Flexible self-driven hydrogel humidity sensor and preparation method thereof

Abstract

The invention discloses a flexible self-driven hydrogel humidity sensor and a preparation method thereof. The flexible self-driven hydrogel humidity sensor comprises a carbon nanotube fabric electrode, a functional layer and a metal electrode which are stacked, the functional layer comprises gelatin and kappa-carrageenan. The flexible self-driven hydrogel humidity sensor provided by the invention adopts a self-adhesion connection mode, and is directly connected with the electrode and the skin by utilizing the high adhesion of the functional layer without an additional adhesive. Moreover, the moisture power generation technology is adopted to provide power support for equipment, and the principle of converting moisture into electric energy is utilized, so that the self-power-supply function is realized. The technology reduces the dependence on an external power supply, improves the use convenience of equipment, ensures that the sensor can operate for a long time under the condition of no external power supply, and provides continuous energy support for humidity monitoring.

Description

Technical Field

[0001] The invention relates to the technical field of humidity sensors, and in particular to a flexible self-driven hydrogel humidity sensor and a preparation method thereof. Background Art

[0002] With the rapid development of global science and technology, humidity sensors are increasingly used in many fields, especially in environmental monitoring, industrial production, agricultural irrigation, smart devices and health monitoring. Especially in the fields of health monitoring and smart devices, humidity sensing technology plays a vital role. The change of human skin humidity is closely related to a variety of physiological indicators, such as skin moisture content, sweat secretion and humidity of the local environment, which can be used as important indicators to reflect human health.

[0003] However, most of the existing humidity sensors currently use capacitive or resistive hard materials, and are mainly used for environmental humidity monitoring or industrial applications. These sensors reflect changes in humidity by detecting changes in capacitance or resistance values. Although they have certain accuracy and response speed, they have obvious defects when in contact with human skin. Due to the use of rigid materials, these sensors are difficult to adapt to the softness and dynamic characteristics of the skin, and long-term wearing will result in poor comfort. In addition, traditional humidity sensors have limited sensitivity in low humidity environments and it is difficult to accurately capture subtle humidity changes on the skin surface. Over time, changes in ambient temperature or physical damage may also affect sensing performance, resulting in a decrease in the accuracy of humidity data.

[0004] In addition, the existing technology also has significant deficiencies in flexibility and fit. Rigid material sensors cannot fit tightly to the skin surface, which not only affects the comfort of wearing, but also reduces the accuracy of the data. At the same time, the lack of sensitivity and stability makes it difficult for the sensor to accurately capture subtle humidity changes on the skin surface. In addition, energy consumption is also an important factor restricting long-term monitoring. Many sensors rely on external power supplies, which limits their application in wearable devices. Summary of the invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a flexible self-driven hydrogel humidity sensor and a preparation method thereof. The humidity sensor is self-powered by moisture power generation, has good skin fit and high sensitivity, can be worn comfortably for a long time, and can accurately detect humidity, and has broad application prospects.

[0006] The present invention is achieved through the following technical solutions:

[0007] A first aspect of the present invention provides a flexible self-driven hydrogel humidity sensor, which comprises a stacked carbon nanotube fabric electrode, a functional layer and a metal electrode; the functional layer comprises gelatin and κ-carrageenan.

[0008] In the flexible self-driven hydrogel humidity sensor provided by the present invention, the carbon nanotube (CNT) fabric electrode and the metal electrode constitute an asymmetric electrode pair. Compared with the traditional carbon black electrode, the carbon nanotube fabric electrode has excellent hydrophilicity, high specific surface area and conductivity, thereby being able to generate an electrical signal with a higher response rate and a higher signal-to-noise ratio, significantly improving the signal quality and signal-to-noise ratio of the sensor.

