Fe3 +-EDTA dynamic coordination compound-based gradient sensitivity hydrogel as well as preparation method and application thereof
A three-dimensional network hydrogel constructed using Fe3+-EDTA dynamic coordination compounds enables the stability of strain sensors in the low strain range and the sensitivity switching in the high strain range, solving the problem of signal mixing in complex scenarios. This technology is suitable for robot joint protection, rehabilitation motion monitoring, and structural health early warning.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-07
- Publication Date
- 2026-03-31
AI Technical Summary
The high sensitivity of existing flexible strain sensors across the entire strain range leads to a mixture of small and large strain signals, making it difficult to effectively distinguish and respond to them in complex scenarios, thus affecting the accuracy and reliability of the signals.
By constructing a three-dimensional interpenetrating network with Fe3+-EDTA dynamic coordination compounds as the core, the hydrogel achieves low sensitivity in the 0-100% strain range, and a stepwise increase in sensitivity after exceeding 100% strain. Combined with the physical cross-linking of polyvinyl alcohol and the lignin-reinforced ion network, a unique gradient sensitivity sensing mode is formed.
It shields minor interference in the low strain range and outputs a stable signal, while switching to high-sensitivity sensing in the high strain range. This solves the contradiction between high stability and high sensitivity over a wide strain range and is suitable for accurate signal capture in complex strain scenarios.
Smart Images
Figure CN121758883A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a Fe-based 3+ - Gradient sensitivity hydrogels of EDTA dynamic coordination compounds, their preparation methods and applications, belong to the field of flexible sensor technology. Background Technology
[0002] Flexible strain sensors are core components in cutting-edge fields such as wearable electronic devices, health monitoring, soft robotics, and artificial electronic skin. Among them, conductive hydrogels are considered ideal materials for fabricating next-generation flexible sensors due to their excellent flexibility, tensile strength, biocompatibility, and tunable conductivity. The core indicator of the strain sensing performance of conductive hydrogels is their sensitivity, usually measured by the strain factor (GF). The higher the GF value, the more sensitive the material is to strain.
[0003] However, existing high-performance hydrogel sensors generally exhibit high GF values across the entire strain range. This leads to a critical issue: when the sensor is placed in a complex environment with both minute environmental strains (such as human tremors or environmental vibrations) and large target strains (such as joint bending or structural deformation), its inherent high sensitivity will simultaneously respond to all strains. Therefore, minute, often noisy, strain signals will be mixed with and superimposed on the crucial large strain signals, severely interfering with the accuracy and reliability of the latter's extraction. In other words, when monitoring large strains, the sensor is essentially subjected to interference from small strains that cannot be effectively filtered out. For example, the PVA-based hydrogel synthesized by Wu et al. (Chemical Engineering Journal, 2024, 480: 148228) has a GF value as high as 2.15–32.95. The PVA-based hydrogel synthesized by Sun et al. (Chemical Engineering Journal, 2024, 482: 148863) also has a GF value of 0.9–1.53. While improving material sensitivity can enhance signal response, such strategies still cannot shield sensors from minute signal disturbances in complex strain fields.
[0004] Therefore, existing technologies lack a hydrogel material capable of intelligently distinguishing strain scales and implementing differentiated response strategies. To address these issues, this invention proposes an innovative solution: precisely constructing a hydrogel material with Fe... 3+ A three-dimensional interpenetrating network with EDTA dynamic coordination compounds at its core enables intelligent programming of the hydrogel's responsive behavior. Among them, Fe... 3+-EDTA coordination chelates possess both positive and negative charges, a characteristic that allows them to simultaneously act as both "ionic conductive pathways" and "dynamic cross-linking points" within the gel network. In the low strain range of 0-100%, minute deformations have minimal impact on the conductive pathways dominated by this bifunctional chelate. Therefore, the hydrogel's GF value is as low as 0.17 in this stage, providing a reliable electrical signal substrate for the system. When the strain exceeds the critical point (>100%), the hydrogel structure undergoes large-scale reconstruction, and the GF value increases dramatically (up to a maximum of 7.5), rapidly switching the material to a high-sensitivity sensing mode. This achieves a mode shift from passive high sensitivity to active programmable response in hydrogels, resolving the inherent contradiction between stability and sensitivity in wide-strain sensing, and providing a novel material platform for complex scenarios requiring the differentiation between minute disturbances and effective deformation (such as joint protection against accidental touch and high-precision rehabilitation motion monitoring). Summary of the Invention
[0005] This invention aims to overcome the technical shortcomings of existing flexible strain sensors that cannot simultaneously achieve signal stability and high sensitivity over a wide strain range, and provides a Fe-based... 3+ - A gradient-sensitivity hydrogel with dynamic coordination of EDTA compounds. Through its unique structural design, this hydrogel achieves intelligent switching of sensing response modes, effectively shielding against minute disturbances in complex strain fields and accurately capturing large strains.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: a Fe-based 3+ - The gradient-sensitivity hydrogel of EDTA dynamic coordination compound has a three-dimensional network structure formed by the interweaving of a polyvinyl alcohol physical cross-linking network, a dynamic metal coordination network, and a lignin-reinforced ionic network.
