Particle filling type flexible piezoelectric composite material and preparation method and application thereof

Abstract

The invention belongs to the technical field of flexible piezoelectric materials, and particularly discloses a particle filling type flexible piezoelectric composite material and a preparation method and application thereof. The composite material is formed by compounding 40-90% by mass of piezoelectric particles and a flexible polymer matrix, the piezoelectric particles are uniformly dispersed in the flexible polymer matrix, and the preparation method comprises the steps of piezoelectric particle drying or modification pretreatment, ultrasonic-mechanical synergistic dispersion, composite slurry regulation and control, precise coating drying and hot pressing. The piezoelectric particles are ensured to be uniformly dispersed and tightly combined with a matrix interface, and agglomeration under high filling amount is inhibited. The piezoelectric sensor prepared on the basis of the composite material has the fracture strain larger than or equal to 280%, has good flexibility, can achieve rapid and stable electric signal output, can still keep stable performance after one million times of circulation, is applied to the fields of pulse wave monitoring, wearable equipment, robot bionic tactile sensation or precise industrial sensing and the like, and has wide application prospects. The problem that flexibility and performance of a traditional piezoelectric material are difficult to consider at the same time is solved.

Description

Technical Field

[0001] This invention belongs to the field of flexible piezoelectric materials technology, specifically relating to a particle-filled flexible piezoelectric composite material, its preparation method and application, which is suitable for wearable medical devices, robotic bionic tactile sensing, precision industrial sensing and other scenarios. Background Technology

[0002] With the rapid development of wearable electronics, soft robots, IoT sensing and medical health monitoring technologies, higher requirements are placed on the comprehensive performance of piezoelectric materials. They not only need to have excellent piezoelectric response sensitivity and signal resolution, but also need to take into account good flexibility, fit and long-term stability in order to adapt to application scenarios such as complex curved surface fitting and dynamic mechanical signal capture.

[0003] Currently, the mainstream fabrication routes for flexible piezoelectric composite materials include laminated and particle-filled types. Laminated composite materials suffer from inherent drawbacks such as single interface, significant stress concentration, and limited overall flexibility, making it difficult to meet the demands for thinner, lighter, and more reliable devices. Particle-filled composite materials, on the other hand, have become a core direction for achieving a balance between material flexibility and high performance due to their ability to construct a three-dimensional force-electric coupling network through filler dispersion and structural design. However, existing particle-filled flexible piezoelectric composite materials still face three major technological bottlenecks: First, flexibility and resolution are mutually restrictive. The signal resolution of sensing materials depends on a certain material stiffness, but increasing stiffness will lead to a decrease in flexibility, making it impossible to achieve a comfortable fit with human skin or flexible devices. On the other hand, traditional flexible polymer matrices are highly viscoelastic and easily absorb weak mechanical signal energy, resulting in a significant reduction in sensor resolution, which severely limits the application of materials in weak signal detection scenarios.

[0004] Secondly, the inorganic particles have poor dispersibility. Inorganic piezoelectric particles, represented by PZT (lead zirconate titanate), have poor compatibility with organic polymer matrices. In high-filling scenarios (especially when the mass fraction exceeds 50%), the particles are prone to agglomeration and sedimentation, making it difficult to form a uniform dispersion system. This results in large fluctuations and poor consistency in the piezoelectric properties of the composite material, making it impossible to achieve stable force-to-electric conversion.

[0005] Third, the interfacial bonding performance is insufficient. The interface between inorganic piezoelectric particles and the organic polymer matrix has different chemical properties and lacks effective interaction, resulting in weak interfacial bonding. During stress or cyclic use, problems such as particle debonding and interfacial peeling easily occur, which not only reduces the mechanical strength and flexibility of the composite material but also hinders the efficient transfer of stress between the particles and the matrix, thus affecting the piezoelectric conversion efficiency and the long-term durability of the material.

