Preparation method and application of flexible photo-thermal device based on GOMxene

Abstract

The invention relates to the technical field of new energy materials and flexible devices, in particular to a preparation method and application of a flexible photo-thermal device based on GOMxene, and the device is sequentially laminated with a photo-thermal layer (the mass ratio of GO to MXene is 1: 1-1: 3), a Bi2Te3-based thermoelectric layer, a PVA / BNNS composite hydrogel flexible substrate layer and a carbon cloth electrode layer, and is integrally formed by a TPU packaging layer. According to the preparation method and application of the flexible photo-thermal device based on GOMxene, the photo-thermal conversion efficiency reaches 85.5%, and the performance retention rate exceeds 90% after aging for 500 h at 60 DEG C / 90% RH; the heat conduction of the substrate is 1.2 W / mK, so that local overheating can be prevented; the power is attenuated by 1t after being bent for 10000 times; the maximum power of 0.92 mW can be output, the recovery rate exceeds 85% after heating at 60 DEG C for 5 minutes after cutting, and the material is suitable for wearable self-powered equipment.

Description

Technical Field

[0001] This invention relates to the field of new energy materials and flexible devices, specifically a method for fabricating and applying a flexible photothermal device based on GOMxene. Background Technology

[0002] With the development of technology, the demand for flexible, wearable, and implantable electronic devices is increasing. These devices, due to their advantages such as light weight, portability, flexibility, and ability to conform to irregular surfaces, show great application potential in fields such as personal health management, smart healthcare, human-computer interaction, and soft robotics. Currently used photothermal materials include carbon nanotubes, graphene, and metal nanowires. Although they possess certain photothermal conversion capabilities, they still suffer from insufficient thermal management performance, poor durability, and susceptibility to aging or failure at high temperatures. Therefore, developing a new energy technology that can provide continuous, self-powered energy to flexible devices and matches their flexible characteristics is crucial. Mxene (Ti3C2T) x As an emerging two-dimensional material, it possesses metallic conductivity and excellent intrinsic photothermal properties. However, its environmental stability is extremely poor, and it is easily oxidized in water and oxygen environments, leading to rapid performance degradation, which severely limits its practical applications. On the other hand, the thermal conductivity of commonly used flexible polymer substrates is extremely low (typically <0.5W / m・K), which prevents the heat generated by photothermal processes from dissipating quickly, easily forming local hot spots. This not only results in low energy utilization efficiency but also poses a safety hazard of burning the skin, failing to meet the stringent thermal management requirements of wearable devices.

[0003] Currently, although there have been attempts to improve stability by combining carbon materials with Mxene or to improve thermal conductivity by using metal meshes, the former has not solved the bottleneck of substrate thermal management and the composite structure is simple; the latter mainly focuses on electrothermal heating and does not involve photothermal self-powering and its application in specific wearable scenarios (such as watch straps). Therefore, the flexible photothermal devices in the existing technology have obvious defects in thermal safety management and cannot meet the comprehensive requirements of wearable devices for continuous self-powering, thermal safety and flexible matching. Therefore, in view of the above situation, it is urgent to develop a fabrication method and application of GOMxene-based flexible photothermal devices to overcome the shortcomings in current practical applications. Summary of the Invention

[0004] The purpose of this invention is to provide a method for fabricating and applying a flexible photothermal device based on GOMxene, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A flexible photothermal device based on GOMxene includes a photothermal layer, a thermoelectric layer, a flexible substrate layer and an electrode layer stacked sequentially, as well as an encapsulation layer that encapsulates the entire device.

[0007] The photothermal layer is a composite material layer of graphene oxide (GO) and MXene, the thermoelectric layer is a Bi2Te3-based thermoelectric material layer, the flexible substrate layer is a polymer-based composite material layer containing highly thermally conductive fillers, the electrode layer is a carbon cloth layer, and the encapsulation layer is a thermoplastic polyurethane (TPU) layer.

[0008] As a further aspect of the present invention: in the photothermal layer, the mass ratio of GO to MXene is 1:1 to 1:3.

