A 3D-printable hydrogel precursor composition, a dual-network hydrogel, and its preparation method

Abstract

This invention relates to a 3D-printable hydrogel precursor composition, a dual-network hydrogel, and a method for preparing the same. The hydrogel precursor composition of this invention comprises aramid nanofibers, carboxymethyl cellulose, monomers, a crosslinking agent, and a water-soluble photoinitiator.

Description

Technical Field

[0001] This invention belongs to the field of composite materials, specifically relating to a 3D printable hydrogel precursor composition, a dual-network hydrogel, and its preparation method. Background Technology

[0002] Hydrogels are soft materials composed of long-chain polymer networks and water, possessing characteristics such as softness, biocompatibility, and responsiveness to stimuli, leading to their wide application in flexible electronics, biomedicine, and other fields. Early hydrogel preparation primarily employed casting methods, injecting a precursor solution into a mold and initiating polymerization through heating or ultraviolet light to obtain a hydrogel of a specified shape. With the continuous development of 3D printing technology, hydrogels with more complex geometries can be fabricated using 3D printing methods. Based on different printing techniques, these can be categorized into two types: extrusion-based ink-to-write (DIW) technology and surface projection photopolymerization (DLP) technology. Compared to the line-scanning printing method of DIW, DLP uses surface projection ultraviolet light to induce polymerization in a designated area and stack layers, resulting in higher printing efficiency and precision, making it an ideal printing technology for hydrogels. Early research has developed several DLP-based 3D-printed hydrogels, such as highly stretchable polyacrylamide hydrogels, self-healing hydrogels containing numerous hydrogen bonds, and PEGDA hydrogels for cell seeding. However, the mechanical properties of DLP-based 3D printed hydrogels are generally weak, such as strength, fracture toughness, and fatigue performance, and their functional characteristics are relatively simple, which limits their application scope in practice.

[0003] Carboxymethyl cellulose (CMC) is an environmentally friendly hydrophilic anionic polysaccharide obtained by partially replacing the hydroxyl groups of cellulose with carboxymethyl groups. The carboxylic acid groups on the carboxymethyl groups of CMC can provide effective anchoring sites for metal ions, forming a reversible ion-coordinated cross-linked structure.

[0004] Para-aramid nanofibers (ANF) are a novel type of nanofiber prepared from poly(p-phenylene terephthalamide) fibers. Their molecular chains consist of alternating benzene rings and amide bonds, and the chains interact through hydrogen bonds, π-π stacking, and van der Waals forces, resulting in excellent specific modulus, specific strength, and wear resistance. While ANF surfaces lack active functional groups, they readily undergo photoaging and break down under ultraviolet light, forming free radicals that can participate in the photopolymerization reaction of hydrogels. Therefore, they can serve as an effective reinforcing phase for photocurable hydrogels and other composite materials.

[0005] Currently, the preparation of DLP-based 3D printing hydrogels generally involves a trade-off between high strength and toughness, formability, and functionality. Taking shape memory effect and conductivity as examples, achieving shape memory effect usually requires fewer chemical cross-linking points and a loose polymer network, which is not conducive to the formation of printed structures. Introducing conductive ions usually leads to a decrease in mechanical properties and printability. To improve the strength and toughness of hydrogels, constructing a dual-network hydrogel composed of two interpenetrating or semi-interpenetrating polymer networks is an effective strategy. However, its precursor solution usually has a high viscosity, which is suitable for extrusion-based DIW printing but not for DLP 3D printing. Therefore, there is relatively little research on dual-network DLP-printable hydrogels. To improve the formability and printability of hydrogels, certain chemical cross-linking agents need to be added, but this leads to a significant decrease in the toughness and shape memory capacity of the hydrogel.

[0006] The trade-offs between mechanical properties, printability, and functional characteristics of DLP-based 3D printing hydrogels limit their application in fields such as biomedicine and flexible electronics. Summary of the Invention

[0007] Problems to be solved by the invention

[0008] Existing DLP 3D printing hydrogels suffer from weak mechanical properties, limited functional characteristics, difficulty in achieving high-precision printing, and the trade-off between shape memory effect.

[0009] The purpose of this invention is to provide a hydrogel precursor composition that can be fabricated into a hydrogel by 3D printing (e.g., surface projection micro-stereolithography), and the resulting hydrogel has high strength and toughness, as well as functional properties such as shape memory effect and conductivity.

[0010] Solutions for solving problems

[0011] To address the aforementioned problems, the inventors conducted long-term and in-depth research and discovered that by further introducing carboxymethyl cellulose into hydrogels, especially aramid nanofiber-strengthened hydrogels, to form a second network structure, a dual-network hydrogel with high strength and toughness, as well as functional properties such as shape memory effect and conductivity, can be obtained.

[0012] Specifically, the present invention solves the problems of the present invention through the following solutions.

[0013] [1] A hydrogel precursor composition comprising carboxymethyl cellulose, monomers, crosslinking agents and water-soluble photoinitiators, and optionally aramid nanofibers and light absorbers.

[0014] [2] According to the hydrogel precursor composition of [1], the content of the aramid nanofiber is 0-1 wt%; the content of the carboxymethyl cellulose is 0.001-10 wt%; the content of the monomer is 15-60 wt%; the content of the crosslinking agent is 0.01-5 wt%; the content of the water-soluble photoinitiator is 0.1-1.5 wt%; and the content of the light absorber is 0-0.1 wt%.

[0015] Preferably, the weight ratio of the monomer to the crosslinking agent is 100:(0.1-1); the weight ratio of the total weight of the monomer and the crosslinking agent to the weight of the water-soluble photoinitiator is (100-40):1.

[0016] [3] The hydrogel precursor composition according to [1] or [2], wherein,

[0017] The aramid nanofibers are para-aramid nanofibers with an average diameter of 10–500 nm and an aspect ratio of 2000–4000.

[0018] The carboxymethyl cellulose has an average relative molecular mass of 10,000 to 1,000,000 and a degree of carboxymethyl substitution of 0.5 to 0.9.

[0019] The monomer is one or more selected from (meth)acrylamide monomers and (meth)acrylic acid monomers; preferably, the monomer includes one or more selected from (meth)acrylamide monomers and one or more selected from (meth)acrylic acid monomers, more preferably the mass ratio of (meth)acrylamide monomers to (meth)acrylic acid monomers is (1-10):1;

[0020] The crosslinking agent is one or more selected from (meth)acrylic acid and (meth)acrylamide crosslinking agents; wherein the (meth)acrylic acid crosslinking agent is preferably one or more selected from polyfunctional (meth)acrylic acid and its salts and polyfunctional (meth)acrylic esters, more preferably polyethylene glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate; the (meth)acrylamide crosslinking agent is preferably N,N-methylenebisacrylamide; the crosslinking agent is preferably polyethylene glycol diacrylate (PEGDA);

[0021] The water-soluble initiator is selected from one or more of water-soluble aromatic ketones, polycyclic aromatic hydrocarbons, polysilanes, acylphosphonates, azo compounds, and organometallic complex initiators, preferably water-soluble TPO;

[0022] The light absorber is selected from one or more of quinoline yellow, methyl red, and brilliant green.

[0023] [4] A method for preparing the hydrogel precursor composition according to any one of [1] to [3], comprising the following steps:

[0024] Carboxymethyl cellulose is dispersed in water, or in an aqueous dispersion of aramid nanofibers, to obtain a carboxymethyl cellulose dispersion.

[0025] The carboxymethyl cellulose dispersion was mixed with monomers, crosslinking agents and water-soluble photoinitiators to obtain the hydrogel precursor composition.

[0026] [5] A hydrogel comprising carboxymethyl cellulose and a crosslinked polymer, and optionally comprising aramid nanofibers, wherein at least a portion of the aramid nanofibers are covalently linked to the crosslinked polymer.

[0027] [6] A dual-network hydrogel comprising a first network structure and a second network structure, wherein the first network structure is formed of a crosslinked polymer and optionally aramid nanofibers, at least a portion of the aramid nanofibers being covalently linked to the crosslinked polymer; and the second network structure is composed of carboxymethyl cellulose and Fe... 3+ form.

[0028] [7] According to the hydrogel described in [5] or [6], wherein the aramid nanofibers are para-aramid nanofibers with an average diameter of 10 to 500 nm and an aspect ratio of 2000 to 4000; and the content of the aramid nanofibers is 0 to 1 wt%.

[0029] The content of the carboxymethyl cellulose is 0.001–10 wt%.

[0030] The crosslinked polymer content is 15-65 wt%; the crosslinked polymer contains structural units derived from one or more monomers selected from (meth)acrylamide monomers and (meth)acrylic acid monomers; preferably, the crosslinked polymer is formed by polymerization of a raw material composition comprising monomers and crosslinking agents, wherein the monomers are one or more selected from (meth)acrylamide monomers and (meth)acrylic acid monomers; the crosslinking agent is one or more selected from (meth)acrylic acid and (meth)acrylamide crosslinking agents; the weight ratio of the monomer to the crosslinking agent is 100:(0.1-1); the polymerization is preferably photoinitiated polymerization.

[0031] [8] The method for preparing hydrogel according to [5] includes a step of irradiating the hydrogel precursor composition according to any one of [1] to [3] with light;

[0032] Preferably, the hydrogel precursor composition is poured into a mold and then subjected to light irradiation; or the light irradiation is performed simultaneously with the 3D printing of the hydrogel precursor composition.

