Dynamic hydrogen bond / ion network multi-mode sensing flexible material and preparation method thereof

Abstract

The invention belongs to the field of multi-mode sensing flexible materials and electronics, and discloses a multi-mode sensing flexible material based on a dynamic hydrogen bond / ionic network and a preparation method and application thereof.According to the material, a hydrophilic monomer and a monomer containing quaternary ammonium cation groups are copolymerized to form a polymer network with the hydrogen bond interaction and the ionic interaction; after a photoinitiator I2959 is introduced, the transparent hydrogel-like flexible material is obtained through uniform dispersion and curing under irradiation of 365 nm ultraviolet light, and the material can realize reversible mechanical transformation from rigidity and plasticity (30% RH) to soft elasticity (60% RH) under regulation and control of environment humidity, is endowed with self-plasticizing, shape memory and thermal programmable characteristics, and keeps excellent tensile property and high optical transparency. A flexible resistance-type humidity sensor and a triboelectric tactile sensor constructed based on the material can realize multi-mode signal sensing, and can be further integrated into wearable sensing equipment for monitoring physiological activities such as human body movement and respiration in real time and material tactile recognition.

Description

Technical Field

[0001] This invention relates to the field of flexible sensors and smart response materials, and in particular to a flexible sensing material capable of reversible mechanical control in dynamic environments, and possessing multimodal functions such as humidity response and triboelectric sensing, as well as its preparation method and applications. Background Technology

[0002] Multimodal sensing flexible materials are a class of functional materials that can generate measurable signal outputs under various physical or chemical stimuli (such as humidity, pressure, friction, etc.) and possess excellent flexibility, stretchability, and environmental adaptability. In recent years, they have attracted widespread attention in smart devices such as wearable sensing, environmental monitoring, and human-computer interaction. In particular, materials that respond to changes in environmental humidity and are accompanied by regulation of their own mechanical properties have become a research hotspot in the field of smart flexible materials.

[0003] Material-based humidity sensing materials have attracted widespread attention in recent years due to their excellent biocompatibility, ultra-high tensile properties (strain exceeding 3000%), and rapid response to changes in environmental humidity. For example, researchers have developed LiCl and MXene-reinforced PVA / PAM dual-network hydrogel materials, achieving a humidity sensitivity of approximately -103.4% / %RH, and improving sensing stability by introducing ion-conducting pathways [Adv. Funct. Mater. 2024, 34, 2402853]. However, existing hydrogel-like humidity-sensitive materials generally suffer from poor durability, narrow humidity response range, and slow response and recovery due to high water content, making it difficult to operate stably for long periods under complex real-world conditions. In particular, many high-sensitivity material sensors can only operate reliably within a narrow low-to-medium humidity range, or experience signal hysteresis and material softening due to moisture accumulation in high-humidity environments.

[0004] In addition, most of these flexible materials currently have single-modal functions, with only humidity or pressure response capabilities. They are difficult to integrate functions such as tactile sensing and material contact recognition, resulting in limited functionality and restricting their applicability in complex application scenarios.

[0005] Given the limitations of the existing technologies, there is an urgent need to develop a flexible material that can reversibly adjust mechanical stiffness under environmental control, has stable sensing performance, and can achieve multimodal functional output, in order to solve the technical problems of traditional materials such as narrow response range, poor sensitivity, lag in structural response, and low functional integration. Summary of the Invention

[0006] Based on the aforementioned technical background, this invention proposes a polymer network material, which is copolymerized from hydrophilic monomers and polymerizable ionic monomers containing quaternary ammonium cations to form a network structure with dynamic hydrogen bonding. This network can achieve reversible phase transitions under different humidity environments: it exhibits a rigid plastic state at approximately 30% relative humidity, while transforming into a flexible elastic state at 60% relative humidity, thus achieving humidity-driven stiffness switching. This material system possesses self-plasticizing properties, shape memory effect, and thermal programmability, while also exhibiting excellent tensile properties (maximum strain up to 3130%), making it suitable for flexible device applications under dynamic deformation conditions. To verify its application potential, this invention applies the material to multimodal flexible sensors, including a flexible resistive humidity sensor with a sensitivity of up to −300% / %RH in the 30–60% relative humidity range. Furthermore, as a triboelectric tactile layer combined with a synchronous signal recognition algorithm, a material classification accuracy of >99% can be achieved. This type of stimulus-responsive conductive gel material provides a material basis for constructing a new generation of flexible electronic skin with environmental adaptability and multifunctional sensing capabilities, and is suitable for real-time sensing and human-computer interaction in fields such as intelligent robots and wearable health monitoring.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A dynamic hydrogen bond / ion network multimodal sensing flexible material is composed of a polymer network formed by copolymerization of hydrophilic monomers and polymer monomers containing quaternary ammonium cationic groups. It forms a dynamic cross-linked structure through reversible hydrogen bonding and ionic interactions. It exhibits a rigid plastic state at a relative humidity of 30% and transforms into a flexible elastic state at a relative humidity of 60%. It can reversibly switch between the rigid plastic state and the flexible elastic state with changes in the relative humidity of the environment, thereby realizing stiffness switching for humidity regulation.

