High-sensitivity flexible piezoelectric sensor and preparation method thereof

Abstract

The invention discloses a high-sensitivity flexible piezoelectric sensor and a preparation method thereof, and relates to the technical field of flexible piezoelectric sensors, through material system and process optimization, including centrifugal classification screening, mixed ultrasonic circulation process, surface modification, synergistic dispersion and novel structure design, the interface bonding force between piezoelectric particles and a matrix is enhanced, and the high-sensitivity flexible piezoelectric sensor is obtained. The distribution of functional groups on the surfaces of the particles is optimized, the defect of sensitivity of a traditional piezoelectric sensor is overcome, and the interface performance of the piezoelectric composite material and the sensitivity of the flexible sensor are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible piezoelectric sensors, and in particular to a highly sensitive flexible piezoelectric sensor and a preparation method thereof, which are mainly used in fields such as pulse detection. Background Art

[0002] As a new emerging high-performance sensing technology, flexible piezoelectric sensors show great application potential in many fields such as health detection, biomedicine, intelligent wearables, and human-computer interaction. For example, in the field of health detection, flexible piezoelectric sensors can accurately sense the weak mechanical signals generated by human pulse beats and efficiently convert them into voltage signals, providing strong support for real-time monitoring of the human health status. Since the accuracy of flexible piezoelectric sensors is determined by sensitivity, it is very important to optimize the sensitivity performance of the sensors.

[0003] In many fields such as precision instruments, biomedicine, and aerospace, flexible piezoelectric sensors have become essential components for physical quantity measurement. Taking the fields of mechanical engineering, aerospace, and medicine as examples, the sensitivity of flexible piezoelectric sensors plays a crucial role in the performance of the entire device. Flexible piezoelectric sensors are usually used to measure physical quantities such as the pressure, flow rate, and gravity of mechanical, gas, or liquid. To accurately capture weak signals, the sensors must have high sensitivity. In addition, in the field of health detection, piezoelectric sensors can sense the weak mechanical signals generated by the human body and convert them into voltage signals through the piezoelectric effect, so the sensitivity requirements for the sensors are extremely high.

[0004] Currently, the commonly used flexible piezoelectric sensors still have many deficiencies in actual applications, especially in terms of sensitivity. Currently, common optimization methods include microstructured design, interface contact resistance optimization, etc. Among them, the microstructured manufacturing method is usually complex in process, high in cost, and limited in the controllability of microstructures, making it difficult to achieve large-scale production. For interface contact resistance optimization, it usually depends on the design of microstructures. Once the microstructures are compressed to a certain extent, the electrical response will tend to saturate and it is difficult to further improve the sensitivity.

[0005] This limits the performance of flexible piezoelectric sensors in actual applications and makes them unable to fully play their due advantages. Therefore, a new flexible piezoelectric sensor is needed to solve the above-mentioned problems and defects and improve its detection sensitivity. Summary of the Invention

[0006] The purpose of the present invention is to provide a highly sensitive flexible piezoelectric sensor and a preparation method thereof, so as to solve the problem of low sensitivity of traditional piezoelectric sensors caused by uneven particle dispersion and weak interface bonding.

[0007] To achieve the above object, the present invention provides a method for preparing a highly sensitive flexible piezoelectric sensor, comprising the following steps:

[0008] S1. Particle pretreatment: Mix piezoelectric particles, organic particles and organic solvents in a certain proportion, ultrasonically disperse them evenly, heat and stir the mixed solution, adopt two-stage gradient standing, and control the phase separation of piezoelectric particles - organic phase by regulating the difference between the solvent evaporation rate and the particle sedimentation rate through temperature, perform centrifugation, add organic solvents, anhydrous ethanol and deionized water in sequence and then ultrasonically disperse them to thoroughly remove impurities, and dry for later use;

[0009] S2. Particle surface modification: Mix the piezoelectric particles obtained in step S1, modifiers and organic solvents in proportion, ultrasonically disperse them evenly, place them on a magnetic turntable for heating and rotational mixing, and dry for later use;