[0033] Preferably, the light irradiation is performed using light with a wavelength of 365–405 nm;

[0034] Preferably, the light irradiation is performed using digital light processing (DLP) technology with surface projection light curing.

[0035] [9] The method for preparing the dual-network hydrogel according to [6] includes mixing the hydrogel described in [5] with Fe... 3+ The steps of contacting the aqueous solution;

[0036] Preferably, the contact time is 1 to 100 minutes, more preferably 5 to 80 minutes, and even more preferably 10 to 60 minutes;

[0037] Preferably, the contact is achieved by impregnating the hydrogel described in [5] with a solution containing Fe. 3+ It is carried out in an aqueous solution;

[0038] Preferably, the one containing Fe 3+ Fe in aqueous solution 3+ The concentration is 0.01–2 mol / L;

[0039] Preferably, the one containing Fe 3+ The aqueous solution is an aqueous solution of a water-soluble iron salt, wherein the water-soluble iron salt is selected from one or more of ferric nitrate, ferric chloride, and ferric sulfate.

[0040]

[10] The method for preparing the dual-network hydrogel according to [9] further includes reacting Fe with Fe... 3+ The step of immersing the hydrogel in water after contact with the aqueous solution is preferably immersion time of 1 to 24 hours, more preferably 6 to 18 hours, and more preferably the time for the hydrogel to reach swelling equilibrium.

[0041]

[11] Use of the hydrogel according to [5] or the dual-network hydrogel according to [6] for drug delivery or pressure sensor applications.

[0042]

[12] A drug capsule comprising a shell having an internal cavity and a drug contained within the cavity, the shell being made of a dual-network hydrogel according to [6].

[0043]

[13] The drug capsule according to

[12] , wherein the shell forms an opening when in contact with an acid or chelating agent, such that the drug contained in the cavity can be released to the outside of the drug capsule through the opening;

[0044] Preferably, the chelating agent is EDTA·2Na.

[0045]

[14] The method for preparing the drug capsule according to

[12] or

[13] includes the following steps:

[0046] Using any one of the hydrogel precursor compositions described in [1] to [3], a shell precursor with an opening is obtained by digital light processing (DLP) technology with surface projection photocuring;

[0047] The drug is filled into the shell precursor through an opening on the shell precursor;

[0048] Under the action of external force, the opening of the shell precursor is closed, forming a shell with a closed structure that contains the drug in the internal cavity;

[0049] Then with Fe 3+ The drug capsules were obtained by contacting the aqueous solution with the solution.

[0050]

[15] A pressure sensor device comprising the dual-network hydrogel described in [6] and an encapsulation body covering the dual-network hydrogel, the encapsulation body being used to prevent moisture loss from the hydrogel;

[0051] The encapsulation is preferably electrically insulating, more preferably comprising polysiloxane, and even more preferably comprising polydimethylsiloxane.

[0052]

[16] A pressure detection device comprising the pressure sensor element described in

[15] .

[0053]

[17] The pressure detection device according to

[16] further includes a power supply and a circuit board with a resistance detection module, and optionally includes one or more components selected from a housing for housing the various components, a display screen for outputting information, and adjustment buttons.

[0054] The effects of the invention

[0055] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0056] In addition to the chemically cross-linked network formed by monomers and cross-linking agents, the single-network hydrogel of this invention contains carboxymethyl cellulose, which allows it to form a double-network hydrogel with shape memory effect under specific conditions. The double-network hydrogel of this invention has a second network formed by the physical cross-linking of carboxymethyl cellulose and iron ions, thus exhibiting high strength and high toughness mechanical properties, and can be transformed into a single-network hydrogel under specific conditions.

[0057] In the preferred embodiment of this invention, the high-strength and tough hydrogel composite material reinforced with para-aramid nanofibers and carboxymethyl cellulose exhibits advantages such as photoaging and breakage under ultraviolet light irradiation, forming free radicals. The strength and toughness of the hydrogel can be improved through covalent cross-linking points, hydrogen bonds, and long-chain entanglement. Carboxymethyl cellulose can undergo post-treatment to form coordination cross-links with metal ions, constituting a second network layer in the hydrogel, significantly enhancing its strength and toughness.

[0058] The present invention allows for switching between a single-network hydrogel and a dual-network hydrogel to achieve a shape memory effect. The first network layer (a permanently covalently cross-linked network) determines the initial shape (i.e., the permanent shape) of the hydrogel, while the second network layer (a reversibly physically cross-linked network) determines the temporary shape. The reversible physical cross-links can be removed using chelating agents or a low-pH environment, thereby achieving shape recovery. Furthermore, due to the presence of metal ions, this dual-network hydrogel also possesses functional properties such as electrical conductivity.

[0059] The hydrogel composite material of this invention can be used to manufacture complex three-dimensional structures based on DLP 3D printing. The prepared structures possess excellent mechanical properties or functional characteristics such as high strength and toughness, shape memory effect, electrical conductivity, and high resolution. This overcomes the problems of low strength, poor fracture toughness, and limited functional properties of hydrogels in current DLP 3D printing, achieving a balance between excellent printability and effective shape memory effect. Attached Figure Description

[0060] Figure 1 The stress-strain curves are for four single-network hydrogel composite materials with different aramid fiber contents prepared in Example 1.

[0061] Figure 2 Stress-strain curves of four double-network hydrogel composite materials with different aramid fiber contents prepared in Example 1;

[0062] Figure 3 The fracture energy diagrams are for the four dual-network hydrogel composites with different aramid fiber contents prepared in Example 1.

[0063] Figure 4 The fatigue threshold diagrams are for the four dual-network hydrogel composite materials with different aramid fiber contents prepared in Example 1.

[0064] Figure 5 The image shows a photograph of the three-dimensional hydrogel composite material produced by DLP 3D printing in Example 2.

[0065] Figure 6 The images and diagrams show the shape fixation and recovery process of the shape memory hydrogel in Example 3.

[0066] Figure 7This is a schematic diagram illustrating the crosslinking mechanism of a 3D-printable hydrogel precursor composition according to one embodiment of the present invention.

[0067] Figure 8 The images show the hydrogel sheet, drug capsule, and hydrogel sheet restored to its initial shape obtained in Example 4.

[0068] Figure 9 The images show the single-network gel, double-network hydrogel, integrated pressure detection device, and the test conducted using the integrated pressure detection device obtained in Example 5. Detailed Implementation

[0069] The present invention will now be described in detail. The description of the technical features described below is based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples.

[0070] <Terminology and Definitions>

[0071] In this specification, the term "alkyl" includes straight-chain, branched, or cyclic alkyl groups, unless otherwise expressly stated.

[0072] In this specification, "monomer" refers to a compound capable of undergoing polymerization, with a molecular weight of 500 or less, for example, 400 or less, 300 or less, 200 or less, or 100 or less.

[0073] In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0074] In this specification, the numerical range indicated by "above" or "below" refers to the numerical range that includes the stated number.

[0075] In this specification, the word "may" has two meanings: to perform a certain process and not to perform a certain process.

[0076] In this specification, the terms "optionally" or "optionally" are used to indicate the use or non-use of certain substances, components, procedures, application conditions, etc.

[0077] All unit names used in this manual are international standard unit names, and unless otherwise stated, the "%" used refers to weight or mass percentage content.

[0078] In this specification, references to "preferred embodiments," "implementation methods," etc., mean that a specific element (e.g., feature, structure, property, and / or characteristic) related to that embodiment is included in at least one of the embodiments described herein, and may or may not be present in other embodiments. Furthermore, it should be understood that the elements may be combined in any suitable manner in various embodiments.

[0079] <Hydrogel precursor composition>

[0080] One object of the present invention is to provide a hydrogel precursor composition comprising carboxymethyl cellulose, monomers, crosslinking agents and water-soluble photoinitiators, and optionally aramid nanofibers and light absorbers.

[0081] The hydrogel precursor composition of the present invention contains a water-soluble photoinitiator, and therefore can be cured by light irradiation, thereby enabling the fabrication of complex three-dimensional structures using technologies such as 3D printing. Furthermore, when aramid nanofibers are included, during light irradiation, the amide bonds on the surface of the aramid nanofibers break to form free radicals, which can form covalent bonds with the crosslinked polymer formed by the monomer and crosslinking agent, thereby achieving a superior strengthening and toughening effect.

[0082] In one embodiment, the aramid nanofibers are para-aramid nanofibers. Para-aramid nanofibers are composed of poly(p-phenylene terephthalamide) with liquid crystal properties, and their molecular chains are more regularly arranged, resulting in higher strength, and are therefore preferred.

[0083] In one embodiment, the aramid nanofibers have an average diameter of 10–500 nm, preferably 10–300 nm, more preferably 10–100 nm, and an aspect ratio of 2000–4000, preferably 3000–4000. The length of the aramid nanofibers is 20–1200 μm, preferably 30–800 μm, more preferably 30–500 μm. By using aramid nanofibers with an average diameter and aspect ratio within the above ranges, better strengthening and toughening effects can be obtained. Furthermore, the longer the aramid nanofibers and the smaller their diameter, the better their strengthening and toughening effect on hydrogels.

