A hydrogel with high weather resistance, high responsivity and stability, and a preparation method and application thereof

Abstract

This invention belongs to the field of temperature sensor technology, and discloses a hydrogel with high weather resistance, high responsiveness and stability, its preparation method and application, which solves the technical problems of poor weather resistance, low responsiveness and poor stability of existing hydrogel temperature sensors in practical applications. The steps are as follows: (1) Add acrylamide and gelatin to the salt solution, and after they dissolve, obtain solution a; then add N,N'-methylenebisacrylamide solution and ammonium persulfate solution to obtain a mixed solution, and obtain hydrogel through cross-linking reaction; (2) Add ethylene glycol and glycerol to the salt solution to obtain a mixed alcohol washing solution; (3) Immerse the above hydrogel in the mixed alcohol washing solution, take it out and treat it at 30-40℃ for 8-10 h, and obtain the hydrogel. The use of the mixed alcohol washing solution can improve the permeation efficiency and distribution uniformity, optimize the balance between antifreeze and dynamic response performance, inhibit phase separation and crystallization tendency and stabilize ionic strength, and further improve the stability of use.

Description

Technical Field

[0001] This invention relates to the field of temperature sensor technology, and more particularly to a method for preparing a hydrogel. Background Technology

[0002] Body temperature is a fundamental vital sign, and its stability is crucial for enzyme activity, metabolism, immunity, and the nervous system. Under normal conditions, the hypothalamus regulates body temperature to maintain it between 36.5-37.2°C. Abnormalities, such as fever or hypothermia, often indicate problems such as infection, inflammation, or metabolic disorders. Body temperature is a sensitive health warning signal, especially in children, the elderly, and postoperative patients. Accurate monitoring of body temperature helps in the early detection and intervention of diseases and is of great significance in intensive care, postoperative care, infectious disease control, and daily health management.

[0003] With the rapid development of the global economy and the continuous advancement of technology, the demand for temperature sensors is constantly increasing. Temperature sensors have received widespread attention in many fields, including temperature monitoring, healthcare, medical diagnostics, signal monitoring, tissue engineering, smart wearable devices, and intelligent robots, demonstrating significant application value in the medical and health sectors. However, traditional temperature sensors can affect users' daily comfort and mobility, and cannot meet high-performance requirements. Hydrogels, as an ideal sensing material, possess excellent biocompatibility, good mechanical properties, and outstanding electrical conductivity, enabling them to respond rapidly to changes in external temperature and showing broad application prospects.

[0004] However, current hydrogel temperature sensors still face many bottlenecks in their progress towards practical applications, mainly in the following aspects:

[0005] (1) Hydrogels are prone to dehydration when in contact with the outside world, which leads to distortion of sensor response signals, elastic deformation, structural damage and performance degradation.

[0006] (2) When a hydrogel sensor is attached to the human body, it must withstand the deformation of the wearing area and the action of external forces. However, the existing hydrogels are not tough and durable enough, and it is difficult to adapt to and recover from deformation under the action of external forces. Therefore, their application in dynamic scenarios is greatly limited.

[0007] (3) Its response mechanism is usually based on thermocouples, which has extremely low responsivity and weak ability to detect subtle temperature changes, making it difficult to meet the requirements of high-precision temperature monitoring.

[0008] (4) The output signal is easily affected by environmental interference, electromagnetic noise and contact resistance, resulting in poor stability of continuous monitoring and insufficient promotion, which greatly affects its application in actual scenarios.

[0009] The aforementioned prominent problems severely limit the practical application of hydrogel strain sensors, and solving these problems has become the focus of current research in this field. While the existing technology CN115873275A has improved the anti-dehydration and antifreeze properties of hydrogels, it still has many shortcomings. This technology uses a single system of glycerol, resulting in a low permeation rate and uneven distribution of glycerol in the hydrogel matrix. Furthermore, ion loss easily leads to fluctuations in the electrical signal, making it unsuitable for long-term use. In addition, the use of glycerol alone can easily cause response delays. Moreover, since this technology uses traditional resistance as the response signal, its ability to detect temperature changes is weak, resulting in insufficient responsivity. Furthermore, this technology relies solely on Fe... 3+ Cross-linking improves mechanical properties, but the resulting hydrogels generally have poor extensibility and elasticity, are easily damaged, and their weather resistance and stability are difficult to meet the requirements of practical applications. Summary of the Invention

[0010] To address the three major shortcomings of existing hydrogel temperature sensors in practical applications—poor weather resistance, low responsiveness, and poor stability—this invention proposes a hydrogel with high weather resistance, high responsiveness, and stability, along with its preparation method and applications.

