Preparation method and application of dry self-adhesive flexible capacitive pressure sensor

Abstract

A preparation method and application of a dry self-adhesive flexible capacitive pressure sensor, comprising: dissolving a polymer with an organic solvent to obtain an electrospinning precursor solution; performing the same pressure conjugate electrospinning through the electrospinning precursor solution to obtain a self-adhesive composite nanofiber membrane; obtaining a nanofiber membrane through electrospinning; using the obtained self-adhesive composite nanofiber membrane as a packaging layer, and preparing a flexible electrode through a vacuum suction filtration carbon nanotube method; assembling the obtained packaging layer and flexible electrode according to a capacitive structure, leading out a lead wire, positioning the assembled structure using a hollow mask, and completing packaging through a hollow hot pressing technology. Through specific polymer selection and electrospinning technology, the self-adhesive composite nanofiber membrane prepared by the application can be directly adhered to the skin or other complex surfaces without the need for additional adhesives, thereby improving the comfort and use convenience of users.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology and materials science, specifically relating to a method for preparing and applying a dry self-adhesive flexible capacitive pressure sensor. Background Technology

[0002] With the rapid development of wearable devices and smart sensing technologies, the demand for high-performance, comfortable flexible sensors is increasing. However, the wearing of flexible sensors mostly relies on external adhesives or tapes, which not only increases user discomfort but may also trigger skin allergies. Currently, different interfacial adhesion mechanisms, such as van der Waals forces, suction adhesion, and intermolecular bonding, are used for interfacial adhesion, exhibiting robust, durable, and shape-preserving interfacial adhesion characteristics on rough, irregular, and deformable surfaces. These strategies still have certain limitations, including complex chemical synthesis modifications and microstructure interface fabrication processes, poor performance of modulus correction under humid and repeated use conditions, and poor mechanical strength due to thickness reduction. Furthermore, for wearable devices designed for extended wear, good breathability is crucial for ensuring skin health and avoiding irritation and adverse reactions. Breathable design helps sweat evaporate, keeping the skin dry and comfortable. However, many current wearable sensors use dense thin-film substrates with poor breathability, significantly impacting wearing comfort. Coupled with their complex manufacturing processes, this further restricts the widespread application and popularization of the technology. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing and applying a dry self-adhesive flexible capacitive pressure sensor, in order to solve the above-mentioned problems.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for fabricating a dry, self-adhesive, flexible capacitive pressure sensor, comprising:

[0006] The polymer was dissolved in an organic solvent to obtain an electrospinning precursor solution;

[0007] Self-adhesive composite nanofiber membranes were obtained by isobaric conjugate electrospinning using an electrospinning precursor solution; nanofiber membranes were obtained by electrospinning.

[0008] The obtained self-adhesive composite nanofiber membrane was used as an encapsulation layer, and the nanofiber membrane was used to prepare flexible electrodes by vacuum filtration of carbon nanotubes.

[0009] The obtained encapsulation layer and flexible electrode are assembled according to a capacitive structure, and wires are led out. A hollow mask is used to position the assembled structure, and encapsulation is completed by hollow hot pressing technology.

[0010] Furthermore, the step of dissolving the polymer in an organic solvent to obtain the electrospinning precursor solution includes: dissolving at least two polymers in an organic solvent, wherein the polymers are selected from a biocompatible thermoplastic polyurethane and a water-soluble adhesive polyvinyl alcohol.

[0011] Furthermore, the method of obtaining a self-adhesive composite nanofiber membrane by isobaric conjugated electrospinning using an electrospinning precursor solution includes:

[0012] The same-pressure conjugate electrospinning is a dual-needle co-spinning technology, in which one needle is responsible for spinning the basic backbone polymer solution, while the other needle is responsible for spinning the water-soluble adhesive solution.

[0013] Furthermore, the voltage is adjusted to 14-20 kV, the spinning speed of the water-soluble adhesive solution is 0.2-0.6 mL / h, the spinning speed of the basic backbone polymer solution is 0.15-0.9 mL / h, and the receiving distance is 13-17 cm, forming a composite nanofiber membrane with adhesive properties.

