High-sensitivity stretching-pressure dual-mode response hydrogel as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of sensing materials, and discloses high-sensitivity stretching-pressure dual-mode response hydrogel as well as a preparation method and application thereof. The hydrogel comprises the following raw material components: a monomer, an ionic conductive enhancer, an electronic conductive filler, a co-crosslinking agent, a photoinitiator and ionic liquid. The hydrogel disclosed by the invention can give consideration to stretching and pressure dual-mode response at the same time, and is good in environmental stability. Furthermore, the material has good mechanical properties, and the preparation process is simple.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensing materials, and particularly relates to a hydrogel with high-sensitivity tensile-pressure dual-mode response, a preparation method thereof, and an application thereof. Background Art

[0002] In the fields of flexible electronics and sensors, hydrogel materials are regarded as ideal candidate materials for flexible tactile sensors due to their high flexibility, biocompatibility, and adjustable conductivity. Currently, hydrogel-based sensors have shown potential in fields such as wearable devices, robotic electronic skin, and medical monitoring. However, there are still significant deficiencies in the dual-mode response (simultaneous detection of tensile and pressure) of hydrogel materials in the prior art, and the specific problems are as follows:

[0003] (1) Current situation of the prior art and core problems:

[0004] Single-response mode limitation: Most hydrogel sensors are designed for a single physical quantity (such as tensile strain or pressure). For example, ion-conductive hydrogels are sensitive to tensile strain (sensitivity GF≈1-3), but have insufficient response to pressure (sensitivity <1 kPa -1 ); while piezoresistive hydrogels based on conductive fillers (such as carbon nanotubes) are sensitive to pressure (sensitivity about 5 kPa -1 ), but have poor tensile properties (elongation at break <200%) due to uneven dispersion of the fillers.

[0005] Contradiction between sensitivity and range: It is difficult for existing materials to achieve both high sensitivity and a wide detection range simultaneously. For example, although the carbon nanotube CNT / polydimethylsiloxane PDMS composite elastomer can detect pressures in the range of 0.1-100 kPa (sensitivity about 3 kPa -1 ), its tensile deformation ability is limited (<50%), and it cannot adapt to complex deformation scenarios (such as joint bending).

[0006] Defect in environmental stability: Traditional hydrogels are prone to water loss due to the large amount of water they contain, resulting in attenuation of conductivity and deterioration of mechanical properties, which severely limits long-term use (see the literature: Adv. Funct. Mater. 2024, 34, 2409703).

[0007] (2) Deficiencies in the prior art:

[0008] Conflict in the dual-mode response mechanism: Tensile and pressure signals are prone to interference with each other. For example, in ion-conductive hydrogels, the resistance increases during stretching, while it decreases due to the compression of ion channels under pressure, and the superposition of the two makes signal analysis difficult (see the literature: Biomacromolecules 2019, 20, 5, 2096–2104).

[0009] Complex preparation process: Existing dual-mode sensors mostly use multi-layer heterogeneous structures (such as piezoresistive layer + capacitor layer), which require precise assembly processes, are costly and prone to delamination failure.

[0010] Mechanical properties and conductivity are difficult to balance: the lack of chemical bonding between conductive fillers (such as graphene, carbon nanotubes) and hydrophilic gel matrix leads to interfacial slip and filler agglomeration. High filler content will destroy the continuity of the polymer network. The modulus difference between conductive fillers and flexible matrix is ​​significant, and stress concentration points are easily formed at the interface during stretching, resulting in decreased mechanical properties.

[0011] Therefore, it is urgent to solve the technical problems in the prior art that hydrogel materials are difficult to take into account both tensile and pressure dual-mode responses and insufficient environmental stability, and further solve the technical problems in the prior art that the preparation process of hydrogel materials is complex. Summary of the invention

[0012] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a highly sensitive stretch-pressure dual-mode response hydrogel and its preparation method and application. The hydrogel of the present invention can simultaneously take into account the stretching and pressure dual-mode response and good environmental stability. Furthermore, it also has good mechanical properties and a simple preparation process.

