Preparation and application of a full-system TENG friction layer composite material

Abstract

This invention provides a method for preparing and applying a TENG friction layer composite material based on a complete system, belonging to the field of nano-energy materials and devices. The method includes the following steps: reacting SiO2 nanoparticles with KH556 silane coupling agent in ethanol, followed by centrifugation, washing, and drying to obtain KH556-SiO2 modified powder; using PFPE as the core material, forming an emulsion in the presence of an emulsifier, and using urea-formaldehyde resin to polymerize in situ on its surface to form a wall material, followed by centrifugation, washing, and drying to obtain PFPE microcapsules; mixing PDMS prepolymer, curing agent, PU solution, and zinc acetate, followed by stirring and degassing to obtain a uniform prepolymer matrix; adding a portion of the prepolymer matrix to KH556-SiO2 to form a surface trap liquid, which is then spin-coated onto the surface of a PTFE template to form a nanoscale trap layer; mixing the remaining prepolymer matrix with PFPE microcapsules and casting it onto the trap layer, allowing it to stand at room temperature to wet, forming a composite with a gradient structure; and vacuum curing and demolding the composite to obtain a composite film in which the surface trap layer and the deep matrix are tightly bonded.

Description

Technical Field

[0001] This invention relates to the field of nano-energy materials and devices, and in particular to the preparation and application of a TENG friction layer composite material based on a complete system. Background Technology

[0002] With the rapid development of the Internet of Things, distributed sensor networks, and wearable electronics, there is an urgent need for miniaturized, sustainable, and environmentally adaptive energy harvesting technologies. Triboelectric nanogenerators (TENGs), as a cutting-edge technology capable of efficiently converting mechanical energy (such as vibration, wind energy, and human movement) into electrical energy, have shown great application potential due to their simple structure, wide range of material choices, and high low-frequency energy harvesting efficiency. Their core working mechanism and output performance directly depend on the charge generation, storage, and retention capabilities of the triboelectric layer material. However, current TENG triboelectric layers based on traditional homogeneous polymer materials (such as polydimethylsiloxane and polytetrafluoroethylene) have long faced three interrelated fundamental bottlenecks in actual dynamic friction scenarios: Irreversible mechanical wear: Continuous solid-to-solid direct contact friction will cause damage to the microstructure of the friction layer surface, material loss, and surface roughening, resulting in a continuous decrease in effective contact area and triboelectric efficiency, ultimately leading to device failure.

[0003] Accumulated damage and functional degradation: Microcracks, scratches and other damage generated during friction cannot repair themselves, becoming channels for charge leakage and the starting point for further damage, leading to accelerated decay of the device's electrical performance and mechanical integrity.

[0004] Environmentally sensitive charge dissipation: Static charge generated by friction is easily neutralized or leaked due to environmental factors such as humidity and temperature. The surface charge density is difficult to maintain for a long time, which limits the stable output power and reliability of TENG.

[0005] To address these challenges, researchers have explored different approaches, but these improvements are often isolated and one-sided, failing to systematically solve the performance degradation problem. Self-lubricating pathways: such as Chinese patent CN111245283B, which reduce the coefficient of friction by introducing microcapsule lubricants or liquid interfaces, can reduce it to below 0.1, effectively reducing wear. However, uncontrollable consumption of lubricant may lead to functional failure and cannot repair existing matrix damage. For example, Chinese patent CN121378645A uses surface-modified self-healing polyurethane as the core material to achieve an energy conversion efficiency of 15%~20% for triboelectric nanogenerators (far exceeding the 8%~10% of traditional polyurethane-based TENGs), a short-circuit current of up to 90nA, and an open-circuit voltage of up to 40V. However, the number of self-healing cycles has an upper limit, and the repair effect decays after long-term use. For example, Chinese patent CN118813057 describes a self-healing elastomer membrane based on dynamic imine bonds modified with amino-functionalized ZIFs nanomaterials. Under the premise that its self-healing and remodeling efficiency both reach over 99%, the triboelectric nanogenerator constructed from this elastomer membrane still maintains a high triboelectric output. However, after completing 21,000 fatigue tests, problems such as decay of self-healing efficiency and decline in power generation performance occur.

[0006] In summary, existing technologies often focus on improving single performance indicators but fail to address all key performance aspects. Similarly, current research on TENG friction materials lacks a synergistic consideration of the systemic failure chain of "wear resistance-self-healing-high charge storage." Different functional mechanisms may even be mutually restrictive; for example, fillers that enhance charge storage may hinder the movement of the self-healing network, while soft matrices pursuing high repair efficiency may not be able to stably load lubricating microcapsules.