[0014] Furthermore, the obtained composite nanofiber membrane is dried at a temperature controlled within the range of 50°C to 70°C to complete the preparation of the self-adhesive composite nanofiber membrane.

[0015] Furthermore, the cutout pattern of the cutout mask is a scaled-up flexible electrode with a scaling ratio of 0.9; the material of the mask is silicone rubber elastomer polydimethylsiloxane.

[0016] Furthermore, the specific process of hollow hot pressing technology is as follows: under set conditions, the assembled layered structure of the sensor is placed in a hollow mask through a flat vulcanizing machine. By controlling the heating temperature and pressurization time, the nanofibers of each layer are uniformly and tightly fused and shaped except for the hollow area, to form a dry self-adhesive flexible capacitive pressure sensor.

[0017] Furthermore, the settings are: temperature 55-75℃, pressure 2-3 MPa.

[0018] A sensor is prepared by the method described above for fabricating a dry self-adhesive flexible capacitive pressure sensor.

[0019] An application of a sensor for medical and health monitoring, motion performance analysis, and human-computer interaction.

[0020] Compared with the prior art, the present invention has the following technical effects:

[0021] This invention utilizes specific polymer selection and electrospinning technology to produce a self-adhesive composite nanofiber membrane that can directly adhere to the skin or other complex surfaces without the need for additional adhesives. This significantly improves user comfort and ease of use, especially in applications requiring prolonged wear or frequent sensor replacements.

[0022] The optimized design of the all-fiber sensor ensures excellent breathability. This helps sweat evaporate, reducing discomfort such as stuffiness and dampness that may occur during prolonged wear. This feature is especially important for applications that require long-term monitoring of physiological parameters, such as sports health monitoring and medical monitoring.

[0023] Compared to traditional methods, this invention simplifies the sensor fabrication process by employing steps such as electrospinning, vacuum filtration of carbon nanotubes to prepare flexible electrodes, and hollow hot pressing technology. This not only improves production efficiency but also reduces production costs, making the sensor more competitive in the market.

[0024] The assembled structure is positioned using a perforated mask, and encapsulation is completed through hollow thermoforming technology, ensuring the accuracy and stability of the capacitive structure. This helps improve the measurement accuracy and reliability of the sensor, meeting the needs of various application scenarios.

[0025] The polymers are selected from biocompatible thermoplastic polyurethane and water-soluble adhesive polyvinyl alcohol, ensuring the safety and comfort of the sensor when in contact with the skin. This is crucial for applications requiring direct skin contact, such as medical monitoring and human health monitoring.

[0026] The perforated pattern on the perforated mask serves as a scalable flexible electrode, allowing the sensor to be scaled and adjusted according to actual needs. Simultaneously, the design of the flexible electrode and the self-adhesive composite nanofiber membrane gives the sensor excellent flexibility and adaptability, enabling it to conform to various complex surfaces.

[0027] In summary, the dry self-adhesive flexible capacitive pressure sensor of this invention exhibits significant technical advantages in terms of self-adhesion characteristics, air permeability, manufacturing process and cost, capacitive structure design and positioning accuracy, material selection and biocompatibility, as well as scalability and flexibility. These advantages make this sensor promising for broad applications in medical monitoring, human health monitoring, and sports health monitoring. Attached Figure Description

[0028] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0029] Figure 1This is a schematic diagram of the preparation of composite nanofiber membranes;

[0030] Figure 2 This is a schematic diagram of a sensor encapsulated using hollow thermoforming technology;

[0031] Figure 3 This is a schematic diagram illustrating the measurement of sensor adhesion force with different proportions of encapsulation layers.

[0032] Figure 4 It refers to the adhesion force of sensors with different proportions of encapsulation layers.

[0033] Figure 5 (a) shows the sensor's pressure-capacitance response curve, and (b) shows the sensor's 1000 bending cycles. Detailed Implementation

[0034] To make the objectives and technical solutions of this invention clearer and easier to understand, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0035] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0036] Example 1: This invention provides a method for fabricating a dry self-adhesive flexible capacitive pressure sensor, comprising:

[0037] The polymer was dissolved in an organic solvent to obtain an electrospinning precursor solution;

[0038] Self-adhesive composite nanofiber membranes were obtained by isobaric conjugate electrospinning using an electrospinning precursor solution; nanofiber membranes were obtained by electrospinning.

