Piezoelectric sensor and preparation method thereof

Abstract

The invention discloses a piezoelectric sensor and a preparation method thereof, the piezoelectric sensor comprises a top packaging layer, a stress transfer layer, a stretchable piezoelectric film layer and a bottom packaging layer, the lower surface of the top packaging layer is provided with a flexible groove, the upper surface of the bottom packaging layer is provided with a rigid groove, and the flexible groove and the rigid groove are arranged in parallel. The lower surface of the top packaging layer is fixedly attached to the upper surface of the bottom packaging layer, the piezoelectric film layer is fixed between the flexible groove and the rigid groove, the stress transfer layer is arranged in the flexible groove, and the stress transfer layer is of a T-shaped structure. External force is transmitted to the piezoelectric film layer through the stress transmission layer of the T-shaped structure, conversion from pressure to tension is achieved, large voltage can be generated under the small external force, and therefore the sensitivity of the sensor to small pressure detection is greatly improved. The method can be widely applied to the technical field of sensor preparation.

Description

Technical Field

[0001] The present application relates to the technical field of sensor preparation, and in particular to a piezoelectric sensor and a preparation method thereof. Background Art

[0002] PVDF piezoelectric film mainly relies on the dipole deflection caused by its own mechanical deformation during the force process to generate voltage signals. Most of the traditional PVDF-based piezoelectric sensor structures are "sandwich" configurations, and are usually d 33 mode. When pressure is applied, the piezoelectric film is compressed, causing the polarization dipole to deflect, thereby generating opposite charges on the electrodes. However, PVDF piezoelectric film is difficult to compress under small pressures. Although piezoelectric film can be deformed under large pressures, due to the extremely limited compressible range of piezoelectric film, only a weak voltage can be generated even under large pressures. In summary, traditional piezoelectric sensors tend to have low sensitivity and are difficult to detect tiny pressures. Summary of the invention

[0003] In order to solve the above technical problems, the purpose of the present invention is to provide a piezoelectric sensor and a preparation method thereof, which can improve the sensitivity of the sensor and realize accurate detection of tiny pressures.

[0004] To achieve the above-mentioned purpose, one aspect of an embodiment of the present application proposes a piezoelectric sensor, including a top packaging layer, a stress transfer layer, a stretchable piezoelectric film layer and a bottom packaging layer, the lower surface of the top packaging layer is provided with a flexible groove, the upper surface of the bottom packaging layer is provided with a rigid groove, the lower surface of the top packaging layer is bonded and fixed to the upper surface of the bottom packaging layer, the piezoelectric film layer is fixed between the flexible groove and the rigid groove, the stress transfer layer is provided in the flexible groove, and the stress transfer layer is a T-shaped structure.

[0005] In some embodiments, the piezoelectric sensor further includes an electrode layer, and the electrode layer is coated on the upper and lower surfaces of the piezoelectric film layer.

[0006] In some embodiments, the material of the top encapsulation layer includes but is not limited to one of polydimethylsiloxane, eco-elastomer, polyurethane elastomer, hydrogenated styrene-butadiene-styrene block copolymer or styrene-butadiene-styrene block copolymer.

[0007] In some embodiments, the material of the stress transfer layer and the bottom packaging layer includes but is not limited to one of polymethyl methacrylate, pure metal, alloy, quartz or ceramic.

[0008] In some embodiments, the material of the piezoelectric thin film layer includes, but is not limited to, one of polyvinylidene fluoride, polyvinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer, polyhydroxybutyrate, or polylactic acid.

[0009] To achieve the above object, on the other hand, an embodiment of the present application provides a method for manufacturing a piezoelectric sensor, including the following steps:

[0010] Manufacture a top encapsulation layer with a flexible groove on its lower surface;

[0011] Manufacture a stress transfer layer with a T-shaped structure, and bond the stress transfer layer in the middle of the flexible groove;

[0012] Manufacture a bottom encapsulation layer with a rigid groove on its upper surface;

[0013] Manufacture a piezoelectric thin film layer, and fix the piezoelectric thin film layer on the rigid groove;

[0014] Bond and fix the lower surface of the top encapsulation layer to the upper surface of the bottom encapsulation layer to obtain a piezoelectric sensor.

