A method of manufacturing a microstructured tpu-based composite and pressure sensing applications

Abstract

This invention discloses a method for preparing a microstructured TPU-based composite material and its pressure sensing application. The PDMS-MCTT composite material is prepared using an electrospinning process. Under a high-voltage electrostatic field, a metal mesh template receiver is used as the current collector, guiding the electrospun fibers to preferentially accumulate at this point, creating a thickness difference and ultimately forming a unique micro-hemispherical structure. A template-guided TPU fabric substrate layer with a surface microstructure is then prepared. MXene@CNTs conductive material is loaded onto this substrate layer to obtain an MXene@CNTs / TT conductive fabric. This sample is then encapsulated with PDMS to obtain the PDMS-MCTT composite material. Finally, the two composite layers are assembled and sewn together to construct a double-layer PDMS-MCTT fabric-based pressure sensor. This provides a larger contact area and greater interlayer void distance within the fabric, thereby achieving a larger resistance change under the same pressure. The double-layer PDMS-MCTT fabric sensor exhibits excellent sensitivity in the field of fabric-based flexible pressure sensing and has great application potential in motion detection and health management.

Description

Technical Field

[0001] This invention relates to the field of flexible sensing, and more particularly to a method for preparing a microstructured TPU-based composite material and its pressure sensing application. Background Technology

[0002] With the development of the Internet of Things (IoT) and the rise of the concept of interconnected everything, wearable sensors, as mobile terminals, are booming and possess enormous market value. Simultaneously, as living standards improve, people's demands for textiles are gradually shifting from basic needs like warmth and cover to demands for aesthetics and comfort, and are moving towards intelligence and multifunctionality. Human body signals can be broadly categorized into sound, temperature, physiological signals, motion trajectories, and static postures. Wearable sensing devices use non-invasive methods to continuously collect these signals on the human body surface over long periods, achieving significant progress in health monitoring, disease diagnosis, human-computer interaction, motion detection, and posture correction. However, traditional rigid sensors made of metal or semiconductor materials are hard and heavy, resulting in poor fit with the curved surfaces of the human body when identifying physiological and motion signals, leading to unsatisfactory wearing comfort; moreover, the signal-to-noise ratio of the collected signals is unstable, and signal accuracy cannot be guaranteed. Therefore, using flexible and easily modifiable fabric-based sensors to accurately identify human physiological and motion signals is of great significance.

[0003] To achieve different functions for various applications and enable flexible fabric-based pressure sensors to more accurately and sensitively identify stress, microstructure design of the sensing layer can be performed while selecting and optimizing the spatial structure of the substrate fabric. The introduction of surface microstructures can concentrate internal stress, improve compressibility, and alter the internal contact area, allowing the fabric-based pressure sensor to generate sufficient changes and signals even under minute pressure. Therefore, designing a novel and specialized surface microstructure fabrication method is essential for improving the sensitivity and accuracy of fabric-based sensors and effectively expanding their application range.

[0004] Since the successful synthesis of Ti3C2Tx in 2011, two-dimensional transition metal carbides / nitrides (MXenes) have attracted considerable attention. MXenes possess advantages such as high conductivity, high specific surface area, good liquid-phase dispersibility, and sensitive response to external pressure, making them one of the ideal materials for constructing conductive layers in fabric-based pressure sensors. However, conductive layers composed of MXene alone are limited by the insufficient stability of the bonding between MXene sheets, making it impossible to withstand excessive pressure while maintaining the overall structure. One-dimensional carbon nanotubes (CNTs), due to their tortuous tubular structure, allow CNTs to become entangled in conductive layers, enabling reversible deformation of the CNT conductive layer under pressure to stabilize the network and significantly improving the pressure sensing range. Therefore, efficiently and conveniently combining MXenes and CNTs on fabric substrates to construct composite conductive networks is of great significance for preparing fabric-based pressure sensors with both high sensitivity and a wide sensing range.

[0005] Furthermore, since the conductive layer of wearable sensors is energized during operation, the infiltration of liquids such as sweat can severely interfere with the sensor's stability and even damage the conductive layer. Therefore, adding hydrophobicity can ensure the performance stability of fabric-based pressure sensors during operation. Maintaining the breathability of the fabric substrate itself while achieving high-performance pressure sensing is crucial for the practical application of fabric-based pressure sensors. However, achieving a fabric-based pressure sensor that maintains the characteristics of the fabric substrate while possessing high sensitivity, a wide sensing range, and hydrophobic properties remains a challenge.