[0009] As a further aspect of the present invention: the high thermal conductivity filler in the flexible substrate is boron nitride nanosheets or alumina nanoparticles, and the mass percentage of the high thermal conductivity filler in the flexible substrate is 10%-20%.

[0010] As a further aspect of the present invention: the electrode layer is connected to the thermoelectric layer through flexible conductive silver paste, and the interface contact resistance between the electrode layer and the thermoelectric layer is less than 0.5Ω.

[0011] A method for fabricating the above-described flexible photothermal device based on GOMxene includes the following steps:

[0012] (1) Preparation of photothermal layer: GO dispersion and MXene dispersion are mixed, crosslinking agent is added, and then the mixture is coated, dried and thermally reduced to obtain GO and MXene composite material layer;

[0013] (2) Preparation of thermoelectric layer: Bi2Te3 powder and Sb2Te3 powder are mixed, ball-milled, densified by spark plasma sintering and cut to obtain Bi2Te3-based thermoelectric material layer;

[0014] (3) Preparation of flexible substrate layer: The polymer is mixed and dispersed with high thermal conductivity filler, and subjected to freeze-thaw cycle treatment to obtain a polymer-based composite material layer containing high thermal conductivity filler;

[0015] (4) Device integration and packaging: The photothermal layer, thermoelectric layer, flexible substrate layer and carbon cloth electrode layer prepared in steps (1)-(3) are stacked in sequence. The electrode layer and thermoelectric layer are connected by flexible conductive silver paste. Then, the TPU encapsulation layer is covered by hot pressing to obtain a flexible photothermal device.

[0016] As a further aspect of the present invention: in step (1), the crosslinking agent is sodium tetraborate, and the amount of the crosslinking agent added is 1%-2% of the total mass of the GO and MXene mixture.

[0017] As a further aspect of the present invention: in step (2), the mixing mass ratio of Bi2Te3 powder to Sb2Te3 powder is 19:1, the ball-to-material ratio during ball milling is 15:1, and the temperature and pressure of spark plasma sintering are 420°C and 50MPa.

[0018] As a further aspect of the present invention: in step (3), the polymer is polyvinyl alcohol, the number of freeze-thaw cycles is 2, the freezing time is 12 hours and the thawing time is 6 hours each time.

[0019] As a further aspect of the present invention: in step (1), the temperature of thermal reduction is 200°C and the time is 2 hours; in step (4), the temperature of hot pressing is 120°C, the pressure is 0.3 MPa and the time is 60 seconds.

[0020] An application of the aforementioned GOMxene-based flexible photothermal device, wherein the flexible photothermal device is used in wearable self-powered devices to provide continuous power to low-power electronic components.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1. It possesses excellent photothermal conversion efficiency and stability. The synergistic effect of GO and MXene in the photothermal layer significantly broadens the absorption range of the solar spectrum and improves the photothermal conversion efficiency, which can reach over 85% in laboratory tests. Among them, the device with a GO / MXene mass ratio of 1:2 has a photothermal conversion efficiency of up to 85.5% under illumination and a steady-state temperature of 83.5℃. After continuous exposure for 500 hours in an environment of 60℃ and 90%RH, the photothermal performance (measured by the time required to reach 80℃) still retains more than 90%. GO plays an excellent role in antioxidant protection for MXene, which is significantly better than pure MXene devices without GO protection (efficiency of 78% under the same conditions, performance retention rate of <50% after 500 hours of aging).

[0023] 2. It achieves efficient thermal safety management. The thermal conductivity of the flexible substrate layer doped with high thermal conductivity nanoparticles can be increased to 1.2-3 W / m·K, which can quickly diffuse the heat generated by the photothermal layer laterally and avoid the formation of local high temperature points. Compared with the comparison device with pure PVA hydrogel (thermal conductivity 0.3 W / (m·K)) as the substrate (ΔT as high as 22℃ under the same conditions), the surface temperature difference of this device is small after reaching photothermal steady state. Combined with the longitudinal conduction and conversion of heat by the thermoelectric layer, the risk of burns to the skin by wearable devices is completely eliminated, and the requirements of wearable devices for thermal safety management are met.