[0015] In some embodiments, the manufacturing of the top encapsulation layer with a flexible groove on its lower surface specifically includes:

[0016] Obtain a rigid polymer;

[0017] Carve the rigid polymer to obtain a rigid mold;

[0018] Mix a polydimethylsiloxane precursor and a curing agent according to a preset weight ratio to obtain a polymer material;

[0019] Pour the polymer material into the rigid mold and cure it to obtain the top encapsulation layer with the flexible groove on its lower surface.

[0020] In some embodiments, the manufacturing of the bottom encapsulation layer with a rigid groove on its upper surface specifically includes:

[0021] Obtain a rigid polymer;

[0022] Carve the rigid groove on the rigid polymer to obtain the bottom encapsulation layer with the rigid groove on its upper surface.

[0023] In some embodiments, the manufacturing of the piezoelectric thin film layer specifically includes:

[0024] Obtain a piezoelectric thin film and an electrode layer;

[0025] The electrode layer is coated on the upper and lower surfaces of the piezoelectric thin film, and the piezoelectric thin film coated with the electrode layer is sheared to obtain the piezoelectric thin film layer.

[0026] In some embodiments, the preparation method further includes:

[0027] Silver-plated copper wires are connected to both ends of the electrode layer.

[0028] The beneficial effects of the present invention are as follows: The piezoelectric sensor and its preparation method of the present invention, the piezoelectric sensor includes a top encapsulation layer, a stress transfer layer, a stretchable piezoelectric thin film layer, and a bottom encapsulation layer. A flexible groove is provided on the lower surface of the top encapsulation layer, and a rigid groove is provided on the upper surface of the bottom encapsulation layer. The lower surface of the top encapsulation layer is fixedly attached to the upper surface of the bottom encapsulation layer. The piezoelectric thin film layer is fixed between the flexible groove and the rigid groove, and the stress transfer layer is disposed in the flexible groove. Among them, the stress transfer layer is a T-shaped structure. The present invention transfers the external force to the piezoelectric thin film layer through the T-shaped stress transfer layer to achieve the conversion of pressure to tension. In this force conversion process, the pressure will be amplified several times into the tension along the film direction, so that the working mode of the sensor changes from d 33 to d 31 , realizing the stretching of the piezoelectric thin film. Since the voltage generated by the PVDF piezoelectric thin film is often proportional to the external force stimulation, this force amplification effect can enable the sensor to generate a large voltage under a small external force, thereby improving the sensitivity of the sensor to small pressure detection. Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following introduces the drawings required to be used in the embodiments of the present invention. It should be understood that the drawings introduced below only conveniently and clearly represent some embodiments of the technical solutions in the present invention. For those skilled in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 It is a schematic structural diagram of a piezoelectric sensor provided by an embodiment of the present invention;

[0031] Figure 2(a) is a schematic diagram of the initial state of a traditional piezoelectric sensor provided by an embodiment of the present invention;

[0032] Figure 2(b) is a schematic diagram of the pressure-applied state of a traditional piezoelectric sensor provided by an embodiment of the present invention;

[0033] Figure 3(a) is a schematic diagram of the initial state of the piezoelectric sensor provided by an embodiment of the present invention;

[0034] Figure 3(b) is a schematic diagram of the pressure applied to the piezoelectric sensor provided by an embodiment of the present invention;

[0035] Figure 4(a) is a schematic diagram of the initial form of the simplified model provided by the embodiment of the present invention;

[0036] Figure 4(b) is a schematic diagram of the form of the simplified model provided by the embodiment of the present invention under the applied pressure;

[0037] Figure 5 It is a relationship diagram of pressure, tensile force and amplification factor varying with angle provided by the embodiment of the present invention;

[0038] Figure 6 It is a comparison diagram of the pressure-voltage performance between the piezoelectric sensor provided by the embodiment of the present invention and the traditional piezoelectric sensor;

[0039] Figure 7 It is a step flow chart of a preparation method of a piezoelectric sensor provided by the embodiment of the present invention;

[0040] Figure 8 It is a process flow chart of the preparation of the piezoelectric sensor provided by the embodiment of the present invention.

[0041] Reference numerals: 01, top encapsulation layer; 02, stress transfer layer; 03, piezoelectric thin film layer; 04, bottom encapsulation layer; 05, electrode layer; 101, flexible groove; 102, rigid groove; 201, dipole. Detailed implementation manners

[0042] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation manners described in the following exemplary embodiments do not represent all implementation manners consistent with the embodiments of the present application. They are only examples of devices and methods consistent with some aspects of the embodiments of the present application detailed in the appended claims.