[0084] In one embodiment, the aramid nanofibers in the hydrogel precursor composition of the present invention are present in an amount of 0.001–1 wt%, preferably 0.002–0.9 wt%, more preferably 0.003–0.8 wt%, even more preferably 0.004–0.75 wt%, and even more preferably 0.005–0.7 wt%, 0.006–0.65 wt%, 0.007–0.6 wt%, 0.008–0.55 wt%, 0.009–0.5 wt%, 0.01–0.45 wt%, or 0.015–0. The content of aramid nanofibers is 4 wt%, or 0.02–0.375 wt%, for example, 0.03 wt%, 0.04 wt%, 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, 0.09 wt%, 0.1 wt%, 0.12 wt%, 0.14 wt%, 0.16 wt%, 0.18 wt%, 0.20 wt%, 0.22 wt%, 0.24 wt%, 0.26 wt%, 0.28 wt%, 0.30 wt%, 0.32 wt%, 0.34 wt%, and 0.36 wt%. By keeping the content of aramid nanofibers within the above range, excellent toughening effect can be obtained, while ensuring that the hydrogel precursor composition has a suitable viscosity for 3D printing. If the content of aramid nanofibers is too high, the viscosity of the hydrogel precursor composition will be too high, affecting its application in 3D printing; if the content of aramid nanofibers is too low, sufficient toughening effect cannot be obtained, and the strength of the hydrogel will not meet the requirements.

[0085] In specific implementation schemes, the aramid nanofibers can be obtained commercially through conventional channels, including but not limited to the para-aramid nanofibers from Shandong Jufang New Materials Co., Ltd. used in the following examples.

[0086] In one embodiment, the carboxymethyl cellulose content in the hydrogel precursor composition of the present invention is 0.001–10 wt%, preferably 0.005–9 wt%, more preferably 0.01–8 wt%, further preferably 0.02–7.5 wt%, and even more preferably 0.03–7 wt%, 0.04–6.5 wt%, 0.05–6 wt%, 0.06–5.5 wt%, 0.07–5 wt%, 0.08–4.5 wt%, 0.09–4 wt%, 0.1–3.5 wt%, for example 0. 15wt%, 0.2wt%, 0.25wt%, 0.03wt%, 0.35wt%, 0.4wt%, 0.45wt%, 0.5wt%, 0.55wt%, 0.6wt%, 0.65wt%, 0.7wt%, 0.7 5wt%, 0.8wt%, 0.85wt%, 0.9wt%, 0.95wt%, 1wt%, 1.05wt%, 1.1wt%, 1.15wt%, 1.2wt%, 1.25wt%, 1.3wt%, 1.35wt% , 1.4wt%, 1.45wt%, 1.5wt%, 1.55wt%, 1.6wt%, 1.65wt%, 1.7wt%, 1.75wt%, 1.8wt%, 1.85wt%, 1.9wt%, 2wt%, 2.05 wt%, 2.1wt%, 2.15wt%, 2.2wt%, 2.25wt%, 2.3wt%, 2.35wt%, 2.4wt%, 2.45wt%, 2.5wt%, 2.55wt%, 2.6wt%, 2.65wt %, 2.7wt%, 2.75wt%, 2.8wt%, 2.85wt%, 2.9wt%, 2.95wt%, 3wt%, 3.1wt%, 3.2wt%, 3.25wt%, 3.3wt%, 3.35wt%, 3.4 wt%, 3.45wt%, 3.5wt%, 3.55wt%, 3.6wt%, 3.65wt%, 3.7wt%, 3.75wt%, 3.8wt%, 3.85wt%, 3.9wt%, 3.95wt%, 4wt%.

[0087] In one embodiment, the carboxymethyl cellulose has an average relative molecular mass of 10,000 to 1,000,000, preferably 15,000 to 900,000, more preferably 20,000 to 800,000, and even more preferably 25,000 to 700,000, 30,000 to 600,000, 35,000 to 500,000, 40,000 to 400,000, 45,000 to 300,000, 50,000 to 200,000, 55,000 to 180,000, 60,000 to 160,000, 65,000 to 140,000, 70,000 to 120,000, 75,000 to 110,000, and 80,000 to 100,000.

[0088] In one embodiment, the degree of carboxymethyl substitution of the carboxymethyl cellulose is 0.5 to 0.9, preferably 0.55 to 0.85, 0.6 to 0.8, or 0.65 to 0.75.

[0089] In one embodiment, the monomer content in the hydrogel precursor composition of the present invention is 15-60 wt%, preferably 21-59 wt%, 22-58 wt%, 23-57 wt%, 24-56 wt%, 25-55 wt%, 26-54 wt%, 27-53 wt%, 28-52 wt%, 29-51 wt%, 30-50 wt%, 31-49 wt%, 32-48 wt%, 33-47 wt%, 34-46 wt%, 35-45 wt%, 36-44 wt%, 37-43 wt%, 38-42 wt%, 39-41 wt%, and also, for example, 16 wt%, 17 wt%, 18 wt%, 19 wt%, and 20 wt%.

[0090] The monomer is selected from one or more monomers of (meth)acrylamide and (meth)acrylic acid.

[0091] In this specification, (meth)acrylamide monomers refer to monomers having a (meth)acrylamide group, including acrylamide monomers and methacrylamide monomers. Specific examples of (meth)acrylamide monomers include, but are not limited to, acrylamide, methacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N-isopropylacrylamide, etc.

[0092] In this specification, (meth)acrylic acid monomers refer to monomers having a (meth)acryloyloxy group, wherein (meth)acryloyloxy includes acryloyloxy and methacryloyloxy. (meth)acrylic acid monomers include (meth)acrylic acid and its salts and (meth)acrylic acid ester monomers (e.g., C1-5 alkyl esters of (meth)acrylic acid). Specific examples of (meth)acrylic acid monomers include, but are not limited to, (meth)acrylic acid and its alkali metal or alkaline earth metal salts (e.g., sodium acrylate, potassium acrylate, sodium methacrylate, potassium methacrylate), polyethylene glycol mono(meth)acrylic acid ester, hydroxyethyl (meth)acrylic acid ester, 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate, 2-methacryloyloxyethyl phosphocholine (MPA), etc.

[0093] Preferably, the monomer comprises one or more selected from (meth)acrylamide monomers and one or more selected from (meth)acrylic acid monomers. More preferably, the monomer comprises acrylamide and acrylic acid.

[0094] The content of (meth)acrylamide monomers is 14–50 wt%, preferably 15–48 wt%, 17–45 wt%, 20–40 wt%, 25–35 wt%, 26–34 wt%, 27–33 wt%, 28–32 wt%, 29–31 wt%, for example 30 wt%. The content of (meth)acrylic acid monomers is 1–15 wt%, preferably 2–14 wt%, 3–13 wt%, 4–12 wt%, 5–11 wt%, 6–10 wt%, 7–9 wt%, for example 1.2 wt%, 1.4 wt%, 1.6 wt%, 1.8 wt%, 2 wt%, 2.2 wt%, 2.4 wt%, 8 wt%.

[0095] In one embodiment, the mass ratio of (meth)acrylamide monomers to (meth)acrylic acid monomers is (1-20):1, preferably (1-18):1, (1-16):1, (1-14):1, (1-13):1, (1-10):1, and more preferably (1.5-9):1, (2-8):1, (2.5-7):1, (2.8-6):1, (3-5):1.

[0096] In one embodiment, the crosslinking agent in the hydrogel precursor composition of the present invention is one or more selected from (meth)acrylic acid and (meth)acrylamide crosslinking agents. Specific examples of the (meth)acrylic acid crosslinking agent include, but are not limited to, polyethylene glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate. The (meth)acrylamide crosslinking agent is, for example, N,N-methylenebisacrylamide.

[0097] Preferably, the crosslinking agent is polyethylene glycol diacrylate (PEGDA). The number average molecular weight of PEGDA is 300-3000, preferably 400-2000, more preferably 500-1000, and even more preferably 600-900.

[0098] In one embodiment, the total content of the monomer and the crosslinking agent is 15-65 wt%, preferably 20-60 wt%, and more preferably 30-50 wt%. By keeping the total content of the monomer and the crosslinking agent within the above range, the resulting hydrogel can have excellent mechanical properties while retaining sufficient moisture.

[0099] In one embodiment, the weight ratio of the monomer to the crosslinking agent is 100:(0.1-1), preferably 100:(0.2-0.9), more preferably 100:(0.3-0.8), 100:(0.4-0.7), or 100:(0.5-0.6). Alternatively, based on 100 parts by weight of monomer, the weight content of the crosslinking agent is 0.1-1 parts by weight, preferably 0.2-0.9 parts by weight, more preferably 0.3-0.8 parts by weight, 0.4-0.7 parts by weight, or 0.5-0.6 parts by weight. By keeping the weight ratio (or weight) of the monomer to the crosslinking agent within the above range, the crosslinked polymer obtained by polymerization can have a suitable degree of crosslinking, thereby achieving a balance between the strength and elongation at break of the hydrogel.

[0100] This invention does not impose any particular limitation on water-soluble photoinitiators. Generally, water-soluble photoinitiators include those obtained by adding hydrophilic surfactants or introducing functional groups such as ammonium salts or sulfonates to non-water-soluble photoinitiators to make them water-soluble. By using water-soluble photoinitiators, it is possible to initiate free radical polymerization reactions under light irradiation while avoiding light scattering and diffraction by suspended particles in the hydrogel precursor composition, thus preventing interference with the processing of the hydrogel precursor composition using 3D printing technologies such as digital light processing (DLP) for surface projection curing.

