Bio-based conductive hydrogel as well as preparation method and application thereof
By immersing gelatin-sodium carboxymethyl cellulose hydrogel in a mixed solution of metal salt and water-glycerol, the problems of poor stability and conductivity of conductive hydrogels are solved, achieving high stability and conductivity of bio-based conductive hydrogels under extreme environments, making them suitable for flexible sensor devices such as respiratory monitoring and humidity sensors.
Patent Information
- Application Number
- CN202511807476.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-03
- Publication Date
- 2026-01-27
AI Technical Summary
Traditional conductive hydrogels exhibit poor stability at high water content, leading to decreased conductivity and difficulty in adapting to environmental changes, thus limiting their application in flexible wearable respiratory monitoring devices.
Gelatin-carboxymethyl cellulose sodium hydrogel was immersed in a mixed solution of metal salt and water-glycerol. The environmental stability and conductivity of the hydrogel were enhanced by the salting-out effect and glycerol. The performance of the hydrogel was improved by doping with metal ions and glycerol.
The prepared bio-based conductive hydrogel maintains high stability and conductivity under extreme environments and has sensitive humidity response, making it suitable for flexible sensor devices, especially for respiratory monitoring and humidity sensors.
Smart Images
Figure CN121405976A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of flexible electronic materials technology, specifically relating to a bio-based conductive hydrogel, its preparation method, and its application. Background Technology
[0002] While traditional medical respiratory monitoring devices can provide effective diagnosis for respiratory diseases, their bulky size, high cost, and poor comfort greatly limit their wider application in medical settings. Furthermore, cumbersome connecting devices can cause patient discomfort and lead to inaccurate diagnostic results. Therefore, it is necessary to develop flexible, portable, and non-invasive remote real-time respiratory monitoring devices.
[0003] The moisture content of exhaled air varies under different respiratory states, thus affecting the humidity level of the surrounding environment. Therefore, humidity sensors can reflect respiratory parameters such as breathing frequency and tidal volume by monitoring changes in ambient humidity. Conductive hydrogels, due to their low modulus, high comfort, ease of doping, and adjustable mechanical properties, are considered promising sensing materials for next-generation flexible wearable respiratory monitoring devices. However, the high water content of current conductive hydrogels leads to poor environmental adaptability, and in daily operation, they face problems such as poor stability due to dehydration and drying, as well as a decrease in conductivity. Summary of the Invention
[0004] The purpose of this invention is to provide a bio-based conductive hydrogel, its preparation method, and its application. The bio-based conductive hydrogel provided by this invention has good environmental stability, conductivity, and sensitive humidity response.
[0005] To achieve the objectives of this invention, the following technical solutions are provided: A method for preparing a bio-based conductive hydrogel includes the following steps: The bio-based conductive hydrogel is obtained by immersing gelatin-sodium carboxymethyl cellulose hydrogel in a metal salt solution; the metal salt solution includes a mixture of metal salt and water-glycerol.
[0006] Preferably, the volume ratio of water to glycerol in the water-glycerol mixed solution is 1~3:1~3.
[0007] Preferably, the soaking time is 1 to 24 hours.
[0008] Preferably, the metal salt includes an organometallic salt and an inorganic metal salt; the mass ratio of the organometallic salt to the inorganic metal salt is 10:0.1~0.5.
[0009] Preferably, the organometal salt includes sodium citrate; the inorganic metal salt includes lithium chloride.
[0010] Preferably, the concentration of the metal salt in the metal salt solution is 5 to 40 wt%.
[0011] Preferably, the mass ratio of gelatin to sodium carboxymethyl cellulose in the gelatin-sodium carboxymethyl cellulose hydrogel is 2:0.02~0.3.
[0012] The bio-based conductive hydrogel prepared by the preparation method described above includes gelatin-sodium carboxymethyl cellulose hydrogel and metal salts and glycerol dispersed in the gelatin-sodium carboxymethyl cellulose hydrogel.
[0013] The above technical solution describes the application of bio-based conductive hydrogel in the preparation of a respiratory monitoring humidity sensor.
[0014] A respiratory monitoring humidity sensor includes the bio-based conductive hydrogel described in the above technical solution.