[0011] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0012] A method for preparing a hydrogel with high weather resistance, high responsiveness, and stability, comprising the following steps:

[0013] (1) Add acrylamide and gelatin to the salt solution and wait for them to dissolve to obtain solution a; then add N,N'-methylenebisacrylamide (MBA) solution and ammonium persulfate (APS) solution to solution a, and stir at room temperature for 20-30 minutes on a magnetic stirrer to fully mix the components to obtain a mixed solution; finally, slowly pour the mixed solution into a pre-prepared mold and place the mold in an oven at a certain temperature for a crosslinking reaction for a certain time. After the reaction is completed, take it out to obtain hydrogel.

[0014] (2) Weigh a certain amount of salt using a balance and add it to a beaker. Then add a certain amount of purified water to the beaker and place it at 50-60℃ and stir for 10-25 min until the salt is completely dissolved to obtain a salt solution. Then add ethylene glycol and glycerol to the salt solution in sequence and stir for a certain time to obtain a uniform mixed alcohol washing solution. Pour the mixed alcohol washing solution into a petri dish and soak the hydrogel obtained in step (1) in the petri dish for 20-30 min. Finally, take out the fully soaked hydrogel and place it in an oven at a constant temperature of 30-40℃ for 8-10 h to obtain a hydrogel with high weather resistance, high responsiveness and stability.

[0015] In step (1) above, the concentration of acrylamide in solution a is 0.25-0.375 g / mL and the concentration of gelatin is 0.15-0.25 g / mL; each g of gelatin requires 0.00108-0.0018 g of N,N'-methylenebisacrylamide and 0.01-0.02 g of ammonium persulfate.

[0016] Furthermore, the temperature of the crosslinking reaction in the mixed solution in step (1) above is 50-60℃, and the time is 8-10 h.

[0017] In step (2) above, the mass ratio of water to ethylene glycol and glycerol in the salt solution is 1:3:1.

[0018] The salt in the salt solution in steps (1) and (2) above is sodium gluconate (C6H4O2). 11 O7Na), sodium sulfate (Na2SO4), disodium hydrogen phosphate dodecahydrate (Na2HPO4·12H2O), disodium ethylenediaminetetraacetic acid dihydrate (C 10 H 14 The salt solution contains at least one of N2Na2O8•2H2O and sodium chloride (NaCl), and the sodium ion concentration in the salt solution is 0.2-1 mol / L.

[0019] More preferably, the salt in the salt solution in steps (1) and (2) above is disodium hydrogen phosphate dodecahydrate.

[0020] Hydrogels with high weather resistance, high responsiveness and stability were prepared using the above preparation method.

[0021] The aforementioned hydrogels, exhibiting high weather resistance, high responsiveness, and stability, are applied in temperature sensors. By selecting the AC impedance value as the temperature response signal, and applying a specific excitation signal under AC excitation, temperature changes are characterized by the sensor's AC impedance, current, voltage, and other response signals, achieving a temperature response with high weather resistance, high stability, and high sensitivity.

[0022] The beneficial effects of this invention are:

[0023] (1) The composite alcohol solution composed of "ethylene glycol + glycerol + ionic solution (salt solution)" in this invention can further improve the stability and weather resistance of hydrogels and sensors prepared therefrom during long-term use. On the one hand, glycerol has a high viscosity and a relatively low permeation rate in the hydrogel matrix, which easily leads to an uneven concentration distribution of "surface enrichment and internal depletion". Introducing ethylene glycol can effectively reduce the viscosity of the system and improve the diffusion capacity, thereby promoting a more uniform distribution of the composite alcohol solution in the thickness direction of the material, enhancing the consistency of the treatment and long-term durability; and ethylene glycol has good compatibility with water and glycerol, which can reduce the risk of local phase separation and improve the stability of the system during long-term use. On the other hand, the introduction of salt solution (ionic solution, such as NaH2PO4) into the composite alcohol solution constructs an "ion buffer", which can alleviate the loss and concentration fluctuation of ions during long-term storage or recycling, and is more conducive to maintaining the stability of electrical signals and the reliability of the recycling platform. Finally, the composite alcohol solution system of the present invention can not only maintain good antifreeze and water retention capabilities through the dilution effect of ethylene glycol and ionic solution, but also effectively suppress the response delay caused by excessive viscosity, making the temperature sensitivity curve clearer and more repeatable. It can also replace the water on the surface of the hydrogel and form a protective layer on the surface of the hydrogel, so that the hydrogel can still be tested for temperature response at high and low temperatures.

[0024] (2) In this invention, alcohol molecules can effectively replace and expel some of the water in the surface network of the hydrogel, thereby forming a dense hydrophobic protective film on its surface. This film acts as a barrier, significantly reducing the evaporation of internal water, greatly improving the weather resistance of the material, and fundamentally reducing signal distortion caused by dehydration. At the same time, during this process, alcohol molecules interact with water molecules in the hydrogel network, promoting the formation of a tighter and more stable cross-linked structure inside the hydrogel. This structure enhances the mechanical properties of the hydrogel, effectively resisting damage to its structure from external factors, reducing structural damage and performance degradation caused by external interference, maintaining its own performance stability, reducing material fatigue and damage caused by local stress concentration, improving the fatigue resistance of the hydrogel, and providing solid and reliable support for subsequent temperature response and applications.

