Conductive hydrogel material, preparation method and application

Abstract

The invention relates to the technical field of hydrogel, in particular to a conductive hydrogel material, a preparation method and application. The conductive hydrogel provided by the invention takes a free radical nano material as a conductive medium; wherein the free radical nano-material comprises ZIF-8-TCNQ NPs anion free radical nano-particles, ZIF-8-TCNQ NPs can form a stable aqueous solution in water, after the ZIF-8-TCNQ NPs aqueous solution is mixed with a hydrogel precursor solution, due to the fact that a photo-crosslinking agent is added into the hydrogel precursor solution, the hydrogel precursor solution is crosslinked and cured under the irradiation of ultraviolet light, and the ZIF-8-TCNQ NPs anion free radical nano-particles are formed. The conductive hydrogel material disclosed by the invention can be obtained. The method is simple and practical, and the prepared conductive hydrogel material has good tissue adhesiveness, flexibility and conductivity and has wide application prospects in the fields of flexible devices, electronic skin and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogels, and in particular to a conductive hydrogel material, a preparation method and an application thereof. Background Art

[0002] Conductive hydrogels are a new class of functional materials that combine electrical conductivity and gelation properties. Due to their high water content, internal porosity, and adjustable swelling properties, they hold great promise for biomedical applications. For example, in biosensors, conductive hydrogels are highly compatible with tissues, enabling accurate detection of various physiological signals within the body, such as heart rate, blood pressure, and neural electrical signals, enabling long-term, real-time health monitoring. In tissue engineering, conductive hydrogels serve as ideal support materials, providing a three-dimensional space for cell growth and proliferation while also promoting cell differentiation, migration, and tissue regeneration. Furthermore, for damaged neural tissue, conductive hydrogels can regulate the growth direction of nerve cells, promoting the recovery of neural function and offering hope for the treatment of neurological diseases. Conductive hydrogels have garnered widespread attention in technologies such as flexible wearable devices and electronic skin due to their excellent flexibility and stretchability. In the electronic skin field, conductive hydrogel electrodes maintain close contact with human skin, enabling efficient and stable signal transmission. Their flexibility also ensures reliability and comfort during various movements.

[0003] Conductive hydrogels, with their unique properties and broad application prospects, have achieved significant development in multiple fields. However, currently, most conductive hydrogels rely on internally doped free ions as a conductive medium for charge transfer. While the preparation process is relatively simple, ionic conductive hydrogels have low conductivity, making them difficult to meet the demands of applications such as efficient and high-frequency charge transfer. Electronic hydrogels, with their excellent electrical conductivity, can effectively reduce energy loss and signal attenuation during charge transfer, ensuring stable and rapid transmission of high-frequency signals, thus meeting the needs of these high-end applications. The conductive medium within the hydrogel is the foundation of electron transport. Currently, the conductive medium within conductive hydrogels is mostly composed of electron-rich nanomaterials such as carbon nanotubes, graphene, metal nanoparticles, or polymers. These conductive media play a key role in the development of conductive hydrogels. However, the rapid development of the conductive hydrogel field and novel materials has placed higher demands on new conductive hydrogels. Therefore, the development of new conductive hydrogels and the exploration of their charge transfer mechanisms are of great significance.

[0004] Free radical nanomaterials generally refer to nanomaterials with free radical electronic structural properties. Due to their electron-rich or electron-deficient states, they are widely used in spin probes, chemical catalysis, photothermal conversion and other fields. Using electron-rich free radical nanomaterials as conductive media in hydrogels and exploring their conductive mechanisms have become research hotspots. However, at this stage, the development of conductive hydrogels based on free radical nanoparticles has the following problems: 1. Free radical nanoparticles react with hydrogel components or crosslinkers, causing free radical electron transfer, which destroys the conductivity of free radical nanoparticles. 2. The hydrogel precursor solution loaded with free radical nanoparticles gels slowly or even fails to gel under external stimuli (ultraviolet light, hydrogen ions or metal ions). Therefore, the development of free radical nanoparticles as conductive media and the development of conductive hydrogel technology controlled by ultraviolet light are of great significance in the study of conductive mechanisms, performance improvement, expansion of application fields, and promotion of material innovation. Summary of the Invention

[0005] The purpose of the present invention is to provide a conductive hydrogel material, a preparation method and an application thereof, so as to achieve the purpose of providing a conductive hydrogel with free radical nanoparticles as a conductive medium.