[0013] The present invention provides a highly sensitive stretch-pressure dual-mode responsive hydrogel and a preparation method thereof, aiming to achieve the following goals through material design and process innovation:

[0014] (1) Realize dual-mode independent response: By constructing a dual conductive network (ionic / electronic cooperative conductive path), the hydrogel generates independent resistance change signals under tensile deformation (0-500%) and pressure loading (0.1-100 kPa), solving the problems of traditional single response mode and signal coupling interference;

[0015] (2) Improve sensitivity and stability: Optimize the dispersion and interfacial bonding strength of the conductive filler to increase the tensile sensitivity (GF ≥ 2) and pressure sensitivity (≥ 5 kPa -1 ) and reduce the water loss rate (weight loss at room temperature for 7 days ≤ 10%);

[0016] (3) Enhanced mechanical adaptability: Through the synergistic effect of dynamic covalent bonds and physical cross-linking, the hydrogel has both high ductility (elongation at break ≥ 800%) and soft tissue-like elastic modulus (0.1-1MPa), meeting the needs of dynamic robot operation and long-term wear by the human body;

[0017] (4) Simplify the preparation process: A one-step cross-linking method is used to integrate the dual response functions of stretching and pressure in a single material system, avoiding the assembly of multi-layer heterogeneous structures and reducing production costs and process complexity.

[0018] The core objective of the present invention: to provide a hydrogel with a simple process and stable performance and a preparation method thereof, enabling it to achieve highly sensitive tensile-pressure dual-mode independent response in a single material system, and breaking through the application limitations of existing flexible sensors in multi-dimensional force detection.

[0019] The first aspect of the present invention provides a hydrogel with highly sensitive tensile-pressure dual-mode response.

[0020] Specifically, a hydrogel with highly sensitive tensile-pressure dual-mode response, the raw material components of which include monomers, ionic conductive enhancers, electronic conductive fillers, co-crosslinking agents, photoinitiators, and ionic liquids.

[0021] Preferably, the monomers include at least one of acrylamide, AMPS (2-acrylamido-2-methylpropanesulfonic acid) and its salts, acrylic acid and its salts. The monomers form a three-dimensional network structure after reaction and serve as the main framework material of the hydrogel. Further preferably, the monomers are monomers containing ionic groups.

[0022] Preferably, the ionic conductive enhancer includes at least one of lithium magnesium silicate nanosheets, montmorillonite, and lithium magnesium aluminum silicate nanosheets. Further preferably, it is lithium magnesium silicate nanosheets.

[0023] Preferably, the electronic conductive filler includes at least one of MXene (a two-dimensional material), molybdenum disulfide, carbon nanotubes, graphene, or graphene oxide. The electronic conductive filler provides an electronic conduction path and enhances the pressure response sensitivity.

[0024] Preferably, the co-crosslinking agent includes at least one of N-hydroxyethyl acrylamide and BIS (N,N-methylenebisacrylamide). It is used for photocuring crosslinking and synergistically enhances the mechanical strength of the hydrogel.

[0025] Preferably, the photoinitiator includes at least one of lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP), 2-hydroxy-1-(4-(2-hydroxyethoxy)phenyl)-2-methyl-1-propanone (Irgacure 2959), and 1-hydroxycyclohexyl phenyl ketone (184).

[0026] Preferably, the ionic liquid includes 1-butyl-3-methylimidazolium chloride. The ionic liquid can act synergistically with the solvent to enhance the antifreeze performance and conductivity of the hydrogel.

[0027] Preferably, the raw material components further include a solvent, and the solvent is water.

[0028] Preferably, the water is deionized water.

[0029] Preferably, the hydrogel, by weight, comprises 5-20 parts of monomer, 0.5-5 parts of ionic conductivity enhancer, 1-10 parts of electronic conductive filler, 0.01-0.1 parts of co-crosslinking agent, 0.01-0.2 parts of photoinitiator, and 15-45 parts of ionic liquid.