[0006] Chinese invention patent CN113667178B discloses a flexible, biodegradable microchannel pressure sensing material and its preparation method. Chinese invention patent CN114184307A discloses a microstructured flexible pressure sensor. Chinese invention patent CN110186600B discloses a method for preparing a self-supporting thin film and a pressure sensing actuator. Chinese invention patent CN114739449B uses 3D printing technology to construct a pressure sensing matrix of a flexible porous material structure. It is evident that there are few methods for preparing composite materials with highly sensitive pressure sensing capabilities that design the surface microstructure of flexible fabric-based sensors and possess both breathability and hydrophobicity. Summary of the Invention

[0007] This invention overcomes the shortcomings of existing technologies and provides a method for preparing materials with extremely high sensitivity (S max =471.3 kPa -1The method of constructing a fabric-based pressure sensor based on the PDMS-MCTT composite material with special surface micro-hemispherical structure was presented, and the application potential of the fabric-based pressure sensor constructed based on the PDMS-MCTT composite material in motion detection and health management was demonstrated.

[0008] To achieve the above objectives, the technical solution adopted in this invention is as follows: PDMS-MCTT composite material is produced using an electrospinning process. Under the action of a high-voltage electrostatic field, a metal mesh template receiver is used as a collector to receive fibers generated by the spinneret with opposite charges. Due to the presence of the mesh structure on the metal mesh template, the charges are unevenly distributed, with the charges being more concentrated in the hollow parts of the mesh. This guides the electrospun fibers to preferentially accumulate in these areas, resulting in thickness differences and ultimately forming a special micro-hemispherical structure. This allows the preparation of a template-guided TPU fabric (TT) substrate layer with a surface microstructure. MXene@CNTs conductive material is loaded onto this substrate layer to obtain MXene@CNTs / TT conductive fabric (MCTT). The sample is then encapsulated with PDMS to obtain the PDMS-MCTT composite material. Finally, the two composite materials are assembled and sewn together to construct a double-layer PDMS-MCTT fabric-based pressure sensor.

[0009] The first technical problem solved by this invention is to provide a method for preparing a TT substrate layer with a unique surface micro-hemispherical structure by template-guided electrospinning.

[0010] The method for preparing the TT substrate layer of the present invention includes the following steps:

[0011] S1. Fix a metal wire mesh template of a certain mesh size onto an insulating rubber board and ground it through conductive grounding to form a metal wire mesh receiver;

[0012] S2. Prepare an electrospinning precursor solution of a certain concentration by mixing TPU particles and N,N-dimethylformamide (DMF) solution in a certain proportion;

[0013] S3. Select a needle of a certain size, and perform electrospinning using an electrospinning precursor solution according to certain spinning parameters. After spinning, remove the TT substrate and dry it in an oven to obtain the TT substrate.

[0014] In a preferred embodiment of the present invention, in step S1, the metal mesh template is 20-80 mesh; and in step S2, the concentration of the prepared precursor solution is 16-18 wt%.

[0015] In a preferred embodiment of the present invention, in step S3, the spinning parameters are: spinning voltage 12-16kV, feed speed 0.7mL / h, and spinning time 0.5-2h.

[0016] The second technical problem solved by this invention is to propose a method for preparing a double-layer PDMS-MCTT fabric-based pressure sensor.

[0017] The method for fabricating the double-layer PDMS-MCTT fabric-based pressure sensor of the present invention includes the following steps:

[0018] S11. Prepare an MXene@CNTs mixed solution by mixing MXene, water-based CNTs slurry and water in a certain proportion;

[0019] S12. Take 20 mL of MXene@CNTs mixed solution, cut the TT substrate layer prepared above to a suitable size and put it into the MXene@CNTs mixed solution, perform ultrasonic-assisted dip coating and drying, repeat the dip coating and drying steps several times to obtain MCTT fabric.

[0020] S13. PDMS is diluted with n-hexane to prepare a PDMS / n-hexane solution of a certain concentration. MCTT fabric is immersed in the PDMS / n-hexane solution and left to stand for a period of time. Then, it is taken out and dried in an oven to completely evaporate the n-hexane, thus obtaining PDMS-MCTT fabric.

[0021] S14. Place two layers of PDMS-MCTT fabric facing each other, so that the micro-hemispherical structures on the two layers of PDMS-MCTT fabric come into contact with each other and are sewn together. Finally, use two copper foils as electrodes and use conductive silver paste to bond them to the outside of the two PDMS-MCTT fabrics. Then put them into an oven to cure the silver paste to obtain a double-layer PDMS-MCTT fabric-based pressure sensor.

[0022] In a preferred embodiment of the present invention, in step S11, the mass ratio of MXene to the aqueous CNTs slurry is 1:1 to 3.