[0007] Therefore, developing an integrated intelligent friction material that can achieve orderly coordination of multiple functions in space and time and optimized internal partitioning, thereby fundamentally solving the durability and performance bottlenecks of TENG, has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing and applying a complete TENG friction layer composite material, solving the chain reaction problem of existing complete TENG friction layers: "wear leads to surface microstructure damage → charge density decrease → output performance degradation". Through innovative material composite design and optimized preparation process, a complete TENG friction layer composite material has been developed, meeting the requirements of complete TENG systems for "wear-self-lubrication and friction reduction-damage-self-repair and restoration-high charge capture throughout the process".

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a TENG friction layer composite material based on a complete system includes the following steps: Step 1: React SiO2 nanoparticles with KH556 silane coupling agent in ethanol, and after centrifugation, washing and drying, obtain KH556-SiO2 modified powder. Step 2: Using PFPE as the core material, an emulsion is formed in the presence of an emulsifier. Urea-formaldehyde resin is then used to polymerize in situ on its surface to form a wall material. After centrifugation, washing, and drying, PFPE microcapsules are obtained. Step 3: Mix PDMS prepolymer, curing agent, PU solution and zinc acetate, stir and degas to obtain a homogeneous prepolymer matrix; Step 4: Take a portion of the prepolymer matrix and add KH556-SiO2 to form a surface trap liquid, spin-coat it onto the PTFE template surface to form a nanoscale trap layer; then mix the remaining prepolymer matrix with PFPE microcapsules and cast it onto the trap layer, let it stand at room temperature to wet, and form a composite with a gradient structure. Step 5: Vacuum curing and demolding of the composite material yields a composite film in which the surface trap layer and the deep matrix are tightly bonded.

[0010] Furthermore, in step 1, the mass ratio of SiO2 nanoparticles to KH556 is (8-12):1.

[0011] Further, in step 2, the urea-formaldehyde resin includes urea and formaldehyde, with a molar ratio of urea to formaldehyde of 1:(1.2-1.8); the PFPE core material accounts for 50%-65% of the total mass of the microcapsules; and the amount of emulsifier SDBS added is 0.3%-0.8% of the water mass.

[0012] Furthermore, in step 3, the mass ratio of PDMS prepolymer to curing agent is (4-6):1; the mass ratio of PDMS system to PU solution is (2.5-3.5):1; and the amount of zinc acetate added is 2%-4% of the total mass of the prepolymer matrix.

[0013] Furthermore, in step 4, the amount of KH556-SiO2 added to the surface trapping solution is 15%-25%; the amount of PFPE microcapsules added is 10%-25% of the total mass of the deep matrix.

[0014] Furthermore, in step 5, the vacuum curing temperature is 60℃, the vacuum degree is ≥0.095MPa, and the curing time is 12h.

[0015] A composite material based on a complete TENG friction layer is prepared according to the aforementioned preparation method.

[0016] An application of a complete TENG friction layer composite material in triboelectric nanogenerators. The composite material, as the friction layer material, is suitable for various TENG structures such as contact-separation, sliding, rotating and single-electrode types, and is especially suitable for sliding / rotating TENGs for harvesting wind energy, water flow energy or rotational mechanical energy.

[0017] A sliding / rotating TENG includes a substrate, wherein the friction contact surface of the substrate is coated or adhered with a TENG friction layer composite material.

[0018] Furthermore, the composite material is applied in the form of a coating with a thickness of 20~50μm, and in the form of a thick film with a thickness of 200~500μm.

[0019] Furthermore, the substrate of the dynamic / rotational TENG is a glass or acrylic plate, and the composite material is used as a triboelectric negative electrode layer.

[0020] The composite material and the sliding / rotational TENG using this material achieve a combination of high-efficiency triboelectric charging and long-lasting wear resistance through the synergistic effect of multiple mechanisms, including surface charge trapping, deep dynamic bonding, and microcapsule self-healing.