[0030] More preferably, the hydrogel, by weight, comprises 10-15 parts of monomer, 1-3 parts of ionic conductivity enhancer, 3-6 parts of electronic conductive filler, 0.02-0.05 parts of co-crosslinking agent, 0.02-0.1 parts of photoinitiator, and 23-37 parts of ionic liquid.

[0031] Preferably, the water, by weight, is 22.7-78.48 parts, and more preferably 50-60 parts.

[0032] The second aspect of the present invention provides a method for preparing a hydrogel with high-sensitivity tensile-pressure dual-mode response.

[0033] Specifically, a method for preparing a hydrogel with high-sensitivity tensile-pressure dual-mode response includes the following steps:

[0034] Mixing each raw material component and curing by light irradiation to obtain the hydrogel.

[0035] Preferably, the preparation method includes the following steps:

[0036] Step 1: Solution preparation

[0037] Adding the ionic conductivity enhancer into water, stirring for 2-4 hours until completely dissolved to form a transparent solution, then sequentially adding the monomer, co-crosslinking agent, and photoinitiator, stirring for 1-2 hours to form a homogeneous mixed solution, and then sequentially adding the ionic liquid and electronic conductive filler, and ultrasonically dispersing for 30-60 minutes to obtain a mixture;

[0038] Step 2: Crosslinking reaction

[0039] Pouring the mixture obtained in Step 1 into a mold and curing under ultraviolet light irradiation to obtain the hydrogel.

[0040] Preferably, the wavelength range of the ultraviolet light is between 300-400 nm.

[0041] Preferably, the intensity of the ultraviolet light irradiation is 100-500 mW / cm 2 .

[0042] The light irradiation intensity can be adjusted according to the type and content of the photoinitiator.

[0043] Ultraviolet-LED lamps can be used for curing.

[0044] After the curing is completed, the hydrogel can be taken out of the mold.

[0045] The third aspect of the present invention provides an application of a hydrogel with high-sensitivity tensile-pressure dual-mode response.

[0046] A sensing device includes the above-mentioned hydrogel with high-sensitivity tensile-pressure dual-mode response.

[0047] Preferably, the sensing device includes a robot, a wearable device or a human-computer interaction system.

[0048] The hydrogel of the present invention is designed with a dual conductive network: under the cooperation of monomers, co-crosslinking agents, photoinitiators, and ionic liquids, through the synergistic effect of an ionic conductivity enhancer (such as lithium magnesium silicate nanosheet, magnesium aluminum silicate nanosheet) and an electron conductive filler (such as graphene / carbon nanotube), an independent tensile and pressure response conductive path is constructed to achieve dual-mode high-sensitivity detection.

[0049] Synergy of mechanical enhancement and conductive enhancement: By combining the cross-linking effect of conductive substances and the cross-linking effect of chemical cross-linking agents, the hydrogel is endowed with excellent high mechanical properties (elongation at break ≥ 800%) and high conductive properties in synergy (conductivity greater than 4 S / m).

[0050] One-step preparation process: Realize dual-mode functions in a single material system, simplify the complex assembly process of traditional multi-layer heterogeneous structures, and reduce production costs.

[0051] Through the above technical solutions, the present invention solves the deficiencies of existing hydrogel materials in terms of mechanical properties, conductive properties, long-term stability and application scope, and provides a broader application prospect for fields such as flexible electronics, biomedicine and intelligent materials.

[0052] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0053] (1) Dual-mode independent response, high sensitivity:

[0054] By constructing a stable ion / electron dual conductive network, the hydrogel generates independent resistance change signals under tensile deformation (0-500%) and pressure loading (0.1-100 kPa) respectively. The tensile sensitivity (GF≥2) and pressure sensitivity (≥5 kPa -1 ) are significantly better than traditional single-response mode hydrogels (such as the pressure sensitivity of traditional single-response mode ionic conductive hydrogels <0.5 kPa -1 , and the tensile sensitivity GF of conductive filler hydrogels <1).

[0055] Solve the problem of coupling interference between tensile and pressure signals in the prior art, and achieve high-precision analysis of multi-dimensional force detection.

