A flexible piezoelectric device with super-high output performance and wireless signal transmission performance and a preparation method thereof

Abstract

The application discloses a flexible piezoelectric device with super-high output performance and wireless signal transmission and a preparation method thereof. ‑2 The flexible piezoelectric device shows excellent energy capturing and collecting capacity under low-frequency mechanical vibration. The output voltage of the flexible device can reach 126V under a frequency of 2Hz, and the corresponding output power density can reach 710mW m ‑2 , which is the optimal output performance among the same type of devices. In addition, the flexible piezoelectric device can sensitively respond to mechanical vibration below 500Hz, showing excellent sensing performance, and the sensing of the vibration signal of a model transformer is successfully realized by using the flexible piezoelectric device. The flexible piezoelectric device is integrated with a wireless signal transmission module, and the wireless transmission of the vibration signal can be realized.

Description

Technical Field

[0001] This invention belongs to the field of sensor fabrication and application, and relates to a flexible piezoelectric device and its fabrication method, particularly to a flexible piezoelectric device with ultra-high output performance and wireless signal transmission function and its fabrication method. Background Technology

[0002] With the advent of the information age, various industries require massive sensor networks, and powering these widely distributed and numerous sensors has become a major challenge. The traditional method uses primary batteries to power the sensors; however, this method is not environmentally friendly, and replacing batteries for a large number of sensors is cumbersome. Therefore, there is a need to develop self-powered sensors that can spontaneously harvest energy from the environment and convert it into electrical energy. The piezoelectric effect refers to the phenomenon that when an external force is applied to the surface of a piezoelectric material, a corresponding surface charge is generated. Through device and circuit design, piezoelectric materials can continuously output charge under external stress, becoming piezoelectric generators, which is an ideal power generation method for self-powered sensors. At the same time, the piezoelectric generator's sensitive electrical signal response to external forces also makes it an ideal vibration sensor.

[0003] The core component of a piezoelectric device is its piezoelectric active material. Limited by the inherent properties of piezoelectric materials, flexible piezoelectric devices currently using piezoelectric polymers as the electroactive material typically have an instantaneous output voltage below 20V, corresponding to an average power density of only 10mW / m². -2 The order of magnitude of the output voltage and the excessively low output performance make it difficult for piezoelectric devices to meet the needs of practical applications as self-powered sensors (ChCC C,LC C,ShaCC C,CC aC.HCCh-CCrCCrmaCcC CCCzCCCCcCrCcCaCCCCCCraCCrp pCCh CmCrCCCCp PpVDF-TrFEpppaTCp3 CaCCcCmCCpCCC mCcrCCCCCarpCCr pCCC-CCpCrCp CCCmCmCCpCrpmCm.SmaCC, 2017, 13p23pm 1604245.). Prior to this invention, no flexible piezoelectric device could achieve an output voltage of over 120V and a power output of 710mW. -2 The output power density is low, and there are no application cases of using flexible piezoelectric sensors for transformer vibration monitoring. Summary of the Invention

[0004] This invention addresses the low output performance of current piezoelectric devices by proposing a flexible piezoelectric device with ultra-high output performance and its fabrication method. This invention is the first to successfully fabricate a piezoelectric device with an output voltage exceeding 120V, and successfully realizes wireless vibration sensing of power equipment using the flexible piezoelectric device. This invention has clear practical value and provides important reference for the design of future piezoelectric energy harvesting devices and piezoelectric vibration sensors.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] This invention provides a flexible piezoelectric device, comprising a core-sheath composite piezoelectric fiber membrane prepared by coaxial electrospinning, electrodes, leads, and device encapsulation material; the electrodes are located on both sides of the core-sheath composite piezoelectric fiber membrane, and the device encapsulation material is disposed on the outer side of the electrodes; the electrodes are provided with leads.

[0007] As one embodiment of the present invention, the sheath polymer of the core-shell composite piezoelectric fiber membrane is PVDF or PVDF-TrFE. The electrospun piezoelectric fiber material applicable to the present invention is a core-shell composite piezoelectric fiber material with polyvinylidene fluoride (PVDF) or polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE) as the matrix.

[0008] As one embodiment of the present invention, the core polymer of the core-shell structure composite piezoelectric fiber membrane is polycarbonate (PC), polymethyl methacrylate (PMMA), or silk fibroin (SF).

