TPU film for robot electronic skin and preparation method thereof

Abstract

The invention discloses a TPU film for robot electronic skin and a preparation method of the TPU film, and relates to the technical field of flexible electronic materials, the film takes TPU introduced with Diels-Alder dynamic reversible bonds as a matrix, a conductive filler is formed by dopamine-modified silver nanowires and MXene, the concentration of the conductive filler is in continuous or quasi-continuous gradient decrease, and the conductive filler is a conductive filler formed by silver nanowires and MXene. An integrated network with self-repairing and environmental stability is formed and is used as an electrode; phase change microcapsules and triboelectric nanofibers are compounded in a low-conductivity contact area to form an intelligent response layer which is self-adaptive in sensing threshold and capable of generating power by friction. Through one-step multi-nozzle electrostatic spinning forming, the problem that self-repairing, signal stability, environmental adaptability and energy independence in electronic skin are difficult to consider at the same time is solved.

Description

Technical Field

[0001] This invention relates to the field of flexible electronic materials technology, specifically a TPU film for robotic electronic skin and its preparation method. Background Technology

[0002] With the deepening application of robotics technology in fields such as intelligent manufacturing, medical rehabilitation, and special services, the demand for high-precision and high-reliability environmental perception is becoming increasingly urgent. As the "sensory" surface of robots, electronic skin is expected to simulate or even surpass some functions of human skin, namely, flexibility, stretchability, self-repair capabilities, sensitive perception of various physical signals (such as pressure and strain), and stable operation in complex environments.

[0003] Currently, most mainstream electronic skin technologies employ a strategy of blending conductive fillers (such as carbon nanotubes and silver nanowires) with elastomers (such as silicone rubber and TPU). However, this type of technology generally suffers from the following bottlenecks: Single function and performance imbalance: Most studies focus on improving a single performance (such as sensitivity), making it difficult to simultaneously achieve self-healing, high tensile strength, signal stability and environmental adaptability.

[0004] Low self-healing efficiency: Existing self-healing electronic skins mostly rely on hydrogen bonds or ionic bonds. Their self-healing process often requires external stimulation (such as heating or light exposure), and the recovery rate of conductivity after repair is usually not ideal (<80%), and the recovery of mechanical properties is slow.

[0005] Insufficient structural reliability: There are obvious physical interfaces between functional layers prepared by multilayer coating or transfer printing processes. Under repeated deformation, delamination and peeling are likely to occur, leading to device failure.

[0006] Significant environmental interference: Humidity and temperature changes can significantly affect the dielectric constant and volume of materials, causing sensor signal drift and a sharp drop in reliability in humid or alternating high and low temperature environments.

[0007] High energy dependence: The sensors require a continuous external power supply, which limits the robot's autonomy and endurance.

[0008] Therefore, developing a novel electronic skin material and preparation method that can systematically solve the above problems and achieve integrated multiple superior properties has become a technical challenge that urgently needs to be overcome in this field. Summary of the Invention

[0009] This invention provides a TPU film for robotic electronic skin and its preparation method to solve the above-mentioned problems.

[0010] One of the core innovations of this invention lies in the synergistic process of the dual self-healing system: when the film is damaged, the hydrogen bonds and metal coordination bonds between AgNWs@PDA and the TPU matrix can undergo rapid and reversible reconstruction at room temperature, achieving preliminary physical repair and partial connection of conductive pathways, restoring the basic morphology and some electrical properties; subsequently, at a repair temperature of 60-80℃, the Diels-Alder covalent bonds reversibly open, and the molecular chain segments gain sufficient mobility for recombination, achieving complete repair of the covalent network, thereby restoring the mechanical strength and the complete conductive network to near its initial state. This multi-level repair mechanism of "physical bonds first, covalent bonds last" is the key to achieving high repair efficiency.

[0011] Another core innovation of this invention lies in the collaborative relationship between the various functional components: Synergy between intelligent response and power generation: The highly conductive region in the gradient conductive network also serves as the electrode of the triboelectric nanostructure, which is used to collect the charge generated when the triboelectric fiber comes into contact with and separates from an external object, thus realizing the integration of "structure-sensing-power generation".

[0012] Synergy between environmental stability and intelligent response: The MXene sheets not only enhance the conductive network, but their unique two-dimensional sheet structure also effectively improves the overall moisture barrier performance of the film, significantly reducing the erosion of phase change microcapsules and internal conductive networks by environmental moisture, and ensuring the stability of the adaptive function in humid environments.

[0013] Synergy of energy and control: The electrical energy generated by triboelectric power generation can be connected to and drive a micro-resistance heater integrated on a thin film to actively and precisely control the temperature of the local phase change microcapsules, thereby adjusting their modulus state and forming a local closed-loop system from energy harvesting to functional regulation.