[0023] In a preferred embodiment of the present invention, in step S12, the ultrasonic-assisted dip coating time is 5 to 30 minutes, and the dip coating and drying steps are repeated 1 to 5 times.

[0024] In a preferred embodiment of the present invention, in step S13, the concentration of the PDMS / n-hexane solution is 8-15 wt%, and the standing time is 5-30 min.

[0025] In one specific embodiment of the present invention, the MXene preparation method includes the following steps:

[0026] S21. Take HCl solution and add LiF and stir to obtain etching solution. Add 1g of Ti3AlC2 to the etching solution and stir in a water bath at 37℃ for 24-36h to obtain the etched multilayer MXene solution.

[0027] S22. Wash the multilayer MXene solution with water by centrifugation multiple times, take the lower layer precipitate, and sonicate it in an ice bath for 1 hour. After sonication, centrifuge the MXene solution at 3500 rpm for 30 minutes and take the upper layer of MXene solution.

[0028] In a preferred embodiment of the present invention, specifically, in step S21, 20 mL of 9 mol / L HCl solution is taken, 1.5 g of LiF is added, and the mixture is slowly stirred for 5-10 min to obtain an etching solution. 1 g of Ti3AlC2 is added to the etching solution, and the mixture is stirred in a water bath at 37°C for 24-36 h to obtain an etched multilayer MXene solution. In step S22, the multilayer MXene solution is washed with water, and the washed multilayer MXene solution is centrifuged at 8000 rpm for 5 min, repeated 5-7 times. The lower layer precipitate is taken until the pH value of the supernatant is greater than 6. The washed multilayer MXene solution is ultrasonically dispersed in an ice bath for 1 h, and the ultrasonically dispersed MXene solution is centrifuged at 3500 rpm for 30 min. The upper layer of lesser MXene solution is taken.

[0029] This invention provides the application of the aforementioned dual-layer PDMS-MCTT fabric-based pressure sensor in the fields of motion detection and health management.

[0030] The dual-layer PDMS-MCTT fabric-based pressure sensor described in this invention exhibits excellent sensing performance and demonstrates extremely high sensitivity (S). max =471.3 kPa -1 It is breathable and hydrophobic. As a wearable flexible sensor, it can fit well with the human body, provide timely and accurate feedback on the body's state during exercise, and monitor physiological activities such as pulse, breathing, and swallowing in real time.

[0031] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0032] (1) This invention uses electrospinning process. Under the action of high voltage electrostatic field, a metal wire mesh template receiver is used as the collector to receive the fibers generated by the spinneret with opposite charge. Because of the existence of the grid structure on the metal wire mesh template, the charge will be unevenly distributed. The charge is more concentrated in the hollow part of the grid, which guides the electrospun fibers to accumulate preferentially here, resulting in thickness difference and finally forming a special micro-hemispherical structure. The micro-hemispherical structure provides a larger contact area and interlayer gap distance for the double-layer PDMS-MCTT fabric sensor, thereby achieving a larger resistance change under the same pressure, and optimizing the sensitivity and pressure response range of the sensor.

[0033] (2) In this invention, MXene and CNTs composites are selected to give full play to the advantages of each component and achieve physicochemical properties that cannot be achieved by a single component. The MXene@CNTs conductive material is loaded onto the TT substrate layer with a unique surface micro-hemispherical structure prepared by template-guided electrospinning using a convenient and simple ultrasonic-assisted dip-coating method. This can achieve the synergistic enhancement effect of highly sensitive conductive material and surface microstructure with rapid pressure response. The MXene@CNTs hybrid conductive layer has the high sensitivity brought by the MXene sheet structure. At the same time, due to the doping of CNTs, the strength of the entire conductive layer is enhanced, so that the conductive layer will not undergo irreversible deformation under high pressure, thereby improving the pressure sensing range of the sensor.

[0034] (3) In this invention, TPU particles are combined with DMF solution to prepare an 18wt% electrospinning precursor solution, which can form continuous fibers, enhance the ability of fibers to accumulate on the metal wire mesh template and form hemispherical protrusions, increase the deposition efficiency and distribution uniformity of fibers on the metal wire mesh, and by using a 60-mesh metal wire mesh template as the collector, a micro-hemispherical structure of moderate size and uniform distribution can be formed, thereby optimizing the sensitivity and pressure response range of the prepared double-layer PDMS-MCTT fabric-based pressure sensor.