[0056] (2) Excellent environmental stability:

[0057] The water loss rate is reduced (weight loss ≤ 10% after 7 days of exposure at room temperature, and conductivity attenuation ≤ 20%), overcoming the problem of performance degradation of traditional hydrogels caused by water evaporation.

[0058] It can still maintain stable electrical and mechanical properties in a wide temperature range (-20°C to 60°C) and under humidity-changing environments, and is suitable for complex working conditions.

[0059] (3) Simple preparation process and low cost:

[0060] By integrating tensile and pressure response functions in a single material system through a one-step cross-linking method, the complex process of assembling multi-layer heterogeneous structures (such as piezoresistive layer + capacitive layer) is avoided, significantly reducing the production cost and process difficulty.

[0061] The material components are widely sourced, and expensive equipment is not required during the preparation process, making it suitable for large-scale production.

[0062] (4) Excellent mechanical properties and strong adaptability:

[0063] The hydrogel has both high ductility (elongation at break ≥ 800%) and soft tissue-like elastic modulus (0.1 - 1 MPa), and can withstand large deformations and high pressures without plastic deformation, being suitable for robot dynamic operation and long-term human wearable scenarios.

[0064] The synergistic effect of dynamic covalent bonds and physical cross-linking endows the material with excellent self-healing performance (repair efficiency ≥ 90%), extending the service life.

[0065] (5) Broad application prospects:

[0066] It can be widely applied in fields such as robot electronic skin, wearable health monitoring devices, and human-computer interaction systems, meeting the needs of multi-dimensional force detection.

[0067] It provides a new material solution for the miniaturization and integration of flexible sensors, promoting the further development of flexible electronic technology.

[0068] Through material design and process innovation, the present invention solves the deficiencies of existing hydrogels in dual-mode response, environmental stability, and preparation process, providing a preparation method for hydrogels with high sensitivity, high stability, and low cost, having significant technical advantages and application value. Detailed implementation manners

[0069] To make the technical solutions described in the present invention clearer and more understandable to those skilled in the art, the following examples are listed for illustration. It should be noted that the following examples do not limit the scope of protection required by the present invention.

[0070] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial channels or can be obtained by existing known methods.

[0071] For example, MXene can be provided by (Xianfeng Nano: https: / / www.xfnano.com / product / detail?goodId=1382), with the product model being nanoflake powder, and it can also be prepared into an aqueous dispersion.

[0072] Example 1

[0073] A hydrogel with high-sensitivity tensile-pressure dual-mode response, by weight, comprises the following raw material components:

[0074] Acrylamide (reactive monomer) 5 parts;

[0075] Lithium magnesium silicate nanosheet (ionic conductivity enhancer) 0.5 part;

[0076] MXene (electronic conductive filler) 1 part;

[0077] 1-Butyl-3-methylimidazolium chloride (ionic liquid) 15 parts;

[0078] N-Hydroxyethylacrylamide (co-crosslinking agent) 0.01 part;

[0079] Lithium phenyl-2,4,6-trimethylbenzoylphosphinate (photoinitiator) 0.01 part;

[0080] Deionized water 78.48 parts.

[0081] A preparation method of a hydrogel with high-sensitivity tensile-pressure dual-mode response comprises the following steps:

[0082] Solution preparation: Add lithium magnesium silicate nanosheet to deionized water, stir for 2 hours until completely dissolved to form a transparent solution, then sequentially add acrylamide, N-hydroxyethylacrylamide, and lithium phenyl-2,4,6-trimethylbenzoylphosphinate, stir for 1 hour to form a homogeneous mixed solution, then sequentially add 1-butyl-3-methylimidazolium chloride, add MXene, and ultrasonically disperse for 30 minutes to obtain a mixture.

[0083] Crosslinking reaction: Pour the mixture into a mold, and cure it with ultraviolet-LED light with a wavelength of 300 - 400 nm and a light intensity of 100 mW / cm 2 for 5 minutes, and take out the hydrogel from the mold to obtain the final dual-mode response hydrogel.