[0015] This invention provides a method for preparing a bio-based conductive hydrogel, comprising the following steps: immersing a gelatin-sodium carboxymethyl cellulose hydrogel in a metal salt solution to obtain the bio-based conductive hydrogel; the metal salt solution comprises a metal salt and a water-glycerol mixture. This invention fully utilizes the salting-out effect, obtaining the bio-based conductive hydrogel by combining the doping of metal ion salts with the introduction of glycerol.
[0016] The bio-based conductive hydrogel prepared by this invention exhibits excellent conductivity, superior environmental stability, and sensitive humidity response, overcoming the problems of poor stability and conductivity in hydrogels prepared by traditional methods. The bio-based conductive hydrogel of this invention achieves long-term environmental stability in a short time. The hydrogel contains water in three states: free water, weakly bound water, and unfrozen water, each with different freezing points. There is almost no interaction between the free water and the polymer network; therefore, both free water and weakly bound water freeze at around 0°C. The unfrozen water is tightly bound to the gel network, maintaining its liquid mobility even at extreme temperatures. This invention enhances the stability of the hydrogel in extreme environments by introducing glycerol into the gel network. Glycerol can inhibit water evaporation by altering the hydrogen bond network structure between water molecules. After being placed at room temperature for 120 hours, the bio-based conductive hydrogel prepared by this invention still retains over 95% of its mass.
[0017] The bio-based conductive hydrogel prepared in this invention incorporates a metal salt. The addition of the metal salt provides a high concentration of mobile ion carriers, while the hydrogel's own water-rich three-dimensional porous network provides channels for these ions to migrate at high speed, resulting in high conductivity. The bio-based conductive hydrogel prepared in this invention exhibits a low resistance of 50 kΩ and good conductivity.
[0018] The bio-based conductive hydrogel prepared in this invention exhibits sensitive humidity responsiveness, enabling rapid and sensitive responses to respiration under various conditions. Gelatin, as a classic and important biomaterial, possesses excellent biocompatibility, biodegradability, and ease of processing and modification, and is also inexpensive. Gelatin and sodium carboxymethyl cellulose form the framework of the hydrogel; sodium carboxymethyl cellulose not only enhances the mechanical properties of the hydrogel but also improves its responsiveness to humidity. The hydrogel, composed of hydrophilic polymer chains, exhibits highly sensitive hydration and conductivity to humidity changes, enabling high-precision humidity monitoring. When ambient humidity increases, the hydrogel absorbs water, causing it to expand in volume, enhancing the interfacial interaction between water molecules and the conductive material, thus increasing conductivity. Conversely, when humidity decreases, water is released, weakening conductivity. Conductive hydrogels show great potential in the field of humidity monitoring. The bio-based conductive hydrogel prepared in this invention can be widely applied in humidity sensing, extreme high or low temperature environment sensing, respiration monitoring, and flexible sensor devices.
[0019] Furthermore, the preparation method provided by this invention has mild reaction conditions, simple preparation process, convenient operation, and no environmental pollution. Attached Figure Description
[0020] Figure 1 This is a schematic diagram illustrating the preparation method of the bio-based conductive hydrogel prepared according to an embodiment of the present invention; Figure 2 The infrared spectrum of the bio-based conductive hydrogel prepared in Example 4 of this invention; Figure 3 Optical images of the bio-based conductive hydrogel prepared in Example 4 of this invention; Figure 4 This is a water-soluble optical image of the bio-based conductive hydrogel prepared in Example 4 of the present invention; Figure 5 This is a graph showing the trend of conductivity variation of the bio-based conductive hydrogel prepared in Example 4 of the present invention. Figure 6 The graph shows the mass change over time of bio-based conductive hydrogels with different water-glycerol volume ratios prepared in Example 4 of the present invention. Figure 7 The diagram shows the respiratory sensing electrical properties of the bio-based conductive hydrogel prepared in Example 4 of this invention. Detailed Implementation
[0021] This invention provides a method for preparing a bio-based conductive hydrogel, comprising the following steps: The bio-based conductive hydrogel is obtained by immersing gelatin-sodium carboxymethyl cellulose hydrogel in a metal salt solution; the metal salt solution includes a mixture of metal salt and water-glycerol.