[0009] The present invention also provides a method for fabricating a flexible piezoelectric device, the method comprising the following steps:

[0010] S1. Cut the composite piezoelectric fiber membrane with an aluminum foil substrate into shape to obtain a fiber membrane sheet;

[0011] S2. An aluminum foil sheet is attached to the substrate-free side of the fiber membrane as an electrode, and copper wires are placed on the aluminum foil electrodes on both sides of the fiber membrane.

[0012] S3. Two polyethylene terephthalate (PET) films are attached to the outside of the fiber film with aluminum foil electrodes and copper wires prepared in step S2, and then pressed to complete the encapsulation of the device.

[0013] In one embodiment of the present invention, in step S1, the size of the fiber membrane is 2cm*2cm to 2.5cm*2.5cm.

[0014] In one embodiment of the present invention, in step S2, the size of the aluminum foil sheet is 1.8cm*1.8cm to 2.3cm*2.3cm.

[0015] In one embodiment of the present invention, in step S3, the size of the polyethylene terephthalate (PET) film is 3.6cm*2.5cm to 4cm*3cm.

[0016] In one embodiment of the present invention, in step S3, the thickness of the polyethylene terephthalate (PET) film is 150–200 μm.

[0017] In one embodiment of the present invention, the copper conductor is copper tape.

[0018] In one embodiment of the present invention, the compaction is performed by using a press to compact the device under a pressure of 5 to 10 MPa.

[0019] In one embodiment of the present invention, in step S1, the composite piezoelectric fiber film with an aluminum foil substrate is prepared by a method comprising the following steps:

[0020] A1. Dissolve PVDF-TrFE polymer raw material in N,N-dimethylformamide to prepare PVDF-TrFE polymer skin spinning solution; dissolve PC in tetrahydrofuran to prepare PC polymer core spinning solution;

[0021] A2. The PVDF-TrFE polymer skin spinning solution and the PC polymer core spinning solution are coaxially electrospun.

[0022] A3. Collect the electrospun fibers prepared in step A2 using a roller covered with aluminum foil, and obtain an electrospun fiber membrane after peeling off the aluminum foil.

[0023] In one embodiment of the present invention, the mass fraction of PVDF-TrFE in the PVDF-TrFE polymer skin spinning solution is 16% to 24%.

[0024] In one embodiment of the present invention, the mass fraction of PC in the PC polymer core spinning solution is 16% to 24%.

[0025] In one embodiment of the present invention, in step A1, the dissolution is achieved by heating in a water bath to 60°C to 80°C and stirring for 4 to 6 hours to completely dissolve the polymer and form a clear solution.

[0026] In one embodiment of the present invention, in step A2, the parameters of the electrospinning process are set as follows: spinning voltage: 15-22kV; spinning rate: the spinning rate of the PVDF-TrFE skin is 0.5-0.9 mL / h. -1 The spinning rate of the PC core layer is 0.1–0.3 mL / h. -1 .

[0027] As one embodiment of the present invention, the coaxial needles used in the coaxial electrospinning are of the following specifications: 18p14G to 25p18G, with the corresponding inner diameter of the core needle being 0.26 to 0.84 mm and the inner diameter of the shell needle being 0.84 to 1.55 mm.

[0028] In one embodiment of the present invention, in step A3, the distance between the roller collector and the spinning needle is selected to be 15-20 cm, and the rotation speed of the roller collector is maintained at 800-1200 rpm.

[0029] The present invention also provides a wireless vibration signal transmission monitoring system, including a flexible piezoelectric device, a wireless signal transmission module electrically connected to the flexible piezoelectric device, and wireless signal acquisition software.

[0030] The present invention also provides a method for fabricating a wireless vibration signal transmission and monitoring system based on the aforementioned flexible piezoelectric device, which includes the following steps:

[0031] S1. Connect the wireless transmission module and the power module by spot welding.

[0032] S2. The signal input of the wireless transmission module is connected to the output wiring (wire) of the flexible piezoelectric device.

[0033] S3. Use polyimide tape to completely insulate and encapsulate the wireless module, but leave the signal transmission port exposed.