[0008] Preferably, the hydrophilic monomer includes, but is not limited to, one of acrylamide, acrylic acid, and carboxyethyl methacrylate.

[0009] Preferably, the polymer monomer containing quaternary ammonium cationic groups includes, but is not limited to, one of (3-acrylamidopropyl)trimethylammonium chloride, acryloyloxyethyltrimethylammonium chloride, and dimethyldiallylammonium chloride.

[0010] Another objective of this invention is to provide a method for preparing the above-mentioned dynamic hydrogen bond / ion network multimodal sensing flexible material, which is prepared by photoinitiated free radical polymerization, and the specific steps are as follows: S1: Mix the polymer monomer containing quaternary ammonium cationic groups and the hydrophilic monomer at room temperature to form a transparent solution A; S2: Add photoinitiator I2959 to transparent solution A, stir again for 10 min to form precursor solution B; S3: Pour the obtained precursor solution B into a polytetrafluoroethylene mold and place it under 365nm ultraviolet light irradiation. After 3 minutes of curing treatment, the flexible material is obtained.

[0011] Preferably, in step S1, the molar ratio of the polymer monomer containing quaternary ammonium cationic groups to the hydrophilic monomer is 1:0.5-1.5.

[0012] Preferably, in step S2, the mass ratio of photoinitiator I2959 to polymer monomers containing quaternary ammonium cationic groups is 1:2000.

[0013] Preferably, in step S2, when preparing the gel precursor solution, the stirring temperature is 25-30℃ and the stirring speed is 300-400 rpm.

[0014] Preferably, in step S3, the temperature of the photocuring crosslinking reaction is 25-30℃, and the curing time is 3 minutes.

[0015] Another objective of this invention is to provide a flexible humidity sensor, which is prepared using the aforementioned flexible sensing material as a humidity-sensitive layer. This humidity-sensitive layer exhibits a change in resistance value in response to changes in ambient relative humidity, and has a humidity sensitivity of −300% / %RH within a relative humidity range of 30-60%.

[0016] Another objective of this invention is to provide a triboelectric tactile sensor, which is prepared using the aforementioned flexible sensing material as the positive electrode friction layer. The positive electrode friction layer repeatedly contacts and separates from another negative electrode material to generate characteristic electrical signals. By performing pattern recognition on these electrical signals, different touched objects can be distinguished. The sensor has an accuracy rate of >99% in recognizing different materials.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The flexible material of the present invention is a polymer formed by copolymerizing hydrophilic monomers with polymer monomers containing quaternary ammonium cationic groups. It has excellent mechanical properties. Through the synergistic dynamic interaction within the system, the mechanical properties, strain sensing ability and high humidity sensitivity of the material are significantly improved.

[0018] 2. The flexible material of the present invention can achieve reversible phase transition under different humidity environments: it exhibits a rigid plastic state at a relative humidity of about 30%, while it transforms into a flexible elastic state at a relative humidity of 60%, thereby realizing humidity-driven stiffness switching.

[0019] 3. The flexible material system of the present invention has self-plasticizing properties, shape memory effect and thermal programmability, and also has excellent tensile properties (maximum strain up to 3130%), making it suitable for flexible device applications under dynamic deformation conditions.

[0020] 4. By applying the flexible material of the present invention to a multimodal flexible sensor, a flexible resistive humidity sensor with a sensitivity of up to −300% / %RH in the 30–60% relative humidity range can be fabricated. As a triboelectric tactile layer and combined with a synchronous signal recognition algorithm, a material classification accuracy of >99% can be achieved.

[0021] 5. The flexible material of the present invention has high humidity sensitivity and sensing sensitivity, and can be used in wearable sensing electronic devices that detect human movement and breathing. Attached Figure Description

[0022] Figure 1 a is a graph showing the stress-strain variation trend of the materials in Examples 1-5 of the present invention with AM content at 40% humidity; Figure 1 b is a graph showing the stress-strain variation of the materials in Examples 1-5 with AM content at 50% humidity; Figure 1 c is the stress-strain curve of the material in Example 3 under 40%-60% RH humidity; Figure 1 d is a graph showing the trend of material variation in Example 3 under cyclic loading-unloading tests at 50% humidity; Figure 1 e represents the trend of material variation in Example 3 under 100% strain after 10 loading-unloading cycles at 50% humidity; Figure 1 f is a dynamic change diagram of stress relaxation of the material in Example 3 under 50 compression cycles at 50% humidity; Figure 1 g is a graph showing the trend of overlap shear adhesion between the material of Example 3 and different substrates under 50% humidity. Figure 1 h is a direct view comparing the quantitative adhesion strength between the material of Example 3 and different substrates at 50% humidity; Figure 1 i is a schematic diagram of the material adhesion measurement scheme in Example 3 under 50% humidity.