[0101] In one embodiment, the water-soluble photoinitiator is selected from one or more of water-soluble aromatic ketones, polycyclic aromatic hydrocarbons, polysilanes, acylphosphonates, azo compounds, and organometallic complex initiators. Examples include Irgacure 2959, a photoinitiator commercially available from BASF, and 2,4,6-(trimethylbenzoyl)diphenylphosphine oxide (TPO), a water-soluble photoinitiator commercially available from Sigma-Aldrich under product number 906808.

[0102] In one specific implementation, the water-soluble photoinitiator is a commercially available water-soluble TPO nanoparticle photoinitiator, including but not limited to the water-soluble TPO based nanoparticle photoinitiator (product number: 906808) from Sigma-Aldrich mentioned above.

[0103] In one embodiment, the total weight ratio of monomer and crosslinking agent to the water-soluble photoinitiator is (100-40):1. Alternatively, based on 1 part by weight of the photoinitiator, the total weight of monomer and crosslinking agent is 100-40 parts by weight, preferably 95-45 parts by weight, 90-50 parts by weight, 85-55 parts by weight, 80-60 parts by weight, 75-62 parts by weight, or 70-64 parts by weight. By keeping the total weight ratio (or weight) of monomer and crosslinking agent to the water-soluble photoinitiator within the above ranges, the polymerization reaction can proceed sequentially under suitable light irradiation.

[0104] In one embodiment, the hydrogel precursor composition of the present invention may further comprise one or more other components selected from light absorbers, dyes, pigments, polymerization inhibitors, other polymerization initiators, light stabilizers, heat stabilizers, etc. In a preferred embodiment, the hydrogel precursor composition of the present invention further comprises a light absorber, preferably a water-soluble light absorber, said light absorber may be one or more selected from quinoline yellow, methyl red, and brilliant green.

[0105] In one embodiment, the content of the light absorber in the hydrogel precursor composition of the present invention is 0-0.1 wt%, preferably 0.001-0.5 wt%, 0.005-0.1 wt%, 0.008-0.015 wt%, or 0.01-0.012 wt%.

[0106] In one embodiment, the content of other components is 0.001 wt% to 1 wt% based on the total mass of the hydrogel composition, for example, 0.003 wt% to 0.5 wt%, or even 0.005 wt% to 0.1 wt%.

[0107] One object of this invention is to provide a method for preparing the hydrogel precursor composition of this invention, which includes the following steps:

[0108] Carboxymethyl cellulose is dispersed in water, or in an aqueous dispersion of aramid nanofibers, to obtain a carboxymethyl cellulose dispersion.

[0109] The carboxymethyl cellulose dispersion was mixed with monomers, crosslinking agents and water-soluble photoinitiators to obtain the hydrogel precursor composition.

[0110] Preferably, carboxymethyl cellulose is dispersed in an aqueous dispersion of aramid nanofibers to obtain a carboxymethyl cellulose dispersion. In this embodiment, the preparation method of the hydrogel precursor composition of the present invention further includes the following step: mixing aramid nanofibers with water and stirring to obtain an aqueous dispersion of aramid nanofibers.

[0111] In one embodiment, water or an aqueous dispersion of aramid nanofibers is mixed with carboxymethyl cellulose and stirred to obtain a carboxymethyl cellulose dispersion. The stirring time is preferably 1 hour or more, 2 hours or more, 3 hours or more, 4 hours or more, 5 hours or more, or 6 hours or more.

[0112] In one embodiment, the aramid nanofiber content in the aqueous dispersion of the aramid nanofiber is 0.001 to 1 wt%, preferably such that the obtained hydrogel precursor composition meets the range of aramid nanofiber content described above for the hydrogel precursor composition.

[0113] The present invention does not impose any particular limitations on the water used in preparing aqueous dispersions of aramid nanofibers or carboxymethyl cellulose dispersions. However, from the perspective of avoiding the introduction of impurities into the hydrogel, deionized water or distilled water is preferred.

[0114] In the aqueous dispersion of aramid nanofibers obtained by the preparation method of the present invention, the aramid nanofibers are uniformly dispersed, and no obvious stratification occurs in the aqueous dispersion after standing for 30 days.

[0115] In one embodiment, a carboxymethyl cellulose dispersion is mixed with a monomer, a crosslinking agent, and a water-soluble photoinitiator, and stirred to obtain the hydrogel precursor composition. The stirring time is preferably 10 minutes or more, 20 minutes or more, 30 minutes or more, 40 minutes or more, 50 minutes or more, or 60 minutes or more.

[0116] The stirring in the preparation method of this invention can be carried out using any stirring method known in the art, including but not limited to mechanical stirring, magnetic stirring, and ultrasonic dispersion, with magnetic stirring being preferred. Stirring is preferably performed under light-protected conditions to prevent aging of the aramid nanofibers under light irradiation.

[0117] For the aramid nanofibers, monomers, crosslinking agents, and initiators used in the preparation method of this invention, please refer to the corresponding description of the hydrogel precursor composition above.

[0118] The present invention also relates to hydrogel precursor compositions obtained by the preparation method of the present invention.

[0119] <Single-network hydrogel>

[0120] One object of the present invention is to provide a single-network hydrogel comprising carboxymethyl cellulose and a crosslinked polymer, and optionally comprising aramid nanofibers, wherein at least a portion of the aramid nanofibers are covalently linked to the crosslinked polymer.

[0121] In this invention, by connecting at least a portion of the aramid nanofibers to the crosslinked polymer via covalent bonds, excellent toughening effects can be achieved with a relatively small amount of aramid nanofibers added.

[0122] The hydrogel of the present invention can be a photocurable hydrogel. In this case, the covalent bond between the aramid nanofiber and the cross-linked polymer can be formed during the photocuring process. When light is applied during the photocuring process, the aramid nanofiber undergoes photoaging and breaks to form free radicals. These free radicals react with the free radicals on the polymer chain during the polymerization process, thereby forming a covalent bond between the aramid nanofiber and the cross-linked polymer.

[0123] It should be noted that the method described above for forming covalent bonds between aramid nanofibers and cross-linked polymers by irradiating them with light is merely exemplary, and other possible methods for forming covalent bonds between aramid nanofibers and cross-linked polymers are not excluded.

[0124] In one embodiment, the content of the aramid nanofibers in the hydrogel of the present invention is within the same range as described above for the hydrogel precursor composition. The above description of the aramid nanofibers also applies to this embodiment.

[0125] In one embodiment, the carboxymethyl cellulose content in the hydrogel of the present invention is within the same range as described above for the hydrogel precursor composition. The above description of carboxymethyl cellulose also applies to this embodiment.

[0126] In one embodiment, the content of the crosslinking polymer in the hydrogel of the present invention is 15-65 wt%, preferably 22-62 wt%, 24-60 wt%, 26-58 wt%, 28-56 wt%, 30-54 wt%, 32-56 wt%, 34-54 wt%, 36-52 wt%, 38-50 wt%, 40-48 wt%, 42-46 wt%, 44-45 wt%, and also, for example, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, and 21 wt%. By keeping the content of the crosslinking polymer within the above range, the hydrogel can have excellent mechanical properties while retaining sufficient moisture.

[0127] In this invention, the crosslinked polymer refers to a polymer having a three-dimensional network structure. It can be obtained by methods known in the art, for example, by polymerizing monomers and a crosslinking agent, or by further crosslinking the chain polymer with a crosslinking agent, or by using an initiator to crosslink the molecular chains of the chain polymer.

[0128] In one embodiment, the crosslinked polymer is formed by polymerization of a raw material composition comprising monomers and crosslinking agents, preferably by photoinitiated polymerization. For information regarding the types and ratios of monomers and crosslinking agents, as well as the initiator, please refer to the description of the hydrogel precursor composition above.

[0129] In one embodiment, the crosslinked polymer comprises structural units derived from one or more monomers selected from (meth)acrylamide monomers and (meth)acrylate monomers; preferably, the crosslinked polymer is formed by polymerization of a raw material composition comprising a monomer and a crosslinking agent, wherein the monomer is one or more selected from (meth)acrylamide monomers and (meth)acrylate monomers; and the crosslinking agent is one or more multifunctional (meth)acrylate crosslinking agents.

[0130] In one embodiment, the water content in the hydrogel of the present invention is 50-85 wt%, preferably 60-75 wt%.

[0131] The present invention also provides a method for preparing the single-network hydrogel of the present invention, which includes the step of irradiating the hydrogel precursor composition of the present invention with light.

[0132] In one embodiment, the light irradiation is performed using ultraviolet light with a wavelength of 365–405 nm. The specific wavelength can be selected based on the specific photoinitiator.

[0133] In one embodiment, the hydrogel precursor composition of the present invention is poured into a mold and then subjected to light irradiation. The present invention does not impose particular limitations on the size, shape, and material of the mold, and those skilled in the art can select accordingly based on actual needs.

[0134] In one embodiment, the hydrogel of the present invention is prepared from the hydrogel precursor composition of the present invention using 3D printing technology such as surface projection photopolymerization digital light processing technology.

[0135] The digital light processing technology of surface projection photopolymerization uses a high-precision ultraviolet light projection system to slice the three-dimensional model to be printed layer by layer and project it onto the surface of the hydrogel precursor liquid. By stacking the layers one by one, a three-dimensional sample can be directly processed from the digital model.

