A sensor / actuator based on piezoelectric composite material and a preparation method thereof

Abstract

The present invention discloses a sensor / actuator based on piezoelectric composite materials and a preparation method thereof, and relates to the technical field of functional devices and their preparation. The sensor / actuator based on piezoelectric composite materials includes a piezoelectric composite material, a positive and negative electrode assembly, and upper and lower surface protective films. The piezoelectric composite material includes an array micro-piezoelectric unit, positive and negative conductive fibers, bonding fibers, and a reinforcement frame. After packaging, positive and negative rectangular pads are connected for polarization to form an efficient functional device that can be used as both a sensor and an actuator. This functional device not only solves the problem of uneven electric field inside traditional piezoelectric composite materials, overcomes the problem of material shedding of each phase of the piezoelectric composite material during the manufacturing process, but also ensures electrical conduction between the bus circuit and the conductive fiber. The preparation method of the sensor / actuator based on piezoelectric composite materials has precise control of structural dimensions and device performance, and can realize device serialization and mass production.

Description

Technical Field

[0001] The present invention relates to the technical field of a functional device and its preparation, and in particular to a sensor / actuator based on a piezoelectric composite material and its preparation method. Background Art

[0002] As a special functional material, piezoelectric ceramics can sense external stress fields through the positive piezoelectric effect and release stress waves through the inverse piezoelectric effect. Since ordinary piezoelectric materials are hard and brittle and cannot be used for curved structures, some scholars and researchers at home and abroad have miniaturized piezoelectric materials and used flexible materials as skeletons to assemble piezoelectric composite materials to adapt to curved structures. Piezoelectric composites can be named according to the connectivity of each phase material. Two-phase piezoelectric composites have 10 types of connectivity, while three-phase piezoelectric composites have 20 types of connectivity. Among the two-phase piezoelectric composites, the representative ones are 0-3 type, 2-2 type and 1-3 type. Among them, the commercialized MFC (Macro fiber composites) belongs to the 1-3 type piezoelectric composite. The piezoelectric composite is formed by attaching piezoelectric fibers to the upper and lower surfaces of flexible interdigitated positive and negative electrodes. The special positive and negative electric fields formed by the positive and negative interdigitated electrodes are used to polarize the piezoelectric fibers into high-efficiency functional materials with d33 characteristics with opposite polarization directions, thereby effectively exerting the longitudinal strain performance of the piezoelectric fibers and making the MFC have high-efficiency output characteristics.

[0003] At present, the piezoelectric fibers in the commercial 1-3 type MFC structure based on the d33 characteristic are continuous long strips. Due to the special structure of the interdigital electrodes on the upper and lower surfaces, the internal electric field in the entire piezoelectric fiber is unevenly distributed. The electric field inside the piezoelectric fiber directly below the interdigital electrodes is zero, and then gradually increases, resulting in a large alternating value of the electric field inside the piezoelectric fiber, which is prone to concentrated stress, causing fatigue damage, and affecting the conversion efficiency and service life of the device. In recent years, some scholars and researchers have proposed cutting the continuous long strip piezoelectric fibers into small segments, embedding electrode materials in the middle to make a new type of 1-2-3 piezoelectric material with three-phase material to solve the problem of uneven electric field. Among them, the invention patent with publication number CN107565013A discloses a longitudinal gradient short fiber piezoelectric composite material and its preparation method, including a forked electrode and a piezoelectric fiber composite layer located between the upper and lower electrodes of the forked electrode, the piezoelectric fiber composite layer is made of polarized short fibers stacked and pressed, it is difficult to ensure that the positive and negative electrode surfaces of the piezoelectric composite material are completely overlapped during the manufacturing process, and it is also difficult to ensure the consistency of the spacing between the short fibers, and the piezoelectric fiber composite material is easy to fall off during the slicing and grinding process. At the same time, the upper and lower surface forked electrodes and the surface electrodes are also difficult to align their corresponding positions, and the yield rate is very low. Similarly, the invention patent with publication number CN108417707A discloses a preparation method and piezoelectric composite material of a piezoelectric composite material, which adopts positive and negative cutting and filling of polymer phases. In the process of grinding the thickness of the piezoelectric composite material, the method also has the problem that the materials of each phase are easy to fall off, and the yield rate is not high in actual operation. Therefore, in the preparation process of piezoelectric composite materials and devices, how to solve the problem of preventing the various phase materials from falling off during the grinding of the thickness of the piezoelectric composite materials and ensuring that the positions of the interdigitated electrodes and the conductive surface electrodes correspond to each other has become a difficult problem that needs to be solved urgently. Summary of the invention