[0009] In the flexible self-driven hydrogel humidity sensor provided by the present invention, the materials of the functional layer are all easily accessible natural organic materials, with good biocompatibility and biodegradability, and the molecular chains of gelatin and κ-carrageenan are in a helical structure, which provides a good energy dissipation mechanism and enhances the stretchability of the material. The material of the functional layer itself has good adhesion properties. Gelatin and κ-carrageenan are rich in hydrophilic groups such as hydroxyl, amino and carboxyl groups. These groups can be closely attached to organic fabrics, metal materials and human epidermis through hydrogen bonds and electrostatic effects, ensuring that the sensor is effectively adhered to the skin and can maintain a comfortable fit, so that the sensor can sensitively detect changes in skin humidity.

[0010] In addition, the porous network structure formed by the combination of gelatin and κ-carrageenan in the functional layer can promote the conduction and adsorption of moisture, thereby generating electrical signals. The specific principle is that the sulfate group of the negatively charged group of κ-carrageenan in the functional layer and the COO - and NH 3 + The groups together construct an efficient dual ion migration channel, which can effectively improve the separation and migration rate of ions, thereby generating high-quality electrical signals and ensuring that the sensor has a high signal-to-noise ratio when responding to changes in skin humidity.

[0011] The present invention uses gelatin and kappa-carrageenan to construct a double network hydrogel, which has high hygroscopicity and good flexibility. In the sensor design, the combination of carbon nanotube fabric electrodes and metal electrodes realizes efficient moisture power generation and sensing functions. The core principle of moisture power generation is based on the construction of an efficient dual ion transmission channel, which uses asymmetric moisture distribution to induce charge separation. When the hydrogel absorbs moisture on the skin surface, water molecules form a gradient inside the hydrogel, thereby inducing an asymmetric ion distribution. In this process, the dual ion transmission channel can promote the rapid migration of ions, so that the charge is separated between the metal electrode and the carbon nanotube fabric electrode, generating an electrical signal. This dual ion transmission channel design greatly improves the efficiency of moisture power generation, and the flexibility of the hydrogel material ensures that the sensor can fit closely to the skin surface for a long time, which not only ensures the effectiveness of moisture adsorption, but also improves the stable output of electrical signals.

[0012] Furthermore, the mass ratio of gelatin to κ-carrageenan is (3-5):(0.05-0.1).

[0013] Furthermore, the metal electrode is a metal aluminum electrode.

[0014] The second aspect of the present invention provides a method for preparing the flexible self-driven hydrogel humidity sensor according to the first aspect, comprising the following steps:

[0015] S1. Immersing the fabric in a carbon nanotube dispersion, taking out the impregnated fabric and drying it to obtain a carbon nanotube fabric electrode;

[0016] S2. mixing water, a humectant, a pH regulator, an ion enhancer and κ-carrageenan until the solution is transparent, adding gelatin, and obtaining a hydrogel solution after the gelatin is completely dissolved, and preparing the hydrogel solution into a hydrogel;

[0017] S3. The carbon nanotube fabric electrode described in S1, the hydrogel described in S2, and the metal electrode are stacked in order to form a sandwich structure to construct the flexible self-driven hydrogel humidity sensor.

[0018] Furthermore, in S1, before the impregnation, the step of plasma treating the fabric is also included to enhance the hydrophilicity of the fabric.

[0019] Furthermore, the plasma treatment time is 6-10 minutes.

[0020] Furthermore, in S1, a fabric made of plant cellulose is selected.

[0021] Furthermore, in S1, the concentration of carbon nanotubes in the carbon nanotube dispersion is 0.15-0.3 wt %.

[0022] Furthermore, in S1, the immersion time is 10-20 minutes, and after ensuring that the fabric completely absorbs the carbon nanotubes, the excess carbon nanotube dispersion is scraped off.

[0023] Furthermore, in S1, the drying method is: drying the impregnated fabric at 70-80°C.

[0024] Furthermore, in S1, after the drying treatment, the step of plasma treating the fabric is also included.

[0025] Furthermore, the plasma treatment time is 6-10 minutes.

[0026] Furthermore, S1 also includes a step of patterning the obtained carbon nanotube fabric electrode to ensure that the functional layer can directly adhere to the skin.

[0027] Furthermore, in S2, the humectant is selected from one or more of glycerol, ethylene glycol and propylene glycol.