[0006] To achieve the above-mentioned purpose, the present invention adopts the following technical solution: a conductive hydrogel material, comprising a hydrogel, wherein the hydrogel is doped with a free radical nanomaterial as a conductive medium.

[0007] Furthermore, the hydrogel includes polyacrylamide hydrogel;

[0008] The free radical nanomaterial includes anion free radical molecules and nanoparticles;

[0009] The anion radical molecules include TCNQ (7,7,8,8-tetracyanoquinodimethane), 4F-TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane), TCNE (tetracyanoethylene) and TCNB (1,2,4,5-tetracyanobenzene);

[0010] The preparation materials of the nanoparticles include metal ions and ligands; the metal ions include zinc ions, silver ions, cobalt ions, copper ions and iron ions; the ligands include 2-methylimidazole, diethylimidazole, benzimidazole, imidazole-2-carboxaldehyde, 2-nitroimidazole and 5-chlorobenzimidazole.

[0011] The preparation method of the conductive hydrogel material comprises the following steps:

[0012] S11, preparing a ZIF-8-TCNQ NPs aqueous solution for later use;

[0013] S12, preparing a hydrogel precursor solution for standby use;

[0014] S13. The ZIF-8-TCNQ NPs aqueous solution prepared in S11 and the hydrogel precursor solution prepared in S12 are evenly mixed and solidified to obtain the conductive hydrogel material of the present invention.

[0015] Furthermore, in the S11, the preparation of the ZIF-8-TCNQ NPs aqueous solution comprises the following steps:

[0016] S21, fully mixing the sodium borohydride methanol solution and the tetracyano-p-benzoquinodimethane methanol solution to obtain a TCNQ anion radical methanol solution for standby use;

[0017] S22, fully mixing the zinc acetate methanol solution and the 2-methylimidazole methanol solution, and adding them to S21 to obtain a TCNQ anion radical methanol solution, and washing after sufficient reaction to obtain ZIF-8-TCNQ NPs anion radical nanoparticles;

[0018] S23. Dispersing the ZIF-8-TCNQ NPs anion radical nanoparticles obtained in S22 into water to obtain a ZIF-8-TCNQ NPs aqueous solution.

[0019] Furthermore, in said S12, the preparation of the hydrogel precursor solution comprises the following steps:

[0020] S31, adding N,N'-methylenebisacrylamide aqueous solution to the prepared acrylamide aqueous solution, and adding glycerol and tannic acid in sequence after complete dissolution to obtain a mixed solution;

[0021] S32. Add a cross-linking agent to the mixed solution of S31, and obtain a hydrogel precursor solution after the cross-linking agent is completely dissolved.

[0022] Furthermore, the crosslinking agent is a photocrosslinking agent, including 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone.

[0023] Furthermore, in the above S13, a mixture of the ZIF-8-TCNQ NPs aqueous solution and the hydrogel precursor solution is placed in a mold and cured under ultraviolet light.

[0024] Furthermore, the mold is a PDMS mold with a length of 10 to 20 mm, a width of 3 to 8 mm, and a height of 2 to 6 mm.

[0025] Furthermore, the wavelength of the ultraviolet light is 365nm and the intensity is 150-200μW / cm 2 , the irradiation time is 3 to 5 minutes.

[0026] Application of conductive hydrogel materials in flexible devices and electronic skin.

[0027] Beneficial effects of the present invention:

[0028] The present invention provides a gel system using free radical nanomaterials as a conductive medium. By regulating and balancing the tissue adhesion, flexibility, and conductivity of the hydrogel through component regulation, it provides technical support for bioelectronic devices and flexible devices. The specific technical effects are reflected in the following aspects:

[0029] 1. Based on the nano-confinement stabilization strategy, the present invention prepares free radical nanomaterials that are stable in an aqueous environment, and then loads them into a hydrogel system to stabilize anionic free radicals in the hydrogel system, thereby obtaining the free radical conductive hydrogel of the present invention; it shows great application potential in cutting-edge fields such as flexible devices and electronic skin.