[0006] Furthermore, existing preparation processes lack systematic optimization of key aspects such as dispersion parameters, modification conditions, and film formation processes, resulting in poor performance reproducibility of composite materials and hindering industrial scale-up. These technical deficiencies collectively limit the large-scale application of particle-filled flexible piezoelectric composite materials in wearable health monitoring devices, robotic bionic tactile sensing, and precision industrial sensing. Therefore, developing a particle-filled flexible piezoelectric composite material that can overcome these bottlenecks and possess both high flexibility and high resolution has significant technological value and market demand. Summary of the Invention

[0007] The purpose of this invention is to solve the technical problems of existing flexible piezoelectric composite materials, such as the difficulty in balancing flexibility and resolution, uneven dispersion of inorganic particles, and poor interfacial bonding. This invention provides a particle-filled flexible piezoelectric composite material, its preparation method, and its application. It is prepared by an integrated process of ultrasonic-mechanical synergistic dispersion and rheological control film formation, which achieves uniform dispersion and strong interfacial bonding of piezoelectric particles at high filling amounts, while also possessing excellent flexibility and μN-level sensing resolution, meeting the application needs of wearable devices, precision sensing, and other fields.

[0008] To solve the above-mentioned technical problems, the present invention provides a method for preparing a particle-filled flexible piezoelectric composite material, comprising the following steps: (1) Ultrasonic-mechanical synergistic dispersion: piezoelectric particles are added to an organic solvent and dispersed by intermittent ultrasonication, while continuous mechanical stirring is performed to make the piezoelectric particles uniformly dispersed in the organic solvent to obtain a dispersion system; (2) Preparation of composite slurry: Add flexible polymer particles to the dispersion system, stir until the flexible polymer particles are completely dissolved, continue stirring to adjust the content of organic solvent in the system, and obtain composite slurry; (3) Coating and drying: The composite slurry is coated onto the stage, evaporated at room temperature, and then dried in steps until the organic solvent is completely evaporated to obtain the composite preform; (4) Hot pressing: The dried composite preform is placed in a flat vulcanizing machine for hot pressing to obtain a thin film-like particle-filled flexible piezoelectric composite material.

[0009] The preparation method of this invention breaks up the agglomeration of piezoelectric particles by intermittent ultrasonic local high-pressure shock waves and achieves global uniform mixing by continuous mechanical stirring. This effectively solves the problem of uneven particle dispersion and sedimentation under high filling volume. At the same time, the hot pressing process eliminates microscopic defects at the interface and promotes structural densification. Ultimately, while ensuring the excellent flexibility of the material, the piezoelectric performance and structural stability are significantly improved. The process has strong controllability and good repeatability, providing a reliable path for the large-scale preparation of high-performance flexible piezoelectric composite materials.

[0010] As a further description of the above technical solution: the mass ratio of piezoelectric particles to flexible polymers is 2:3 to 9:1, to obtain particle-filled flexible piezoelectric composite materials with a particle mass fraction ranging from 40% to 90%, thereby flexibly adapting to the performance requirements of different application scenarios: at low mass fractions (40% to 60%), the material has both superior flexibility and fit, and can seamlessly adapt to flexible fitting scenarios such as skin and complex curved surfaces; at medium to high mass fractions (60% to 90%), a highly efficient three-dimensional force-electric coupling network can be constructed through the high-density uniform distribution of particles, significantly improving the piezoelectric response sensitivity and mechanical sensing resolution. At the same time, ultrasonic-mechanical synergistic dispersion and hot pressing processes effectively avoid particle agglomeration and weak interface bonding problems under high filling amounts, achieving synergistic optimization of flexibility, piezoelectric performance and structural stability. This not only meets the comfortable fitting requirements of wearable devices, but also achieves the high-precision requirements of μN-level weak signal detection, adapting to diversified application scenarios from flexible electronic skin to precision industrial sensing.

