Electret piezoelectric sensing device and preparation method thereof

Abstract

The invention discloses an electret piezoelectric sensing device and a preparation method thereof. The electret piezoelectric sensing device comprises a polarized electricity storage material layer and an electrode layer; the electricity storage material layer comprises a plurality of PTFE compact layers and at least one porous layer which are stacked and tightly combined, the porous layer is arranged between the two compact layers, and the two end faces of the porous layer are compact layers. According to the piezoelectric device provided by the invention, optimized electric field distribution is formed near the hole, a pressure change layer is generated on a bonding interface through hot pressing bonding, the molecular orientation and conformation of the interface are changed, a field plate effect is formed, the sensitive degree of polarized charges to pressure deformation can be improved under the combined effect, and the residence capability of the polarized charges is improved; therefore, by combining the PTFE composite film technology with piezoelectricity, the functional material which is high in performance, durable and suitable for complex environments is manufactured, and the functional material can stably work in severe environments such as high temperature and high corrosivity and has wide application prospects.

Description

Technical Field

[0001] The invention relates to an electret piezoelectric sensor device and a preparation method thereof, belonging to the field of piezoelectric sensor devices, in particular to the technical field of electromechanical energy conversion. Background Art

[0002] The description in this section merely provides background information related to the present disclosure and does not constitute prior art.

[0003] Piezoelectric sensors are widely used in various detection and measurement fields because of their ability to convert mechanical energy into electrical energy. Although common piezoelectric materials used to prepare core sensitive materials for piezoelectric sensors, such as ferroelectric polymer PDVF and piezoelectric electret PP, have good piezoelectric properties, their performance will be limited in certain special environments, such as high temperature and highly corrosive environments. PTFE, as an excellent engineering plastic, has excellent properties such as high temperature resistance and chemical corrosion resistance. Therefore, the research and development of piezoelectric sensors based on PTFE materials is of great significance.

[0004] However, the PTFE piezoelectric devices obtained by the same single-layer polarization treatment as piezoelectric materials such as PDVF and PP often cannot obtain more sensitive sensing characteristics and more stable polarization electric fields, and their structure needs to be further improved.

[0005] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the present invention and facilitating the understanding of those skilled in the art. It cannot be considered that the technical solutions of the present invention are well known to those skilled in the art simply because these solutions are described in the background technology section of the present invention. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a piezoelectric sensor device based on the electret principle and a preparation method thereof, so as to improve the piezoelectric induction sensitivity and the stability of the polarization electric field of the PTFE piezoelectric sensor device.

[0007] In order to solve the above technical problems, the present invention provides an electret piezoelectric sensor device, comprising a polarized energy storage material layer and electrode layers arranged on both sides of the energy storage material layer; the energy storage material layer comprises a plurality of dense PTFE material layers and at least one porous PTFE material layer that are stacked and tightly combined, the porous PTFE material layer is arranged between any two adjacent dense PTFE material layers, and the dense PTFE material layers are in direct contact with the electrode layers on both sides.

[0008] Furthermore, along the stacking direction, the dense PTFE material layers and the porous PTFE material layers are alternately arranged.

[0009] Furthermore, the dense PTFE material layer and the porous PTFE material layer are combined by hot pressing, and a hot pressing deformation interface exists between any of the dense PTFE material layers and the porous PTFE material layer.

[0010] Furthermore, the porosity of the porous PTFE material layer is 20-95%, and the pore size of the internal holes ranges from 0.5 to 100 μm.

[0011] Furthermore, the thickness of the porous PTFE material layer is 5-500 μm;

[0012] Furthermore, the thickness of the dense PTFE material layer is 1-100 μm.

[0013] Furthermore, the electret piezoelectric sensor device also includes a packaging layer and a lead, the packaging layer wraps the electrode layer and the power storage material layer, and the lead is in conductive contact with the electrode layer and penetrates the packaging layer to reach outside the packaging layer.

[0014] Furthermore, the material of the encapsulation layer includes any one of PI, FEP, PP, and PET, or a combination of two or more thereof.

[0015] Furthermore, the electrode layer includes metal or conductive tape.