[0014] Specifically, the present invention provides the following technical solution: A TPU film for robotic electronic skin, wherein the film is an integrated three-dimensional fiber film formed by electrospinning technology, and the conductive filler inside is a mixture of dopamine-modified silver nanowires and MXene. The concentration of the mixture is continuously or quasi-continuously decreasing from one side of the main surface of the film to the opposite side of the main surface, forming a gradient conductive network. The film substrate is a TPU with a Diels-Alder dynamic reversible crosslinking network, and the dopamine-modified silver nanowires are dispersed in the substrate. A physical self-healing system composed of hydrogen bonds and metal coordination bonds is formed between the substrate and the dopamine-modified silver nanowires, which together with the Diels-Alder dynamic reversible covalent bonds constitute a dual self-healing mechanism; the film includes at least: A highly conductive functional region comprising the conductive filler dispersed in the substrate, constituting an electrode of the thin film; A low-conductivity contact functional region is seamlessly connected to the high-conductivity functional region by interwoven fibers, and phase change microcapsules and triboelectric nanofibers are composited in the contact functional region. The highly conductive functional region and the contact functional region together constitute a triboelectric nanogenerator structure, and the gradient conductive network serves as the common electrode of this structure.

[0015] Preferably, the TPU matrix with the Diels-Alder dynamic reversible crosslinking network is prepared by the following method: using polycaprolactone diol as the soft segment, 4,4'-dicyclohexylmethane diisocyanate as the hard segment, 2-(2-furanylethylamine) as the chain extender to introduce furan groups, and bismaleimide as the crosslinking agent, and reacting at 70-85°C for 2-4 hours; wherein, the molar ratio of polycaprolactone diol, 4,4'-dicyclohexylmethane diisocyanate, 2-(2-furanylethylamine) to bismaleimide is 1:2.5-3.0:0.8-1.0:0.1-0.2.

[0016] Preferably, the dopamine-modified silver nanowires are prepared by the following method: dispersing silver nanowires in a Tris-HCl buffer solution with a concentration of 5-15 mg / mL, adjusting the pH to 8.5, adding dopamine hydrochloride at a mass ratio of 1:1-3 to the silver nanowires, stirring at 20-30°C for 10-14 hours, and obtaining the nanowires after centrifugation and washing; the mass percentage of the dopamine-modified silver nanowires in the highly conductive functional region of the film is 10%-20% of the DA-TPU matrix.

[0017] Preferably, the MXene is a few-layer Ti3C2T x Its mass percentage in the highly conductive functional region of the thin film is 1%-5% of that of the DA-TPU matrix.

[0018] Preferably, the shell material of the phase change microcapsule is polyurethane or melamine resin, and the core material is a low-melting-point alloy or phase change polymer with a melting point between 45-70℃, and its mass percentage in the film contact functional area is 5%-15% of the DA-TPU matrix.

[0019] Preferably, the phase change microcapsules are prepared by the following method: using in-situ polymerization, a low melting point alloy is melted at a temperature 5-10°C above its melting point, and then emulsified with an aqueous solution containing 1-5 wt% emulsifier at a high-speed shearing speed of 8000-12000 rpm for 5-15 minutes to form an O / W emulsion; subsequently, a shell prepolymer and a chain extender are added to the emulsion, and the mixture is reacted at 50-70°C for 3-5 hours. After the reaction is completed, the mixture is filtered, washed, and dried to obtain core-shell structured phase change microcapsule powder.

[0020] Preferably, the triboelectric nanofibers are polytetrafluoroethylene or nylon 6,6 fibers with an average fiber diameter of 100-500 nm and an aspect ratio greater than 50. Their mass percentage in the contact functional area of ​​the film is 3%-10% of the DA-TPU matrix.

[0021] The present invention also provides a method for preparing the above-mentioned TPU film, characterized by comprising the following steps: S1: Preparation of TPU matrix with Diels-Alder dynamic reversible crosslinking network; S2: Preparation of dopamine-modified silver nanowires; S3: Preparation of an organic solvent dispersion of MXene; S4: Preparation of electrospinning sizing agent: S41: Conductive layer slurry: Dissolve the DA-TPU obtained in S1 in a DMF / THF mixed solvent to prepare a solution with a mass-volume concentration of 15%-25%, then add the dopamine-modified silver nanowires obtained in S2 and the MXene dispersion obtained in S3 in sequence, and disperse them evenly by ultrasonication. S42: Insulation / Transition Layer Paste: Dissolve the DA-TPU obtained in S1 in a DMF / THF mixed solvent to prepare a solution with a mass-volume concentration of 15%-25%; S43: Intelligent contact outer layer slurry: Dissolve the DA-TPU obtained in S1 in a DMF / THF mixed solvent to prepare a solution with a mass-volume concentration of 15%-25%, and add phase change microcapsules and triboelectric nanofibers, and ultrasonically disperse them evenly; S5: Using a multi-nozzle electrospinning device, at least two of the slurries obtained from S41, S42 and S43 are spatially oriented and spun synchronously according to a preset functional gradient structure, and a fiber membrane with a gradient conductive network structure is collected on a receiving device. S6: The collected fiber membrane is heat-treated at 65-75°C for 1-3 hours to obtain the electronic skin film.