[0007] The above-mentioned Fe-based 3+ - A method for preparing gradient sensitivity hydrogels of EDTA dynamic coordination compounds includes the following steps: dissolving chelating agents, metal ions, and polyvinyl alcohol in ethylene glycol / water solution to prepare solution A; dissolving lignin in aromatic eutectic solvent to prepare solution B; uniformly mixing solution A and solution B for reaction; thoroughly stirring, defoaming, and injecting into a mold; and then sequentially undergoing low-temperature aging, freezing, and drying treatments to obtain the hydrogel.
[0008] The above-mentioned Fe-based 3+ - A method for preparing gradient-sensitive hydrogels of EDTA dynamic coordination compounds, wherein the chelating agent is an organic compound or its salt containing a polydentate coordination group, and the chelating agent is selected from one or more of ethylenediaminetetraacetic acid, its sodium salt or citrate.
[0009] The above-mentioned Fe-based 3+A method for preparing gradient-sensitivity hydrogels of EDTA dynamic coordination compounds, wherein the metal ion is a multivalent metal ion capable of forming dynamic coordination bonds with the chelating agent, and the multivalent metal ion is selected from Fe. 3+ Al 3+ Cu 3+ Ca 3+ Mg 3+ Li + or K + One or more of them.
[0010] The above-mentioned Fe-based 3+ A method for preparing gradient-sensitivity hydrogels of EDTA dynamic coordination compounds, wherein the polyvinyl alcohol is a water-soluble polymer capable of forming a physical cross-linked network.
[0011] The above-mentioned Fe-based 3+ - A method for preparing gradient-sensitive hydrogels of EDTA dynamic coordination compounds, wherein the aromatic eutectic solvent is composed of a quaternary ammonium salt as a hydrogen bond acceptor and an organic acid as a hydrogen bond donor, wherein the quaternary ammonium salt is selected from one or more of benzyltrimethylammonium chloride, benzyltrimethylammonium bromide or benzyltrimethylammonium iodide; and the organic acid is lactic acid.
[0012] The above-mentioned Fe-based 3+ - A method for preparing gradient-sensitivity hydrogels of EDTA dynamic coordination compounds, wherein the feeding ratio of each main component satisfies one or more of the following conditions:
[0013] 1) The mass-to-volume ratio of lignin to aromatic eutectic solvent is 0-0.2 g / mL;
[0014] 2) The molar ratio of quaternary ammonium salt to organic acid is 0.5-2:1-3;
[0015] 3) The molar concentration of the chelate formed by the chelating agent and the metal ion is 0-1.5 mol / L;
[0016] 4) In the ethylene glycol / water solution, the molar ratio of ethylene glycol to water is 1-5:1-10.
[0017] 5) The reaction temperature is controlled at 60-120℃.
[0018] The gradient sensitivity hydrogel described above is characterized in that the low-temperature aging conditions are: standing at 2-8 ℃ for 2-6 h; and the freezing conditions are: freezing at -15 ℃ to -25 ℃ for 12-24 h.
[0019] A flexible strain sensor, the sensing element of which is made of the aforementioned gradient sensitivity hydrogel.
[0020] Application of a gradient-sensitivity hydrogel or a flexible strain sensor as described above in the fabrication of devices for robot joint limit protection, rehabilitation motion monitoring, or structural health early warning.
