Mechanical interlocking polyrotaxane conductive hydrogel as well as preparation method and application thereof

Abstract

The invention discloses a mechanically interlocked polyrotaxane conductive hydrogel and a preparation method and application thereof, and the hydrogel is prepared by taking quasi rotaxane formed by self-assembling a water-soluble allyl functionalized naphthalene tube and polyethylene glycol diacrylate as a dynamic crosslinking unit and performing one-step photopolymerization on the dynamic crosslinking unit and an ethylene monomer. The hydrogel has ultrahigh stretchability (fracture strain gt, 2450%), skin-like low modulus (about 8.5 kPa), excellent fatigue resistance, high ionic conductivity (7.46 mS / cm) and strong interface adhesion. The invention further discloses application of the hydrogel in preparation of high-performance flexible strain sensors and biological electrodes. In a biological electrode, stable conformal contact with the skin can be formed, high-fidelity and motion artifact-resistant electrocardio and electromyographic signal acquisition is realized, and the signal-to-noise ratio is still kept above 34 dB under dynamic motion. The preparation process is simple, the biocompatibility is good, and the application prospect in the fields of wearable medical monitoring and human-computer interaction is wide.

Description

Technical Field

[0001] This invention relates to the fields of functional polymer materials and flexible electronics, specifically to a conductive hydrogel with a mechanically interlocked topology, its preparation method, and its application in flexible strain sensors and bioelectrodes. Background Technology

[0002] Conductive hydrogels, possessing the flexibility, hydrophilicity, and ion / electron conductivity of polymer materials, have become ideal candidate materials for flexible electronic devices, biosensors, and wearable health monitoring systems. These materials can form good conformal contact with human skin, thus promising comfortable, long-term, and high-fidelity physiological signal acquisition.

[0003] However, traditional conductive hydrogels primarily rely on static covalent cross-linked networks or fragile physical interactions, resulting in generally insufficient mechanical properties (such as toughness, elongation at break, and fatigue resistance). Under repeated dynamic deformation (such as joint bending and skin stretching), the network structure is prone to irreversible damage or breakage, while the internal conductive pathways (whether ion migration paths or filler conductive networks) are also easily disrupted. This directly manifests as drift in sensing signals, decreased signal-to-noise ratio, and poor long-term stability, making it difficult to meet the urgent need for high-reliability, high-fidelity signal acquisition in motion or long-term continuous monitoring scenarios.

[0004] Polyrotaxane, as a typical mechanically interlocked molecular structure, can effectively dissipate energy and improve mechanical properties through the "molecular pulley" effect. In this structure, macrocyclic molecules are threaded onto linear polymer chains and can slide along the chains. Integrating such topologies into hydrogel networks can effectively dissipate external force energy through the reversible sliding of macrocycles, thereby endowing the material with excellent toughness, tensile strength, and fatigue resistance. However, the application of polyrotaxane structures in conductive hydrogels is limited by suitable macrocyclic molecules (which must possess water solubility, strong host-guest recognition ability, and polymerizability) and cumbersome multi-step preparation processes.

[0005] Most reported polyrotaxane hydrogels are based on cyclodextrin systems, resulting in relatively limited material types and performance control methods, which makes it difficult to meet diverse application needs. More importantly, the construction of traditional polyrotaxanes usually requires complex end-capping steps to prevent macrocycle desorption, making the synthesis process cumbersome and incompatible with the simple one-step molding process of hydrogels. This severely restricts the large-scale fabrication and application of polyrotaxane structures in flexible electronic devices.

[0006] In existing technologies, such as the prior art document CN115124662B, a polyrotaxane quasi-slip ring hydrogel and its preparation method and application, dynamic cross-linking is achieved by using carboxyl-containing naphthalene tubes (NT) and PEG-DA through hydrogen bonding, focusing on mechanical enhancement through mechanical training. However, in this method, the macrocyclic molecules do not form covalent bonds with the polymer network, and a mechanically interlocked structure cannot be formed. Its mechanical properties are no different from ordinary covalently cross-linked hydrogel materials, and it cannot dissipate external stress through the "slip ring effect." Its dynamic cross-linking depends on hydrogen bonds, and under long-term or severe dynamic use, stress concentration is prone to occur, affecting the long-term stability of the structure and the reliability of signal acquisition.

[0007] Therefore, developing novel macrocyclic molecules and matching efficient one-pot methods to simultaneously achieve quasi-rotaxane end-capping and network cross-linking, in order to construct mechanically interlocked polyrotaxane conductive hydrogels with excellent comprehensive performance, has become the key to solving the above problems and promoting the development of high-performance flexible bioelectrodes. Summary of the Invention

[0008] The present invention aims to overcome the shortcomings of the prior art, and its primary objective is to provide a novel water-soluble, polymerizable allyl-functionalized naphthalene tubule (ANT) macrocyclic molecule.

