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

Abstract

The invention discloses a preparation method and application of a dry self-adhesion flexible capacitive pressure sensor, and the method comprises the steps: dissolving a polymer through an organic solvent, and obtaining an electrostatic spinning precursor solution; performing same-pressure conjugate electrostatic spinning through the electrostatic spinning precursor solution to obtain a self-adhesion composite nanofiber membrane; a nanofiber membrane is obtained through electrostatic spinning; the obtained self-adhesion composite nanofiber membrane is used as a packaging layer, and the nanofiber membrane is used for preparing a flexible electrode in a mode of vacuum filtration of a carbon nanotube; and assembling the obtained packaging layer and the flexible electrode according to a capacitive structure, leading out a wire, positioning the assembled structure by using a hollow mask plate, and completing packaging through a hollow hot pressing technology. Through specific polymer selection and an electrostatic spinning technology, the prepared self-adhesion composite nanofiber membrane can be directly adhered to the skin or other complex surfaces, an additional adhesive is not needed, and the comfort level and the use convenience of a user are improved.

Description

Technical Field

[0001] The present invention belongs to the field of sensor technology and material science, and in particular, relates to a preparation method and application of a dry self-adhesive flexible capacitive pressure sensor. Background Art

[0002] With the rapid development of wearable devices and smart sensing technology, the demand for high-performance and comfortable flexible sensors is increasing. However, most flexible sensors rely on external glue or tape to wear, which not only increases the user's discomfort, but also may cause skin allergic reactions. At present, different interface adhesion mechanisms such as van der Waals force, suction adhesion, intermolecular bonding, etc. are used for interface adhesion, which have strong, durable and conformal interface adhesion characteristics on rough, irregular and deformable surfaces. The above strategies still have certain limitations, including chemical synthesis modification and complex preparation process of microstructure interface, poor performance of modulus correction under humid and repeated use conditions, and poor mechanical strength of thinning. In addition, for wearable devices that pursue long-term wear, good breathability is the key to ensure skin health and avoid irritation and adverse reactions. Breathable design helps sweat evaporate and keep the skin dry and comfortable. However, many current wearable sensors use dense film substrates, which have poor breathability, greatly affecting the wearing comfort. In addition, their cumbersome production process further restricts the widespread application and popularization of the technology. Summary of the invention

[0003] The object of the present invention is to provide a preparation method and application of a dry self-adhesive flexible capacitive pressure sensor to solve the above problems.

[0004] To achieve the above object, the present invention adopts the following technical solutions: A method for preparing a dry self-adhesive flexible capacitive pressure sensor, comprising: dissolving the polymer with an organic solvent to obtain an electrospinning precursor solution; The self-adhesive composite nanofiber membrane is obtained by isobaric conjugate electrospinning of an electrospinning precursor solution; the nanofiber membrane is obtained by electrospinning; Using the obtained self-adhesive composite nanofiber membrane as an encapsulation layer, the nanofiber membrane is used to prepare a flexible electrode by vacuum filtration of carbon nanotubes; The obtained packaging layer and flexible electrode are assembled according to the capacitive structure, and the wires are led out. The assembled structure is positioned using a hollow mask, and the packaging is completed using hollow hot pressing technology.

[0005] Furthermore, the step of dissolving the polymer with an organic solvent to obtain an electrospinning precursor solution includes: dissolving at least two polymers with an organic solvent, wherein the polymers are selected from thermoplastic polyurethane with biocompatibility and water-soluble adhesive polyvinyl alcohol.

[0006] Furthermore, the self-adhesive composite nanofiber membrane is obtained by performing isobaric conjugate electrospinning using an electrospinning precursor solution, comprising: Co-pressure conjugate electrospinning is a double-needle co-spinning technology, in which one needle is responsible for spinning the basic skeleton polymer solution, and the other needle is responsible for spinning the water-soluble adhesive solution.

