolymer solution.

[0057] S3: The prepolymer solution obtained in step S2 is injected into a glass mold and irradiated for 2 hours at room temperature under a UV lamp with a wavelength of 365nm and a power of 24W to obtain P(AM-co-AMPS-co-LMA)@PA / TA / LDS / LiCl composite hydrogel, i.e., a dual-response hydrogel.

[0058] To investigate the effect of LMA dosage on the power generation performance of a dual-response hydrogel-based wet / thermal generator, the dosages of other components such as LiCl, TA, LDS, PA, glycerol, pure water, AM, AMPS, I2959, and PEGDA were kept constant, and only the amount of LMA was adjusted to prepare a series of dual-response hydrogels with different formulations. The performance of the corresponding hydrogel-based wet / thermal generators in Example 2 was characterized according to the aforementioned wet power generation and thermal power generation test configurations. The test results are shown in the table below. When LMA = 2.55 parts by weight, the open-circuit voltage of the generator reached its highest value of 0.799V; when LMA = 3.8 parts by weight, the short-circuit current density of the wet power generation was the highest, at 38.54 μA·cm. -2 The Seebeck coefficient of the ion thermoelectric generator generally decreases with increasing LMA dosage. Overall, while LMA = 3.8 parts by weight slightly reduces the wet power generation open-circuit voltage and the ion thermoelectric Seebeck coefficient, it achieves the maximum wet power generation short-circuit current density, significantly enhancing the device's output power potential, while maintaining high positive ion thermoelectric performance. This results in the optimal balance between thermoelectric response capability and wet power output.

[0059]

[0060] Example 3:

[0061] A method for preparing a dual-responsive hydrogel includes the following steps:

[0062] S1: Preparation of premixed solution: Mix 3.8 parts by weight of LMA, 30 parts by weight of LiCl, 15 parts by weight of TA, 13.6 parts by weight of LDS, 150 parts by weight of PA, 250 parts by weight of glycerol and 250 parts by weight of pure water, then add 58 parts by weight of AM and 340 parts by weight of AMPS, and stir magnetically at 600 r / min for 2 h at 60℃ to obtain the premixed solution.

[0063] S2: Preparation of prepolymer solution: Add 1 part by weight of I2959 and 3 parts by weight of PEGDA to the premixed solution obtained in step S1, and stir magnetically at 600 r / min for 15 min at room temperature to obtain the prepolymer solution.

[0064] S3: The prepolymer solution obtained in step S2 is injected into a glass mold and irradiated for 2 hours at room temperature under a UV lamp with a wavelength of 365nm and a power of 24W to obtain P(AM-co-AMPS-co-LMA)@PA / TA / LDS / LiCl composite hydrogel, i.e., a dual-response hydrogel.

[0065] To investigate the effect of cationic components on the power generation performance of a dual-response hydrogel-based wet / thermal generator, while keeping other raw materials and their amounts constant, only LiCl and LDS were replaced with an equimolar amount of an inorganic salt-surfactant combination. Specifically, the following settings were used: ① Replaced with SDS (sodium dodecylbenzenesulfonate) and NaCl (sodium chloride); ② Replaced with MDS (magnesium sodium dodecylbenzenesulfonate) and MgCl2 (magnesium chloride). The above preparation process was repeated sequentially to obtain dual-response hydrogels with different cationic components. The performance of the corresponding hydrogel-based wet / thermal generators in Example 3 was characterized according to the aforementioned wet power generation mode and thermal power generation mode test configurations. The test results are shown in the table below. When using the LiCl+LDS combination, the generator's wet power generation open-circuit voltage, wet power generation short-circuit current density, and ion thermoelectric Seebeck coefficient all reached optimal values, which were 0.654 V, 37.61 μA·cm, and respectively. -2 The efficiency was 13.98 mV / K; after replacing the cation component with NaCl+SDS or MgCl2+MDS, all three key performance indicators decreased significantly. This indicates that the LiCl+LDS combination can better enhance the ion transport and energy conversion capabilities of the generator, making it the preferred cation system for achieving efficient wet-heat co-generation.