[0016] The second aspect of the present invention also provides a method for preparing the above-mentioned electret piezoelectric sensor device, which comprises:

[0017] Providing multiple dense PTFE material layers and at least one porous PTFE material layer

[0018] The dense PTFE material layer and the porous PTFE material layer are stacked and combined, and the porous PTFE material layer is arranged between any two adjacent dense PTFE material layers, and the two end surfaces are the dense PTFE material layers, to form a combination;

[0019] Performing a hot pressing treatment on the assembly to obtain an electricity storage material layer;

[0020] Covering the two end surfaces of the electricity storage material layer with electrode layers;

[0021] During the preparation process, an electric field may be applied to the non-electrode surface of the storage material layer with electrode material to perform corona poling treatment, or corona poling may be completed before the electrode layer is applied.

[0022] Furthermore, the preparation method also includes the steps of covering the periphery of the combined structure formed by the energy storage material layer and the electrode layer with a packaging layer, and providing leads penetrating the packaging layer.

[0023] Furthermore, the hot pressing treatment adopts a roller pressing method, the pressing temperature is set to 160-380°C, the pressure is 1-1.5MPa, the diameter of the pressing roller is 5-10cm, and the travel speed is 0.5-1m / s.

[0024] Furthermore, the corona polarization treatment includes a polarization process and an aging process; the voltage of the polarization process is 10-15 kV, the temperature is 15-35° C., and the time is 0.1 s-30 min; the temperature of the aging treatment is 120-200° C., and the time is 10-60 min.

[0025] By means of the above technical solution, the beneficial effects of the present invention at least include:

[0026] The piezoelectric device provided by the present invention forms an optimized electric field distribution near the hole by setting a porous PTFE material layer in the middle and dense PTFE material layers on both sides, and combines each material layer by hot pressing, so that a new charge trap is generated at the bonding interface, and the retention capacity of polarized charge is improved. The two work together to significantly improve the sensitivity of polarized charge to pressure deformation. Therefore, by combining the process of PTFE composite membrane with piezoelectricity, a high-performance, durable and complex environment-suitable functional material can be manufactured, which can work stably in harsh environments such as high temperature and high corrosion, and has broad application prospects.

[0027] The above description is only an overview of the technical solution of the present invention. In order to enable those skilled in the art to more clearly understand the technical means of the present application and implement them according to the contents of the specification, the following is a description of the preferred embodiments of the present invention in conjunction with detailed drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic diagram of charge distribution of an electric storage material layer provided by a typical implementation case of the present invention;

[0029] Figure 2 It is a schematic diagram of the interlayer structure of the electricity storage material layer provided by a typical implementation case of the present invention;

[0030] Figure 3 It is a complete structural schematic diagram of an electret piezoelectric sensor device provided in a typical implementation case of the present invention. Description of the drawings:

[0032] 1. Electrode basic electret; 2. Positive polarity space charge; 3. Pores; 4. Negative polarity space charge; 5. Dense PTFE material layer; 6. Porous PTFE material layer; 7. Dense PTFE material layer; 8. Electrode layer; 9. Encapsulation layer; 10. Electricity storage material layer; 11. Lead wire. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] It should be noted that, in the description of the present invention, the terms "first", "second", etc. are only used for descriptive purposes and to distinguish similar objects. There is no order of precedence between the two, and they cannot be understood as indicating or implying relative importance. In addition, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0035] Based on the deficiencies in the prior art, the purpose of the present invention is to provide a piezoelectric sensor based on a PTFE flexible electromechanical energy conversion composite film and a preparation method thereof, which has good piezoelectric properties and ultra-high external force monitoring sensitivity, can effectively reduce the complexity of the sensor's later signal processing, and can work stably in high temperature and highly corrosive environments.

[0036] The main technical idea adopted is to utilize the continuous production process of PTFE electromechanical energy conversion functional membrane, thermal bonding of microporous membrane structure composite membrane and charging of composite membrane, wherein the thermal bonding step of the composite membrane of the microporous membrane has at least two layers of PTFE film sandwiched with a layer of porous PTFE film, which are alternately stacked and then introduced between upper and lower hot pressing rollers for hot pressing bonding to form a composite membrane; then the composite membrane is charged to obtain PTFE piezoelectric electret material.