[0009] The second objective is to provide a quasi-rotaxane dynamic crosslinking unit based on the above-mentioned ANT and PEG-DA and its preparation method.

[0010] The third objective is to provide a method for preparing mechanically interlocked polyrotaxane conductive hydrogels with excellent comprehensive properties through a one-step photopolymerization process, using the aforementioned crosslinking units as the core.

[0011] The fourth objective is to provide information on the application of the aforementioned hydrogels in the fabrication of high-performance flexible strain sensors and bioelectrodes.

[0012] To achieve the above objectives, the present invention adopts the following technical solution: This invention designs and synthesizes a novel water-soluble allyl-functionalized naphthalene tube (ANT) macrocyclic molecule, which has the general formula shown in formula (1): ; Equation (1).

[0013] The molecule has the following characteristics: the carboxylate groups modified on its outer side ensure water solubility; the specific amide cavity on the inner side gives it a strong binding affinity to polyethylene glycol (PEG) chains, which is due to the synergistic hydrogen bonding and hydrophobic interaction; and the allyl double bond modified at the end provides an active site that can participate in free radical polymerization.

[0014] In this invention, ANT and PEG-DA are co-assembled in water to form a quasi-rotaxane dynamic crosslinking agent (PRC-ANT).

[0015] The molecular weight of the PEG-DA is from 10 kDa to 35 kDa.

[0016] The molar ratio of ANT to PEG-DA is 1:1 to 5:1.

[0017] The present invention discloses a method for preparing mechanically interlocked polyrotaxane conductive hydrogel, comprising the following steps: S1: Water-soluble allyl functionalized naphthalene tubes (ANT) and polyethylene glycol diacrylate (PEG-DA) are mixed in water and left to stand at 0-10℃. The ANT macrocycle can efficiently penetrate the PEG-DA chain through host-guest interaction and self-assemble to form a quasi-rotaxane crosslinking agent (PRC-ANT) solution. S2: Mix the quasi-rotaxane crosslinking agent solution obtained in step S1, the ethylene functional monomer and the photoinitiator in water to obtain a precursor solution; S3: The precursor solution is placed in a mold and subjected to polymerization under ultraviolet light. During polymerization, the PEG-DA chain is cross-linked (forming a static network) and the ANT macrocycle is covalently anchored to the polymer backbone (forming dynamic slip ring cross-linking points), thereby constructing a mechanically interlocked network in one step to obtain the mechanically interlocked polyrotaxane conductive hydrogel.

[0018] The ethylene functional monomers include neutral ethylene monomers and ionizable ethylene monomers; The neutral vinyl monomers include at least one of acrylamide, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, hydroxypropyl methacrylate, N-tris(hydroxymethyl)methacrylamide, N-(2-hydroxypropyl)methacrylamide, methyl methacrylate, and glycidyl methacrylate. The ionizable ethylene monomers include at least one of acrylic acid, methacrylic acid, sodium acrylate, lithium acrylate, potassium acrylate, itaconic acid, 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, [3-(methacryloylamino)propyl]dimethyl(3-thiopropyl)ammonium hydroxide, acryloyloxyethyltrimethylammonium chloride, and methacryloyloxyethyltrimethylammonium chloride.

[0019] The mass ratio of the neutral ethylene monomer to the ionizable ethylene monomer is 1:10 to 10:1.

[0020] During photopolymerization, a synergistic reaction occurs: (1) the double bonds at the ends of PEG-DA participate in the reaction, forming a static covalent crosslinking network; (2) simultaneously, the allyl double bonds of the ANT molecules pre-inserted into the PEG-DA chain also participate in polymerization, thereby covalently anchoring the ANT to the polymer backbone. This makes the PEG-DA chain a "axis" running through the covalently fixed macrocycle (ANT), while the ANT acts as a dynamic crosslinking point that can slide along this "axis," ultimately forming a unique mechanically interlocked topological network. Acrylic acid and sodium acrylate not only participate in the construction of the network, but the ions generated by their ionization are also the source of the high ionic conductivity of the hydrogel. The carboxyl and amide groups on the polymer chain also provide abundant hydrogen bonds, giving the hydrogel strong interfacial adhesion.

