Preparation Method and Application of a Double-Network Conductive Ionic Hydrogel

Abstract

The present invention relates to a preparation method and application of a double-network conductive ionic hydrogel, belonging to the technical field of hydrogel production processes. This preparation method can use nano-MOFs as raw materials to prepare double-network hydrogel materials, obtaining functional hydrogels with multiple functions such as high stretchability, high sensitivity, self-adhesion, and self-healing. Adsorb Ag in an AgNO3 solution + and further reduce it to elemental Ag to prepare the double-network conductive ionic hydrogel. Applying it to sensors solves the problems of low sensitivity and small sensitive range of current hydrogel flexible sensors. The obtained double-network ionic conductive hydrogel has functions such as high stretchability (~1755%), high sensitivity (~3.3 S / m), adhesiveness, and self-healing, and can be applied to the fields of flexible sensing and motion detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogel production processes, and particularly relates to a preparation method and application of a double-network conductive ionic hydrogel. Background Art

[0002] Disclosing the information of this background art section is only intended to enhance the understanding of the overall background of the present invention, and is not necessarily to be regarded as an admission or any form of implication that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] As a new type of sensor, flexible sensors are more suitable for the measurement needs of organisms. Flexible sensors can convert external stimulus signals received into electrical signals, and have attracted great attention in recent years in fields such as interactive human-machine interfaces, wearable devices, skin prostheses, and three-dimensional printed sensors. Most flexible sensors are prepared by adding conductive materials (such as carbon materials, metal nanomaterials, conductive polymers, etc.) into flexible elastomeric substrates. Among many flexible substrates, hydrogel is a hydrophilic three-dimensional network gel that can quickly absorb water and swell in water and maintain a certain water content, and has this special property between solid and liquid. Therefore, hydrogel substances have advantages such as good flexibility, elasticity, and biocompatibility. However, at the same time, most traditional synthetic hydrogels have poor mechanical properties, which hinders their further application. To solve the deficiency of the mechanical properties of hydrogels, researchers have tried to explore different solutions. Among them, double-network (DN) hydrogels are composed of two cross-linked networks with asymmetric structures and exhibit excellent mechanical properties. Usually, the first network of the double-network hydrogel is relatively rigid and hard, and the second network is soft and tough, so that while taking into account the advantages of traditional hydrogels, the mechanical properties of the hydrogel are also greatly improved.

[0004] Zhang Shiyuan et al. (Construction of a double-network interpenetrating structure conductive hydrogel and its strain sensing performance [J]. Chemical Engineering Technology and Development, 2020, 49(9): 11-16.) used polyacrylamide / polyvinyl alcohol (PAM / PVA) as raw materials to prepare a double-network interpenetrating structure conductive hydrogel through thermal-initiated free radical polymerization reaction and hydrogen bond action. Its elongation at break and tensile fracture stress increased to 577% and 517 kPa respectively. When the tensile strain did not exceed 150%, the GF value of the conductive hydrogel was 0.92; when the tensile strain was in the range of 150% - 300%, the GF value was 1.62.

[0005] CN201811482152.4 discloses a preparation method of a high-strength, high-toughness, sticky and weather-resistant polyvinyl alcohol-based double-network hydrogel. By adding acrylamide, acrylic acid, a cross-linking agent and an initiator to a polyvinyl alcohol solution, heating and then freezing, and then carrying out photo-initiated chemical cross-linking under an ultraviolet lamp, a double-network high-strength polyvinyl alcohol-based hydrogel is prepared. The hydrogel prepared by this method has a fracture strain of (832% - 1332%), and has adhesiveness and water retention.

[0006] However, the hydrogels obtained by the current double-network structure still have defects such as single function or poor mechanical properties, and there is still a certain distance from preparing a flexible sensor that can be actually applied.

[0007] Metal-organic frameworks (MOFs) are called porous coordination polymers, which are porous crystalline materials with a special spatial structure formed by coordinating metal ions and organic ligands through coordination bonds. Therefore, MOFs have a porous framework structure. Due to their ability to include different metal ions and organic ligands, a variety of MOF materials with different molecular structures, topological structures and pore structures have been synthesized in recent years. Due to the spatial structure and composition of MOF materials themselves, MOF materials have good function tunability. For example, by reasonably selecting materials, regulating the addition order, introducing functional groups and other methods, good function selectivity can be given to MOF materials, thereby regulating the application performance of MOFs. Based on the porous structure and function tunability of MOFs themselves, MOFs have been applied in various aspects, such as gas adsorption and separation, energy storage, catalysis, sensing, drug carriers and water treatment.

