Vanadium dioxide / MXene-based multi-response flexible sensor preparation method

Abstract

The invention relates to the technical field of flexible electronic devices, and discloses a vanadium dioxide / MXene-based multi-response flexible sensor preparation method, which comprises the steps of substrate processing, conductive layer assembling, functional material filling, packaging processing, signal decoupling design and the like. Through regulation and control of a bionic micro-column array structure and a gradient functional material, high-precision detection of temperature, strain and pressure multi-mode signals is realized, the sensitivity reaches 12.8 kPa <-1 >, and the cycle stability exceeds 20,000 times. The photo-thermal regulation and control module and the deep learning algorithm improve the response speed and the recognition accuracy, and the durability is improved through interface combination optimization. Signal crosstalk can be remarkably reduced, the weather resistance and reliability of the sensor are improved, and the long-term use requirement in a complex environment is met.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible electronic devices, and specifically to a method for preparing a multi-responsive flexible sensor based on vanadium dioxide / MXene. Background Art

[0002] As an important sensing device, flexible sensors have broad application prospects in smart wearable devices, health monitoring systems and human-computer interaction. Traditional flexible sensors usually adopt a single-function design and can detect one signal among temperature, strain or pressure. However, there are certain technical challenges in the simultaneous detection of multimodal signals. For example, in the process of realizing the simultaneous detection of temperature, strain and pressure, signal crosstalk is more significant, and the sensitivity is limited (<5 kPa). -1 ), and the problems of slow low-temperature phase transition response (VO2 phase transition hysteresis >10℃) and poor cycle stability (<5000 times) limit its practical application.

[0003] Flexible sensors based on vanadium dioxide (VO2) and MXene are currently attracting widespread attention due to their excellent conductivity and phase change properties. However, existing sensors often lack targeted structural optimization, resulting in insufficient signal decoupling and difficulty meeting high-precision requirements. Furthermore, MXene's easy oxidation in humid environments can cause signal drift (monthly resistance change rate >30%), while a simple mixture of VO2 and MXene can affect response speed and detection range (strain range <40%) due to poor interfacial compatibility (phase separation >5μm).

[0004] Currently, the application scenarios of flexible sensors are developing towards multifunctionality and high performance, especially in wearable devices and complex environment monitoring, which place higher demands on sensor sensitivity, stability, and weather resistance. Traditional design methods still have certain limitations in production efficiency, quality control, and cost. Therefore, it is necessary to develop a method for preparing multi-responsive flexible sensors based on vanadium dioxide / MXene to address these issues and meet practical application needs. Summary of the Invention

[0005] The purpose of the present invention is to propose a method for preparing a multi-responsive flexible sensor based on vanadium dioxide / MXene. By designing a bionic micropillar array structure and a gradient functional material control mechanism, the problems of signal crosstalk, limited sensitivity and poor cyclic stability in traditional flexible sensors in temperature, strain and pressure multimodal signal detection are solved, while at the same time improving the weather resistance and response speed of the sensor.

[0006] The object of the present invention is achieved through the following technical solution: a method for preparing a multi-responsive flexible sensor based on vanadium dioxide / MXene, comprising the following steps:

[0007] Substrate processing: A polyimide film is fixed to a laser engraving platform, and a biomimetic micropillar array structure is formed on its surface using femtosecond laser etching. The micropillars have a diameter of 50μm, a height of 100μm, and a spacing of 80μm. The tops of the micropillars are hemispherical to enhance stress distribution uniformity.

[0008] Conductive layer assembly: A 200nm thick MXene (Ti3C2T5) conductive layer was self-assembled layer by layer on the micropillar surface, with a total of three layers deposited. Vacuum-assisted dip coating was used during the deposition process to ensure uniform coverage of the micropillar surface with MXene and form a continuous conductive network.

[0009] Functional material filling: VO2 nanowire / PEDOT:PSS composite phase change material is injected into the micropillar gaps, with the VO2 nanowires comprising 40wt%. After hydrogen annealing, the VO2 nanowires have a grain size of less than 50nm, and the phase change response time is shortened to 0.3s.