[0021] This invention relates to the application of hydrogels in flexible strain sensors. Using a mechanically interlocked polyrotaxane conductive hydrogel as the sensing and conductive core, and integrating flexible electrodes (such as metal wires or conductive fabrics) onto its surface or within it, and connecting them to a signal reading circuit, a high-performance flexible strain sensor can be fabricated. This sensor can convert deformation into a regular change in resistance / impedance, making it suitable for fields such as human motion monitoring, gesture recognition, and human-computer interaction.

[0022] The flexible sensor is specifically applied in the following scenarios: Human movement and activity monitoring: Attached to joints (such as fingers, wrists, elbows, and knees), it monitors joint flexion angles, range of motion, and frequency in real time for use in motion analysis, rehabilitation training assessment, or motion capture.

[0023] Gesture recognition and human-computer interaction: Integrated into gloves or wearable devices, it enables precise gesture control and virtual interaction by recognizing subtle movements and postures of the hands and fingers.

[0024] This invention relates to the application of hydrogels in bioelectrodes. Mechanically interlocked polyrotaxane conductive hydrogels are prepared and formed into thin sheets of a predetermined shape, which are then combined with metal current collectors (such as silver / silver chloride foil or conductive carbon cloth) to create flexible bioelectrodes. These electrodes can form a stable, conformal, low-impedance interface with the skin, enabling the acquisition of high-fidelity electrocardiogram (ECG), electromyographic (EMG), and other physiological signals, and exhibit strong anti-interference capabilities during movement.

[0025] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: 1. Innovative Network Structure and Superior Stability: Through the design of allyl-functionalized macrocyclic molecules, the intercalation of macrocycles into the PEG chain and their covalent anchoring in the network are simultaneously achieved during polymerization, forming a truly mechanically interlocked structure. Compared with "quasi-rotaxanes" that rely solely on physical interactions such as hydrogen bonds, the network topology of this invention is more stable, and the macrocycles are less prone to detachment, ensuring the structural integrity and performance stability of the material under long-term, repeated deformation.

[0026] 2. Excellent dynamic performance to meet wearable needs: The unique "sliding-anchoring" synergistic mechanism enables the material to effectively dissipate energy through large-ring sliding under external force, exhibiting tensile strength (fracture strain > 2450%) and fatigue resistance (withstanding more than 1000 cycles of 100% strain) far exceeding that of traditional hydrogels. Its skin-like low modulus and strong interfacial adhesion achieve a comfortable and stable fit with human tissue.

[0027] 3. Excellent performance of the flexible sensor: Based on this mechanically interlocked polyrotaxane hydrogel, the flexible sensor achieves an excellent combination of ultra-wide strain response (>2000%), high sensitivity, and long-term cycling stability through its "sliding-anchoring" network and dynamic conductive pathway. Simultaneously, its tissue-like softness, strong interfacial adhesion, and good biocompatibility ensure stable conformal contact with the human body or complex curved surfaces and comfortable wear, making it particularly suitable for dynamic, long-term deformation and motion signal monitoring.

[0028] 4. High-quality electrophysiological signal acquisition: Combining the aforementioned mechanical advantages with high ionic conductivity, the resulting bioelectrode maintains stable low-impedance contact with the skin in both static and dynamic states, significantly suppressing motion artifacts caused by interfacial slippage or gel rupture. Experiments show that its ECG signal-to-noise ratio (≥34dB) during exercise is significantly higher than that of commercial gel electrodes (see Comparative Experiment Example 2). Figure 7 (ef) provides a reliable tool for achieving dynamic health monitoring.

[0029] 5. Simple preparation process: The "self-assembly-photopolymerization" one-pot method avoids the cumbersome end-capping steps in the traditional polyrotaxane synthesis. The process is simple and efficient, and suitable for large-scale preparation. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the conductive hydrogel design for an example.

[0031] Figure 2 This is a diagram illustrating the dynamic slip ring effect mechanism of the conductive hydrogel of this invention.

[0032] Figure 3 1H NMR spectra of PEG20k-DA, ANT, and an equimolar mixture of the two (PRC-ANT) 1 H NMR comparison image.

[0033] Figure 4 The NMR titration curves and bonding constant fitting plots of ANT and the model guest molecule (TEG-DA) are shown.

[0034] Figure 5The mechanical properties of the example hydrogel (Hydrogel 1) and the comparative hydrogels (Hydrogel 2, 3) are compared, including stress-strain curves, cyclic tensile curves, adhesion strength, and puncture resistance.

[0035] Figure 6 This is a comparison graph showing the resistance change stability of the hydrogels in the examples and comparative examples under cyclic stretching.

[0036] Figure 7 This is a signal response diagram of a flexible sensor based on the hydrogel (Hydrogel 1) of the present invention for monitoring the movement of different joints in the human body.