[0024] 3. Possessing excellent flexibility and mechanical durability, each functional layer is made of flexible materials and integrated through a one-piece molding process, giving the device good bending performance (minimum bending radius up to 5mm, actual test up to 4mm), tensile strength (strain >15%), and fatigue resistance. It can closely conform to human skin or various irregular surfaces. After 10,000 reciprocating bending tests with a radius of 5mm, its thermoelectric output power decay rate is less than 5%, and there is no delamination or cracking, which is far superior to the comparative devices based on rigid bonding (which usually show interface peeling and significant performance degradation (>20%) after 1,000-2,000 bending cycles).

[0025] 4. It has stable thermoelectric output performance under standard illumination (1000W / m²). 2 Under these conditions, the device can provide a stable temperature difference of approximately 45-50°C, continuously output an open-circuit voltage of 130mV, and a maximum output power of 0.92mW, which is sufficient to continuously power low-power electronic components (such as temperature and humidity sensors).

[0026] 5. It has excellent self-healing properties. After the device (including the hydrogel substrate and photothermal layer) is completely cut through with a blade, the cut surfaces are gently touched and aligned, heated on a 60°C hot plate for 5 minutes, and cooled to room temperature, the tensile strength of the device can be restored to more than 85% of the original value, and the photothermal performance recovery rate exceeds 88%. This characteristic greatly improves the service life and reliability of the device after accidental damage. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the device in an embodiment of the present invention. Detailed Implementation

[0028] 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.

[0029] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0030] Please see Figure 1 The present invention provides a method for fabricating and applying a flexible photothermal device based on GOMxene, which specifically includes the following:

[0031] I. Raw Material Preparation

[0032] All raw materials used in this embodiment meet the functional requirements of the device. Their specific specifications and sources are as follows:

[0033] Photothermal layer raw materials: Graphene oxide (GO) dispersion (concentration 2 mg / mL, self-made); Ti3C2T x MXene dispersion (concentration 4 mg / mL, requiring 1.68 g LiF and 20 mL 8 mol HCl, etching temperature 40°C to avoid excessive oxidation of MXene, etching time 48 h, ultrasonic power 100 W, time not exceeding 8 min, followed by centrifugation at 3500 rpm for 60 min, collection of the supernatant, and finally washing with a large amount of deionized water until the pH of the supernatant is >6, prepared by selective etching of Ti3AlC2 followed by ultrasonic exfoliation, with the dispersion concentration precisely controlled within the range of 3-5 mg / mL to avoid MXene nanosheets recombination); sodium tetraborate (analytical grade, used as a crosslinking agent).

[0034] Thermoelectric layer raw materials: Bi2Te3 powder (99.99% purity); Sb2Te3 powder (99.99% purity), both used to prepare high-performance thermoelectric materials doped with antimony based on bismuth.

[0035] Flexible substrate raw materials: polyvinyl alcohol (PVA, type 1799, analytical grade); boron nitride nanosheets (BNNS, thickness <5nm, diameter 1μm, as a high thermal conductivity filler); deionized water (used to dissolve PVA and disperse BNNS).

[0036] Electrode layer raw material: commercial carbon cloth (0.3mm thick, with good conductivity and flexibility, meeting the flexibility requirements of adapter components).

[0037] Encapsulation layer raw material: transparent thermoplastic polyurethane (TPU) film (thickness 50μm, visible light transmittance >90%, tensile elongation at break >400%, used for device environmental protection).

[0038] Auxiliary materials: copper mesh (150 mesh, 50μm wire diameter); acetone and ethanol (analytical grade, used for cleaning carbon cloth surface); high thermal conductivity silicone grease (used to reduce the interfacial thermal resistance between the thermoelectric layer and the photothermal layer); flexible conductive silver paste (used for electrode connection to ensure low contact resistance); epoxy resin adhesive (used for electrode point fixation).