[0010] Packaging: The structure is placed in a hot press mold for hot pressing at 68°C, 10 MPa, and a holding time of 5 minutes. During the hot pressing process, the VO2 nanowires and PEDOT:PSS form an interpenetrating network structure, further enhancing the interfacial bonding strength.

[0011] Signal decoupling design: A bias voltage is applied to the sensor, and the temperature, strain, and pressure signals are distinguished by monitoring the resistance change between the micropillars. The temperature signal is characterized by the resistance jump caused by the VO2 phase transition, with an on / off ratio greater than 10³. The strain and pressure signals are characterized by the change in MXene contact area caused by micropillar deformation, with a sensitivity of 12.8 kPa⁻¹.

[0012] Integrated self-verification mechanism: When the ambient temperature exceeds 68°C, the VO2 phase change triggers the sensor's internal circuit switching, automatically adjusting the pressure detection range from 0-50kPa to 50-200kPa;

[0013] Photothermal control module embedding: A near-infrared laser module with a wavelength of 808nm and a power range of 0.5W / cm² to 1.5W / cm² is embedded in the sensor array. Low-power irradiation activates the temperature sensing channel, while high-power irradiation induces local strain to simulate pressure input.

[0014] Deep learning algorithm deployment: Based on a convolutional neural network, the system dynamically decouples photothermal stimulation and mechanical deformation signals, achieving a recognition accuracy of 98.7%;

[0015] Gradient structure manufacturing: The bottom layer uses electrospun TPU nanofibers loaded with MXene quantum dots, the middle layer is filled with a eutectic mixture of VO2 nanoribbons and liquid metal (EGaIn), and the top layer uses a MXene / silk protein composite transparent electrode with a transmittance greater than 89%;

[0016] Phase-change-induced self-assembly: During hot pressing at 68°C, liquid metal selectively infiltrates the VO2 grain boundaries, forming a reversibly conductive-insulating network. The liquid metal pathways remain stable at low strains (<5%) and reshape at high strains (5-80%).

[0017] Optical-electrical dual signal output: The top electrode undergoes a temperature-triggered transmittance mutation, ΔT = 40%, while the bottom MXene quantum dot tunnel current responds to microstrain signals.

[0018] Interface bonding optimization: Plasma treatment is used to enhance the interface bonding strength between the various layers of materials, ultimately reaching 18.7 MPa, which is five times higher than the traditional mixing method.

[0019] Furthermore, the femtosecond laser etching process parameters described in the step are: laser power of 1W, scan rate of 10mm / s, pulse frequency of 1kHz, and focused spot diameter of 20μm. The surface roughness of the micropillars after etching is controlled within Ra0.2 to ensure uniformity of subsequent MXene deposition.

[0020] Furthermore, the vacuum assisted dip coating method in the step is specifically operated as follows: placing the etched polyimide substrate in a vacuum chamber, evacuating to 10 -2 Pa, followed by the injection of MXene dispersion with a dispersion concentration of 1 mg / mL. The dipping time was 30 minutes, and the vacuum release rate was 0.1 Pa / s to avoid residual bubbles.

[0021] Furthermore, the hydrogen annealing treatment conditions described in the step are as follows: the VO2 nanowires are placed in a tube furnace and heated to 400°C under a hydrogen atmosphere for 2 hours at a heating rate of 5°C / min. After annealing, the VO2 nanowire grain size is controlled within 50nm, and the phase transition response time is shortened to 0.3s.

[0022] Furthermore, the hot pressing mold described in the step comprises two stainless steel templates, the surfaces of which are coated with Teflon to prevent adhesion. A porous gasket is provided inside the mold to discharge gas generated during the hot pressing process to ensure that no bubbles remain inside the composite material.

[0023] Furthermore, the bias voltage is applied by connecting electrodes at both ends of the sensor through silver paste and connecting a constant current source to provide a 10μA bias current. When the bias current flows through the conductive network between the micropillars, the resistance mutation caused by the VO2 phase transition is monitored and recorded in real time.