[0030] 2. The present invention adopts molecular design and component optimization strategies to innovatively integrate conductive pathway construction and bioadhesion functions into a single hydrogel system. Specifically, by introducing the synergistic effect of dynamic covalent bonds and hydrophilic polymers, while ensuring the efficiency of electron transmission, the interfacial interaction between the material and skin tissue is significantly enhanced, not only achieving the organic fusion of conductivity and tissue adhesion, but also by introducing a light-responsive module, giving the material intelligent regulation capabilities, providing key technical support for the biocompatible design of flexible electronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a comparison diagram of blank polyacrylamide hydrogel cross-linked by UV light and polyacrylamide conductive hydrogel doped with ZIF-8-TCNQ NPs according to an embodiment of the present invention;

[0032] Figure 2 1 is a conductivity test graph of a blank polyacrylamide hydrogel and a polyacrylamide conductive hydrogel doped with ZIF-8-TCNQ NPs according to an embodiment of the present invention;

[0033] Figure 3 This is a test chart of the skin adhesion performance of the polyacrylamide conductive hydrogel doped with ZIF-8-TCNQ NPs in an embodiment of the present invention. DETAILED DESCRIPTION

[0034] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0035] Existing conductive hydrogels mostly rely on free ions within the gel as a conductive medium. However, the internal ion migration rate of ionic conductive hydrogels is low, resulting in low charge transfer efficiency and susceptibility to external environmental influences, making them unsuitable for high-frequency electronic transmission devices. In particular, when ionic conductive hydrogels couple with metal interfaces, chemical reactions are prone to occur, resulting in a decrease in charge transfer performance. Electronic conductive hydrogels mostly use electrons as a charge transfer medium and have better charge transfer efficiency. Therefore, the development of new electronic conductive hydrogels is particularly important.

[0036] The key to constructing electronic conductive hydrogels lies in the conductive dielectric material. Among the many electron-rich materials, anionic organic free radicals are a relatively special type of electron-rich molecules. However, since free radical molecules have an open-shell electronic structure, they easily react with the surrounding environment (such as water and air) and lose their activity. Therefore, anionic free radicals cannot be directly applied to the hydrogel system.

[0037] This invention is the first to load free radical nanomaterials into hydrogels to prepare electronic conductive hydrogels, enriching the types of electronic hydrogels and providing technical support for fields such as bioelectronic devices, biosensors, electronic skin and flexible electronic devices.

[0038] The conductivity of conductive hydrogel is closely related to the conductive material doped inside. In the present invention, free radical nanomaterials are loaded into the hydrogel precursor solution and the conductive hydrogel is prepared by ultraviolet light excitation technology.

[0039] UV-excited hydrogels offer precise controllability in both time and space, while also being non-invasive and biosafe. This method utilizes photoinitiators under UV light to promote crosslinking of hydrogel substrate molecules. By varying the ratio of photoinitiators, the speed and flexibility of hydrogel formation can be controlled. Furthermore, by varying the duration of UV light exposure, the phase transition and flexibility of the hydrogel can be precisely controlled.

[0040] This method balances the flexibility and skin adhesion of the conductive hydrogel by regulating the ratios of the various components in the gel precursor solution. The method is relatively simple and practical. By adjusting the ratios of N,N'-methylenebisacrylamide (MBAA), glycerol, and tannic acid in the hydrogel precursor mixture, the flexibility of the conductive hydrogel and its adhesion to skin tissue are controlled. By optimizing the acrylamide content and UV exposure time, the tensile and bending properties of the hydrogel are optimized. By regulating the content of free radical nanomaterials in the components, the conductive properties of the hydrogel are optimized.

[0041] Example 1

[0042] The development of the conductive hydrogel in this embodiment is divided into two steps: 1. Encapsulating TCNQ anion radical molecules into the interior of ZIF-8 nanoparticles to obtain ZIF-8-TCNQ NPs free radical nanoparticles that can be stabilized in aqueous solution; 2. Dispersing the prepared ZIF-8-TCNQ NPs into a hydrogel precursor solution, adjusting the ratio of components such as a cross-linking agent, and cross-linking them using ultraviolet light to form a conductive hydrogel. The specific scheme is as follows:

[0043] 1. Add 0.2 mL of sodium borohydride (NaBH4) methanol solution (concentration of 1.2 mg / mL) to 0.5 mL of tetracyanoquinodimethane (TCNQ) methanol solution (concentration of 0.5 mg / mL) (activation). After thorough mixing at room temperature, the color of the tetracyanoquinodimethane methanol solution turned light green.