[0025] (3) This invention uses sodium dihydrogen phosphate as the electrolyte, whose ions have good migration ability in the hydrogel system. By precisely controlling the ion concentration of sodium dihydrogen phosphate, the ion conduction environment inside the hydrogel can be changed. When the ion concentration is in a suitable range, the migration of internal ions is smoother, and the interaction between ions is more frequent, so that the motion state of ions can change more significantly when the temperature changes. This change will make the sensor more sensitive to temperature changes, thereby further enhancing the sensor's sensitivity to temperature changes, improving detection accuracy, and enabling more precise capture of subtle temperature fluctuations.

[0026] (4) This invention uses the AC impedance value of the hydrogel as the temperature response signal, which has significant advantages. The ion conduction capacity inside the ion hydrogel is extremely sensitive to temperature changes. Under AC excitation signal, the motion state of ions (such as migration rate, collision frequency, etc.) will change significantly with temperature. This change can be directly and quickly reflected in the change of AC impedance value. By applying an AC excitation signal of a specific frequency (tested at 1 kHz) and amplitude, the sensor can capture this impedance change in real time, thereby achieving a high-sensitivity response to temperature. This mechanism avoids the problems of slow response speed of thermocouples and signal lag in scenarios with frequent temperature fluctuations. It greatly improves the sensor's ability to detect subtle temperature changes (such as temperature fluctuations of 0.1℃ or even smaller), and the responsivity can reach [around 110 in the test range of -20℃ to 45℃], which is much higher than that of traditional thermocouple sensors, providing a solid foundation for high-precision temperature monitoring.

[0027] (5) The hydrogel sensor is encapsulated using a highly elastic and aging-resistant polymer film. This film forms an effective barrier, isolating the hydrogel from external humidity changes and contaminant intrusion, preventing damage to the structure and performance of the hydrogel, preventing signal drift and performance impairment, and ensuring high detection accuracy and reliable operation even during long-term use. Simultaneously, this polymer film has excellent elasticity, effectively adapting to deformations that may occur in the hydrogel under temperature changes or external forces, preventing any impact on the normal operation of the sensor. Excellent aging resistance ensures that the encapsulation structure can resist light and oxidation during long-term use, without cracking or degradation, maintaining its integrity. Through this encapsulation design, the sensor's performance remains stable over a long period, ensuring high accuracy and reliability during extended use. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 The tensile properties diagram is shown for the hydrogel prepared in Example 1 of this invention.

[0030] Figure 2 Physical images of samples prepared for different embodiments; wherein, (a) is a sample treated with glycerol alone (Comparative Example 2); (b) is a sample treated with the composite alcohol solution prepared in Example 1; and (c) is a sample not soaked in alcohol solution (Comparative Example 1).

[0031] Figure 3 The weight loss rate of the samples prepared for Example 1 and Comparative Example 2 at 60°C every half hour.

[0032] Figure 4 This is a schematic diagram of a sensor assembled from a hydrogel with high weather resistance, high responsiveness, and stability prepared according to the present invention.

[0033] Figure 5 The thermosensitive response behavior of the sensors assembled from the hydrogels prepared in Examples 1-5.

[0034] Figure 6 The temperature-sensitive response behavior of the sensor assembled from the hydrogel prepared in Example 1 after being placed for two months.

[0035] Figure 7 This is a schematic diagram illustrating the potential application of the hydrogel prepared in this invention as a patch sensor. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 are within the scope of protection of the present invention.

[0037] Example 1

[0038] The method for preparing the hydrogel with high weather resistance, high responsiveness, and stability in this embodiment includes the following steps:

[0039] (1) First, weigh 1.4326 g of disodium hydrogen phosphate dodecahydrate and add it to a beaker containing 40 g of purified water. Place the beaker on a magnetic stirrer and stir at 50°C for 20 minutes until the disodium hydrogen phosphate dodecahydrate is completely dissolved to obtain a salt solution. Then, add 12 g of acrylamide and 8 g of gelatin to the beaker and seal it with plastic wrap. Then, place the beaker in a 60°C constant temperature magnetic stirrer and stir until the acrylamide and gelatin are completely dissolved. Remove the beaker and let it cool naturally on a room temperature magnetic stirrer for 20 minutes. Then, add 1.08 g of N,N'-methylenebisacrylamide solution (1 wt%) and 1 g of ammonium persulfate solution (10 wt%) to the beaker. The mixture (wt%) was stirred at room temperature on a magnetic stirrer for 30 minutes to ensure thorough mixing of all components and obtain a homogeneous solution. Finally, the solution was slowly poured into a pre-prepared mold and placed in an oven at 55°C for 8 hours for cross-linking reaction. After the reaction was completed, the hydrogel was obtained.