[0024] Furthermore, the near-infrared laser module described in the steps is mounted as follows: the laser is fixed to a three-dimensional precision translation stage with a displacement accuracy of 1 μm. The laser beam is transmitted to the sensor surface via an optical fiber, with a distance of 5 mm between the fiber port and the sensor surface to ensure that the light spot evenly covers the target area.

[0025] Furthermore, the convolutional neural network model described in the step includes three convolutional layers and two fully connected layers. The input data is the resistance change signal collected by the sensor array. The model training data set contains 10,000 sets of samples, and the test set accuracy rate reaches 98.7%.

[0026] Furthermore, the electrospinning process parameters described in the step are: spinning voltage of 15 kV, receiving distance of 15 cm, and spinning rate of 0.5 mL / h. The diameter of the TPU nanofibers is controlled within 500 nm, and the MXene quantum dots are 3-5 nm in size and evenly distributed on the fiber surface.

[0027] Furthermore, the plasma treatment conditions described in the step are as follows: the gradient structure is placed in an oxygen plasma treatment chamber, the radio frequency power is 100W, the treatment time is 5 minutes, and the working gas is oxygen at a flow rate of 50sccm. After treatment, the interface bonding strength reaches 18.7MPa, which is 5 times higher than that of the untreated sample.

[0028] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0029] The bionic micro-pillar array structure significantly improves the sensor's signal decoupling capability, with the decoupling error of temperature, strain, and pressure signals less than 5%. The temperature detection accuracy is ±0.5°C (30-100°C), the strain detection limit is 0.05%, and the pressure sensitivity is increased to three times that of conventional sensors (12.8 kPa). -1 );

[0030] The micro-pillar structure buffers external stress concentration, and the sensor's cycle stability exceeds 20,000 times, far exceeding the 5,000 times of traditional designs;

[0031] The photothermal control module achieves hardware-level perception mode reconstruction. The switching response time between temperature, pressure, and photothermal stimulation modes is less than 0.5s, and the photothermal response sensitivity reaches 1.2% / mW, far exceeding the conventional thermal response of 0.3% / mW.

[0032] The gradient structure design expands the strain detection range to 0.01%-80%, significantly improving the response speed, with a temperature response time of 0.2s and a strain recovery time of 0.15s;

[0033] The optical-electrical dual signal output mechanism provides redundant detection means, and the resistance variation range is 103 Ω, the transmittance change is 40%, which enhances the reliability of the sensor;

[0034] Interface optimization significantly improves the durability of the sensor. After aging for 1000 hours at 85°C / 85%RH, the performance degradation is less than 8%, meeting the needs of long-term use in complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a block diagram of the overall structural design of the sensor in an embodiment of the present invention;

[0036] Figure 2 This is a block diagram of the bionic micro-pillar array structure in an embodiment of the present invention;

[0037] Figure 3 This is a flowchart of the preparation process of the MXene conductive layer in an embodiment of the present invention;

[0038] Figure 4 This is a block diagram for preparing the VO2 nanowire / PEDOT:PSS composite phase change material according to an embodiment of the present invention;

[0039] Figure 5 This is a block diagram of the hot pressing molding structure in an embodiment of the present invention;

[0040] Figure 6 This is a block diagram of the design of the photothermal control module in an embodiment of the present invention;

[0041] Figure 7 This is a block diagram of the functional gradient material layer structure in an embodiment of the present invention;

[0042] Figure 8 This is a block diagram of the design of the optical-electrical dual-signal output electrode in an embodiment of the present invention. DETAILED DESCRIPTION

[0043] The following will clearly and completely describe the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0044] The present invention provides a method for preparing a multi-responsive flexible sensor based on vanadium dioxide / MXene. Figure 1 -Attached Figure 8 Detailed description is given. Figure 1The overall structural design of the sensor was demonstrated, including a bionic micropillar array, a MXene conductive layer, a VO2 nanowire / PEDOT:PSS composite phase change material, a hot-pressed molding structure, a near-infrared laser module, a gradient functional material layer, and an optical-electrical dual-signal output electrode.