[0021] The significant feature of the gradient-sensitivity hydrogel described in this invention lies in its strain response behavior: in the low strain range of 0-100%, its strain coefficient (GF) is designed to be extremely low (no greater than 0.2), giving the material highly stable electrical conductivity, effectively resisting interference from minute strains and environmental noise, and outputting a stable reference electrical signal; when the strain exceeds 100% and enters the medium-high strain range, its GF value increases significantly in a stepwise manner with increasing strain (up to 7.5), allowing the material to quickly switch to a high-sensitivity strain sensing mode. Simultaneously, the hydrogel has a high electrical conductivity (4.19 S / m), ensuring high signal-to-noise ratio transmission of the sensing signal. This unique dual-mode characteristic of "stable reference + sensitive response" solves the inherent contradiction between high sensitivity and high stability in wide-strain sensing, making it particularly suitable for complex scenarios that require simultaneously ignoring minute interferences while accurately capturing large movements.
[0022] Based on the above characteristics, this invention further provides the application of the gradient sensitivity hydrogel in the fabrication of flexible strain sensors. The sensor is particularly suitable for scenarios requiring selective sensing under complex strain conditions, such as anti-accidental contact protection for robot joints, monitoring devices for accurately identifying large-amplitude rehabilitation movements against the backdrop of everyday micro-movements in the human body, and engineering safety early warning systems for distinguishing between structural thermal expansion and contraction and actual crack propagation.
[0023] Compared with the prior art, the beneficial effects of the present invention include:
[0024] 1. Intelligent switching of response modes has been achieved: Breaking through the traditional design approach of pursuing a single high sensitivity across the entire strain range, the device is creatively designed with material structure to enable it to have two intelligently switchable working modes: "stable conductivity under low strain" and "sensitive sensing under high strain".
[0025] 2. Resolves the fundamental contradiction in wide-strain monitoring: It fundamentally solves the technical challenge of the incompatibility between high stability and high sensitivity within an ultra-wide strain range of 0-400%. The inherent high stability of the material in the low-strain region provides a pure signal substrate for the system, ensuring the accuracy and reliability of signal extraction in the high-strain region.
[0026] 3. Expanded high-level application scenarios: It provides a brand-new and irreplaceable key material solution for fields that require "signal filtering" capabilities, such as precise robot control, high-end health monitoring, and safety early warning of major infrastructure.
[0027] 4. Green and controllable preparation method: Lignin is treated with a low eutectic solvent, which is environmentally friendly. It is formed by physical cross-linking methods such as freeze-thaw, which is mild, has a controllable structure, and is easy to prepare on a large scale. Attached Figure Description
[0028] Figure 1 SEM image of the strain response gradient sensitivity hydrogel prepared in Example 4.
[0029] Figure 2 The GF values of the strain response gradient sensitivity hydrogel prepared in Example 4 under different strain conditions. Detailed Implementation
[0030] Example 1
[0031] Solution A was prepared by dissolving 0.75 g of polyvinyl alcohol in 4.5 mL of a ethylene glycol-water mixture (molar ratio 1:4) at 95 °C. Solution B was prepared by dissolving 0.075 g of alkali lignin in 1.25 mL of DESs (benzyltrimethylammonium chloride and lactic acid mixed uniformly in a 1:2 molar ratio) at 60 °C. Solutions A and B were mixed thoroughly at 80 °C and poured into a polytetrafluoroethylene mold. The mixture was then aged at 4 °C for 6 h, frozen at -20 °C for 12 h, and dried for 2 h to obtain a hydrogel. Electrochemical testing showed that its conductivity was 0.435 S / m.
[0032] Example 2
[0033] Solution A was prepared by dissolving 0.75 g of polyvinyl alcohol, 0.4 mol of FeCl3, and 0.4 mol of disodium ethylenediaminetetraacetate at 95 °C in 4.5 mL of ethylene glycol-water (molar ratio 1:4). Solution B was prepared by dissolving 0.075 g of alkali lignin at 60 °C in 1.25 mL of DESs (benzyltrimethylammonium chloride and lactic acid mixed uniformly at a molar ratio of 1:2). Solutions A and B were mixed thoroughly at 80 °C and poured into a polytetrafluoroethylene mold. The mixture was then aged at 4 °C for 6 h, frozen at -20 °C for 12 h, and dried for 2 h to obtain a hydrogel. Electrochemical testing showed that its conductivity was 2.25 S / m.