[0037] Figure 8 This is a performance comparison chart of the bioelectrode based on the hydrogel 1 of this invention and a commercial gel electrode (CE) in acquiring electrocardiogram (ECG) and electromyography (EMG) signals under static and exercise conditions, including signal waveforms, signal-to-noise ratio, etc. Detailed Implementation

[0038] The present invention will be described in detail below with reference to embodiments and accompanying drawings. These embodiments are for illustrative purposes only and do not constitute a limitation thereof.

[0039] Example 1: Synthesis of allyl-functionalized naphthalene tubes (ANT) The specific synthetic method of allyl-functionalized naphthalene tubes (ANT) is as follows: ; (1) Synthesis of intermediate S1: In a 2 L three-necked flask, under an inert atmosphere (such as argon), 100 g (624 mmol) of 2,6-dihydroxynaphthalene was dissolved in 1 L of anhydrous N,N-dimethylformamide (DMF). The reaction mixture was cooled to 0 °C in an ice bath, and a 60% sodium hydride mineral oil dispersion (23.73 g, 593.1 mmol) was slowly added with stirring. After stirring for 1 hour, 200 mL of allyl bromide (68 g, 562 mmol) in DMF was slowly added dropwise through a constant-pressure dropping funnel. After the addition was complete, the ice bath was removed, and the reaction mixture was allowed to warm to room temperature naturally and stirred for 12 hours at room temperature. After the reaction was complete, the reaction mixture was slowly poured into 1 L of ice water while stirring. Subsequently, the pH of the mixture was adjusted to neutral (approximately 7) with dilute hydrochloric acid aqueous solution, at which point a large amount of solid precipitated. The solid was collected by filtration and washed with a small amount of cold water. The crude product was purified by silica gel column chromatography using a mixture of petroleum ether and dichloromethane as the eluent (volume ratio could be varied, for example, from 5:1 to 1:1). The target fraction was collected and concentrated to give a white solid intermediate S1 (29.4 g, yield 24%) with a melting point >300 °C.

[0040] (2) Synthesis of intermediate S3: Intermediate S1 (15.4 g, 77 mmol) obtained in the previous step, another known intermediate S2 (18.9 g, 77 mmol), and trifluoroacetic acid (TFA, 78 mL) were dissolved together in 300 mL of dichloromethane (DCM) to form a mixed solution. Under an inert atmosphere and with stirring, this mixed solution was slowly added dropwise over 15 minutes to 100 mL of DCM solution containing 1,1,3,3-tetramethoxypropane (12.6 g, 77 mmol). After the addition was complete, the reaction mixture was stirred at room temperature for 12 hours. After the reaction was complete, the reaction solution was poured into ice water and carefully neutralized with a saturated sodium bicarbonate (NaHCO3) aqueous solution until no more bubbles were generated. The aqueous phase was extracted with DCM (3 × 100 mL). All organic phases were combined, dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to remove the solvent, yielding the crude product. The crude product was purified by silica gel column chromatography with petroleum ether / dichloromethane as the eluent to give a white solid intermediate S3 (10.2 g, yield 27%) with a melting point >300 °C.

[0041] (3) Synthesis of intermediate S4: Under an inert atmosphere and at 0 °C, 1,1-dichlorodimethyl ether (7.6 mL, 84 mmol) was slowly added to 250 mL of DCM solution containing intermediate S3 (10.2 g, 21 mmol), and the mixture was stirred for 10 minutes. Subsequently, 70 mL of DCM solution containing titanium tetrachloride (TiCl4, 9.3 mL, 84 mmol) was slowly added dropwise over 1 hour using a constant-pressure dropping funnel. After the addition was complete, the reaction system was allowed to rise naturally to room temperature, and the reaction was stirred at room temperature for 12 hours. After the reaction was complete, most of the volatile organic solvents (THF and acetone) were removed by distillation under reduced pressure. A 1 mol / L aqueous solution of hydrochloric acid was added to the remaining aqueous phase to adjust the pH to 5-6, at which point a pale yellow solid precipitated. The solid was filtered, collected, washed thoroughly with water, and dried to obtain a pale yellow solid intermediate S5 (a diacid compound) with a yield of 7.8 g (90% yield) and a melting point above 300 °C. (10.2g, yield 90%), melting point > 300℃.

[0042] (4) Synthesis of intermediate S5: S4 (8.2 g, 15.2 mmol), sodium chlorite (11.2 g, 123 mmol), and aminosulfonic acid (11.1 g, 114 mmol) were added to a mixed solvent of water (220 mL) / THF (220 mL) / acetone (332 mL), stirred at room temperature for 12 h, concentrated to remove volatile solvents, and the pH was adjusted to 5-6 with 1 mol / L hydrochloric acid. The precipitate was collected by filtration, washed with water, and dried to obtain a pale yellow solid S5 (7.8 g, yield 90%) with a melting point >300℃.