[0136] Accordingly, this invention relates to hydrogels obtained by the preparation method of this invention.

[0137] When aramid nanofibers are incorporated, the single-network hydrogel of the present invention (hereinafter also referred to as aramid nanofiber-strengthened hydrogel) exhibits excellent mechanical properties.

[0138] In one embodiment, the tensile strength of the aramid nanofiber-reinforced hydrogel of the present invention is 20 kPa or more, preferably 30 kPa or more, more preferably 40 kPa or more, further preferably 50 kPa or more, and even more preferably 60 kPa or more. There is no particular limitation on the upper limit of the tensile strength; it is typically below 500 kPa, or below 400 kPa, or 300 kPa, or even below 200 kPa. The tensile strength of the aramid nanofiber-reinforced hydrogel of the present invention is 1.1 to 30 times that of the original hydrogel, for example, 1.3 to 20 times, for example, 1.4 to 15 times, and even more for example, 1.5 to 12 times, 1.6 to 10 times, 1.7 to 8 times, 1.8 to 6 times, 2 to 4 times, 2.2 to 3.6 times, 1.3 to 3.4 times, 2.4 to 3.2 times, and 2.6 to 3 times.

[0139] Here, "original hydrogel" refers to a hydrogel that has the same composition and content as the aramid nanofiber strengthening hydrogel of the present invention, except that the same amount of water is used to replace the aramid nanofiber dispersion during preparation.

[0140] <Dual-network hydrogel>

[0141] Another object of the present invention is to provide a dual-network hydrogel comprising a first network structure and a second network structure, wherein the first network structure is formed of a crosslinked polymer and optionally aramid nanofibers, at least a portion of the aramid nanofibers being covalently linked to the crosslinked polymer; and the second network structure is composed of carboxymethyl cellulose and Fe... 3+ form.

[0142] In one implementation, the first network structure and the second network structure are interpenetrating network structures.

[0143] Figure 7 The crosslinking mechanism of the hydrogel precursor composition or the dual-network hydrogel of the present invention, as shown in the preferred embodiment, is illustrated. The first network is a UV-induced permanently covalently crosslinked P(AAm-co-AAc) copolymer network, where additional covalent crosslinking points and long-chain entanglements are generated between the para-aramid fibers and the hydrogel polymer chains, forming a hybrid network. Subsequently, the introduction of iron ions enables the carboxyl groups on carboxymethyl cellulose and acrylic acid to form strong metal ion coordination with iron ions. This coordination is a reversible physical crosslinking effect. Therefore, the dual-network hydrogel composite material consists of a permanently covalently crosslinked P(AAm-co-AAc) network and a reversibly physically crosslinked CMC-Fe network. 3+The networks form an interpenetrating double network. The permanently covalently cross-linked network determines the initial shape (i.e., permanent shape) of the hydrogel, while the physically cross-linked network determines the temporary shape. Reversible physical cross-links can be removed by chelating agents (e.g., EDTA·2Na) or in a low pH environment (e.g., pH = 0–3), thereby achieving shape recovery.

[0144] The description of the components and contents of the single-network hydrogel above also applies to the dual-network hydrogel of the present invention.

[0145] In one embodiment, the dual-network hydrogel of the present invention is obtained by reacting a single-network hydrogel with Fe... 3+ It is obtained by contacting an aqueous solution.

[0146] One object of the present invention is to provide a method for preparing a dual-network hydrogel, comprising mixing the single-network hydrogel of the present invention with a Fe-containing... 3+ The step of contacting the aqueous solution.

[0147] Preferably, the contact time is 1 to 100 minutes, more preferably 5 to 80 minutes, and even more preferably 10 to 60 minutes.

[0148] Preferably, the contact is achieved by impregnating a single-network hydrogel with Fe... 3+ It is carried out in an aqueous solution.

[0149] Preferably, the one containing Fe 3+ Fe in aqueous solution 3+ The concentration is 0.01–2 mol / L, preferably 0.05–1.8 mol / L, 0.1–1.6 mol / L, 0.2–1.5 mol / L, 0.3–1.4 mol / L, 0.4–1.3 mol / L, 0.5–1.2 mol / L, 0.6–1.1 mol / L, 0.7–1 mol / L, or 0.8–0.9 mol / L.

[0150] Preferably, the one containing Fe 3+ The aqueous solution is an aqueous solution of a water-soluble iron salt, wherein the water-soluble iron salt is selected from one or more of ferric nitrate, ferric chloride, and ferric sulfate.

[0151] In one embodiment, the method for preparing the dual-network hydrogel further includes reacting it with Fe... 3+ The step of immersing the hydrogel in water after contact with the aqueous solution.

[0152] Preferably, the immersion time in water is 1 to 24 hours, more preferably 6 to 18 hours, and even more preferably the time for the hydrogel to reach swelling equilibrium.

[0153] The present invention also relates to a dual-network hydrogel obtained by the preparation method of the present invention.

[0154] The dual-network hydrogel of this invention has excellent mechanical properties.

[0155] In one embodiment, the tensile strength of the dual-network hydrogel of the present invention is 1500 kPa or more, preferably 1600 kPa or more, more preferably 1700 kPa or more, further preferably 1800 kPa or more, and even more preferably 1900 kPa or more. There is no particular limitation on the upper limit of the tensile strength; it is typically 5000 kPa or less, or 4500 kPa or less, or 4200 kPa, or even 4000 kPa or less.

[0156] The tensile strength of the dual-network hydrogel of this invention is excluding Fe 3+ It is 5 to 50 times, for example 8 to 45 times, for example 9 to 40 times, and for example 10 to 35 times, 11 to 33 times, 12 to 32 times, 13 to 31 times, 14 to 30 times, or 15 to 29 times that of other single-network hydrogels with the same composition.

[0157] In one embodiment, the fracture energy of the dual-network hydrogel of the present invention is 1000 J / m. 2 The preferred value is 1500 J / m. 2 The above, more preferably 2000 J / m 2 The above is further optimized to 2500 J / m 2 The above, or even more preferably 3000 J / m 2 That's all. There is no specific upper limit to the fracture energy; it is typically 5000 J / m. 2 Below, or 4500J / m 2 Below, or 4200J / m 2 Below, or 4000J / m 2 the following.

[0158] For the dual-network hydrogel of the present invention, the fracture energy when aramid nanofibers are included is 1.5 to 15 times that when aramid nanofibers are not included under the same conditions, for example, 1.6 to 12 times, for example, 1.7 to 10 times, 1.8 to 8 times, 1.9 to 6 times, 2 to 4 times, 2.1 to 3 times, 2.2 to 2.8 times, 2.3 to 2.7 times, or 2.4 to 2.5 times.

[0159] In one embodiment, the fatigue threshold of the dual-network hydrogel of the present invention is 10 J / m. 2 The above is preferably 15J / m 2 The above is preferred, with 20 J / m being more ideal. 2 The above is further optimized to 25 J / m 2 The above, or even more preferably 30J / m2 Above, 35J / m 2 That's all. There is no specific upper limit to the fatigue threshold; it is typically 200 J / m. 2 Below, or 150J / m 2 Below, or 100J / m 2 The fatigue threshold of the dual-network hydrogel of the present invention, when containing aramid nanofibers, is 1.5 to 15 times that of the case where other conditions are the same but aramid nanofibers are not included, for example, 1.6 to 12 times, for example, 1.7 to 10 times, and for example, 1.8 to 8 times, 1.9 to 6 times, 2.0 to 5 times, 2.1 to 4 times, and 2.2 to 3 times.

[0160] The present invention also relates to the use of the hydrogel of the present invention in the fields of flexible electronic devices and biomedical engineering.

[0161] <Drug Delivery and Drug Capsules>

[0162] In one embodiment, the object of the present invention is to provide the use of the hydrogel or dual-network hydrogel of the present invention for drug delivery.

[0163] In one embodiment, the present invention provides a drug capsule comprising a shell having an internal cavity and a drug contained within the cavity, the shell being constructed of the dual-network hydrogel of the present invention.

[0164] The present invention also provides a method for preparing the drug capsule of the present invention, which includes the following steps:

[0165] Using the hydrogel precursor composition of the present invention, a shell precursor with an opening is obtained by digital light processing (DLP) technology of surface projection photocuring;

[0166] The drug is filled into the shell precursor through an opening on the shell precursor;

[0167] Under the action of external force, the opening of the shell precursor is closed, forming a shell with a closed structure that contains the drug in the internal cavity;

[0168] Then with Fe 3+ The drug capsules were obtained by contacting the aqueous solution with the solution.

[0169] The various features and preferred embodiments described above for the hydrogel precursor compositions, single-network hydrogels, double-network hydrogels and their preparation methods of the present invention are also applicable to the drug capsules and their preparation methods of the present invention.

[0170] The present invention does not impose any particular limitation on the shape of the shell precursor, which can be any suitable shape, such as sheet, sphere, cylinder, and common capsule shape. For sheet, it can be triangular or polygonal, which can form a closed structure (e.g., tetrahedron, cube, cuboid, etc.).

