CN113155328B - A flexible passive pressure sensor, preparation method, wearable tactile sensor - Google Patents

Abstract

The invention belongs to the technical field of novel flexible sensors, and discloses a flexible passive pressure sensor, a preparation method and a wearable touch sensor, wherein PVDF powder is added into a beaker containing dimethylformamide solutionStirring to form pasty slurry; baTiO of core-shell structure ₃ Adding the @ ZnO material into a beaker containing dimethylformamide solution, and performing ultrasonic dispersion; adding the white solution into the PVDF transparent pasty slurry, continuously stirring to form uniform white pasty slurry, and placing the slurry into a vacuum drying oven for maintenance; pouring the slurry into a manufactured mold, uniformly dispersing the slurry in the mold by using a scraper, placing the mold in a vacuum drying oven for holding, drying the slurry to form a piezoelectric film, and drying; the aluminum foil electrodes are attached to the upper surface and the lower surface of the piezoelectric film, the golden finger PI packaging device is used, the direct-current high-voltage power supply is connected with the upper electrode and the lower electrode, and the flexible piezoelectric force sensor is obtained through polarization. The invention has higher electrical performance output and sensitivity.

Description

A flexible passive pressure sensor, preparation method, wearable tactile sensor

technical field

The invention belongs to the technical field of novel flexible sensors, and in particular relates to a flexible passive pressure sensor, a preparation method, and a wearable tactile sensor.

Background technique

In recent years, due to changes in living habits and dietary structure, various chronic health diseases have gradually emerged among young and middle-aged people, and the incidence rate is showing a rising trend. Going to the hospital for health checks has caused a large number of medical equipment to be occupied, and it has also brought a lot of inconvenience and troubles to people's daily life. Flexible wearable electronic devices are favored by people because of their small size, light weight, easy to carry, comfortable to wear, real-time monitoring, health and environmental protection, etc., showing unparalleled charm in the field of next-generation medical health monitoring. However, the existence of the battery increases the size and weight of the portable device, and the regular replacement and maintenance of the battery also causes a lot of inconvenience. Therefore, it is of great significance to develop a self-powered flexible wearable sensor. Among the many types of pressure sensors, the flexible piezoelectric pressure sensor developed according to the piezoelectric effect is one of the most widely studied passive flexible pressure sensors due to its simple structure, low cost, and high sensitivity.

Polyvinylidene fluoride (PVDF) is a thermoplastic semi-crystalline polymer composed of a large number of repeating units [CH ₂ -CF ₂ ], which has ultra-high flexibility, sufficient mechanical strength, stable chemical resistance and excellent piezoelectricity, and is widely used in the fields of wearable electronic devices and energy harvesting devices. PVDF has five different crystal phases of α, β, δ, γ, and ε, among which the crystalline β phase has a high piezoelectric coefficient. Although PVDF polymer has good flexibility and durability, its dielectric constant and piezoelectric coefficient d ₃₃ , which are far lower than inorganic piezoelectric materials, are still a huge regret in its application. To solve this problem, the researchers developed two approaches: adding functional nanomaterials to the PVDF matrix to break the symmetrical structure of polyvinylidene fluoride and promote the formation of the polar crystalline β phase; adding basic nanomaterials with piezoelectric properties to the PVDF matrix to improve the overall piezoelectric response. Among them, zinc oxide is a wurtzite piezoelectric material and also a functional material that promotes the formation of the piezoelectric phase of PVDF. Lead-free BTO is considered to be the most environmentally friendly perovskite material and provides high-voltage performance and high dielectric constant.

At present, there have been many reports on pressure sensors based on ZnO or BaTiO ₃ , but there are few reports on flexible self-powered pressure sensors based on BaTiO ₃ @ZnO. The ZnO on the surface of the BaTiO ₃ @ZnO piezoelectric material strengthens the connection between the nanoparticles and the polymer, and increases the content of the piezoelectric phase β phase in PVDF. In terms of performance, BaTiO ₃ and ZnO can provide higher piezoelectric coefficient and dielectric constant, improve the voltage output performance, and the uniform dispersion of nanoparticles improves the sensitivity of the device. Therefore, the research on the flexible passive pressure sensor prepared by BaTiO ₃ @ZnO has far-reaching significance.