[0037] Based on the above ideas, see Appendix Figure 1-Figure 3 As shown, an electret piezoelectric sensor device according to a preferred embodiment of the present invention comprises a polarized storage material layer 10, and electrode layers 8 arranged on both sides of the storage material layer 10; the storage material layer 10 comprises a plurality of dense PTFE material layers 5 and 7 and at least one porous PTFE material layer 6 stacked and tightly combined, the porous PTFE material layer 6 is arranged between any two adjacent dense PTFE material layers 5 and 7, and the dense PTFE material layers 5 and 7 are in direct contact with the electrode layers 8 on both sides. The electret piezoelectric sensor device also comprises a packaging layer 9 and a lead 11, the packaging layer 9 wraps the electrode layer 8 and the storage material layer 10, the lead 11 is in conductive contact with the electrode layer 8 and penetrates the packaging layer 9 to reach the outside of the packaging layer 9.

[0038] Based on the above structure, the key component of the device provided by the present invention is the storage material layer 10. The storage material layer 10 forms positive polarity space charges 2 and negative polarity space charges 4 on both sides of the gas holes 3 in the electrode basic electret 1 through polarization. The two space charges form a regionalized concentrated distribution trend due to the spacing effect of the gas holes 3. Since different PTFE material layers are combined by hot pressing, there is a pressure-sensitive layer (not shown in the figure) at the interface between the layers. The physical properties and polarization properties of the pressure-sensitive layer are significantly different from those of the material layer matrix, thereby forming a field plate effect, limiting the distribution range of the space charge in the thickness direction, making the charge more concentrated, thereby bringing about a more sensitive sensing characteristic to the volume change of the intermediate layer with holes 3; in addition, due to the barrier of the pressure-sensitive layer and the high stability of PTFE itself, the charge is not easy to lose and can remain in the device for a long time, thereby improving the stability of the device, especially in the environment of high temperature, high humidity, especially temperature and humidity alternation, its stability is more prominent.

[0039] As a typical example, the manufactured device has at least:

[0040] High temperature resistance: PTFE material itself has good high temperature resistance, and the sensor can work stably in high temperature environment. Chemical corrosion resistance: The chemical inertness of PTFE enables the sensor to maintain good performance in corrosive environment. High mechanical strength: The specially treated PTFE matrix has good mechanical strength and can withstand large mechanical stress. Stable piezoelectric performance: Through reasonable piezoelectric material selection and polarization treatment, the piezoelectric performance of the sensor is stable and the sensitivity is high.

[0041] Based on the above advantages, the device provided by the present invention is suitable for application in: Piezoelectric switch sensor: using the piezoelectric effect to generate electrical signals under mechanical stress. Used for vibration detection and impact detection. Energy harvesting sensor: using the vibration or movement in the environment, the piezoelectric layer converts mechanical energy into electrical energy, and the PTFE film can protect the piezoelectric material and improve the energy conversion efficiency. Microelectromechanical system (MEMS): In microelectromechanical systems, piezoelectric-PTFE composite materials can be used to manufacture high-precision actuators and sensors, which are suitable for precision control and detection in complex environments. Protective coating: PTFE film can be used as a protective coating for piezoelectric materials and is used in situations requiring chemical resistance and environmental resistance, such as industrial sensors and environmental monitoring equipment. Switch sensor: The combination of PTFE film and piezoelectric layer is widely used in pressure sensors, acceleration sensors and acoustic sensors. For example, in medical ultrasonic probes, PTFE film can provide protection and improve signal quality.

[0042] In addition to traditional sensor applications, the piezoelectric film can also be used in the actuator field through electrical expansion or contraction, such as acoustic wave generators and vibration generators in some micro-electromechanical systems.

[0043] Corresponding to the above device structure, an embodiment of the present invention further provides a flexible electromechanical energy conversion composite film piezoelectric sensor and a preparation method thereof, the steps are:

[0044] 1. There are at least two layers of dense PTFE film, and a layer of expanded porous PTFE is sandwiched between each adjacent two layers of PTFE film. After alternately stacked, they are introduced between upper and lower hot pressing rollers for hot pressing and bonding to form a composite film.