[0011] As a further description of the above technical solution: the piezoelectric particles have a particle size range of 200nm to 5μm, which helps to achieve synergistic optimization of dispersion, interfacial bonding, and electromechanical conversion efficiency. Small-sized (200nm to 1μm) piezoelectric particles can form a denser contact interface with the polymer matrix due to their high specific surface area, enhancing interfacial interaction and stress transfer efficiency, while reducing stress concentration inside the composite material. Medium-sized (1μm to 5μm) piezoelectric particles can reduce the tendency to agglomerate in high-filling systems. Through the spatial stacking of spherical morphology, a continuous and efficient three-dimensional electromechanical coupling network is constructed, which improves the piezoelectric response sensitivity. This avoids the performance unevenness caused by excessive agglomeration of piezoelectric particles and overcomes the defect of large-sized particles destroying the flexibility of materials. Combined with ultrasonic-mechanical synergistic dispersion and hot pressing processes, it can ensure that the piezoelectric particles are uniformly distributed in the flexible polymer matrix, so that the composite material can stably achieve μN-level mechanical sensing resolution while maintaining excellent flexibility, adapting to diverse scenarios from wearable devices that fit the skin to industrial precision sensing.

[0012] As a further description of the above technical solution: the piezoelectric particles are modified piezoelectric particles with a silane coupling agent surface modified. The surface modification process is as follows: a silane coupling agent is mixed with an alcohol solution to prepare a modifier dilution; the piezoelectric particles are added to the modifier dilution; and after ultrasonic treatment, pretreatment, and drying, the modified piezoelectric particles are obtained. The silane coupling agent is preferably one or more of KH-550, KH-560, and KBM-503. These silane coupling agents all share the common characteristics of strong reactivity with the hydroxyl groups on the surface of the piezoelectric particles and good compatibility with the flexible polymer matrix. They can efficiently construct a stable active interface layer through hydrolysis-grafting reactions, fundamentally solving key problems such as uneven dispersion and weak interfacial bonding between inorganic piezoelectric particles and organic polymer matrices.

[0013] As a further description of the above technical solution: the flexible polymer is preferably polyurethane (PU). Polyurethane combines ultra-high flexibility similar to skin and cartilage with excellent mechanical toughness, ensuring that the composite material maintains its structural integrity under bending, stretching, and other deformations, meeting the flexible fit requirements of wearable devices; the active functional groups on its molecular chain can form strong chemical bonds with the silane coupling agent on the surface of modified piezoelectric particles, while also having good wetting and encapsulation capabilities for unmodified piezoelectric particles, significantly improving interfacial bonding stability and stress transfer efficiency; PU has excellent solubility in organic solvents such as tetrahydrofuran (THF), and the rheological properties of the composite slurry can be precisely adjusted by controlling the solvent ratio, adapting to precision coating and stepped drying processes, avoiding defects such as cracking and porosity during film formation; in addition, PU also has excellent aging resistance and chemical stability, and combined with hot pressing densification process, it can further improve the structural density of the composite material, ensuring that the sensor maintains stable piezoelectric output after multiple cycle tests, providing a core guarantee for the long-term reliable application of the material in wearable medical, industrial sensing and other fields.

[0014] As a further description of the above technical solution: the organic solvent is preferably THF (tetrahydrofuran), which can not only provide a liquid medium for ultrasonically dispersed modified PZT particles and dissolve polyurethane, but also facilitate subsequent rapid volatilization and removal.

[0015] As a further description of the above technical solution: the hot pressing pressure is 6-8 MPa, and the hot pressing time is 2-5 hours. The hot pressing process can effectively eliminate the micropores and interface defects caused by solvent evaporation during the drying process of the composite preform, promote the close adhesion between piezoelectric particles and flexible polymer matrix, and avoid particle agglomeration or matrix embrittlement caused by high pressure, thus ensuring that the flexibility of the material is not damaged.