[0045] First, during the substrate processing process, a bionic micropillar array is formed on the surface of the polyimide film using femtosecond laser etching technology. The micropillars have a diameter of 50μm, a height of 100μm, a spacing of 80μm, and a hemispherical top to optimize stress distribution. The femtosecond laser etching process parameters are set to a laser power of 1W, a scanning rate of 10mm / s, a pulse frequency of 1kHz, and a focused spot diameter of 20μm. After etching, the surface roughness of the micropillars is controlled within Ra0.2 to ensure uniform coverage of the subsequent MXene conductive layer. The structural design of the bionic micropillar array effectively alleviates external stress concentration through the gaps between the micropillars and the hemispherical top design, providing a foundation for subsequent functional material filling and signal decoupling.

[0046] Next, the MXene conductive layer was assembled layer by layer on the surface of the biomimetic micropillar array. The MXene conductive layer was deposited by vacuum-assisted dip coating, with each layer having a thickness of 200 nm and a total of 3 layers deposited. The specific operation of the vacuum-assisted dip coating method is to place the etched polyimide substrate in a vacuum chamber and evacuate to 10 -2 Pa, followed by the injection of a MXene dispersion at a concentration of 1 mg / mL. The dipping time was 30 minutes, and the vacuum release rate was 0.1 Pa / s to prevent air bubbles from accumulating. The MXene conductive layer evenly covered the surface of the biomimetic micropillar array, forming a continuous conductive network. This conductive network not only serves as a core component for strain and pressure signal sensing but also provides a stable interface support for the subsequent embedding of the composite phase change material.

[0047] A VO2 nanowire / PEDOT:PSS composite phase-change material was injected into the gaps between the micropillars. The VO2 nanowires comprised 40% by weight of the composite phase-change material and were hydrogen annealed to optimize their performance. The hydrogen annealing treatment involved placing the VO2 nanowires in a tube furnace and heating them to 400°C in a hydrogen atmosphere for two hours at a heating rate of 5°C / min. After annealing, the VO2 nanowire grain size was controlled within 50nm, and the phase change response time was shortened to 0.3s. The VO2 nanowire / PEDOT:PSS composite phase-change material forms close contact with the MXene conductive layer by filling the gaps between the micropillars, and its phase change properties provide key support for temperature signal detection.

[0048] After the functional material filling is completed, the above structure is placed in a hot pressing mold for hot pressing to form a hot pressing molded structure. The hot pressing temperature is 68°C, the pressure is 10MPa, and the holding time is 5 minutes. The hot pressing mold consists of two upper and lower stainless steel templates. The surface of the template is coated with Teflon coating to prevent adhesion. A porous breathable gasket is provided in the mold to discharge the gas generated during the hot pressing process to ensure that there are no bubbles remaining inside the composite material. During the hot pressing process, VO2 nanowires and PEDOT:PSS form an interpenetrating network structure, further enhancing the interface bonding strength. The formation of the hot pressing molded structure enables the functional material layers to be tightly combined, laying the foundation for the subsequent signal decoupling and self-verification mechanism.

[0049] The sensor's signal decoupling design is achieved by applying a bias voltage. The bias voltage is applied by connecting electrodes at both ends of the sensor through silver paste and connecting a constant current source to provide a 10μA bias current. When the bias current passes through the conductive network between the micropillars, the resistance mutation caused by the VO2 phase transition is monitored and recorded in real time. The temperature signal is characterized by the resistance mutation caused by the VO2 phase transition, and the on-off ratio is greater than 10 3 The strain and pressure signals are characterized by the change in MXene contact area caused by micropillar deformation, with a sensitivity of 12.8 kPa. -1 This signal decoupling design distinguishes temperature, strain, and pressure signals through the changing characteristics of different physical quantities, significantly reducing signal crosstalk.

[0050] A self-verification mechanism is integrated into the sensor's internal circuitry. When the ambient temperature exceeds 68°C, a VO2 phase change triggers a switch in the sensor's internal circuitry, automatically adjusting the pressure detection range from 0-50kPa to 50-200kPa. This mechanism, combining the VO2 phase change characteristics with circuit design, enables dynamic adjustment of the pressure detection range at the hardware level, enhancing the sensor's adaptability in complex environments.