[0007] Furthermore, the voltage was regulated to 14-20 kV, the spinning propulsion speed of the water-soluble adhesive solution was 0.2-0.6 mL / h, the spinning propulsion speed of the basic skeleton polymer solution was 0.15-0.9 mL / h, and the receiving distance was 13-17 cm, thereby forming a composite nanofiber membrane with adhesion.

[0008] Furthermore, the obtained composite nanofiber membrane is dried, and the drying temperature is controlled in the range of 50° C. to 70° C. to complete the preparation of the self-adhesive composite nanofiber membrane.

[0009] Furthermore, the hollow pattern of the hollow mask is a scaled flexible electrode with a scaling ratio of 0.9; the material of the mask is silicone rubber elastomer polydimethylsiloxane.

[0010] Furthermore, the specific process of the hollow hot pressing technology is to place the assembled hierarchically separated sensor in a hollow mask plate under set conditions through a flat vulcanizing machine, and by controlling the heating temperature and pressurizing time, the nanofibers of each layer except the hollow area are evenly and tightly fused and shaped to form a dry self-adhesive flexible capacitive pressure sensor.

[0011] Furthermore, the setting conditions are: temperature 55-75°C, pressure 2-3 MPa.

[0012] A sensor is made by the method for preparing a dry self-adhesive flexible capacitive pressure sensor.

[0013] An application of sensors for medical health monitoring, sports performance analysis and human-computer interaction.

[0014] Compared with the prior art, the present invention has the following technical effects: The present invention uses specific polymer selection and electrospinning technology to produce a self-adhesive composite nanofiber membrane that can be directly adhered to the skin or other complex surfaces without the need for additional adhesives. This significantly improves user comfort and convenience, especially in application scenarios where sensors need to be worn for a long time or replaced frequently.

[0015] The optimized design of the full fiber ensures that the sensor has good breathability. This helps sweat evaporate and reduces discomfort that may occur when worn for a long time, such as stuffiness and humidity. This feature is particularly important for applications that require long-term monitoring of physiological parameters, such as sports health monitoring and medical monitoring.

[0016] Compared with the traditional method, the present invention simplifies the sensor preparation process through 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.

[0017] The assembled structure is positioned using a hollow mask and encapsulated using hollow hot pressing technology, ensuring the accuracy and stability of the capacitive structure. This helps improve the measurement accuracy and reliability of the sensor and meet the needs of various application scenarios.

[0018] The polymer is selected from biocompatible thermoplastic polyurethane and water-soluble adhesive polyvinyl alcohol, ensuring the safety and comfort of the sensor when it contacts the skin. This is crucial for medical monitoring, human health monitoring and other applications that require direct contact with the skin.

[0019] The hollow pattern of the hollow mask is a scaled flexible electrode, which allows the sensor to be scaled and adjusted according to actual needs. At the same time, the design of the flexible electrode and the self-adhesive composite nanofiber membrane makes the sensor flexible and adaptable, and can fit various complex surfaces.

[0020] In summary, the dry self-adhesive flexible capacitive pressure sensor of the present invention has shown remarkable technical effects in terms of self-adhesive properties, air permeability, preparation process and cost, capacitive structure design and positioning accuracy, material selection and biocompatibility, scalability and flexibility, etc. These advantages make the sensor have broad application prospects in the fields of medical monitoring, human health monitoring, sports health monitoring, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings: Figure 1 is a schematic diagram of the preparation of the composite nanofiber membrane; Figure 2 It is a schematic diagram of the sensor packaged by hollow hot pressing technology; Figure 3 Schematic diagram of the measurement of sensor adhesion force with different ratios of encapsulation layers.

[0022] Figure 4is the sensor adhesion force with different ratios of encapsulation layers.