[0022] Preferably, in step S5, the morphology of the gradient structure is controlled by independently adjusting the propulsion speed of each functional layer slurry, wherein the propulsion speed of the conductive layer slurry is 1.5-3.0 times that of the propulsion speed of the contact functional area slurry.

[0023] Preferably, the electrospinning process parameters in step S5 are as follows: spinning voltage is 12-20kV, receiving distance is 10-20cm, slurry feed speed is 0.3-1.0mL / h, ambient temperature is controlled at 20-30℃, and ambient humidity is controlled below 30%.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention constructs a TPU matrix with a Diels-Alder dynamic reversible crosslinking network, endowing the material with excellent self-healing ability and thermal responsiveness. Combined with a gradient conductive network synergistically constructed from dopamine-modified silver nanowires and MXene, the sensitivity and cycling stability of the electronic skin are significantly improved. Phase change microcapsules are introduced to achieve temperature buffering and energy regulation functions, while triboelectric nanofibers enhance the surface charge trapping ability, further improving the sensing signal-to-noise ratio. Multi-nozzle electrospinning technology is used to achieve spatial orientation distribution of functional components, enabling the film to maintain high flexibility while possessing regional response characteristics, meeting the multimodal sensing needs in complex environments.

[0025] The electronic skin film described in this invention can dynamically reconstruct itself by triggering the Diels-Alder reverse reaction at 60-80℃ after mechanical damage, with a repair efficiency of over 90%. Dopamine modification effectively enhances the interfacial compatibility between silver nanowires and MXene in the DA-TPU matrix, inhibits aggregation, and keeps the conductive network stable during repeated stretching and releasing. Phase change microcapsules undergo solid-liquid transition near body temperature, absorbing or releasing heat, improving wearability and environmental adaptability. Triboelectric nanofibers, through surface functionalization design, significantly improve the contact electrification effect, enabling the device to have high response speed and detection accuracy to minute pressure, bending, and frictional movements.

[0026] 3. This invention employs multi-nozzle electrospinning technology to achieve precise construction of functionally graded structures. By independently controlling the slurry propulsion speed of each nozzle, the conductive layer and contact functional areas are spatially distributed in a gradual manner, effectively reducing interfacial stress concentration and improving overall mechanical stability. During the heat treatment process at 65-75℃, the DA-TPU matrix undergoes moderate cross-linking, further enhancing the structural integrity and thermal response reversibility of the fiber membrane, ensuring the electronic skin maintains stable performance during long-term use. Furthermore, this fabrication process eliminates the need for complex photolithography or etching steps, making it environmentally friendly and suitable for mass production. The resulting electronic skin can be integrated into flexible wearable devices and applied in health monitoring, human-computer interaction, and intelligent robotics, demonstrating broad application prospects. Attached Figure Description

[0027] Figure 1 This invention provides a flowchart of a method for preparing a TPU film for robotic electronic skin.

[0028] Figure 2 This is a scanning electron microscope (SEM) image of the thin film in Example 4. Detailed Implementation

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0030] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0031] Example 1: Synthesis of DA-TPU matrix Under dry nitrogen protection, 100 g of polycaprolactone diol (PCL2000) was added to a 500 mL three-necked flask equipped with a stirrer, thermometer, and condenser, and the mixture was heated to 60 °C to melt it. Then, 39.4 g of 4,4'-dicyclohexylmethane diisocyanate (HMDI) and 0.05 g of dibutyltin dilaurate catalyst were added, and the reaction was carried out at 80 °C for 2 hours to obtain an -NCO-terminated prepolymer. The system was cooled to 50 °C, and 6.8 g of 2-(2-furanylethylamine) (usually used in its hydrochloride form, dissolved in 30 mL of anhydrous DMF) was added, and the reaction was carried out for 1 hour. Subsequently, 3.48 g of 1,1'-(methylenedi-4,1-phenylene)bismaleimide (dissolved in 20 mL of anhydrous DMF) was added, and the reaction was continued at 80 °C for 2 hours. After the reaction was completed, the product was poured into a polytetrafluoroethylene mold and aged in a vacuum drying oven at 80°C for 12 hours to obtain a light yellow, tough and elastic DA-TPU solid, which was then sealed and stored for later use.