[0039] The obtained self-adhesive composite nanofiber membrane was used as an encapsulation layer, and the nanofiber membrane was used to prepare flexible electrodes by vacuum filtration of carbon nanotubes.

[0040] The obtained encapsulation layer and flexible electrode are assembled according to a capacitive structure, and wires are led out. A hollow mask is used to position the assembled structure, and encapsulation is completed by hollow hot pressing technology.

[0041] Example 2: This invention provides a method for fabricating a dry self-adhesive flexible capacitive pressure sensor, specifically including:

[0042] The method for preparing self-adhesive composite nanofiber membranes includes the following steps:

[0043] Step 1: Dissolve the polymer in an organic solvent to obtain an electrospinning precursor solution;

[0044] Step 2: Perform isobaric conjugated electrospinning on the electrospinning precursor solution obtained in Step 1.

[0045] Step 3: By adjusting the voltage and propulsion speed of the same-pressure conjugate electrospinning in step 2, the formed nanofibers are cross-linked and entangled to a certain extent during the spinning process, forming a composite nanofiber membrane with a certain adhesion.

[0046] Step 4: Dry the composite nanofiber membrane obtained in Step 3 to enhance the interconnection between fibers and complete the preparation of the self-adhesive composite nanofiber membrane.

[0047] In step 1, there are two types of electrospinning precursor solutions.

[0048] In step 1, the polymer is a biocompatible thermoplastic polyurethane and a water-soluble adhesive polyvinyl alcohol.

[0049] In step 1, an appropriate mixing ratio of high-boiling-point and low-boiling-point organic solvents is selected.

[0050] In step 2, the co-spinning of the same pressure conjugated electrospinning is a dual-needle co-spinning technology, in which one needle is responsible for spinning the basic backbone polymer solution, while the other needle is responsible for spinning the water-soluble adhesive solution, so as to achieve uniform doping and functional integration of the composite nanofiber membrane during the spinning process.

[0051] In step 3, the voltage of the same-pressure conjugate electrospinning is 14-20kV, the feed speed is 0.2-0.6 mL / h, and the receiving distance is 13-17 cm.

[0052] In step 4, the drying temperature of the composite nanofiber membrane is 50℃-70℃.

[0053] A method for fabricating a dry self-adhesive flexible capacitive pressure sensor includes the following steps:

[0054] Step 1: Obtain nanofiber membranes and self-adhesive and functional layer composite nanofiber membranes by electrospinning and isobaric conjugate electrospinning.

[0055] Step 2: Based on the nanofiber membrane obtained in Step 1, a flexible electrode is prepared by vacuum filtration of carbon nanotubes;

[0056] Step 3: Prepare a mask with a hollowed-out pattern, where the hollowed-out pattern is a scaled-down flexible electrode with a scaling ratio of 0.9;

[0057] Step 4: Assemble the functionalized composite nanofiber membrane, flexible electrode, and functional layer obtained in steps 1 and 2 to form a capacitive structure, and lead out wires;

[0058] Step 5: Place the cutout mask onto the assembled sensor structure and encapsulate the capacitive sensor using hollow thermoforming technology.

[0059] In step 3, the material of the mask is polydimethylsiloxane (PDMS), a silicone rubber elastomer.

[0060] In step 5, the hollow hot pressing technology specifically involves placing the assembled, layered sensor into a hollow mask under certain temperature (55-75℃) and pressure (2-3 MPa) conditions using a flat vulcanizing machine. By controlling the heating temperature and pressurization time, the nanofibers of each layer are uniformly and tightly fused and shaped, except for the hollow area, to form a dry self-adhesive flexible capacitive pressure sensor.