[0051] The photothermal control module is embedded in the sensor array, with a wavelength of 808nm and a power range of 0.5W / cm 2 Up to 1.5W / cm 2 . The near-infrared laser module is installed in such a way that the laser is fixed on a three-dimensional precision displacement stage with a displacement accuracy of 1μm. The laser beam is transmitted to the sensor surface through an optical fiber. The distance between the optical fiber port and the sensor surface is 5mm, ensuring that the light spot evenly covers the target area. Low-power irradiation activates the temperature sensing channel, and high-power irradiation induces local strain to simulate pressure input. The photothermal control module realizes the hardware-level reconstruction of multimodal signal detection through the synergistic effect of photothermal effect and mechanical deformation signal.

[0052] A deep learning algorithm, deployed in the sensor signal processing phase, dynamically decouples photothermal stimulation from mechanical deformation signals using a convolutional neural network. The convolutional neural network model consists of three convolutional layers and two fully connected layers, and its input data is the resistance change signals collected by the sensor array. The model training dataset contains 10,000 samples, and the test set accuracy reaches 98.7%. Through extensive data training, the deep learning algorithm achieves efficient recognition and classification of complex signals, providing software-level support for multimodal sensor signal detection.

[0053] The functional gradient material layer is designed to consist of a bottom layer, a middle layer, and a top layer. The bottom layer utilizes electrospun TPU nanofibers loaded with MXene quantum dots, the middle layer is filled with a eutectic mixture of VO2 nanoribbons and liquid metal (EGaIn), and the top layer utilizes a MXene / silk protein composite transparent electrode with a transmittance exceeding 89%. The electrospinning process parameters are a spinning voltage of 15 kV, a receiving distance of 15 cm, and a spinning rate of 0.5 mL / h. The diameter of the TPU nanofibers is kept within 500 nm, and the MXene quantum dots are 3-5 nm in size and evenly distributed across the fiber surface. The functional gradient material layer achieves an expanded strain detection range and improved signal response speed through a layered design of different materials.

[0054] Phase-change-induced self-assembly is achieved during hot pressing at 68°C. Liquid metal selectively infiltrates the VO2 grain boundaries, forming a reversibly conductive-insulating network. The liquid metal pathways remain stable at low strains (<5%) and reconfigure at high strains (5-80%). This self-assembly mechanism leverages the material's inherent physical properties to dynamically adjust the conductive network, ensuring the sensor's high sensitivity and wide detection range.

[0055] The design of dual optical and electrical output electrodes enables redundant detection capabilities in the sensor. The top electrode undergoes a temperature-triggered sudden change in transmittance, reaching ΔT = 40%, while the underlying MXene quantum dot tunneling current responds to microstrain signals. This dual-signal output mechanism enhances sensor reliability through the synergistic effect of optical and electrical signals, providing multiple safeguards for signal detection in complex environments.

[0056] Interface bonding optimization is achieved through plasma treatment. The gradient structure was placed in an oxygen plasma treatment chamber with an RF power of 100W and a treatment time of 5 minutes. The working gas was oxygen at a flow rate of 50 sccm. After treatment, the interface bonding strength reached 18.7 MPa, a five-fold increase compared to the untreated sample. Interface bonding optimization significantly improved the durability of the sensor, resulting in a performance degradation of less than 8% after aging for 1000 hours at 85°C / 85% RH, meeting the requirements for long-term use in complex environments.

[0057] The above embodiments describe in detail the fabrication process and operating principles of a multi-responsive flexible sensor based on vanadium dioxide / MXene. Through the synergistic effects of a biomimetic micropillar array, a MXene conductive layer, a VO2 nanowire / PEDOT:PSS composite phase change material, a hot-pressed structure, a near-infrared laser module, a gradient functional material layer, and optical-electrical dual-signal output electrodes, it achieves efficient decoupling and precise detection of temperature, strain, and pressure signals.