[0028] Furthermore, in S2, the pH adjuster is selected from one or more of sodium citrate, citric acid, sodium malate and sodium lactate, preferably sodium citrate and citric acid.

[0029] Furthermore, in S2, the ion enhancer is selected from one or more of sodium chloride, potassium chloride and magnesium chloride.

[0030] Furthermore, in S2, the mass ratio of the water, moisturizing agent, pH regulator, ion enhancer and κ-carrageenan is (7.8-8.2):(5.8-6.2):(1-1.5):(0.88-0.96):(0.05-0.1).

[0031] Furthermore, in S2, the concentration of κ-carrageenan in the hydrogel is 0.1-0.5 wt %.

[0032] Further, in S2, water, glycerol, sodium citrate, sodium chloride, citric acid and κ-carrageenan are mixed at 85-95° C. until the solution is transparent.

[0033] Furthermore, in S2, the mass ratio of gelatin to κ-carrageenan is (3-5):(0.05-0.1).

[0034] Further, in S2, after gelatin is added, it is heated at 70-80°C for 3-4h to ensure that the gelatin is completely dissolved.

[0035] Further, in S2, the hydrogel solution is poured into a mold and cooled to form a hydrogel.

[0036] Furthermore, in S3, the metal electrode is a metal aluminum electrode.

[0037] Furthermore, in S3, the double-sided conductive aluminum tape is made into a metal electrode.

[0038] Beneficial effects of the present invention:

[0039] 1. The flexible self-driven hydrogel humidity sensor provided by the present invention adopts a self-adhesive connection method, and directly connects to the electrode and the skin by utilizing the high adhesion of the functional layer, without the need for additional adhesive. In addition, the present invention adopts a flexible hydrogel material, which has good flexibility and comfort, and can ensure that the sensor adapts to the dynamic changes of the skin, achieving a comfortable and tight fit for a long time, thereby improving the accuracy of humidity monitoring and the comfort of users wearing it, and is particularly suitable for long-term continuous skin humidity monitoring of wearable devices. The present invention adopts a highly sensitive hydrogel humidity sensing mechanism, which can effectively monitor tiny humidity fluctuations on the skin surface, ensure accurate perception within various humidity ranges, and improve data stability.

[0040] 2. The present invention adopts wet gas power generation technology to provide power support for the equipment, and uses the principle of converting moisture into electrical energy to achieve self-powered function. This technology reduces the dependence on external power supply, improves the convenience of equipment use, ensures that the sensor can operate for a long time without external power supply, and provides continuous energy support for humidity monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a schematic diagram of the structure of the flexible self-driven hydrogel humidity sensor prepared in Example 1.

[0042] Figure 2 This is a schematic diagram of the structure of the flexible self-driven hydrogel humidity sensor prepared in Example 1 and a schematic diagram of its electrical performance working principle.

[0043] Figure 3 Schematic diagram of the preparation process of gelatin / κ-carrageenan hydrogel in Example 1.

[0044] Figure 4 Schematic diagram of the two-dimensional cross-linked network during the synthesis of gelatin / κ-carrageenan hydrogel in Example 1.

[0045] Figure 5 Schematic diagram of the surface stretching of gelatin / κ-carrageenan hydrogel in Example 1.

[0046] Figure 6Scanning electron microscope images of the cross-sections of gelatin / κ-carrageenan hydrogels with different κ-carrageenan concentrations; wherein, a is a gelatin / κ-carrageenan hydrogel with a κ-carrageenan concentration of 0 wt%, b is a gelatin / κ-carrageenan hydrogel with a κ-carrageenan concentration of 0.2 wt% in Example 3, and c is a gelatin / κ-carrageenan hydrogel with a κ-carrageenan concentration of 0.4 wt% in Example 1.

[0047] Figure 7 Graph showing the transparency test results of the gelatin / κ-carrageenan hydrogels in Examples 1-5.

[0048] Figure 8 This is a graph showing the long-term electrical performance test results of the flexible self-driven hydrogel humidity sensor prepared in Example 1.