[0039] II. Preparation of each functional layer

[0040] 2.1 Preparation of the photothermal layer (GO / MXene composite photothermal film);

[0041] Preparation of composite dispersion: GO dispersion (2 mg / mL) was mixed with Ti3C2T xThe MXene dispersion (4 mg / mL) was mixed at a volume ratio of 1:1 (corresponding to a mass ratio of GO to MXene of approximately 1:2, within the preferred range of 1:1 to 1:3). It was first initially mixed by magnetic stirring for 2 hours, and then ultrasonically treated (power 300W, ultrasonic mode "on for 2 seconds / off for 3 seconds") for 30 minutes to ensure that the two nanosheets were uniformly dispersed and formed a non-agglomerated GO / MXene composite dispersion.

[0042] Crosslinking agent addition: Add 1.5% sodium tetraborate powder (1%-2% of the total mass of the mixture, meeting process requirements) to the above composite dispersion and stir magnetically until completely dissolved. In this step, the borate ions in sodium tetraborate can form reversible borate ester bonds with the hydroxyl groups on the GO surface. On the one hand, this significantly enhances the interaction between GO layers, laying the foundation for high mechanical strength after film formation; on the other hand, the dynamic covalent bonds endow the film with a certain self-healing ability, allowing performance recovery through heating after device damage.

[0043] Film coating: The above composite slurry is coated onto a clean glass plate (temporary substrate) using a blade coating method. The blade coating gap is controlled at 400μm (within the process window of 300~500μm), and the blade moving speed is 15mm / s (within the range of 10-20mm / s). This combination of parameters can balance the uniformity, density and production efficiency of the film, and avoid uneven film thickness due to excessively fast blade coating speed or slurry accumulation due to excessively slow blade coating speed.

[0044] Drying and Thermal Reduction: The coated film was dried in a 60℃ forced-air drying oven for 6 hours to remove the solvent from the dispersion. After drying, the film was peeled off and transferred to a tube furnace. Under argon protection, the temperature was increased to 200℃ at a rate of 5℃ / min and held for 2 hours for thermal reduction treatment. Thermal reduction can remove some oxygen-containing functional groups on the GO surface, improve the electrical conductivity and photothermal properties of the GO / MXene composite material, and further strengthen the interlayer bonding.

[0045] Through the above process, a GO / MXene composite photothermal film with a thickness of 25±3μm was finally obtained. The film has a dense surface, good flexibility and metallic luster. Subsequent tests showed that the synergistic effect of GO and MXene can significantly broaden the absorption range of the solar spectrum, and the photothermal conversion efficiency can reach 85.5%. Moreover, GO can effectively protect MXene from oxidation. After 500 hours of accelerated aging in an environment of 60℃ and 90%RH, the photothermal performance (measured by the time required to reach 80℃) still retains more than 90%, which is far superior to the pure MXene device without GO protection (performance retention rate <50% under the same conditions).

[0046] 2.2 Preparation of thermoelectric layer (Bi2Te3-based thermoelectric thin film);

[0047] Powder mixing and ball milling: Bi₂Te₃ powder and Sb₂Te₃ powder were accurately weighed and mixed at a mass ratio of 19:1. The mixed powder was placed in a ball mill jar and subjected to high-energy ball milling under argon protection (ball-to-powder ratio 15:1, rotation speed 350 rpm, milling time 3 hours). Argon protection prevents powder oxidation, and high-energy ball milling ensures thorough mixing of the two powders, forming a nanocomposite powder with uniform composition and fine particle size, laying the foundation for subsequent densification molding and high-performance thermoelectric properties.

[0048] Densification by spark plasma sintering: The ball-milled nanocomposite powder was loaded into a Φ20mm graphite mold and densified using spark plasma sintering technology under vacuum. The heating rate was controlled at 100℃ / min, and after reaching 420℃, a uniaxial pressure of 50MPa was applied and held at that temperature and pressure for 5 minutes. This rapid hot-pressing process effectively suppresses grain coarsening, ensuring a material density higher than 98%, while simultaneously forming a significantly textured microstructure and improving thermoelectric conversion efficiency.