[0171] When the outer shell of the drug capsule of the present invention comes into contact with an acid (e.g., hydrochloric acid) or a chelating agent (e.g., EDTA·2Na), the reversibly physically cross-linked CMC-Fe present in the dual-network hydrogel... 3+ When the network is disrupted, the outer shell reverts from a closed structure to a sheet, thereby creating an opening in the outer shell (restoring the shape of the shell precursor), allowing the drug contained within the cavity to be released to the outside of the drug capsule through the opening.

[0172] The present invention does not particularly limit the acid that can release the drug, such as hydrochloric acid.

[0173] This invention does not impose any particular limitation on the drug within the drug capsule; it can be a drug for treating or preventing various diseases, such as drugs for treating or preventing various functional and organic diseases. More specifically, it can be a drug for treating or preventing various respiratory diseases, digestive diseases, cardiovascular diseases, genitourinary diseases, and endocrine and metabolic diseases.

[0174] The drug capsule of the present invention can be used for purposes such as drug delivery and drug grasping.

[0175] <Pressure Sensors and Pressure Detection Devices>

[0176] In one embodiment, the object of the present invention is to provide the use of the dual-network hydrogel of the present invention in a pressure sensor. The dual-network hydrogel of the present invention contains Fe... 3+ Ions, therefore, are conductive, and their conductivity changes with the applied pressure, thus they can be used in pressure sensors.

[0177] In one embodiment, the present invention provides a pressure sensor comprising the dual-network hydrogel of the present invention and an encapsulation covering the dual-network hydrogel, the encapsulation being used to prevent moisture loss from the hydrogel.

[0178] Preferably, the package is electrically insulating, for example, made of an electrically insulating polymer material.

[0179] Preferably, the encapsulation body comprises polysiloxane, and more preferably polydimethylsiloxane.

[0180] In one embodiment, the present invention provides a method for preparing the pressure sensor device of the present invention, which includes: preparing the dual-network hydrogel of the present invention as described above, and encapsulating the obtained dual-network hydrogel.

[0181] The present invention does not particularly limit the encapsulation method; it can be carried out by any known suitable method, such as impregnation. Specifically, it can be done by impregnating a dual-network hydrogel into a composition containing the encapsulated body. The impregnation time can be 2 to 20 hours, preferably 4 to 16 hours. The impregnation temperature is 15 to 80°C, preferably 20 to 70°C.

[0182] The composition forming the encapsulation can be, for example, a composition containing polydimethylsiloxane and a curing agent, and specifically can use various commercially available potting compounds, including but not limited to... 194 (Shenzhen Osbon Co., Ltd.), DOWSIL TM 184 (Dow Corning DC184), Momentive RTV615 PDMS, etc.

[0183] More specifically, a polydimethylsiloxane optical potting compound (containing two components, adhesive and curing agent, mixed uniformly at a mass ratio of 10:1) can be used. This compound is poured into a container containing a double-network hydrogel and left to stand at room temperature for 8 to 20 hours (or heated at 60°C for more than 2 hours) to obtain an encapsulation made of polydimethylsiloxane elastomer that covers the double-network hydrogel.

[0184] In one embodiment, the present invention provides a pressure detection device comprising the pressure sensor element of the present invention.

[0185] In one embodiment, the pressure detection device of the present invention further includes a power supply and a circuit board having a resistance detection module.

[0186] Preferably, the power source includes a secondary battery (rechargeable battery), such as a lithium secondary battery or a lithium-ion secondary battery.

[0187] Preferably, the pressure detection device of the present invention further includes a housing for accommodating the various components.

[0188] Preferably, the pressure detection device of the present invention further includes a display screen for outputting information (e.g., displaying measurement results).

[0189] Preferably, the pressure detection device of the present invention further includes an adjustable button, which can realize one or more functions such as power on / off, detection mode switching, unit switching, and sensor calibration.

[0190] Preferably, the pressure detection device of the present invention has one or more of the following detection modes: real-time mass detection mode, real-time force detection mode, force-time variation history curve mode, and impact load mode. The real-time mass detection mode and the real-time force detection mode can reflect the magnitude of the object mass or external force applied to the pressure sensor in real time; the force-time variation history curve mode can record the trend of the magnitude of the external force applied to the pressure sensor over time and plot a force-time variation history curve; the impact load mode can record the maximum value of the external force acting on the pressure sensor over a period of time.

[0191] Example

[0192] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. It should be understood that the detailed descriptions and drawings of the following embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, the embodiments and features described below can be combined with each other unless otherwise specified.

[0193] The raw materials and instruments used in the following examples are described below:

[0194] Para-aramid nanofibers: purchased from Shandong Jufang New Material Co., Ltd., with diameters between 10 and 100 nm and lengths between 30 and 300 μm;

[0195] Carboxymethyl cellulose: Purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., brand name C104983, average molecular weight 90,000, degree of carboxymethyl substitution 0.7;

[0196] Water-soluble TPO nanoparticles: purchased from Sigma-Aldrich, brand name 906808;

[0197] PEGDA: Purchased from Shanghai Coleman Reagent Co., Ltd., brand name KLM211227, average molecular weight 700;

[0198] Fiber debonding machine: The manufacturer is Dongguan Hengke Automation Equipment Co., Ltd.

[0199] Example 1

[0200] (1) Take para-aramid nanofibers with different contents and disperse them in water using a fiber disintegrator to obtain uniform dispersions with para-aramid fiber mass concentrations of 0.125wt%, 0.25wt%, and 0.375wt%.

[0201] (2) Take 6.4g of deionized water and 6.4g of uniform dispersions with mass concentrations of 0.125wt%, 0.25wt%, and 0.375wt% prepared in step (1). Add 0.2g of carboxymethyl cellulose to each of the deionized water and the three solutions. Stir with a magnetic stirrer for more than 6 hours in a dark environment to form a uniform dispersion.

[0202] (3) Add 3g of acrylamide, 0.24g of acrylic acid, 0.01875g of PEGDA, and 0.05g of water-soluble TPO nanoparticles to each of the four dispersions prepared in step (2), and titrate each with deionized water to a final mass of 10g. Stir with a magnetic stirrer for more than 1 hour in a dark environment to form a homogeneous hydrogel precursor solution. The aramid fiber content in the final precursors is 0wt%, 0.08wt%, 0.16wt%, and 0.24wt%, respectively.

[0203] (4) Fill the four hydrogel precursor solutions prepared in step (3) into the polytetrafluoroethylene mold of the dumbbell-shaped specimen conforming to GB / T528-2009, cover it with a transparent acrylic plate and place it in an ultraviolet light box, and irradiate it with 405nm ultraviolet light for 5 minutes to obtain four single-network hydrogel composite materials with different aramid fiber contents.

[0204] (5) Fill the four hydrogel precursor solutions prepared in step (3) into a rectangular mold with a size of 25mm×20mm×0.8mm, cover it with a transparent acrylic plate and place it in an ultraviolet light box, and irradiate it with 405nm ultraviolet light for 4min to obtain four single-network hydrogel composite materials with different aramid fiber contents.

[0205] (6) The single-network hydrogel composite material obtained in steps (4) and (5) was immersed in 0.1M ferric nitrate solution for 30 min, and then transferred to deionized water for more than 12 hours to reach swelling equilibrium, finally obtaining four double-network hydrogel composite materials with different aramid fiber contents. Among them, dumbbell-shaped specimens can be used for uniaxial tensile testing, and rectangular specimens can be used for Rivlin-Thomas fracture testing and fatigue cyclic loading testing.

[0206] Figure 1 Stress-strain curves of four single-network hydrogel composites with different aramid fiber contents are presented. Figure 1 It can be seen that the strength of the single-network hydrogel composites with aramid fiber content of 0.08wt%, 0.16wt%, and 0.24wt% is increased by 59%, 142%, and 270%, respectively, compared with the hydrogel without aramid fiber.

[0207] Figure 2Stress-strain curves of four double-network hydrogel composites with different aramid fiber contents after iron ion treatment are shown. Figure 2 It can be seen that the strength of the dual-network hydrogel composites with aramid fiber content of 0.08wt%, 0.16wt%, and 0.24wt% increased by 25%, 53%, and 79%, respectively, compared with the hydrogel without aramid fiber.

[0208] Will Figure 1 and Figure 2 The comparison shows that the strengths of the four aramid fiber-containing dual-network hydrogel composites (2.0 MPa, 2.5 MPa, 3.1 MPa, and 3.6 MPa, respectively) are increased to 28.5, 22.3, 18.0, and 13.8 times that of the original single-network hydrogel composites. This demonstrates the significant improvement achieved by the addition of aramid fibers and CMC-Fe... 3+ The second network layer significantly improved the strength of the hydrogel, and the increase in strength was not accompanied by a decrease in elongation at break.

[0209] Figure 3 The fracture energy variation curves of four dual-network hydrogel composites are shown. The fracture energy testing method is consistent with that in Nature, 2012, 489(7414):133-136. Figure 3 It can be seen that the fracture energy of the dual-network hydrogel composites with aramid fiber contents of 0.08wt%, 0.16wt%, and 0.24wt% (3675 J / m) is respectively 2 3935J / m 2 4008J / m 2 Compared to hydrogels without aramid fibers, the fracture energy is 1600 J / m. 2 These figures increased by 130%, 146%, and 150%, respectively.