[0023] Figure 2 The XPS spectrum of APTC1-AM1 material in Example 3 of this invention ( Figure 2 a) C 1s diagram ( Figure 2 b) N 1s plot ( Figure 2 c) O 1s diagram ( Figure 2 d) Cl 2p spectrum ( Figure 2 e) Transmission spectrum of a 2mm thick material ( Figure 2 f, a schematic diagram of the transmission spectrum of a 2mm thick material covering a rainbow background.

[0024] Figure 3 This is a temperature sensitivity photograph of the APTC1-AM1 material in Example 3 of the present invention. Figure 3a); Actual observations and corresponding thermal images of the shape memory effect of APTC1-AM1 material ( Figure 3 b).

[0025] Figure 4 The graph shows the relative resistance change trend of the APTC1-AM1 material sensor of Example 3 of the present invention at low strain levels (10-70%) under 50% humidity. Figure 4 a) Trend of relative resistance of the sensor under high strain levels (100-300%) Figure 4 b).

[0026] Figure 5 The APTC1-AM1 material sensor of Embodiment 3 of the present invention is used in the finger ( Figure 5 a) Wrist ( Figure 5 b) Elbow ( Figure 5 c) Response trend graph during motion monitoring; and trend graph of material resistance returning to its original value after cutting and reconnection without heat application. Figure 5 d).

[0027] Figure 6 The humidity-sensitive response curve of the APTC1-AM1 material sensor in Embodiment 3 of the present invention is shown in the figure. Figure 6 a); Hygroscopic-desorption kinetics curves of APTC1-AM1 material under 75% humidity and 25℃ conditions ( Figure 6 b); Trend of cyclic desorption stability of APTC1-AM1 material over 20 days under alternating humidity (30% humidity ↔ 60% humidity) ( Figure 6 c); Desorption cycle variation diagram of APTC1-AM1 material with resistance ( Figure 6 d).

[0028] Figure 7 a represents the humidity response of the APTC1-AM1 humidity sensor prepared in Example 3 of this invention to the surface humidity of a non-contact finger. Figure 7 b is a dynamic response diagram to breathing through the mouth; Figure 7 c is a dynamic response diagram for breathing through the nose; Figure 7 d is a schematic diagram of the APTC1-AM1 thin-film humidity sensor integrated into a mask for real-time monitoring of human respiration; Figure 7 e is a graph showing the changes in sensor signals during rapid and slow breathing. Figure 7 f is a graph showing the signal changes of the breathing sensor used for sleep apnea monitoring.

[0029] Figure 8 A schematic diagram illustrating the formation mechanism of the contact-induced characteristic electrical signals of the APTC1-AM1 triboelectric nanogenerator prepared in Example 3 of this invention. Figure 8a) Hotspot region map for information extraction using convolutional neural network; corresponding confusion matrix map for object recognition obtained from the CNN model using APTC1-AM1 triboelectric nanogenerator device signal. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1 Preparation of prepolymer solution: 2.74 g of (3-acrylamidopropyl)trimethylammonium chloride (APTC) and 0.355 g of acrylamide (AM) were placed in a round-bottom flask and mixed. After stirring at room temperature for 30 min, a uniform, clear and transparent solution was obtained. The prepared prepolymer solution was sealed and ready for use.

[0032] Material preparation: 1.37 mg of photoinitiator (I2959) was added to the prepolymer solution and magnetically stirred at 25 °C for 10 min at a stirring speed of 300 rpm to form a material precursor liquid; the well-stirred material precursor liquid was transferred to a polytetrafluoroethylene mold and placed in an ultraviolet curing machine for curing for 3 min to obtain the material.

[0033] Example 2 Preparation of prepolymer solution: 2.74 g of (3-acrylamidopropyl)trimethylammonium chloride (APTC) and 0.5325 g of acrylamide (AM) were placed in a round-bottom flask and mixed. After stirring at room temperature for 30 min, a uniform, clear and transparent solution was obtained. The prepared prepolymer solution was sealed and ready for use.

[0034] Material preparation: 1.37 mg of photoinitiator (I2959) was added to the prepolymer solution and magnetically stirred at 25 °C for 10 min at a stirring speed of 300 rpm to form a material precursor liquid; the well-stirred material precursor liquid was transferred to a polytetrafluoroethylene mold and placed in an ultraviolet curing machine for curing for 3 min to obtain the material.

[0035] Example 3 Preparation of prepolymer solution: 2.74 g of (3-acrylamidopropyl)trimethylammonium chloride (APTC) and 0.71 g of acrylamide (AM) were placed in a round-bottom flask and mixed. After stirring at room temperature for 30 min, a uniform, clear and transparent solution was obtained. The prepared prepolymer solution was sealed and ready for use.