Through the above analysis, the existing problems and defects of the prior art are: there are few reports on flexible self-powered pressure sensors based on BaTiO ₃ @ZnO. _BaTiO nanoparticles are prone to agglomeration, resulting in poor dispersion in the PVDF matrix, and interface hole defects and cracks between the two components limit the performance of the flexible pressure sensor. For this reason, many researchers add functional materials (such as carbon nanotubes, graphene, cellulose, etc.) to it to solve these problems. Unfortunately, the added functional material does not have piezoelectric properties; the functional material and BaTiO ₃ nanoparticles are not composited together, and the dispersion problem is not completely solved.

The difficulty of solving the above problems and defects is: the present invention hopes to coat the wurtzite piezoelectric material ZnO nanoparticles on the surface of BaTiO ₃ to improve the overall piezoelectric performance of the sensor while completely solving the dispersion problem of BaTiO ₃ . However, _BaTiO3 is a stable perovskite ceramic material, and it is difficult to grow and attach other materials on its smooth surface. To this end, the present invention uses a sol-gel method to adhere the generated Zn(OH) ₂ to the surface of BaTiO ₃ through the complexation reaction of the polymer, and synthesize ZnO nanoparticles attached to the surface of BaTiO ₃ after high-temperature calcination.

The significance of solving the above problems and defects is: through this method, the present invention solves the dispersion problem of _BaTiO3 in the PVDF matrix without introducing other non-piezoelectric materials, and the introduction of the wurtzite ZnO self-polarized piezoelectric material improves the overall output performance and long-term stability of the device, and provides a new solution for subsequent related research.

Contents of the invention

Aiming at the problems existing in the prior art, the invention provides a flexible passive pressure sensor, a preparation method, and a wearable tactile sensor.

The present invention is achieved like this, a kind of preparation method of flexible passive pressure sensor, the preparation method of described flexible passive pressure sensor comprises:

Add PVDF powder into a beaker containing dimethylformamide solution, place the beaker in a water bath and stir to form a uniform and transparent paste-like slurry, which provides a supporting framework for the next incorporation of high-performance piezoelectric material BaTiO ₃ @ZnO;

Add the core-shell structure BaTiO ₃ @ZnO material into a beaker containing dimethylformamide solution, and ultrasonically disperse, so that BaTiO _{3 @ZnO is evenly dispersed in the solution, avoiding BaTiO 3 @ZnO} powder directly added to PVDF slurry to cause uneven dispersion of BaTiO ₃ @ZnO, and improving the long-term stability of the device;

Add the resulting white solution into the PVDF transparent paste slurry, continue to stir to form a uniform white paste slurry, place the slurry in a vacuum drying oven to keep the air bubbles in the slurry out, and avoid microscopic holes in the piezoelectric film due to the existence of air bubbles, resulting in subsequent high-voltage polarization failures;

Pour the slurry into the prepared mold, use a scraper to disperse the slurry evenly in the mold, place the mold in a vacuum oven to keep, dry the slurry at low temperature to form a piezoelectric film, and calcine at a high temperature to promote the formation of more electroactive phases in the PVDF in the piezoelectric film;

Aluminum foil electrodes were attached to the upper and lower surfaces of the piezoelectric film, and gold finger PI was used to package the device, which avoided the influence of the device test performance by the environment; the DC high-voltage power supply was connected to the upper and lower electrodes and polarized to make the direction of the BaTiO ₃ electric dipole moment consistent, which enhanced the piezoelectric output capability; a flexible piezoelectric pressure sensor based on BaTiO ₃ @ZnO was obtained.