[0049] Cutting and shaping: The dense thermoelectric bulk obtained by sintering is cut into thin sheets with a thickness of 200μm using a diamond wire cutter. Then, the thin sheets are processed into strips of 10mm×30mm using laser cutting technology (which can be adjusted according to the actual size of the device) to obtain the Bi2Te3-based thermoelectric thin film integrated with the adapter device.

[0050] The prepared Bi2Te3-based thermoelectric thin film exhibits excellent thermoelectric properties. When combined with a photothermal layer and a flexible substrate, it can achieve longitudinal heat conduction and conversion under standard illumination (1000 W / m²). 2 Under these conditions, a stable temperature difference of 45-50℃ can be formed with the photothermal layer, providing a basis for the thermoelectric output of the device; at the same time, the microstructure array formed by laser cutting can enhance the flexibility of the thermoelectric device and adapt to the bending requirements of the overall device.

[0051] 2.3 Preparation of flexible substrate layer (PVA-BNNS composite hydrogel).

[0052] Solution preparation: Add 8g of PVA powder and 2g of BNNS nanosheets to 90g of deionized water (PVA mass fraction 8%, BNNS mass fraction 2%, which meets the mass ratio requirement of 10%-20% for high thermal conductivity fillers). Stir magnetically at 95℃ for 4 hours until PVA is completely dissolved and BNNS is uniformly dispersed to form a uniform and viscous mixed solution.

[0053] Freeze-thaw crosslinking: Pour the above mixed solution into a polytetrafluoroethylene mold, freeze at -20°C for 12 hours, then thaw at room temperature (25°C) for 6 hours. Repeat this freeze-thaw cycle twice. The freeze-thaw process allows PVA molecules to form a stable three-dimensional network of physical crosslinks, while BNNS is uniformly embedded in the network, preventing aggregation.

[0054] The final product is a transparent and flexible PVA-BNNS composite hydrogel film with a thickness of approximately 1 mm. Laser scintillation testing showed that its in-plane thermal conductivity is approximately 1.2 W / (m·K), significantly higher than that of pure PVA hydrogel (thermal conductivity ~0.3 W / (m·K)). This allows for rapid lateral diffusion of heat generated by the photothermal layer, preventing localized overheating. After the device reaches photothermal steady state, the maximum surface temperature difference ΔT < 4.0℃, completely eliminating the risk of burns associated with pure PVA substrate devices (ΔT as high as 22℃). Simultaneously, this composite hydrogel maintains a high water content of 75% and an elongation at break of over 400%, achieving a tensile strength of 2.5 MPa (approximately 1.5 times higher than pure PVA hydrogel). Furthermore, it can achieve self-healing within 5 minutes at 60℃, providing support for the overall mechanical and self-healing properties of the device.

[0055] 2.4 Preparation of electrode layer (carbon cloth electrode);

[0056] Commercial carbon cloth is cut into strips (approximately 3mm wide, adjustable according to the size of the thermoelectric film) that match the width of the thermoelectric film. To remove impurities and oil from the surface of the carbon cloth, it is ultrasonically cleaned in acetone and ethanol for 15 minutes each. After cleaning, it is dried in a 60℃ forced-air drying oven for later use.

[0057] The cleaned carbon cloth surface is clean, and when it is subsequently connected to the thermoelectric layer, it can be tightly bonded by highly conductive silver paste, combined with the fixation of a small amount of epoxy resin glue at the points, to ensure that the interface contact resistance is less than 0.5Ω, thereby achieving efficient and stable electrical signal output and avoiding the attenuation of thermoelectric output power due to excessive contact resistance.

[0058] 2.5 Pre-processing of the encapsulation layer;

[0059] Based on the final integrated size of the device, cut the transparent TPU film into a shape slightly larger than the overall size of the device (leaving a 1-2mm edge to ensure complete coverage of the device) for later use.