[0022] In this invention, unless otherwise specified, all raw materials used in the preparation are preferably commercially available products known to those skilled in the art.
[0023] As one embodiment of the present invention, the preparation method of the gelatin-carboxymethyl cellulose sodium hydrogel includes the following steps: Gelatin, sodium carboxymethyl cellulose, and water are mixed and gelled to form a gelatin-sodium carboxymethyl cellulose hydrogel.
[0024] In one embodiment of the present invention, sodium carboxymethyl cellulose (CMC) is preferably mixed with water to form an aqueous solution of CMC, and then the aqueous solution of CMC is mixed with gelatin to obtain a gelatin-sodium CMC solution. The mixing of CMC and water is carried out under stirring conditions at room temperature for 10-15 hours, specifically 12 hours. The concentration of CMC in the aqueous solution of CMC is 1-3 wt%, specifically 1 wt%, 2 wt%, or 3 wt%. The ratio of CMC to gelatin is 2-10 mL:2 g, specifically 5 mL:2 g. The mixing of CMC and gelatin is carried out under stirring conditions at 40-60°C, specifically 50°C, for 20-40 minutes, specifically 30 minutes. The concentration of the gelatin-sodium CMC solution is 40 wt%.
[0025] In one embodiment of the present invention, the gelation is preferably carried out by pouring the obtained gelatin-sodium carboxymethyl cellulose solution into a mold; the gelation temperature can be 2~6℃, specifically 4℃, and the time can be 4~6min, specifically 5min; the mass ratio of gelatin to sodium carboxymethyl cellulose in the gelatin-sodium carboxymethyl cellulose hydrogel can be 2:0.02~0.3, specifically 2:0.05.
[0026] The metal salt solution of this invention comprises a metal salt and a water-glycerol mixture. As one embodiment of this invention, the preparation method of the metal salt solution includes the following steps: A metal salt is mixed with a water-glycerol mixture to obtain a metal salt solution.
[0027] In one embodiment of the present invention, the metal salt includes an organometallic salt and an inorganic metal salt; the mass ratio of the organometallic salt to the inorganic metal salt can be 10:0.1~0.5, specifically 10:0.3; the organometallic salt includes sodium citrate, and the inorganic metal salt includes lithium chloride. In another embodiment of the present invention, the volume ratio of water to glycerol in the water-glycerol mixed solution can be 1~3:1~3, specifically 1:1, 2:3, 3:2, or 2:1. In yet another embodiment of the present invention, the mixing of the metal salt with the water-glycerol mixed solution is carried out under ultrasonic conditions; the ultrasonic power can be 40 kHz, the temperature can be 25 °C, and the time can be 3~8 min; the concentration of the metal salt in the metal salt solution is 5~40 wt%, more specifically 10~35 wt%.
[0028] This invention involves immersing gelatin-sodium carboxymethyl cellulose hydrogel in a metal salt solution to obtain the bio-based conductive hydrogel. In one embodiment of this invention, the immersion time can be 1–24 hours, specifically 1 hour, 3 hours, 6 hours, 12 hours, or 24 hours; the temperature is room temperature, specifically 25°C.
[0029] The present invention provides a bio-based conductive hydrogel prepared by the preparation method described above, comprising gelatin-sodium carboxymethyl cellulose hydrogel and metal salts and glycerol dispersed within the gelatin-sodium carboxymethyl cellulose hydrogel.
[0030] This invention provides the application of the bio-based conductive hydrogel described in the above technical solution in the preparation of a respiratory monitoring humidity sensor.
[0031] This invention provides a respiratory monitoring humidity sensor, comprising the bio-based conductive hydrogel described in the above technical solution.
