A method for processing KNLTN electrospinning solution, nanofibers, and sensors.

Abstract

This invention relates to the field of piezoelectric pressure sensors, and specifically to a method for processing KNLTN electrospun solution, nanofibers, and a sensor. The KNLTN nanofiber material of this invention possesses a high voltage constant. This KNLTN nanofiber material is used to fabricate pressure sensing elements. KNLTN nanofibers can be fabricated on a rigid substrate using electrospinning technology to obtain a flexible pressure sensor with an ultra-high voltage constant nanofiber, thus solving the problems of low sensitivity and toxicity associated with piezoelectric sensors. This invention features a simple fabrication process, high yield, and no pollution during manufacturing.

Description

Technical Field

[0001] This invention relates to the field of voltage-type pressure sensors, and particularly to a method for processing KNLTN electrospun liquid, nanofibers, and sensors. Background Technology

[0002] Sensors are playing an increasingly important role in many fields as a means of perception. Among them, pressure sensors can convert sensed force into changes in electrical signals. Pressure sensors have a wide range of applications. In wearable and implantable devices, flexible pressure sensors, because they can be in close contact with the human body, expand our perception. By detecting various health-related information in real time, such as breathing, heart rate, and blood flow rate, they can play a role in health monitoring, timely feedback and early warning, and even disease diagnosis.

[0003] With the continuous development of sensor technology in miniaturization, intelligence, and networking, people have placed higher demands on sensors. The electronic devices we use in our lives have undergone tremendous changes, requiring not only improved sensitivity, anti-interference and noise immunity, but also miniaturization, integration, and low power consumption. With the development of wireless communication and 5G technology, smart homes are gradually entering ordinary households, and the normal operation of our society is increasingly inseparable from various sensors. This rapid development has also brought enormous challenges to the power supply of countless miniaturized sensors. Under current technological conditions, energy supply still relies on external power sources or batteries, which not only has significant limitations in use but also presents many inconveniences in later maintenance. For example, regular battery replacement is required, wiring is difficult, and for implanted sensors, batteries pose safety hazards and require surgery for replacement, resulting in high maintenance costs. Therefore, using energy conversion materials to directly obtain energy from the environment and convert it into electrical energy to power sensors, developing sustainable, self-powered sensors, is a promising research direction.

[0004] While lead-based piezoelectric materials possess high piezoelectric constants, the toxicity of lead-containing substances makes them less desirable. In recent years, pressure sensors based on lead-free piezoelectric low-dimensional nanomaterials have become a hot topic in flexible sensing applications, but the piezoelectricity of lead-free piezoelectric materials is generally low. Potassium sodium niobate (K...) 0.5 Na 0.5NbO3 (KNN) piezoelectric materials belong to the typical perovskite ABO3 type structure, possessing characteristics such as high Curie temperature (Tc = 420℃), low dielectric constant, good piezoelectric properties, high electromechanical coupling coefficient (kp ≈ 40%), and good biocompatibility, making them considered one of the most promising lead-free piezoelectric materials. KNN piezoelectric materials exhibit an orthorhombic hexahedral structure (R phase) at low temperatures, generally an orthorhombic structure (O phase) at room temperature, and a tetragonal structure (T phase) as the temperature rises to 200℃. Further increases above the Curie temperature result in a cubic structure (C phase). The piezoelectric constant of existing KNN-based materials is generally below 200 pm / V. The fabrication of KNN nanofibers using spinning for high-performance pressure sensor devices has not been documented in published literature or patents. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for processing KNLTN electrospinning solution, nanofibers, and sensors. The KNLTN nanofiber material of this invention possesses a high voltage constant. This KNLTN nanofiber material is used to fabricate pressure sensing elements. KNLTN nanofibers can be fabricated on a rigid substrate using electrospinning technology over a large area, resulting in a flexible pressure sensor with an ultra-high voltage constant nanofiber, thus solving the problems of low sensitivity and toxicity associated with piezoelectric sensors. This invention features a simple fabrication process, high yield, and no pollution during the manufacturing process.

[0006] The technical solution of this invention is: a KNLTN nanofiber, characterized in that it comprises the following components by weight: 0.2-0.3 parts anhydrous potassium acetate, 0.1-0.2 parts anhydrous sodium acetate, 0.01-0.02 parts anhydrous lithium acetate, 6-8 parts ethylene glycol methyl ether, 1.2-1.4 parts glacial acetic acid, 1-2 parts acetylacetone, 0.6-1.0 parts niobium ethoxide, 0.1-0.6 parts tantalum ethoxide, and 1-2 parts polyvinylpyrrolidone (PVP). (Parts by weight refer to mass)

[0007] According to the above description, a KNLTN nanofiber is characterized by: 0.220 parts of anhydrous potassium acetate, 0.171 parts of anhydrous sodium acetate, 0.017 parts of anhydrous lithium acetate, 6.67 parts of ethylene glycol methyl ether, 1.34 parts of glacial acetic acid, 2 parts of acetylacetone, 0.71 parts of niobium ethoxide, 0.39 parts of tantalum ethoxide, and 2.0 parts of polyvinylpyrrolidone.