[0060] The cut TPU film can be adapted to subsequent thermoforming encapsulation processes of components, with a low water and oxygen permeability (<5g / (m)). 2 •day) can effectively protect the internal functional layers (photothermal layer, thermoelectric layer and electrode layer) from external factors such as moisture, oxygen and ultraviolet rays, and significantly improve the environmental stability and operating life of the device.

[0061] III. Integration and Molding of Flexible Photothermal Devices

[0062] The core of device integration lies in achieving a robust connection and functional synergy between various functional layers. The specific steps are as follows:

[0063] The bonding of the photothermal layer and the flexible substrate: The prepared PVA-BNNS composite hydrogel film (flexible substrate) is laid flat on a glass slide. A small amount of deionized water is sprayed evenly onto the surface of the hydrogel to activate the surface (enhance the hydrogen bonding ability). Then, the GO / MXene composite photothermal film (photothermal layer) is flatly attached to the surface of the hydrogel and gently rolled with a clean roller. The free hydroxyl groups on the surface of the hydrogel form hydrogen bonds with the oxygen-containing functional groups of the nanosheets in the photothermal film to achieve initial adhesion.

[0064] The entire structure was then subjected to another complete freeze-thaw cycle (freezing at -20°C for 12 hours → thawing at 25°C for 6 hours) to create a physically interlocked structure between the hydrogel three-dimensional network and the photothermal film layer, ensuring the stability of the interface under flexible deformation and preventing delamination.

[0065] The combination of thermoelectric layer and photothermal layer: A small amount of high thermal conductivity silicone grease is uniformly coated in the central area of ​​the photothermal layer (to reduce interfacial thermal resistance). The hot end (bottom surface) of the cut Bi2Te3-based thermoelectric film (thermoelectric layer) is tightly attached to the silicone grease layer. Gently press to ensure tight adhesion, so as to achieve efficient heat conduction between the photothermal layer and the thermoelectric layer.

[0066] Connection between electrode layer and thermoelectric layer: The pretreated carbon cloth electrode (electrode layer) is placed in a predetermined area of ​​the cold end (top surface) of the thermoelectric film, and the carbon cloth is bonded to the cold end of the thermoelectric film using flexible conductive silver paste. At the same time, a small amount of epoxy resin is used to fix the lead-out end of the carbon cloth electrode.

[0067] After the silver paste has cured (curing conditions are heating at 80℃ for 10 minutes, which ensures optimal conductivity of the silver paste without damaging the thermosensitive structure of the hydrogel substrate), use a digital multimeter to test the interface contact resistance to ensure that the contact resistance is less than 0.5Ω; finally, solder wires to the lead-out ends of the carbon cloth electrode for subsequent electrical signal output.

[0068] Overall encapsulation: The device with all functional layers integrated (hydrogel side up) is placed in a custom mold, and a pre-treated TPU film is placed over the entire surface of the device. Hot pressing is then performed using a thermopressor, controlling the hot pressing temperature at 120℃, the pressure at 0.3MPa, and the hot pressing time at 60 seconds. These hot pressing parameters allow the TPU molecular chains to effectively diffuse above the glass transition temperature and embed into the hydrogel surface, forming a tight, bubble-free bond and constituting an overall flexible encapsulation structure.

[0069] Through the above integrated process, the functional layers of the device (photothermal layer → thermoelectric layer → flexible substrate layer → electrode layer) are firmly bonded together, and the device maintains excellent flexibility after encapsulation, with a minimum bending radius of 4mm.

[0070] After undergoing 10,000 reciprocating bending tests with a radius of 5 mm, its thermoelectric output power attenuation rate is less than 6%, with no delamination or cracking (far superior to rigid bonded devices, which typically exhibit interface peeling and performance degradation of >20% after 1,000-2,000 bends).

[0071] Meanwhile, the TPU encapsulation layer effectively isolates the device from external environmental corrosion, further improving the device's environmental stability. After 240 hours of aging test, the performance retention rate is >90%.