[0008] However, since most MOFs exist in the form of crystals and powders, it limits their practical applications. Hydrogel is a network structure formed by cross-linking water molecules and polymers, and has high stability and biocompatibility. Combining MOFs with hydrogels can effectively solve the stability problem of MOFs in aqueous solutions, and at the same time can also improve the mechanical properties of hydrogels themselves. Summary of the Invention

[0009] In order to improve the deficiencies of the prior art, the purpose of the present invention is to provide a preparation method and application of a double-network conductive ionic hydrogel. This preparation method can use MOFs as raw materials to prepare double-network hydrogel materials, and obtain functional hydrogels with multiple functions such as high stretchability, high sensitivity, self-adhesion and self-repair.

[0010] In order to achieve the above purpose, the technical solution of the present invention is as follows.

[0011] In the first aspect, a preparation method of a double-network conductive ionic hydrogel is as follows.

[0012] S1. Prepare a 10 wt% polyvinyl alcohol (PVA) solution, add acrylamide (PM) monomer to it, and stir until homogeneous; the mass ratio of the polyvinyl alcohol solution to the acrylamide monomer is 4:1.

[0013] S2. Add MOFs, specifically nano-powder of UIO-66-NH2, to the mixed solution and stir until homogeneous; the addition amount of UIO-66-NH2 is 0.05% - 0.2% of the weight of the mixed solution in S1.

[0014] S3. Add phytic acid (PA) to the mixed solution and stir until homogeneous; the addition amount of phytic acid (PA) is 10% - 20% of the weight of the mixed solution in S1.

[0015] S4. Add tannic acid (TA) to the mixed solution and stir until homogeneous; the addition amount of tannic acid (TA) is 0.1% - 0.2% of the weight of the mixed solution in S1.

[0016] S5. Add initiator and cross-linking agent to the mixed solution and stir evenly.

[0017] S6. Pour the mixed solution into a mold, seal it, and heat it in a water bath to obtain a double-network hydrogel.

[0018] S7. Immerse the double-network hydrogel in silver nitrate solution to obtain a gel strip.

[0019] S8. Place the gel strip under ultraviolet light for illumination to obtain a double-network conductive ionic hydrogel.

[0020] In the second aspect, a double-network conductive ionic hydrogel prepared by the preparation method of the above double-network conductive ionic hydrogel.

[0021] In the third aspect, the application of the above double-network conductive ionic hydrogel in the fields of flexible sensing and motion detection.

[0022] The beneficial effects of the present invention are as follows:

[0023] 1. The preparation process of the double-network ionic conductive hydrogel proposed by the present invention is simple and convenient. A large number of hydrogels containing MOFs can be rapidly prepared by a two-step method. The nano-powder material of MOFs (UiO-66-NH2) is introduced into the hydrogel precursor solution and uniformly dispersed, solving the problem of poor mechanical properties of the double-network hydrogel.

[0024] 2. The double-network ionic conductive hydrogel proposed by the present invention is based on the double-network hydrogel, introducing nano-filler materials of MOFs (UiO-66-NH2), and at the same time introducing tannic acid and phytic acid. In the mixed system, through the action of multiple hydrogen bonds, the mechanical properties, adhesion properties and self-healing properties of the hydrogel are improved.

[0025] 3. The double-network ion-conductive hydrogel proposed by the present invention has functions such as high stretchability (~1755%), high sensitivity (~3.3 S / m), adhesiveness, and self-healing property, and can be applied to flexible sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The attached drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0027] Figure 1 It is a schematic diagram of the preparation and reaction principle of the double-network ion-conductive hydrogel of the present invention.

[0028] Figure 2 It is a stress-strain diagram of the double-network hydrogel in Example 1 of the present invention.

[0029] Figure 3 It is a stress-strain diagram of the double-network hydrogel in Example 2 of the present invention.