[0034] Example 3
[0035] Solution A was prepared by dissolving 0.75 g of polyvinyl alcohol, 0.4 mol of FeCl3, and 0.4 mol of disodium ethylenediaminetetraacetate at 95 °C in 4.5 mL of ethylene glycol-water (molar ratio 1:2). Solution B was prepared by dissolving 0.075 g of alkali lignin at 60 °C in 1.25 mL of DESs (benzyltrimethylammonium chloride and lactic acid mixed uniformly at a molar ratio of 1:2). Solutions A and B were mixed thoroughly at 80 °C and poured into a polytetrafluoroethylene mold. The mixture was then aged at 4 °C for 6 h, frozen at -20 °C for 12 h, and dried for 2 h to obtain a hydrogel. Electrochemical testing showed that its conductivity was 0.19 S / m.
[0036] Example 4
[0037] Solution A was prepared by dissolving 0.75 g of polyvinyl alcohol, 0.4 mol of FeCl3, and 0.4 mol of disodium ethylenediaminetetraacetate at 95 °C in 4.5 mL of a ethylene glycol-water mixture (molar ratio 1:8). Solution B was prepared by dissolving 0.075 g of alkali lignin at 60 °C in 1.25 mL of DESs (a homogeneous mixture of benzyltrimethylammonium chloride and lactic acid at a molar ratio of 1:2). Solutions A and B were mixed thoroughly at 80 °C and poured into a polytetrafluoroethylene mold. The mixture was then aged at 4 °C for 6 h, frozen at -20 °C for 12 h, and dried for 2 h to obtain a hydrogel. Scanning electron microscopy images are shown below. Figure 1 As shown, electrochemical tests indicate that its conductivity is 4.19 S / m. Mechanical tests show that its elongation at break can reach 401%, its tensile strength can reach 832 kPa, and its toughness is 1.46 MJ / m. 3 Electrochemical tests showed that its GF value was 0.17 at 0–100% strain, 1.31 at 100%–250% strain, 4.8 at 250%–370% strain, and 7.5 at 370%–401% strain. Figure 2 As shown.
[0038] Example 5
[0039] Solution A was prepared by dissolving 1 g of polyvinyl alcohol, 0.4 mol of FeCl3, and 0.4 mol of disodium ethylenediaminetetraacetate at 95 °C in 4.5 mL of ethylene glycol-water (molar ratio 1:8). Solution B was prepared by dissolving 0.075 g of alkali lignin at 60 °C in 1.25 mL of DESs (benzyltrimethylammonium chloride and lactic acid mixed uniformly at a molar ratio of 1:2). Solutions A and B were mixed thoroughly at 80 °C and poured into a polytetrafluoroethylene mold. The mixture was then aged at 4 °C for 6 h, frozen at -20 °C for 12 h, and dried for 2 h to obtain a hydrogel. Electrochemical testing showed that its conductivity was 2.38 S / m.
[0040] Example 6
[0041] Solution A was prepared by dissolving 0.75 g of polyvinyl alcohol, 0.4 mol of FeCl3, and 0.4 mol of disodium ethylenediaminetetraacetate at 95 °C in 4.5 mL of a ethylene glycol-water mixture (molar ratio 1:2). Solution B was prepared by uniformly mixing 1.25 mL of DESs (benzyltrimethylammonium chloride and lactic acid at a molar ratio of 1:2). Solutions A and B were mixed thoroughly at 80 °C and poured into a polytetrafluoroethylene mold. The mixture was then aged at 4 °C for 6 h, frozen at -20 °C for 12 h, and dried for 2 h to obtain a hydrogel. Electrochemical testing showed that its conductivity was 1.96 S / m.
[0042] Example 7
[0043] Solution A was prepared by dissolving 0.75 g of polyvinyl alcohol and 0.8 mol of FeCl3 in 4.5 mL of ethylene glycol-water (molar ratio 1:8) at 95 °C. Solution B was prepared by dissolving 0.075 g of alkali lignin in 1.25 mL of DESs (benzyltrimethylammonium chloride and lactic acid mixed uniformly in a 1:2 molar ratio) at 60 °C. Solutions A and B were mixed thoroughly at 80 °C and poured into a polytetrafluoroethylene mold. The mixture was then aged at 4 °C for 6 h, frozen at -20 °C for 12 h, and dried for 2 h to obtain a hydrogel. Electrochemical testing showed that its conductivity was 0.29 S / m.