[0034] Existing piezoelectric and triboelectric devices primarily generate electrical signals through vertical pressure. In contrast, the piezoelectric device of this invention can respond to both vertical pressure and output electrical signals under bending stress. Specifically, to meet the requirements of bending deformation, the encapsulation material used in this invention is a 150-200 micrometer thick polyethylene terephthalate (PET) film. Experiments have shown that this thickness range offers the best performance in terms of thickness, flexibility, and elasticity among all encapsulation materials. Using a thinner PET film, such as a 100-micrometer or 50-micrometer film, or other encapsulation materials like polyimide (PI) films, would not achieve the ultra-high device output performance described in this invention.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. Since the piezoelectric fiber membrane prepared by electrospinning has inherent flexibility, the flexible piezoelectric devices prepared from it also have excellent flexibility. The advantage of flexible piezoelectric devices is that they can be attached to surfaces of various shapes and are easy to undergo large deformations, making them suitable for environmental mechanical energy capture and mechanical vibration sensing.

[0037] 2. The fabricated flexible piezoelectric generator device can output voltage up to 126V and power density up to 710mW / m³. -2 This is the highest value among devices of the same type.

[0038] 3. Flexible piezoelectric devices can effectively respond to mechanical vibrations below 500Hz, successfully enabling online monitoring of vibration signals from model transformers.

[0039] 4. Wireless transmission of vibration signals can be achieved by integrating flexible piezoelectric devices with wireless signal transmission modules. Attached Figure Description

[0040] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0041] Figure 1 The scanning electron microscope image shows the piezoelectric fiber membrane prepared according to an embodiment of the present invention.

[0042] Figure 2 Transmission electron microscope (TEM) image of the piezoelectric fiber membrane prepared in an embodiment of the present invention;

[0043] Figure 3 A transmission electron microscope cross-sectional image of the piezoelectric fiber membrane prepared in an embodiment of the present invention;

[0044] Figure 4 The piezoelectric coefficient of the piezoelectric fiber membrane prepared in the embodiments of the present invention is compared with that of pure PVDF-TrFE fiber and PVDF-TrFE and PC blend;

[0045] Figure 5 This is a schematic diagram of the flexible piezoelectric device structure prepared according to an embodiment of the present invention;

[0046] Figure 6 The output performance characterization diagram of the flexible piezoelectric device prepared according to an embodiment of the present invention is shown.

[0047] Figure 7 The time-domain signal diagram obtained from the transformer used to monitor the flexible piezoelectric device in this embodiment of the invention;

[0048] Figure 8 The frequency domain signal obtained from the time domain signal obtained by the flexible piezoelectric device monitoring model transformer prepared for the embodiment of the present invention is obtained by Fourier transform.

[0049] Figure 9 A schematic diagram of a wireless vibration sensing system consisting of a flexible piezoelectric device designed and fabricated for this invention, a wireless signal transmission module, and a receiving terminal (computer);

[0050] Figure 10is a schematic diagram of the interface of the wireless signal transmission system measurement software supporting the present invention. Detailed Description of the Embodiments

[0051] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that several variations and improvements can be made by those of ordinary skill in the art without departing from the concept of the present invention. All of these shall fall within the protection scope of the present invention.

[0052] Preparation of Piezoelectric Fiber Membrane

[0053] 1. Weigh 4 parts of N,N-dimethylformamide, add 1 part of PVDF-TrFE raw material, and magnetically stir for 4 hours in a 60°C water bath until the polymer is completely dissolved.

[0054] 2. Weigh 4 parts of tetrahydrofuran, add 1 part of PC raw material, and magnetically stir for 4 hours in a 60°C water bath until the polymer is completely dissolved.

[0055] 3. Inject the prepared polymer solutions into syringes equipped with coaxial needles respectively, and perform spinning using an electrospinning machine. The specifications of the coaxial needle are: 25Gp18G, the corresponding core layer needle has an inner diameter of 0.26mm, and the shell layer needle has an inner diameter of 0.86mm; the process parameters of electrospinning are: spinning voltage: 18kV; spinning rate: the spinning rate of the PVDF-TrFE shell layer is 0.7mL h -1 , the spinning rate of the PC core layer is 0.3mL h -1 .

[0056] 4. Use a drum covered with aluminum foil to collect the electrospun fibers, keep the distance between the drum collector and the spinning needle at 15cm, and keep the rotation speed of the drum collector at 1000 revolutions per minute. Peel off the aluminum foil to obtain a complete electrospun fiber membrane. The scanning electron microscope image of the composite piezoelectric fiber is as shown in Figure 1 . The core-shell structure of the composite piezoelectric fiber can be observed through a transmission electron microscope photograph, as shown in Figure 2 and Figure 3 . Figure 4 shows the comparison of piezoelectric coefficients between different types of fibers. It can be seen that the core-shell structure composite piezoelectric fiber prepared by the coaxial electrospinning method has the highest piezoelectric coefficient, which can reach 49.1C N -1 , which is 110% higher than that of pure PVDF-TrFE.