Further, add 1-2g of PVDF powder purchased from Aladdin into a beaker containing 7-10ml of dimethylformamide solution, place the beaker in a water bath at 50-70°C and stir for 1-3 hours to promote the dissolution of PVDF to form a uniform and transparent paste-like slurry.

Further, add 0.05-0.15g of BaTiO ₃ @ZnO material with core-shell structure into a beaker containing 3-5ml of dimethylformamide solution, add a small amount of BaTiO ₃ @ZnO to improve the piezoelectric properties while maintaining the flexibility of the piezoelectric sensor, and disperse it evenly by ultrasonication for 30-60 minutes.

Further, add the obtained white solution into the PVDF transparent paste slurry, continue stirring at 50-70°C for 1-3 hours, BaTiO ₃ @ZnO is completely dispersed in the PVDF slurry to form a uniform white paste-like slurry, and place the slurry in a vacuum drying oven for 30-90 minutes to extract the air bubbles in the slurry.

Further, pour the slurry into the prepared mold, use a scraper to disperse the slurry evenly in the mold, place the mold in a vacuum oven at 60-80°C for 1-3 hours, dry the slurry to form a piezoelectric film, and dry at 90-120°C for 1-3 hours.

Furthermore, the aluminum foil electrodes were attached to the upper and lower surfaces of the piezoelectric film, the device was packaged with gold finger PI, the upper and lower electrodes were connected to a DC high-voltage power supply, and polarized at 90-120°C for 1-1.5h to obtain a flexible piezoelectric pressure sensor based on BaTiO ₃ @ZnO.

Further, the piezoelectric film is obtained by mixing BaTiO ₃ @ZnO material with core-shell structure and PVDF solution, including:

(1) Dissolve 5-7g NaOH in 20-40ml deionized water, stir at room temperature for 10-20min to completely dissolve NaOH in deionized water, and provide an alkaline solution environment for the preparation of BaTiO ₃ particles; add 0.6-0.8g Ba(Ac) ₂ and 0.2-0.3g TiO ₂ into the NaOH solution to provide Ba and Ti sources for the preparation of BaTiO ₃ particles, and continue stirring at room temperature for 30-60 minutes to disperse the solution evenly , to ensure that the subsequent hydrothermal reaction is sufficient and the size of the target product is uniform;

(2) Transfer the obtained white mixed solution to an autoclave, and heat it in an oven at 200° C. for 24 hours to generate the target product BaTiO ₃ ;

(3) Centrifuge the obtained precipitate, wash the obtained product with deionization and ethanol respectively, and then centrifuge for 5 to 7 times; dry the product at 60 to 80°C, and roast the obtained powder at 900 to 1100°C for 1 to 3 hours, so that _BaTiO3 forms a tetragonal phase structure. That is, the BaTiO ₃ material of 140-160nm is obtained;

(4) Dissolve 1-2g of PEG and 0.3-0.4g of Zn(Ac) ₂ in 30-40ml of deionized water, wherein Zn(Ac) ₂ is used as the source of Zn for the synthesis of ZnO, and PEG will adhere the generated Zn(OH) ₂ to the surface of _BaTiO3 ; stir at room temperature for 10-30min to dissolve completely;

(5) Add the obtained product into the mixed solution obtained in (4), continue stirring at room temperature for 30-60 minutes to disperse the material evenly in the mixed solution, add 2-4ml NH ₃ ·H ₂ O and stir for 1-3 hours;

(6) Centrifuge the obtained precipitate, wash the obtained product with deionized water and ethanol, and centrifuge for 5 to 7 times; dry the product at 60 to 80° C., and roast the obtained powder at 500 to 600° C. for 1 to 3 hours, and Zn (OH) ₂ is converted into ZnO nanoparticles. That is, the BaTiO ₃ @ZnO piezoelectric material is obtained.