[0049] Fig. 9 Graph showing the electrical performance and output power test results of the flexible self-driven hydrogel humidity sensor prepared in Example 1 under different load resistances.

[0050] Fig.10 This is a graph showing the electrical performance response signals of the flexible self-driven hydrogel humidity sensor prepared in Example 1 for testing the humidity of the palm and forehead skin; wherein a is the test result graph of the palm, and b is the test result graph of the forehead.

[0051] Fig.11 The electrical performance response signal diagram of the flexible self-driving hydrogel humidity sensor prepared in Example 1 under different skin humidity conditions; wherein, a is the electrical response signal diagram of the flexible self-driving hydrogel humidity sensor when the skin humidity on the inside of the wrist is in the range of 20%-70%, and b is the response time and recovery time data diagram of the flexible self-driving hydrogel humidity sensor. DETAILED DESCRIPTION

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0053] The present invention provides a flexible self-driven hydrogel humidity sensor, which comprises a stacked carbon nanotube fabric electrode, a functional layer and a metal electrode; the functional layer contains gelatin and kappa-carrageenan.

[0054] In a specific embodiment, the functional layer is a hydrogel made of gelatin and κ-carrageenan (gelatin / κ-carrageenan hydrogel), which has excellent biocompatibility and moisture adsorption capacity.

[0055] In a specific embodiment, the concentration of κ-carrageenan in the gelatin / κ-carrageenan hydrogel is 0.1-0.5 wt %.

[0056] In a specific embodiment, the flexible self-driven hydrogel humidity sensor comprises an asymmetric electrode combination of a carbon nanotube fabric electrode and a metal electrode, and leads are led out through a conductive silver paste to collect skin humidity sensing signals.

[0057] The flexible self-driven hydrogel humidity sensor provided by the present invention adopts a self-adhesive connection method. The functional layer material has good self-adhesiveness. By patterning the carbon nanotube fabric electrode, the sensor can be tightly combined with the skin, avoiding the use of additional adhesives, thereby improving the wearing comfort and stability.

[0058] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0059] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods, and the materials, reagents, etc. used are all available from commercial sources unless otherwise specified.

[0060] Example 1

[0061] A method for preparing a flexible self-driven hydrogel humidity sensor comprises the following steps:

[0062] S1. Select a fabric made of plant cellulose with a size of 9 cm × 9 cm, and subject the fabric to oxygen plasma vacuum treatment for 6 minutes to remove surface impurities and enhance its hydrophilicity; 2 O, the concentration of carbon nanotubes is 0.4wt%) and deionized water in a volume ratio of 1:1 are placed in a 50mL centrifuge tube, and ultrasonic treatment is performed using an ultrasonic cleaner for 30 minutes to evenly disperse the carbon nanotubes to obtain a carbon nanotube dispersion; the fabric after oxygen plasma vacuum treatment is immersed in the carbon nanotube dispersion for 10 minutes to ensure that the fabric completely absorbs the carbon nanotubes, and then the excess carbon nanotube dispersion is scraped off; the impregnated fabric is taken out and placed on a heating table at 80°C for drying until it is completely dry, and then oxygen plasma vacuum treatment is performed for 6 minutes to further enhance its performance to obtain a carbon nanotube fabric electrode; the carbon nanotube fabric electrode is cut into a circle with a diameter of 1 cm using a laser marking machine, and pattern design is performed, such as Figure 1 as shown to ensure that the functional layer material can directly adhere to the skin.

[0063] S2. 8 mL of water, 6 g of glycerol, 1.14 g of sodium citrate, 0.92 g of sodium chloride, 0.2 g of citric acid and 0.08 g of κ-carrageenan were mixed, and the κ-carrageenan was thoroughly dissolved on a heating table at 90°C until the solution was transparent. Then 4 g of gelatin was added and heated at 70°C for 4 hours to ensure that the gelatin was completely dissolved to obtain a hydrogel solution. The hydrogel solution was poured into a circular silicone mold with a diameter of 1 cm and a depth of 2 mm, and cooled at room temperature for 30 minutes to form a gelatin / κ-carrageenan hydrogel (the concentration of κ-carrageenan in the gelatin / κ-carrageenan hydrogel was 0.4 wt%).