[0061] In the above technical solution, the present invention provides a method for preparing a dry self-adhesive flexible capacitive pressure sensor. The sensor includes an encapsulation layer, a functional layer, and an electrode layer. The encapsulation layer is a self-adhesive composite nanofiber membrane, the functional layer is a composite nanofiber membrane, and the electrode layer is a nanofiber membrane filtration carbon nanotube.

[0062] Example 3, 1) Preparation of self-adhesive composite nanofiber membranes with different component ratios. Using conjugate electrospinning under the same pressure to maintain a constant precursor solution concentration, with TPU at 2.80 g / 10 mL, PVA at 10 wt%, spinning voltage at 14 kV, needle-to-receiver distance at 15 cm, rotation speed at 300 rpm, and needles with 22 G (TPU) / 23 G (PVA) (inner diameter 0.41 mm / 0.34 mm), the syringe feed rate was adjusted. PVA was fed at a constant rate of 0.30 mL / h, while the feed rate of the TPU precursor solution was systematically adjusted to 0.15 mL / h, 0.30 mL / h, 0.60 mL / h, and 0.90 mL / h to regulate the proportions of different fibers. Spinning continued for 8 h, 4 h, 2 h, and 1.3 h until a 10 μm thick self-adhesive composite nanofiber membrane with different ratios was deposited on release paper.

[0063] 2) Construction of functional layer composite nanofiber membrane. Based on the process in 1), TPU and polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) precursor solutions were electrospun under the same pressure and conjugated. The feed rate of the precursor solution was set to 1 mL / h, the positive voltage was set to 14 kV, and the negative voltage was grounded by default. A total voltage of 14 kV was applied between the metal needle and the high-speed roller collector. The humidity was maintained at 25 %RH. After 2 hours, a PVDF-TrFE / TPU NFs membrane with a thickness of about 15 μm was collected.

[0064] 3) Preparation of flexible electrodes. Take 5 mL of a commercially available aqueous dispersion of carbon nanotubes with a content of 10 wt%, and dilute it with deionized water to a ratio of 10-20. Stir at room temperature for 1 h, and then sonicate for 1 h to ensure that the carbon nanotubes are uniformly dispersed in the system. Lay a hand-cut TUP NFs membrane (5×5 cm2) flat on a vacuum filtration device. Filter the dispersion twice to both sides of the TPU nanofiber membrane. During the vacuum filtration process, drying at 60°C for 10 min helps the conductive active material to reload onto the surface of the nanofiber membrane. Dry the electrode obtained by vacuum filtration at 60 ℃ for 1 h. After it is completely dry, carve it into a uniform and standardized shape using a mold.

[0065] 4) The flexible electrodes obtained by the above process are placed on the upper and lower sides of the functional layer of the composite nanofiber and led out with wires for electrical connection. Simultaneously, a self-adhesive composite nanofiber membrane is placed on both sides of the flexible electrodes as an encapsulation layer, thus constructing a five-layer sensor structure. A PDMS film (approximately 100 μm thick) with a 90% scaled-down electrode pattern is then laid on top of the five-layer structure and aligned with the center, serving as a mask. This mask is then hot-pressed for 10 minutes at 65 ℃ and 2 MPa. Based on the above assembly process, a lightweight, breathable, and self-adhesive flexible capacitive pressure sensor is fabricated.

[0066] Test Example 1:

[0067] The adhesive force of functional composite nanofiber membranes was measured using a tensile testing machine based on a peel model. Figure 3 As shown, a 2×3 cm² square sample was used and thoroughly moistened with 75% alcohol before being attached to a circular PDMS base (simulating human skin) and allowed to dry completely. Then, 3M transparent tape was used to firmly adhere the center of the square sample, and it was pulled upwards at a constant speed of 15 mm / s. During the tensile test, the angle between the tape and the functional composite nanofiber membrane was maintained at 90° until the membrane completely separated from the PDMS base.

[0068] Test results are as follows Figure 4As shown, composite nanofiber membranes of the same size (2×3 cm²) but with different proportions exhibit different peeling forces. Figure 4 As shown, the sensor encapsulated with a TPU:PVA=1:2 composite fiber membrane can withstand a maximum tensile force of up to 0.91 N under wet conditions. The sensor encapsulated with a TPU:PVA=1:1 composite fiber membrane can withstand a maximum tensile force of 0.62 N. With increasing PVA ratio, the maximum adhesion of the composite nanofiber membrane to the skin also increases.