[0008] This invention also discloses a method for preparing KNLTN electrospinning solution, the specific steps of which are as follows:

[0009] (1) Add 0.2 to 0.3 parts by weight of potassium acetate, 0.1 to 0.2 parts by weight of sodium acetate, and 0.01 to 0.02 parts by weight of lithium acetate to a mixed solution of 0.6 to 0.7 parts by weight of glacial acetic acid and 3 to 4 parts by weight of ethylene glycol methyl ether, and then add 0.7 to 1.2 parts by weight of acetylacetone. Seal and stir until the powder is completely dissolved to obtain solution A.

[0010] (2) In a nitrogen-filled chamber with a humidity of less than 0.1%RH, add 0.6 to 1 part by weight of niobium ethoxide and 0.1 to 0.6 parts by weight of tantalum ethoxide to a mixed solution of 0.4 to 0.8 parts by weight of glacial acetic acid and 2.0 to 3.0 parts by weight of ethylene glycol methyl ether, and then add 0.7 to 1.2 parts by weight of acetylacetone. After sealing and stirring for a certain period of time, solution B is obtained.

[0011] (3) Mix solution A and solution B at a volume ratio of 1:1; stir at a constant temperature of 90℃ for a certain period of time to obtain solution C;

[0012] (4) Take 5 to 15 parts by weight of anhydrous ethanol, then weigh 1 to 2 parts by weight of polyvinylpyrrolidone and dissolve it in it. After stirring for a certain time, liquid D is obtained. Mix equal volumes of solution C and solution D. After stirring thoroughly, KNLTN electrospinning solution precursor is obtained.

[0013] This invention also discloses a method for preparing KNLTN nanofibers, which uses the KNLTN electrospinning solution as described above, and further includes the following steps:

[0014] (1) Select silicon wafers (Si / SiO2), and ultrasonically clean the silicon wafers with acetone, anhydrous ethanol and deionized water for 10-30 min respectively, and dry them in air at 40-60℃ for 20-50 min.

[0015] (2) Place the silicon wafer on the front of the receiving plate and load the KNLTN electrospinning solution precursor solution into the syringe. Perform electrospinning under the following conditions: temperature 25-35℃, humidity below 30%, voltage 10-12kV, distance between needle tip and receiving plate 10cm, and injection pump push speed 0.2mL / h.

[0016] (3) The substrate covering the spinning is heated from room temperature to 420-470°C at a rate of 10°C / min, kept at the temperature for a certain time, and then heated to 620-670°C at a rate of 10°C / min. After being kept at the temperature for a certain time again, it is naturally cooled to room temperature to form KNLTN nanofibers.

[0017] This invention also discloses a method for fabricating a KNLTN nanofiber sensor, using KNLTN nanofibers as described above.

[0018] (1) Lay the KNLTN nanofiber silicon wafer flat, and drop a layer of PDMS silicone on the KNLTN nanofiber with a thickness of 0.9 mm to 1.1 mm. Bake to cure the PDMS silicone layer.

[0019] (2) Peel off the PDMS silicone layer along one corner to obtain a layer of KNLTN nanofibers;

[0020] (3) A gold electrode is deposited on both sides of the nanofibers attached to the PDMS silicone layer. The electrode width is about 2.5 mm, the electrode spacing is 5 mm, and the electrode direction is perpendicular to the arrangement direction of the nanofibers.

[0021] (4) Lead wires out from the electrode with silver paste, and then coat the nanofiber with another layer of PDMS silicone for encapsulation. The PDMS is cured to form a pressure sensor.

[0022] According to the KNLTN nanofiber sensor fabrication method described above, the electrode thickness is 100 nm, the width is 2.5 mm, and the electrode spacing is 5 mm.

[0023] The present invention also discloses a KNLTN nanofiber sensor, comprising a polydimethylsiloxane silica gel layer and nanofibers. The nanofibers comprise the following components by weight: 0.2-0.3 parts of anhydrous potassium acetate, 0.1-0.2 parts of anhydrous sodium acetate, 0.01-0.02 parts of anhydrous lithium acetate, 6-8 parts of ethylene glycol methyl ether, 1.2-1.4 parts of glacial acetic acid, 1-2 parts of acetylacetone, 0.6-1 part of niobium ethoxide, 0.1-0.6 parts of tantalum ethoxide, and 1-2 parts of polyvinylpyrrolidone.