[0043] (5) Synthesis of anti-S7: S5 (2.0 g, 3.5 mmol) and PyBOP (5.8 g, 11.1 mmol) in 60 mL of DMF solution, and S6 (2.9 g, 3.5 mmol) in 60 mL of DMF solution, were simultaneously added dropwise over 8 h to a 500 mL DMF solution containing DIEA (10.0 mL, 57.3 mmol) and PyBOP (5.8 g, 11.1 mmol). The reaction was carried out under argon atmosphere at room temperature for 48 h. Most of the solvent was removed by concentration, and 400 mL of methanol was added. The precipitate was collected by filtration and purified by silica gel column chromatography (eluent: dichloromethane / methanol) to give a white solid anti-S7 (0.71 g, yield 18.1%) with a melting point >300 °C.

[0044] (6) Synthesis of ANT: Anti-S7 (0.15 g, 0.13 mmol) was placed in a 500 mL single-necked flask, and methanol (150 mL), water (75 mL), THF (150 mL), and sodium hydroxide (0.32 g, 8.0 mmol) were added. The mixture was stirred at 50 °C for 12 h, and the volatile solvent was removed by concentration. The residue was dissolved in 75 mL of water, and 2 mL of concentrated hydrochloric acid was added. The mixture was sonicated for 30 min to induce precipitation. After filtration, the precipitate was washed with water until neutral and dried under vacuum to obtain anti-S8 (0.13 g, 94% yield). Three equivalents of sodium hydroxide aqueous solution were added to anti-S8, and the mixture was stirred to dissolve and then freeze-dried to obtain a white solid ANT.

[0045] Example 2: Preparation of quasi-rotaxane crosslinking agent (PRC-ANT) solution The preparation process includes: A certain amount of the host molecule ANT is added to the sample vial, and the molar ratio of ANT to PEG20k-DA is controlled to be n(ANT) / n(PEG20k-DA)=1 / 1. The mass ratio of PEG20k-DA to deionized water is controlled to be m(PEG20k-DA) / m(H2O)=1 / 9. After stirring and mixing evenly, the solution is placed in a refrigerator at 0~7℃ for 24h to obtain a quasi-rotaxane slip ring crosslinking agent (called PRC-ANT) with the host molecule threaded PEG20k-DA.

[0046] pass 1 H NMR characterization confirmed the assembly effect, such as Figure 3 As shown, the chemical shift of the specific hydrogen of PEG after mixing with ANT exhibits a significant high-field shift, indicating that it successfully penetrates the hydrophobic cavity of ANT to form a quasi-rotaxane structure.

[0047] In addition, nuclear magnetic titration was used to determine the bonding ability between the model guest molecule, tetraethylene glycol diacrylate (TEG-DA), and the host molecule ANT. Figure 4 This indicates that the bonding constant of ANT to TEG-DA reaches 10. 4 This further confirms that PEG and ANT can easily form rotaxane crosslinking agents in water. Example 3: Preparation of mechanically interlocked polyrotaxane conductive hydrogel

[0048] This embodiment uses a mechanically interlocked polyrotaxane conductive hydrogel, prepared with the optimal formulation as an example, referring to... Figure 1 Its preparation process includes: Take 40 μL of the PRC-ANT stock solution prepared in Example 2 (containing approximately 4 mg of solids) and add it to a 1.5 ml centrifuge tube. Add 50 mg of acrylamide (AM), 50 μL of acrylic acid (AAc), 15 mg of sodium acrylate (AANa), and 0.3 g of photoinitiator Irgacure I2959, and add deionized water to make the total volume 400 μL. Shake and stir until homogeneous to obtain a hydrogel precursor solution. Pour this solution into a polytetrafluoroethylene mold (e.g., 40 mm × 4 mm × 2 mm), cover it with a quartz glass plate, and irradiate it under a 365 nm wavelength ultraviolet lamp for 30 minutes to obtain a transparent mechanically interlocked polyrotaxane conductive hydrogel, named Hydrogel 1.

[0049] The dynamic slip ring effect mechanism of the conductive hydrogel of this invention, such as... Figure 2 As shown in Figure a, the dynamic slip ring crosslinking points can effectively slide and dissipate energy under external force, endowing the material with ultra-high tensile strength (fracture strain > 2450%), excellent toughness, and outstanding fatigue resistance (able to withstand more than a thousand repeated tensile cycles with stable performance), such as... Figure 6 As shown in a.