[0040] (2) Weigh 3.2233 g of disodium hydrogen phosphate dodecahydrate and add it to a beaker. Then add 20 g of purified water to the beaker and place it on a magnetic stirrer and stir for 30 minutes until the disodium hydrogen phosphate dodecahydrate is completely dissolved. Then add 60 g of ethylene glycol and 20 g of glycerol to the beaker and stir for 20 minutes to obtain a uniform mixed alcohol washing solution. Then pour the alcohol washing solution into a petri dish and soak the hydrogel obtained in step (1) in the petri dish for 30 minutes. Finally, take out the fully soaked hydrogel and place it in a 30°C oven for 10 hours to obtain a hydrogel with high weather resistance, high responsiveness and stability.

[0041] Example 2

[0042] The method for preparing the hydrogel with high weather resistance, high responsiveness, and stability in this embodiment includes the following steps:

[0043] (1) First, weigh 1.6650 g of disodium ethylenediaminetetraacetate dihydrate and add it to a beaker containing 40 g of purified water. Place the beaker on a magnetic stirrer and stir at 50°C for 20 minutes until the disodium ethylenediaminetetraacetate dihydrate is completely dissolved to obtain a salt solution. Then, add 12 g of acrylamide and 8 g of gelatin to the beaker and seal it with plastic wrap. Then, place the beaker in a 60°C constant temperature magnetic stirrer and stir until the acrylamide and gelatin are completely dissolved. Remove the beaker and let it cool naturally on a room temperature magnetic stirrer for 20 minutes. Then, add 1.08 g of N,N'-methylenebisacrylamide solution (1 wt%) and 1 g of ammonium persulfate solution (10 wt%) to the beaker. The mixture (wt%) was stirred at room temperature on a magnetic stirrer for 30 minutes to ensure thorough mixing of all components and obtain a homogeneous solution. Finally, the solution was slowly poured into a pre-prepared mold and placed in an oven at 55°C for 8 hours for cross-linking reaction. After the reaction was completed, the hydrogel was obtained.

[0044] (2) Weigh 3.7462 g of disodium ethylenediaminetetraacetate dihydrate and add it to a beaker. Then add 20 g of purified water to the beaker and place it on a magnetic stirrer and stir for 30 minutes until the disodium ethylenediaminetetraacetate dihydrate is completely dissolved. Then add 60 g of ethylene glycol and 20 g of glycerol to the beaker and stir for 20 minutes to obtain a uniform mixed alcohol washing solution. Then pour the alcohol washing solution into a petri dish and soak the hydrogel obtained in step (1) in the petri dish for 30 minutes. Finally, take out the fully soaked hydrogel and place it in a 30°C oven for 10 hours to obtain a hydrogel with high weather resistance, high responsiveness and stability.

[0045] Example 3

[0046] The method for preparing the hydrogel with high weather resistance, high responsiveness, and stability in this embodiment includes the following steps:

[0047] (1) First, weigh 1.7451 g of sodium gluconate and add it to a beaker containing 40 g of purified water. Place the beaker on a magnetic stirrer and stir at 50°C for 20 minutes until the sodium gluconate is completely dissolved to obtain a salt solution. Then, add 12 g of acrylamide and 8 g of gelatin to the beaker and seal it with plastic wrap. Then, place the beaker in a 60°C constant temperature magnetic stirrer and stir until the acrylamide and gelatin are completely dissolved. Remove the beaker and place it on a room temperature magnetic stirrer to cool naturally for 20 minutes. Then, add 1.08 g of N,N'-methylenebisacrylamide solution (1 wt%) and 1 g of ammonium persulfate solution (10 wt%) to the beaker and stir at room temperature for 30 minutes to ensure that the components are fully mixed to obtain a homogeneous solution. Finally, slowly pour the solution into a pre-prepared mold and place the mold in a 55°C oven for crosslinking reaction for 8 hours. After the reaction is complete, the hydrogel can be obtained.

[0048] (2) Weigh 3.9265 g of sodium gluconate and add it to a beaker. Then add 20 g of purified water to the beaker and place it on a magnetic stirrer and stir for 30 minutes until the sodium gluconate is completely dissolved. Then add 60 g of ethylene glycol and 20 g of glycerol to the beaker and stir for 20 minutes to obtain a uniform mixed alcohol washing solution. Then pour the alcohol washing solution into a petri dish and soak the hydrogel obtained in step (1) in the petri dish for 30 minutes. Finally, take out the fully soaked hydrogel and place it in a 30°C oven for 10 hours to obtain a hydrogel with high weather resistance, high responsiveness and stability.