[0016] This invention also provides a particle-filled flexible piezoelectric composite material prepared according to the above-described preparation method. The particle-filled flexible piezoelectric composite material consists of piezoelectric particles and a flexible polymer matrix. The piezoelectric particles, after uniform dispersion, form a continuous three-dimensional force-electric coupling network with the flexible polymer matrix. This not only increases the overall elastic modulus of the composite material by introducing piezoelectric particles, solving the testing instability problem caused by polymer viscoelasticity, but also optimizes device performance by increasing the piezoelectric particle content. Simultaneously, the composite material utilizes a silane coupling agent to modify and construct an active interface layer on the surface of the piezoelectric particles, forming covalent or hydrogen bonds with the flexible polymer matrix. Combined with the synergistic effect of uniform particle dispersion and the three-dimensional force-electric coupling network, this not only overcomes the technical pain points of uneven piezoelectric particle dispersion and weak interfacial bonding in traditional flexible piezoelectric materials, but also achieves synergistic optimization of flexibility and piezoelectric properties. Its fracture strain is ≥280%, and the resolution reaches the μN level. It possesses both excellent flexibility and high-efficiency force-electric conversion capability, significantly improving the material's mechanical stability, signal transmission efficiency, and piezoelectric response reliability, providing a high-quality core material for the fabrication of high-performance flexible sensor devices.

[0017] This invention also provides the application of the above-mentioned particle-filled flexible piezoelectric composite material in the preparation of flexible piezoelectric sensors. The flexible piezoelectric sensor is made of particle-filled flexible piezoelectric composite material through electrode preparation and polarization treatment. Its mechanical sensing resolution is ≤5μN (corresponding to pressure resolution ≤0.05Pa), fracture strain is ≥280%, bending angle is ≥120°, signal-to-noise ratio is ≥43dB, sensitivity is ≥22 V / kPa, response time is ≤11.5ms, and the performance degradation rate is ≤10% after 1 million cycles of testing.

[0018] As a further description of the above technical solution: the flexible piezoelectric sensor is applied in the fields of pulse wave monitoring, wearable devices, robotic bionic tactile sensing, or precision industrial sensing.

[0019] Compared with the prior art, the beneficial effects of the present invention are: This invention employs an intermittent ultrasonic-mechanical synergistic dispersion process. By expanding the range of key parameters such as ultrasonic power, processing time, and stirring speed, it successfully solves the problem of piezoelectric particle agglomeration and sedimentation under different solid contents, ensuring uniform dispersion of piezoelectric particles in a flexible polymer matrix and guaranteeing the stability and consistency of material properties. The hot-pressing process effectively eliminates microscopic pores and interface defects caused by solvent evaporation during the drying process of the composite preform, promoting close adhesion between piezoelectric particles and the flexible polymer matrix, while avoiding particle agglomeration or matrix embrittlement caused by high pressure, ensuring that the material's flexibility is not compromised. The prepared composite material possesses both excellent flexibility and high response resolution, with a mechanical sensing resolution ≤5μN (corresponding to a pressure resolution ≤0.05Pa), a signal-to-noise ratio ≥43dB, a sensitivity ≥22V / kPa, and a response time ≤11.5ms. Furthermore, its performance remains stable after 1 million cycles of testing. The expanded parameter range allows the material to be flexibly adjusted according to different application scenarios, meeting the diverse requirements of the flexible sensing field. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the preparation process of particle-filled flexible piezoelectric composite film.

[0021] Figure 2 This is a schematic diagram of the modification mechanism of silane coupling agents.

[0022] Figure 3 This is a schematic diagram of the experimental setup and principle of ultrasonic dispersion.

[0023] Figure 4 This is a scanning electron microscope (SEM) image of the composite material prepared in Example 1.

[0024] Figure 5 This is a scanning electron microscope (SEM) image of the composite material prepared in Example 2.

[0025] Figure 6 This is a schematic diagram of the fabrication process of a particle-filled flexible piezoelectric sensor.

[0026] Figure 7 This is a schematic diagram of the finished product appearance and internal structure of a particle-filled flexible piezoelectric sensor.

[0027] Figure 8 This is a test diagram of the mechanical properties of a particle-filled flexible piezoelectric sensor.

[0028] Figure 9 This is a test diagram of the electrical performance of a particle-filled flexible piezoelectric sensor.

[0029] Figure 10 This is the result of a 1,000,000-cycle test of a particle-filled flexible piezoelectric sensor.