[0084] Example 2

[0085] A hydrogel with high-sensitivity tensile-pressure dual-mode response, by weight, comprises the following raw material components:

[0086] 20 parts of acrylamide (reactive monomer);

[0087] 5 parts of lithium magnesium silicate nanosheets (ionic conductivity enhancer);

[0088] 10 parts of graphene (electronic conductive filler);

[0089] 45 parts of 1-butyl-3-methylimidazolium chloride (ionic liquid);

[0090] 0.1 part of N,N'-methylenebisacrylamide (co-crosslinker);

[0091] 0.2 part of 2-hydroxy-1-(4-(2-hydroxyethoxy)phenyl)-2-methyl-1-propanone (photoinitiator);

[0092] 22.7 parts of deionized water.

[0093] A preparation method of a hydrogel with high-sensitivity tensile-pressure dual-mode response, comprising the following steps:

[0094] Solution preparation: Add lithium magnesium silicate nanosheets into deionized water, stir for 4 hours until completely dissolved to form a transparent solution, then successively add acrylamide, N,N'-methylenebisacrylamide, and 2-hydroxy-1-(4-(2-hydroxyethoxy)phenyl)-2-methyl-1-propanone, stir for 2 hours to form a homogeneous mixed solution, then successively add 1-butyl-3-methylimidazolium chloride and graphene, and ultrasonically disperse for 60 minutes to obtain a mixture;

[0095] Crosslinking reaction: Pour the mixture into a mold, and cure it with ultraviolet-LED light with a wavelength of 300 - 400 nm and a light intensity of 500 mW / cm 2 for 10 minutes, and take out the hydrogel from the mold to obtain the final dual-mode response hydrogel.

[0096] Example 3

[0097] A hydrogel with high-sensitivity tensile-pressure dual-mode response, by weight, comprises the following raw material components:

[0098] 15 parts of acrylamide (reactive monomer);

[0099] 3 parts of lithium magnesium silicate nanosheets (ionic conductivity enhancer);

[0100] 6 parts of molybdenum disulfide (electronic conductive filler);

[0101] 40 parts of 1-butyl-3-methylimidazolium chloride (ionic liquid);

[0102] N-Hydroxyethyl acrylamide (co-crosslinking agent) 0.05 parts;

[0103] 1-Hydroxycyclohexyl phenyl ketone (photoinitiator) 0.1 parts;

[0104] Deionized water 50 parts.

[0105] A preparation method of a hydrogel with high-sensitivity tensile-pressure dual-mode response, comprising the following steps:

[0106] Solution preparation: Add lithium magnesium silicate nanosheets to deionized water and stir for 3 hours until completely dissolved to form a transparent solution. Then, sequentially add acrylamide, N-hydroxyethyl acrylamide, and 1-hydroxycyclohexyl phenyl ketone, and stir for 1.5 hours to form a homogeneous mixed solution. Then, sequentially add 1-butyl-3-methylimidazolium chloride and molybdenum disulfide, and ultrasonically disperse for 45 minutes to obtain a mixture;

[0107] Crosslinking reaction: Pour the mixture into a mold and irradiate it with ultraviolet-LED light with a wavelength of 300-400 nm and a light intensity of 300 mW / cm 2 for 30 minutes to cure. Take out the hydrogel from the mold to obtain the final dual-mode response hydrogel.

[0108] Example 4

[0109] A hydrogel with high-sensitivity tensile-pressure dual-mode response, by weight, comprising the following raw material components:

[0110] Acrylamide (reactive monomer) 12 parts;

[0111] Lithium magnesium aluminum silicate nanosheets (ionic conductivity enhancer) 2 parts;

[0112] Graphene oxide (electronic conductive filler) 4 parts;

[0113] 1-Butyl-3-methylimidazolium chloride (ionic liquid) 20 parts;

[0114] N,N-Methylenebisacrylamide (co-crosslinking agent) 0.03 parts;

[0115] Phenyl-2,4,6-trimethylbenzoylphosphinic acid lithium salt (photoinitiator) 0.05 parts;

[0116] Deionized water 50.92 parts.