[0049] Example 4

[0050] The method for preparing the hydrogel with high weather resistance, high responsiveness, and stability in this embodiment includes the following steps:

[0051] (1) First, weigh 0.4675 g of sodium chloride and add it to a beaker containing 40 g of purified water. Place the beaker on a magnetic stirrer and stir at 50°C for 20 minutes until the sodium chloride is completely dissolved to obtain a salt solution. Then, add 12 g of acrylamide and 8 g of gelatin to the beaker and seal it with plastic wrap. Then, place the beaker in a 60°C constant temperature magnetic stirrer and stir until the acrylamide and gelatin are completely dissolved. Remove the beaker and place it on a room temperature magnetic stirrer to cool naturally for 20 minutes. Then, add 1.08 g of N,N'-methylenebisacrylamide solution (1 wt%) and 1 g of ammonium persulfate solution (10 wt%) to the beaker and stir at room temperature on a magnetic stirrer for 30 minutes to ensure that the components are fully mixed to obtain a homogeneous solution. Finally, slowly pour the solution into a pre-prepared mold and place the mold in a 55°C oven for crosslinking reaction for 8 hours. After the reaction is complete, remove the mold to obtain a hydrogel.

[0052] (2) Weigh 1.0519 g of sodium chloride and add it to a beaker. Then add 20 g of purified water to the beaker and place it on a magnetic stirrer and stir for 30 minutes until the sodium chloride is completely dissolved. Then add 60 g of ethylene glycol and 20 g of glycerol to the beaker and stir for 20 minutes to obtain a uniform mixed alcohol washing solution. Then pour the alcohol washing solution into a petri dish and soak the hydrogel obtained in step (1) in the petri dish for 30 minutes. Finally, take out the fully soaked hydrogel and place it in a 30°C oven for 10 hours to obtain a hydrogel with high weather resistance, high responsiveness and stability.

[0053] Example 5

[0054] The method for preparing the hydrogel with high weather resistance, high responsiveness, and stability in this embodiment includes the following steps:

[0055] (1) First, weigh 0.5688 g of sodium sulfate and add it to a beaker containing 40 g of purified water. Place the beaker on a magnetic stirrer and stir at 50°C for 20 minutes until the sodium sulfate is completely dissolved to obtain a salt solution. Then, add 12 g of acrylamide and 8 g of gelatin to the beaker and seal it with plastic wrap. Then, place the beaker in a 60°C constant temperature magnetic stirrer and stir until the acrylamide and gelatin are completely dissolved. Remove the beaker and place it on a room temperature magnetic stirrer to cool naturally for 20 minutes. Then, add 1.08 g of N,N'-methylenebisacrylamide solution (1 wt%) and 1 g of ammonium persulfate solution (10 wt%) to the beaker and stir at room temperature on a magnetic stirrer for 30 minutes to ensure that the components are fully mixed to obtain a homogeneous solution. Finally, slowly pour the solution into a pre-prepared mold and place the mold in a 55°C oven for crosslinking reaction for 8 hours. After the reaction is complete, remove the mold to obtain a hydrogel.

[0056] (2) Weigh 1.2794 g of sodium sulfate and add it to a beaker. Then add 20 g of purified water to the beaker and place it on a magnetic stirrer and stir for 30 minutes until the sodium sulfate is completely dissolved. Then add 60 g of ethylene glycol and 20 g of glycerol to the beaker and stir for 20 minutes to obtain a uniform mixed alcohol washing solution. Then pour the alcohol washing solution into a petri dish and soak the hydrogel obtained in step (1) in the petri dish for 30 minutes. Finally, take out the fully soaked hydrogel and place it in a 30°C oven for 10 hours to obtain a hydrogel with high weather resistance, high responsiveness and stability.

[0057] Example 6

[0058] The method for preparing the hydrogel with high weather resistance, high responsiveness, and stability in this embodiment includes the following steps:

[0059] (1) First, weigh 0.5688 g of sodium sulfate and add it to a beaker containing 40 g of purified water. Place the beaker on a magnetic stirrer and stir at 50°C for 20 minutes until the sodium sulfate is completely dissolved to obtain a salt solution. Then, add 15 g of acrylamide and 6 g of gelatin to the beaker and seal it with plastic wrap. Then, place the beaker in a 60°C constant temperature magnetic stirrer and stir until the acrylamide and gelatin are completely dissolved. Remove the beaker and place it on a room temperature magnetic stirrer to cool naturally for 20 minutes. Then, add 1.08 g of N,N'-methylenebisacrylamide solution (1 wt%) and 1 g of ammonium persulfate solution (10 wt%) to the beaker and stir at room temperature on a magnetic stirrer for 30 minutes to fully mix the components and obtain a homogeneous solution. Finally, slowly pour the solution into a pre-prepared mold and place the mold in a 50°C oven for a crosslinking reaction for 10 hours. After the reaction is complete, remove the mold to obtain a hydrogel.