[0057] Preparation of Flexible Pressure Device

[0058] Example 1

[0059] 1. Cut the piezoelectric fiber membrane into 2cm*2cm sheets.

[0060] 2. Attach a 1.8cm*1.8cm aluminum foil sheet to the front of the cut fiber membrane as an electrode, and attach copper tape to the aluminum foil electrodes on both sides as wires;

[0061] 3. Cut two PET films with a thickness of 200μm and a size of 3.6cm*2.5cm. Use double-sided adhesive to attach the prepared fiber film with aluminum foil electrodes and copper wires between the two PET films. Then, use a press to completely compact the device under a pressure of 10MPa, completing the device encapsulation. An optical photograph of the actual piezoelectric generator device is shown below. Figure 5 As shown.

[0062] 4. Integrate flexible piezoelectric devices with wireless modules to form a wireless vibration signal transmission and monitoring system.

[0063] like Figure 6 As shown, the flexible device outputs a voltage as high as 126V under mechanical vibration excitation at 2Hz, with a maximum power density of 710mW / m². -2 .

[0064] Example 2

[0065] The device fabrication steps in Example 2 are basically the same as in Example 1, except that the effective area of ​​the piezoelectric fiber film is 2.2cm*2.2cm, the aluminum foil electrode size is 2cm*2cm, and the encapsulation PET film size is 4cm*2.8cm. The fabricated flexible piezoelectric device can achieve an output voltage of up to 121V and an output power density of 688mW / m². -2 .

[0066] Example 3

[0067] The device fabrication steps in Example 3 are basically the same as in Example 1, except that the thickness of the encapsulating PET film used is 150 μm. The fabricated flexible piezoelectric device can achieve an output voltage of 123V and an output power density of 633 mW / m². -2 .

[0068] Comparative Example 1

[0069] Comparative Example 1 is basically the same as Example 1, except that the thickness of the PET film is 100 micrometers.

[0070] The flexible device in this comparative example outputs a voltage of 71V and a power density of 246mW / m² under mechanical vibration excitation at 2Hz. -2 .

[0071] Comparative Example 2

[0072] Comparative Example 2 is basically the same as Example 1, except that the thickness of the PET film is 50 micrometers.

[0073] The flexible device in this comparative example outputs a voltage of 46V and a power density of 50mW / m² under mechanical vibration excitation at 2Hz. -2 .

[0074] Comparative Example 3

[0075] Comparative Example 3 is basically the same as Example 1, except that the encapsulation uses a 50-micron PI film.

[0076] The flexible device in this comparative example outputs a voltage of 53V and a power density of 147mW / m² under mechanical vibration excitation at 2Hz. -2 .

[0077] Comparative Example 4

[0078] Comparative Example 4 is basically the same as Example 1, except that: the piezoelectric fiber membrane uses a PVDF-TrFEpTPU core-sheath composite piezoelectric fiber; the piezoelectric coefficient of the obtained core-sheath composite piezoelectric fiber is 19.8 CC N. -1 .

[0079] The flexible device in this comparative example outputs a voltage of 22V and a power density of 3.9mW / m² under mechanical vibration excitation at 2Hz. -2 .

[0080] The flexible piezoelectric sensor prepared by the method described in this invention can not only be used as a high-performance energy harvesting device at low frequencies, but also as a vibration sensor. Figure 7 The image shows the time-domain signal obtained by monitoring the vibration of a transformer using a flexible piezoelectric device. Figure 8 The frequency domain signal obtained by Fourier transforming the time domain signal graph shows a significant response to the transformer's 100Hz main frequency, as well as the harmonics of 200Hz and 300Hz.

[0081] A wireless vibration signal transmission monitoring system integrating flexible piezoelectric devices and wireless signal transmission modules, such as... Figure 9 As shown in the figure, the vibration signal of the model transformer received in real time by the computer is as follows. Figure 10 As shown.

[0082] It should be noted that without using the electrospun piezoelectric fiber material and device assembly and packaging technology used in this method, it is impossible to obtain a flexible piezoelectric device with high output performance, and the output signal may be interfered with by factors such as triboelectric charging.