[0058] In order to better enable relevant personnel in this technical field to fully understand and implement the present invention, the specific implementation principle of the present invention is further supplemented below with reference to a specific application scenario.

[0059] First, in smart wearable devices, flexible sensors need to simultaneously detect body temperature, strain generated by joint bending, and pressure signals from external pressure. When the sensor is attached to the surface of human skin, the biomimetic micropillar array effectively disperses external stress concentration through its top hemispherical design and gap structure. When the human joint bends, the spacing between the micropillars changes, and the contact area of ​​the MXene conductive layer changes accordingly. Due to the high conductivity of MXene, its resistance change can accurately reflect the strain signal. At the same time, the VO2 nanowire / PEDOT:PSS composite phase change material fills the gaps between the micropillars, forming a close contact with the MXene conductive layer. When the human body temperature rises to around 68°C, the VO2 nanowires undergo a phase change, and their resistance mutation provides a key representation of the temperature signal.

[0060] Next, the hot-pressed structure ensures a tight bond between the functional material layers. In practical applications, the sensor may be subject to external pressure. When pressure is applied to the sensor surface, the bionic micropillar array deforms, causing the contact area of ​​the MXene conductive layer to further change. This change is monitored in real time via the bias current, enabling the distinction between strain and pressure signals. In addition, when the ambient temperature exceeds 68°C, the VO2 phase change triggers the switching of the sensor's internal circuit, automatically adjusting the pressure detection range. This mechanism enables the sensor to adapt to different pressure ranges in complex environments through dynamic adjustment at the hardware level.

[0061] The photothermal control module plays a crucial role in multimodal signal detection. When the near-infrared laser module illuminates the sensor surface at low power, the photothermal effect activates the temperature sensing channel, enabling temperature signal acquisition by monitoring the local temperature rise. When the laser power is increased, local thermal expansion induces deformation of the micropillars, simulating a pressure input signal. This synergistic effect of the photothermal effect and the mechanical deformation signal provides the sensor with hardware-level multimodal signal reconstruction capabilities.

[0062] The design of the gradient functional material layer further enhances the sensor's performance. In the bottom layer, electrospun TPU nanofibers are loaded with MXene quantum dots, and the evenly distributed quantum dots enhance the stability of the conductive network. The middle layer, filled with a eutectic mixture of VO2 nanoribbons and liquid metal, selectively infiltrates the VO2 grain boundaries during hot pressing, forming a reversibly conductive-insulating network. This self-assembly mechanism ensures sensor stability under microstrain conditions, while the conductive network reshapes under high strain, achieving a wide detection range and high sensitivity.

[0063] The design of the dual-signal optical and electrical output electrodes provides the sensor with redundant detection capabilities. When the top electrode experiences a sudden change in transmittance due to temperature fluctuations, the 40% change in ΔT can be captured by the optical sensor. Simultaneously, the tunneling current of the underlying MXene quantum dots responds to microstrain signals. The synergistic effect of these two signals enhances the sensor's reliability in complex environments. For example, in humid environments, interface optimization through plasma treatment significantly improves the sensor's durability, resulting in performance degradation of less than 8% after 1000 hours of aging at 85°C / 85% RH.

[0064] The above steps detail the operating principles of a vanadium dioxide / MXene-based multi-responsive flexible sensor in specific application scenarios. Through the synergistic effects of a biomimetic micropillar array, a MXene conductive layer, a VO2 nanowire / PEDOT:PSS composite phase change material, a hot-pressed structure, a near-infrared laser module, a gradient functional material layer, and optical-electrical dual-signal output electrodes, the sensor efficiently decouples and accurately detects temperature, strain, and pressure signals, meeting the multifunctional requirements of complex environments.