[0024] The beneficial effects of the present invention are as follows: (1) The present invention requires only a small amount of nanofibers to realize the pressure sensing function, and the preparation is simple and low cost. (2) The present invention uses KNLTN nanofibers as raw materials to prepare a flexible pressure sensor with an ultra-fast response time, and the output voltage of the sensor varies greatly under different pressures. (3) The present invention has a sensitivity of 43.97mV / kPa and a response time of only 5ms, which can distinguish human movement. Attached Figure Description

[0025] Figure 1 This is a SEM image of the KNLTN nanofibers from Example 2 of the present invention.

[0026] Figure 2 The image shows the XRD phase diagram of the KNLTN nanofibers of Example 1 of this invention.

[0027] Figure 3 This is the XRD phase diagram of the KNLTN nanofibers in Example 2 of the present invention.

[0028] Figure 4 The image shows the XRD phase diagram of the KNLTN nanofibers in Example 3 of this invention.

[0029] Figure 5 This is the PFM amplitude diagram of the KNLTN nanofibers in Example 2 of the present invention.

[0030] Figure 6 The output voltage curves of the flexible pressure sensor assembled from KNLTN nanofibers in Embodiment 1 of the present invention are shown under different stress conditions.

[0031] Figure 7 The output voltage curves of the flexible pressure sensor assembled from KNLTN nanofibers in Embodiment 2 of the present invention are shown under different stress conditions.

[0032] Figure 8 The output voltage curves of the flexible pressure sensor assembled from KNLTN nanofibers in Embodiment 3 of the present invention are shown under different stress conditions.

[0033] Figure 9 This is a cyclic curve of the flexible pressure sensor assembled from KNLTN nanofibers according to Example 2 of the present invention.

[0034] Figure 10 The output voltage curve of the flexible pressure sensor assembled from KNLTN nanofibers in Embodiment 2 of the present invention when tapped.

[0035] Figure 11 This is a graph showing the output voltage of the flexible pressure sensor assembled from KNLTN nanofibers according to Embodiment 2 of the present invention during walking.

[0036] Figure 12 The output voltage curve of the flexible pressure sensor assembled with KNLTN nanofibers according to Embodiment 2 of the present invention during jogging.

[0037] Explanation of the name: KNLTN --- Potassium sodium lithium tantalate niobate. Detailed Implementation

[0038] The present invention will be further described below with reference to embodiments. The following description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make equivalent modifications to the disclosed technical content to create equivalent embodiments. Any simple modifications or equivalent changes made to the following embodiments based on the technical essence of the present invention without departing from the scope of the invention are all within the protection scope of the present invention.

[0039] This invention discloses a KNLTN nanofiber comprising, by weight, the following components: 0.2-0.3 parts anhydrous potassium acetate, 0.1-0.2 parts anhydrous sodium acetate, 0.01-0.02 parts anhydrous lithium acetate, 6.0-8.0 parts ethylene glycol methyl ether, 1.2-1.4 parts glacial acetic acid, 1.0-2.0 parts acetylacetone, 0.6-1.0 parts niobium ethoxide, 0.1-0.6 parts tantalum ethoxide, and 1-2 parts polyvinylpyrrolidone (PVP). The lead-free nanofiber exhibits a piezoelectric constant ranging from 80 pm / V to 120 pm / V, and the formulation is lead-free. (In this invention, all parts by weight are measured according to quality standards.)

[0040] Preferably, a sodium niobate nanofiber material comprises, by weight, the following components: 0.220 parts anhydrous potassium acetate, 0.171 parts anhydrous sodium acetate, 0.017 parts anhydrous lithium acetate, 6.67 parts ethylene glycol methyl ether, 1.34 parts glacial acetic acid, 2 parts acetylacetone, 0.71 parts niobium ethoxide, 0.39 parts tantalum ethoxide, and 2 parts polyvinylpyrrolidone. The average piezoelectric constant of the lead-free nanofiber is 522 pm / V.

[0041] This invention also discloses a method for preparing KNLTN nanofibers, the specific steps of which are as follows:

[0042] (1) Weigh 0.2-0.3 parts by weight of potassium acetate, 0.1-0.2 parts by weight of sodium acetate, and 0.01-0.02 parts by weight of lithium acetate and add them to a mixed solution of 0.6-0.7 parts by weight of glacial acetic acid and 3.0-4.0 parts by weight of ethylene glycol methyl ether. Then add 0.5-1.0 parts by weight of acetylacetone, seal, and stir at 700 rpm for 2-4 hours at room temperature until the powder is completely dissolved to obtain a clear, pale yellow transparent solution A.