[0072] IV. Device Performance Testing and Result Analysis

[0073] To verify the function and performance of the device of the present invention, the integrated flexible photothermal device was tested using the following standard test methods, and the results are as follows:

[0074] 4.1 Photothermal performance testing;

[0075] Test method: A solar simulator (xenon lamp, AM1.5G spectrum) calibrated with standard silicon cells was used to provide 1000W / m 2 The incident light intensity was used to irradiate the surface of the photothermal layer of the device (test area size 2cm×2cm).

[0076] A high-precision infrared thermal imager (FLIRA655sc) was used to record the temperature change at the center point of the device surface over time until the temperature stabilized (temperature change <0.5℃ / minute).

[0077] The photothermal conversion efficiency can be calculated using the following formula:

[0078] ;

[0079] Where m is the sample mass. For specific heat capacity, The initial heating rate, For heat loss, Let A be the incident light intensity and A be the light-receiving area.

[0080] Test results: The steady-state temperature of the photothermal layer of the device can reach 83.5℃, and the photothermal conversion efficiency is as high as 85.5%. After 500 hours of accelerated aging in an environment of 60℃ and 90%RH, the photothermal performance retention rate is >90%, which proves its excellent photothermal conversion capability and environmental stability.

[0081] 4.2 Thermal safety management performance test;

[0082] Test method: After the device reaches photothermal steady state, an infrared thermal imager is used to capture the temperature distribution map of the entire device surface, and the highest temperature (T) is extracted. max ) and lowest temperature (T min ), calculate the maximum temperature difference ΔT=T max -T min Simultaneously, the in-plane thermal conductivity of the flexible substrate was tested using the laser flare method.

[0083] Test results: The in-plane thermal conductivity of the flexible substrate (PVA-BNNS composite hydrogel) is about 1.2 W / (m・K), the maximum temperature difference ΔT on the device surface is <4.0℃, and there are no local hot spots. Compared with pure PVA hydrogel substrate devices (ΔT=22℃), this invention completely solves the risk of burns from wearable photothermal devices and meets thermal safety management requirements.

[0084] 4.3 Thermoelectric output performance test;

[0085] Test method: Under standard illumination (1000W / m²) 2 Under these conditions, use a digital source meter (Keithley 2450) to measure the open-circuit voltage (V) of the device. oc ) and short-circuit current (I sc By changing the load resistance and plotting the power curve, the maximum output power (P) can be determined. max Simultaneously, the temperature difference between the photothermal layer and the flexible substrate layer is recorded.

[0086] Test results: The device can generate a stable temperature difference of about 48°C, with an open-circuit voltage of 130mV and a maximum output power of 0.95mW. This power is sufficient to continuously power low-power electronic components (such as temperature and humidity sensors) and achieve self-powering function.

[0087] 4.4 Mechanical durability test;

[0088] Test method: A bending test platform was built using a universal testing machine. The device was repeatedly bent around cylinders of different diameters. The resistance change of the device was monitored online using a digital multimeter, or its thermoelectric output power was measured periodically. The "bending fatigue life" was defined as the number of bends when the performance degraded to 90% of the initial value. The minimum bending radius of the device was also tested.

[0089] Test results: The device has a minimum bending radius of 4mm; after 10,000 reciprocating bending tests with a radius of 5mm, the thermoelectric output power attenuation rate is <6%, and there is no delamination or cracking, proving its excellent flexibility and mechanical durability.

[0090] 4.5 Self-healing performance test;

[0091] Test method: The device (including the flexible substrate layer and the photothermal layer) was completely cut through with a blade, and the cut surfaces were gently aligned and contacted. The device was heated on a 60°C hot table for 5 minutes. After cooling to room temperature, the tensile strength recovery rate of the device was tested using a universal testing machine. At the same time, its photothermal performance recovery rate was verified by photothermal performance testing.

[0092] Test results: The tensile strength of the device can be recovered to more than 85% of the original value, and the photothermal performance recovery rate is >88%, which significantly improves the service life and reliability of the device after accidental damage.