Another object of the present invention is to provide a flexible passive pressure sensor prepared by the preparation method of the flexible passive pressure sensor. The flexible passive pressure sensor is composed of a flexible piezoelectric film made of BaTiO ₃ @ZnO piezoelectric material and PVDF, an aluminum foil electrode attached to the upper and lower surfaces of the flexible piezoelectric film, and a PI packaging material attached to the surface of the aluminum foil electrode.

Another object of the present invention is to provide a wearable tactile sensor comprising the flexible passive pressure sensor.

Another object of the present invention is to provide a medical health monitoring terminal, which communicates wirelessly with the wearable tactile sensor.

Combining all the above-mentioned technical solutions, the advantages and positive effects of the present invention are: the BaTiO ₃ @ZnO piezoelectric material prepared by the sol-gel method in the present invention has a simple synthesis method and low cost; the prepared material has high piezoelectric properties, good material crystallinity, and uniform particle distribution; the prepared flexible pressure sensor has excellent mechanical strength and flexibility, and can work at different frequencies; the prepared flexible pressure sensor has high electrical performance output and sensitivity, and has broad application prospects in wearable flexible self-powered sensors.

The invention uses a sandwich structure to package the combined device, which has simple technology and small volume, and _is suitable for mass production. BaTiO ₃ @ZnO is used as the piezoelectric material. On the one hand, the hydroxyl groups and metal ions on the surface of ZnO are combined with PVDF to make the inorganic nanoparticles and organic polymers closely connected; performance and energy harvesting. At the same time, the piezoelectric sensor with a sandwich structure adopted in the present invention has a simple manufacturing process, good flexibility, and is conducive to industrial mass production, so it has important application value.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the accompanying drawings that need to be used in the embodiments of the present application will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other accompanying drawings can also be obtained according to these drawings without paying creative work.

Fig. 1 is a flowchart of a method for preparing a flexible passive pressure sensor provided by an embodiment of the present invention.

Fig. 2 is a SEM surface topography diagram of the hydrothermally synthesized perovskite material BaTiO ₃ provided by the embodiment of the present invention.

Fig. 3 is a SEM surface topography diagram of (a) pure PVDF film and (b) BaTiO ₃ @ZnO/PVDF film provided by the embodiment of the present invention.

Fig. 4 is a Fourier transform infrared spectrum diagram of the piezoelectric composite thin film provided by the embodiment of the present invention.

Fig. 5 is a schematic structural diagram of a flexible pressure sensor provided by an embodiment of the present invention.

Fig. 6 is the voltage and current output diagram of the flexible pressure sensor prepared by the pure PVDF film provided by the embodiment of the present invention.

Fig. 7 is a voltage and current output diagram of a flexible pressure sensor prepared from a BaTiO ₃ @ZnO/PVDF film provided by an embodiment of the present invention.

Fig. 8 is a comparison chart of the electrical performance output of the BZ-2 sensor under different pressures in the embodiment provided by the embodiment of the present invention.

Fig. 9 is a comparison diagram of the electrical performance output of the BZ-2 sensor at different frequencies in the embodiment provided by the embodiment of the present invention.

Fig. 10 is the voltage fatigue output diagram of the BZ-2 flexible pressure sensor in the embodiment provided by the embodiment of the present invention.

Fig. 11 is a voltage output diagram of the flexible pressure sensor in the embodiment provided by the embodiment of the present invention in 2000 pressure cycles.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Aiming at the problems existing in the prior art, the present invention provides a flexible passive pressure sensor, a preparation method, and a wearable tactile sensor. The present invention will be described in detail below in conjunction with the accompanying drawings.