[0030] Figure 11 This is a test diagram of a particle-filled flexible piezoelectric sensor applied to pulse wave monitoring. Detailed Implementation

[0031] The claims of the present invention will be further described in detail below with reference to specific embodiments, but this does not constitute any limitation on the present invention. Any limited modifications made by any person within the scope of protection of the claims of the present invention are still within the scope of protection of the claims of the present invention.

[0032] Example 1 The preparation method of particle-filled flexible piezoelectric composite materials is as follows: Figure 1 As shown, it includes the following steps: (1) Surface modification of piezoelectric particles: First, 1g of silane coupling agent KH-560 was mixed with 99g of 95% ethanol solution to prepare a 1% mass fraction of silane coupling agent KH-560 modifier dilution; then, 40g of lead zirconate titanate (PZT) piezoelectric particles with a particle size of 200nm~5μm were added to the modifier dilution and ultrasonically treated with 800W power for 20min to achieve uniform surface modification of PZT piezoelectric particles; after ultrasonic treatment, the mixture was pretreated in a 40℃ environment for 10min, and then transferred to a 120℃ oven for continuous drying until constant weight to obtain modified PZT particles; the coupling mechanism is as follows. Figure 2 As shown, the silane coupling agent connects PZT piezoelectric particles (inorganic substrate) and PU matrix (organic material) through four steps of hydrolysis, condensation, dehydration and bonding, thus solving the problem of poor interfacial compatibility between the two and enhancing the interfacial bonding strength.

[0033] (2) Ultrasonic-mechanical synergistic dispersion: Weigh 40g of modified PZT particles and add them to a reactor containing 400g of tetrahydrofuran (THF). Dispersion is carried out using an ultrasonic disperser. Figure 3 (As shown) Ultrasonic dispersion was performed at a power of 1200W for a total processing time of 40 minutes. The ultrasonic mode was set to intermittent operation of "on for 20 seconds - off for 10 seconds". Simultaneously, a homogenizer at 500 rpm was used for continuous stirring to ensure uniform dispersion of the modified PZT particles in THF, preventing localized overheating and agglomeration. Through ultrasonic dispersion, the originally agglomerated large particles were dispersed into independent small particles. Bubbles may be generated during this process, such as... Figure 3 The principle diagram is shown.

[0034] (3) Preparation of composite slurry: After ultrasonic dispersion, 60g of polyurethane (PU) particles were added to the reactor, the stirring speed was adjusted to 800r / min, and the stirring was continued until the PU was completely dissolved. Then, the stirring was continued to allow THF to slowly evaporate to about 225g (the mass ratio of PU to THF was 1:4.5) to obtain composite slurry. (4) Coating and drying: Slowly pour the composite slurry onto the stage of the flat plate coater and coat it at a speed of 1000 mm / min. After coating, evaporate it at room temperature for 48 hours. After the film is initially formed, demold it and transfer it to a 40°C oven to dry for 24 hours. Finally, place it in a 60°C oven to dry for 1 week to ensure that THF is completely volatilized and obtain the composite preform. (5) Hot pressing: The dried composite blank is placed in a flat vulcanizing machine and hot pressed for 3 hours under a pressure of 8MPa to obtain a thin film-shaped particle-filled flexible piezoelectric composite material.

[0035] The particle-filled flexible piezoelectric composite material prepared in this embodiment consists of surface-modified PZT piezoelectric particles and a polyurethane (PU) matrix. The modified PZT piezoelectric particles are uniformly dispersed within the PU matrix, forming a continuous three-dimensional force-electric coupling network. Its scanning electron microscope (SEM) image is shown below. Figure 4 As shown, the low-magnification SEM image on the left shows that a large number of modified PZT nanoparticles are uniformly distributed in the PU matrix without obvious agglomeration and are evenly dispersed; the high-magnification SEM image on the right clearly shows that the modified PZT piezoelectric particles are tightly bonded to the PU matrix interface without obvious gaps, which verifies the modification effect of the silane coupling agent and provides a structural basis for the continuity of the three-dimensional network.