[0043] (2) In a nitrogen-filled glove box with a humidity of less than 0.1% RH, add 0.6 to 1.0 parts by weight of niobium ethoxide and 0.1 to 0.6 parts by weight of tantalum ethoxide to a mixed solution of 0.6 to 0.7 parts by weight of glacial acetic acid and 3.0 to 4.0 parts by weight of ethylene glycol methyl ether, and then add 0.5 to 1.0 parts by weight of acetylacetone. Seal the container and stir at 700 rpm for 2 to 4 hours at room temperature to obtain a clear, pale yellow solution B.

[0044] (3) In the reflux condenser, use a syringe to slowly inject solution B into a three-necked round-bottom flask through the injection hole. After mixing with solution A that has been placed in the flask beforehand, the volume ratio of solution A to solution B is 1:1. After stirring at a constant temperature of 90°C and a speed of 700 rpm for 1 hour, a golden yellow transparent solution C is obtained. After the reaction is complete, the solution is removed, sealed, and stored.

[0045] (4) Measure 5-15 parts by weight of anhydrous ethanol, then weigh 1-2 parts by weight of polyvinylpyrrolidone (PVP) and dissolve it in the ethanol. Stir at 700 rpm for 12-14 hours at room temperature to obtain a colorless, transparent, viscous liquid D. Use a pipette to measure equal volumes of solution C and solution D, mix them together, and stir at 800 rpm for 2-4 hours at room temperature to obtain a viscous, pale yellow liquid, which is the KNLTN electrospinning solution precursor. Then, KNLTN nanofibers are prepared by electrospinning.

[0046] This invention also discloses a process for preparing KNLTN nanofibers by electrospinning, specifically including the following steps:

[0047] (1) Select a silicon wafer (i.e., a Si / SiO2 substrate), and ultrasonically clean the silicon wafer for 10-30 min with acetone, anhydrous ethanol and deionized water respectively, and dry it in air at 40-60℃ for 20-50 min.

[0048] (2) The silicon wafer is attached to the front of the receiving plate, and the KNLTN electrospinning solution precursor solution is loaded into the syringe. Electrospinning is performed under the following conditions: temperature 25-35℃, humidity below 30%, voltage 10-12kV, distance between needle tip and receiving plate 10cm, and syringe advance speed 0.2mL / h. (The electrospinning device consists of: a high-voltage DC power supply, a syringe with a metal needle, a push pump, and a receiving plate. The needle is connected to the positive electrode, and the receiving plate is connected to the negative electrode, thereby forming a strong electric field between the needle and the receiving plate. The KNLTN electrospinning solution precursor solution is loaded into the syringe. Under the action of the electric field, the KNLTN electrospinning solution precursor solution at the needle tip flies out from the needle tip to the receiving plate, and is drawn into filaments during flight to form fibers.)

[0049] (3) The substrate covering the spinning process is heated from room temperature to 420–470°C at a rate of 10°C / min, held at this temperature for a certain time, then heated to 620–670°C at a rate of 10°C / min, held at this temperature again for a certain time, and then naturally cooled to room temperature to obtain pure KNLTN nanofibers. (In this invention, PVP was added when preparing the electrospinning solution precursor, so the nanofibers before annealing were actually KNLTN / PVP nanofibers. After annealing, PVP burned and decomposed, and KNLTN also gained better crystallinity due to annealing, so it can be said to be pure.)

[0050] Specifications of materials used in the preparation of KNLTN nanofibers:

[0051]

[0052]

[0053] A method for fabricating KNLTN nanofiber sensors.

[0054] (1) After the annealing is completed, place the silicon wafer on a flat surface and apply a layer of PDMS silicone (i.e., polydimethylsiloxane silicone) onto the KNLTN nanofibers. The thickness is controlled between 0.9 mm and 1.1 mm, such as 1.0 mm. Place it in an oven at 80°C for a period of time until the PDMS silicone layer is cured.

[0055] (2) Lift up one corner of the PDMS silicone layer and peel it off slowly to obtain a layer of KNLTN nanofibers on the PDMS silicone layer.

[0056] (3) Using an electrostatic evaporator, an Au electrode with a thickness of about 100 nm is deposited on both sides of the nanofibers attached to the PDMS silicone layer. The electrode width is about 2.5 mm and the electrode spacing is 5 mm, so that the electrode direction is perpendicular to the arrangement direction of the nanofibers.

[0057] (4) Conductive silver paste is used to lead wires out from the gold electrode, and then a layer of PDMS silicone is deposited on the electrode again for encapsulation to protect the nanofibers. After standing at room temperature for a period of time until the PDMS is completely cured, a flexible self-powered pressure sensor based on PDMS and KNLTN nanofibers is obtained. This makes the response time of the present invention approximately 5ms and the sensitivity 14-44mV / kPa, which is fast and highly sensitive. Each pressure sensing function of the present invention only requires 0.017mL of electrospinning solution precursor solution to support it. A small amount of nanofibers can realize the pressure sensing function, making the pressure sensor small in size and meeting the needs of miniaturized applications, such as wearable devices.