As shown in Figure 1, the preparation method of the flexible passive pressure sensor provided by the present invention comprises the following steps:

S101: Add 1-2g of PVDF powder purchased from Aladdin into a beaker containing 7-10ml of dimethylformamide solution, place the beaker in a water bath at 50-70°C and stir for 1-3 hours to form a uniform and transparent paste-like slurry;

S102: Add 0.05-0.15 g of core-shell structure BaTiO ₃ @ZnO material into a beaker containing 3-5 ml of dimethylformamide solution, and disperse it evenly by ultrasonication for 30-60 min;

S103: Add the obtained white solution into the PVDF transparent paste slurry, continue stirring at 50-70°C for 1-3 hours to form a uniform white paste-like slurry, and then place the slurry in a vacuum drying oven for 30-60 minutes to extract the air bubbles in the slurry;

S104: Slowly pour the slurry into the prepared mold, use a scraper to disperse the slurry evenly in the mold, place the mold in a vacuum oven at 60-80°C for 1-3 hours, dry the slurry to form a piezoelectric film, and dry at 90-120°C for 1-3 hours;

S105: Aluminum foil electrodes are attached to the upper and lower surfaces of the piezoelectric film, the device is packaged with gold finger PI, the upper and lower electrodes are connected to a DC high-voltage power supply, and polarized at 90-120°C for 1-1.5h to obtain a flexible piezoelectric pressure sensor based on BaTiO ₃ @ZnO.

The preparation method of the flexible passive pressure sensor provided by the present invention can also be implemented by those skilled in the art by other steps, and the preparation method of the flexible passive pressure sensor provided by the present invention in Fig. 1 is only a specific embodiment.

The piezoelectric pressure tactile sensor based on the BaTiO ₃ @ZnO material of the present invention is composed of a flexible piezoelectric film made of BaTiO ₃ @ZnO piezoelectric material and PVDF, an adhesive aluminum foil electrode attached to the upper and lower surfaces of the flexible film, electrode lead wires, and a PI packaging material that isolates static electricity and the influence of the air environment; it is characterized in that: the piezoelectric film is obtained by mixing BaTiO ₃ @ZnO material with a core-shell structure and PVDF solution, and the material is prepared by the following steps:

(1) First, dissolve 5-7g NaOH in 20-40ml deionized water to prepare a strong alkaline solution environment, and stir at room temperature for 10-20min to completely dissolve NaOH in deionized water. Add 0.6-0.8g Ba(Ac) ₂ and 0.2-0.3g TiO ₂ to the NaOH solution, and continue stirring at room temperature for 30-60min to disperse the solution evenly;

(2) Transfer the obtained white mixed solution to an autoclave, and heat it in an oven at 200° C. for 24 hours to generate the target product BaTiO ₃ ;

(3) Centrifuge the obtained precipitate, wash the obtained product with deionization and ethanol respectively, and centrifuge for 5 to 7 times; dry the product at 60 to 80°C, and roast the obtained powder at 900 to 1100°C for 1 to 3 hours. That is, the BaTiO ₃ material of 150-200nm is obtained;

(4) Dissolve 1-2g PEG, 0.3-0.4g Zn(Ac) ₂ in 30-40ml deionized water, stir at room temperature for 10-30min to completely dissolve;

(5) Add the obtained product into the mixed solution obtained in step ④, continue stirring at room temperature for 30-60 minutes to disperse the material evenly in the mixed solution, add 2-4ml NH ₃ ·H ₂ O and stir for 1-3 hours;

(6) Centrifuge the obtained precipitate, wash the obtained product with deionized water and ethanol, and then centrifuge for 5 to 7 times. The product is dried at 60-80°C, and the obtained powder is calcined at 500-600°C for 1-3 hours. That is, the BaTiO ₃ @ZnO piezoelectric material is obtained.

The technical scheme of the present invention will be further described below in conjunction with the accompanying drawings.

As shown in Figure 2, it can be seen that the BaTiO ₃ piezoelectric material particles are uniform, the particle size range is 150-200nm, and the shape is square.

As shown in Figure 3, it can be seen that the surface of BaTiO ₃ is uniformly covered with ZnO nanoparticles, and the particles are uniform.

As shown in Figure 4, (a) and (b) in the figure are pure PVDF film and composite film doped with piezoelectric material respectively. The surface of the film is uniform, and the piezoelectric material is uniformly dispersed in the composite film.