[0117] A preparation method of a hydrogel with high-sensitivity tensile-pressure dual-mode response, comprising the following steps:

[0118] Solution preparation: Add nano - magnesium aluminum silicate into deionized water and stir for 2.5 hours until it is completely dissolved to form a transparent solution. Then, add acrylamide, N,N - methylenebisacrylamide, and lithium phenyl - 2,4,6 - trimethylbenzoylphosphinate in sequence, and stir for 1.2 hours to form a homogeneous mixed solution. Next, add 1 - butyl - 3 - methylimidazolium chloride and graphene oxide in sequence, and ultrasonically disperse for 35 minutes to obtain a mixture;

[0119] Cross - linking reaction: Pour the mixture into a mold and irradiate it with ultraviolet - LED light with a wavelength of 300 - 400 nm and a light intensity of 200 mW / cm 2 for 60 minutes to cure it. Take out the hydrogel from the mold to obtain the final dual - mode responsive hydrogel.

[0120] Comparative example 1

[0121] A hydrogel contains the following raw material components by weight:

[0122] Acrylamide (monomer) 15 parts;

[0123] Deionized water 84.94 parts;

[0124] N - hydroxyethyl acrylamide (co - crosslinking agent) 0.05 parts;

[0125] 1 - hydroxycyclohexyl phenyl ketone (photo - initiator) 0.01 parts.

[0126] The preparation method is as follows:

[0127] Solution preparation: Add N - hydroxyethyl acrylamide and 1 - hydroxycyclohexyl phenyl ketone into deionized water and stir for 3 hours until they are completely dissolved. Then add acrylamide and continue to stir for 1.5 hours to obtain a homogeneous mixed solution.

[0128] Cross - linking reaction: Pour the mixed solution into a mold and cure it under ultraviolet - LED light with a wavelength of 300 - 400 nm and a light intensity of 300 mW / cm 2 for 30 minutes, and then take out the hydrogel from the mold.

[0129] This hydrogel is basically non - conductive, and its conductivity is only 0.05 S / m. Because no conductive components and mechanical reinforcing agents are added, its mechanical strength is poor, the elongation at break is only 20%, and the elastic modulus is only 0.05 MPa. At the same time, without adding ionic liquid, its environmental stability is poor, and after being exposed at room temperature for 7 days, the weight loss is as high as 83%. The tensile sensitivity (GF) is 0.1, and the pressure sensitivity is 1 kPa -1 .

[0130] Comparative example 2

[0131] A hydrogel, comprising the following raw material components by weight:

[0132] Acrylamide (monomer) 15 parts;

[0133] 3 parts of nano-lithium magnesium silicate (ion conductivity enhancer);

[0134] 81.94 parts of deionized water;

[0135] N-hydroxyethyl acrylamide (co-crosslinking agent) 0.05 parts;

[0136] 1-Hydroxycyclohexylphenyl ketone (photoinitiator) 0.01 parts.

[0137] The preparation method is as follows:

[0138] Solution preparation: Add nano-lithium magnesium silicate into deionized water and stir for 3 hours to completely dissolve it to form a transparent solution. Then add N-hydroxyethyl acrylamide and 1-hydroxycyclohexyl phenyl ketone and stir for 1.5 hours. Then add acrylamide and continue to stir evenly to obtain a mixed solution.

[0139] Cross-linking reaction: Pour the mixed solution into the mold and cure it under UV-LED light with a wavelength of 300-400nm and a light intensity of 300mW / cm– for 30 minutes, and finally remove the hydrogel from the mold.

[0140] Compared with Comparative Example 1, Comparative Example 2 adds nano-lithium magnesium silicate as a mechanical enhancer. The conductivity is slightly improved, and the conductivity reaches 0.45S / m. The mechanical strength is enhanced, the elongation at break is increased to 750%, and the elastic modulus is 0.2MPa. However, due to the lack of ionic liquid, the environmental stability is still poor, and the weight loss is 79% after exposure to room temperature for 7 days. The tensile sensitivity (GF) is increased to 1, and the pressure sensitivity is 2kPa -1 .