[0066]

[0067] Example 4:

[0068] A method for preparing a dual-responsive hydrogel includes the following steps:

[0069] S1: Preparation of premixed solution: Mix 3.8 parts by weight of LMA, 30 parts by weight of LiCl, 15 parts by weight of TA, 13.6 parts by weight of LDS, 150 parts by weight of PA, 250 parts by weight of glycerol and 250 parts by weight of pure water, then add 58 parts by weight of AM and 340 parts by weight of AMPS, and stir magnetically at 600 r / min for 2 h at 60℃ to obtain the premixed solution.

[0070] S2: Preparation of prepolymer solution: Add 1 part by weight of I2959 and 3 parts by weight of PEGDA to the premixed solution obtained in step S1, and stir magnetically at 600 r / min for 15 min at room temperature to obtain the prepolymer solution.

[0071] S3: The prepolymer solution obtained in step S2 is injected into a glass mold and irradiated for 2 hours at room temperature under a UV lamp with a wavelength of 365nm and a power of 24W to obtain P(AM-co-AMPS-co-LMA)@PA / TA / LDS / LiCl composite hydrogel, i.e., a dual-response hydrogel.

[0072] To investigate the effect of ambient humidity on the power generation performance of the dual-response hydrogel-based wet / thermal generator of Example 4, the environmental parameters of the aforementioned wet power generation mode test configuration and wet / thermal synergistic power generation mode test configuration were adjusted as follows: only the relative humidity (RH) in the test environment was changed, set to 60%, 70%, 80%, and 90% respectively, while the remaining test steps, equipment connection methods, and temperature conditions remained consistent with the above. The results are shown in the table below. As the ambient humidity increased from 60% to 90%, the open-circuit voltage of the generator wet power generation showed a trend of first increasing and then decreasing, reaching a peak of 0.740V at 70% humidity, and the wet power generation short-circuit current density reached its maximum value of 38.54μA·cm at 80% humidity. -2 The open-circuit voltage of the generator in humid and hot co-generation decreases slightly with increasing humidity but remains stable overall, while the short-circuit current density of the generator in humid and hot co-generation continues to increase with increasing humidity.

[0073]

[0074] To investigate the effect of ambient temperature on the power generation performance of the dual-response hydrogel-based wet / thermal generator of Example 4, the environmental parameters of the aforementioned wet power generation mode test configuration were adjusted as follows: only the temperature in the test environment was changed, set to 5℃, 15℃, 25℃, 35℃, and 45℃ respectively, while the remaining test steps, equipment connection methods, and humidity conditions remained consistent with the above. The results are shown in the table below. As the ambient temperature increased from 5℃ to 45℃, the wet power generation open-circuit voltage and wet power generation short-circuit current density both showed a trend of first increasing and then decreasing. The wet power generation open-circuit voltage reached its highest value of 0.825V at 35℃, and the wet power generation short-circuit current density reached its peak value of 59.22μA·cm at 35℃. -2 .

[0075]

[0076] To assess the biocompatibility of the material, a hydrogel extract was first prepared: the dual-response hydrogel prepared in Example 4 was immersed in DMEM complete culture medium at a mass-to-volume ratio of 1 g:10 mL, sealed, and placed in a 37°C, 5% CO2 cell culture incubator for 24 h in the dark. After extraction, the extract was filtered through a 0.22 μm sterile filter to obtain a stock solution of hydrogel extract, which was then diluted with complete culture medium to 2.5 mg / mL and stored at 4°C for later use. L929 cells in the logarithmic growth phase were digested with trypsin and gently pipetted to disperse them fully. The cell suspension was transferred to centrifuge tubes and centrifuged at 1000 rpm for 5 min. The supernatant was discarded, and the cells were resuspended in fresh culture medium. The cell suspension was seeded into six-well plates, with 1.5 mL added to each well, and cultured overnight in a 37°C, 5% CO2 cell culture incubator to allow the cells to adhere. The experiment was divided into two groups: a blank control group (Control) and a group treated with 2.5 mg / mL hydrogel extract. After cell adhesion, the original culture medium in each well was aspirated, and the cells were washed once with PBS buffer. Then, equal volumes of the corresponding concentration of hydrogel extract were added, and the cells were incubated for 48 hours. After incubation, the six-well plates were removed, the drug-containing culture medium was aspirated, and the cells were washed three times with PBS buffer. Calcein / PI working solution was diluted 1:1000 with complete culture medium, and 1 mL of the diluent was added to each well. The plates were incubated at 37°C in the dark for 20 minutes. After staining, the working solution was aspirated, and the cells were washed three times with PBS, retaining approximately 1 mL of PBS in each well to prevent sample drying. Finally, images of live cells (green fluorescence) and dead cells (red fluorescence) were acquired in the same field of view under a fluorescence microscope, and Merge overlay analysis was performed. The results are as follows: Figure 2 As shown in the figure, the biresponsive hydrogel exhibits good biocompatibility.