[0036] Example 2 A method for preparing particle-filled flexible piezoelectric composite materials includes the following steps: (1) Ultrasonic-mechanical synergistic dispersion: Weigh 45g of dried barium titanate (BaTiO3) piezoelectric particles and add them to a reactor containing 35g of tetrahydrofuran (THF). Ultrasonic dispersion is performed at a power of 1400W for a total processing time of 50min. The ultrasonic mode is set to "on for 25s-off for 12s" intermittent operation. At the same time, a homogenizer with a speed of 600r / min is used for continuous stirring to ensure that the barium titanate piezoelectric particles are evenly dispersed in THF and to avoid local overheating and agglomeration. (3) Preparation of composite slurry: After ultrasonic dispersion, add 5g of polyurethane (PU) particles to the reactor, adjust the stirring speed to 900r / min, stir until PU is completely dissolved, and continue stirring to allow THF to slowly evaporate to about 20g (the mass ratio of PU to THF is 1:4) to obtain composite slurry; (4) Coating and drying: Slowly pour the composite slurry onto the stage of the flat plate coater and coat it at a speed of 1200 mm / min. After coating, evaporate it at room temperature for 60 hours. After the film is initially formed, demold it and transfer it to a 45°C oven to dry for 36 hours. Finally, place it in a 55°C oven to dry for 8 days to ensure that THF is completely volatilized and obtain the composite preform.

[0037] (4) Hot pressing: The dried composite preform is placed in a flat vulcanizing machine and hot pressed for 5 hours under a pressure of 6MPa to obtain a thin film-shaped particle-filled flexible piezoelectric composite material.

[0038] The particle-filled flexible piezoelectric composite material prepared in this embodiment consists of barium titanate piezoelectric particles and a polyurethane (PU) matrix. The barium titanate piezoelectric particles are uniformly dispersed within the PU matrix. Its scanning electron microscope (SEM) image is shown below. Figure 5 As shown in the low-magnification view on the left, barium titanate nanoparticles are uniformly distributed in the PU matrix. The particles do not have obvious agglomeration clusters and are in close contact with the matrix, but there are fine gaps at the interface. The high-magnification view on the right shows that the barium titanate piezoelectric particles are densely and irregularly stacked in the PU matrix. There is no large-area agglomeration or sedimentation, and the overall structure is relatively uniform.

[0039] Example 3 The fabrication method of a particle-filled flexible piezoelectric sensor is as follows: Figure 6 As shown, it includes the following steps: (1) Electrode preparation: The particle-filled flexible piezoelectric composite film prepared in Example 1 was cut into the required size and shape, and gold electrodes were sputtered on both sides of the film by magnetron sputtering. Then, aluminum foil electrodes were led out as conductive terminals. (2) Polarization treatment: The composite film with electrodes is immersed in silicone oil, and the oil temperature is controlled at 80℃. A polarization electric field of 20kV / mm is applied using a high-voltage DC power supply and polarization is continued for 1 hour. After polarization, the electric field is kept constant. After the system cools down to room temperature, the power supply is turned off and the sample is taken out. The particle-filled flexible piezoelectric sensor is obtained. The appearance and internal structure of the finished product are shown in the figure. Figure 7 As shown, the particle-filled flexible piezoelectric sensor uses particle-filled flexible piezoelectric composite material as the core sensing layer, with flexible electrodes on both sides and electrode leads. It has the characteristics of flexibility and fit, making it suitable for wearable, pulse wave monitoring and other scenarios.

[0040] To verify the overall performance of the fabricated particle-type flexible piezoelectric sensor, its mechanical properties, electrical properties, and long-term stability were tested, as detailed below: (1) Mechanical property testing: such as Figure 8 As shown, the stress-strain curve on the left reflects the trend of force (stress) change of the sensor as deformation (strain) increases, and the fracture strain of the sensor can reach 280% to 730%. The stress and strain bar charts on the right corresponding to different proportions of modified PZT piezoelectric particles show that even when the proportion of PZT piezoelectric particles reaches 80wt%, the fracture strain of the sensor is still ≥280%, proving that it has good flexibility and can adapt to the deformation requirements of fitting, wearable and other scenarios. Moreover, the stress-strain curve is smooth without sudden drop, proving that external force can be uniformly transmitted through the network without local stress interruption.