[0036] Material preparation: 1.37 mg of photoinitiator (I2959) was added to the prepolymer solution and magnetically stirred at 25 °C for 10 min at a stirring speed of 300 rpm to form a material precursor liquid; the well-stirred material precursor liquid was transferred to a polytetrafluoroethylene mold and placed in an ultraviolet curing machine for curing for 3 min to obtain the material.

[0037] Example 4 Preparation of prepolymer solution: 2.74 g of (3-acrylamidopropyl)trimethylammonium chloride (APTC) and 0.8875 g of acrylamide (AM) were placed in a round-bottom flask and mixed. After stirring at room temperature for 30 min, a uniform, clear and transparent solution was obtained. The prepared prepolymer solution was sealed and ready for use.

[0038] Material preparation: 1.37 mg of photoinitiator (I2959) was added to the prepolymer solution and magnetically stirred at 25 °C for 10 min at a stirring speed of 300 rpm to form a material precursor liquid; the well-stirred material precursor liquid was transferred to a polytetrafluoroethylene mold and placed in an ultraviolet curing machine for curing for 3 min to obtain the material.

[0039] Example 5 Preparation of prepolymer solution: 2.74 g of (3-acrylamidopropyl)trimethylammonium chloride (APTC) and 1.065 g of acrylamide (AM) were placed in a round-bottom flask and mixed. After stirring at room temperature for 30 min, a uniform, clear and transparent solution was obtained. The prepared prepolymer solution was sealed and ready for use.

[0040] Material preparation: 1.37 mg of photoinitiator (I2959) was added to the prepolymer solution and magnetically stirred at 25 °C for 10 min at a stirring speed of 300 rpm to form a material precursor liquid; the well-stirred material precursor liquid was transferred to a polytetrafluoroethylene mold and placed in an ultraviolet curing machine for curing for 3 min to obtain the material.

[0041] Example 6 Preparation of prepolymer solution: 2.41g of acryloyloxyethyltrimethylammonium chloride (AETC) and 0.71g of acrylamide (AM) were placed in a round-bottom flask and mixed. After stirring at room temperature for 30 minutes, a uniform, clear and transparent solution was obtained. The prepared prepolymer solution was sealed and ready for use.

[0042] Material preparation: 1.37 mg of photoinitiator (I2959) was added to the prepolymer solution and magnetically stirred at 25 °C for 10 min at a stirring speed of 300 rpm to form a material precursor liquid; the well-stirred material precursor liquid was transferred to a polytetrafluoroethylene mold and placed in an ultraviolet curing machine for curing for 3 min to obtain the material.

[0043] Example 7 Preparation of prepolymer solution: 2.67g of dimethyl diallyl ammonium chloride (DMDAAC) and 0.71g of acrylamide (AM) were placed in a round-bottom flask and mixed. After stirring at room temperature for 30 minutes, a uniform, clear and transparent solution was obtained. The prepared prepolymer solution was sealed and ready for use.

[0044] Material preparation: 1.37 mg of photoinitiator (I2959) was added to the prepolymer solution and magnetically stirred at 25 °C for 10 min at a stirring speed of 300 rpm to form a material precursor liquid; the well-stirred material precursor liquid was transferred to a polytetrafluoroethylene mold and placed in an ultraviolet curing machine for curing for 3 min to obtain the material.

[0045] Example 8 Preparation of prepolymer solution: 2.74 g of (3-acrylamidopropyl)trimethylammonium chloride (APTC) and 0.72 g of acrylic acid (AA) were placed in a round-bottom flask and mixed. After stirring at room temperature for 30 min, a uniform, clear and transparent solution was obtained. The prepared prepolymer solution was sealed and ready for use.

[0046] Material preparation: 1.37 mg of photoinitiator (I2959) was added to the prepolymer solution and magnetically stirred at 25 °C for 10 min at a stirring speed of 300 rpm to form a material precursor liquid; the well-stirred material precursor liquid was transferred to a polytetrafluoroethylene mold and placed in an ultraviolet curing machine for curing for 3 min to obtain the material.

[0047] Example 9 Preparation of prepolymer solution: 2.74 g of (3-acrylamidopropyl)trimethylammonium chloride (APTC) and 1.30 g of carboxyethyl methacrylate (HEMA) were placed in a round-bottom flask and mixed. After stirring at room temperature for 30 min, a uniform, clear and transparent solution was obtained. The prepared prepolymer solution was sealed and ready for use.

[0048] Material preparation: 1.37 mg of photoinitiator (I2959) was added to the prepolymer solution and magnetically stirred at 25 °C for 10 min at a stirring speed of 300 rpm to form a material precursor liquid; the well-stirred material precursor liquid was transferred to a polytetrafluoroethylene mold and placed in an ultraviolet curing machine for curing for 3 min to obtain the material.

[0049] The properties of the materials prepared in Examples 1-9 were tested: (1) Ultraviolet-visible absorption (UV-vis) test: The prepared sample was subjected to spectral testing using an ultraviolet spectrophotometer (UV-1800PC) to detect the light transmittance of the material.