[0032] Example 2: Preparation of AgNWs@PDA and MXene dispersion Preparation of AgNWs@PDA: 100 mg of silver nanowires (diameter ~80 nm, length ~20 μm) were dispersed in 100 mL of Tris-HCl buffer (10 mg / mL) at pH 8.5 and sonicated for 30 minutes; 150 mg of dopamine hydrochloride was added and the mixture was magnetically stirred at 25 °C in the dark for 12 hours; the precipitate was collected by centrifugation (8000 rpm, 10 min), washed three times each with deionized water and ethanol, and redispersed in 50 mL of DMF to obtain a DMF dispersion of AgNWs@PDA (approximately 2 mg / mL).

[0033] Preparation of MXene dispersion: A LiF / HCl etching method was used. 2g of LiF was dissolved in 40mL of 9M HCl, and 2g of Ti3AlC2 powder was slowly added at 35℃, reacting for 24 hours. After the reaction, the supernatant was repeatedly washed by centrifugation with deionized water until the pH > 6. The precipitate was dispersed in 100mL of deionized water and ultrasonically exfoliated in an ice-water bath for 1 hour. Then, it was centrifuged (3500rpm, 30min) to collect the upper black colloidal solution, which was the few-layer MXene aqueous dispersion. 50mL of this aqueous dispersion was taken and, under a vacuum of -0.08MPa to -0.1MPa, replaced with DMF solvent by vacuum filtration. This process was repeated three times, and the final volume was adjusted to 50mL to obtain a stable and homogeneous few-layer MXene DMF dispersion (approximately 1mg / mL).

[0034] Example 3: Preparation of phase change microcapsules In-situ polymerization was employed. 10g of Field's metal (bismuth-indium-tin eutectic alloy) with a melting point of 62℃ was melted at 70℃ and mixed with 100mL of deionized water containing 2g of gum arabic. The mixture was emulsified under high-speed shear at 10000 rpm for 10 minutes to form a stable O / W emulsion. The emulsion was transferred to a three-necked flask, and 5g of prepolymer (composed of an adduct of toluene-2,4-diisocyanate and trimethylolpropane) and 1g of ethylenediamine were slowly added as chain extenders. The reaction was carried out at 60℃ for 4 hours. After the reaction, the mixture was filtered, washed with deionized water and ethanol, and dried in a vacuum drying oven at 50℃ for 12 hours to obtain phase change microcapsule powder with an intact core-shell structure and a smooth surface.

[0035] Example 4: Preparation of electronic skin film This embodiment represents a preferred method for preparing a fully functional thin film, directly using two pastes—the conductive layer and the smart contact outer layer—to form a distinct functional gradient. In other embodiments of the invention, an insulating / transition layer paste can be introduced between the conductive layer and the smart contact outer layer, depending on the actual sensing sensitivity requirements, to create a gradient structure with a smoother resistance change.

[0036] Slurry preparation: Conductive layer slurry: Take 5 g of the DA-TPU synthesized in Example 1 and dissolve it in 20 mL of a DMF / THF (v / v = 7:3) mixed solvent. Under stirring, add 15 mL of the AgNWs@PDA dispersion prepared in Example 2 (containing about 30 mg of AgNWs@PDA) and 10 mL of the MXene dispersion (containing about 10 mg of MXene), and then ultrasonically disperse for 1 hour until the system is homogeneous to obtain a uniform black slurry.

[0037] Intelligent contact outer layer slurry: Take 5 g of the DA-TPU synthesized in Example 1 and dissolve it in 20 mL of a DMF / THF mixed solvent. Add 0.5 g (10% of the TPU mass) of the phase change microcapsule powder prepared in Example 3 and 0.25 g (5% of the TPU mass) of PTFE nanofibers with an average fiber diameter of about 200 nm and an aspect ratio greater than 100, and ultrasonically disperse evenly.

[0038] Electrospinning: Use a three-nozzle electrospinning device. The three nozzles are arranged in a "pin" shape. Two nozzles are filled with the conductive layer slurry, and one nozzle is filled with the intelligent contact outer layer slurry. Ensure that the outer layer slurry can effectively cover outside the conductive layer fibers through spatial arrangement. Set the process parameters: the spinning voltage is +15 kV / -5 kV, the receiving distance is 15 cm, and the slurry feeding speed is 0.5 mL / h for all. Control the environmental temperature at 25 ± 2 °C and the humidity < 30%. Collect the fibers on a drum receiver covered with aluminum foil, and the spinning time is about 4 hours to obtain a flexible film with a thickness of about 100 μm.

[0039] Post-treatment: Peel the film off the aluminum foil and place it in a vacuum oven at 70 °C for heat treatment for 2 hours to obtain an electronic skin film with intelligent response function (denoted as sample A).