[0035] (4) The dual-layer PDMS-MCTT fabric sensor in this invention exhibits excellent sensitivity (S) in the field of fabric-based flexible pressure sensing. max =471.3 kPa -1 It features a wide pressure sensing range (0-521.6 kPa), a low minimum detection limit (0.003 kPa), a fast response time, and stable cyclic pressure performance. In addition, the double-layer PDMS-MCTT fabric provides excellent sensing performance while also being breathable and hydrophobic (contact angle of 132.7°). Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1This is a group of images of the surface and cross-section (jk) of the PDMS-MCTT fabric in Embodiment 1 of the present invention, the surface and cross-section (ab) of the pure TPU fabric, the surface and cross-section (de) of the TT fabric, and the surface and cross-section (f) of the MCTT fabric.

[0038] Figure 2 This is a schematic diagram of the micro-hemispherical structure of the double-layer PDMS-MCTT fabric-based pressure sensor in Embodiment 1 of the present invention;

[0039] Figure 3 Here are (a) SEM images and corresponding EDS spectra of the PDMS-MCTT fabric in Embodiment 1 of the present invention: (b) C, (c) O, (d) Ti, (e) F, (f) Si;

[0040] Figure 4 This is a digital image of the water contact angle (132.7°) of the double-layer PDMS-MCTT fabric-based pressure sensor in Embodiment 1 of the present invention;

[0041] Figure 5 The pressure-ΔI / I0 curves are those of the double-layer PDMS-MCTT fabric-based pressure sensor (a) in Embodiment 1 of the present invention and the double-layer PDMS-MCTPU / MCTPU fabric-based pressure sensor (b) without micro-hemispherical structure in Comparative Example 3.

[0042] Figure 6 The curves of the double-layer PDMS-MCTT fabric-based pressure sensor in Embodiment 1 of the present invention are the "time-ΔI / I0" curves in (a) micro pressure range, (b) small pressure range, (c) medium pressure range and (d) large pressure range. Detailed Implementation

[0043] 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.

[0044] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0045] It should be noted that the raw materials, equipment and reagents used in this invention can all be purchased from the market or obtained through existing preparation methods.

[0046] A PDMS-MCTT composite material is provided, which uses a TPU fabric with a micro-hemispherical structure prepared by template-guided spinning as the base layer, and encapsulates it with MXene@CNTs conductive material to form a stable structure.

[0047] It should be noted that this PDMS-MCTT composite material uses an ultrasonic-assisted method to load an MXene@CNTs conductive layer onto the micro-hemispherical structure of the TT substrate, followed by PDMS encapsulation. This composite material exhibits excellent conductivity and good piezoresistive variation capability due to the synergistic enhancement of the highly sensitive conductive material and the surface micro-hemispherical structure with rapid pressure response. Simultaneously, this composite material retains the air permeability of the flexible fabric while also possessing hydrophobicity, allowing for assembly and stitching to construct a double-layer PDMS-MCTT fabric-based pressure sensor, which has potential applications in motion detection and health management.

[0048] This invention provides a method for preparing PDMS-MCTT composite material, comprising the following steps:

[0049] S1. Electrospinning with a metal mesh template is used to prepare a TPU fabric (TT) base layer with a surface micro-hemispherical structure.

[0050] S2. Prepare an MXene@CNTs mixed solution by mixing MXene, water-based CNTs slurry and water in a certain proportion;

[0051] S3. Place the TPU fabric base layer in the MXene@CNTs mixed solution, and perform ultrasonic-assisted dip coating and drying. Repeat the dip coating and drying several times to obtain the MCTT fabric.

[0052] S4. The MCTT fabric is placed in a PDMS / n-hexane solution of a certain concentration for encapsulation, and after standing for a period of time, it is taken out and dried to obtain the PDMS-MCTT composite material.

[0053] In some specific implementations, in step S2, the mass ratio of MXene to aqueous CNTs slurry is 1:1 to 3.

[0054] In some specific implementations, in step S3, the ultrasonic-assisted dip coating time is 5 to 30 minutes, and the dip coating and drying steps are repeated 1 to 5 times.

[0055] In some specific implementations, in step S4, the concentration of the PDMS / n-hexane solution is 8–15 wt%, and the settling time is 5–30 min.

[0056] In step S1, the method for preparing the TT substrate includes the following steps:

[0057] S11. Fix a metal wire mesh template of a certain mesh size onto an insulating rubber board and ground it through conductive grounding to form a metal wire mesh receiver;

[0058] S12. Prepare an electrospinning precursor solution of a certain concentration by mixing TPU particles and N,N-dimethylformamide (DMF) solution in a certain proportion.

[0059] S13. Select a needle of a certain size, and perform electrospinning using an electrospinning precursor solution according to certain spinning parameters. After spinning, remove the TT substrate layer and dry it in an oven to obtain the TT substrate layer.