[0050] (2) Mechanical property testing: Mechanical tests were conducted on various material samples using a texture analyzer (TA.XTC-18) with a tensile rate of 1 mm / s. The samples were made into dumbbell shapes with a total length of 5 cm, an outer width of 8 mm, a narrow section length of 1.5 cm, a width of 4 mm, and a thickness of approximately 2 mm. All tests were repeated three times, and the average value was calculated.

[0051] (3) Thermogravimetric analysis: Thermogravimetric analysis was performed using a thermogravimetric analyzer (TG209F1) to evaluate the thermal stability of the material under a nitrogen atmosphere. Samples of 5 to 10 mg were tested at a heating rate of 20 °C / min.

[0052] (4) XPS photoelectron spectroscopy analysis: The material structure of the sample was analyzed using an X-ray photoelectron spectroscopy system (ESCALAB 250Xi).

[0053] The mechanical properties of the material prepared by this invention, as shown in the table below, are obtained through mechanical testing: Table 1 Mechanical properties of APTC-AM materials prepared in Examples 1-5 at 40% humidity

[0054] Table 1 shows the mechanical properties of the APTC-AM materials prepared in Examples 1-5 at 40% humidity. Figure 1 a is a graph showing the stress-strain curve trend of the materials prepared with increasing acrylamide content in Examples 1-5 of this invention (25℃, 40%RH). (From Table 1 and...) Figure 1 As can be seen, as the AM content increases from 1:0.5 to 1:1.5, the tensile stress at fracture increases from 1.16 MPa to 15.47 MPa, while the elongation at fracture decreases from 3050% strain to 530% strain. This inverse correlation occurs because higher AM incorporation reduces the overall water content and increases the density of hydrogen bonds in the network, effectively creating a denser polymer network. However, this results in a stronger but less ductile material. In other words, a high AM ratio results in higher stiffness and lower elongation. Conversely, a lower AM content leaves more free water / plasticizer in the gel, achieving extremely high tensile strength at the expense of strength. Examples 4 and 5 demonstrate classic plastic deformation behavior with a defined yield point, indicating that ambient humidity plays a significant role in regulating mechanics.

[0055] Table 2 Mechanical properties of APTC-AM materials prepared in Examples 1-5 at 50% humidity

[0056] Table 2 shows the mechanical properties of the APTC-AM materials prepared in Examples 1-5 at 50% humidity, and at 25℃ and 50% RH ( Figure 1 Under the conditions of b), neither Example 1 nor Example 2 can maintain stress well under both conditions, due to chain slippage caused by low dynamic crosslinking and entanglement.

[0057] Table 3 Mechanical properties of APTC1-AM1 material prepared in Example 3 under different humidity conditions

[0058] Table 3 shows the mechanical properties of the APTC-AM materials prepared in Examples 1-5 under different humidity levels. Combined with the APTC1-AM1 material (intermediate AM content) in Example 3, the mechanical properties were measured at all tested humidity levels (40-60% RH). Figure 1 c) Maintaining elastic-dominant stress-strain behavior. This indicates that the APTC1-AM1 material in Example 3 achieved an optimal balance, exhibiting a tensile strength of 5.15 MPa and an elongation at break of 1251% at 40% RH, and a tensile strength of 0.50 MPa and an elongation at break of 3130% at 60% RH. This is due to its sufficiently high dynamic crosslinking density, which provides strength without becoming brittle at lower RH levels. This suggests that excessive AM (e.g., a 1:1.5 ratio) leads to brittleness, making the network too rigid and prone to breakage at low strain; while insufficient AM results in an overly soft gel with poor strength. Therefore, the APTC1-AM1 material is the optimal choice.

[0059] Table 4 Mechanical properties of the materials prepared in Examples 3 and 6-9 at 50% humidity.

[0060] Table 4 shows the mechanical properties of materials copolymerized with different hydrophilic monomers and polymer monomers containing quaternary ammonium cationic groups at a 1:1 molar ratio, under 50% humidity. First, the polymer monomer containing quaternary ammonium cationic groups, APTC, was changed, and materials were formed by copolymerizing AETC or DMDAAC with AM. In Example 6, the elongation at break of the AETC1-AM1 material reached 2340%, but its strength was only 1.34 MPa. In Example 7, the elongation at break of the DMDAAC1-AM1 material reached 4040%, but its strength was only 0.15 MPa. The overall mechanical properties of both were inferior to the material formed by copolymerizing APTC and AM in Example 3 of this invention. However, by changing the hydrophilic monomer AM, materials were formed by copolymerizing AA or HEMA with APTC. In Example 8, APTC1-AA1 had an elongation at break of 1403% and a strength of 0.21 MPa. In Example 9, APTC1-HEMA1 had an elongation at break of 675% and a strength of 0.24 MPa. It can be seen that the overall mechanical properties of the materials in these two examples were inferior to the material formed by copolymerizing APTC and AM in Example 3 of this invention. Therefore, in Embodiment 3 of the present invention, the APTC1-AM1 material was selected for further application.