[0058] The following are several specific embodiments of the present invention.

[0059] Example 1, a method for fabricating a KNLTN nanofiber flexible self-powered pressure sensor, includes the following steps:

[0060] (1) Dissolve 0.22g potassium acetate, 0.171g sodium acetate and 0.017g lithium acetate in a mixed solution of 0.667mL glacial acetic acid and 3.333mL ethylene glycol methyl ether, then add 1mL acetylacetone, seal, and stir at room temperature for 4h. After the powder is completely dissolved, solution A is obtained.

[0061] (2) In a nitrogen-filled glove box with humidity less than 0.1%RH, weigh 0.917g of niobium ethanol and 0.130g of tantalum ethanol and add them to a mixed solution of 0.667mL of glacial acetic acid and 3.333mL of ethylene glycol methyl ether. Then add 1mL of acetylacetone, seal the box, and stir at room temperature for 4h to obtain solution B.

[0062] (3) In the reflux condenser, take equal volumes of solution A and solution B. Use a syringe to slowly inject solution B into a three-necked round-bottom flask along the injection hole. After mixing with solution A that has been placed in it beforehand, keep the temperature at 90°C and stir at 700 rpm for 1 hour to obtain solution C. After the reaction is complete, take out the solution and seal it for storage.

[0063] (4) Measure 10 mL of anhydrous ethanol, then weigh 2 g of polyvinylpyrrolidone (PVP) and dissolve it in it. Stir at 700 rpm for 12-14 h at room temperature to obtain a colorless and transparent viscous liquid D. Use a pipette to measure equal volumes of solution C and solution D, mix them together, and stir at 800 rpm for 2-4 h at room temperature to obtain a viscous pale yellow liquid, which is the KNLTN electrospinning solution precursor.

[0064] (5) Select a 10mm×10mm silicon wafer, clean and dry it, and fix it on the receiving plate. Connect the metal needle to the positive terminal of the high-voltage DC power supply and the receiving plate to the negative terminal. The distance between the needle and the receiving plate is 10cm. The voltage is 10kV. The ambient temperature is 20~35℃ and the humidity is less than 30%. The injection pump push speed is 0.2mL / h. After electrospinning for 5min, turn off the high-voltage DC power supply, remove the silicon wafer from the receiving plate, put it into a quartz sintering boat, and then place it in an annealing furnace. Heat it from room temperature to 420~470℃ at a rate of 10℃ / min, hold it for a certain time (generally 1h is sufficient), then heat it to 620~670℃ at a rate of 10℃ / min, hold it for a certain time again (generally 1h is sufficient), and then cool it naturally to room temperature to obtain pure KNLTN nanofibers.

[0065] (6) After the annealing is finished, place the silicon wafer on a flat surface and apply a layer of PDMS silicone on the nanofibers. The thickness should be controlled at about 1 mm. Let it stand in an oven at 80°C for a period of time until the PDMS silicone layer is cured.

[0066] (7) Lift up one corner of the PDMS silicone layer and peel it off slowly to obtain a layer of KNLTN nanofibers on the PDMS silicone layer.

[0067] (8) Using an electrostatic evaporator, deposit an Au electrode about 100 nm thick on both sides of the nanofibers attached to the PDMS silicone layer. The electrode width is about 2.5 mm and the electrode spacing is 5 mm, so that the electrode direction is perpendicular to the arrangement direction of the nanofibers.

[0068] (9) Use conductive silver paste to lead the wires out from the gold electrode, and then apply another layer of PDMS silicone to the electrode for encapsulation to protect the nanofibers. After standing at room temperature for a period of time, the PDMS silicone layer is completely cured to obtain the KNLTN nanofiber flexible self-powered pressure sensor with PDMS silicone layer as the substrate.

[0069] The XRD pattern of the KNLTN-1 nanofibers prepared in this embodiment is shown below. Figure 2 As shown, the output voltage curves of the flexible pressure sensor assembled using KNLTN-1 nanofibers under different force conditions are as follows. Figure 6 As shown.

[0070] Example 2

[0071] (1) Dissolve 0.22g potassium acetate, 0.171g sodium acetate and 0.017g lithium acetate in a mixed solution of 0.667mL glacial acetic acid and 3.333mL ethylene glycol methyl ether, then add 1mL acetylacetone, seal, and stir at room temperature for 4h. After the powder is completely dissolved, a clear, pale yellow transparent solution A is obtained.

[0072] (2) In a nitrogen-filled glove box with a humidity of less than 0.1%RH, weigh 0.713g of niobium ethanol and 0.390g of tantalum ethanol and add them to a mixed solution of 0.667mL of glacial acetic acid and 3.333mL of ethylene glycol methyl ether. Then add 1mL of acetylacetone, seal the box, and stir at room temperature for 4h to obtain a clear, pale yellow transparent solution B.