[0060] In some specific implementations, in step S11, the metal mesh template is 20-80 mesh; in step S12, the concentration of the prepared precursor solution is 16-18 wt%; in step S13, the electrospinning needle size is 22, the spinning voltage is 12-16 kV, the feed speed is 0.7 mL / h, and the spinning time is 0.5-2 h.

[0061] In step S2, the preparation method of MXene includes the following steps:

[0062] S21. Take HCl solution and add LiF and stir to obtain etching solution. Add 1g of Ti3AlC2 to the etching solution and stir in a water bath at 37℃ for 24-36h to obtain the etched multilayer MXene solution.

[0063] S22. Wash the multilayer MXene solution with water by centrifugation multiple times, take the lower layer precipitate, and sonicate it in an ice bath for 1 hour. After sonication, centrifuge the MXene solution at 3500 rpm for 30 minutes and take the upper layer of MXene solution.

[0064] In some specific implementations, in step S21, 20 mL of 9 mol / L HCl solution is taken, 1.5 g of LiF is added, and the mixture is slowly stirred for 5-10 min to obtain an etching solution. 1 g of Ti3AlC2 is added to the etching solution, and the mixture is stirred in a water bath at 37°C for 24-36 h to obtain an etched multilayer MXene solution. In step S22, the multilayer MXene solution is washed with water, and the washed multilayer MXene solution is centrifuged at 8000 rpm for 5 min, repeated 5-7 times. The lower layer precipitate is taken until the pH value of the supernatant is greater than 6. The washed multilayer MXene solution is ultrasonically dispersed in an ice bath for 1 h. The ultrasonically dispersed MXene solution is centrifuged at 3500 rpm for 30 min, and the upper few-layer MXene solution is taken.

[0065] Example 1

[0066] A method for preparing a TT substrate includes the following steps:

[0067] S1. Fix a 60-mesh metal wire mesh template onto an insulating rubber board and ground it to form a metal wire mesh receiver.

[0068] S2. Take 4.16g of TPU particles and add them to 20mL of DMF solution. Stir under constant temperature water bath conditions to prepare an 18wt% electrospinning precursor solution.

[0069] S3. Select a size 22 needle for electrospinning. Set the spinning parameters as follows: collection device distance 15cm from spinning needle, spinning voltage 14kV, feed speed 0.7mL / h, spinning time 1h. After spinning, remove the TT electrospun fabric and place it in an oven to dry for 1h to completely remove residual solvent.

[0070] The TT electrospun fabric obtained in step S3 was observed by scanning electron microscopy (SEM), and the results are as follows: Figure 1 As shown, after using the templated receiver, the surface of the TT fabric is no longer smooth, but instead shows regularly and evenly distributed hemispherical protrusions. Figure 1 d), and the morphology of the TPU electrospun nanofibers did not change. Figure 1 e) demonstrates that the surface structure formation of TT fabric occurs during fiber deposition without altering the fiber's morphology. This is because the metal mesh template, fixed to an insulating rubber plate and grounded electrically, forms a metal mesh receiver. This receiver, acting as a current collector in electrospinning, carries an opposite charge to the electrospinning spinneret. Under the influence of a high-voltage electrostatic field, it preferentially receives the electrospun fibers, causing them to accumulate on the metal mesh and form a unique micro-hemispherical structure. However, because the high-voltage electrostatic field and the concentration of the TPU spinning solution remain stable during electrospinning, the resulting spun fibers themselves do not exhibit any differences. Figure 1 f is a cross-sectional SEM image of the TT fabric, showing that the height of the hemispherical protrusions is around 80-100 μm.

[0071] A method for fabricating a double-layer PDMS-MCTT fabric-based pressure sensor includes the following steps:

[0072] S11. Take 20 mL of 9 mol / L HCl solution, add 1.5 g LiF and stir slowly for 5 min to obtain an etching solution. Add 1 g Ti3AlC2 to the etching solution and stir in a water bath at 37℃ for 36 h to obtain an etched multilayer MXene solution. Wash the multilayer MXene solution with water. Centrifuge the washed multilayer MXene solution at 8000 rpm for 5 min and take the lower layer precipitate. Repeat the above washing and centrifugation steps until the pH value of the supernatant is greater than 6. Sonicate the washed multilayer MXene solution in an ice bath for 1 h to remove the few-layer MXene. Centrifuge the MXene solution after sonication at 3500 rpm for 30 min and take the upper few-layer MXene solution.

[0073] S12. Take a small layer of MXene solution and add it to the aqueous CNTs slurry to prepare an MXene@CNTs mixed solution with a mass ratio of MXene to CNTs of 1:1;

[0074] S13. Take 20 mL of MXene@CNTs mixed solution, cut the TT electrospun fabric obtained in step S3 into a size of 4×4 cm and put it into the MXene@CNTs mixed solution. Dip it in the solution for 10 min under ultrasonic assistance, take it out and dry it. Repeat the dip-coating and drying steps 3 times to obtain MCTT fabric.