[0040] Observe the cross-sectional morphology of sample A by scanning electron microscopy (SEM), as Figure 2 shown. It can be seen that the TPU fibers in the highly conductive functional area and the contact functional area penetrate and intertwine with each other, forming a continuous three-dimensional network structure without visible physical interfaces. The average diameter of the TPU fibers is measured to be 800 ± 200 nm. Through statistical analysis of the SEM images, the intertwining density between fibers (defined as the number of fiber intersections per unit area) is higher than 50 per mm 2 . This fiber membrane also exhibits the characteristics of high porosity, and its porosity is calculated to be about 7%-85% by image analysis method.

[0041] Perform a water vapor transmission rate test on sample A (according to the standard ASTM E96). Under the conditions of 38 °C and 90% relative humidity, its water vapor transmission rate is 0.9 g / (m 2 ·24 h), while the water vapor transmission rate of the control sample with the same formula and structure but without MXene is 6.0 g / (m2 (24h) demonstrates that the introduction of MXene significantly improves the moisture barrier properties of the film.

[0042] Example 5 Slurry preparation Conductive layer slurry: Take 5g of DA-TPU from Example 1, dissolve it in 20mL DMF / THF (7:3), add 10mL AgNWs@PDA dispersion (containing approximately 500mg AgNWs@PDA, accounting for 10% of the TPU mass) and 50mL MXene dispersion (containing approximately 50mg MXene, accounting for 1% of the TPU mass), and ultrasonically disperse for 1 hour.

[0043] Insulating / transition layer paste: Same as S42 in Example 4 (5g DA-TPU dissolved in 20mL mixed solvent).

[0044] Intelligent contact outer layer slurry: Take 5g DA-TPU, dissolve it in 20mL mixed solvent, add 0.25g phase change microcapsules (5% of TPU mass) and 0.3g nylon 6,6 triboelectric nanofibers (6% of TPU mass), and ultrasonically disperse for 1 hour.

[0045] electrospinning Equipment: Three-nozzle electrospinning machine, with the nozzles arranged in a "linear pattern" (conductive layer - transition layer - smart contact layer).

[0046] Process parameters: spinning voltage 12kV, receiving distance 12cm, feed speed: conductive layer 0.6mL / h, transition layer 0.4mL / h, smart contact layer 0.4mL / h (the speed of the conductive layer is 1.5 times that of the contact layer), ambient temperature and humidity are the same as in Example 4.

[0047] Post-processing: Vacuum heat treatment at 70℃ for 2 hours to obtain an electronic skin film (denoted as sample B).

[0048] Example 6 Slurry preparation Conductive layer slurry: 5g DA-TPU, add 10mL AgNWs@PDA dispersion (containing approximately 1g AgNWs@PDA, accounting for 20% of TPU mass) and 100mL MXene dispersion (containing approximately 250mg MXene, accounting for 5% of TPU mass), and ultrasonically disperse for 1.5 hours (to avoid agglomeration).

[0049] Intelligent contact outer layer slurry: 5g DA-TPU, add 0.75g phase change microcapsules (15% of TPU mass) and 0.5g PTFE triboelectric nanofibers (10% of TPU mass), and ultrasonically disperse for 1.5 hours until the system is homogeneous (to avoid agglomeration of conductive fillers).

[0050] electrospinning Equipment: Dual-nozzle spinning machine (conductive layer + intelligent contact layer).

[0051] Process parameters: spinning voltage 20kV, receiving distance 20cm, feed speed: conductive layer 0.9mL / h, contact layer 0.3mL / h (the speed of the conductive layer is 3.0 times that of the contact layer).

[0052] Post-processing: Vacuum heat treatment at 75℃ for 1 hour to obtain an electronic skin film (denoted as sample C).

[0053] Comparative Example 1 In Example 4, the "dopamine-modified silver nanowires (AgNWs@PDA)" were replaced with "ordinary silver nanowires" of equal mass (diameter ~80nm, length ~20μm, without dopamine modification), and everything else was the same as in Example 4. The resulting film was designated as control sample CE1.

[0054] Comparative Example 2 The "conductive layer slurry" and "contact functional area slurry" in Example 4 were mixed at a volume ratio of 1:1 and stirred for 30 minutes until the system was uniform (forming a homogeneous conductive filler distribution). The system was then spun using a single-nozzle electrospinning device (replacing the multi-nozzle method). All other steps were the same as in Example 4. The resulting film was designated as the comparative sample CE2.

[0055] Comparative Example 3 Except for the absence of MXene, the raw materials, formulation and preparation steps were the same as in Example 4, and the resulting film was designated as control sample CE3.