[0210] Figure 4 Fatigue threshold test results for four dual-network hydrogel composites are presented. The test method for fatigue threshold is consistent with that in Extreme Mechanics Letters, 2017, 15:91-96. Figure 4 It can be seen that the fatigue thresholds of the dual-network hydrogel composites with aramid fiber contents of 0.08 wt%, 0.16 wt%, and 0.24 wt% are 48.59 J / m. 2 63.03 J / m 2 79.88J / m 2 The fatigue threshold (25.34 J / m) was increased to that of the untreated aramid fiber hydrogel. 2 1.9, 2.5, and 3.2 times that of ).

[0211] Example 2

[0212] (1) Para-aramid nanofibers were dispersed in water using a fiber dispersing machine to obtain a uniform dispersion with a para-aramid fiber mass concentration of 0.125 wt%.

[0213] (2) Take 25.6g of the uniform dispersion of aramid fiber prepared in step (1), add 0.8g of carboxymethyl cellulose to it, and stir with a magnetic stirrer for more than 6 hours in a dark environment to form a uniform dispersion.

[0214] (3) Add 12g acrylamide, 0.96g acrylic acid, 0.075g PEGDA, 0.2g water-soluble TPO nanoparticles, and 12mg quinoline yellow to the dispersion prepared in step (2), and titrate the final mass with deionized water to 40g. Stir with a magnetic stirrer for more than 1 hour in a dark environment to form a homogeneous hydrogel precursor solution.

[0215] (4) Transfer the hydrogel precursor solution prepared in step (3) into the liquid tank of the DLP 3D printer, set the slice layer thickness to 40 μm, the ultraviolet wavelength to 405 nm, and the ultraviolet light intensity to 58 mW / cm². 2 The bottom layer was exposed for 8 seconds, and the remaining layers were exposed for 6 seconds, resulting in a high-resolution hydrogel structure.

[0216] (5) The high-resolution hydrogel structure printed in step (4) is soaked in 0.1M ferric nitrate solution for 30 min, and then transferred to deionized water for more than 12 hours to reach swelling equilibrium, and finally a high-strength, high-resolution hydrogel structure is obtained.

[0217] Figure 5 The exhibition showcases high-resolution hydrogel 3D lattice structures printed by DLP 3D printing. The top and bottom rows of each structure are photographs of the actual objects before and after immersion in ferric nitrate solution.

[0218] Example 3

[0219] (1) Para-aramid nanofibers were dispersed in water using a fiber dispersing machine to obtain a uniform dispersion with a para-aramid fiber mass concentration of 0.125 wt%.

[0220] (2) Take 6.4g of the uniformly dispersed aramid fiber prepared in step (1), add 0.2g of carboxymethyl cellulose to it, and stir with a magnetic stirrer for more than 6 hours in a dark environment to form a uniformly dispersed liquid.

[0221] (3) Add 3g of acrylamide, 0.24g of acrylic acid, 0.01875g of PEGDA, and 0.05g of water-soluble TPO nanoparticles to the dispersion prepared in step (2), and titrate the final mass of each with deionized water to 10g. Stir with a magnetic stirrer for more than 1 hour in a dark environment to form a homogeneous hydrogel precursor solution.

[0222] (4) Fill the hydrogel precursor solution prepared in step (3) into a cuboid mold with dimensions of 25mm×2mm×1mm, cover it with a transparent acrylic plate and place it in an ultraviolet light box, and irradiate it with 405nm ultraviolet light for 5min to obtain a single-network hydrogel composite material.

[0223] (5) Apply external force to the single-network hydrogel composite material obtained in step (4) and bend it 180° and soak it in 0.8M ferric nitrate solution for 5 minutes. Then, transfer it to deionized water and soak it for 5 minutes to remove excess ferric nitrate solution. Remove the external force to obtain a double-network hydrogel composite material with a fixed shape.

[0224] (6) Immerse the double-network hydrogel with the fixed shape in step (5) in an acidic environment with pH=0. The hydrogel can gradually recover to the initial shape after solidification in step (4). The recovery time is within 3 minutes.

[0225] (7) Immerse the double network hydrogel with the fixed shape in step (5) in a 0.1M chelating agent EDTA·2Na solution. The hydrogel can also gradually recover to the initial shape after solidification in step (4), and the recovery time is within 30 minutes.

[0226] (8) Steps (5), (6) or (5), (7) can be repeated multiple times in a loop.

[0227] Figure 6 The shape memory effect of fiber-reinforced hydrogel composites was demonstrated, enabling shape fixation induced by metal ions and shape recovery induced by pH or chelating agents.

[0228] Figure 7 The crosslinking mechanism of the fiber-reinforced hydrogel composite material was demonstrated. The first network is a UV-induced permanently covalently crosslinked P(AAm-co-AAc) copolymer network. Additional covalent crosslinking points and long-chain entanglements are generated between the para-aramid fibers and the hydrogel polymer chains, forming a hybrid network. Subsequently, the introduction of iron ions enables the carboxyl groups on carboxymethyl cellulose and acrylic acid to form strong metal ion coordination with iron ions. This coordination is a reversible physical crosslinking process. Therefore, this dual-network hydrogel composite material consists of a permanently covalently crosslinked P(AAm-co-AAc) network and a reversibly physically crosslinked CMC-Fe network. 3+The hydrogel forms an interpenetrating double network. The permanently covalently cross-linked network determines the initial shape (i.e., permanent shape) of the hydrogel, while the physically cross-linked network determines the temporary shape. Reversible physical cross-links can be removed using the chelating agent EDTA·2Na or in a low pH environment, thus achieving shape recovery.

[0229] Example 4:

[0230] (1) Para-aramid nanofibers were dispersed in water using a fiber dispersing machine to obtain a uniform dispersion with a para-aramid fiber mass concentration of 0.125 wt%.

[0231] (2) Take 25.6g of the uniform dispersion of aramid fiber prepared in step (1), add 0.8g of carboxymethyl cellulose to it, and stir with a magnetic stirrer for more than 6 hours in a dark environment to form a uniform dispersion.

[0232] (3) Add 12g acrylamide, 0.96g acrylic acid, 0.075g PEGDA, and 0.2g water-soluble TPO nanoparticles to the dispersion prepared in step (2), and titrate with deionized water to a final mass of 40g. Stir with a magnetic stirrer for more than 1 hour in a dark environment to form a homogeneous hydrogel precursor solution.

[0233] (4) Transfer the hydrogel precursor solution prepared in step (3) into the liquid tank of the DLP 3D printer, set the slice layer thickness to 40 μm, the ultraviolet wavelength to 405 nm, and the ultraviolet light intensity to 58 mW / cm². 2 The bottom layer was exposed for 8 seconds, and the remaining layers were exposed for 6 seconds, resulting in a three-dimensional hydrogel sheet.

[0234] (5) Apply external force to the hydrogel sheet printed in step (4), fill it with drug and fix it into a temporary shape with a closed structure, then soak it in 0.8M ferric nitrate solution for 5 minutes, then transfer it to deionized water for 5 minutes to remove excess ferric nitrate solution, remove the external force, and you can get a drug capsule with a fixed shape that encapsulates the drug.

[0235] (6) Immerse the capsule containing the drug, which has been fixed in shape in step (5), in an acidic environment with pH=0. The hydrogel can gradually recover to the initial shape after printing in step (4).

[0236] (7) The capsule containing the drug, whose shape was fixed in step (5), was immersed in a 0.1M chelating agent EDTA·2Na solution. The hydrogel can also gradually recover to the initial shape after printing in step (4).

[0237] (8) Repeat steps (5) and (6) or steps (5) and (7) multiple times.

[0238] Figure 8 The diagram illustrates the DLP 3D printed hydrogel sheet in step (4), the drug capsule with its shape fixed in step (5), and the hydrogel sheet restored to its initial shape in step (6). Figure 8 It is understood that the drug capsule of the present invention can achieve effective shape fixation and shape recovery induced by pH value or chelating agent, so as to realize the function of drug delivery or grasping.

[0239] Example 5:

[0240] (1) Para-aramid nanofibers were dispersed in water using a fiber dispersing machine to obtain a uniform dispersion with a para-aramid fiber mass concentration of 0.125 wt%.

[0241] (2) Take 25.6g of the uniform dispersion of aramid fiber prepared in step (1), add 0.8g of carboxymethyl cellulose to it, and stir with a magnetic stirrer for more than 6 hours in a dark environment to form a uniform dispersion.

[0242] (3) Add 12g acrylamide, 0.96g acrylic acid, 0.075g PEGDA, and 0.2g water-soluble TPO nanoparticles to the dispersion prepared in step (2), and titrate with deionized water to a final mass of 40g. Stir with a magnetic stirrer for more than 1 hour in a dark environment to form a homogeneous hydrogel precursor solution.

[0243] (4) Transfer the hydrogel precursor solution prepared in step (3) into the liquid tank of the DLP 3D printer, set the slice layer thickness to 40 μm, the ultraviolet wavelength to 405 nm, and the ultraviolet light intensity to 58 mW / cm². 2 The bottom layer was exposed for 8 seconds, and the remaining layers were exposed for 6 seconds, resulting in a high-resolution three-dimensional hydrogel structure.

[0244] (5) Soak the hydrogel obtained in step (4) in 0.1M ferric nitrate solution for 30 min, and then soak it in deionized water for more than 12 hours to reach swelling equilibrium, and finally obtain a high-strength, high-resolution, conductive dual-network hydrogel with pressure sensing performance.