[0010] S3. Hot pressing and curing: Prepare a composite piezoelectric thin film from the particles modified in step S2 by the doctor blade method. When the matrix material reaches the elastoviscous state temperature, perform multi-stage hot pressing to optimize the interfacial bonding strength between the particles and the matrix to obtain a piezoelectric thin film;

[0011] S4. Gold plating and polarization: Sputter metal electrodes on the composite thin film prepared in step S3, and apply pressure polarization on the double-sided electrodes;

[0012] S5. Pre-stretch and encapsulate the sensor: Lay a layer of polymer film on the surface of the sensor prepared in S4 for encapsulation, fix it on the polymer tape with medical tape and pre-stretch it to obtain a flexible piezoelectric thin film sensor;

[0013] Preferably, in step S1, the piezoelectric particles are lead zirconate titanate (PZT), with an average particle size of 1 - 5 μm, the organic particles are polyvinyl chloride (PVC), and the organic solvent is tetrahydrofuran (THF). The mass ratio of the piezoelectric particles, organic particles and organic solvent is 1:4:15.

[0014] Preferably, in step S1, the ultrasonic dispersion adopts a pulse intermittent mode (working cycle 6s / intermittent cycle 7s), with a power of 10 - 30%, and suppresses particle agglomeration through dynamic cavitation effect, so that the PZT particles are evenly dispersed in the PVC-THF system.

[0015] Preferably, in step S1, the heating and stirring conditions are 50 - 70 °C, and the rotation speed is 800 - 1200 r / min. The segmented standing is the first stage of standing at 50 - 70 °C for 48 h, and the second stage of standing at 20 - 40 °C for 48 h.

[0016] Preferably, in step S1, the centrifugation speed is set to 3000 - 5000 r / min, the duration is set to 10 - 30 min, and it is repeated twice.

[0017] Preferably, in step S2, the power of the ultrasonic dispersion is 10 - 30%, which is divided into two stages: the first stage is 5 - 15 min, taken out and left standing for 100 - 150 s; the second stage is 5 - 15 min.

[0018] Preferably, in step S2, the modifier is silane coupling agent KBM - 503, and the organic solvent is acetone. The mass ratio of the piezoelectric particles, modifier and organic solvent is 1:0.075:3.

[0019] Preferably, in step S2, the heating and rotation conditions are 50 - 70 °C and the rotation speed is 400 - 800 r / min. The drying temperature in the oven is 50 - 70 °C.

[0020] Preferably, in step S3, the hot - pressing parameters are set as the temperature of 60 - 100 °C, the pressure of 6 - 10 MPa, and the hot - pressing time of 2 - 4 hours.

[0021] Preferably, in step S4, the sputtered metal is gold, the sputtering duration is 8 - 12 s, and it is sputtered 15 - 25 times on both sides respectively. The polarization electric field is set as 15 - 25 kV / mm.

[0022] Preferably, in step S5, the thickness of the polymer film is 80 - 120 microns, and the pre - stretching is set as 2 - 5% of the deformation amount. The material of the polymer tape is PU.

[0023] The second object of the present invention is a highly sensitive flexible piezoelectric sensor, which is prepared according to the preparation method of the highly sensitive flexible piezoelectric sensor, and specifically includes an upper polymer encapsulation layer, an electrode layer, a piezoelectric material layer, an electrode layer and a lower polymer encapsulation layer laid successively from top to bottom.

[0024] Beneficial effects

[0025] The present invention provides a highly sensitive flexible piezoelectric sensor and its preparation method. Through the optimization of the material system and process, it solves the deficiency of traditional piezoelectric sensors in sensitivity, and significantly improves the interfacial performance of piezoelectric composites and the sensitivity of flexible sensors. Adopting two - stage gradient standing, by regulating the difference between the solvent evaporation rate and the particle sedimentation speed through temperature, the controllable phase separation of piezoelectric particles - organic phase is realized; using the new modifier KBM - 503 for surface modification, significantly improving the interfacial bonding ability, and enhancing the particle - matrix interfacial bonding ability by hot - pressing multiple times in the elastoviscous state, realizing a significant improvement in the sensitivity, stability and flexibility of the sensor; introducing a packaging structure of pre - stretched polymer tape + medical tape fixation, offsetting the dynamic stress during the operation of the sensor through pre - stretching, and combining with the polymer film encapsulation layer, realizing the directional transfer of strain energy and reducing the baseline signal drift rate. Description of the Drawings