[0064] S3. Use double-sided conductive aluminum tape and cut it into circular electrodes with a diameter of 1 cm by a laser marking machine to obtain a metal aluminum electrode; stack the carbon nanotube fabric electrode described in S1, the gelatin / κ-carrageenan hydrogel described in S2 (use a silicone film encapsulation layer to encapsulate the surrounding area to prevent external moisture interference), and the metal aluminum electrode in this order to form a sandwich structure to construct the flexible self-driven hydrogel humidity sensor.

[0065] Example 2

[0066] A method for preparing a flexible self-driven hydrogel humidity sensor is basically the same as that of Example 1, except that in S2, the concentration of κ-carrageenan in the gelatin / κ-carrageenan hydrogel is 0.1 wt %.

[0067] Example 3

[0068] A method for preparing a flexible self-driven hydrogel humidity sensor is basically the same as that of Example 1, except that in S2, the concentration of κ-carrageenan in the gelatin / κ-carrageenan hydrogel is 0.2 wt %.

[0069] Example 4

[0070] A method for preparing a flexible self-driven hydrogel humidity sensor is basically the same as that of Example 1, except that in S2, the concentration of κ-carrageenan in the gelatin / κ-carrageenan hydrogel is 0.3 wt %.

[0071] Example 5

[0072] A method for preparing a flexible self-driven hydrogel humidity sensor is basically the same as that of Example 1, except that in S2, the concentration of κ-carrageenan in the gelatin / κ-carrageenan hydrogel is 0.5 wt %.

[0073] Figure 1The schematic diagram of the structure of the flexible self-driven hydrogel humidity sensor prepared in Example 1 is shown, including a schematic diagram of the patterned design of the carbon nanotube fabric electrode, which is precisely patterned and printed by laser direct writing technology. This design ensures that the functional layer material (gelatin / k-carrageenan hydrogel) can directly contact the skin and achieve good lamination performance. The functional groups such as -OH in the gelatin / k-carrageenan hydrogel further enhance the self-adhesion performance by forming hydrogen bonds with molecules on the skin surface.

[0074] The structural diagram of the flexible self-driven hydrogel humidity sensor prepared in Example 1 and the schematic diagram of its electrical performance and working principle are shown in the figure. Figure 2 As shown in the figure, the humidity sensor has an overall diameter of 1 cm and a height of about 2 mm. The functional layer uses a combination of natural gelatin and κ-carrageenan to form a porous network with good biocompatibility and moisture adsorption capacity. In addition, the sensor realizes a humidity gradient-driven response mechanism by designing an asymmetric humidity distribution. Gelatin / κ-carrageenan hydrogel is used as the functional layer material, and its molecular structure contains COO - NH 3 + and OSO 3 - These groups can construct efficient ion migration channels under humidity changes, thereby improving the effective electrical migration rate of ions, significantly reducing the energy loss caused by ineffective diffusion, and improving the separation efficiency of positive and negative ions.

[0075] The schematic diagram of the preparation process of gelatin / κ-carrageenan hydrogel in Example 1 is as follows Figure 3 As shown in FIG. 1 , the hydrogel has a rich helical molecular structure, which, as a good energy dissipation mechanism, significantly improves the tensile properties and mechanical strength of the material. Figure 4 As shown in this network, κ-carrageenan molecules are connected by their sulfate groups (OSO 3 - ) and the amino group (NH 3 + ) and carboxyl (COO - ) form a stable electrostatic crosslink. In addition, the -OH and -NH groups between gelatin and κ-carrageenan molecules further form auxiliary crosslinking points through hydrogen bonding. This composite crosslinking network significantly enhances the mechanical properties of the hydrogel, providing excellent stretch resistance and energy dissipation capabilities while maintaining good flexibility.