[0044] 2. Mix 1.0 mL of zinc acetate [Zn(Ac)2, concentration is 0.028 g / mL] methanol solution with 1.0 mL of 2-methylimidazole (concentration is 0.064 g / mL) methanol solution (zinc acetate and dimethylimidazole react quickly, and after mixing the two, quickly add them to the methanol solution of TCNQ anion radical obtained in process 1);

[0045] The TCNQ anion radical methanol solution (0.5 mL) obtained in the above process 1 was quickly added to the above mixed solution, and the mixed methanol solution was placed under magnetic stirring at room temperature for at least 1 hour with a stirring intensity of 400 rpm. The obtained green-milky solution was centrifuged three times with methanol (5000 rpm, 5 min) to wash away the unreacted components, and then dried at 60°C to obtain ZIF-8-TCNQ NPs free radical nanoparticles;

[0046] The obtained anionic radical nanoparticles (ZIF-8-TCNQ NPs) were dispersed in 5 mL of water and refrigerated at 4°C until use.

[0047] 3. Prepare an aqueous solution of acrylamide at a concentration of 0.5 g / mL. Take 1.0 mL of the aqueous solution of acrylamide and add 40 mL of a 20 mg / mL aqueous solution of MBAA. Stir until completely dissolved. Then add 50 mL of glycerol and disperse evenly.

[0048] Then, 400 mL of 60 mg / mL tannic acid was added and mixed thoroughly. 45 mg of 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone (photocrosslinker 2959) was added and vortexed using a homogenizer until all the solids were dissolved.

[0049] The ZIF-8-TCNQ free radical nanoparticle solution in step 2 was added to the prepared hydrogel precursor solution, mixed evenly, and then slowly poured into a PDMS mold (15 mm * 5 mm * 4 mm). The mold was irradiated with UV light for about 3 min (wavelength 365 nm, intensity 180 μW / cm 2 ), and the conductive hydrogel of the present invention can be obtained after curing.

[0050] In order to compare the changes in the conductive properties of polyacrylamide hydrogel after loading ZIF-8-TCNQ NPs into the hydrogel, the blank hydrogel precursor solution and the hydrogel precursor solution doped with ZIF-8-TCNQ NPs were spread into PDMS molds of the same size, and then irradiated with UV light for 3 minutes to form gels; Figure 1 As shown, Figure a is a blank polyacrylamide hydrogel cross-linked by UV light; Figure b is a polyacrylamide conductive hydrogel doped with ZIF-8-TCNQ NPs.

[0051] It can be seen that compared with the blank hydrogel, the hydrogel doped with ZIF-8-TCNQ NPs exhibits a transparent light green color.

[0052] like Figure 2 As shown, the obtained blank polyacrylamide hydrogel and conductive hydrogel were placed under the same voltage respectively to test the current flow; Figure a is the conductivity test of the blank polyacrylamide hydrogel. After the voltage was applied, the brightness of the red LED light was weak; Figure b is the conductivity test of the conductive hydrogel after doping with ZIF-8-TCNQ NPs. After the same voltage was applied, the brightness of the red LED light increased significantly.

[0053] The results showed that compared with the blank polyacrylamide hydrogel (voltage 7.5V, current 3.13mA), after loading ZIF-8-TCNQ NPs, the current passing through the conductive hydrogel became significantly larger (voltage 7.5V, current 15.26mA), making the corresponding LED light brighter; this shows that after loading ZIF-8-TCNQ NPs into the hydrogel, the resistance of the conductive hydrogel decreased and the conductivity increased.

[0054] Generally speaking, loading nanomaterials into gels will affect their tensile properties, flexibility and skin adhesion. The present invention is based on component regulation technology and enhances their skin adhesion properties by adding components such as tannic acid; and balances the flexibility and tensile properties of the gel by regulating the ratio of acrylamide and MBAA.