[0056] Comparative Example 4 The "PTFE triboelectric nanofibers" in the "contact functional area slurry" of Example 4 were removed. The contact functional area was only pure DA-TPU slurry, and the rest was the same as in Example 4. The resulting film was designated as the comparative sample CE4.

[0057] Comparative Example 5 Only the "phase change microcapsules" in "intelligent contact outer layer slurry" of Example 4 were deleted. All other raw materials, formulations and processes were the same as in Example 4. The resulting film was designated as the comparative sample CE5.

[0058] Comparative Example 6 The difference from Example 4 is that ordinary silver nanowires (without dopamine modification) were used instead of AgNWs@PDA, MXene was missing, and the conductive filler was homogeneously mixed with the matrix (without gradient structure). All other raw materials, formulations and processes were the same as in Example 4. The resulting film was designated as comparative sample CE6.

[0059] Performance testing The samples prepared in Examples 4-6 and Comparative Examples 1-6 were subjected to systematic performance tests using the same test methods and evaluation criteria. The results are as follows: 1. Verification of gradient conductivity characteristics The surface resistivity of the high-conductivity functional region and the contact functional region of each sample was measured using a four-probe tester (model: RTS-9) and a high-resistivity meter (model: TH2512) to evaluate the uniformity of the gradient distribution. Sample A: The surface resistivity of the high-conductivity functional area is 18 Ω / sq, and the surface resistivity of the contact functional area is higher than 8 × 10⁻⁶. 7 Ω / sq, with clear functional partitioning and significant gradient characteristics; Sample B (including transition layer): The surface resistivity of the high conductivity region is 15 Ω / sq, and the resistance of the transition layer increases linearly (gradually transitioning from 15 Ω / sq to 5 × 10⁻⁶). 6 Ω / sq), contact area surface resistance 1.2×10 8 Ω / sq, to ​​verify the optimization effect of the transition layer on gradient smoothness; Sample C (high-concentration filler): surface resistivity of the high-conductivity area is as low as 8 Ω / sq, and surface resistivity of the contact area is 2 × 10⁻⁶. 7 Ω / sq, no aggregation was observed between high concentrations of AgNWs@PDA and MXene, confirming good dispersibility and gradient stability at high filler concentrations.

[0060] 2. Self-healing performance test Damage was created using the "blade scratch method" (scratch length 1cm, depth 50μm). Scratch healing was observed using an optical microscope, and the resistance recovery rate was tested using the four-probe method. The tensile strength recovery rate was tested using a tensile testing machine (model: CMT6104). Sample A (composite smart component): scratches narrowed by 80% after 24 hours at room temperature, and completely disappeared after heating at 70℃ for 30 minutes; the resistance repair efficiency was 94%, and the tensile strength recovery rate was 92%, proving that the phase change microcapsules and triboelectric fibers did not hinder the self-repair process; Sample B: After repair at room temperature for 24 hours + 70℃ for 30 minutes, the scratches disappeared, the resistance repair rate was 95%, and the tensile strength recovery rate was 93%, verifying the self-healing stability under the parameters defined in the claims. Sample C: Due to the presence of high-concentration filler, the room temperature repair speed is slightly slower (scratches narrow by 65% ​​after 24 hours), but after heating at 70℃ for 30 minutes, it still achieves a 93% resistance repair rate and a 90% tensile strength recovery rate, which meets practical requirements. Comparative Example CE1 (Physical Self-Healing): After being placed at room temperature for 24 hours, the scratch narrowed by only 40%, and after heating at 70℃ for 30 minutes, the resistive repair efficiency was 78%, which was much lower than that of Sample A (96%), proving that the synergistic effect of the dual self-healing system is crucial. Comparative Example CE6: Scratch narrowing of 5% after 24 hours at room temperature, and resistance repair rate of 68% after 30 minutes at 70℃, which is much lower than 94% of Sample A.

[0061] 3. Environmental stability test Each sample was placed in a constant temperature and humidity chamber (model: BPH-060) with conditions set at 25℃ and 90%RH. The sheet resistance was continuously monitored for 48 hours to evaluate the water vapor barrier effect of MXene. Sample A: Resistance increase of 8.0%, phase change microcapsules did not show interface delamination due to moisture; Sample B: Resistance increased by 8.2%, the presence of the transition layer did not affect the blocking performance of MXene; Sample C: High concentration of MXene further enhances the moisture barrier effect, with a resistance increase of only 6.8% after 48 hours, which is better than other samples, confirming the positive correlation between MXene concentration and environmental stability; Comparative example CE3 (MXene-deficient): After 48 hours in a 90% RH environment, the resistance increased by 40%, which is in stark contrast to sample A (7.5%), fully demonstrating the core role of MXene as an environmental stabilizer; Comparative Example CE6: 90% RH / 48h resistance increase of 45%, significantly higher than sample A's 8.0%.