[0073] (3) In the reflux condenser, take equal volumes of solution A and solution B. Use a syringe to slowly inject solution B into a three-necked round-bottom flask along the injection hole. After mixing with solution A that has been placed in it beforehand, keep the temperature at 90°C and stir at 700 rpm for 1 hour to obtain a golden yellow transparent solution C. After the reaction is complete, take out the solution and seal it for storage.

[0074] (4) Measure 10 mL of anhydrous ethanol, then weigh 2 g of PVP and dissolve it in it. Stir at 700 rpm for 12-14 h at room temperature to obtain a colorless and transparent viscous liquid D. Use a pipette to measure equal volumes of solution C and solution D, mix them together, and stir at 800 rpm for 2-4 h at room temperature to obtain the KNLTN electrospinning solution precursor.

[0075] (5) Select a 10mm×10mm silicon wafer, clean and dry it, and fix it on the receiving plate. Connect the metal needle to the positive terminal of the high-voltage DC power supply and the receiving plate to the negative terminal. The distance between the needle and the receiving plate is 10cm. The voltage is 10kV. The ambient temperature is 20~35℃ and the humidity is less than 30%. The injection pump push speed is 0.2mL / h. After electrospinning for 5min, turn off the high-voltage DC power supply, remove the silicon wafer from the receiving plate, put it into a quartz sintering boat, and then place it in an annealing furnace. Heat it from room temperature to 420~470℃ at a rate of 10℃ / min, hold it for a certain time, then heat it to 620~670℃ at a rate of 10℃ / min, hold it for a certain time again, and then cool it naturally to room temperature to obtain pure KNLTN nanofibers.

[0076] (6) After the annealing is complete, place the silicon wafer on a flat surface and apply a layer of PDMS silicone on the nanofibers. The thickness should be controlled at about 1 mm. Place it in an oven at 80°C for a period of time until the PDMS is cured.

[0077] (7) Lift up one corner of the PDMS silicone layer and peel it off slowly to obtain a layer of KNLTN nanofibers on the PDMS silicone layer.

[0078] (8) Using an electrostatic evaporator, deposit an Au electrode about 100 nm thick on both sides of the nanofibers attached to the PDMS silicone layer. The electrode width is about 2.5 mm and the electrode spacing is 5 mm, so that the electrode direction is perpendicular to the arrangement direction of the nanofibers.

[0079] (9) Use conductive silver paste to lead the wires out from the gold electrode, and then apply another layer of PDMS silicone to the electrode for encapsulation to protect the nanofibers. After standing at room temperature for a period of time, the PDMS silicone layer is completely cured to obtain the KNLTN nanofiber flexible self-powered pressure sensor with PDMS silicone layer as the substrate.

[0080] The SEM image of the KNLTN-2 nanofibers prepared in this embodiment is shown below. Figure 1 As shown, the XRD pattern is as follows Figure 3 As shown, the PFM amplitude diagram is as follows: Figure 5 As shown, the output voltage curves of the flexible pressure sensor under different force conditions are as follows: Figure 6 As shown in the figure, the cyclic curve of the flexible pressure sensor is as follows: Figure 9 As shown in the figure, the output voltage curve of the flexible pressure sensor when tapped is as follows: Figure 10 As shown in the figure, the output voltage curve of the flexible pressure sensor during walking is as follows: Figure 11 As shown in the figure, the output voltage curve of the flexible pressure sensor during jogging is as follows. Figure 12 As shown.

[0081] Example 3

[0082] (1) Dissolve 0.22g potassium acetate, 0.171g sodium acetate and 0.017g lithium acetate in a mixed solution of 0.667mL glacial acetic acid and 3.333mL ethylene glycol methyl ether, then add 1mL acetylacetone, seal, and stir at room temperature for 4h. After the powder is completely dissolved, a clear, pale yellow transparent solution A is obtained.

[0083] (2) In a nitrogen-filled glove box with a humidity of less than 0.1%RH, weigh 0.611g of niobium ethanol and 0.520g of tantalum ethanol and add them to a mixed solution of 0.667mL of glacial acetic acid and 3.333mL of ethylene glycol methyl ether. Then add 1mL of acetylacetone, seal the box, and stir at room temperature for 4h to obtain a clear, pale yellow transparent solution B.

[0084] (3) In the reflux condenser, take equal volumes of solution A and solution B. Use a syringe to slowly inject solution B into a three-necked round-bottom flask along the injection hole. After mixing with solution A that has been placed in it beforehand, keep the temperature at 90°C and stir at 700 rpm for 1 hour to obtain a golden yellow transparent solution C. After the reaction is complete, take out the solution and seal it for storage.