[0021] The present invention, by adopting the above-described technical solution, has the following beneficial effects: 1. Self-lubricating and friction-reducing: PFPE microcapsules rupture under frictional pressure to release lubricant, reducing the coefficient of friction from 0.6~0.8 to 0.08~0.12, a reduction of more than 85%, significantly reducing wear; 2. Dynamic key self-repair: Zn 2+ -The dynamic coordination bond of the carboxyl group can achieve self-repair without external energy input at room temperature, with a repair time of <10 min, a repair rate of >90%, and can be repeatedly repaired >50 times; 3. Gradient charge trapping: Deep charge traps are formed in the surface KH556-SiO2, increasing the surface charge density to 1000 μC / m. 2 The above shows that the charge leakage rate under high humidity is <5% / h; 4. Synergistic cycle mechanism: Achieve a positive cycle of "wear → lubrication → repair → high output", which greatly improves the durability and output stability of TENG. Attached Figure Description

[0022] Figure 1 These are performance test diagrams of the composite material of this invention; Figure 2 These are microscope images of the self-healing composite material of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. However, it should be noted that many details listed in the specification are merely to provide the reader with a thorough understanding of one or more aspects of the invention, and these aspects of the invention can be implemented even without these specific details.

[0024] Example 1 (Sliding / Rotating TENG) A method for preparing a TENG friction layer composite material based on a complete system includes the following steps: I. Weighing of raw materials Step 1: 10g SiO2 and 200mL anhydrous ethanol. Core reaction / ratio: 1. Mass ratio: SiO2 nanoparticles : KH556 silane coupling agent = 10 : 1 (10g SiO2 corresponds to 1g KH556) 2. Glacial acetic acid is only used to adjust the pH of the system to 4-5. There is no fixed addition ratio. It is added dropwise until the system is weakly acidic.

[0025] Step 2: 500mL deionized water, 0.5wt% SDBS, 10g PFPE, 6g urea, 8mL 37% formaldehyde solution. Core reaction / ratio: 1. Molar ratio: Urea: 37% formaldehyde solution = 1:1.5 (6g urea corresponds to 8mL 37% formaldehyde solution, with excess formaldehyde to ensure the synthesis of urea-formaldehyde resin prepolymer). 2. Microcapsule core-to-wall ratio: PFPE core material accounts for 58.7% of the total mass of microcapsules (10g PFPE corresponds to a wall material system of 6g urea + 8mL formaldehyde). 3. The amount of SDBS emulsifier added is 0.5wt% of deionized water, and NaOH is only used to adjust the pH to 8-9 (emulsification stage) and 2-3 (polymerization stage), with no fixed ratio.

[0026] Step 3: Mix 7g PDMS prepolymer and 1.4g curing agent thoroughly, then add 3g PU solution (50% solids content) and 0.3g zinc acetate. All proportions are by mass, based on the preparation of 10g PDMS / PU matrix. 1. PDMS system: PDMS prepolymer:PDMS curing agent = 5:1 (7g prepolymer corresponds to 1.4g curing agent), accounting for 84% of the total matrix mass; 2. Blending ratio: PDMS system: PU solution (50% solid content) = 8.4:3, PU solid content accounts for 30% of the total mass of the matrix (actual PU solid content 1.5g); 3. Dynamic bond system: The amount of zinc acetate added is 3wt% of the total mass of the matrix (10g matrix corresponds to 0.3g zinc acetate).

[0027] Step 4: Take 2g of the prepolymer matrix from Step 3, add 0.4g of KH556-SiO2, 8g of the prepolymer matrix from Step 3, and 1.5~2.0g of PFPE microcapsules. Core formulation ratio (mass ratio): 1. Surface trap layer: KH556-SiO2 accounts for 20wt% of the surface trap liquid (take 2g of the prepolymer matrix from step 3, add 0.4g of KH556-SiO2, and stir to disperse into a surface trap liquid). 2. Deep matrix: The amount of PFPE microcapsules added is 15~20wt% of the total mass of the matrix (10g matrix corresponds to 1.5~2.0g microcapsules). 3. The volume ratio of the surface trap liquid to the deep matrix is ​​1:9, ensuring that the surface trap layer thickness is 100~500nm and the deep matrix thickness is 50~200μm (overall target thickness).

[0028] II. Material Preparation Step 1: Add nano-SiO2 nanoparticles and anhydrous ethanol to a three-necked flask and magnetically stir to form a uniform suspension to prevent particle agglomeration; add KH556 dropwise, stir for 10 min, then add glacial acetic acid to adjust the pH to 4-5, heat to 60℃, reflux and stir for 4 h to ensure that the coupling agent fully binds to the hydroxyl groups on the SiO2 surface; after the reaction is complete, centrifuge the suspension, collect the precipitate, wash it three times with anhydrous ethanol to remove unreacted KH556; place the washed precipitate in an 80℃ forced-air drying oven to dry for 12 h, grind it through a 200-mesh sieve to obtain KH556-SiO2 modified powder, and seal it in a desiccator for later use; In step 1, the magnetic stirring speed is 400-600 r / min and the time is 20-40 min; the centrifugation speed is 7000-9000 r / min and the time is 8-12 min.