[0075] S14. Dilute PDMS with n-hexane to prepare a 10wt% PDMS / n-hexane solution. Immerse the MCTT fabric in the PDMS / n-hexane solution, let it stand for 10 minutes, take it out and dry it in an oven to completely evaporate the n-hexane, and obtain the PDMS-MCTT fabric.

[0076] S15. Place two PDMS-MCTT fabrics facing each other, so that the micro-hemispherical structures on the two PDMS-MCTT fabrics come into contact with each other and are sewn together. Finally, use two 1×6cm copper foils as electrodes and use conductive silver paste to bond them to the outside of the two PDMS-MCTT fabrics. Then put them into an oven to cure the silver paste to obtain a double-layer PDMS-MCTT fabric-based pressure sensor.

[0077] Scanning electron microscopy (SEM) was performed on the MCTT and PDMS-MCTT fabrics prepared in steps S13 and S14. The results are as follows: Figure 1 As shown. After the construction of the MXene@CNTs composite conductive layer, the hemispherical protrusion structure on the surface of the MCTT fabric remains clear. Figure 1 g), and the fiber diameter is slightly increased due to the conductive material loaded on the fiber surface. Figure 1 h), but the conductive material is closely distributed with the TPU fibers and does not accumulate, and the porous structure of the TT fabric substrate is still maintained. Figure 1 i is a cross-sectional SEM image of the MCTT fabric. It can be seen that after loading the MXene@CNTs composite conductive layer, the height and clarity of the hemispherical protrusion structure did not change. Figure 1 jk is a surface SEM image of PDMS-MCTT fabric. After PDMS encapsulation, the raised structure on the fabric surface is still clearly visible, and due to the tension of the PDMS layer during the drying process, the fabric surface exhibits a wrinkled appearance. Figure 1 j). Meanwhile, the diameter of the fiber encapsulated by PDMS is further increased ( Figure 1 (k), but the porous structure of the fabric is still preserved. Figure 1 Image l is a cross-sectional SEM image of the PDMS-MCTT fabric. The hemispherical structure on the fabric surface was still preserved after PDMS encapsulation.

[0078] Figure 3 The surface SEM image and corresponding EDS energy dispersive spectroscopy image of the PDMS-MCTT fabric are shown. The C element comes from the TPU substrate and CNTs, the O element comes from the TPU substrate and PDMS encapsulation layer, the Ti and F elements belong to MXene, and the F element comes from the (-F) functional group grafted to the MXene surface during the etching process. The uniform distribution of Ti and F elements proves that MXene is uniformly coated on the entire TPU substrate. The Si element comes from PDMS, and the uniform distribution of Si element on the entire fabric surface proves the uniform loading in PDMS.

[0079] Figure 4 This is a digital photograph of water droplets on PDMS-MCTT fabric. After encapsulating MCTT with hydrophobic PDMS, the surface of the PDMS-MCTT fabric is completely covered by PDMS. Furthermore, with the synergistic effect of the surface micro-hemispherical structure, the water contact angle can reach 132.7°, indicating that the PDMS-MCTT fabric has excellent hydrophobicity.

[0080] Example 2

[0081] This embodiment is basically the same as embodiment 1, except that: step S2 is as follows: 3.7g of TPU particles are added to 20mL of DMF solution and stirred under constant temperature water bath conditions to prepare a 16wt% electrospinning precursor solution.

[0082] Comparative Example 1

[0083] This comparative example is basically the same as Example 1, except that: Step S2 is as follows: 3.26g of TPU particles are added to 20mL of DMF solution and stirred under constant temperature water bath conditions to prepare a 14wt% electrospinning precursor solution.

[0084] It should be noted that the TT electrospun fabric in this comparative example does not have uniformly distributed hemispherical protrusions on its surface and does not possess a micro-hemispherical structure.

[0085] Comparative Example 2

[0086] This comparative example is basically the same as Example 1, except that: Step S2 is as follows: 4.62g of TPU particles are added to 20mL of DMF solution and stirred under constant temperature water bath conditions to prepare a 20wt% electrospinning precursor solution.

[0087] It should be noted that the TT electrospun fabric in this comparative example does not have uniformly distributed hemispherical protrusions on its surface and does not possess a micro-hemispherical structure.

[0088] Comparative Example 3

[0089] This comparative example is basically the same as Example 1, except that step S1 is omitted; step S2 is as follows: 3.26g of TPU particles are added to 20mL of DMF solution and stirred under constant temperature water bath conditions to prepare a 14wt% electrospinning precursor solution.