[0023] Figure 5 (a) is the pressure capacitance response curve of the sensor, and (b) is 1000 bending cycles of the sensor. DETAILED DESCRIPTION

[0024] In order to make the purpose and technical solution of the present invention clearer and easier to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0026] Embodiment 1, the present invention provides a method for preparing a dry self-adhesive flexible capacitive pressure sensor, comprising: dissolving the polymer with an organic solvent to obtain an electrospinning precursor solution; The self-adhesive composite nanofiber membrane is obtained by isobaric conjugate electrospinning of an electrospinning precursor solution; the nanofiber membrane is obtained by electrospinning; Using the obtained self-adhesive composite nanofiber membrane as an encapsulation layer, the nanofiber membrane is used to prepare a flexible electrode by vacuum filtration of carbon nanotubes; The obtained packaging layer and flexible electrode are assembled according to the capacitive structure, and the wires are led out. The assembled structure is positioned using a hollow mask, and the packaging is completed using hollow hot pressing technology.

[0027] Embodiment 2, the present invention provides a method for preparing a dry self-adhesive flexible capacitive pressure sensor, specifically comprising: The method for preparing a self-adhesive composite nanofiber membrane comprises the following steps: Step 1, dissolving the polymer with an organic solvent to obtain an electrospinning precursor solution; Step 2, subjecting the electrospinning precursor solution obtained in step 1 to isobaric conjugate electrospinning; Step 3: by adjusting the voltage and propulsion speed of the isobaric conjugate electrospinning in step 2, the formed nanofibers are caused to undergo a certain degree of crosslinking and entanglement during the spinning process, thereby forming a composite nanofiber membrane with a certain adhesion; Step 4: Drying the composite nanofiber membrane obtained in step 3 to enhance the interconnection between fibers, thereby completing the preparation of the self-adhesive composite nanofiber membrane.

[0028] In step 1, there are two types of electrospinning precursor solutions.

[0029] In step 1, the polymer uses biocompatible thermoplastic polyurethane and water-soluble adhesive polyvinyl alcohol.

[0030] In step 1, the organic solvent is selected to have a proper mixing ratio of high boiling point and low boiling point.

[0031] In step 2, the same-pressure conjugate electrospinning is a double-needle co-spinning technology, in which one needle is responsible for the spinning of the basic skeleton polymer solution, and the other needle is responsible for the spinning of the water-soluble adhesive solution, so as to achieve uniform doping and functional integration of the composite nanofiber membrane during the spinning process.

[0032] In step 3, the voltage of the isobaric conjugate electrospinning is 14-20 kV, the propulsion speed is 0.2-0.6 mL / h, and the receiving distance is 13-17 cm.

[0033] In step 4, the drying temperature of the composite nanofiber membrane is 50°C-70°C.

[0034] A method for preparing a dry self-adhesive flexible capacitive pressure sensor comprises the following steps: Step 1, obtaining a nanofiber membrane and a self-adhesive and functional layer composite nanofiber membrane by electrospinning and isobaric conjugate electrospinning; Step 2: preparing a flexible electrode by vacuum filtering carbon nanotubes based on the nanofiber membrane obtained in step 1; Step 3, preparing a mask having a hollow pattern, wherein the hollow pattern is a scaled flexible electrode, and the scale ratio is 0.9; Step 4, assembling the functionalized composite nanofiber membrane, the flexible electrode and the functional layer obtained in steps 1 and 2 to form a capacitive structure, and leading out a wire; Step 5: Place the hollow mask on the assembled sensor structure and package the capacitive sensor using hollow hot pressing technology.

[0035] In step 3, the material of the mask is silicone rubber elastomer polydimethylsiloxane (PDMS).

[0036] In step 5, the specific process of the hollow hot pressing technology is to place the assembled hierarchically separated sensor in a hollow mask plate under certain temperature (55-75°C) and pressure (2-3 MPa) conditions through a flat vulcanizer, and by controlling the heating temperature and pressurizing time, the nanofibers of each layer except the hollow area are evenly and tightly fused and shaped to form a dry self-adhesive flexible capacitive pressure sensor.

[0037] In the above technical scheme, the present invention provides a method for preparing a dry self-adhesive flexible capacitive pressure sensor, wherein the sensor includes a packaging layer, a functional layer, and an electrode layer. The packaging layer adopts a self-adhesive composite nanofiber membrane, the functional layer is a composite nanofiber membrane, and the electrode layer is a nanofiber membrane filtered carbon nanotube.