[0029] Preferably, in step 1, the magnetic stirring conditions are: rotation speed 500 r / min for 30 min, and centrifugation of turbid liquid at 8000 r / min for 10 min.

[0030] Step 2: Add deionized water and SDBS to a three-necked flask, stir to dissolve, then add PFPE and stir at high speed for 30 min to form an O / W type emulsion with droplet size controlled at 1~5 μm; add urea and formaldehyde solution, adjust pH to 8~9 with NaOH, heat to 70℃, stir for 1 h to synthesize urea-formaldehyde resin prepolymer; adjust pH to 2~3 with dilute hydrochloric acid, cool to 50℃, stir at low speed for 4 h to polymerize, the urea-formaldehyde resin prepolymer polymerizes in situ on the surface of PFPE droplets to form wall material; after the reaction is complete, collect the microcapsules by centrifugation, wash 3 times with deionized water, dry in a vacuum drying oven at 60℃ for 8 h, and pass through a 100-mesh sieve; In step 2, the high-speed shear stirring speed is 2500-3500 r / min and the time is 20-40 min; in the polymerization stage, the low-speed stirring speed is 200-400 r / min and the time is 3-5 h.

[0031] Preferably, in step 2: high-speed shear stirring at 3000 r / min for 30 min, low-speed stirring at 300 r / min for 4 h, centrifugation at 6000 r / min for 15 min to collect microcapsules.

[0032] Step 3: Add PDMS prepolymer and curing agent to a PTFE beaker, stir magnetically for 10 minutes, mix thoroughly, then add PU solution (50% solids content), continue stirring for 20 minutes to form a homogeneous PDMS / PU blend prepolymer; add zinc acetate, stir for 30 minutes to ensure complete dispersion of zinc acetate, Zn 2+ Preliminary complexation with carboxyl groups in PU; place the beaker in a vacuum degassing machine and degas for 15 minutes under a vacuum of 0.09 MPa to remove bubbles introduced during stirring. A bubble-free, homogeneous, viscous prepolymer matrix is ​​considered qualified; place the degassed prepolymer matrix on a dust-free workbench at room temperature (25±2℃) and complete the gradient molding of the subsequent step 4 within 30 minutes to prevent premature crosslinking; In step 3, the magnetic stirring speed is 250-350 r / min, and the time is 8-12 min.

[0033] Preferably, in step 3: magnetic stirring (300 r / min) for 10 min.

[0034] Step 4: Take the prepolymer matrix from Step 3, add KH556-SiO2, stir magnetically for 15 min, and ultrasonically disperse for 5 min to form a non-agglomerated surface trap liquid; fix the PTFE template on the sample stage of the spin coater, drop the surface trap liquid onto the center of the template, and set the spin coating parameters: low speed 500 r / min (5 s, uniform spreading) → high speed 3000 r / min (30 s, thickness control). After spin coating, a uniform trap layer of 100~500 nm thick is formed on the template surface; within 5 min after spin coating, add the remaining prepolymer matrix from Step 3 (1.5~2.0 g). PFPE microcapsules (after being stirred and dispersed evenly) are slowly cast onto the surface trap layer. The PTFE template is then gently smoothed with a PTFE scraper to ensure uniform matrix thickness, without sagging or bubbles. After casting, the PTFE template is placed on a dust-free workbench and left to stand at room temperature for 5 minutes to allow the surface trap layer and deep matrix to initially wet, ensuring no delamination at the interface and forming a PTFE template-prepolymer matrix composite (surface trap layer + deep dynamic bond / microcapsule matrix). The spin coating parameters for step 4 are: low speed 400-600 r / min for 3-8 s, then high speed 2500-3500 r / min for 20-40 s.

[0035] Preferably, in step 4: the magnetic stirring speed is 400 r / min for 15 min, the ultrasonic dispersion power is 200 W for 5 min, and the spin coating parameters are set as follows: low speed 500 r / min (5 s, uniform spreading) → high speed 3000 r / min (30 s, controlling thickness). After spin coating, a uniform trap layer with a thickness of 100~500 nm is formed on the template surface.