[0050] Electrical and interfacial properties: High ionic conductivity (e.g., 7.46 mS / cm) is achieved by providing ionic conductivity pathways through the ionization of functional monomers (e.g., AAc, NaAA), without the need to introduce rigid conductive fillers that are prone to leakage or have poor biocompatibility.

[0051] Adaptability and adhesion properties: The material has a low modulus (e.g., 8.5 kPa) that matches human skin and strong interfacial adhesion based on abundant hydrogen bonds.

[0052] The conductive hydrogel of this invention can be used to fabricate flexible sensors and bioelectrodes, such as... Figure 2 As shown in b, it is attached to joints (such as fingers, wrists, elbows, and knees) to monitor joint flexion angles, range of motion, and frequency in real time for motion analysis, rehabilitation training assessment, or motion capture. It can also acquire high-fidelity electrocardiogram (ECG) and electromyography (EMG) signals, monitoring various mechanical signals ranging from micro-vibrations to large-amplitude joint movements. Comparative Example 1

[0053] This comparative example discloses a conductive hydrogel. The preparation method is identical to that of Example 3, except that ANT is not added and an equivalent molar amount of PEG20k-DA as a conventional covalent crosslinking agent is added (as in Example 2). The prepared statically covalently crosslinked conductive hydrogel is referred to as hydrogel 2. Figure 1 As shown. Comparative Example 2

[0054] This comparative example discloses a conductive hydrogel. The preparation method is identical to Example 3, except that an amide ring naphthalene tube (NT) with a structure similar to ANT but without terminal allyl double bonds is used instead of ANT. Since NT lacks polymerizable double bonds, it cannot be covalently anchored in the network after polymerization and exists only through physical inclusion. The prepared conductive hydrogel is referred to as hydrogel 3. Figure 1 As shown.

[0055] The molecular structure of NT is shown in formula (2): ; (Equation 2). Comparative Experiment Example 1

[0056] 1. To verify the effect of mechanically interlocked polyrotaxane networks on improving the overall performance of hydrogels, the following comparative experiments were conducted in the examples: Control hydrogels (denoted as hydrogel 2 and hydrogel 3) were prepared according to the methods described in Comparative Examples 1 and 2, respectively. These hydrogels were then subjected to a series of performance tests compared with the mechanically interlocked polyrotaxane conductive hydrogel (denoted as hydrogel 1) prepared in Example 3. The results are as follows: Figure 5-8 As shown.

[0057] 1. Tensile mechanical properties The mechanical behavior of three hydrogels was tested using uniaxial tensile experiments. Figure 5As shown in a and 5b, under the same crosslinking agent concentration, the hydrogel 1 provided by this invention simultaneously exhibits higher tensile strength and elongation at break, successfully overcoming the strength-toughness balance problem commonly found in traditional hydrogels. This performance improvement is attributed to the dynamic movement capability of the sliding cyclic structural units (ANTs) along the linear PEG chains in the polyrotaxane network, i.e., the "pulley effect." This effect enables efficient stress distribution and dissipation during material deformation, thereby delaying fracture (e.g., ...). Figure 2 (as shown in a). In contrast, hydrogel 2 and hydrogel 3 use static crosslinking points, which easily cause local stress concentration, leading to premature material failure.

[0058] 2. Cyclic durability and resilience like Figure 5 As shown in Figure d, under continuous tensile loading-unloading cyclic testing at 100% strain, hydrogel 1 exhibits excellent resilience and fatigue resistance. After 100 cycles, its residual strain is less than 5%, and its hysteresis ratio remains consistently below 8%. This outstanding recovery performance is attributed to the reversible sliding mechanism of the ANT element, which dissipates energy in each cycle without causing permanent network damage. In contrast, hydrogel 2 and hydrogel 3 show significant stress decay and poor recovery capabilities.

[0059] 3. Interfacial adhesion properties The adhesion strength of three hydrogels on different substrates (such as pigskin, stainless steel, and glass) was evaluated using a 180° overlap shear test. Figure 5 As shown in Figure i, although all three contain the same adhesive functional groups, the adhesive shear strength of hydrogel 1 is significantly higher than that of hydrogel 2 and hydrogel 3. This indicates that its superior adhesive performance mainly stems from the energy dissipation achieved by the sliding cross-linked structure within the network, rather than solely relying on surface chemical interactions. During the peeling process, the sliding cross-linking points promote stress distribution and molecular chain extension, consuming energy through internal friction and network recombination, thereby inhibiting interfacial crack propagation and improving adhesive strength.