[0061] In Example 3, the APTC1-AM1 material also exhibited good elastic recovery and fatigue resistance. At 25°C and 50%RH, the dissipated energy increased with increasing strain. Figure 1 d), indicating energy absorption during deformation. Cyclic tensile test at 25℃ and 50%RH ( Figure 1 e) indicates that after a 20% decrease in initial stress during the first cycle (common for viscoelastic materials), the stress-strain response stabilizes, with a variation of <5% in subsequent cycles. Even after 50 compression cycles to 50% strain ( Figure 1 f), the material retains >95% of its initial stress, confirming minimal permanent deformation. This phenomenon demonstrates excellent fatigue resistance and structural integrity under repeated stress.

[0062] Adhesion to different substrates is another important characteristic of sensor integration, as demonstrated by tensile-shear tests. Figure 1 g) shows that the APTC1-AM1 material in Example 3 exhibits strong adhesion to a variety of materials, from metals to plastics. For example, the shear bond strength of aluminum reaches 1.0 ± 0.1 MPa, significantly exceeding that of rubber (0.15 MPa) or polytetrafluoroethylene (0.1 MPa). Figure 1 h). The specific experimental procedure is as follows: Figure 1 As shown in i, this strong adhesion is attributed to the large number of hydrogen bonds and polar groups in APTC-AM, which can interact with a variety of substrates. The excellent adhesion ensures that the APTC-AM-based sensor can be firmly attached to the robot's finger or human skin without delamination during movement.

[0063] Figure 2 The spectrum shows the dominant signals of C, N, O, and Cl, consistent with the included acrylamide (rich in C, N, and O) and APTC fragments (the source of Cl). High-resolution XPS scanning provides evidence of the surface chemical composition of the network. Cl s spectra ( Figure 2 b) The peaks are 284.8 eV (CC), 286.4 eV (Cn), and 288.1 eV (C=O), indicating the presence of a carbon chain and a polar amide / carbonyl group. N 1s spectrum ( Figure 2 c) There are two peaks at 398.8 eV (NH) and 401.7 eV (NC), while O 1s ( Figure 2 d) A strong peak at 531.7 eV is attributed to the C=O group, confirming the functional group of the amide. Simultaneously, the Cl 2p heavy state (198.0 / 199.4 eV) shows a strong peak. Figure 2 e) The presence of chloride ions in APTC was confirmed. These polar groups (NH, C=O) can form intermolecular hydrogen bonds and ionic bonds, which is the basis for the dynamic crosslinking in APTC-AM. The APTC1-AM1 material in Example 3 exhibited excellent mechanical properties and outstanding transparency (92% at wavelengths from 400 to 800 nm). Figure 2 f), making it suitable for applications requiring durability and optical clarity.

[0064] Figure 3 a shows that in Example 3 of this invention, the APTC1-AM1 material remains rigid under dry environmental conditions (25°C, 30%RH). Due to strong hydrogen bonds locking the polymer chains in place, the material maintains a flat structure. When heated to 50°C, the material softens and bends downwards. Figure 3 The sample in sample a, once softened, sagged noticeably under its own weight. Upon cooling back to 25°C, the material rapidly hardened and returned to its original flat shape within 10 ± 3 seconds. This rapid and completely reversible shape change phenomenon demonstrates a thermal shape memory cycle: heating triggers temporary shape deformation, which is repaired or restored to its original shape upon cooling. Figure 3As shown in b, the material from Example 3 was first heated to 50°C to soften it, and then manually deformed into a coiled (spiral) shape. While maintaining this shape, the strip was cooled to room temperature (25°C) for 3 minutes, "freezing" the temporary shape. After the external force was removed, the gel retained the spiral structure, indicating that the temporary shape was successfully fixed by the re-cured hydrogen bond network. The sample maintained this coiled state until reheating, and the spiral quickly unwound and recovered its original straight shape within 10 seconds. This rapid recovery of the permanent shape confirms the material's excellent shape memory performance. This heat-deformation-cooling-heat cycle was repeated 10 times, and in each test, it completely recovered to a straight state without loss of recovery speed and fidelity, always within 10 seconds. This repeatable shape memory behavior stems from the reversibility of the cross-linked network: at high temperatures, hydrogen bonds temporarily break, allowing the material to reconfigure, while at lower temperatures, hydrogen bonds reform, locking in a new shape or restoring the old shape. In this process, the balance between bond strength and mobility is crucial. In its intact state, a hydrogen bond is strong enough to maintain a given shape, yet unstable enough to dissociate under moderate heating, thus imparting ductility. This dynamic thermal response behavior is ideal for adaptive wearable devices that need to change shape or stiffness in response to body temperature or applied thermal stimuli.