As shown in Figure 5, the figure shows the diffraction peak intensities of the piezoelectric phase β, γ phase and the non-piezoelectric phase α phase in the flexible piezoelectric composite film.

As shown in Figure 6, the sandwich structure of the flexible piezoelectric sensor, piezoelectric composite film, surface electrodes, and device packaging materials are shown in (a), and the physical map of the flexible BaTiO ₃ @ZnO/PVDF piezoelectric sensor device is shown in (b).

As shown in Figure 7, the pure PVDF film can output a peak-to-peak voltage of 8V and a maximum short-circuit current of 200nA after polarization.

As shown in Figure 8, the maximum output peak-to-peak voltage of the BaTiO ₃ @ZnO/PVDF composite film with different zinc oxide content on the surface is 26V. Too much zinc oxide may cause a short circuit of the internal current of the composite film, resulting in a decrease in the output voltage.

As shown in Figure 9, the output voltage of the flexible sensor gradually increases with the gradual increase of the pressure.

As shown in Figure 10, the output voltage of the flexible pressure sensor gradually increases with the increase of the applied pressure frequency.

As shown in Figure 11, the output voltage of the flexible pressure sensor is stable during 2000 pressure cycles without significant decrease, and the performance of the device is stable.

The technical solutions of the present invention will be further described below in conjunction with specific embodiments.

Comparative example 1:

A flexible pressure sensor is prepared from a piezoelectric composite film made of pure PVDF. The specific manufacturing process is as follows:

1. Add 1-2g of PVDF powder purchased from Aladdin into a beaker containing 10-15ml of dimethylformamide solution, place the beaker in a water bath at 50-70°C and stir for 2-4 hours to form a uniform and transparent paste slurry.

2. Put the PVDF transparent paste slurry in a vacuum drying oven for 30-60 minutes to extract the air bubbles in the slurry.

3. Slowly pour the slurry into the prepared mold, use a scraper to disperse the slurry evenly in the mold, place the mold in a vacuum drying oven at 60-80°C for 1-3 hours, dry the slurry to form a piezoelectric film, and dry at 90-120°C for 1-3 hours.

4. Attach the aluminum foil electrodes to the upper and lower surfaces of the piezoelectric film, use gold finger PI to package the device, connect the upper and lower electrodes with a DC high-voltage power supply, and polarize at 90-120°C for 1-1.5 hours, thus obtaining a flexible piezoelectric pressure sensor based on BaTiO ₃ @ZnO.

Example 1:

1. First, dissolve 5-7g NaOH in 20-40ml deionized water to prepare a strong alkaline solution environment, stir at room temperature for 10-20min to completely dissolve NaOH in deionized water. Add 0.6-0.8g Ba(Ac) ₂ and 0.2-0.3g TiO ₂ to the NaOH solution, and continue stirring at room temperature for 30-60min to disperse the solution evenly.

2. The mixed solution was transferred to an autoclave, and heated in an oven at 200° C. for 24 hours to generate the target product BaTiO ₃ .

3. Centrifuge the obtained precipitate, wash the obtained product with deionization and ethanol respectively, and centrifuge for 5-7 times; dry the product at 60-80° C., and roast the obtained powder at 900-1100° C. for 1-3 hours. That is, a BaTiO ₃ material of 150-200 nm is obtained.

4. Dissolve 1-2g of PEG and 0.382g (0.19g, 0.57g, 0.76g) of Zn(Ac) ₂ in 30-40ml of deionized water, and stir at room temperature for 10-30min to dissolve completely.

5. Add the product obtained in step 3 to the mixed solution obtained in step 4, continue stirring at room temperature for 30-60 minutes to disperse the material evenly in the mixed solution, add 2-4ml NH ₃ ·H ₂ O and stir for 1-3 hours.