[0043] It can be understood that the terms "first", "second", etc. used in the present application can be used herein to describe various concepts, but unless otherwise specified, these concepts are not limited by these terms. These terms are only used to distinguish one concept from another. For example, without departing from the scope of the embodiments of the present application, the first information can also be called the second information, and similarly, the second information can also be called the first information. Depending on the context, the words "if", "when" as used herein can be interpreted as "when...", "when...", or "in response to determination".

[0044] The terms "at least one", "multiple", "each", "any", etc. used in this application, at least one includes one, two or more, multiple includes two or more, each refers to each of the corresponding multiple, and any refers to any one of the multiple.

[0045] Before explaining the embodiments of the present application in detail, some nouns and terms involved in the embodiments of the present application are first explained. The nouns and terms involved in the embodiments of the present application are subject to the following explanations.

[0046] d 33 Model: Indicates that the polarization direction (3-axis, usually the thickness direction) is consistent with the applied stress direction (also 3-axis). Mechanism: When the material is compressed or stretched in the thickness direction, the change in the spacing of the dipoles causes the polarization strength to change, thereby generating charges on the upper and lower surfaces.

[0047] d 31 Model: Indicates that the polarization direction (3-axis) is orthogonal to the applied in-plane stress direction (1-axis, such as the stretching direction of the film). Mechanism: In-plane stress (such as bending or stretching) causes thickness direction strain through the Poisson effect, resulting in a change in the dipole density, which generates charge in the thickness direction.

[0048] PVDF piezoelectric film mainly relies on the dipole deflection caused by its own mechanical deformation during the force process to generate voltage signals. Most of the traditional PVDF-based piezoelectric sensor structures are "sandwich" configurations, and are usually d 33 mode. When pressure is applied, the piezoelectric film is compressed, causing the polarization dipole to deflect, thereby generating opposite charges on the electrodes. However, PVDF piezoelectric film is difficult to compress under small pressures. Although piezoelectric film can be deformed under large pressures, due to the extremely limited compressible range of piezoelectric film, only a weak voltage can be generated even under large pressures. In summary, traditional piezoelectric sensors tend to have low sensitivity and are difficult to detect tiny pressures.

[0049] To this end, an embodiment of the present invention proposes a piezoelectric sensor, which includes a top packaging layer, a stress transfer layer, a stretchable piezoelectric film layer and a bottom packaging layer. The lower surface of the top packaging layer is provided with a flexible groove, the upper surface of the bottom packaging layer is provided with a rigid groove, the lower surface of the top packaging layer is bonded and fixed to the upper surface of the bottom packaging layer, the piezoelectric film layer is fixed between the flexible groove and the rigid groove, and the stress transfer layer is provided in the flexible groove, wherein the stress transfer layer is a T-shaped structure. The present invention transfers external force to the piezoelectric film layer through the stress transfer layer of the T-shaped structure to realize the conversion from pressure to tension. In this force conversion process, the pressure will be amplified several times to become tension along the film direction, so that the sensor working mode changes from d 33 Transformed into d31 , the stretching of the piezoelectric film is realized. Since the magnitude of the voltage generated by the PVDF piezoelectric film is often proportional to the external force stimulus, this force amplification effect enables the sensor to generate a large voltage under a small external force, thereby improving the sensitivity of the sensor to small pressure detection. This piezoelectric sensor can be applied to industrial detection, smart home, and structural health monitoring scenarios, but is not limited thereto.

[0050] Referring to Figure 1 , Figure 1 is a schematic structural diagram of a piezoelectric sensor provided by an embodiment of the present invention. An embodiment of the present invention proposes a piezoelectric sensor, including a top encapsulation layer 01, a stress transfer layer 02, a stretchable piezoelectric film layer 03, and a bottom encapsulation layer 04. A flexible groove 101 is provided on the lower surface of the top encapsulation layer 01, and a rigid groove 102 is provided on the upper surface of the bottom encapsulation layer 04. The lower surface of the top encapsulation layer 01 is fixedly attached to the upper surface of the bottom encapsulation layer 04. The piezoelectric film layer 03 is fixed between the flexible groove 101 and the rigid groove 102, and the stress transfer layer 02 is disposed in the flexible groove 101, wherein the stress transfer layer 02 is a T-shaped structure.