[0026] Figure 1 It is a schematic diagram of the structure of a flexible piezoelectric sensor

[0027] Figure 2 It is an effect diagram of the high flexibility of the flexible piezoelectric sensor,

[0028] Figure 3 It is a schematic diagram of the actual test fitting method,

[0029] Figure 4 It is the output waveform diagram of the superior ulnar collateral artery Specific Embodiments

[0030] The technical solutions of the present invention will be further described below with reference to the drawings and embodiments

[0031] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the field to which the present invention belongs

[0032] Embodiment 1

[0033] A highly sensitive flexible piezoelectric sensor, the preparation method includes the following steps

[0034] S1. Particle pretreatment: Mix lead zirconate titanate (PZT), polyvinyl chloride (PVC) and tetrahydrofuran (THF) in a ratio of 1:4:15, disperse evenly with an ultrasonic power of 20%, heat the mixed solution to 60°C and stir (rotation speed 1000 r / min), then let it stand at 60°C for 48 h, let it stand at 30°C for 48 h, centrifuge at 4000 r / min for 20 min, add acetone, absolute ethanol and deionized water respectively, and then ultrasonically disperse and dry them in sequence

[0035] S2. Particle surface modification: Mix the piezoelectric particles obtained in step S1, silane coupling agent KBM-503 and acetone in a certain ratio, disperse the mixed solution with an ultrasonic disperser, the dispersion time is 10 min, take out the mixed solution and let it stand for 120 s after completion; continue to disperse for 10 min., place it on a magnetic turntable for heating (60°C) and rotary mixing, and dry it at 60°C for standby

[0036] S3. Hot pressing and curing: Prepare a composite piezoelectric film from the particles modified in step S2 by the doctor blade method, hot press at 80°C and 8 Mpa for 3 hours to obtain a piezoelectric film

[0037] S4. Gold plating and polarization: Sputter gold electrodes on the composite film prepared in step S3, the sputtering duration is 10 s, the number of sputtering times on both sides is 20 times respectively, and apply an electric field of 20 kV / mm for polarization on both sides of the electrode

[0038] S5. Pre-stretched encapsulated sensor: A polymer film with a thickness of 100 microns is laid on the surface of the sensor prepared in S4 for encapsulation, and it is fixed on the polymer tape with medical tape and pre-stretched to obtain a flexible piezoelectric film sensor;

[0039] Figure 1 The flexible piezoelectric film sensor prepared by this improved method is as Figure 1 shown. The flexible piezoelectric film sensor prepared by the above method specifically includes an upper polymer encapsulation layer, an electrode layer, a piezoelectric material layer, an electrode layer, and a lower polymer encapsulation layer laid successively from top to bottom.

[0040] Figure 2 For the flexibility test of the sensor made by this improved method, it is not damaged under large deformations and has high flexibility.

[0041] In this embodiment, the obtained flexible piezoelectric film sensor is tested and applied.

[0042] Figure 3 For the test diagram, the sensor is fixed on the polymer PU tape with medical tape to keep it flat and adhered. The sensor is pre-stretched by about 4% to give it a pre-tightening force, and it is fixed outside the supraorbital artery on the upper side of the superciliary arch, which is the test site. The output waveform diagram of the supraorbital artery pulse as shown in Figure 4 is obtained. The characteristic peaks of the pulse wave can be easily and directly judged. The flexible piezoelectric film sensor prepared by this method has high sensitivity, high resolution, fast response time, high flexibility, and stable electrical properties.