6. Centrifuge the obtained precipitate, wash the obtained product with deionized water and ethanol, and then centrifuge for 5 to 7 times. The product is dried at 60-80°C, and the obtained powder is calcined at 500-600°C for 1-3 hours. That is to obtain the BaTiO ₃ @ZnO piezoelectric material, denoted as BZ-2 (BZ-1, BZ-3, BZ-4).

7. Add 1-2g of PVDF powder purchased from Aladdin into a beaker containing 7-10ml of dimethylformamide solution, place the beaker in a water bath at 50-70°C and stir for 1-3 hours to form a uniform and transparent paste slurry.

8. Add 0.05-0.15 g of core-shell structure BaTiO ₃ @ZnO material into a beaker containing 3-5 ml of dimethylformamide solution, and disperse it evenly by ultrasonication for 30-60 min.

9. Add the white solution obtained in step ② into the PVDF transparent paste slurry, and continue stirring at 50-70°C for 1-3 hours to form a uniform white paste-like slurry, and then place the slurry in a vacuum drying oven for 30-60 minutes to extract the air bubbles in the slurry.

10. Slowly pour the slurry into the prepared mold, use a scraper to disperse the slurry evenly in the mold, place the mold in a vacuum oven at 60-80°C for 1-3 hours, dry the slurry to form a piezoelectric film, and dry at 90-120°C for 1-3 hours.

11. Attach the aluminum foil electrodes to the upper and lower surfaces of the piezoelectric film, use gold finger PI to package the device, connect the upper and lower electrodes with a DC high-voltage power supply, and polarize at 90-120°C for 1-1.5 hours, thus obtaining a flexible piezoelectric pressure sensor based on BaTiO ₃ @ZnO.

In the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more; the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, in a specific orientation construction and operation, therefore, should not be construed as limiting the invention. In addition, the terms "first", "second", "third", etc. are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

It should be noted that the embodiments of the present invention can be realized by hardware, software, or a combination of software and hardware. The hardware part can be implemented using dedicated logic; the software part can be stored in memory and executed by a suitable instruction execution system such as a microprocessor or specially designed hardware. Those of ordinary skill in the art will appreciate that the above-described devices and methods may be implemented using computer-executable instructions and/or embodied in processor control code provided, for example, on a carrier medium such as a magnetic disk, CD or DVD-ROM, a programmable memory such as a read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. The device and its modules of the present invention can be realized by hardware circuits such as very large scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, etc., or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., can also be realized by software executed by various types of processors, or can be realized by a combination of the above hardware circuits and software, such as firmware.

The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any modification, equivalent replacement and improvement made within the spirit and principles of the present invention by any person familiar with the technical field within the technical scope disclosed in the present invention shall be covered within the protection scope of the present invention.

Claims (7)

1. The preparation method of the flexible passive pressure sensor is characterized by comprising the following steps of:

adding PVDF powder into a beaker containing dimethylformamide solution, and placing the beaker into a water bath kettle to be stirred to form uniform and transparent pasty slurry;

BaTiO of core-shell structure ₃ Adding the @ ZnO material into a beaker containing dimethylformamide solution, and performing ultrasonic dispersion;

adding the obtained white solution into PVDF transparent pasty slurry, continuously stirring to form uniform white pasty slurry, and placing the slurry in a vacuum drying oven for maintaining to extract bubbles in the slurry;

pouring the slurry into a manufactured mold, uniformly dispersing the slurry in the mold by using a scraper, placing the mold in a vacuum drying oven for holding, drying the slurry to form a piezoelectric film, and drying;

aluminum foil electrodes are attached to the upper surface and the lower surface of the piezoelectric film, a PI packaging device is used, a direct-current high-voltage power supply is connected with the upper electrode and the lower electrode, and polarization is carried out to obtain a piezoelectric film based on BaTiO ₃ Flexible piezoelectric pressure sensor made of @ ZnO;

adding 1-2 g of PVDF powder into a beaker containing 7-10 ml of dimethylformamide solution, and placing the beaker into a water bath kettle at 50-70 ℃ to be stirred for 1-3 hours to form uniform and transparent pasty slurry;