[0093] In summary, this embodiment, through clearly defined raw material specifications, detailed preparation parameters, and a complete integration process, fabricates a flexible photothermal device based on GO / MXene, which possesses excellent photothermal conversion efficiency, thermal safety management capabilities, thermoelectric output performance, mechanical durability, and self-healing properties, as shown in the table below:

[0094]

[0095] It should be noted that, in this invention, although the specification describes the embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A flexible photothermal device based on GOMxene, characterized in that, It includes a photothermal layer, a thermoelectric layer, a flexible substrate layer and an electrode layer stacked in sequence, as well as an encapsulation layer that encapsulates the entire device; The photothermal layer is a composite material layer of graphene oxide (GO) and MXene, the thermoelectric layer is a Bi2Te3-based thermoelectric material layer, the flexible substrate layer is a polymer-based composite material layer containing highly thermally conductive fillers, the electrode layer is a carbon cloth layer, and the encapsulation layer is a thermoplastic polyurethane (TPU) layer.

2. The flexible photothermal device based on GOMxene according to claim 1, characterized in that, In the photothermal layer, the mass ratio of GO to MXene is 1:1 to 1:

3.

3. The flexible photothermal device based on GOMxene according to claim 1, characterized in that, The high thermal conductivity filler in the flexible substrate is boron nitride nanosheets or alumina nanoparticles, and the mass percentage of the high thermal conductivity filler in the flexible substrate is 10%-20%.

4. The flexible photothermal device based on GOMxene according to claim 1, characterized in that, The electrode layer is connected to the thermoelectric layer via flexible conductive silver paste, and the interface contact resistance between the electrode layer and the thermoelectric layer is less than 0.5Ω.

5. A method for fabricating a flexible photothermal device based on GOMxene as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Preparation of photothermal layer: GO dispersion and MXene dispersion are mixed, crosslinking agent is added, and then the mixture is coated, dried and thermally reduced to obtain GO and MXene composite material layer; (2) Preparation of thermoelectric layer: Bi2Te3 powder and Sb2Te3 powder are mixed, ball-milled, densified by spark plasma sintering and cut to obtain Bi2Te3-based thermoelectric material layer; (3) Preparation of flexible substrate layer: The polymer is mixed and dispersed with high thermal conductivity filler, and subjected to freeze-thaw cycle treatment to obtain a polymer-based composite material layer containing high thermal conductivity filler; (4) Device integration and packaging: The photothermal layer, thermoelectric layer, flexible substrate layer and carbon cloth electrode layer prepared in steps (1)-(3) are stacked in sequence. The electrode layer and thermoelectric layer are connected by flexible conductive silver paste. Then, the TPU encapsulation layer is covered by hot pressing to obtain a flexible photothermal device.

6. The method for fabricating a flexible photothermal device based on GOMxene according to claim 5, characterized in that, In step (1), the crosslinking agent is sodium tetraborate, and the amount of the crosslinking agent added is 1%-2% of the total mass of the GO and MXene mixture.

7. The method for fabricating a flexible photothermal device based on GOMxene according to claim 5, characterized in that, In step (2), the mixing mass ratio of Bi2Te3 powder to Sb2Te3 powder is 19:1, the ball-to-material ratio during ball milling is 15:1, and the temperature and pressure of spark plasma sintering are 420℃ and 50MPa.

8. The method for fabricating a flexible photothermal device based on GOMxene according to claim 5, characterized in that, In step (3), the polymer is polyvinyl alcohol, and the number of freeze-thaw cycles is 2, with each freezing time being 12 hours and the thawing time being 6 hours.

9. The method for fabricating a flexible photothermal device based on GOMxene according to claim 5, characterized in that, In step (1), the temperature of thermal reduction is 200℃ and the time is 2 hours; in step (4), the temperature of hot pressing is 120℃, the pressure is 0.3MPa and the time is 60 seconds.

10. An application of the flexible photothermal device based on any one of claims 1-4, characterized in that, The flexible photothermal device is used in wearable self-powered devices to provide continuous power to low-power electronic components.

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