[0041] (2) Electrical performance testing: such as Figure 9 As shown, by applying gradient pressure through a micro-force testing platform, the sensor can stably detect a weak mechanical signal of 5 μN, corresponding to a pressure resolution of 0.05 Pa; the signal-to-noise ratio is 43 dB, indicating strong anti-interference capability; the sensitivity is 22 V / kPa, demonstrating high response strength to pressure changes; and the response time is 11.5 ms, indicating fast response speed. Figure 6 As shown, this demonstrates that the sensor possesses both high-precision micro-signal recognition capabilities and the ability to achieve fast and stable electrical signal output, supporting its feasibility for application in scenarios such as pulse wave monitoring and precision industrial sensing.

[0042] (3) Long-term stability test: such as Figure 10 As shown, comparing the initial signal (0 cycles) with the signal after 1 million cycles, the voltage peak only fluctuated by about 2.8% (from 102.4mV to 173.8mV, with an actual attenuation rate of ≤10%). This means that after 1 million cycles, the voltage output of the sensor is stable with no significant attenuation, proving that the network structure of the composite material is stable and unbroken in the long term. This allows the sensor to maintain stable performance under long-term high-frequency use and has excellent durability.

[0043] (4) Practical application test: When the sensor is attached to the human wrist for pulse wave monitoring, it can clearly capture the percussion wave, tidal wave, and diabetic wave signals of the pulse wave, such as Figure 11 As shown, it can meet the needs of health monitoring.

[0044] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the present invention.

Claims

1. A method for preparing a particle-filled flexible piezoelectric composite material, characterized in that, Includes the following steps: (1) Ultrasonic-mechanical synergistic dispersion: piezoelectric particles are added to an organic solvent and dispersed by intermittent ultrasonication, while continuous mechanical stirring is performed to make the piezoelectric particles uniformly dispersed in the organic solvent to obtain a dispersion system; (2) Preparation of composite slurry: Add flexible polymer particles to the dispersion system, stir until the flexible polymer particles are completely dissolved, continue stirring to adjust the content of organic solvent in the system, and obtain composite slurry; (3) Coating and drying: The composite slurry is coated onto the stage, evaporated at room temperature, and then dried in steps until the organic solvent is completely evaporated to obtain the composite preform; (4) Hot pressing: The dried composite preform is placed in a flat vulcanizing machine for hot pressing to obtain a thin film-like particle-filled flexible piezoelectric composite material.

2. The preparation method according to claim 1, characterized in that: The mass ratio of the piezoelectric particles to the flexible polymer is 2:3 to 9:

1.

3. The preparation method according to claim 2, characterized in that: The piezoelectric particles have a particle size range of 200 nm to 5 μm.

4. The preparation method according to claim 3, characterized in that: The piezoelectric particles are modified piezoelectric particles that have undergone surface modification with a silane coupling agent. The surface modification process is as follows: a silane coupling agent is mixed with an alcohol solution to prepare a modifier dilution, the piezoelectric particles are added to the modifier dilution, and after ultrasonic treatment and pretreatment, they are dried to obtain modified piezoelectric particles.

5. The preparation method according to claim 4, characterized in that: The silane coupling agent is selected from one or more of KH-550, KH-560, and KBM-503.

6. The preparation method according to claim 2, characterized in that: The flexible polymer is polyurethane.

7. The preparation method according to claim 1, characterized in that: The hot pressing pressure is 6-8 MPa, and the hot pressing time is 2-5 h.

8. A particle-filled flexible piezoelectric composite material, characterized in that: It is prepared according to any one of claims 1-7.

9. The application of the particle-filled flexible piezoelectric composite material according to claim 8 in the preparation of flexible piezoelectric sensors.

10. The application according to claim 9, characterized in that: The flexible piezoelectric sensor described herein is applied in pulse wave monitoring, wearable devices, bionic tactile sensing for robots, or precision industrial sensing.

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