[0051] Specifically, traditional piezoelectric sensors usually work in the d 33 mode. As shown in Fig. 2(a), it is a schematic diagram of the initial state of a traditional piezoelectric sensor, and as shown in Fig. 2(b), it is a schematic diagram of the pressure-applied state of a traditional piezoelectric sensor. When pressure is applied, the piezoelectric film will be compressed, causing the deflection of the polarization dipoles 201, thereby generating opposite charges on the electrodes. The voltage signal generated by the piezoelectric sensor is proportional to the magnitude of the external force applied. Under small pressure, it is difficult to compress the piezoelectric film, so its sensitivity to small pressure signals is relatively low. As shown in Fig. 3(a), it is a schematic diagram of the initial state of the piezoelectric sensor according to an embodiment of the present invention, and as shown in Fig. 3(b), it is a schematic diagram of the pressure application of the piezoelectric sensor according to an embodiment of the present invention. The top plane of the T-shaped structure of the stress transfer layer 02 adheres to the flexible groove 101, and the bottom tip contacts the piezoelectric film layer 03. Based on the flexible top encapsulation layer 01, the T-shaped stress transfer layer 02, and the bottom encapsulation layer 04 with the rigid groove 102, the piezoelectric sensor can achieve the conversion of pressure to tension. In this force conversion process, the pressure will be amplified several times into tension along the film direction, enabling the sensor working mode to change from d 33 to d 31 , realizing the stretching of the piezoelectric film, triggering the deflection of the dipoles 201. Through this force amplification and conversion effect, even under small pressure stimuli, the sensor can generate a large voltage, thereby improving the sensitivity of the sensor to small pressure detection.

[0052] Furthermore, to simulate the pressure-tension conversion process, a simplified model of a piezoelectric sensor was established. As shown in Fig. 4(a), it is a schematic diagram of the initial form of the simplified model, and as shown in Fig. 4(b), it is a schematic diagram of the form of the simplified model under the applied pressure. With the piezoelectric film fixed at both ends, applying a vertical force F to the suspended film will generate a tensile strain on the film, generating a tensile force F along the film direction t , where F = 2F t sinθ. To emphasize this amplification effect, an amplification factor m f is defined as:

[0053]

[0054] As Figure 5 shown in the relationship diagram of pressure, tensile force, and amplification factor varying with the angle, when the range of θ is 0° < θ < 30°, the amplification factor is greater than 1. Therefore, within this range, the pressure-tension conversion process will be amplified. This force amplification effect helps the structure in detecting small pressures, highlighting its potential in highly sensitive detection of tiny forces

[0055] It should be noted that the pressure transfer layer can also be a hemispherical structure, a conical structure, a wedge-shaped structure, etc., to achieve single-point contact at one end and planar contact at the other end

[0056] Referring to Figure 1 , further as an optional implementation manner, the piezoelectric sensor further includes an electrode layer 05, and the electrode layer 05 is coated on the upper and lower surfaces of the piezoelectric film layer 03

[0057] In some optional embodiments, the electrode layer 05 is used to transfer the charges generated by the piezoelectric film to an external circuit, and the electrode layer 05 can adopt electrode materials with good conductivity such as silver electrodes, gold electrodes, copper electrodes, aluminum electrodes, etc

[0058] Further as an optional implementation manner, the material of the top encapsulation layer 01 includes but is not limited to one of polydimethylsiloxane, ecological elastomer, polyurethane elastomer, hydrogenated styrene-butadiene-styrene block copolymer, or styrene-butadiene-styrene block copolymer

[0059] It should be noted that the material of the top encapsulation layer 01 can be a stretchable elastomer such as polydimethylsiloxane, ecological elastomer, polyurethane elastomer, hydrogenated styrene-butadiene-styrene block copolymer, or styrene-butadiene-styrene block copolymer, etc. It can be specifically selected according to actual needs and is not limited here

[0060] Exemplarily, in the embodiments of the present invention, polydimethylsiloxane (PDMS) is selected as the top encapsulation layer 01. Polydimethylsiloxane (PDMS) is a silicone polymer, the main chain of which is composed of silicon-oxygen bonds (Si—O—Si), and the side chains are methyl groups (CH3).