[0069] Test Example 2:

[0070] The pressure-capacitive response of the self-adhesive flexible capacitive pressure sensor prepared above was tested, such as... Figure 5 As shown in (a), devices with ordered structures exhibit higher sensitivity performance within the vertical pressure range of 0-40 kPa. When the vertical pressure is below 3 kPa, the sensitivity of the fabricated sensor is 112.6 / MPa. When the dynamic pressure is maintained within the range of 3 to 40 kPa, although the sensitivity decreases, it still remains at a level of 6.4 / MPa. To further investigate the stability and durability of the flexible pressure sensor, such as... Figure 5 As shown in (b), 1000 repeated bending cycles were performed on the chord with a length of 25 mm. The experimental results show that the sensor response remained almost constant during each bending process, demonstrating extremely high stability.

[0071] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A method for fabricating a dry self-adhesive flexible capacitive pressure sensor, characterized in that, include: The polymer was dissolved in an organic solvent to obtain an electrospinning precursor solution; Self-adhesive composite nanofiber membranes were obtained by isobaric conjugate electrospinning using an electrospinning precursor solution. Nanofiber membranes were obtained by electrospinning. The obtained self-adhesive composite nanofiber membrane was used as an encapsulation layer, and the nanofiber membrane was used to prepare flexible electrodes by vacuum filtration of carbon nanotubes. The obtained encapsulation layer and flexible electrode are assembled according to a capacitive structure, and wires are led out. The assembled structure is positioned using a hollow mask, and encapsulation is completed through hollow hot pressing technology. The process of dissolving the polymer in an organic solvent to obtain an electrospinning precursor solution includes: dissolving at least two polymers in an organic solvent, wherein the polymers are selected from biocompatible thermoplastic polyurethane and water-soluble adhesive polyvinyl alcohol; The process of obtaining a self-adhesive composite nanofiber membrane by isobaric conjugated electrospinning using an electrospinning precursor solution includes: The same pressure conjugate electrospinning is a dual-needle co-spinning technology, in which one needle is responsible for spinning the basic backbone polymer solution, and the other needle is responsible for spinning the water-soluble adhesive solution. The voltage is adjusted to 14-20 kV, the spinning speed of the water-soluble adhesive solution is 0.2-0.6 mL / h, the spinning speed of the basic backbone polymer solution is 0.15-0.9 mL / h, and the receiving distance is 13-17 cm, forming a composite nanofiber membrane with adhesive properties.

2. The method for fabricating a dry self-adhesive flexible capacitive pressure sensor according to claim 1, characterized in that, The obtained composite nanofiber membrane was dried at a temperature controlled between 50°C and 70°C to complete the preparation of the self-adhesive composite nanofiber membrane.

3. The method for fabricating a dry self-adhesive flexible capacitive pressure sensor according to claim 1, characterized in that, The cutout pattern of the cutout mask is a scaled-down flexible electrode with a scaling ratio of 0.9; the material of the mask is silicone rubber elastomer polydimethylsiloxane.

4. The method for fabricating a dry self-adhesive flexible capacitive pressure sensor according to claim 1, characterized in that, The specific process of hollow hot pressing technology is as follows: under set conditions, the assembled layered structure of the sensor is placed in a hollow mask through a flat vulcanizing machine. By controlling the heating temperature and pressurization time, the nanofibers of each layer are uniformly and tightly fused and shaped except for the hollow area, to form a dry self-adhesive flexible capacitive pressure sensor.

5. The method for fabricating a dry self-adhesive flexible capacitive pressure sensor according to claim 4, characterized in that, The set conditions are: temperature 55-75℃, pressure 2-3 MPa.

6. A sensor, characterized in that, The dry self-adhesive flexible capacitive pressure sensor is prepared by any one of claims 1 to 5.

7. The application of the sensor as described in claim 6, characterized in that, Used for medical and health monitoring, sports performance analysis, and human-computer interaction.

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