[0030] Figure 4 It is a stress-strain diagram of the double-network hydrogel in Example 3 of the present invention.

[0031] Figure 5 It is an infrared spectrogram of the sample, MOFs, and PP double-network hydrogel in Example 5 of the present invention.

[0032] Figure 6 It is an SEM image of the MOF 0.05wt% double-network hydrogel in Example 6 of the present invention.

[0033] Figure 7 It is an SEM image of the MOF 0wt% double-network hydrogel in Example 6 of the present invention.

[0034] Figure 8 It is a photo of the cut double-network conductive ion hydrogel in Example 7 of the present invention.

[0035] Figure 9 It is a photo of the healed double-network conductive ion hydrogel in Example 7 of the present invention.

[0036] Figure 10 It is a photo of the double-network conductive ion hydrogel adhering to various materials in Example 8 of the present invention.

[0037] Figure 11 It is a photo of the double-network conductive ion hydrogel spline fixed at the finger joint and bent in Example 9 of the present invention.

[0038] Figure 12 It is a bending angle-resistance change diagram of the double-network conductive ion hydrogel as a sensor in Example 9 of the present invention. Detailed implementation mode

[0039] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0040] It should be noted that the terms used herein are only for describing the specific implementation mode and are not intended to limit the exemplary implementation mode according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0041] A preparation method of a double-network conductive ionic hydrogel, and the specific steps are as follows.

[0042] S1. Prepare a 10 wt% polyvinyl alcohol solution, add acrylamide monomer thereto, and stir until uniform to obtain a mixed solution; the mass ratio of the polyvinyl alcohol solution to the acrylamide monomer is 4:1.

[0043] S2. Add MOFs, specifically nano-powder of UIO-66-NH2, to the mixed solution and stir until uniform; the addition amount of UIO-66-NH2 is 0.05% - 0.2% of the weight of the mixed solution in S1.

[0044] S3. Add phytic acid (PA) to the mixed solution and stir until uniform.

[0045] The addition amount of the phytic acid (PA) is 10% - 20% of the weight of the mixed solution in S1.

[0046] S4. Add tannic acid (TA) to the mixed solution and stir until uniform.

[0047] The addition amount of the tannic acid (TA) is 0.1% - 0.2% of the weight of the mixed solution in S1.

[0048] S5. Add initiator potassium persulfate (KPS) and crosslinking agent N,N'-methylenebisacrylamide (MBAA) to the mixed solution and stir evenly.

[0049] S6. Add the mixed solution into a glass mold, seal it, and then place it in a preheated water bath at 55 °C and heat for 3 h to obtain a double-network hydrogel.

[0050] S7. Cut the double-network hydrogel into thin slices, immerse them in silver nitrate solution for a period of time to obtain sheet-like gel strips.

[0051] S8. Place the sheet-like gel-like strip under an ultraviolet lamp (365 nm) for 30 min of light irradiation to obtain a double-network conductive ionic hydrogel.

[0052] The reaction principle is as Figure 1 shown: Using polyvinyl alcohol (PVA) and acrylamide (AM) as the substrate, the AM monomer is polymerized through a free radical polymerization reaction to form a chemically cross-linked first-stage polyacrylamide (PAM) network. By introducing metal-organic framework material (UiO-66-NH2), phytic acid (PA), and tannic acid (TA) through a one-pot method, since the amide groups in the PAM chain can easily interact with the functional groups or cations / anions between (PVA), phytic acid (PA), tannic acid (TA), and UiO-66-NH2 and form various interactions (hydrogen bonds, coordination bonds, and π-π interactions), a second-stage physical cross-linked network interpenetrating with PAM is formed in the hydrogel network. The initiator potassium persulfate (KPS) belongs to an inorganic peroxide initiator. After the peroxy group (-O-O-) contained in it is heated, the -O-O- bond breaks and splits into two corresponding free radicals, thus initiating the polymerization of the monomer; the cross-linking agent N,N'-methylenebisacrylamide (MBAA) converts the linear structure into a three-dimensional network structure by copolymerizing with AM.