[0090] It should be noted that the dual-layer PDMS-MCTT fabric-based pressure sensor in this comparative example does not have a micro-hemispherical structure, in addition to not using a metal wire mesh template for guiding the spinning.

[0091] Performance tests were conducted on Examples 1-2 and Comparative Examples 1-3, and the results are shown in Table 1.

[0092] Table 1:

[0093] Performance testing Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Pressure response (kPa) 521.6 515.2 359.6 322.1 208.2 <![CDATA[Sensitivity (KPa -1 )]]> 471.3 463.5 8.083 3.516 0.391

[0094] As shown in Table 1, a comparison of Example 1 with Comparative Examples 1 and 2 reveals that changes in the electrospinning precursor solution affect the interaction between the fibers and the metal mesh template, thus influencing the fiber adhesion and accumulation behavior on the template, and consequently impacting the sensor's sensitivity and pressure response range. When the concentration of the electrospinning precursor solution is too low, the spun fibers become too fine or fail to form continuous fibers, affecting the fiber accumulation on the metal mesh template and the ability to form hemispherical protrusions. When the concentration of the electrospinning precursor solution is too high, the viscosity increases, slowing down the fiber formation rate and increasing the fiber diameter. This also affects the fiber deposition efficiency and distribution uniformity on the metal mesh. Uneven fiber deposition or changes in the interaction between fibers prevent the formation of regularly and uniformly distributed hemispherical protrusions.

[0095] A comparison of Example 1 (a double-layer PDMS-MCTPU / MCTPU fabric-based pressure sensor with a micro-hemispherical structure) and Comparative Example 3 (a double-layer PDMS-MCTPU / MCTPU fabric-based sensor without a micro-hemispherical structure and without a metal mesh template for guided spinning in the fabrication process) reveals that... Figure 5 The sensing ranges of the two sensors can be roughly divided into three linear sensing regions. Example 1 exhibits a significantly superior sensing range compared to Comparative Example 3, achieving a maximum response of 521.6 kPa. In terms of sensitivity, especially in the low pressure range (corresponding to the S1 data of both), Example 1 achieves S = 471.3 kPa. -1 In contrast, Comparative Example 3 only had S = 0.391 kPa. -1 It can be seen that the micro-hemispherical structure has a significant effect on improving the sensitivity and pressure response range of the sensor.

[0096] To test the response of the dual-layer PDMS-MCTT fabric-based pressure sensor of Example 1 to different pressures, Figure 6 The "time-ΔI / I0" curves are shown under different pressure ranges. The dual-layer PDMS-MCTT fabric-based pressure sensor generates repetitive and stable current signals across different pressure ranges. Furthermore, the current value changes less with increasing pressure, indicating that the dual-layer PDMS-MCTT fabric-based pressure sensor is highly sensitive to changes in external pressure and can effectively detect pressure magnitude throughout its sensing range.

[0097] Example 3

[0098] This embodiment is basically the same as embodiment 1, except that: step S1 is: fixing a 40-mesh metal wire mesh template onto an insulating rubber board and grounding it to form a metal wire mesh receiver.

[0099] Example 4

[0100] This embodiment is basically the same as embodiment 1, except that: step S1 is: fixing the 20-mesh metal wire mesh template onto the insulating rubber board and grounding it through conductivity to form a metal wire mesh receiver.

[0101] Example 5

[0102] This embodiment is basically the same as embodiment 1, except that: step S1 is: fixing an 80-mesh metal wire mesh template onto an insulating rubber board and grounding it to form a metal wire mesh receiver.

[0103] Performance tests were conducted on Examples 3-5, and the results are shown in Table 2.

[0104] Table 2:

[0105]

[0106]

[0107] As shown in Table 2, a comparison between Examples 1 and Examples 3-5 reveals that different mesh counts in the wire mesh template result in variations in the size and distribution of holes on the template. Templates with smaller mesh counts have larger holes, allowing more fibers to pass through and accumulate on them; while templates with larger mesh counts have smaller holes, providing more precise control over fiber accumulation and distribution. This difference directly affects the size, distribution, and density of the microhemispherical structure on the TT substrate surface. Specifically, if the mesh count is too small, the resulting microhemispherical structure will be too large or too sparse, leading to insufficient sensor sensitivity and potentially limited pressure response range. Conversely, if the mesh count is too large, while a finer structure can be formed, the fibers may become too densely packed, reducing sensor sensitivity or slowing response speed. Therefore, a suitable wire mesh template mesh count can form a moderately sized and uniformly distributed microhemispherical structure, thereby optimizing the sensor's sensitivity and pressure response range.