[0045] 2. Preparation of piezoelectric electret: magnetron sputtering a conductive metal layer on one side of the composite film surface or using conductive tape to prepare electrodes. Then negative high voltage polarization is used to generate an electric dipole moment on the surface of the material.

[0046] 3. Package the device: Package the piezoelectric composite film to protect it from environmental influences such as humidity, oxygen and physical damage. The packaging materials include PI, FEP, PP, PET, etc., depending on the application requirements of the device. Ensure the stability and reliability of the sensor in harsh environments.

[0047] 4. Fixing of the electrode lead 11: Use air nails or other methods to fix the electrode lead 11 at a specific position of the electronic device.

[0048] In the above preparation scheme, the voltage of the corona polarization treatment can be 10-15 kV, the ambient temperature is 15-35 degrees Celsius, and the temperature of the oven aging treatment after polarization is 120-150 degrees Celsius for 20-60 minutes.

[0049] In addition, in a preferred embodiment of the present invention, in order to form a pressure-sensitive layer with excellent performance, the strategy adopted is to regulate the hot pressing conditions, that is: the hot pressing treatment adopts a roller pressing method, the pressing temperature is set to 160-380°C, the pressure is 1-1.5MPa, the roller diameter is 5-10cm, and the travel speed is 0.5-1m / s. In the hot pressing conditions adopted in the present invention, the range of hot pressing temperature is relatively narrow. The hot pressing temperature of the conventional porous PTFE film is 280-300+°C, and the pressure is generally 0.1-0.5MPa. In the present invention, the low-temperature, high-pressure, and short-time hot pressing method of roller pressing is adopted, which can form a pressure-transformed layer with clear boundaries and smooth morphology. If a higher temperature is combined with a slightly lower pressure (usually such as a planar hot pressing method), the PTFE material will be deformed too much, causing the pressure-transformed layer to have mixed boundaries and uneven morphology; and if the hot pressing time is too long (usually plane hot pressing or too low a travel speed during roller pressing will cause the hot pressing time to be too long), it will also cause the interface position to be mixed and the morphology to be uneven.

[0050] The technical scheme of the present invention is further described in detail below through several embodiments and in conjunction with the accompanying drawings. However, the selected embodiments are only used to illustrate the present invention and do not limit the scope of the present invention. It should be noted that, unless otherwise specified, the materials, equipment and testing methods involved in the following embodiments are all conventional commercially available materials or commonly used methods in the art.

[0051] Example 1

[0052] This embodiment illustrates a preparation process of an electret piezoelectric sensor device and its performance test, which is specifically as follows:

[0053] 1. Two layers of dense PTFE film (with a thickness of 30 μm) are used, and a layer of expanded porous PTFE film (with a thickness of 60 μm, a porosity of 90%, and an internal average pore size of 30 μm) is sandwiched between the two layers of dense PTFE film. After stacking, they are introduced between upper and lower hot pressing rollers for hot pressing and bonding to form a composite film. The diameter of the pressing roller is 5 cm, the temperature is 380°C, the applied pressure is converted to 1.5 MPa according to the actual contact area of ​​the pressing roller-film, and the travel speed is set to 1 m / s.

[0054] 2. Preparation of piezoelectric electret: A layer of 50um thick conductive tape is attached to the surface of the composite film to form an electrode layer, and then negative high voltage polarization is used to generate an electric dipole moment on the surface of the material. The specific process is to apply a voltage of 10-15kv at room temperature, polarize for 5 minutes, and then perform oven aging treatment at a temperature of 140 degrees Celsius for 40 minutes.

[0055] 3. Package device: Use PI coating to package the device and leave leads.

[0056] 4. Fixing of electrode leads: Fix the electrode leads at specific positions of electronic devices.

[0057] The device was subjected to a sensing sensitivity test and an aging performance test, wherein the aging performance test was conducted under conditions of a temperature of 70° C. and a humidity of 80% for 24 hours.