[0004] The purpose of the present invention is to provide a sensor / actuator based on a piezoelectric composite material, aiming to improve the problem of uneven electric field in the existing piezoelectric composite material using a d33 characteristic structure, and at the same time solve the problem of the shedding of various phases of the functional material constituting the sensor / actuator, namely the piezoelectric composite material, during the grinding process, thereby improving the yield of the finished product, preferably piezoelectric ceramic functional materials with high d33 and g33 values, and ultimately making the device a functional device for both sensing and excitation.

[0005] Another object of the present invention is to provide a method for preparing a sensor / actuator based on piezoelectric composite materials, which adopts the method of filling the middle with conductive fibers to solve the problem of uneven electric field in the array micro-piezoelectric unit, the method of adding a frame on the periphery to solve the problem of material shedding of each phase during grinding, and the method of etching and sputtering circuits on the reinforcement frame to solve the problem of electrical conduction between the bus circuit and the conductive fibers.

[0006] The present invention solves the above technical problem by adopting the following technical solutions.

[0007] The present invention proposes a sensor / actuator based on a piezoelectric composite material, comprising a piezoelectric composite material, a positive electrode assembly, a negative electrode assembly, an upper surface protective film and a lower surface protective film; the piezoelectric composite material comprises a plurality of array micro-piezoelectric units with consistent lateral and longitudinal spacings, a plurality of bonding fibers having a length consistent with the longitudinal length of the array micro-piezoelectric units are arranged between the lateral spacings of the array micro-piezoelectric units, a plurality of positive conductive fibers and negative conductive fibers alternating between positive and negative are arranged between the longitudinal spacings of the array micro-piezoelectric units and the bonding fibers, and a reinforcement frame is arranged around the array micro-piezoelectric units; a positive rectangular pad is provided at the end of the positive electrode assembly circuit; a negative rectangular pad is provided at the end of the negative electrode assembly circuit; and the upper surface protective film is provided with exposed notches at the negative rectangular pad and the positive rectangular pad.

[0008] Preferably, the positive electrode assembly is a silver or gold sputtered circuit, each circuit branch is completely bonded to the positive conductive fiber contact surface corresponding to its position, and charges can move without resistance. The positive electrode assembly is completely bonded to the reinforcement frame and the bonding fiber contact surface, and the three are insulated and there is no charge movement.

[0009] Preferably, the negative electrode assembly is a silver or gold sputtered circuit, each circuit branch is completely bonded to the negative conductive fiber contact surface corresponding to its position, and charges can move without resistance. The negative electrode assembly is completely bonded to the reinforcement frame and the bonding fiber contact surface, and the three are insulated and there is no charge movement.

[0010] Preferably, the upper surface protection film and the lower surface protection film are polyimide insulating coatings, which are completely bonded to the upper and lower surfaces of the piezoelectric composite material respectively.

[0011] Preferably, the array micro-piezoelectric unit is made of piezoelectric ceramic material with high d33 and g33 values, and its polarization direction is from the positive conductive fiber to the negative conductive fiber in the longitudinal direction, and has a relatively high positive piezoelectric effect and inverse piezoelectric effect in its polarization direction.