[0108] In this invention, TPU particles are combined with DMF solution to prepare an 18wt% electrospinning precursor solution, which can form continuous fibers. This enhances the fiber's ability to accumulate on a metal mesh template and form hemispherical protrusions, increasing the deposition efficiency and uniformity of fiber distribution on the metal mesh. By using a 60-mesh metal mesh template as the current collector, a moderately sized and uniformly distributed micro-hemispherical structure can be formed. Consequently, the prepared double-layer PDMS-MCTT fabric-based pressure sensor exhibits excellent sensitivity (S) in the field of fabric-based flexible pressure sensing. max =471.3 kPa -1 It features a wide pressure sensing range (0-521.6 kPa), a low detection limit (0.003 kPa), fast response times (7 ms and 8 ms), and stable cyclic pressure performance (3000 cycles). In addition to achieving excellent sensing performance, the double-layer PDMS-MCTT fabric also provides air permeability (24.1% deionized water loss rate in 10 days) and hydrophobicity (contact angle of 132.7°).

[0109] The above description is based on the preferred embodiments of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of the invention is defined by the appended claims rather than the foregoing description, and all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0110] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and 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 method for preparing a PDMS-MCTT composite material, characterized in that, Includes the following steps: S1. Electrospinning with a metal mesh template is used to prepare a TPU fabric base layer with a surface micro-hemispherical structure. S2. Prepare an MXene@CNTs mixed solution by mixing MXene, water-based CNTs slurry and water in a certain proportion; S3. Place the TPU fabric base layer in the MXene@CNTs mixed solution, and perform ultrasonic-assisted dip coating and drying. Repeat the dip coating and drying several times to obtain the MCTT fabric. S4. The MCTT fabric is placed in a PDMS / n-hexane solution of a certain concentration for encapsulation, and after standing for a period of time, it is taken out and dried to obtain the PDMS-MCTT composite material. In step S1, the method for preparing the TPU fabric base layer includes the following steps: S11. Fix a 20-80 mesh metal wire template onto an insulating rubber board and ground it to form a metal wire receiver. S12. Prepare an electrospinning precursor solution with a concentration of 16-18 wt% by mixing TPU particles and N,N-dimethylformamide solution in a certain proportion. S13. Select a needle of a certain size, and perform electrospinning using an electrospinning precursor solution according to certain spinning parameters. After spinning, remove the TPU fabric base layer and put it into an oven to dry to obtain the TPU fabric base layer. The height of the micro-hemispherical structure is 80–100 μm.

2. The method for preparing a PDMS-MCTT composite material according to claim 1, characterized in that: In step S13, the spinning parameters are: spinning voltage 12-16kV, feed speed 0.7mL / h, and spinning time 0.5-2h.

3. The method for preparing a PDMS-MCTT composite material according to claim 1, characterized in that: In step S2, the method for preparing MXene includes the following steps: S21. Take HCl solution and add LiF and stir to obtain etching solution. Add 1g of Ti3AlC2 to the etching solution and stir in a water bath at 37℃ for 24-36h to obtain the etched multilayer MXene solution. S22. Wash the multilayer MXene solution with water by centrifugation multiple times, take the lower layer precipitate, and sonicate it in an ice bath for 1 hour. After sonication, centrifuge the MXene solution at 3500 rpm for 30 minutes and take the upper layer of MXene solution.

4. The method for preparing a PDMS-MCTT composite material according to claim 3, characterized in that: In step S21, the stirring time is 5 to 10 minutes; in step S22, the centrifugal washing conditions are: centrifugation at 8000 rpm for 5 minutes, repeated 5 to 7 times.

5. The method for preparing a PDMS-MCTT composite material according to claim 1, characterized in that: In step S2, the mass ratio of MXene to the aqueous CNTs slurry is 1:1 to 3.

6. The method for preparing a PDMS-MCTT composite material according to claim 1, characterized in that: In step S3, the ultrasonic-assisted dip coating time is 5 to 30 minutes, and the dip coating and drying steps are repeated 1 to 5 times.

7. The method for preparing a PDMS-MCTT composite material according to claim 1, characterized in that: In step S4, the concentration of the PDMS / n-hexane solution is 8–15 wt%, and the standing time is 5–30 min.

8. An application of a PDMS-MCTT composite material, characterized in that: The PDMS-MCTT composite material is obtained by the preparation method according to any one of claims 1-7. The PDMS-MCTT composite material is assembled and sewn in a specific manner, and conductive silver paste and copper foil are used to construct electrodes on both sides to prepare a double-layer PDMS-MCTT fabric-based pressure sensor.

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