[0062] 4. Sensor stability test Each sample was subjected to 1000 cycles of 50% tensile strain (tensile rate 50 mm / min), and the repeatability and drift of the resistance change curves were recorded. Sample A: Drift amount less than 4.5%, the addition of smart components did not reduce cycle stability; Sample B (including transition layer): Due to its gentler gradient, the resistance drift is only 3.8%, the lowest among all samples; Sample C (high-concentration filler): drift amount 5.0%, which is slightly higher than other samples, but still within the industrially acceptable range (<10%). Comparative Example CE2 (homogeneous structure): After 1000 cycles of 50% tensile strain, the resistance drift was as high as 15%, which was significantly higher than that of Sample A (4.2%), proving that the gradient structure can greatly improve signal stability. Comparative example CE6: drifted by 18% after 1000 cycles, with no power generation capability.

[0063] 5. Intelligent Response Performance Test The sample temperature was adjusted (25℃→65℃) using a temperature control platform, and the rate of change of the piezoresistive signal under the action of a 1g weight was tested. Durability was verified by performing 100 heating and cooling cycles. Sample A: The signal change rate was 5% at 25℃, increasing to 12% at 65℃; after 100 cycles, the signal change rate at 65℃ was still 11.5%, with an attenuation rate of only 4.2%. Sample B: Signal change rate of 4.8% at 25℃, reaching 11.7% at 65℃; after 100 cycles, it remains at 11.2%, demonstrating excellent stability; Sample C (high-concentration phase change microcapsules): The signal change rate reached 14% at 65℃, with the highest sensitivity; after 100 cycles, it still maintained 13.5%, confirming the synergistic effect of high-concentration microcapsules; Comparative example CE5 (lacking phase change microcapsules): The piezoresistive signal change rate of a 1g weight is 0.8% at 25℃ and 0.9% at 65℃. Temperature change has less than 1% effect on the signal, and there is no adaptive function.

[0064] 6. Energy Autonomy Feasibility Test A simulated real-world contact scenario was achieved using finger pressure (2Hz frequency, 5N pressure). The open-circuit voltage was tested using an oscilloscope (model: DS1104Z). After processing by a rectifier and voltage regulator circuit (including a 1N5819 Schottky diode and a 100μF tantalum capacitor), the ability to drive low-power devices was evaluated. Sample A: Open circuit voltage 3.0V, power density 0.8μW / cm² 2 After 30 seconds of energy storage, it can drive the BLE module to send data once every 60 seconds; Sample B: Open circuit voltage 2.8V, power density 0.7μW / cm² 2 Stable performance; Sample C (high-concentration triboelectric fiber): open-circuit voltage 3.5V, power density up to 1.0μW / cm² 2 After storing energy for 30 seconds, it can drive the BLE module to send data once every 45 seconds, and it can work continuously for 8 hours without performance degradation, fully verifying the potential for energy autonomy. Comparative example CE4 (missing triboelectric fiber): No open-circuit voltage output, unable to drive BLE module.

[0065] It should be noted that, for the sake of simplicity, the foregoing embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0066] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still combine, add, delete, or otherwise adjust the features of the various embodiments of the present invention according to the circumstances without conflict or creative effort, thereby obtaining different technical solutions that do not fundamentally depart from the concept of the present invention. These technical solutions also fall within the scope of protection of the present invention.

Claims

1. A TPU film for robotic electronic skin, characterized in that, The film is an integrated three-dimensional fiber film formed by electrospinning technology. Its internal conductive filler is a mixture of dopamine-modified silver nanowires and MXene. The concentration of the mixture decreases continuously or quasi-continuously from one main surface of the film to the other, forming a gradient conductive network. The film substrate is a TPU with a Diels-Alder dynamic reversible crosslinking network, and the dopamine-modified silver nanowires are dispersed in the substrate. A physical self-healing system composed of hydrogen bonds and metal coordination bonds is formed between the substrate and the dopamine-modified silver nanowires, which together with the Diels-Alder dynamic reversible covalent bonds constitute a dual self-healing mechanism; the film includes at least: A highly conductive functional region comprising the conductive filler dispersed in the substrate, constituting an electrode of the thin film; A low-conductivity contact functional region is seamlessly connected to the high-conductivity functional region by interwoven fibers, and phase change microcapsules and triboelectric nanofibers are composited in the contact functional region. The highly conductive functional region and the contact functional region together constitute a triboelectric nanogenerator structure, and the gradient conductive network serves as the common electrode of this structure.