[0085] (4) Measure 10 mL of anhydrous ethanol, then weigh 2 g of PVP and dissolve it in it. Stir at 700 rpm for 12-14 h at room temperature to obtain a colorless and transparent viscous liquid D. Use a pipette to measure equal volumes of solution C and solution D, mix them together, and stir at 800 rpm for 2-4 h at room temperature to obtain the KNLTN electrospinning solution precursor.

[0086] (5) Select a 10mm×10mm silicon wafer, clean and dry it, and fix it on the receiving plate. Connect the metal needle to the positive terminal of the high-voltage DC power supply and the receiving plate to the negative terminal. The distance between the needle and the receiving plate is 10cm. The voltage is 10kV. The ambient temperature is 20~35℃ and the humidity is less than 30%. The injection pump push speed is 0.2mL / h. After electrospinning for 5min, turn off the high-voltage DC power supply, remove the silicon wafer from the receiving plate, put it into a quartz sintering boat, and then place it in an annealing furnace. Heat it from room temperature to 420~470℃ at a rate of 10℃ / min, hold it for a certain time, then heat it to 620~670℃ at a rate of 10℃ / min, hold it for a certain time again, and then cool it naturally to room temperature to obtain pure KNLTN nanofibers.

[0087] (6) After the annealing is finished, place the silicon wafer on a flat surface and apply a layer of PDMS silicone on the nanofibers. The thickness should be controlled at about 1 mm. Let it stand in an oven at 80°C for a period of time until the PDMS silicone layer is cured.

[0088] (7) Lift up one corner of the PDMS silicone layer and peel it off slowly to obtain a layer of KNLTN nanofibers on the PDMS silicone layer.

[0089] (8) Using an electrostatic evaporator, deposit an Au electrode about 100 nm thick on both sides of the nanofibers attached to the PDMS silicone layer. The electrode width is about 2.5 mm and the electrode spacing is 5 mm, so that the electrode direction is perpendicular to the arrangement direction of the nanofibers.

[0090] (9) Use conductive silver paste to lead the wires out from the gold electrode, and then apply another layer of PDMS silicone to the electrode for encapsulation to protect the nanofibers. After standing at room temperature for a period of time, the PDMS silicone layer is completely cured to obtain the KNLTN nanofiber flexible self-powered pressure sensor with PDMS silicone layer as the substrate.

[0091] The XRD pattern of the KNLTN-3 nanofibers prepared in this embodiment is shown below. Figure 4 As shown, the output voltage curves of the flexible pressure sensor assembled using KNLTN-3 nanofibers under different force conditions are as follows. Figure 8 As shown.

[0092] like Figure 1 As shown, KNLTN nanofibers exhibit a uniform morphology and a high aspect ratio. Figure 2 , 3 Figures 4 and 5 show the XRD patterns of Examples 1, 2, and 3, respectively. It can be seen that with Ta doping (Ta and Li are actually elemental dopants; potassium sodium niobate (KNN) has a perovskite ABO3 structure), doping allows Ta and Li to replace the B and A sites in KNN, respectively. The raw material for Ta is tantalum ethoxide (C... 10 H 25 With the increase of the proportion of anhydrous lithium acetate (CH3COOLi) in the TaO5 and Li raw materials, the XRD diffraction pattern of KNLTN nanofibers showed a peak shift. The XRD pattern of Example 1 showed an orthorhombic phase, corresponding to JCPDS card number No: 32-0822. With the increase of the Ta doping ratio, the XRD pattern of Example 2 showed both diffraction peaks corresponding to the orthorhombic phase and diffraction peaks corresponding to the tetragonal phase. With the further increase of the Ta doping ratio, the XRD pattern of Example 3 showed a tetragonal phase, corresponding to JCPDS card number No: 71-0945, indicating that Ta doping caused the structure of KNLTN to change at room temperature. Figure 5 The image shows the PFM amplitude diagram of a single KNLTN-2 nanofiber from Example 2. It can be seen that there is a distinct butterfly-shaped hysteresis loop, indicating that the KNLTN nanofiber does indeed have piezoelectric properties. Figure 6 , 7Figures 8 and 9 show the output voltage curves of the flexible pressure sensors assembled from KNLTN nanofibers in Examples 1, 2, and 3, respectively, under different stress conditions. With the increase of the Ta doping ratio, the output voltage of the pressure sensor in Example 2 increases significantly, while with a further increase in the Ta doping ratio, the output voltage of the pressure sensor in Example 3 decreases. The increase in output voltage is due to the structural change of the KNLTN nanofibers caused by Ta doping. Figure 9 The figure shown is a cyclic curve of the KNLTN-2 nanofiber flexible pressure sensor from Example 2. Figure 10 The figure shown is the output voltage curve of the KNLTN-2 nanofiber flexible pressure sensor in Example 2 when tapped. Figure 11 The figure shown is the output voltage curve of the KNLTN-2 nanofiber flexible pressure sensor in Example 2 during walking. Figure 12 The figure shows the output voltage curve of the KNLTN-2 nanofiber flexible pressure sensor in Example 2 during jogging. This flexible pressure sensor has an ultrafast response time of 5ms and a sensitivity of 43.97mV / kPa. Its high sensitivity and fast response time make it a promising candidate for wearable devices.