[0044] Example 8
[0045] Solution A was prepared by dissolving 1 g of polyvinyl alcohol, 0.4 mol of LiCl, and 0.4 mol of disodium ethylenediaminetetraacetate at 95 °C in 4.5 mL of a ethylene glycol-water mixture (molar ratio 1:8). Solution B was prepared by dissolving 0.075 g of alkali lignin at 60 °C in 1.25 mL of DESs (a homogeneous mixture of benzyltrimethylammonium chloride and lactic acid at a molar ratio of 1:2). Solutions A and B were mixed thoroughly at 80 °C and poured into a polytetrafluoroethylene mold. The mixture was then aged at 4 °C for 6 h, frozen at -20 °C for 12 h, and dried for 2 h to obtain a hydrogel. Electrochemical testing showed that its conductivity was 0.79 S / m.
[0046] Example 9
[0047] Solution A was prepared by dissolving 0.75 g of polyvinyl alcohol, 0.4 mol of FeCl3, and 0.4 mol of disodium ethylenediaminetetraacetate at 95 °C in 4.5 mL of ethylene glycol-water (molar ratio 1:8). Solution B was prepared by dissolving 0.1 g of alkali lignin at 60 °C in 1.25 mL of DESs (benzyltrimethylammonium chloride and lactic acid mixed uniformly at a molar ratio of 1:2). Solutions A and B were mixed thoroughly at 80 °C and poured into a polytetrafluoroethylene mold. The mixture was then aged at 4 °C for 3 h, frozen at -20 °C for 15 h, and dried for 2 h to obtain a hydrogel. Electrochemical testing showed that its conductivity was 2.03 S / m.
[0048] Example 10
[0049] Solution A was prepared by dissolving 0.75 g of polyvinyl alcohol, 0.1 mol of FeCl3, and 0.1 mol of disodium ethylenediaminetetraacetate at 95 °C in 4.5 mL of a ethylene glycol-water mixture (molar ratio 1:8). Solution B was prepared by dissolving 0.075 g of alkali lignin at 60 °C in 1.25 mL of DESs (benzyltrimethylammonium chloride and lactic acid mixed uniformly at a molar ratio of 1:2). Solutions A and B were mixed thoroughly at 80 °C and poured into a polytetrafluoroethylene mold. The mixture was then aged at 4 °C for 3 h, frozen at -20 °C for 15 h, and dried for 2 h to obtain a hydrogel. Electrochemical testing showed that its conductivity was 0.76 S / m.
[0050] In summary, Fe 3+ The introduction of EDTA dynamic coordination compounds resulted in a hydrogel conductivity of up to 4.19 S / m, significantly higher than that achieved using FeCl3 or other alkali metal ion systems alone. This result confirms that Fe... 3+- EDTA dynamic coordination compounds can efficiently promote the construction of conductive pathways within the hydrogel, thereby significantly improving its intrinsic conductivity. This lays a crucial material foundation for achieving high signal-to-noise ratio transmission of sensing signals. Simultaneously, the hydrogel exhibits excellent mechanical properties, with an elongation at break of 401% and a tensile strength of 832 kPa, indicating that the material possesses good flexibility and mechanical strength, capable of adapting to the large deformation requirements of practical applications.
[0051] Most importantly, this hydrogel achieves an intelligent gradient response, transitioning from "low strain stability" to "high strain sensitivity." In the low strain range of 0-100%, its extremely low GF value (0.17) effectively shields the material from interference from minute background strains and environmental noise, providing a highly stable electrical signal reference for the system output. When the strain exceeds 100%, its GF value exhibits a stepwise increase (reaching a maximum of 7.5), indicating that the material can quickly switch to a high-sensitivity mode, enabling precise and sensitive capture of large-amplitude movements.