[0061] Further as an alternative embodiment, the materials of the stress transfer layer 02 and the bottom encapsulation layer 04 include but are not limited to one of polymethyl methacrylate, pure metal, alloy, quartz or ceramic.

[0062] It should be noted that the materials of the stress transfer layer 02 and the bottom encapsulation layer 04 can be rigid processable materials such as polymethyl methacrylate, pure metal, alloy, quartz or ceramic, and can be specifically selected according to actual needs, which are not limited herein.

[0063] Exemplarily, in the embodiments of the present invention, rigid polymethyl methacrylate (PMMA) is selected as the stress transfer layer 02 and the bottom encapsulation layer 04. Polymethyl methacrylate (PMMA) is a transparent, colorless thermoplastic with excellent light transmittance, weather resistance and processing performance. As the stress transfer layer 02, it makes single-point contact with the piezoelectric thin film layer 03, and the rigid characteristics enable the piezoelectric thin film layer 03 to be stretched when subjected to an external force. As the bottom encapsulation layer 04, the rigid grooves 102 provided thereon can allow the piezoelectric thin film layer 03 to bend and deform.

[0064] Further as an alternative embodiment, the materials of the piezoelectric thin film layer 03 include but are not limited to one of polyvinylidene fluoride, polyvinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer, polyhydroxybutyrate or polylactic acid.

[0065] It should be noted that the material of the piezoelectric thin film layer 03 can be a stretchable organic piezoelectric material such as polyvinylidene fluoride, polyvinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer, polyhydroxybutyrate or polylactic acid, and can be specifically selected according to actual needs, which are not limited herein.

[0066] Exemplarily, the stretchable piezoelectric thin film in the embodiments of the present invention is composed of a uniaxially oriented high-modulus PVDF (polyvinylidene fluoride) thin film and exhibits reversible Hookean elastic deformation.

[0067] In summary, the piezoelectric sensor proposed in the embodiment of the present invention designs a piezoelectric device with four layers, namely a soft top encapsulation layer 01, a rigid T-shaped structure stress transfer layer 02, a stretchable piezoelectric thin film layer 03, and a bottom encapsulation layer 04 with a rigid groove 102. The top encapsulation layer is made of soft polydimethylsiloxane (PDMS) to protect the piezoelectric thin film from potential damage and allow the applied external force to be transmitted to the stress transfer layer; the stress transfer layer is made of rigid polymethyl methacrylate (PMMA) with a T-shaped structure to transmit the external force to the piezoelectric thin film layer and ensure precise single-point contact with the piezoelectric thin film layer; the stretchable piezoelectric thin film layer is composed of a uniaxially oriented high-modulus polyvinylidene fluoride (PVDF) film, showing reversible Hookean elastic deformation and ensuring the stability of the device; the rigid groove 102 allows the piezoelectric thin film to bend and deform, thereby realizing the d 31 working mode. As Figure 6 shown in the pressure-voltage performance comparison diagram of the piezoelectric sensor of the embodiment of the present invention and the traditional piezoelectric sensor, it can be seen from Figure 6 that the piezoelectric sensor proposed in the embodiment of the present invention can generate a large voltage under a small pressure due to its ability to amplify the pressure several times into tension, and its piezoelectric performance and sensitivity are much higher than those of the traditional piezoelectric sensor.

[0068] The structure and working principle of the piezoelectric sensor of the embodiment of the present invention are described above. It can be recognized that compared with the existing piezoelectric devices, in the embodiment of the present invention, the external force is transmitted to the piezoelectric thin film layer through the stress transfer layer with a T-shaped structure to realize the conversion of pressure to tension. In this force conversion process, the pressure will be amplified several times into tension along the film direction, so that the working mode of the sensor changes from d 33 to d 31 to realize the stretching of the piezoelectric thin film, and a large voltage can be generated under a small external force, thereby improving the sensitivity of the sensor to detect small pressures.