[0093] The principle of this invention is as follows: This invention employs the sol-gel method, electrospinning process, and self-assembly technology to obtain KNLTN nanofibers with good crystallinity through annealing. Li and Ta co-doping induces the O-T phase transition in KNLTN at room temperature, thereby enhancing its piezoelectric constant. Sensors assembled with these nanofibers exhibit ultrafast response times and generate a large output voltage upon receiving pressure, thus yielding a self-powered flexible pressure sensor. (When the sensor senses a pressure change, it generates an AC output voltage signal, which can be received, stored, or even used to power some microsensors.)

Claims

1. A method for preparing KNLTN nanofibers, characterized by, The specific steps are as follows: First, a KNLTN electrospinning liquid precursor is prepared, and the specific steps are as follows: (1) 0.1-0.2 parts by weight of sodium acetate, 0.2-0.3 parts by weight of potassium acetate, and 0.01-0.02 parts by weight of lithium acetate are added to a mixed solution of 0.6-0.7 parts by weight of glacial acetic acid and 3.0-4.0 parts by weight of ethylene glycol methyl ether, and then 0.7-1.2 parts by weight of acetylacetone is added, sealed and stirred, and the powder is completely dissolved to obtain solution A; (2) In a nitrogen-filled box with a humidity of less than 0.1% RH, 0.6-1.0 parts by weight of niobium ethoxide and 0.1-0.6 parts by weight of tantalum ethoxide are added to a mixed solution of 0.6-0.7 parts by weight of glacial acetic acid and 3.0-4.0 parts by weight of ethylene glycol methyl ether, and then 0.7-1.2 parts by weight of acetylacetone is added, sealed and stirred, and the powder is completely dissolved to obtain solution B; (3) Mix solution A and solution B at a volume ratio of 1:1; stir at 90°C to obtain solution C; (4) Measure 5.0-15.0 parts by weight of anhydrous ethanol, then weigh 1.0-2.0 parts by weight of polyvinylpyrrolidone and dissolve it in the anhydrous ethanol, and stir to obtain liquid D; mix equal volumes of solution C and solution D; after stirring, a KNLTN electrospinning liquid precursor is obtained; Then, a KNLTN nanofiber is prepared using the KNLTN electrospinning liquid precursor, and the following steps are included: (5) Select a silicon wafer, and ultrasonically clean the silicon wafer with acetone, anhydrous ethanol and deionized water for 10-30 min, and dry in air at a temperature of 40-60°C for 20-50 min; (6) Attach the silicon wafer to the front of the receiving plate, and load the KNLTN electrospinning liquid precursor solution into a syringe, and perform electrospinning under the following conditions: temperature 25-35°C, humidity less than 30%, voltage 10-12 kV, distance between needle tip and receiving plate 10 cm, and injection pump advancing speed 0.2 mL / h; (7) Heat the substrate covered with the nanofiber from room temperature to 420-470°C at a rate of 10°C / min, maintain for a certain time, then heat to 620-670°C at a rate of 10°C / min, maintain for a certain time again, and then naturally cool to room temperature, to obtain a KNLTN nanofiber.

2. A method for processing a KNLTN nanofiber sensor, using the KNLTN nanofiber of claim 1, (1) Place the silicon wafer covered with the KNLTN nanofiber flat, and drop a layer of PDMS silicone rubber on the KNLTN nanofiber, with a thickness controlled at 0.9-1.1 mm, and bake to solidify the PDMS silicone rubber layer; (2) Lift the PDMS silicone rubber layer along one corner and peel it off to obtain a layer of KNLTN nanofiber; (3) Evaporate electrodes on both sides of the PDMS silicone rubber layer with the nanofiber adhered, with an electrode width of 2.5 mm, an electrode spacing of 5 mm, and the electrode direction perpendicular to the arrangement direction of the nanofiber; (4) Lead wires from the electrodes, and then drop another layer of PDMS silicone rubber on the electrodes for encapsulation, and the PDMS is solidified to obtain a pressure sensor.

3. The method of claim 2, wherein the KNLTN nanofiber sensor is processed by: The electrodes were 100 nm thick and 2.5 mm wide with a 5 mm spacing between electrodes.

4. The method of claim 2, wherein the KNLTN nanofiber sensor is processed by: The PDMS silicone layer was between 0.9 mm and 1.1 mm thick.

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