[0043] In addition, the present invention also solves the problem of insufficient softness of traditional piezoelectric film sensors, and the preparation process is simple and can be industrialized.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A preparation method of a highly sensitive flexible piezoelectric sensor, characterized in that: It includes the following steps: S1. Particle pretreatment: Mix piezoelectric particles, organic particles and organic solvents in a certain proportion, ultrasonically disperse them evenly, heat and stir the mixed solution, adopt two-stage gradient standing, control the difference between the solvent evaporation rate and the particle sedimentation rate through temperature, realize the controllable phase separation of the piezoelectric particle-organic phase, conduct centrifugal treatment, add organic solvents, anhydrous ethanol and deionized water respectively, and then ultrasonically disperse them in turn to thoroughly remove impurities, and dry for later use; S2. Particle surface modification: Mix the piezoelectric particles, modifier and organic solvent obtained in step S1 in proportion, ultrasonically disperse them evenly, place them on a magnetic turntable for heating and rotary mixing, and dry for later use; S3. Hot pressing and curing: Prepare a composite piezoelectric thin film from the particles modified in step S2 by the doctor blade method. When the matrix material reaches the viscoelastic state temperature, conduct multi-stage hot pressing to optimize the interfacial bonding strength between the particles and the matrix to obtain a piezoelectric thin film; S4. Gold sputtering and polarization: Sputter metal electrodes on the composite thin film prepared in step S3, and apply pressure polarization on both sides of the electrodes; S5. Pre-stretching and encapsulating the sensor: Lay a layer of polymer film on the surface of the sensor prepared in S4 for encapsulation, fix it on the polymer tape with medical tape and pre-stretch it to obtain a flexible piezoelectric thin film sensor.

2. The preparation method of a highly sensitive flexible piezoelectric sensor according to claim 1, characterized in that: In step S1, the piezoelectric particles are lead zirconate titanate (PZT), with an average particle size of 1-5 μm, the organic particles are polyvinyl chloride (PVC), and the organic solvent is tetrahydrofuran (THF). The mass ratio of the piezoelectric particles, organic particles and organic solvent is 1:4:

15.

3. The preparation method of a highly sensitive flexible piezoelectric sensor according to claim 1, characterized in that: In step S1, the heating and stirring conditions are 50-70 °C and the rotation speed is 800-1200 r / min. The segmented standing is that the first stage stands at 50-70 °C for 48 h, and the second stage stands at 20-40 °C for 48 h.

4. The preparation method of a highly sensitive flexible piezoelectric sensor according to claim 1, characterized in that: In step S2, the power of the ultrasonic dispersion is 10-30%, which is divided into two stages: the first stage is 5-15 min, take it out and stand for 100-150 s; the second stage is 5-15 min.

5. The preparation method of a highly sensitive flexible piezoelectric sensor according to claim 1, characterized in that: In step S2, the modifier is silane coupling agent KBM-503, and the organic solvent is acetone. The mass ratio of the piezoelectric particles, modifier and organic solvent is 1:0.075:

3.

6. The preparation method of a highly sensitive flexible piezoelectric sensor according to claim 1, characterized in that: In step S3, the hot pressing parameters are set as the temperature is 60-100 °C, the pressure is 6-10 MPa, and the hot pressing time is 2-4 hours.

7. The preparation method of a highly sensitive flexible piezoelectric sensor according to claim 1, characterized in that: In step S4, the sputtered metal is gold, the sputtering duration is 8-12 s, and it is sputtered 15-25 times on both sides respectively. The polarization electric field is set to 15-25 kV / mm.

8. The preparation method of a highly sensitive flexible piezoelectric sensor according to claim 1, characterized in that: In step S5, the thickness of the polymer film is 80-120 microns, and the pre-stretching is set to 2-5% of the deformation amount. The material of the polymer tape is PU.

9. A highly sensitive flexible piezoelectric sensor, characterized in that: Prepared by the preparation method described in any one of claims 1-9, including an upper polymer encapsulation layer, an electrode layer, a piezoelectric material layer, an electrode layer and a lower polymer encapsulation layer laid successively from top to bottom.

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