2. The TPU film for robotic electronic skin according to claim 1, characterized in that, The TPU matrix with the Diels-Alder dynamic reversible crosslinking network is prepared by the following method: using polycaprolactone diol as the soft segment, 4,4'-dicyclohexylmethane diisocyanate as the hard segment, 2-(2-furanylethylamine) as the chain extender to introduce furan groups, and bismaleimide as the crosslinking agent, and reacting at 70-85°C for 2-4 hours; wherein, the molar ratio of polycaprolactone diol, 4,4'-dicyclohexylmethane diisocyanate, 2-(2-furanylethylamine) to bismaleimide is 1:2.5-3.0:0.8-1.0:0.1-0.

2.

3. The TPU film for robotic electronic skin according to claim 1, characterized in that, The dopamine-modified silver nanowires were prepared by the following method: silver nanowires were dispersed in a Tris-HCl buffer solution with a concentration of 5-15 mg / mL, the pH was adjusted to 8.5, dopamine hydrochloride was added at a mass ratio of 1:1-3 to the silver nanowires, and the mixture was stirred at 20-30°C for 10-14 hours. After centrifugation and washing, the silver nanowires were obtained. The mass percentage of the dopamine-modified silver nanowires in the highly conductive functional region of the film was 10%-20% of the DA-TPU matrix.

4. The TPU film for robotic electronic skin according to claim 1, characterized in that, The MXene is a few-layer Ti3C2T x Its mass percentage in the highly conductive functional region of the thin film is 1%-5% of that of the DA-TPU matrix.

5. The TPU film for robotic electronic skin according to claim 1, characterized in that, The shell material of the phase change microcapsule is polyurethane or melamine resin, and the core material is a low-melting-point alloy or phase change polymer with a melting point between 45-70℃. The mass percentage of the core material in the film contact functional area is 5%-15% of the DA-TPU matrix.

6. The TPU film for robotic electronic skin according to claim 5, characterized in that, The phase change microcapsules are prepared by the following method: using in-situ polymerization, a low melting point alloy is melted at a temperature 5-10°C above its melting point, and then emulsified with an aqueous solution containing 1-5 wt% emulsifier at a high-speed shearing speed of 8000-12000 rpm for 5-15 minutes to form an O / W emulsion; subsequently, a shell prepolymer and a chain extender are added to the emulsion, and the reaction is carried out at 50-70°C for 3-5 hours. After the reaction is completed, the mixture is filtered, washed, and dried to obtain core-shell structured phase change microcapsule powder.

7. The TPU film for robotic electronic skin according to claim 1, characterized in that, The triboelectric nanofibers are polytetrafluoroethylene or nylon 6,6 fibers with an average fiber diameter of 100-500 nm and an aspect ratio greater than 50. Their mass percentage in the contact functional area of ​​the film is 3%-10% of that of the DA-TPU matrix.

8. A method for preparing a TPU film as described in any one of claims 1-7, characterized in that, Includes the following steps: S1: Preparation of TPU matrix with Diels-Alder dynamic reversible crosslinking network; S2: Preparation of dopamine-modified silver nanowires; S3: Preparation of an organic solvent dispersion of MXene; S4: Preparation of electrospinning sizing agent: S41: Conductive layer slurry: Dissolve the DA-TPU obtained in S1 in a DMF / THF mixed solvent to prepare a solution with a mass-volume concentration of 15%-25%, then add the dopamine-modified silver nanowires obtained in S2 and the MXene dispersion obtained in S3 in sequence, and disperse them evenly by ultrasonication. S42: Insulation / Transition Layer Paste: Dissolve the DA-TPU obtained in S1 in a DMF / THF mixed solvent to prepare a solution with a mass-volume concentration of 15%-25%; S43: Intelligent contact outer layer slurry: Dissolve the DA-TPU obtained in S1 in a DMF / THF mixed solvent to prepare a solution with a mass-volume concentration of 15%-25%, and add phase change microcapsules and triboelectric nanofibers, and ultrasonically disperse them evenly; S5: Using a multi-nozzle electrospinning device, at least two of the slurries obtained from S41, S42 and S43 are spatially oriented and spun synchronously according to a preset functional gradient structure, and a fiber membrane with a gradient conductive network structure is collected on a receiving device. S6: The collected fiber membrane is heat-treated at 65-75°C for 1-3 hours to obtain the electronic skin film.

9. The method for preparing a TPU film for robotic electronic skin according to claim 8, characterized in that, In step S5, the morphology of the gradient structure is controlled by independently adjusting the propulsion speed of each functional layer slurry, wherein the propulsion speed of the conductive layer slurry is 1.5-3.0 times that of the propulsion speed of the contact functional area slurry.

10. The method for preparing a TPU film for robotic electronic skin according to claim 8, characterized in that, The electrospinning process parameters in step S5 are as follows: spinning voltage is 12-20kV, receiving distance is 10-20cm, slurry feed speed is 0.3-1.0mL / h, ambient temperature is controlled at 20-30℃, and ambient humidity is controlled below 30%.

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