[0036] Step 5: This step requires no new raw materials. The operation is divided into three parts: mandatory vacuum curing, mandatory demolding and basic post-treatment, and optional laser etching. The core operations, instruments, parameters, and indicators strictly follow the original content. The core control points are: vacuum degree ≥ 0.095MPa, uninterrupted curing, PTFE demolding equipment, and laser etching layer scanning + nitrogen purging. The final result is a milky white semi-transparent composite film with no bubbles or scratches, and the surface trap layer is tightly bonded to the deep matrix.

[0037] The core premise is: 1. State of the material to be cured: After step 4 completes the surface spin coating + deep casting + microcapsule dispersion, the prepolymer matrix in the PFTE template has no obvious bubbles and no scratches on the surface. The commonly used size of the PFTE template is 50mm×50mm / 100mm×100mm. The spin coating-casting interval is strictly <5min, and there is no delamination at the interface. 2. Consistency of raw material ratio: The concentration and ratio of all materials are consistent with steps 1-4. This step only controls the curing process parameters and does not involve any addition / dilution operations. 3. Molds and tools: Polytetrafluoroethylene (PFTE) molds / scrapers are used throughout the process. Avoid using metal tools to contact the uncured substrate to prevent adhesion / introduction of impurities and damage to the charge trap layer.

[0038] Detailed operation steps: 1. Template fixing: On a dust-free operating table, place the PTFE template-prepolymer matrix composite formed in step 4 flat on the oven tray. Use high-temperature resistant silicone clamps to gently press the edges of the template to fix it, without applying external pressure, to avoid squeezing and damaging the 100~500nm trap layer on the surface. 2. Oven preheating: Preheat the vacuum drying oven to 60°C. After the temperature stabilizes, place the fixed composite material inside. Preheating before placing the composite material inside can prevent microbubbles from forming on the matrix due to a sudden temperature rise. 3. Vacuuming operation: Close the oven door, first open the vacuum valve, and slowly increase the vacuum level inside the oven to 0.095 MPa. The pumping rate is controlled at 0.01 MPa / min to avoid rapid vacuuming that could cause pinholes on the substrate surface. After the vacuum level reaches 0.095 MPa, close the vacuum valve and maintain the vacuum pressure for curing. 4. Constant temperature curing: Continuous curing for 12 hours at 60℃ and 0.095 MPa vacuum, without interruption or temperature adjustment. The curing kinetics follow α=1-e^(-kt), k=0.21 h. -1 After 12 hours, the degree of curing can be stabilized at 80%. 5. Natural pressure relief and cooling: After the curing time is up, first turn off the oven heating switch and keep it in vacuum to cool naturally to room temperature of 25±2℃, which takes about 2~3 hours. Avoid direct pressure relief at high temperature, which may cause the substrate to expand and contract and crack. After cooling is complete, slowly open the vent valve to restore the oven to normal pressure, with a rate of <0.02 MPa / min; Sample Removal: Using heat-resistant gloves, remove the PFTE template-cured matrix composite and place it on a clean bench to cool to room temperature for approximately 10 minutes. It is crucial to avoid depressurizing or heating during the curing process, as this will lead to uneven PDMS crosslinking, insufficient dynamic bond formation, and a decrease in mechanical properties and self-healing efficiency of >30%. If the vacuum level is below 0.09 MPa, residual air bubbles will remain in the matrix, causing the dielectric loss tangent (tanδ) to increase from 0.02 to over 0.08, thus increasing energy loss.

[0039] Among them, the specific operation steps 1. Cleaning before demolding: Use a lint-free cloth dampened with a small amount of anhydrous ethanol to gently wipe the edges of the PFTE template surface to remove surface dust and avoid scratching the film during demolding; 2. Edge film separation: Insert the PTFE release knife into the corner of the PFTE template between the template and the cured film to a depth of <1mm, and gently pry upwards to separate the film edge from the template. Only pry the edge; do not insert the knife into the middle of the film to prevent delamination. 3. Complete peeling: Pinch the edge of the separated film with your fingers and slowly and evenly peel the film off the template. Keep the peeling angle at 15~30°. If the angle is too large, it will easily cause the surface trap layer to separate from the deep matrix. 4. Thickness inspection: Use a micrometer to measure the thickness of the film at 5 points, one in the center and one at each of the four corners, to ensure that the thickness uniformity is <5%. The target thickness is 50~200μm as the optimal thickness of the TENG friction layer. If the thickness exceeds the standard, return to step 4 to adjust the casting amount. 5. Size cutting: According to the required TENG structural design, use a precision paper cutter to cut the film into two sizes: 20mm×20mm and 50mm×50mm. After cutting, wipe the edges of the film with a lint-free cloth to remove burrs. 6. Drying and storage: Place the cut film in a 60℃ forced-air drying oven for 30 minutes to remove any residual anhydrous ethanol from the demolding process. After cooling, seal it in a dust-free self-sealing bag and store it in a desiccator with a humidity of <30%RH.