[0060] 4. Puncture resistance A puncture test was performed using a 1 mm diameter metal needle, and the results were as follows: Figure 5 As shown in g, hydrogel 1 can still undergo large deformation without breaking even when the needle displacement reaches 11 mm, exhibiting excellent puncture resistance. Under the same conditions, hydrogel 2 is easily punctured; although hydrogel 3 did not break, its puncture load was lower than that of hydrogel 1. This result further confirms that the mechanically interlocked slip ring network has the effect of inhibiting crack propagation.

[0061] 5. Sensing stability Electrical stability, such as Figure 6 As shown, after 1000 consecutive loading-unloading cycles at 100% strain, the electrical signal output of hydrogel 1 remained highly stable with no significant attenuation; while the electrical signals of hydrogel 2 and hydrogel 3 gradually decreased with increasing cycle count. This indicates that the mechanical interlocking structure provided by this invention can effectively maintain the integrity of the conductive network, avoid irreversible damage accumulation, and thus endow the sensor with excellent durability.

[0062] 7. Practical Application Demonstration Sensing applications, such as Figure 7 As shown, the sensor fabricated using hydrogel 1 can be closely fitted to different joints of the human body for real-time monitoring of various movement behaviors. The sensor resistance changes systematically with strain / pressure, demonstrating good response performance and potential for wearable applications.

[0063] In summary, the mechanically interlocked polyrotaxane network hydrogel (hydrogel 1) involved in this invention is significantly superior to the statically cross-linked control hydrogel in terms of mechanical strength, resilience, adhesion, puncture resistance, and sensing stability, fully demonstrating the positive effect of this dynamic network structure in improving the overall performance of hydrogels. Comparative Experiment Example 2

[0064] Flexible bioelectrodes were prepared using hydrogel 1, hydrogel 2, and hydrogel 3, respectively, according to the method in Example 3, and their performance for skin impedance measurement and acquisition of human electrophysiological signals (such as electrocardiogram ECG and electromyography EMG) was systematically evaluated.

[0065] 1. Skin-electrode interface impedance: Applications of bioelectrodes, such as Figure 8 As shown, the interfacial properties of the electrodes are evaluated by measuring the skin-electrode impedance. Figure 8 As shown in a, from 1 Hz to 10 5 In the Hz frequency range, the impedance of the electrode made from hydrogel 1 is significantly lower than that of commercial standard wet gel electrodes. This superior performance is attributed to its high volumetric ionic conductivity and tissue-matched Young's modulus, which synergistically achieve close adhesion to the skin surface, thereby effectively increasing the conductive contact area. Notably, the hydrogel 1 electrode exhibits the lowest impedance among all tested hydrogels, thanks to its optimized composition and stable mechanical interlocking network structure, which lays an ideal foundation for high-fidelity bioelectrical signal acquisition.

[0066] 2. Electrocardiogram signal acquisition performance: The actual acquisition effect of the electrodes was verified by monitoring the electrocardiogram. Figure 8 b and 8c show representative ECG waveforms obtained from a hydrogel 1 electrode and a commercial wet gel electrode (CE), respectively.

[0067] The signals acquired by the hydrogel 1 electrode clearly presented all key diagnostic waveforms: the P wave (atrial depolarization), the QRS complex (ventricular depolarization), and the T wave (ventricular repolarization). The measured RR interval was approximately 0.83 seconds, corresponding to a heart rate of 72 beats per minute, which is within the normal resting range.

[0068] Although it is comparable to commercial gels in terms of sensitivity characterized by the P / R peak voltage ratio (P / R) ( Figure 8 d), but there is a significant difference in signal quality. The hydrogel 1 electrode achieved a high signal-to-noise ratio of 42.5 dB, while the commercial gel electrode (CE) only achieved 23.3 dB ( Figure 8 d). This improvement is mainly due to the superior interfacial contact performance and inherent noise suppression capability of the hydrogel electrode of this invention.

[0069] More importantly, the electrodes of this invention maintain excellent signal stability even under dynamic conditions. For example... Figure 8 As shown in e and 8f, after 10 minutes of jumping exercise (heart rate increasing from 72 bpm to 125 bpm), the hydrogel 1 electrode continued to output high-quality ECG waveforms with a signal-to-noise ratio (SNR) above 34.5 dB. Under the same exercise conditions, the SNR of commercial gel electrodes dropped sharply from 23.3 dB to 6.4 dB. This significant difference indicates that the skin-like softness and strong, fatigue-resistant adhesion of hydrogel 1 are crucial for reliably acquiring biosignals during physical activity, while traditional rigid or poorly adhesive electrodes are prone to failure under such conditions.