[0245] (6) Prepare polydimethylsiloxane optical potting compound ( 194, the two components of adhesive and curing agent are mixed uniformly at a mass ratio of 10:1, and poured into a cuboid cavity mold containing the double network hydrogel obtained in step (5), and left to stand at room temperature for more than 12 hours to obtain a pressure sensor device encapsulated with PDMS elastomer that can effectively prevent hydrogel from losing water.

[0246] (7) Connect the pressure sensor obtained in step (6) to the circuit board containing the resistance detection module, calibrate and standardize it, and assemble it together with the rechargeable battery into a customized instrument box to obtain an integrated pressure detection device.

[0247] Figure 9 The paper displays physical images of the single-network hydrogel obtained by DLP 3D printing in step (4), the double-network hydrogel obtained in step (5), and the integrated pressure detection device assembled in step (7), as well as photographs of various modes of testing using this integrated pressure detection device. The integrated pressure detection device of the present invention has a precise digital display screen, a calibration system that can be calibrated according to different hydrogel properties, adjustable buttons, and a charging module, and can realize four detection modes: real-time mass detection mode, real-time force detection mode, force change history curve mode over time, and impact load (maximum value) mode.

[0248] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

[0249] Industrial availability

[0250] The hydrogel precursor composition of this invention can be used as a resin material for commercial DLP printing companies to print hydrogel soft materials with excellent mechanical properties and multiple functions. The hydrogel of this invention has good conductivity, and its resistance changes with applied strain, making it widely applicable in the field of flexible electronic devices. Unlike traditional sensors, this invention can 3D print conductive hydrogel materials with specific geometries to adapt to different application scenarios.

Claims

1. A dual-network hydrogel, characterized in that, The network includes a first network structure and a second network structure. The first network structure is formed by a cross-linked polymer and aramid nanofibers, with at least a portion of the aramid nanofibers covalently bonded to the cross-linked polymer. The second network structure is composed of carboxymethyl cellulose and Fe... 3+ form; The aramid nanofibers are para-aramid nanofibers with an average diameter of 10–500 nm and an aspect ratio of 2000–4000; the content of the aramid nanofibers is 0.001–1 wt%. The content of the carboxymethyl cellulose is 0.001–10 wt%. The crosslinked polymer content is 15-65 wt%; the crosslinked polymer is formed by polymerization of a raw material composition comprising monomers and crosslinking agents, wherein the monomers include one or more selected from (meth)acrylamide monomers and one or more selected from (meth)acrylic acid monomers; the crosslinking agent is one or more selected from (meth)acrylic acid and (meth)acrylamide crosslinking agents; the weight ratio of the monomer to the crosslinking agent is 100:(0.1-1); the polymerization is photoinitiated polymerization.

2. The dual-network hydrogel according to claim 1, characterized in that, The carboxymethyl cellulose has an average relative molecular mass of 10,000 to 1,000,000 and a degree of carboxymethyl substitution of 0.5 to 0.

9.

3. The dual-network hydrogel according to claim 1, characterized in that, (Meth)acrylic acid crosslinking agents are selected from one or more of polyfunctional (meth)acrylic acid and its salts and polyfunctional (meth)acrylic acid esters, and (meth)acrylamide crosslinking agents are N,N-methylenebisacrylamide.

4. The dual-network hydrogel according to claim 1, characterized in that, (Meth)acrylic crosslinking agents are selected from one or more of polyethylene glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate.

5. The dual-network hydrogel according to claim 1, characterized in that, The crosslinking agent is polyethylene glycol diacrylate (PEGDA).

6. The dual-network hydrogel according to claim 1, characterized in that, The mass ratio of the (meth)acrylamide monomer to the (meth)acrylic acid monomer is (1-20):

1.

7. The dual-network hydrogel according to claim 1, characterized in that, The monomer contains acrylamide and acrylic acid.

8. The method for preparing a dual-network hydrogel according to any one of claims 1 to 7, characterized in that, Includes the following steps: The hydrogel precursor composition was irradiated with light to obtain a single-network hydrogel. The single-network hydrogel is mixed with Fe 3+ Contact with aqueous solution; The hydrogel precursor composition comprises carboxymethyl cellulose, monomers, crosslinking agents, water-soluble photoinitiators, aramid nanofibers, and optionally light absorbers.

9. The preparation method according to claim 8, characterized in that, The hydrogel precursor composition is poured into a mold and then subjected to light irradiation; or the light irradiation is performed simultaneously with 3D printing of the hydrogel precursor composition.

10. The preparation method according to claim 8, characterized in that, The light irradiation is performed using light with a wavelength of 365–405 nm.

11. The preparation method according to claim 8, characterized in that, The light irradiation is performed using digital light processing technology (DLP) with surface projection photopolymerization.

12. The preparation method according to claim 8, characterized in that, The contact time is 1 to 100 minutes.

13. The preparation method according to claim 12, characterized in that, The contact time is 5 to 80 minutes.

14. The preparation method according to claim 13, characterized in that, The contact time is 10 to 60 minutes.

15. The preparation method according to claim 8, characterized in that, The contact is achieved by impregnating the single-network hydrogel with an Fe-containing solution. 3+ It is carried out in an aqueous solution.

16. The preparation method according to claim 15, characterized in that, The containing Fe 3+ Fe in aqueous solution 3+ The concentration is 0.01–2 mol / L.

17. The preparation method according to claim 15, characterized in that, The containing Fe 3+ The aqueous solution is an aqueous solution of a water-soluble iron salt, wherein the water-soluble iron salt is selected from one or more of ferric nitrate, ferric chloride, and ferric sulfate.

18. The method for preparing the dual-network hydrogel according to claim 8, characterized in that, It also includes those containing Fe 3+ The step of immersing the hydrogel in water after contact with the aqueous solution.

19. The preparation method according to claim 18, characterized in that, The soaking time in water is 1 to 24 hours.

20. The preparation method according to claim 19, characterized in that, The soaking time in water is 6 to 18 hours.

21. The preparation method according to claim 19, characterized in that, The immersion time in water is the time required for the hydrogel to reach swelling equilibrium.

22. Use of the dual-network hydrogel according to any one of claims 1 to 7 for drug delivery or pressure sensors.

23. A pharmaceutical capsule, characterized in that, It includes a shell having an internal cavity and a drug contained within the cavity, the shell being made of a dual-network hydrogel according to any one of claims 1 to 7.

24. The drug capsule according to claim 23, characterized in that, The shell forms an opening when in contact with an acid or chelating agent, allowing the drug contained within the cavity to be released to the outside of the drug capsule through the opening.

25. The pharmaceutical capsule according to claim 24, characterized in that, The chelating agent is EDTA·2Na.

26. The method for preparing the drug capsule according to any one of claims 23 to 25, characterized in that, Includes the following steps: A shell precursor with an opening was obtained by using a hydrogel precursor composition and digital light processing (DLP) technology with surface projection photocuring. The drug is filled into the shell precursor through an opening on the shell precursor; Under the action of external force, the opening of the shell precursor is closed, forming a shell with a closed structure that contains the drug in the internal cavity; Then with Fe 3+ The drug capsules were obtained by contacting the aqueous solution with the solution. The hydrogel precursor composition comprises carboxymethyl cellulose, monomers, crosslinking agents, water-soluble photoinitiators, aramid nanofibers, and optionally light absorbers.

27. The method for preparing the dual-network hydrogel according to claim 8 or the method for preparing the drug capsule according to claim 26, characterized in that, The content of the water-soluble photoinitiator is 0.1-1.5 wt%; the content of the light absorber is 0-0.1 wt%.

28. The method for preparing the dual-network hydrogel according to claim 8 or the method for preparing the drug capsule according to claim 26, characterized in that, The total weight ratio of the monomer and crosslinking agent to the water-soluble photoinitiator is (100-40):

1.

29. The method for preparing the dual-network hydrogel according to claim 8 or the method for preparing the drug capsule according to claim 26, characterized in that, The water-soluble photoinitiator is selected from one or more of water-soluble aromatic ketones, polycyclic aromatic hydrocarbons, polysilanes, acylphosphonates, azo compounds, and organometallic complex initiators.

30. The method for preparing the dual-network hydrogel according to claim 8 or the method for preparing the drug capsule according to claim 26, characterized in that, The water-soluble photoinitiator is water-soluble TPO.

31. The method for preparing the dual-network hydrogel according to claim 8 or the method for preparing the drug capsule according to claim 26, characterized in that, The light absorber is selected from one or more of quinoline yellow, methyl red, and brilliant green.

32. A pressure sensor device, characterized in that, The invention includes a dual-network hydrogel according to any one of claims 1 to 7 and an encapsulation body covering the dual-network hydrogel, the encapsulation body being used to prevent moisture loss from the hydrogel.

33. The pressure sensor according to claim 32, characterized in that, The package is electrically insulated.

34. The pressure sensor according to claim 33, characterized in that, The encapsulation body comprises polysiloxane.

35. The pressure sensor according to claim 34, characterized in that, The encapsulation body comprises polydimethylsiloxane.

36. A pressure detection device, characterized in that, The pressure sensor device included in any one of claims 32 to 35.

37. The pressure detection device according to claim 36, characterized in that, It also includes a power supply and a circuit board with a resistance detection module, and optionally includes one or more components selected from a housing for housing the various components, a display screen for outputting information, and adjustment buttons.

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