[0065] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a multi-responsive flexible sensor based on vanadium dioxide / MXene, characterized in that: The steps include: Step 1: Substrate processing: A polyimide film is fixed on a laser engraving platform, and a bionic micropillar array is formed on its surface by femtosecond laser etching. The micropillars have a diameter of 50 μm, a height of 100 μm, a spacing of 80 μm, and a hemispherical top. Step 2: Conductive layer assembly: Self-assemble the MXene conductive layer layer by layer on the surface of the bionic micropillar array, with each layer having a thickness of 200 nm, and deposit three layers in total. The vacuum-assisted dip coating method is used during the deposition process. Step 3: Filling the gaps between the biomimetic micropillar arrays with functional materials: injecting VO2 nanowires / PEDOT:PSS composite phase change material, with VO2 nanowires accounting for 40wt%; Step 4: Packaging treatment: Place the above structure in a hot pressing mold for hot pressing molding. The hot pressing temperature is 68°C, the pressure is 10MPa, and the holding time is 5 minutes. Step 5: Gradient structure fabrication: The bottom layer uses electrospun TPU nanofibers loaded with MXene quantum dots, the middle layer is filled with a mixture of VO2 nanoribbons and liquid metal eutectic, and the top layer uses a MXene / silk protein composite transparent electrode with a transmittance greater than 89%; Step 6: Phase change-induced self-assembly: During the hot pressing process at 68°C, liquid metal selectively penetrates the VO2 grain boundaries to form a conductive-insulating reversible conversion network; Step 7: Optical-electrical dual signal output: The top electrode undergoes a sudden change in transmittance under temperature triggering, ΔT = 40%, while the tunnel current of the bottom MXene quantum dots responds to microstrain signals; Step 8: Interface bonding optimization: Enhance the interface bonding strength between each layer of material through plasma treatment.

2. The method for preparing a multi-responsive flexible sensor based on vanadium dioxide / MXene according to claim 1, characterized in that: The femtosecond laser etching process parameters in step 1 are: laser power of 1 W, scanning rate of 10 mm / s, pulse frequency of 1 kHz, focused spot diameter of 20 μm, and the surface roughness of the microcolumns after etching is controlled within Ra0.

2.

3. The method for preparing a multi-responsive flexible sensor based on vanadium dioxide / MXene according to claim 1, characterized in that: The specific operation of the vacuum-assisted dip coating method in step 2 is: placing the etched polyimide substrate in a vacuum chamber, evacuating to 10 -2 Pa, and then the MXene dispersion was injected, the dispersion concentration was 1 mg / mL, the dipping time was 30 min, and the vacuum release rate was 0.1 Pa / s.

4. The method for preparing a multi-responsive flexible sensor based on vanadium dioxide / MXene according to claim 1, characterized in that: In step 3, the VO2 nanowires are subjected to hydrogen annealing treatment. The hydrogen annealing conditions are as follows: the VO2 nanowires are placed in a tubular furnace and heated to 400°C in a hydrogen atmosphere for 2 hours at a heating rate of 5°C / min. After annealing, the grain size of the VO2 nanowires is controlled within 50nm.

5. The method for preparing a multi-responsive flexible sensor based on vanadium dioxide / MXene according to claim 1, characterized in that: The hot pressing mold in step 4 includes two upper and lower stainless steel templates, the surfaces of the templates are coated with Teflon coating, and a porous breathable gasket is provided in the mold to discharge the gas generated during the hot pressing process.

6. The method for preparing a multi-responsive flexible sensor based on vanadium dioxide / MXene according to claim 1, characterized in that: The electrospinning process parameters in step 5 are: spinning voltage of 15 kV, receiving distance of 15 cm, spinning rate of 0.5 mL / h, TPU nanofiber diameter controlled within 500 nm, and MXene quantum dot size of 3-5 nm.

7. The method for preparing a multi-responsive flexible sensor based on vanadium dioxide / MXene according to claim 1, characterized in that: The plasma treatment conditions in step eight are as follows: placing the gradient structure in an oxygen plasma treatment chamber, the radio frequency power is 100 W, the treatment time is 5 minutes, the working gas is oxygen, and the flow rate is 50 sccm.

8. The method for preparing a multi-responsive flexible sensor based on vanadium dioxide / MXene according to claim 1, characterized in that: In the optical-electrical dual signal output mechanism in step 7, the transmittance of the top electrode varies in the range of 40%, and the tunnel current response microstrain signal of the bottom MXene quantum dots varies in the range of 10 3 Ω.

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