[0055] like Figure 3As shown, a strip of conductive hydrogel doped with nanomaterials is adhered to the finger joints and bent appropriately; Figure a shows the conductive hydrogel attached to the skin at the finger joints; Figure b shows the bent state of the conductive hydrogel on the skin after the finger is bent; Figure c shows the conductive hydrogel bent and attached to the skin on the back of the finger after the finger is bent about 90°.

[0056] The results showed that during the bending process, the hydrogel remained tightly attached to the surface of the finger skin, demonstrating its good adhesion and flexibility. The present invention can greatly promote the application of conductive hydrogels in electronic skin or flexible wearable fields.

[0057] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, any technical solution that is the same or similar to that of the present application falls within the scope of protection of the present invention.

Claims

1. A conductive hydrogel material, characterized in that: The invention comprises a hydrogel, wherein the hydrogel is doped with free radical nanomaterials as a conductive medium.

2. The conductive hydrogel material according to claim 1, characterized in that: The hydrogel includes polyacrylamide hydrogel; The free radical nanomaterial includes anion free radical molecules and nanoparticles; The anion radical molecules include TCNQ, 4F-TCNQ, TCNE and TCNB; The preparation materials of the nanoparticles include metal ions and ligands; the metal ions include zinc ions, silver ions, cobalt ions, copper ions and iron ions; the ligands include 2-methylimidazole, diethylimidazole, benzimidazole, imidazole-2-carboxaldehyde, 2-nitroimidazole and 5-chlorobenzimidazole.

3. The method for preparing a conductive hydrogel material according to any one of claims 1 to 2, characterized in that: The following steps are involved: S11, preparing a ZIF-8-TCNQ NPs aqueous solution for later use; S12, preparing a hydrogel precursor solution for standby use; S13. The ZIF-8-TCNQ NPs aqueous solution prepared in S11 and the hydrogel precursor solution prepared in S12 are evenly mixed and solidified to obtain the conductive hydrogel material of the present invention.

4. The method for preparing a conductive hydrogel material according to claim 3, wherein: In the S11, the preparation of the ZIF-8-TCNQ NPs aqueous solution comprises the following steps: S21, fully mixing the sodium borohydride methanol solution and the tetracyano-p-benzoquinodimethane methanol solution to obtain a TCNQ anion radical methanol solution for standby use; S22, fully mixing the zinc acetate methanol solution and the 2-methylimidazole methanol solution, and adding them to S21 to obtain a TCNQ anion radical methanol solution, and washing after sufficient reaction to obtain ZIF-8-TCNQ NPs anion radical nanoparticles; S23. Dispersing the ZIF-8-TCNQ NPs anion radical nanoparticles obtained in S22 into water to obtain a ZIF-8-TCNQ NPs aqueous solution.

5. The method for preparing a conductive hydrogel material according to claim 3, wherein: In the above-mentioned S12, the preparation of the hydrogel precursor solution comprises the following steps: S31, adding N,N'-methylenebisacrylamide aqueous solution to the prepared acrylamide aqueous solution, and adding glycerol and tannic acid in sequence after complete dissolution to obtain a mixed solution; S32. Add a cross-linking agent to the mixed solution of S31, and obtain a hydrogel precursor solution after the cross-linking agent is completely dissolved.

6. The method for preparing a conductive hydrogel material according to claim 5, wherein: The crosslinking agent is a photocrosslinking agent, including 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone.

7. The method for preparing a conductive hydrogel material according to claim 6, wherein: In the above-mentioned S13, a mixture of the ZIF-8-TCNQ NPs aqueous solution and the hydrogel precursor solution is placed in a mold and cured under ultraviolet light.

8. The method for preparing a conductive hydrogel material according to claim 7, wherein: The mold is a PDMS mold with a length of 10 to 20 mm, a width of 3 to 8 mm, and a height of 2 to 6 mm.

9. The method for preparing a conductive hydrogel material according to claim 7, wherein: The wavelength of the ultraviolet light is 365nm and the intensity is 150-200μW / cm 2 , the irradiation time is 3 to 5 minutes.

10. Application of the conductive hydrogel material according to any one of claims 1 to 9 in the fields of flexible devices and electronic skin.

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