[0053] Specifically, PA is composed of six phosphate molecules coupled to the inositol ring through ester bonds, and the ester bonds have many anions and hydroxyl groups from ionic / hydrogen bonds; TA is composed of five aromatic rings with triol ends; and UiO-66-NH2 has many metal ions and amino / carboxyl groups. These functional groups or cations / anions can form various interactions. While forming the second-stage physical cross-linked network, the hydrogen bond interaction between tannic acid TA and phytic acid PA and the double-network system endows the hydrogel with adhesion performance and self-healing performance, effectively solving the problem of the single function of the double-network hydrogel and making the hydrogel have excellent self-adhesion and adjustable mechanical properties.

[0054] Finally, by soaking in silver nitrate solution (AgNO3) to adsorb silver ions, excellent conductivity is imparted to the hydrogel under the action of ions / electrons. Further, the silver ions are reduced to Ag elemental nanoparticles (Ag NPs) by ultraviolet irradiation. The interaction between silver nanoparticles can form a channel for connected charge transfer, improving the conductivity of the material. On the other hand, the electrons on the surface of silver nanoparticles have high activity and controllability, and can form an electron cloud layer on the surface, interacting with molecules or ions in the hydrogel system to enhance the conductivity, solving the problems of low sensitivity and small sensitive range of current hydrogel flexible sensors.

[0055] Example 1 - Preparation and performance testing of double-network hydrogels with different UIO-66-NH2 addition amounts.

[0056] The specific steps are as follows:

[0057] S1. Prepare a 10 wt% polyvinyl alcohol solution. Weigh 8 g of the polyvinyl alcohol solution, add 2 g of acrylamide monomer thereto, and stir until homogeneous to obtain 10 g of a mixed solution.

[0058] S2. Add MOFs, specifically the nano-powder of UIO-66-NH2, to the mixed solution, (manually stir with a glass rod for 20 min) and stir until homogeneous; the nano-powder specification of UIO-66-NH2 is (particle size is 300 - 600 nm).

[0059] The addition amount of the UIO-66-NH2 is divided into four cases, which are 0% (0 g), 0.05% (5 mg), 0.1% (10 mg), and 0.2% (20 mg) of the weight of the mixed solution in S1, respectively.

[0060] S3. Add about 10 mg of initiator potassium persulfate (KPS) and about 1 mg of crosslinking agent N,N'-methylenebisacrylamide (MBAA) to the four mixed solutions, and stir evenly.

[0061] S4. Add the four mixed solutions into a glass mold, seal it, and then place it in a preheated water bath at 55 °C and heat for 3 h to obtain four double-network hydrogels.

[0062] Perform tensile property tests on the four obtained sheet-like gel strips, and the obtained results are as Figure 2 shown:

[0063] Figure 2 Among them, MOF 0tw% represents a double-network hydrogel with a UIO-66-NH2 addition amount of 0%, MOF 0.05tw% represents a double-network hydrogel with a UIO-66-NH2 addition amount of 0.05%, MOF 0.1tw% represents a double-network hydrogel with a UIO-66-NH2 addition amount of 0.1%, and MOF 0.2tw% represents a double-network hydrogel with a UIO-66-NH2 addition amount of 0.2%.

[0064] When the addition amount of UIO-66-NH2 is 0.05% of the weight of the mixed solution in S1, the performance is the best, the tensile strength is 0.26 MPa, and the elongation at break is 960%.

[0065] Example 2 - Preparation and performance test of double-network hydrogels with different phytic acid addition amounts.

[0066] The specific steps are as follows:

[0067] S1. Prepare a 10 wt% polyvinyl alcohol solution. Weigh 8 g of the polyvinyl alcohol solution, add 2 g of acrylamide monomer thereto, and stir until homogeneous to obtain 10 g of a mixed solution;

[0068] S2. Add MOFs, specifically the nano-powder of UIO-66-NH2, to the mixed solution, (manually stir with a glass rod for 20 min) until it is uniform. The specification of the UIO-66-NH2 nano-powder is (the particle size is 300 - 600 nm); the addition amount of UIO-66-NH2 is 0.05% (5 mg) of the weight of the mixed solution in S1.

[0069] S3. Add phytic acid (PA) to the mixed solution and stir until it is uniform.

[0070] The addition amounts of the phytic acid (PA) are divided into four cases, which are 0% (0 g), 10% (1.0 g), 15% (1.5 g), and 20% (2.0 g) of the weight of the mixed solution in S1 respectively.