[0083] In summary, this invention provides a flexible piezoelectric energy harvesting and sensor device with ultra-high output performance, made from core-sheath composite piezoelectric fibers, and a matching wireless signal transmission module. The flexible piezoelectric device exhibits excellent energy harvesting capabilities under low-frequency mechanical vibration. At a frequency of 2Hz, the output voltage of the flexible device can reach 126V, corresponding to an output power density of 710mW / m². -2 This represents the best output performance among similar devices currently available. Furthermore, flexible piezoelectric devices can sensitively respond to mechanical vibrations below 500Hz, exhibiting excellent sensing performance. The sensing of vibration signals from a model transformer has been successfully achieved using flexible piezoelectric devices. Integrating flexible piezoelectric devices with a wireless signal transmission module also enables wireless transmission of vibration signals.

[0084] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A flexible piezoelectric device, characterized in that, The invention comprises a core-sheath composite piezoelectric fiber membrane, electrodes, leads, and device encapsulation material prepared by coaxial electrospinning. The electrodes are located on both sides of the core-sheath composite piezoelectric fiber membrane, and the device encapsulation material is disposed on the outer side of the electrodes. Leads are provided on the electrodes. The sheath polymer of the core-sheath composite piezoelectric fiber membrane is PVDF or PVDF-TrFE, and the core polymer is polycarbonate (PC). The encapsulation material is a 150-200 micrometer thick polyethylene terephthalate (PET) film. The method for fabricating the flexible piezoelectric device includes the following steps: S1. Cut the composite piezoelectric fiber membrane with an aluminum foil substrate into shape to obtain a fiber membrane sheet; S2. An aluminum foil sheet is attached to the substrate-free side of the fiber membrane as an electrode, and copper wires are placed on the aluminum foil electrodes on both sides of the fiber membrane. S3. Two polyethylene terephthalate (PET) films are attached to the outside of the fiber film with aluminum foil electrodes and copper wires prepared in step S2, and then pressed to complete the encapsulation of the device. In step S1, the composite piezoelectric fiber film with an aluminum foil substrate is prepared by a method including the following steps: A1. Dissolve PVDF-TrFE polymer raw material in N,N-dimethylformamide to prepare PVDF-TrFE polymer skin spinning solution; dissolve PC in tetrahydrofuran to prepare PC polymer core spinning solution; A2. The PVDF-TrFE polymer skin spinning solution and the PC polymer core spinning solution are coaxially electrospun. A3. Collect the electrospun fibers prepared in step A2 using a roller covered with aluminum foil, and obtain an electrospun fiber membrane after peeling off the aluminum foil.

2. The flexible piezoelectric device according to claim 1, characterized in that, In step S1, the size of the fiber membrane is 2cm. 2 cm~2.5 cm 2.5 cm; In step S2, the aluminum foil sheet has a size of 1.8 cm. 1.8 cm ~ 2.3 cm 2.3 cm; In step S3, the size of the polyethylene terephthalate (PET) film is 3.6 cm. 2.5 cm ~ 4 cm 3 cm, with a thickness of 150~200μm.

3. The flexible piezoelectric device according to claim 1, characterized in that, The copper conductor is copper tape.

4. The flexible piezoelectric device according to claim 1, characterized in that, The compaction is achieved by using a press to compact the device under a pressure of 5~10 MPa.

5. The flexible piezoelectric device according to claim 1, characterized in that, The mass fraction of PVDF-TrFE in the PVDF-TrFE polymer sheath spinning solution is 16%~24%; the mass fraction of PC in the PC polymer core spinning solution is 16%~24%.

6. The flexible piezoelectric device according to claim 1, characterized in that, In step A1, the dissolution is achieved by heating in a water bath to 60℃~80℃ and stirring for 4~6 hours to completely dissolve the polymer and form a clear solution; in step A2, the parameters for the electrospinning process are set as follows: spinning voltage: 15~22 kV; spinning rate: the spinning rate of the PVDF-TrFE skin is 0.5~0.9 mL h. -1 The spinning rate of the PC core layer is 0.1~0.3 mL / h. -1 .

7. A wireless vibration signal transmission monitoring system, characterized in that, The invention includes the flexible piezoelectric device as described in any one of claims 1-6, a wireless signal transmission module electrically connected to the flexible piezoelectric device, and wireless signal acquisition software.

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