[0141] Comparative Example 3

[0142] A hydrogel, comprising the following raw material components by weight:

[0143] Acrylamide (monomer) 15 parts;

[0144] 3 parts of nano-lithium magnesium silicate (ion conductivity enhancer);

[0145] 1-Butyl-3-methylimidazolium chloride (ionic liquid) 40 parts;

[0146] N-hydroxyethyl acrylamide (co-crosslinking agent) 0.05 parts;

[0147] 1-Hydroxycyclohexylphenyl ketone (photoinitiator) 0.01 part;

[0148] 41.94 parts of deionized water.

[0149] The preparation method is as follows:

[0150] Solution preparation: First, add lithium magnesium silicate nanosheets to deionized water and stir for 3 hours until completely dissolved to form a transparent solution. Then add N - hydroxyethyl acrylamide and 1 - hydroxycyclohexyl phenyl ketone, stir for 1.5 hours, then add acrylamide and stir evenly. Next, add 1 - butyl - 3 - methylimidazolium chloride and continue to stir evenly to obtain a mixed solution.

[0151] Cross - linking reaction: Pour the mixed solution into a mold and cure it under ultraviolet - LED light with a wavelength of 300 - 400 nm and a light intensity of 300 mW / cm² for 30 minutes. Then take out the hydrogel from the mold.

[0152] After adding the ionic liquid, the conductivity of the hydrogel becomes better, and the conductivity is 4.8 S / m. In Comparative Example 3, no electron - conductive filler was added, but the conductivity (4.8 S / m) was still relatively high because the ionic liquid dominated the conductivity. The tensile sensitivity is relatively high, and the tensile sensitivity (GF) is 3. The mechanical strength is good, the elongation at break is 880%, and the elastic modulus is 0.7 MPa. The environmental stability is good. After being exposed at room temperature for 7 days, the weight loss is 7%. However, due to the lack of electron - conductive filler, the compression sensitivity is not high, and the pressure sensitivity is 3 kPa - 1.

[0153] Comparative Example 4

[0154] A hydrogel, by weight, contains the following raw material components:

[0155] 15 parts of acrylamide (monomer);

[0156] 3 parts of lithium magnesium silicate nanosheets (ionic - conductivity enhancer);

[0157] 6 parts of molybdenum disulfide (electron - conductive filler);

[0158] 0.05 part of N - hydroxyethyl acrylamide (co - crosslinking agent);

[0159] 0.01 part of 1 - hydroxycyclohexyl phenyl ketone (photo - initiator);

[0160] 75.94 parts of deionized water.

[0161] The preparation method is as follows:

[0162] Solution preparation: Add lithium magnesium silicate nanosheets into deionized water, stir for 3 hours to completely dissolve them to form a transparent solution. Then add N-hydroxyethyl acrylamide and 1-hydroxycyclohexyl phenyl ketone, stir for 1.5 hours, add acrylamide and stir evenly. Finally, add molybdenum disulfide and disperse it by ultrasonic for 45 minutes to obtain a mixed solution.

[0163] Crosslinking reaction: Pour the mixed solution into a mold, and cure it under ultraviolet-LED light with a wavelength of 300 - 400 nm and a light intensity of 300 mW / cm² for 30 minutes. Then take out the hydrogel from the mold.

[0164] After adding the electron-conductive filler molybdenum disulfide, the hydrogel has good conductivity, and the conductivity is 1.8 S / m. The tensile sensitivity is not high, and the tensile sensitivity (GF) is 2. The mechanical strength is good, the elongation at break is 350%, and the elastic modulus is 0.75 MPa. The electron-conductive filler results in a significantly lower elongation at break compared to Comparative Example 3, indicating that the electron-conductive filler affects the mechanical properties of the gel. However, lithium magnesium silicate can better disperse the electron-conductive filler, making it evenly dispersed and suspended in the system. Because no ionic liquid is added, the environmental stability is not good. After being exposed at room temperature for 7 days, the weight loss is 73%. The compression sensitivity is high, and the pressure sensitivity is 10 kPa. -1 。

[0165] Product effect test

[0166] Take the hydrogels prepared in the above examples and comparative examples, and use an impedance analyzer such as the Agilent 4294A precision impedance analyzer to test the conductivity of the hydrogel samples.