[0071] S4. Add initiator potassium persulfate (KPS) (about 10 mg) and crosslinking agent N,N'-methylenebisacrylamide (MBAA) (about 1 mg) to the four mixed solutions and stir evenly.

[0072] S5. Add the mixed solution into a glass mold, seal it, and then place it in a preheated water bath at 55 °C and heat for 3 h to obtain double-network hydrogels with different amounts of phytic acid added when the addition amount of MOFs is 0.05% of the weight of the mixed solution in S1.

[0073] Perform tensile property tests on the four obtained double-network hydrogels, and the obtained results are as Figure 3 shown:

[0074] Figure 3 In, PPM 0.05 represents that the addition amount of UIO-66-NH2 is 0.05% of the weight of the mixed solution in S1, P0 represents the double-network hydrogel with the addition amount of PA being 0% of the weight of the mixed solution in S1, and P 10 represents the double-network hydrogel with the addition amount of PA being 10%, and P 15 represents the double-network hydrogel with the addition amount of PA being 15%, and P 20 represents the double-network hydrogel with the addition amount of PA being 20%.

[0075] When the addition amount of UIO-66-NH2 is 0.05% of the weight of the mixed solution in S1, the double-network conductive ionic hydrogel with the addition amount of phytic acid being 15% of the weight of the mixed solution in S1 has the best performance, with a tensile strength of 0.25 MPa and an elongation at break of 1210%.

[0076] Example 3 - Preparation and performance test of hydrogels with different tannic acid addition amounts.

[0077] The specific steps are as follows:

[0078] S1. Prepare a 10 wt% polyvinyl alcohol solution. Weigh 8 g of the polyvinyl alcohol solution and add 2 g of acrylamide monomer to it. Stir until homogeneous to obtain 10 g of a mixed solution.

[0079] S2. Add MOFs, specifically UIO-66-NH2, to the mixed solution. Manually stir with a glass rod for 20 min until homogeneous. The nano-powder specification of UIO-66-NH2 is a particle size of 300 - 600 nm.

[0080] The addition amount of the UIO-66-NH2 is 0.05% (5 mg) of the weight of the mixed solution in S1.

[0081] S3. Add phytic acid (PA) to the mixed solution and stir until homogeneous.

[0082] The addition amount of the phytic acid (PA) is 15% (1.5 g) of the weight of the mixed solution in S1.

[0083] S4. Add tannic acid (TA) to the mixed solution and stir until homogeneous.

[0084] The addition amounts of the tannic acid (TA) are divided into four cases, which are 0% (0 mg), 0.10% (10 mg), 0.15% (15 mg), and 0.20% (20 mg) of the weight of the mixed solution in S1, respectively.

[0085] S5. Add approximately 10 mg of initiator potassium persulfate (KPS) and approximately 1 mg of crosslinking agent N,N'-methylenebisacrylamide (MBAA) to the four mixed solutions and stir evenly.

[0086] S6. Add the four mixed solutions into a glass mold. After sealing, place it in a preheated water bath at 55 °C and heat for 3 h to obtain a double-network hydrogel.

[0087] Perform tensile property tests on the four obtained sheet-like gel strips, and the obtained results are as Figure 4 shown.

[0088] Figure 4 In, PPM 0.05 represents that the addition amount of UIO-66-NH2 is 0.05% of the weight of the mixed solution in S1, P 15 represents that the addition amount of phytic acid is 15% of the weight of the mixed solution in S1, T0 represents that the addition amount of tannic acid is 0% of the weight of the mixed solution in S1, T 0.10 represents that the addition amount of tannic acid is 0.10%, T 0.15 represents that the addition amount of tannic acid is 0.15%, T 0.20 represents that the addition amount of tannic acid is 0.20%.

[0089] When the addition amount of UIO-66-NH2 is 0.05%, the addition amount of phytic acid is 15%, and the addition amount of tannic acid is 0.15% of the weight of the mixed solution in S1, the performance of the double-network hydrogel is the best, with a tensile strength of 0.22 MPa and an elongation at break of 1755%.

[0090] Example 4 - Preparation of double-network conductive ionic hydrogel.