[0060] (2) Weigh 1.2794 g of sodium sulfate and add it to a beaker. Then add 20 g of purified water to the beaker and place it on a magnetic stirrer and stir for 30 minutes until the sodium sulfate is completely dissolved. Then add 60 g of ethylene glycol and 20 g of glycerol to the beaker and stir for 20 minutes to obtain a uniform mixed alcohol washing solution. Then pour the alcohol washing solution into a petri dish and soak the hydrogel obtained in step (1) in the petri dish for 25 minutes. Finally, take out the fully soaked hydrogel and place it in a 35°C oven for 9 hours to obtain a hydrogel with high weather resistance, high responsiveness and stability.

[0061] Example 7

[0062] The method for preparing the hydrogel with high weather resistance, high responsiveness, and stability in this embodiment includes the following steps:

[0063] (1) First, weigh 0.5688 g of sodium sulfate and add it to a beaker containing 40 g of purified water. Place the beaker on a magnetic stirrer and stir at 50°C for 20 minutes until the sodium sulfate is completely dissolved to obtain a salt solution. Then, add 10 g of acrylamide and 10 g of gelatin to the beaker and seal it with plastic wrap. Then, place the beaker in a 60°C constant temperature magnetic stirrer and stir until the acrylamide and gelatin are completely dissolved. Remove the beaker and place it on a room temperature magnetic stirrer to cool naturally for 20 minutes. Then, add 1.08 g of N,N'-methylenebisacrylamide solution (1 wt%) and 1 g of ammonium persulfate solution (10 wt%) to the beaker and stir at room temperature on a magnetic stirrer for 30 minutes to fully mix the components and obtain a homogeneous solution. Finally, slowly pour the solution into a pre-prepared mold and place the mold in a 60°C oven for crosslinking reaction for 9 hours. After the reaction is complete, remove the mold to obtain a hydrogel.

[0064] (2) Weigh 1.2794 g of sodium sulfate and add it to a beaker. Then add 20 g of purified water to the beaker and place it on a magnetic stirrer and stir for 30 minutes until the sodium sulfate is completely dissolved. Then add 60 g of ethylene glycol and 20 g of glycerol to the beaker and stir for 20 minutes to obtain a uniform mixed alcohol washing solution. Then pour the alcohol washing solution into a petri dish and soak the hydrogel obtained in step (1) in the petri dish for 20 minutes. Finally, take out the fully soaked hydrogel and place it in a 40°C oven for 8 hours to obtain a hydrogel with high weather resistance, high responsiveness and stability.

[0065] Comparative Example 1

[0066] The preparation method of the hydrogel in this comparative example differs from that in Example 1 in that step (2) was not performed. The steps are as follows:

[0067] First, weigh 1.4326 g of disodium hydrogen phosphate dodecahydrate and add it to a beaker containing 40 g of purified water. Place the beaker on a magnetic stirrer and stir at 50°C for 20 minutes until the disodium hydrogen phosphate dodecahydrate is completely dissolved, obtaining a salt solution. Then, add 12 g of acrylamide and 8 g of gelatin to the beaker and seal it with plastic wrap. Next, place the beaker in a 60°C constant-temperature magnetic stirrer and stir until the acrylamide and gelatin are completely dissolved. Remove the beaker and allow it to cool naturally on a room-temperature magnetic stirrer for 20 minutes. Then, add 1.08 g of... The N,N'-methylenebisacrylamide solution (1 wt%) and 1 g ammonium persulfate solution (10 wt%) were stirred at room temperature on a magnetic stirrer for 30 minutes to ensure thorough mixing of the components and obtain a homogeneous solution. Finally, the solution was slowly poured into a pre-prepared mold and placed in an oven at 55°C for a crosslinking reaction for 8 hours. After the reaction was completed, the hydrogel was obtained.

[0068] Comparative Example 2

[0069] The preparation method of the hydrogel in this comparative example differs from that in Example 1 in that only glycerol is used in step (2), and the steps are as follows:

[0070] (1) First, weigh 1.4326 g of disodium hydrogen phosphate dodecahydrate and add it to a beaker containing 40 g of purified water. Place the beaker on a magnetic stirrer and stir at 50°C for 20 minutes until the disodium hydrogen phosphate dodecahydrate is completely dissolved to obtain a salt solution. Then, add 12 g of acrylamide and 8 g of gelatin to the beaker and seal it with plastic wrap. Then, place the beaker in a 60°C constant temperature magnetic stirrer and stir until the acrylamide and gelatin are completely dissolved. Remove the beaker and let it cool naturally on a room temperature magnetic stirrer for 20 minutes. Then, add 1.08 g of N,N'-methylenebisacrylamide solution (1 wt%) and 1 g of ammonium persulfate solution (10 wt%) to the beaker. The mixture was stirred at room temperature for 30 minutes on a magnetic stirrer to ensure thorough mixing of all components and obtain a homogeneous solution. Finally, the solution was slowly poured into a pre-prepared mold and placed in an oven at 55°C for 8 hours for cross-linking reaction. After the reaction was completed, the mixture was removed to obtain a hydrogel.