[0052] The above results fully demonstrate that the hydrogel provided by this invention successfully integrates high electrical conductivity, excellent mechanical properties, and intelligent gradient strain response characteristics into a single material system, making it particularly suitable for high-end flexible sensing applications that require "signal filtering" functions in complex strain fields.
[0053] The above is an exemplary description of the present invention. Without departing from the core of the present invention, any simple modifications, alterations, substitutions, combinations, or simplifications are equivalent replacements and are included within the protection scope of the present invention.
Claims
1. A gradient-sensitivity hydrogel based on Fe 3+ -EDTA dynamic coordination compounds, characterized in that, The gradient sensitivity hydrogel has a three-dimensional network structure interpenetrated by a polyvinyl alcohol physical crosslinking network, a dynamic metal coordination network and a lignin enhanced ionic network.
2. A Fe-based alloy as claimed in claim 1. 3+ Process for the preparation of a gradient-sensitivity hydrogel of dynamic coordination compounds of EDTA, characterized in that, The preparation method comprises the following steps: dissolving a chelating agent, metal ions and polyvinyl alcohol in a glycol / water solution to prepare solution A, dissolving lignin in an aromatic eutectic solvent to prepare solution B, uniformly mixing solution A and solution B to react, fully stirring, defoaming and pouring into a mold, and then sequentially performing low-temperature aging, freezing and drying treatment to obtain the hydrogel.
3. A Fe-based alloy according to claim 2, wherein the alloy contains 0.1 to 0.5% of C. 3+ A method for preparing a gradient-sensitivity hydrogel of an EDTA dynamic coordination compound, characterized by, The chelating agent is an organic compound or salt thereof containing a polydentate coordination group, and the chelating agent is selected from one or more of ethylenediaminetetraacetic acid, a sodium salt or a citrate salt thereof.
4. A Fe-based alloy according to claim 2, wherein the alloy contains 0.1 to 0.5% of C. 3+ A method for preparing a gradient-sensitivity hydrogel of an EDTA dynamic coordination compound, characterized by, The metal ion is a polyvalent metal ion capable of forming a dynamic coordination bond with the chelating agent, the polyvalent metal ion being selected from one or more of Fe 3+ , Al 3+ , Cu 3+ , Ca 3+ , Mg 3+ , Li + or K + .
5. A Fe-based alloy according to claim 2, wherein the alloy contains 0.1 to 0.5% of C. 3+ A method for preparing a gradient-sensitivity hydrogel of an EDTA dynamic coordination compound, characterized by, The polyvinyl alcohol is a water-soluble polymer capable of forming a physical crosslinking network.
6. A Fe 3+ A method for preparing a gradient-sensitivity hydrogel of EDTA dynamic coordination compounds, characterized by, The aromatic eutectic solvent is composed of a quaternary ammonium salt as a hydrogen bond acceptor and an organic acid as a hydrogen bond donor, the quaternary ammonium salt is selected from one or more of benzyltrimethylammonium chloride, benzyltrimethylammonium bromide or benzyltrimethylammonium iodide, and the organic acid is lactic acid.
7. A Fe-based alloy according to claim 2, wherein the alloy contains 0.1 to 0.5% of C. 3+ A method for preparing a gradient-sensitivity hydrogel of an EDTA dynamic coordination compound, characterized by, The feeding ratio of each main component meets one or more of the following conditions: 1) the mass-volume ratio of lignin to aromatic eutectic solvent is 0-0.2 g / mL; 2) the molar ratio of quaternary ammonium salt to organic acid is 0.5-2:1-3; 3) the molar concentration of the chelate composed of the chelating agent and the metal ions is 0-1.5 mol / L; 4) in the glycol / water solution, the molar ratio of glycol to water is 1-5:1-10; 5) the reaction temperature is controlled at 60-120 ℃.
8. The gradient-sensitivity hydrogel of claim 1, wherein, The low-temperature aging condition is standing at 2-8 ℃ for 2-6 h, and the freezing condition is freezing at-15 ℃ to-25 ℃ for 12-24 h.
9. A flexible strain sensor, characterized by The sensing element is made of the gradient sensitivity hydrogel of claim 1.
10. Use of the gradient sensitivity hydrogel of claim 1 or the flexible strain sensor of claim 9 in the preparation of equipment for robot joint limit protection, rehabilitation motion monitoring or structure health early warning.