[0065] Figure 4 a and Figure 4 Section b shows that the APTC1-AM1 material in Example 3 was evaluated as a piezoresistive strain sensor in an environment due to its superior mechanical flexibility and resilience. Under laboratory conditions (25°C, 50%RH), the relative resistance change (ΔR / R0) was measured over a wide strain range (10-300%) to evaluate its piezoresistive behavior. ΔR / R0 increased from 13.8% at 10% strain to 738.3% at 300% strain, exhibiting a non-linear but consistent behavior. Therefore, ΔR / R0 maintained significant consistency across various strain levels during repeated stretching and release cycles, indicating stable strain sensitivity.

[0066] like Figure 5 As shown in a-5c, the APTC1-AM1 material in Example 3 can efficiently serve as a wearable sensor for human joints, accurately monitoring human movement and precisely detecting both subtle movements (e.g., finger bending) and large deformations (e.g., elbow bending). In multiple consecutive cycles, the material in Example 3 exhibits high repeatability and reliable signal output in the ΔR / R0 ratio. Therefore, this material has great application potential in the field of wearable flexible sensors and can be used to monitor various complex human movements. Figure 5As shown in Figure d, the real-time resistance change of the material during the cutting and healing cycle is displayed. When the material is cut, its resistance increases to infinity. When the broken materials are manually glued back together, the resistance returns to its original value in a very short time.

[0067] like Figure 6 As shown in Figure a, the resistance of the APTC1-AM1 material in Example 3 was measured as a function of ambient humidity to evaluate its sensing performance. Experiments showed that the resistance decreased exponentially with increasing relative humidity. In the dry to moderate humidity range (30-60%RH), the resistivity of the material decreased sharply, achieving a linear fit within this range, with an effective sensitivity of approximately -300% / %RH (R²=0.997). This indicates that for every 1% increase in humidity, the resistance decreases by approximately 300%, demonstrating its very high sensitivity. At higher humidity levels (60-80%RH, second linear region S2), the response slope decreases as the material approaches saturation. The ultra-high sensitivity at 40-60%RH is particularly suitable for applications such as skin humidity sensing and indoor environmental monitoring. Figure 6 Figure b shows the absorption-desorption kinetics of the material during rapid humidity changes. As can be seen from the figure, the APTC-AM network can quickly capture and release moisture. When exposed to 75% RH, the moisture content reaches equilibrium in a short time. When switching back to a dry atmosphere, the material quickly loses the absorbed moisture. This rapid adsorption kinetic performance is crucial for the sensor's responsiveness, ensuring that the device can track sudden humidity changes in real time. Figure 6 Table c shows the adsorption and desorption efficiencies after 10 cycles over 20 days, indicating that its humidity response has not fatigued or degraded. In multiple tests, the dynamic response of the resistance during each humidity switching period (…) Figure 6 d) The consistent, rapid response and recovery, combined with stable cycling, indicate that the material can reliably function as a humidity sensor under realistic conditions, even with continuous humidity fluctuations.

[0068] like Figure 7 As shown in Figure a, based on its ultra-high humidity sensitivity, the APTC1-AM1 material in Embodiment 3 of this invention can be used for non-contact sensing and wearable real-time respiratory monitoring. When a finger is repeatedly placed 5mm above the sensor surface, the sensor produces a clear response: the resistance decreases as the finger approaches, and increases when the finger is removed. This phenomenon occurs because human skin constantly emits tiny halos of moisture; the closer the finger is, the greater the local humidity increase, which the sensor immediately records. Non-contact humidity sensing capabilities enable non-contact human-machine interfaces, such as gesture control devices or proximity-activated wearable devices. Human respiration contains a large amount of water vapor, and monitoring respiratory patterns (frequency, depth, apnea events) is crucial for health diagnosis.

[0069] The sensor of this invention can detect respiration without the need for nasal intubation or direct contact with the airway. It only requires measuring changes in humidity outside the nose or mouth, and monitoring respiration through the nasal cavity. Figure 7 b) and oral cavity Figure 7 c) The airflow was observed to show a sharp change in electrical resistance during exhalation. Compared with nasal breathing, oral breathing caused more significant changes in electrical signals because the exhaled oral air carries more moisture. This ability to distinguish breathing patterns may help diagnose problems related to oral breathing during sleep.

[0070] Abnormal breathing events can also be detected using humidity sensors. A prototype sensor mounted on a face mask was tested. Figure 7 d) Used for continuous respiratory tracking. During exhalation, the relative humidity around the sensor increases, causing the resistance to drop immediately. During inhalation, as the ambient relative humidity decreases, the sensor's resistance increases, and these resistance oscillations faithfully correspond to the respiratory cycle. Therefore, respiratory rate and depth can be determined by analyzing the frequency and amplitude of these peaks, such as... Figure 7 As shown in e, when the test subject breathes at both fast and slow paces, the measured respiratory rate accurately matches the actual respiratory rate. When the subject stops breathing to simulate apnea, a rapidly rising electrical curve is observed, indicating the presence of sleep apnea. Figure 7 f). Because the sensor is non-contact, it avoids the problem of skin irritation or pressure, making it suitable for continuous nighttime monitoring. The platform demonstrated in this invention is a thin film integrated into a breathable mask, highlighting the potential of the material in telemedicine and wearable health. It can continuously record breathing patterns to help diagnose sleep apnea or chronic respiratory diseases, and even trigger alarms or interventions when dangerous apnea events are detected.