[0069] Referring to Figure 7 , Figure 7 which is the step flowchart of a preparation method of a piezoelectric sensor provided by the embodiment of the present invention. The embodiment of the present invention also provides a preparation method of a piezoelectric sensor, including the following steps S101 to S105:

[0070] S101. Prepare a top encapsulation layer with a flexible groove on the lower surface;

[0071] Further as an optional implementation manner, the step of preparing a top encapsulation layer with a flexible groove on the lower surface can be specifically further divided into the following steps S1011 to S1014:

[0072] S1011. Obtain a rigid polymer;

[0073] S1012. Engrave the rigid polymer to obtain a rigid mold;

[0074] S1013. Mix the polydimethylsiloxane precursor and the curing agent according to a preset weight ratio to obtain a polymer material;

[0075] S1014. Pour the polymer material into the rigid mold and cure it to obtain a top encapsulation layer with a flexible groove on the lower surface.

[0076] Specifically, as Figure 8 shown is the process flow chart for preparing a piezoelectric sensor, and a top encapsulation layer with a flexible groove on the lower surface is prepared. First, use a laser cutter to engrave a rigid polymer. The material of the rigid polymer is polymethyl methacrylate (PMMA) to obtain a rigid mold. Mix the liquid polydimethylsiloxane (PDMS) precursor and the curing agent according to a preset weight ratio, pour them into the rigid mold, and then cure the rigid mold at a temperature of 80 °C for 30 minutes to obtain the top encapsulation layer.

[0077] It should be noted that in the embodiment of the present invention, the preset weight ratio is selected as a weight ratio of 10:1 to mix the liquid polydimethylsiloxane (PDMS) precursor and the curing agent. This preset weight ratio can also be set according to actual needs, such as adjusted within the weight ratio range of 3:1 to 30:1.

[0078] In the embodiment of the present invention, the size of the flexible groove of the top encapsulation layer can be set to a width of 8 mm, a depth of 2 mm, and the groove length can be one of the values such as 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, etc. The size of the flexible groove can be set according to actual needs and is not limited herein.

[0079] S102. Prepare a stress transfer layer with a T-shaped structure and bond the stress transfer layer in the middle of the flexible groove;

[0080] Specifically, use a laser cutter to make a stress transfer layer with a rigid T-shaped structure and bond it in the middle of the flexible groove with epoxy glue.

[0081] S103. Prepare a bottom encapsulation layer with a rigid groove on the upper surface;

[0082] Further as an optional implementation manner, the step of preparing a bottom encapsulation layer with a rigid groove on the upper surface can be specifically divided into the following steps S1031 and S1032:

[0083] S1031. Obtain a rigid polymer;

[0084] S1032. Engrave a rigid groove on the rigid polymer to obtain a bottom encapsulation layer with a rigid groove on the upper surface.

[0085] Specifically, a rigid groove is engraved on a rigid polymer (polymethyl methacrylate, PMMA) using a laser cutting machine to obtain a bottom encapsulation layer. The size of the rigid groove corresponds to that of the flexible groove and can be set to, for example, a width of 8 mm, a depth of 2 mm, and the groove length can be one of the values such as 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, etc.

[0086] S104. Prepare a piezoelectric thin film layer and fix the piezoelectric thin film layer on the rigid groove.

[0087] Further, as an optional implementation manner, the step of preparing the piezoelectric thin film layer can be specifically further divided into the following steps S1041 and S1042:

[0088] S1041. Obtain a piezoelectric thin film and an electrode layer.

[0089] S1042. Coat electrode layers on the upper and lower surfaces of the piezoelectric thin film, and shear the piezoelectric thin film coated with the electrode layers to obtain a piezoelectric thin film layer.

[0090] Further, as an optional implementation manner, the preparation method further includes the following step S114:

[0091] S114. Connect silver-plated copper wires to both ends of the electrode layer.

[0092] Specifically, the piezoelectric thin film is made of polyvinylidene fluoride (PVDF). Conductive silver paste (electrode layer) is coated on the piezoelectric thin film to obtain a PVDF piezoelectric electrode. Then, the film is cut into an appropriate size, and the silver-plated copper wire is connected to the silver electrode through the silver paste to obtain a piezoelectric thin film layer. The piezoelectric thin film layer is fixed on the rigid groove of the bottom encapsulation layer with epoxy glue.

[0093] S105. Bond and fix the lower surface of the top encapsulation layer to the upper surface of the bottom encapsulation layer to obtain a piezoelectric sensor.