[0038] Example 3, 1) Preparation of self-adhesive composite nanofiber membranes with different proportions of components. The precursor solution concentration was kept constant by isobaric conjugate electrospinning. Under the conditions of TPU of 2.80 g / 10 mL, PVA of 10 wt%, spinning voltage of 14 kV, distance between the needle and the receiving device of 15 cm, rotation speed of 300 rpm, and needle of 22 G (TPU) / 23 G (PVA) (with an inner diameter of 0.41 mm / 0.34 mm), the propulsion speed of the syringe was adjusted; wherein the propulsion speed of PVA was kept constant at 0.30 mL / h, and the propulsion speed of the TPU precursor solution was changed to 0.15 mL / h, 0.30 mL / h, 0.60 mL / h, and 0.90 mL / h, respectively, in order to adjust the proportion of different fibers. The spinning lasted for 8 h, 4 h, 2 h, and 1.3 h, respectively, until self-adhesive composite nanofiber membranes with different proportions and a thickness of 10 μm were deposited on the release paper.

[0039] 2) Construction of functional layer composite nanofiber membrane. Based on the process of 1), TPU and polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) precursor solutions were subjected to co-pressure conjugate electrospinning. The propulsion speed of the precursor solution was set to 1mL / 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, and a PVDF-TrFE / TPU NFs membrane of about 15 μm thick was collected for 2 hours.

[0040] 3) Preparation of flexible electrodes. Take out 5 mL of commercial finished carbon nanotubes with a 10 wt% aqueous dispersion and dilute it to 10-20 times with deionized water; stir at room temperature for 1 h and then ultrasonicate for 1 h to evenly disperse the carbon nanotubes in the system; lay the hand-cut TUP NFs membrane (5×5 cm2) flat on the filtration device; filter the dispersion twice onto the front and back sides of the TPU nanofiber membrane; dry at 60°C for 10 min during the filtration process to help the conductive active material reload the nanofiber membrane surface; dry the filtered electrode at 60°C for 1 h, and after it is completely dried, carve it into a uniform and standardized shape through a mold.

[0041] 4) The flexible electrodes obtained by the above process are placed on the upper and lower sides of the functional layer of the composite nanofibers and the wires are led out for electrical connection. At the same time, the self-adhesive composite nanofiber membrane is placed on both sides of the flexible electrode as a packaging layer, so that a five-layer sensor structure is constructed. At the same time, the PDMS membrane (thickness of about 100 μm) with a 90% reduction in electrode pattern engraving and hollowing is laid on top of the five-layer structure and aligned to the center, and the corresponding mask is used as a hot press for 10 minutes at a temperature of 65 ° C and a pressure of 2 MPa. Based on the above assembly process, a lightweight, breathable and self-adhesive flexible capacitive pressure sensor is prepared.

[0042] Test Example 1: The adhesion of the functional composite nanofiber membrane was measured using a tensile testing machine based on the peeling model. Figure 3 As shown in the figure, a 2×3 cm2 square sample was used, and it was fully moistened with 75% alcohol and attached to a PDMS circular base (simulating human skin) and waited for complete drying; then, a 3 M transparent tape was used to firmly stick the middle part of the square sample and pull it upward at a constant speed of 15 mm / s. During the tensile test, the angle between the tape and the functional composite nanofiber membrane was always maintained at 90° until the membrane was completely separated from the PDMS base.

[0043] The test results are as follows Figure 4 As shown in Figure 2, composite nanofiber membranes with different proportions in the same size (2×3 cm2) exhibit different peeling forces. Figure 4 As shown in the figure, the sensor encapsulated with 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 TPU:PVA=1:1 composite fiber membrane can withstand a maximum tensile force of 0.62 N. As the PVA ratio increases, the maximum adhesion of the composite nanofiber membrane on the skin also increases.