[0070] 3. Electromyography signal acquisition performance: The hydrogel electrode was further applied to electromyography (EMG) signal acquisition. During the fist-clenching (brachioradialis muscle contraction) action, the hydrogel 1 electrode could instantly record clear and stable EMG signals, which disappeared when relaxed. Figure 8 g). During repeated fist-clenching cycles, the signal-to-noise ratio acquired by this electrode reached 45.8 dB, while that of commercial electrodes was only 28.3 dB.

[0071] Furthermore, the system demonstrated quantitative monitoring capabilities: when subjects applied different levels of grip force (5 kg, 10 kg, 20 kg) using a grip strength meter, the recorded EMG signal amplitude increased accordingly with the increase of applied force. Figure 8 (h), indicating its potential application in assessing muscle exertion.

[0072] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A mechanically interlocking polyrotaxane conductive hydrogel, characterized in that, It is prepared by a one-step photopolymerization reaction of a reaction system containing the following components: (a) Dynamic crosslinking unit: a quasi-rotaxane structure formed by self-assembly of water-soluble allyl functionalized naphthalene tube (ANT) and polyethylene glycol diacrylate (PEG-DA) through host-guest interaction, wherein the structure of the ANT includes a naphthalene tube backbone, a carboxyl group or carboxylate group modified on the outside of the backbone to provide water-soluble properties, and a polymerizable allyl group modified at the end of the backbone. (b) Ethylene functional monomers, including neutral ethylene monomers and ionizable ethylene monomers; (c) Photoinitiators; The photopolymerization reaction causes both the acrylate double bonds at the PEG-DA end and the allyl double bonds at the ANT end to participate in covalent crosslinking, thereby forming a mechanically interlocked topology that simultaneously possesses a static covalent crosslinking network and dynamic slip ring crosslinking points based on quasi-rotaxane.

2. The mechanically interlocked polyrotaxane conductive hydrogel according to claim 1, characterized in that, The water-soluble allyl-functionalized naphthalene tube (ANT) has the general formula shown in formula (1): ； Equation (1).

3. The mechanically interlocked polyrotaxane conductive hydrogel according to claim 1, characterized in that, The molecular weight of the PEG-DA is from 10 kDa to 35 kDa.

4. The mechanically interlocked polyrotaxane conductive hydrogel according to claim 1, characterized in that, The molar ratio of ANT to PEG-DA is 1:1 to 5:

1.

5. The mechanically interlocked polyrotaxane conductive hydrogel according to claim 1, characterized in that, The neutral vinyl monomers include at least one of acrylamide, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, hydroxypropyl methacrylate, N-tris(hydroxymethyl)methacrylamide, N-(2-hydroxypropyl)methacrylamide, methyl methacrylate, and glycidyl methacrylate. The ionizable ethylene monomers include at least one of acrylic acid, methacrylic acid, sodium acrylate, lithium acrylate, potassium acrylate, itaconic acid, 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, [3-(methacryloylamino)propyl]dimethyl(3-thiopropyl)ammonium hydroxide, acryloyloxyethyltrimethylammonium chloride, and methacryloyloxyethyltrimethylammonium chloride.

6. The mechanically interlocked polyrotaxane conductive hydrogel according to claim 5, characterized in that, The mass ratio of the neutral ethylene monomer to the ionizable ethylene monomer is 1:10 to 10:

1.

7. A method for preparing the mechanically interlocked polyrotaxane conductive hydrogel according to any one of claims 1-6, characterized in that, Includes the following steps: S1: Water-soluble allyl functionalized naphthalene tubes (ANT) are mixed with polyethylene glycol diacrylate (PEG-DA) in water, allowing ANT to penetrate the PEG-DA chain and self-assemble to form a quasi-rotaxane crosslinking agent solution; S2: Mix the quasi-rotaxane crosslinking agent solution obtained in step S1, the ethylene functional monomer and the photoinitiator in water to obtain a precursor solution; S3: The precursor solution is placed in a mold and subjected to polymerization under ultraviolet light to obtain the mechanically interlocked polyrotaxane conductive hydrogel.

8. A flexible strain sensor, characterized in that, Its sensing unit is composed of mechanically interlocked polyrotaxane conductive hydrogel as described in any one of claims 1-6.

9. A bioelectrode, characterized in that, It includes an electrode substrate and a conductive gel layer disposed on the electrode substrate, wherein the conductive gel layer is composed of mechanically interlocked polyrotaxane conductive hydrogel as described in any one of claims 1-6.

10. The application of the bioelectrode according to claim 9 in acquiring human electrocardiogram or electromyogram signals.

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