[0071] like Figure 8 As shown in Figure a, an AI-driven material recognition system is built around the TENG sensor. The sensor is mounted on the finger of an intelligent robot for lightly touching materials. The voltage signal is acquired by a microcontroller and sent to a computer, where the waveform data is processed by a 1D convolutional neural network algorithm and displayed in real time using a graphical user interface. In practical applications, only the wiring needs to be connected to the intelligent device chip, which enhances system integration. The triboelectric signal exhibits biphasic characteristics (peak I: contact; peak II: separation). Figure 8 As shown in Figure b, the hotspots (red spots) indicate the areas where the CNN extracts feature information. The red areas form around peaks I and II, indicating that the waveform generated by the tactile sensor made from the flexible material of this invention has unique characteristics. Based on these results, it is demonstrated that combining the output TENG signal with CNN technology enables the prefabricated tactile sensor to recognize different materials. Figure 8After training, the AI ​​system based on the tactile APTC1-AM1 triboelectric nanogenerator achieved a material recognition accuracy of 99.2%. Figure 8 c). Therefore, by performing CNN feature extraction on the TENG signal and corresponding recognition, excellent material identification accuracy was successfully achieved.

[0072] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A dynamic hydrogen bond / ion network multimodal sensing flexible material, characterized in that, It consists of a polymer network formed by copolymerization of hydrophilic monomers and polymer monomers containing quaternary ammonium cationic groups. It forms a dynamic cross-linked structure through reversible hydrogen bonding and ionic interactions. It can reversibly switch between a rigid plastic state and a flexible elastic state with changes in relative humidity, thereby achieving stiffness switching for humidity regulation.

2. The dynamic hydrogen bond / ion network multimodal sensing flexible material according to claim 1, characterized in that, The hydrophilic monomers include, but are not limited to, one of acrylamide, acrylic acid, and carboxyethyl methacrylate.

3. The dynamic hydrogen bond / ion network multimodal sensing flexible material according to claim 1, characterized in that, The polymer monomers containing quaternary ammonium cationic groups include, but are not limited to, one of (3-acrylamidopropyl)trimethylammonium chloride, acryloyloxyethyltrimethylammonium chloride, and dimethyldiallylammonium chloride.

4. A method for preparing a dynamic hydrogen bond / ion network multimodal sensing flexible material as described in any one of claims 1-3, characterized in that, The preparation method is photoinitiated free radical polymerization, and the specific steps are as follows: S1: Mix the polymer monomer containing quaternary ammonium cationic groups and the hydrophilic monomer at room temperature to form a transparent solution A; S2: Add photoinitiator I2959 to transparent solution A, stir again for 10 min to form precursor solution B; S3: Pour the obtained precursor solution B into a polytetrafluoroethylene mold and place it under 365nm ultraviolet light irradiation. After 3 minutes of curing treatment, the flexible material is obtained.

5. The method for preparing the dynamic hydrogen bond / ion network multimodal sensing flexible material as described in claim 3, characterized in that, In step S1, the molar ratio of the polymer monomer containing quaternary ammonium cationic groups to the hydrophilic monomer is 1:0.5-1.

5.

6. The method for preparing the dynamic hydrogen bond / ion network multimodal sensing flexible material as described in claim 3, characterized in that, In step S2, the mass ratio of photoinitiator I2959 to polymer monomers containing quaternary ammonium cationic groups is 1:2000.

7. The method for preparing the dynamic hydrogen bond / ion network multimodal sensing flexible material as described in claim 3, characterized in that, In step S2, when preparing the material precursor solution, the stirring temperature is 25-30℃ and the stirring speed is 300-400rpm.

8. The method for preparing the dynamic hydrogen bond / ion network multimodal sensing flexible material as described in claim 3, characterized in that, In step S3, the temperature of the photocuring crosslinking reaction is 25-30℃, and the curing time is 3 minutes.

9. A flexible humidity sensor, characterized in that, The layer is prepared using the flexible sensing material as described in any one of claims 1-3 as the humidity-sensitive layer. The humidity-sensitive layer exhibits a change in resistance value in response to changes in ambient relative humidity and has a humidity sensitivity of −300% / %RH within a relative humidity range of 30-60%.

10. A triboelectric tactile sensor, characterized in that, The sensor is prepared using the flexible sensing material as described in any one of claims 1-3 as the positive electrode friction layer. The positive electrode friction layer repeatedly contacts and separates from another negative electrode material to generate characteristic electrical signals. By performing pattern recognition on the electrical signals, different touched objects can be distinguished. The sensor has an accuracy rate of >99% in recognizing different materials.

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