[0071] (2) Weigh 3.2233 g of disodium hydrogen phosphate dodecahydrate and add it to a beaker. Then add 20 g of purified water to the beaker and place it on a magnetic stirrer and stir for 30 minutes until the disodium hydrogen phosphate dodecahydrate is completely dissolved. Then add 80 g of glycerol to the beaker and stir for 20 minutes to obtain a uniform mixed alcohol washing solution. Then pour the alcohol washing solution into a petri dish and soak the hydrogel obtained in step (1) in the petri dish for 30 minutes. Finally, take out the fully soaked hydrogel and place it in a 30°C oven for 10 hours to obtain the hydrogel.

[0072] The composite alcohol system retains the antifreeze and water-retention properties of glycerol while reducing response delay through the low viscosity of ethylene glycol. Alcohol molecules can form a dense and flexible hydrophobic protective film on the hydrogel surface, not only densifying the internal cross-linked structure but also fixing the alcohol molecules within the gel network to prevent alcohol volatilization at high temperatures. Simultaneously, sodium ions in the ionic solution can bind with the alcohol molecules, increasing the cross-linking density of the hydrogel and achieving enhanced water retention, structural stability, sensitivity, and mechanical properties. This effectively solves the core problems of poor weather resistance, low reactivity, and poor stability in existing hydrogel temperature sensors, achieving a synergistic improvement in weather resistance, reactivity, and operational stability, making it more suitable for practical applications such as flexible wearables and medical monitoring.

[0073] Implementation Results Example

[0074] Figure 1 The load-displacement curves of disodium hydrogen phosphate dodecahydrate hydrogel obtained in tensile fracture tests are shown respectively. Figure 1 a) Stress-strain curve ( Figure 1 b) and cyclic tensile performance curves ( Figure 1 c). The treated hydrogel sample exhibited a high elongation at break of 890% and a tensile strength of 1.1 MPa. After 180 cycles of tensile testing (each time stretched to 150% of the initial length and then unloaded), the hydrogel showed a stress retention rate and strain recovery rate exceeding 90%, demonstrating excellent mechanical stability and fatigue resistance, effectively overcoming the limitations of traditional hydrogels that are prone to mechanical damage and rapid performance degradation. These results indicate that the material can withstand repeated mechanical loading without significant performance degradation, making it suitable for practical applications in sensors (such as bonding to human skin or the surface of flexible electronic devices). Figure 7 It is of great significance for the long-term reliable use of ).

[0075] Figure 2 Images of disodium hydrogen phosphate dodecahydrate hydrogels are shown, both before and after immersion in different solutions and subsequent weathering treatments. The images reveal the differences in performance between the samples treated with glycerol alone (…). Figure 2The hardening and yellowing of sample a) was significantly greater than that of the sample treated with the compound alcohol solution. Figure 2 b), and the former's water retention effect was significantly lower than the latter's, while the sample that was not soaked in alcohol solution ( Figure 2 c) It is clearly milky white and feels very hard and brittle to the touch, indicating that it is completely dehydrated.

[0076] Figure 3 The weight loss rate of disodium hydrogen phosphate dodecahydrate hydrogel samples was measured every half hour at 60°C after immersion in a composite alcohol solution and a single glycerol solution. The figure shows that the weight loss rate of the sample treated with the composite alcohol solution was significantly lower than that of the sample treated with the glycerol solution.

[0077] Figure 4 The overall structure of the hydrogel sensor is presented. The sensor comprises three main parts: a flexible encapsulation layer, a hydrogel response medium (hydrogel), and a silver nanoparticle microsensor. The flexible encapsulation layer, located on the outer layer, provides protection, effectively blocking moisture and dust, and possesses both wear resistance and flexibility. The hydrogel response medium, as the temperature-sensing core, exhibits a three-dimensional network structure that reversibly swells or contracts with temperature changes, thereby altering electrical parameters. The silver nanoparticle microsensor is responsible for detecting these parameter changes in real time and converting them into electrical signals, thus achieving high-precision temperature monitoring. Through optimized overall structural design and tight integration of all components, the sensor's performance stability and detection sensitivity are ensured.