[0040] The specific operational steps for laser etching to prepare micron-sized microstructures include... 1. Sample fixation: Lay the cut composite film flat on the sample stage of the laser etching machine, turn on the vacuum adsorption of the sample stage to make the film completely adhere to the sample stage without wrinkles, and avoid etching size deviation; 2. Etching parameter settings: Laser wavelength: 355 nm, power: 10 W, scanning speed: 50 mm / s; Etching pattern: Square pillars with a side length of 50 μm and a pillar spacing of 50 μm / Pyramid with a base side length of 50 μm and a height of 10 μm; Scanning method: Layered scanning, with an etching depth of 2 μm per layer, for a total of 5 layers, to avoid ablation of the surface trap layer by a single high-power etching; Etching range: Covering the entire effective friction area of ​​the film, with a 2 mm blank area left at the edge to prevent electrode short circuits; 3. Trial etching and calibration: Perform a small-area trial etching (5mm × 5mm) at the blank edge of the thin film. Observe the microstructure dimensions using an optical microscope. If the deviation from the target size is >5%, adjust the scanning speed / power. Power and depth are proportional (h ∝ P). 0.9 Speed ​​is negatively correlated with depth; 4. Formal Etching: After calibration, start the laser etching machine to perform the entire etching process. During the etching process, use a nitrogen spray gun to continuously blow and clean the etching area. 5. Post-etching treatment: After etching is completed, the film is removed, the surface debris is blown away with a nitrogen spray gun, then wiped gently with a lint-free cloth, and finally placed in a 60℃ vacuum oven to dry for 1 hour to remove trace amounts of volatile organic compounds generated during etching.

[0041] Finally, the microstructures were obtained with a size of 50μm×50μm and a depth of 10μm, a distribution uniformity of <3%, no ablation of the surface trap layer, no collapse of the microstructure sidewalls, and a contact area that was 3 times larger than that of the unetched film.

[0042] The core of steps 1-4 is: functional powder drying and preparation + stepwise composite with liquid prepolymer matrix + in-situ gradient physical molding. No additional chemical bonding medium is used; the organic combination of products from each step is achieved solely through physical dispersion and interfacial wetting. The operational logic revolves around "first preparing the functional phase, then preparing the continuous phase, and finally gradient composite molding," as detailed below: 1. Connecting medium The KH556-SiO2 modified powder in step 1 and the PFPE microcapsule powder in step 2 are both directly dispersed in the PDMS / PU-Zn mixture in step 3, using dry powder as a transition medium. 2+ In the liquid prepolymer matrix, the viscosity of the prepolymer matrix is ​​used to achieve uniform dispersion of the functional phase without the addition of any coupling agent, dispersant or other additional connecting medium.

[0043] 2. Connection Method (1) Dispersed combination of functional phase and continuous phase After drying, the functional powders prepared in steps 1 and 2 are dispersed in the liquid prepolymer matrix of step 3 by physical methods of ultrasonic dispersion and magnetic stirring: KH556-SiO2 is dispersed in part of the prepolymer matrix to form a surface trap liquid, and PFPE microcapsules are dispersed in the remaining prepolymer matrix to form a deep matrix. Physical dispersion is used to ensure the uniformity of the functional phase in the continuous phase. There is no chemical reaction, only physical mixing.

[0044] (2) Gradient molding combination of surface and deep layers The connection between the surface trap layer and the deep substrate is achieved through an in-situ physical molding method of spin coating and casting: First, a thin liquid layer of surface trap liquid is formed by spin coating on a PTFE template, and then the deep substrate is quickly cast on its surface. The liquid flowability of the prepolymerized substrate is used to achieve interface wetting and fusion. The spin coating-casting interval is strictly <5min to avoid premature cross-linking of the surface trap liquid and resulting in interface delamination, and finally a gradient structure without interface defects is formed.