[0032] Figure 1 This is a schematic diagram illustrating the preparation method of the bio-based conductive hydrogel according to an embodiment of the present invention. Figure 1 As shown, this invention first prepares a gelatin / sodium carboxymethyl cellulose hydrogel through solution mixing and cooling, and then obtains a bio-based conductive hydrogel by soaking in a metal salt solution. To further illustrate this invention, the technical solutions will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0033] Example 1 Step 1: Weigh 1g of sodium carboxymethyl cellulose using an electronic balance, dissolve it in 99mL of water, and stir magnetically for 12h at room temperature to obtain an aqueous solution of sodium carboxymethyl cellulose; take 5mL of the sodium carboxymethyl cellulose aqueous solution and add 2g of gelatin, stir at 50℃ for 30min to obtain a gelatin-sodium carboxymethyl cellulose solution; take 1mL of the gelatin-sodium carboxymethyl cellulose solution and pour it into a mold, gelatinize at 4℃ for 5min to obtain a gelatin-sodium carboxymethyl cellulose hydrogel.
[0034] Step 2: Weigh 10g of sodium citrate and 0.3g of lithium chloride and dissolve them in 30mL of a water-glycerol mixed solution with a water-glycerol volume ratio of 1:1. Sonicate at 25℃ under an ultrasonic power of 40kHz until dissolved to obtain a metal salt solution.
[0035] Step 3: The gelatin-sodium carboxymethyl cellulose hydrogel was immersed in the metal salt solution at 25°C for 1 h, 3 h, 6 h, 12 h and 24 h respectively, and the resulting bio-based conductive hydrogels were obtained after immersion for different times.
[0036] Example 2 Steps one and three are the same as in Example 1; The difference between step two and example 1 is that the volume ratio of water to glycerol in the water-glycerol mixed solution is 2:1.
[0037] Example 3 Step one is the same as step three in Example 1; The difference between step two and example 1 is that the volume ratio of water to glycerol in the water-glycerol mixed solution is 2:3.
[0038] Example 4 Steps one and three are the same as in Example 1; The difference between step two and example 1 is that the volume ratio of water to glycerol in the water-glycerol mixed solution is 3:2.
[0039] Optical images of the bio-based conductive hydrogel obtained in Example 4 are shown below. Figure 3 As shown. According to Figure 3 It can be seen that the bio-based conductive hydrogel prepared in Example 4 can rapidly gel in 5 min 17 s; it can be made into a transparent film with a thickness of 0.25 mm, or into a personalized custom pattern.
[0040] Test Example 1 The bio-based conductive hydrogel prepared in this invention was subjected to infrared detection, and the results are as follows: Figure 2 As shown. Figure 2 The infrared spectrum of the bio-based conductive hydrogel prepared in Example 4 of this invention; Figure 2 This indicates that the bio-based conductive hydrogel of the present invention has been successfully synthesized.
[0041] Figure 4 This is a water-soluble optical image of the bio-based conductive hydrogel from Example 4 of the present invention. According to... Figure 4 It is known that when the bio-based conductive hydrogel prepared in this invention is placed in water and stirred at 50°C, the bio-based conductive hydrogel can dissolve in water within 10 minutes.
[0042] Test Example 2 Figure 5 This is a graph showing the trend of conductivity variation of the bio-based conductive hydrogel in Example 4 of the present invention. Figure 5 (a) shows the resistance histograms of gelatin-sodium carboxymethyl cellulose hydrogel that has not been soaked in metal salt solution and bio-based conductive hydrogel that has been soaked for 1 h, 3 h, 6 h, 12 h and 24 h, respectively. Figure 5 (b) shows a magnified histogram of the resistance of the bio-based conductive hydrogel after soaking for 1 h, 3 h, 6 h, 12 h, and 24 h, respectively. Figure 5 It is known that the resistance of the gelatin-carboxymethyl cellulose sodium hydrogel is higher than 450 kΩ when it is not immersed in the metal salt solution; after immersing the gelatin-carboxymethyl cellulose sodium hydrogel in the metal salt solution for 1 h, 3 h, 6 h, 12 h and 24 h respectively, the resistance of the bio-based conductive hydrogel is lower than 60 kΩ, indicating that the bio-based conductive hydrogel of the present invention has excellent conductivity.