[0078] according to Figure 4 The sensor was assembled using the structure shown. The specific assembly and testing steps are as follows: First, a glass slide was used as the base layer. Then, a circular piece of hydrogel, the same size as the nano-silver microsensor, was cut and placed in close contact with the electrode side of the nano-silver microsensor. Finally, adhesive tape was used as an encapsulation layer to seal the sensor and provide some isolation from the external environment. Thermosensitive response performance was then tested, and the results are as follows: Figure 5 As shown. Figure 5 Figures a and e respectively illustrate the response behavior of hydrogel temperature-sensitive elements prepared using disodium hydrogen phosphate dodecahydrate (Example 1), disodium ethylenediaminetetraacetate dihydrate (Example 2), sodium gluconate (Example 3), sodium chloride (Example 4), and sodium sulfate (Example 3) as salt ions within a temperature range of -20°C to 45°C. The figures show the sensitivity change trend of the temperature-sensitive element during cyclic temperature increases and decreases. When the salt ion of the hydrogel is disodium hydrogen phosphate dodecahydrate, its response performance value exceeds 110 (…). Figure 5 a) This fully demonstrates the material's advantages in temperature sensitivity, providing reliable data support for the sensor to achieve accurate temperature measurement over a wide temperature range, and further verifying the effectiveness and superiority of the technical solution adopted in this invention.

[0079] Figure 6 The response behavior of a hydrogel temperature-sensitive element prepared using disodium hydrogen phosphate dodecahydrate (Example 1) as the salt ion is presented in the temperature range of -20°C to 45°C after two months of storage. The figure shows that although the hydrogel temperature-sensitive element has been stored for two months, its response performance value still reaches 100 with cyclical temperature increases and decreases during subsequent testing, and is comparable to its initial value (before storage). Figure 5 The response values ​​of a) are not significantly different, which fully demonstrates the stability and weather resistance of the sensor.

[0080] The hydrogel temperature sensor prepared in this invention can be integrated into flexible wearable devices to achieve real-time, high-precision monitoring of human skin surface temperature. For example, in the field of sports and health, the sensor can continuously track athletes' body temperature changes during training. When abnormal increases or decreases in body temperature are observed, it can promptly issue warnings to users via connected smart terminals, helping them to scientifically adjust exercise intensity and pace and prevent sports injuries. In medical diagnosis, it can be applied to specific lesion sites on patients, such as the joints of arthritis patients, to monitor temperature changes in the lesion area over a long period, providing doctors with accurate temperature data to assess disease progression and develop personalized treatment plans. Furthermore, this sensor can also be applied to the field of intelligent robotics, acting as the robot's "skin" to sense ambient temperature. This allows the robot to make more precise adjustments to its movements based on temperature information when interacting with humans or performing specific tasks, improving the robot's intelligence and safety.

[0081] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a hydrogel with high weather resistance, high responsiveness, and stability, characterized in that, The steps are as follows: (1) Add acrylamide and gelatin to the salt solution and wait for them to dissolve to obtain solution a; then add N,N'-methylenebisacrylamide solution and ammonium persulfate solution to solution a to obtain a mixed solution, and obtain hydrogel through cross-linking reaction; (2) Add ethylene glycol and glycerol to the salt solution to obtain a mixed alcohol washing solution; (3) Immerse the hydrogel obtained in step (1) in a mixed alcohol washing solution, take it out and treat it at 30-40℃ for 8-10 h to obtain the hydrogel.

2. The method for preparing a hydrogel with high weather resistance, high responsiveness, and stability according to claim 1, characterized in that, In step (1), the concentration of acrylamide in solution a is 0.25-0.375 g / mL and the concentration of gelatin is 0.15-0.25 g / mL.

3. The method for preparing a hydrogel with high weather resistance, high responsiveness, and stability according to claim 2, characterized in that, In the mixed solution of step (1), each g of gelatin requires 0.00108-0.0018 g of N,N'-methylenebisacrylamide and 0.01-0.02 g of ammonium persulfate.

4. The method for preparing a hydrogel with high weather resistance, high responsiveness, and stability according to claim 3, characterized in that, The temperature of the crosslinking reaction in the mixed solution in step (1) is 50-60℃ and the time is 8-10 h.

5. The method for preparing a hydrogel with high weather resistance, high responsiveness, and stability according to claim 1, characterized in that, In step (2), the mass ratio of water to ethylene glycol and glycerol in the salt solution is 1:3:

1.

6. The method for preparing a hydrogel with high weather resistance, high responsiveness, and stability according to claim 5, characterized in that, The salt in the salt solution in steps (1) and (2) is at least one of sodium gluconate, sodium sulfate, disodium hydrogen phosphate dodecahydrate, disodium ethylenediaminetetraacetate dihydrate, and sodium chloride.

7. The method for preparing a hydrogel with high weather resistance, high responsiveness, and stability according to claim 6, characterized in that, In steps (1) and (2), the sodium ion concentration in the salt solution is 0.2-1 mol / L.

8. The method for preparing a hydrogel with high weather resistance, high responsiveness, and stability according to claim 7, characterized in that, The soaking time in step (3) is 20-30 min.

9. A hydrogel with high weather resistance, high responsiveness and stability prepared by the preparation method according to any one of claims 1-8.

10. The application of the hydrogel with high weather resistance, high responsiveness and stability as described in claim 9 in sensors.

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