[0045] 3. Core Operation Logic 1. Stepwise preparation and drying for later use: In steps 1 and 2, highly active and highly compatible functional powders (KH556-SiO2, PFPE microcapsules) are prepared independently, dried and sealed for later use to avoid functional phase failure and to provide stable functional raw materials for subsequent compounding. 2. Single-pot synthesis, continuous phase unification: Step 3 prepares PDMS / PU-Zn in one step. 2+ The prepolymer matrix, as the only continuous phase in the entire system, ensures the consistency of the basic properties of the composite material. The introduction of Zn... 2+ -Carboxyl dynamic bonds provide the chemical basis for self-healing in deep matrices; 3. Gradient introduction and functional zoning: In step 4, the charge trapping phase from step 1 and the self-healing phase from step 2 are introduced into the continuous phase from step 3 in a gradient manner. The high-concentration charge trapping layer on the surface is formed by spin coating, and the distribution of deep dynamic bonds and microcapsules is achieved by casting, thus realizing the functional zoning of "surface energy storage and deep self-healing". 4. In-situ molding with template constraint: PTFE is used as the molding template, and the gradient molding is completed entirely within the template. The low adhesion of the template avoids the prepolymer matrix from sticking, ensuring the integrity of subsequent demolding. At the same time, the template provides a fixed spatial constraint for gradient molding, ensuring the dimensional accuracy of the composite material.

[0046] Overall, steps 1 and 4 are connected by the logic of "independent preparation of functional phases → unified synthesis of continuous phases → gradient physical dispersion of functional phases → in-situ molding within the template". There are no complex chemical connection reactions. The organic combination of the products of each step is achieved only through physical dispersion and interface wetting, which ensures the realization of the gradient structure and function of the composite material.

[0047] Core preparations before using PTFE molding templates: 1. Clean the surface: Wipe the template surface with anhydrous ethanol or acetone to thoroughly remove oil, dust, release agent residue and other impurities. 2. Check integrity: Confirm that the template is free of cracks, deformation, deep scratches and edge damage to avoid defects in the molded parts.

[0048] Finally, the prepared composite material is coated / bonded onto the substrate of the sliding / rotating TENG, wherein the bonding is done with transparent conductive adhesive.

[0049] III. Performance Testing: Testing showed that... Figure 1 As shown, the friction coefficient of this material is reduced from 0.6~0.8 for traditional PDMS to 0.08~0.12 (a reduction of over 85%), achieving self-healing without external energy input (healing time <10 min, repair rate >90%). Laboratory tests show that the material can be repeatedly repaired >50 times, with tensile strength and elongation at break retaining >90% and triboelectric output retaining >95% after repair. The surface charge density is reduced from <100 μC / m² for traditional PDMS. 2 Increased to 1000 μC / m 2 The above indicates that deep traps (trap depth > 1 eV) have a strong ability to bind charges, and even in high humidity (RH > 80%) environments, the charge leakage rate is < 5% / h.

[0050] To address the chain reaction of traditional TENG friction layers—"wear leading to surface microstructure damage → charge density decrease → output performance degradation"—this approach abandons the compromise of "single modification (such as only adding a wear-resistant coating / only making microstructures)" and achieves a positive cycle of "wear-self-lubrication and friction reduction-damage-self-repair and restoration-high charge capture throughout the process." 1. Self-lubricating and friction-reducing mechanism When contact friction occurs in the TENG friction layer, if the contact pressure is >0.5 MPa / wear depth is >1 μm (TENG's normal working wear threshold), the urea-formaldehyde resin microcapsule wall material in the matrix ruptures, releasing the internal PFPE liquid lubricant. PFPE quickly spreads at the friction interface, forming a continuous liquid lubricating film, reducing the coefficient of friction from 0.6~0.8 of traditional PDMS to 0.08~0.12 (a reduction of more than 85%), significantly reducing mechanical wear and microstructure damage of the friction layer, and extending the material's service life.

[0051] Additional gain: PFPE is a highly triboelectrone material. After release, it forms a liquid-solid heterogeneous triboelectrode interface between PTFE and aluminum foil triboelectrode layers. Compared with traditional solid-solid interfaces, the charge separation efficiency is improved by more than 50%, further enhancing the output performance.

[0052] 2. Dynamic key self-repair mechanism If excessive local pressure at the friction interface leads to microcracks / micro-damage in the material, the Zn at the damaged area... 2+ -Carboxyl dynamic coordination bond (Zn) 2+ -OOC-) breakage; at room temperature, the matrix molecular chains are rapidly reconstructed through thermal motion, and the broken coordination bonds recombine, achieving self-repair without external energy input, with repair time <10 min and repair rate >90%.