[0167] The tensile sensitivity is tested using an electronic universal testing machine. The specimen is stretched, and the resistance change and the corresponding tensile strain during the stretching process of the specimen are recorded. The tensile sensitivity (GF) is calculated by the formula GF = (ΔR / R0) / ∈, where ΔR is the resistance change, R0 is the initial resistance, and ∈ is the tensile strain.

[0168] The pressure sensitivity test is carried out using an electronic universal testing machine. Pressure is applied to the specimen, and the resistance change of the sample during the pressure change process is recorded. The pressure sensitivity is calculated by the formula S = (ΔR / R0) / ΔP, where ΔR is the resistance change, R0 is the initial resistance, and ΔP is the pressure change, with the unit of kPa.

[0169] The environmental stability of the hydrogel is measured by measuring the weight loss rate. At room temperature for 30 days, its weight loss is tested to measure its environmental stability.

[0170] The elongation at break and elastic modulus were tested using an electronic universal testing machine. The elongation at break was calculated by the formula (L - L0) * 100% / L0, where L is the specimen length at break and L0 is the initial gauge length of the specimen. The elastic modulus was calculated from the slope of the linear part of the tensile stress-strain curve, and the unit is MPa.

[0171] The above performance test results are shown in Table 1.

[0172] Table 1

[0173]

[0174]

[0175] As can be seen from Table 1, the tensile sensitivity, pressure sensitivity, environmental stability, elongation at break, and elastic modulus of the hydrogels prepared in the examples are all better than those of the comparative examples. It can also be seen from this that the hydrogels of the present invention have selectivity for the types of raw materials, and the combined use of specific raw material components can enable the hydrogels to simultaneously have good tensile sensitivity, pressure sensitivity, environmental stability, and mechanical properties.

Claims

1. A hydrogel, characterized in that, The raw material components include monomers, ionic conductivity enhancers, electronic conductivity fillers, co-crosslinking agents, photoinitiators, and ionic liquids.

2. The hydrogel according to claim 1, wherein The monomers include at least one of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and its salts, acrylic acid and its salts.

3. The hydrogel according to claim 1, characterized in that, The ionic conductivity enhancers include at least one of lithium magnesium silicate nanosheets, montmorillonite, and lithium magnesium aluminum silicate nanosheets.

4. The hydrogel according to claim 1, characterized in that, The electronic conductivity fillers include at least one of MXene, molybdenum disulfide, carbon nanotubes, graphene, or graphene oxide; and / or, the co-crosslinking agents include at least one of N-hydroxyethylacrylamide and N,N-methylenebisacrylamide.

5. The hydrogel according to claim 1, wherein, The photoinitiators include at least one of lithium phenyl-2,4,6-trimethylbenzoylphosphinate, 2-hydroxy-1-(4-(2-hydroxyethoxy)phenyl)-2-methyl-1-propanone, and 1-hydroxycyclohexyl phenyl ketone; and / or, the ionic liquids include 1-butyl-3-methylimidazolium chloride.

6. The hydrogel according to any one of claims 1-5, characterized in that, The raw material components further include a solvent.

7. The hydrogel according to any one of claims 1-5, characterized in that, For the hydrogel, by weight, the raw material components include 5-20 parts of monomers, 0.5-5 parts of ionic conductivity enhancers, 1-10 parts of electronic conductivity fillers, 0.01-0.1 parts of co-crosslinking agents, 0.01-0.2 parts of photoinitiators, and 15-45 parts of ionic liquids.

8. The hydrogel according to claim 7, wherein The raw material components further include a solvent, the solvent includes water, and the water is 22.7-78.48 parts by weight.

9. The preparation method of the hydrogel according to any one of claims 1-8, characterized in that, It includes the following steps: Mix all the raw material components and cure them by light irradiation to obtain the hydrogel.

10. A sensing device, characterized in that, It includes the hydrogel according to any one of claims 1-8.

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