[0058] The test result shows that there is no attenuation in the device sensitivity.

[0059] Comparative Example 1

[0060] This comparative example is substantially the same as Example 1, except that:

[0061] The porous PTFE film in the middle is replaced with a dense PTFE film of equal thickness.

[0062] The sensitivity of the obtained device is about 50% of that of the device in Example 1, and the aging resistance is comparable.

[0063] Comparative Example 2

[0064] This comparative example is substantially the same as Example 1, except that:

[0065] An integral PTFE film having a thickness equal to the total thickness of the three-layer PTFE film in Example 1 is used.

[0066] The sensitivity of the obtained device is about 20% of that of the device in Example 1, and the aging resistance is comparable.

[0067] Comparative Example 3

[0068] This comparative example is substantially the same as Example 1, except that:

[0069] The dense PTFE films on both sides were replaced with porous PTFE films of the same thickness as that in Example 1.

[0070] The sensitivity of the obtained device is about 30% of that of the device in Example 1, and the aging resistance is comparable.

[0071] Comparative Example 4

[0072] This comparative example is substantially the same as Example 1, except that:

[0073] The hot pressing was carried out in a plane hot pressing manner, with a hot pressing temperature of 280°C, a pressure of 0.3 MPa, and a time of 50 s.

[0074] The sensitivity of the obtained device is about 70% of that of the device in Example 1, and its aging resistance also decreases to a certain extent.

[0075] Example 2

[0076] This embodiment illustrates a preparation process of an electret piezoelectric sensor device and its performance test, which is specifically as follows:

[0077] 1. Two layers of dense PTFE film (with a thickness of 10 μm) are used, and a layer of expanded porous PTFE film (with a thickness of 20 μm, a porosity of 95%, and an internal average pore size of 50 μm) is sandwiched between the two layers of dense PTFE film. After stacking, the film is introduced between the upper and lower hot pressing rollers for hot pressing and bonding to form a composite film. The diameter of the pressing roller is 5 cm, the temperature is 380°C, the applied pressure is converted to 1.5 MPa according to the actual contact area between the pressing roller and the film, and the travel speed is set to 1 m / s.

[0078] 2. Preparation of piezoelectric electret: A conductive copper layer is magnetron sputtered on one side of the composite film surface to form an electrode layer, and then negative high voltage polarization is used to generate an electric dipole moment on the surface of the material. The specific process is to apply a voltage of 10-15kV at room temperature, polarize for 10 minutes, and then perform oven aging treatment at a temperature of 140 degrees Celsius for 40 minutes.

[0079] 3. Package the device: Use PET coating to package the device and leave leads.

[0080] 4. Fixing of electrode leads: Fix the electrode leads at specific positions of electronic devices.

[0081] Example 3

[0082] This embodiment illustrates a preparation process of an electret piezoelectric sensor device and its performance test, which is specifically as follows:

[0083] 1. Two layers of dense PTFE film (with a thickness of 6 μm) are used, and a layer of expanded porous PTFE film (with a thickness of 50 μm, a porosity of 80%, and an internal average pore size of 100 μm) is sandwiched between the two layers of dense PTFE film. After stacking, they are introduced between upper and lower hot pressing rollers for hot pressing and bonding to form a composite film. The diameter of the pressing roller is 5 cm, the temperature is 380°C, the applied pressure is converted to 1.5 MPa according to the actual contact area between the pressing roller and the film, and the travel speed is set to 1 m / s.

[0084] 2. Preparation of piezoelectric electret: A conductive copper layer is magnetron sputtered on one side of the composite film surface to form an electrode layer, and then negative high voltage polarization is used to generate an electric dipole moment on the surface of the material. The specific process is to apply a voltage of 10-15kV at room temperature, polarize for 5 minutes, and then perform oven aging treatment at a temperature of 140 degrees Celsius for 40 minutes.

[0085] 3. Package the device: Use PP to package the device and leave leads.

[0086] 4. Fixing of electrode leads: Fix the electrode leads at specific positions of electronic devices.

[0087] The devices obtained in the above-mentioned embodiments 2-3 still have similar high sensitivity and high aging resistance performance, which will not be described in detail here.