[0077] To characterize the internal microstructure of the hydrogel, scanning electron microscopy (SEM) was used for observation. The sample preparation steps were as follows: The dual-response hydrogel prepared in Example 4 was quenched with liquid nitrogen to fully expose its internal network structure, and then freeze-dried in a freeze dryer for 48 hours. The freeze-dried cross-section sample was taken, fixed to the sample stage with conductive adhesive, and sputter-coated with gold for 90 seconds to enhance conductivity. SEM observation was performed using a FEI Quanta scanning electron microscope with an accelerating voltage of 10 kV and a beam current of 7 mA. The test results are as follows: Figure 3 As shown in the figure, the dual-response hydrogel exhibits a dense porous framework structure.

[0078] The dual-response hydrogel prepared in Example 4 was used to characterize the performance of the corresponding hydrogel-based wet / thermal generator according to the test configuration of the aforementioned thermal power generation mode. The test results are as follows: Figure 4 As shown in the figure, the generator exhibits a clear ionic thermoelectric response characteristic to changes in temperature difference.

[0079] The dual-response hydrogel prepared in Example 4 was used to characterize the power generation performance of the corresponding hydrogel-based wet / thermal generator, referring to the aforementioned wet power generation mode test configuration. To examine the voltage amplification performance of the device, multiple wet power generation test samples were connected in series, one end to the other. That is, the carbon cloth end of the previous sample was connected to the gel end of the next sample via a copper wire, and so on, to complete the array assembly, forming a series power generation array with a maximum of 24 units. This series array was placed in a constant temperature and humidity chamber at 25°C and 80% relative humidity for 15 minutes to allow the system to reach humidity equilibrium. The open-circuit voltage of the generator was recorded using an electrochemical workstation. The test results are as follows: Figure 5 As shown in the figure, the open-circuit voltage of the device can be significantly increased by connecting multiple power generation units in series.

[0080] The dual-response hydrogel prepared in Example 4 was used, and the power generation performance of the corresponding hydrogel-based wet / thermal generator was characterized according to the aforementioned wet power generation mode test configuration. The device was placed in an environment with room temperature (25°C) and relative humidity of 80%, and a programmable resistor box was connected externally to the generator output terminal as a variable load. By adjusting the resistance box to change the load resistance value, after the device output stabilized for 15 minutes at each resistance value, the corresponding output voltage was recorded, and the output power under different load conditions was calculated accordingly. The test results are as follows. Figure 6 As shown in the figure, the generator can reach its maximum output power by adjusting the size of the external load.

[0081] The dual-response hydrogel prepared in Example 4 was used, and the power generation performance of the corresponding hydrogel-based wet / thermal generator was characterized according to the aforementioned wet / thermal synergistic power generation mode test configuration. The hot end was kept constant at 37°C using an electric heater, and the ambient temperature was adjusted to 37°C, 27°C, 17°C, and 7°C using a constant temperature and humidity chamber to create different temperature differences. After the system stabilized, the reference voltage at a temperature difference of 0K was recorded. The thermal voltage change curve was obtained by subtracting this reference voltage, and the temperature of each part was monitored simultaneously. The test results are as follows: Figure 7 As shown in the figure, the generator, in addition to achieving stable wet power output, can further generate additional ion thermoelectric voltage by changing the temperature gradient.

[0082] Using the dual-response hydrogel prepared in Example 4, a wet / thermal generator sample was prepared according to the aforementioned wet power generation mode test configuration, and its piezoresistive sensing performance under compression was characterized. The sample was connected to a digital source meter via copper wires and placed on a multifunctional fabric tensile testing platform. In the strain gradient test, a compressive strain ranging from 5% to 60% was applied to the sample at room temperature, with the pressure increasing in increments of 5% each time, and the relative current change rate under different strains was recorded. In the cyclic compression stability test, a specific compression ratio was selected for multiple cycles of compression-release to examine the response repeatability. In the variable-temperature piezoresistive response test, the sample was kept at a constant compressive strain of 60% and attached to the surface of a cold stage cooled by a circulating water cooling device. The sample body temperature was changed by adjusting the temperature of the cold stage, and the relative current change rate of compression cycles at different temperatures was measured. The results are as follows: Figure 8 As shown in the figure, the generator exhibits stable and reversible cyclic compression response characteristics over a wide range of compressive strains and under different operating temperatures.