[0091] The specific steps are as follows:

[0092] S1. Prepare a 10 wt% polyvinyl alcohol solution. Weigh 8 g of the polyvinyl alcohol solution and add 2 g of acrylamide monomer to it, and stir until uniform to obtain 10 g of a mixed solution.

[0093] S2. Add MOFs to the mixed solution, specifically UIO-66-NH2, and manually stir with a glass rod for 20 min until uniform. The nano-powder specification of UIO-66-NH2 is a particle size of 300 - 600 nm; the addition amount of UIO-66-NH2 is 0.05% (5 mg) of the weight of the mixed solution in S1.

[0094] S3. Add phytic acid (PA) to the mixed solution and stir until uniform; the addition amount of phytic acid (PA) is 15% (1.5 g) of the weight of the mixed solution in S1.

[0095] S4. Add tannic acid (TA) to the mixed solution and stir until uniform; the addition amount of tannic acid (TA) is 0.15% (150 mg) of the weight of the mixed solution in S1.

[0096] S5. Add about 10 mg of initiator potassium persulfate (KPS) and about 1 mg of cross-linking agent N,N'-methylenebisacrylamide (MBAA) to the four mixed solutions and stir evenly.

[0097] S6. Add the four mixed solutions into a glass mold, seal it, and then place it in a preheated water bath at 55 °C and heat for 3 h to obtain a double-network conductive ionic hydrogel.

[0098] S7. Cut the double-network conductive ionic hydrogel into thin slices and immerse them in a silver nitrate solution (0.3 mol / L) for 30 min to obtain sheet-like gel strips.

[0099] S8. Place the sheet-like gel strips under an ultraviolet lamp (365 nm) for 30 min of light irradiation to obtain PPM 0.05 P 15 T 0.15 / AgNPs double-network conductive ionic hydrogel.

[0100] Example 5 - Infrared spectrum test of the hydrogel.

[0101] Figure 5 Representing UiO-66-NH2, PP(PVA / PAM) double-network hydrogel, and PPM obtained in Example 3 0.05 P 15 T 0.15 FTIR spectra of three substances: UiO-66-NH2, double-network hydrogel, and PPM. The absorption peak of UiO-66-NH2 at 1580 cm -1 indicates the presence of -COOH, which can coordinate with Zr in UiO-66-NH2. Meanwhile, the absorption bands at 1506 and 3390 cm 4+ are attributed to C=C and -NH, respectively. -1 For the PP hydrogel, the absorption peaks at 3427 and 1627 cm

[0102] are related to the stretching vibrations of O-H and C=O, respectively. Further comparison shows that these stretching vibration peaks appear and shift in the PPM0.05P15T0.15 double-network hydrogel, demonstrating the successful introduction of UiO-66-NH2 into the PP hydrogel network. -1

[0103] Example 6 - SEM observation of double-network hydrogel.

[0104] Figure 6 Figure 7 SEM images of the MOF 0.05wt% double-network hydrogel obtained in Example 1 Figure 7 SEM images of the MOF 0wt% double-network hydrogel obtained in Example 1. By comparing the pore size in Figure 6 and Figure 7 , it shows that the introduction of UiO-66-NH2 increases the pore size of the hydrogel. Combining with the mechanical property test in Example 1, it indicates that this increase in pore size enhances the mechanical properties of the hydrogel.

[0105] Example 7 - Self-healing performance test of double-network conductive ionic hydrogel.

[0106] The PPM 0.05 P 15 T 0.15 / Ag NPs double-network conductive ionic hydrogel prepared in Example 4 was cut into two segments at room temperature as shown in Figure 8 . Then, the two fractured interfaces were docked and fixed in a sealed container containing a small amount of distilled water and placed in an oven at 65 °C. After 24 h, it was cooled to room temperature and stretched at room temperature. It was found that the hydrogel re-bonded together and maintained certain tensile properties as shown in Figure 9 . This indicates that the prepared PPM 0.05 P 15 T 0.15 double-network hydrogel has self-healing properties.

[0107] Example 8 - Adhesion performance test of double - network conductive ionic hydrogel.

[0108] Figure 10 PPM prepared in Example 4 0.05 P 15 T 0.15 Schematic diagram of the adhesion performance of PPM

[0109] Example 9 - Performance test of the sensor.