[0044] Test Example 2: The pressure-capacitance response test of the self-adhesive flexible capacitive pressure sensor prepared above was carried out, such as Figure 5 (a) shows that the device with an ordered arrangement structure exhibits higher sensitivity performance in the vertical pressure range of 0-40 kPa. When the vertical pressure is lower than 3 kPa, the sensitivity of the prepared sensor is 112.6 / MPa. When the dynamic pressure is maintained in the range of 3 to 40 kPa, although the sensitivity decreases, it still maintains at the level of 6.4 / MPa. In order to further study the stability and durability of flexible pressure sensors, such as Figure 5 As shown in (b), the sensor was subjected to 1000 repeated bending cycles under the condition of a chord length of 25 mm. The experimental results show that the response of the sensor remains almost consistent during each bending process, showing extremely high stability.

[0045] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

Claims

1. A method for preparing a dry self-adhesive flexible capacitive pressure sensor, characterized in that: include: dissolving the polymer with an organic solvent to obtain an electrospinning precursor solution; The self-adhesive composite nanofiber membrane is obtained by isobaric conjugate electrospinning using an electrospinning precursor solution; Nanofibrous membranes were obtained by electrospinning; Using the obtained self-adhesive composite nanofiber membrane as an encapsulation layer, the nanofiber membrane is used to prepare a flexible electrode by vacuum filtration of carbon nanotubes; The obtained packaging layer and flexible electrode are assembled according to the capacitive structure, and the wires are led out. The assembled structure is positioned using a hollow mask, and the packaging is completed using hollow hot pressing technology.

2. The method for preparing a dry self-adhesive flexible capacitive pressure sensor according to claim 1, characterized in that: The method of dissolving the polymer with an organic solvent to obtain an electrospinning precursor solution comprises: dissolving at least two polymers with an organic solvent, wherein the polymers are selected from thermoplastic polyurethane with biocompatibility and water-soluble adhesive polyvinyl alcohol.

3. The method for preparing a dry self-adhesive flexible capacitive pressure sensor according to claim 1, characterized in that: The method of performing isobaric conjugate electrospinning with an electrospinning precursor solution to obtain a self-adhesive composite nanofiber membrane comprises: Co-pressure conjugate electrospinning is a double-needle co-spinning technology, in which one needle is responsible for spinning the basic skeleton polymer solution, and the other needle is responsible for spinning the water-soluble adhesive solution.

4. The method for preparing a dry self-adhesive flexible capacitive pressure sensor according to claim 3, characterized in that: The voltage was regulated to be 14-20 kV, the spinning propulsion speed of the water-soluble adhesive solution was 0.2-0.6 mL / h, the spinning propulsion speed of the basic skeleton polymer solution was 0.15-0.9 mL / h, and the receiving distance was 13-17 cm, thereby forming a composite nanofiber membrane with adhesion.

5. The method for preparing a dry self-adhesive flexible capacitive pressure sensor according to claim 3, characterized in that: The obtained composite nanofiber membrane is dried, and the drying temperature is controlled within the range of 50° C. to 70° C. to complete the preparation of the self-adhesive composite nanofiber membrane.

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

7. The method for preparing a dry self-adhesive flexible capacitive pressure sensor according to claim 1, characterized in that: The specific process of hollow hot pressing technology is to place the assembled hierarchically separated sensor in a hollow mask through a flat vulcanizer under set conditions. By controlling the heating temperature and pressurizing time, the nanofibers of each layer except the hollow area are evenly and tightly fused and shaped to form a dry self-adhesive flexible capacitive pressure sensor.

8. The method for preparing a dry self-adhesive flexible capacitive pressure sensor according to claim 7, characterized in that: The setting conditions are: temperature 55-75℃, pressure 2-3 MPa.

9. A sensor, characterized in that: The dry self-adhesive flexible capacitive pressure sensor is prepared by the preparation method of any one of claims 1 to 9.

10. The use of a sensor as claimed in claim 9, characterized in that: Used for medical health monitoring, sports performance analysis and human-computer interaction.

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