[0076] Figure 5The schematic diagram of the surface stretching of the gelatin / κ-carrageenan hydrogel in Example 1 shows that the surface stretching performance is remarkable and can achieve a strain rate of up to 700%. This excellent tensile performance is mainly due to the synergistic effect of the dynamic cross-linking network inside the material, including the electrostatic cross-linking and hydrogen bond cross-linking structure between κ-carrageenan and gelatin molecules. The cross-linking network can be dynamically reorganized under the action of external forces, providing an efficient energy dissipation mechanism to ensure that the material maintains structural integrity and functional stability under large deformation conditions.

[0077] Figure 6 Scanning electron microscope images of the cross-sections of gelatin / κ-carrageenan hydrogels with different κ-carrageenan concentrations; wherein, a is a gelatin / κ-carrageenan hydrogel with a κ-carrageenan concentration of 0 wt%, b is a gelatin / κ-carrageenan hydrogel with a κ-carrageenan concentration of 0.2 wt% in Example 3, and c is a gelatin / κ-carrageenan hydrogel with a κ-carrageenan concentration of 0.4 wt% in Example 1. Figure 6 Figure c shows the smallest pores and significantly increased cross-linking density. As the concentration of κ-carrageenan increases, the intermolecular cross-linking points in the hydrogel increase significantly, resulting in a tighter network structure.

[0078] Figure 7 The transparency test results of the gelatin / κ-carrageenan hydrogel in Examples 1-5 are shown in FIG. Figure 7 It can be seen that under different κ-carrageenan concentration conditions, the hydrogels showed high transmittance (over 80%).

[0079] The electrode part of the sensor provided by the embodiment of the present invention is composed of a carbon nanotube fabric electrode and a metal aluminum electrode to form an asymmetric electrode pair. The design of the sensor uses asymmetric humidity distribution to induce directional migration of water in the hydrogel. The treated carbon nanotube fabric electrode has excellent hydrophilic properties and enhances the adsorption and migration of water. The improvement in ion migration efficiency is mainly attributed to the charged groups on the molecular chains of gelatin and κ-carrageenan, among which the gelatin contains positively charged amino groups (–NH 3 + ) and negatively charged carboxyl groups (–COO-), while κ-carrageenan has negatively charged sulfate groups (–SO 4 - ). These charged groups promote the migration of ions through electrostatic interactions, constructing efficient dual ion migration channels, thereby generating strong electrical signals. This design not only improves the sensitivity and signal-to-noise ratio of the sensor, but also ensures that the sensor can fit closely to the skin surface, adapt to the dynamic changes of the skin, and achieve real-time and accurate monitoring of skin moisture.

[0080] The flexible self-driven hydrogel humidity sensor prepared in Example 1 was subjected to an electrical signal test. The test method was as follows: a Keithley 2440 digital source meter, an alligator clip test line, and a digital display thermometer and hygrometer were used to test the open circuit voltage of the flexible self-driven hydrogel humidity sensor (i.e., a moisture power generation device) in a long-term outdoor environment. During the test, the open circuit voltage measurement interval of the digital source meter was set to 1000ms, and the device was placed in an outdoor environment for continuous monitoring.

[0081] Figure 8 The long-term electrical performance test results of the flexible self-driven hydrogel humidity sensor prepared in Example 1 are shown in FIG. Figure 8 It can be seen that the sensor can work continuously and stably for more than 1200 hours at an open circuit voltage of 1.2 V, showing excellent stability and durability.

[0082] Fig. 9 The electrical performance and output power test results of the flexible self-driven hydrogel humidity sensor prepared in Example 1 under different load resistances are shown in FIG. Fig. 9 It can be seen that the output power of the sensor under optimized load conditions can reach 120 microwatts per square centimeter, showing excellent energy conversion efficiency. This performance is due to the efficient ion migration channel and stable cross-linked network structure of the hydrogel material, which ensures high stability and consistency of current generation and power output driven by humidity changes.