[0043] Test Example 3 Figure 6 This is a graph showing the mass change over time of bio-based conductive hydrogels with different water-glycerol volume ratios in Example 4 of the present invention. Figure 6 (a) shows the mass change over time of bio-based conductive hydrogels with water-glycerol volume ratios of 2:1, 2:3, 1:1, and 3:2. Figure 6 Image (b) shows optical images of the bio-based conductive hydrogel before and after being placed in air at room temperature for 120 hours. Figure 6 The upper image in (b) is an optical image of the bio-based conductive hydrogel before placement, and the lower image is an optical image of the bio-based conductive hydrogel after being placed in air at room temperature for 120 hours.
[0044] according to Figure 6 As shown in (a), the bio-based conductive hydrogel with a water to glycerol volume ratio of 2:3 retains more than 95% of its mass after 120 h, indicating that the bio-based conductive hydrogel prepared in this invention has excellent environmental stability. Figure 6 As shown in (b), the size of the bio-based conductive hydrogel did not change significantly after being placed in air at room temperature for 120 hours, indicating that the hydrogel has good water retention and did not shrink or become smaller in volume.
[0045] Test Example 4 Figure 7 This is a respiratory sensing electrical diagram of the bio-based conductive hydrogel in Example 4 of the present invention; Figure 7 (a) shows the respiratory sensing electrical diagram monitored by the bio-based conductive hydrogel during rapid breathing; Figure 7 (b) shows the electrical diagram of respiratory sensing monitored by bio-based conductive hydrogel during non-contact humidity sensing; Figure 7 (c) shows the respiratory sensing electrograph monitored by the bio-based conductive hydrogel during respiratory distress; Figure 7 (d) shows the respiratory sensing electrical diagram monitored by the bio-based conductive hydrogel during mouth breathing. Figure 7 As shown, Figure 7 (b) Non-contact humidity sensing refers to bringing a finger close to the hydrogel without touching it; according to Figure 7 As can be seen in (b), there is a slight change in humidity when the fingertip is brought close to the bio-based conductive hydrogel, indicating that the bio-based conductive hydrogel has excellent sensitivity. Figure 7 (a) Figure 7 (c) and Figure 7 The different breathing patterns in (d) show that the bio-based conductive hydrogel exhibits significant electrical responses under different external stimuli, with varying electrical characteristics. When there is no breathing, there is no change in resistance in the horizontal region of the electrical curve, indicating that the bio-based conductive hydrogel of this invention can be used for respiratory monitoring. The bio-based conductive hydrogel prepared by this invention has excellent respiratory monitoring capabilities and can provide timely feedback on respiratory disorders.
[0046] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.
Claims
1. A method for preparing a bio-based conductive hydrogel, comprising the following steps: The bio-based conductive hydrogel was obtained by immersing gelatin-carboxymethyl cellulose sodium hydrogel in a metal salt solution. The metal salt solution comprises a mixture of metal salt and water-glycerol.
2. The preparation method according to claim 1, characterized in that, The volume ratio of water to glycerol in the water-glycerol mixed solution is 1~3:1~3.
3. The preparation method according to claim 1, characterized in that, The soaking time is 1 to 24 hours.
4. The preparation method according to claim 1, characterized in that, The metal salt includes organometallic salts and inorganic metal salts; the mass ratio of the organometallic salt to the inorganic metal salt is 10:0.1~0.
5.
5. The preparation method according to claim 4, characterized in that, The organometal salt includes sodium citrate; the inorganic metal salt includes lithium chloride.
6. The preparation method according to claim 1 or 4, characterized in that, The concentration of the metal salt in the metal salt solution is 5~40wt%.
7. The preparation method according to claim 1, characterized in that, The mass ratio of gelatin to sodium carboxymethyl cellulose in the gelatin-sodium carboxymethyl cellulose hydrogel is 2:0.02~0.
3.
8. The bio-based conductive hydrogel prepared by the preparation method according to any one of claims 1 to 7 comprises gelatin-sodium carboxymethyl cellulose hydrogel and metal salts and glycerol dispersed in the gelatin-sodium carboxymethyl cellulose hydrogel.
9. The application of the bio-based conductive hydrogel of claim 8 in the preparation of a respiratory monitoring humidity sensor.
10. A respiratory monitoring humidity sensor, comprising the bio-based conductive hydrogel of claim 8.