[0094] Specifically, the flexible groove of the top encapsulation layer is assembled on the rigid groove of the bottom encapsulation layer for assembly to obtain a piezoelectric sensor.

[0095] The content in the above piezoelectric sensor embodiments is applicable to the embodiment of the preparation method of this piezoelectric sensor. The functions specifically realized by the embodiment of the preparation method of this piezoelectric sensor are the same as those of the above piezoelectric sensor embodiments, and the beneficial effects achieved are also the same as those of the above piezoelectric sensor embodiments.

[0096] In the foregoing description of the present specification, the descriptions referring to terms such as "one embodiment / example", "another embodiment / example", or "certain embodiments / examples" etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In the present specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0097] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the claims and their equivalents.

[0098] The above is a specific description of the preferred embodiments of the present invention, but the present invention is not limited to the embodiments. Those skilled in the art can also make various equivalent deformations or substitutions without departing from the spirit of the present invention, and these equivalent deformations or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A piezoelectric sensor, characterized in that, It includes a top encapsulation layer, a stress transfer layer, a stretchable piezoelectric thin film layer, and a bottom encapsulation layer. A flexible groove is provided on the lower surface of the top encapsulation layer, and a rigid groove is provided on the upper surface of the bottom encapsulation layer. The lower surface of the top encapsulation layer is fixedly attached to the upper surface of the bottom encapsulation layer. The piezoelectric thin film layer is fixed between the flexible groove and the rigid groove, and the stress transfer layer is disposed in the flexible groove. Among them, the stress transfer layer is a T-shaped structure.

2. The piezoelectric sensor according to claim 1, characterized in that The piezoelectric sensor further includes an electrode layer, and the electrode layer is coated on the upper and lower surfaces of the piezoelectric thin film layer.

3. The piezoelectric sensor according to claim 1, characterized in that, The material of the top encapsulation layer includes but is not limited to one of polydimethylsiloxane, ecological elastomer, polyurethane elastomer, hydrogenated styrene-butadiene-styrene block copolymer, or styrene-butadiene-styrene block copolymer.

4. The piezoelectric sensor according to claim 1, characterized in that The materials of the stress transfer layer and the bottom encapsulation layer include but are not limited to one of polymethyl methacrylate, pure metal, alloy, quartz, or ceramic.

5. The piezoelectric sensor according to claim 1, characterized in that The material of the piezoelectric thin film layer includes but is not limited to one of polyvinylidene fluoride, polyvinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer, polyhydroxybutyrate, or polylactic acid.

6. A preparation method of a piezoelectric sensor for preparing the piezoelectric sensor according to any one of claims 1 to 5, characterized in that, It includes the following steps: Prepare a top encapsulation layer with a flexible groove on its lower surface; Prepare a stress transfer layer with a T-shaped structure and bond the stress transfer layer in the middle of the flexible groove; Prepare a bottom encapsulation layer with a rigid groove on its upper surface; Prepare a piezoelectric thin film layer and fix the piezoelectric thin film layer on the rigid groove; Attach and fix the lower surface of the top encapsulation layer to the upper surface of the bottom encapsulation layer to obtain a piezoelectric sensor.

7. The preparation method according to claim 6, characterized in that The preparation of the top encapsulation layer with a flexible groove on its lower surface specifically includes: Obtain a rigid polymer; Carve the rigid polymer to obtain a rigid mold; Mix a polydimethylsiloxane precursor and a curing agent according to a preset weight ratio to obtain a polymer material; Pour the polymer material into the rigid mold and cure it to obtain the top encapsulation layer with the flexible groove on its lower surface.

8. The preparation method according to claim 6, characterized in that, The preparation of the bottom encapsulation layer with a rigid groove on its upper surface specifically includes: Obtain a rigid polymer; Carve the rigid groove on the rigid polymer to obtain the bottom encapsulation layer with the rigid groove on its upper surface.

9. The preparation method according to claim 6, characterized in that, The preparation of the piezoelectric thin film layer specifically includes: Obtain a piezoelectric thin film and an electrode layer; Coat the electrode layer on the upper and lower surfaces of the piezoelectric thin film, and shear the piezoelectric thin film coated with the electrode layer to obtain the piezoelectric thin film layer.

10. The preparation method according to claim 9, characterized in that, The preparation method further includes: Connect silver-plated copper wires to both ends of the electrode layer.

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