[0083] Using the dual-response hydrogel prepared in Example 4, a corresponding wet / thermal generator was fabricated according to the aforementioned wet power generation mode test configuration. To verify the application potential of this device in the field of wearable motion monitoring, the gel side was attached to joints such as the fingers, wrists, elbows, and ankles of the human body, and secured with medical tape. The device was connected to a digital source meter via copper wires. After the readings stabilized, the subject was instructed to repeatedly bend the corresponding joints with the same amplitude, and the device's current change rate response to different joint movements was recorded in real time. The results are as follows: Figure 9 As shown in the figure, the device can achieve stable and real-time detection and response to human joint movements. To further expand the monitoring application scenarios of this device, the gel side was attached to the human finger joint and fixed with medical tape. It was connected to a digital source meter via a copper wire. After the reading stabilized, the finger joint was controlled to bend at two different amplitudes according to the Morse code meter, corresponding to the "dot" and "line" of Morse code respectively. The corresponding electrical signal response of the device was recorded, and the results are shown in the figure. Figure 10 As shown in the figure, the generator can output a matching Morse code signal based on the differences in the amplitude of human body movements.

[0084] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a dual-responsive hydrogel, characterized in that: Includes the following steps: (1) Mix lauryl methacrylate, lithium chloride, tannic acid, lithium dodecyl sulfonate, phytic acid, glycerol and pure water, and add acrylamide and 2-acrylamide-2-methylpropanesulfonic acid. Stir and dissolve at 60°C to obtain a premixed solution. (2) Add the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone and the crosslinking agent polyethylene glycol diacrylate to the premixed solution obtained in step (1), stir and mix evenly at room temperature to obtain a prepolymer solution; (3) The prepolymer solution obtained in step (2) is transferred to a mold and photoinitiated polymerization is carried out under 365nm ultraviolet light to obtain a dual-response hydrogel.

2. The preparation method according to claim 1, characterized in that: In step (1), the amount of lauryl methacrylate is 3-9 parts by weight, the amount of lithium chloride is 30-90 parts by weight, the amount of tannic acid is 15-45 parts by weight, the amount of lithium dodecyl sulfonate is 7-21 parts by weight, the amount of phytic acid is 25-150 parts by weight, the amount of glycerol is 0-500 parts by weight, the amount of pure water is 500-1000 parts by weight, the amount of acrylamide is 35-200 parts by weight, and the amount of 2-acrylamide-2-methylpropanesulfonic acid is 0-500 parts by weight.

3. The preparation method according to claim 1 or 2, characterized in that: In step (2), the amount of the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone is 1 to 3 parts by weight, and the amount of the crosslinking agent polyethylene glycol diacrylate is 3 to 9 parts by weight.

4. A dual-responsive hydrogel, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 3.

5. A dual-response hydrogel-based wet / thermal generator, characterized in that: Includes electrodes and a dual-response hydrogel as described in claim 4, which is disposed in contact with the electrodes.

6. The dual-response hydrogel-based wet / thermal generator according to claim 5, characterized in that: The electrode is any one of hydrophobic carbon cloth, carbon nanotube film, graphene paper, conductive nonwoven fabric, and graphite plate; the generator also includes copper wire as a hot-end auxiliary conductive electrode.

7. The dual-response hydrogel-based wet / thermal generator according to claim 5, characterized in that: The dual-response hydrogel is fixed to the electrode surface or sandwiched between the two electrodes.

8. The dual-response hydrogel-based wet / thermal generator according to claim 5, characterized in that: The dual-response hydrogel-based wet / thermal generator has wet power generation and / or ion thermoelectric functions.

9. The application of the dual-response hydrogel of claim 4 and the dual-response hydrogel-based wet / thermal generator of any one of claims 5 to 8 in the preparation of self-powered sensors.

10. A self-powered sensor, characterized in that: The generator comprises the dual-response hydrogel of claim 4 or the dual-response hydrogel-based wet / thermal generator of any one of claims 5 to 8.

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