[0053] Repair effect: After microcrack repair, the integrity of the microstructure and surface charge trap of the friction layer surface is restored, and the charge trapping ability and mechanical properties are restored simultaneously, avoiding the overall output performance decay caused by local damage; According to laboratory tests, the material can be repaired repeatedly >50 times, and the tensile strength and elongation at break after repair are maintained at >90%, and the triboelectric output is maintained at >95%.

[0054] 3. Gradient charge trap enhancement mechanism The 100-500 nm KH556-SiO2 nanoparticles on the surface of the composite material form a high-concentration deep charge trap. When contact charging occurs in the triboelectric layer, the generated free charges are rapidly captured and stored in the trap, inhibiting charge leakage and neutralizing, thus reducing the surface charge density from <100 μC / m² in traditional PDMS. 2 Increased to 1000μC / m 2 The above; however, the deep matrix contains only low concentrations of trap particles, retaining Zn. 2+ - The flexible network of dynamic carboxyl bonds ensures the material's mechanical toughness and self-healing ability.

[0055] Charge stabilization mechanism: deep traps, where the trap depth is >1 eV, have a strong ability to bind charges. Even in high humidity environments, where RH>80%, the charge leakage rate is <5% / h, further improving output stability.

[0056] 4. Overall Coordination and Cycle Wear → Microcapsule rupture → PFPE release → Self-lubricating friction reduction + heterogeneous interface charge increase → Local damage → Dynamic bond reconstruction → Self-repair → Surface trap continuously captures charge → High output throughout the process + low wear, completely breaking the performance bottleneck of traditional TENG.

[0057] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a TENG friction layer composite material based on a complete system, characterized in that: Includes the following steps: Step 1: React SiO2 nanoparticles with KH556 silane coupling agent in ethanol, and after centrifugation, washing and drying, obtain KH556-SiO2 modified powder. Step 2: Using PFPE as the core material, an emulsion is formed in the presence of an emulsifier. Urea-formaldehyde resin is then used to polymerize in situ on its surface to form a wall material. After centrifugation, washing, and drying, PFPE microcapsules are obtained. Step 3: Mix PDMS prepolymer, curing agent, PU solution and zinc acetate, stir and degas to obtain a homogeneous prepolymer matrix; Step 4: Take a portion of the prepolymer matrix and add KH556-SiO2 to form a surface trap liquid, spin-coat it onto the PTFE template surface to form a nanoscale trap layer; then mix the remaining prepolymer matrix with PFPE microcapsules and cast it onto the trap layer, let it stand at room temperature to wet, and form a composite with a gradient structure. Step 5: Vacuum curing and demolding of the composite material yields a composite film in which the surface trap layer and the deep matrix are tightly bonded.

2. The preparation method of a TENG friction layer composite material based on a complete system according to claim 1, characterized in that: In step 1, the mass ratio of SiO2 nanoparticles to KH556 is (8-12):

1.

3. The method for preparing a TENG friction layer composite material based on a complete system according to claim 1, characterized in that: In step 2, the urea-formaldehyde resin includes urea and formaldehyde, with a molar ratio of urea to formaldehyde of 1:(1.2-1.8); the PFPE core material accounts for 50%-65% of the total mass of the microcapsules; and the amount of emulsifier SDBS added is 0.3%-0.8% of the water mass.

4. The preparation method of a TENG friction layer composite material based on a complete system according to claim 1, characterized in that: In step 3, the mass ratio of PDMS prepolymer to curing agent is (4-6):1; the mass ratio of PDMS system to PU solution is (2.5-3.5):1; and the amount of zinc acetate added is 2%-4% of the total mass of the prepolymer matrix.

5. The method for preparing a TENG friction layer composite material based on a complete system according to claim 1, characterized in that: In step 4, the amount of KH556-SiO2 added to the surface trapping solution is 15%-25%; the amount of PFPE microcapsules added is 10%-25% of the total mass of the deep matrix.

6. The method for preparing a TENG friction layer composite material based on a complete system according to claim 1, characterized in that: In step 5, the vacuum curing temperature is 60℃, the vacuum degree is ≥0.095MPa, and the curing time is 12h.

7. A TENG-based friction layer composite material prepared according to any one of claims 1-6.

8. An application of the TENG-based composite material for a complete system of friction layers as described in claim 7 in a triboelectric nanogenerator, characterized in that: Composite materials, as friction layer materials, are suitable for contact-separation, sliding, rotating, and single-electrode TENGs.

9. A sliding / rotating TENG, characterized in that: Includes a substrate, the friction contact surface of which is coated or adhered with a TENG friction layer composite material.

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