[0110] As Figure 11 shown, the PPM 0.05 P 15 T 0.15 / Ag NPs double - network conductive ionic hydrogel prepared in Example 4 was processed into a spline with dimensions of 3 * 10 * 40 mm (thickness * width * length). Copper wires were pulled at both ends and connected to a DM3068 resistance tester. The conductive hydrogel spline was fixed at the finger joint, and the resistance change was detected in real - time during the finger bending process to test the sensing performance and sensing stability of the hydrogel. The bending angles were 0°, 30°, 45°, 60°, and 90°.

[0111] Figure 12 PPM prepared in Example 4 0.05 P 15 T 0.15 / Ag NPs double - network conductive ionic hydrogel as a sensor for sensing performance test.

[0112] By calculating the resistivity through the real - time change of the resistance, when bending at different angles such as 0, 30°, 60°, and 90°, the hydrogel can show relatively sensitive resistance changes in real - time, and the conductivity can remain stable when the finger maintains the bending angle.

[0113] The prepared double - network ionic conductive hydrogel has high sensitivity (~3.3 S / m), and the sensitivity is calculated by σ = L / RS, where L is the length of the test spline (m), R is the initial resistance of the corresponding hydrogel (Ω), and S is the cross - sectional area of the spline (m 2 ²). This high sensitivity is a prerequisite for accurately detecting weak deformations caused by the human body to large - scale deformations caused by joint and muscle movements.

[0114] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a double-network conductive ionic hydrogel, characterized in that the steps Including: S1. Prepare a 10 wt% polyvinyl alcohol solution, add acrylamide monomer thereto, and stir until homogeneous to obtain a mixed solution; The mass ratio of the polyvinyl alcohol solution to the acrylamide monomer is 4:1; S2. Add MOFs, specifically nano-powders of UIO-66-NH2, to the mixed solution and stir until homogeneous; The addition amount of UIO-66-NH2 is 0.05% - 0.2% of the weight of the mixed solution in S1; S3. Add phytic acid to the mixed solution and stir until homogeneous; The addition amount of phytic acid is 10% - 20% of the weight of the mixed solution in S1; S4. Add tannic acid to the mixed solution and stir until homogeneous; The addition amount of tannic acid is 0.1% - 0.2% of the weight of the mixed solution in S1; S5. Add an initiator and a crosslinking agent to the mixed solution; S6. Add the mixed solution into a mold, seal it, and heat it in a water bath to obtain a double-network hydrogel; S7. Immerse the double-network hydrogel in a silver nitrate solution to obtain a gel strip; S8. Place the gel strip under an ultraviolet lamp for illumination to obtain a double-network conductive ionic hydrogel.

2. The preparation method of the double-network conductive ionic hydrogel according to claim 1, characterized in that, The nano-powder specification of UIO-66-NH2 is a particle size of 300 - 600 nm.

3. The preparation method of the double-network conductive ionic hydrogel according to claim 1, characterized in that, In S2, the addition amount of UIO-66-NH2 is 0.05% of the weight of the mixed solution in S1.

4. The preparation method of the double-network conductive ionic hydrogel according to claim 1, characterized in that, In S3, the addition amount of phytic acid is 15% of the weight of the mixed solution in S1.

5. The preparation method of the double-network conductive ionic hydrogel according to claim 1, characterized in that, In S4, the addition amount of tannic acid is 0.15% of the weight of the mixed solution in S1.

6. The preparation method of the double-network conductive ionic hydrogel according to claim 1, characterized in that, In S5, the initiator is potassium persulfate, and the crosslinking agent is N,N'-methylenebisacrylamide. After adding, stir evenly.

7. The preparation method of the double-network conductive ionic hydrogel according to claim 1, characterized in that, In S6, after sealing, place it in a preheated water bath at 55 °C and heat for 3 h.

8. The preparation method of the double-network conductive ionic hydrogel according to claim 1, characterized in that, In S7, the concentration of the silver nitrate solution is 0.3 mol / L.

9. A double-network conductive ionic hydrogel prepared by the preparation method of the double-network conductive ionic hydrogel according to any one of claims 1 - 8.

10. Application of the double-network conductive ionic hydrogel according to claim 9 in the field of flexible sensing or the field of motion detection.

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