[0088] Based on the above embodiments and comparative examples, it can be clearly seen that the piezoelectric device provided in the embodiments of the present invention forms an optimized electric field distribution near the holes by arranging a porous PTFE material layer in the middle and dense PTFE material layers on both sides, and combines the various material layers by hot pressing, so that a pressure-dependent sublayer is generated at the bonding interface, which changes the orientation and conformation of the PTFE molecules at the interface and forms a field plate effect. Under the joint action, the sensitivity of polarized charges to pressure deformation can be increased, and the retention capacity of polarized charges can be increased to prevent loss, thereby combining the process of PTFE composite membrane with piezoelectricity to manufacture high-performance, durable and complex environment-suitable functional materials, which can work stably in harsh environments such as high temperature and high corrosion, and have broad application prospects.

[0089] The above-described embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or changes made by those skilled in the art based on the present invention are within the protection scope of the present invention. The protection scope of the present invention shall be subject to the claims.

Claims

1. An electret piezoelectric sensor device, comprising a polarized storage material layer and electrode layers arranged on both sides of the storage material layer; It is characterized in that The electricity storage material layer includes a plurality of dense PTFE material layers and at least one porous PTFE material layer which are stacked and tightly combined. The porous PTFE material layer is arranged between any two adjacent dense PTFE material layers, and the dense PTFE material layers are in direct contact with the electrode layers on both sides.

2. The electret piezoelectric sensor device according to claim 1, characterized in that: Along the stacking direction, the dense PTFE material layers and the porous PTFE material layers are arranged alternately.

3. The electret piezoelectric sensor device according to claim 1 or 2, characterized in that: The dense PTFE material layer and the porous PTFE material layer are combined by hot pressing, and a hot pressing deformation interface exists between any of the dense PTFE material layers and the porous PTFE material layer.

4. The electret piezoelectric sensor device according to claim 1, characterized in that: The porosity of the porous PTFE material layer is 20-95%, and the pore size of the internal holes ranges from 0.5 to 100 μm; And / or, the thickness of the porous PTFE material layer is 5-500 μm; And / or, the thickness of the dense PTFE material layer is 1-100 μm.

5. The electret piezoelectric sensor device according to claim 1, characterized in that: It also includes a packaging layer and a lead, wherein the packaging layer wraps the electrode layer and the power storage material layer, and the lead is in conductive contact with the electrode layer and penetrates the packaging layer to reach outside the packaging layer.

6. The electret piezoelectric sensor device according to claim 5, characterized in that: The material of the encapsulation layer includes any one of PI, FEP, PP, and PET, or a combination of two or more thereof; And / or, the electrode layer comprises metal or conductive tape.

7. The method for preparing the electret piezoelectric sensor device according to any one of claims 1 to 6, characterized in that: include: Providing multiple dense PTFE material layers and at least one porous PTFE material layer The dense PTFE material layer and the porous PTFE material layer are stacked and combined, and the porous PTFE material layer is arranged between any two adjacent dense PTFE material layers, and the two end surfaces are the dense PTFE material layers, to form a combination; Performing a hot pressing treatment on the assembly to obtain an electricity storage material layer; Covering the two end surfaces of the electricity storage material layer with electrode layers; And, a step of applying an electric field to the electricity storage material layer to perform corona poling treatment.

8. The preparation method according to claim 7, characterized in that: The method also includes covering a packaging layer on the periphery of the combined structure formed by the power storage material layer and the electrode layer, and providing leads penetrating the packaging layer.

9. The preparation method according to claim 7, characterized in that: The hot pressing treatment adopts a roller pressing method, the pressing temperature is set to 160-380° C., the pressure is 1-1.5 MPa, the roller diameter is 5-10 cm, and the travel speed is 0.5-1 m / s.

10. The preparation method according to claim 7, characterized in that: The corona polarization treatment includes a polarization process and an aging process; The voltage of the polarization process is 10-15 kV, the temperature is 15-35° C., and the time is 0.1-30 min; the temperature of the aging treatment is 120-200° C., and the time is 20-60 min.

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