[0083] Fig.10 The electrical performance response signal diagram of the flexible self-driven hydrogel humidity sensor prepared in Example 1 to test the humidity of the palm and forehead skin. After the original signal is derivatized and low-pass filtered, the results clearly show the significant differences in humidity signals of different parts. This shows that the sensor can sensitively identify changes in skin humidity in different parts of the human body. This ability is due to the high sensitivity and low noise characteristics of the sensor, as well as the optimized ion migration channel in the hydrogel material.

[0084] Fig.11 The electrical performance response signal diagram of the flexible self-driven hydrogel humidity sensor prepared in Example 1 under different skin humidity conditions. By taking the derivative and low-pass filtering the test data, the results show that the electrical signal response of the sensor is significantly enhanced with the increase of skin humidity. This trend shows that the sensor is highly sensitive to humidity changes and has good response characteristics, with response time and recovery time of 1.2 seconds and 0.9 seconds respectively. The humidity of the test environment is controlled at about 30%, ensuring that the influence of external factors on the experimental results is minimized.

[0085] from Fig.10 and Fig.11It can be seen that the flexible self-driven hydrogel humidity sensor prepared by the present invention is more sensitive to changes in moisture concentration than traditional humidity sensors. The differences in the electrical signal response of the sensor under different skin humidity conditions at different parts; under different skin humidity conditions at the same part, the electrical signal response of the sensor is significantly different, which can effectively reflect the changes in skin surface humidity. This performance provides a reliable solution for real-time monitoring of skin humidity and demonstrates the wide potential of the sensor in practical applications.

[0086] In summary, the flexible self-driven hydrogel skin humidity sensor provided by the present invention can generate significantly different electrical response signals for different skin humidity states. Combined with the post-processing platform, it can achieve accurate and effective detection of the humidity sensor acquisition signal, providing a scientific basis for daily skin care and health management.

[0087] Obviously, the above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art should understand that other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A flexible self-driven hydrogel humidity sensor, characterized in that: The flexible self-driven hydrogel humidity sensor comprises a stacked carbon nanotube fabric electrode, a functional layer and a metal electrode; the functional layer contains gelatin and kappa-carrageenan.

2. The flexible self-driven hydrogel humidity sensor according to claim 1, characterized in that: The mass ratio of gelatin to kappa-carrageenan is (3-5):(0.05-0.1).

3. The flexible self-driven hydrogel humidity sensor according to claim 1, characterized in that: The metal electrode is a metal aluminum electrode.

4. A method for preparing a flexible self-driven hydrogel humidity sensor according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Immersing the fabric in a carbon nanotube dispersion, taking out the impregnated fabric and drying it to obtain a carbon nanotube fabric electrode; S2. mixing water, a humectant, a pH regulator, an ion enhancer and κ-carrageenan until the solution is transparent, adding gelatin, and obtaining a hydrogel solution after the gelatin is completely dissolved, and preparing the hydrogel solution into a hydrogel; S3. The carbon nanotube fabric electrode described in S1, the hydrogel described in S2, and the metal electrode are stacked in order to form a sandwich structure to construct the flexible self-driven hydrogel humidity sensor.

5. The preparation method according to claim 4, characterized in that: In S1, the concentration of carbon nanotubes in the carbon nanotube dispersion is 0.15-0.3 wt%.

6. The preparation method according to claim 4, characterized in that: S1 also includes a step of patterning the obtained carbon nanotube fabric electrode.

7. The preparation method according to claim 4, characterized in that: In S2, the mass ratio of water, moisturizer, pH adjuster, ion enhancer and κ-carrageenan is (7.8-8.2):(5.8-6.2):(1-1.5):(0.88-0.96):(0.05-0.1).

8. The preparation method according to claim 4, characterized in that: In S2, the pH regulator is selected from one or more of sodium citrate, citric acid, sodium malate and sodium lactate; the ion enhancer is selected from one or more of sodium chloride, potassium chloride and magnesium chloride.

9. The preparation method according to claim 4, characterized in that: In S2, the concentration of κ-carrageenan in the hydrogel is 0.1-0.5 wt %.

10. The preparation method according to claim 4, characterized in that: In S2, after adding gelatin, heat at 70-80°C for 3-4h.

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