0.05-0.2 g of BaTiO with core-shell structure ₃ Adding the @ ZnO material into a beaker containing 3-5 ml of dimethylformamide solution, and carrying out ultrasonic treatment for 30-60 min to uniformly disperse the @ ZnO material;

wherein the piezoelectric film is made of BaTiO with a core-shell structure ₃ @ZnOThe PVDF material is obtained by mixing the PVDF material with a PVDF solution, and specifically comprises the following components:

(1) Dissolving 5-7 g of NaOH in 20-40 ml of deionized water to prepare a strong alkaline solution environment, stirring at room temperature for 10-20 min, and completely dissolving the NaOH in the deionized water; adding 0.6 to 0.8g of Ba (Ac) into the NaOH solution ₂ 、0.2~0.3gTiO ₂ Continuously stirring for 30-60 min at room temperature to uniformly disperse the solution;

(2) Transferring the obtained white mixed solution into an autoclave, and carrying out hydrothermal treatment in an oven at 200 ℃ for 24 hours to generate a target product BaTiO ₃ ；

(3) Centrifuging the obtained precipitate, washing the obtained product with deionized water and ethanol respectively, and centrifuging for 5-7 times; drying the product at 60-80 ℃, roasting the obtained powder at 900-1100 ℃ for 1-3 hours to obtain 150-200nm BaTiO ₃ A material;

(4) 1 to 2g of PEG, 0.3 to 0.4g of Zn (Ac) ₂ Dissolving in 30-50 ml deionized water, and stirring at room temperature for 10-30 min to completely dissolve;

(5) Adding the obtained product into the mixed solution obtained in the step (4), continuously stirring for 30min at room temperature to uniformly disperse the material in the mixed solution, and adding 2-4 ml of NH ₃ ^. H ₂ O stirring for 1-3 h;

(6) Centrifuging the obtained precipitate, washing the obtained product with deionized water and ethanol, and centrifuging for 5-7 times; drying the product at 60-80 ℃, and roasting the obtained powder at 500-600 ℃ for 1-3 hours to obtain BaTiO ₃ @ ZnO piezoelectric material.

2. The method for manufacturing the flexible passive pressure sensor according to claim 1, wherein the obtained white solution is added into PVDF transparent pasty slurry, stirring is continued for 1-3 hours at 50-70 ℃ to form uniform white pasty slurry, and the slurry is placed in a vacuum drying oven for 30-60 min to extract bubbles existing in the slurry.

3. The method for manufacturing the flexible passive pressure sensor according to claim 1, wherein slurry is poured into a manufactured mold, the slurry is uniformly dispersed in the mold by using a scraper, the mold is placed in a vacuum drying oven at 60-80 ℃ for 1-3 hours, the slurry is dried to form a piezoelectric film, and the piezoelectric film is dried at 90-120 ℃ for 1-3 hours.

4. The method for manufacturing a flexible passive pressure sensor according to claim 1, wherein aluminum foil electrodes are attached to upper and lower surfaces of the piezoelectric film, a PI packaging device is used, a direct current high voltage power supply is connected with the upper and lower electrodes, and polarization is performed for 1 to 1.5 hours at 90 to 120 ℃ to obtain a film based on BaTiO ₃ Flexible piezoelectric pressure sensor made of ZnO.

5. A flexible passive pressure sensor prepared by the method for preparing a flexible passive pressure sensor according to any one of claims 1 to 4, characterized in that the flexible passive pressure sensor is prepared by a method comprising BaTiO ₃ The flexible piezoelectric film is composed of a flexible piezoelectric film made of ZnO piezoelectric material and PVDF, adhesive aluminum foil electrodes attached to the upper surface and the lower surface of the flexible film, and a PI packaging material for isolating static electricity and air environmental influences.

6. A wearable touch sensor comprising the flexible passive pressure sensor of claim 5.

7. A medical health monitoring terminal in wireless communication with the wearable touch sensor of claim 6.