[0012] Preferably, the bonding fiber material is flexible epoxy resin, which is seamlessly bonded to the contact surface of the array micro-piezoelectric unit; the positive conductive fiber and the negative conductive fiber are made of thermosetting conductive silver glue, which has a hardness equivalent to that of piezoelectric ceramics after curing, has a non-resistance conductive function, and is seamlessly bonded to the contact surface of the array micro-piezoelectric unit; the reinforcement frame is made of flexible epoxy resin, which is seamlessly bonded to each contact surface and locked in the frame.

[0013] Preferably, the overall structure of the piezoelectric composite sensor / actuator has greater lateral flexibility and certain longitudinal flexibility.

[0014] The present invention also proposes a method for preparing a sensor / actuator based on a piezoelectric composite material, comprising the following steps:

[0015] The whole piezoelectric ceramic is cut into thin slices, a plurality of bonding fiber grooves are cut horizontally and equidistantly on the surface of the thin piezoelectric ceramic, and flexible epoxy resin is filled in the grooves; after curing, a plurality of conductive fiber grooves are cut longitudinally and equidistantly on the surface of the thin piezoelectric ceramic, and thermosetting conductive silver glue is filled in the grooves; after curing, flexible epoxy resin is filled on the periphery of the thin piezoelectric ceramic, and a reinforcement frame is formed after curing; the upper and lower surfaces of the whole are ground to remove the non-penetrating piezoelectric ceramic layer and grind to the required thickness.

[0016] The positive and negative electrode assembly patterns are etched to the required depth on the upper surface of the reinforcement frame and part of the positive and negative conductive fibers, and the positive and negative electrode assemblies of equal thickness are formed on the etched patterns by plasma sputtering to cover the positive and negative rectangular pads, and a polyimide insulating protective layer of equal thickness is applied to the upper and lower surfaces.

[0017] According to the longitudinal unit length L (mm) of the array piezoelectric unit, the voltage calculation formula V=2000×L (V) is used to load the polarization voltage on the positive and negative rectangular pads. The array piezoelectric unit is polarized by maintaining the voltage for 20 minutes to form a sensor / actuator based on piezoelectric composite materials.

[0018] Preferably, the longitudinal unit length L of the array piezoelectric unit can be adaptively calculated based on the wavelength of the sensing / excitation signal, and the bonding fiber groove width can be adaptively calculated based on the flexibility in the transverse direction.

[0019] Preferably, the thickness of the piezoelectric composite material may be 0.1-1 mm; the thickness of the upper and lower surface protective films may be 0.01-0.05 mm.

[0020] The embodiment of the present invention provides a sensor / actuator based on a piezoelectric composite material and a preparation method thereof. The beneficial effects are as follows: the sensor / actuator provided by the present invention is composed of a piezoelectric composite material, a positive electrode assembly, a negative electrode assembly, an upper surface protective film and a lower surface protective film; the piezoelectric composite material includes an array of micro-piezoelectric units, transverse bonding fibers, longitudinally positive and negative alternating positive and negative conductive fibers and negative conductive fibers, and a reinforcement frame; this structure not only solves the problem of uneven electric field inside the piezoelectric ceramic functional material and improves the service life of the device, but also overcomes the defect that each phase material is easy to fall off during the grinding process. The present invention also provides a preparation method for a sensor / actuator based on a piezoelectric composite material, which has a simple and easy process, solves the problem of electrical conduction between the positive and negative bus circuits and the conductive fibers in the structure, and is relatively easy to realize the serialized and batch preparation of sensors / actuators based on piezoelectric composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions combined with the prior art, the drawings required for the implementation methods are briefly introduced below. It should be pointed out that the following drawings only reflect certain implementation methods of the present invention and therefore should not be defined as limiting the scope. A person skilled in the art can expand more relevant drawings based on the drawings without paying any creative work.

[0022] Figure 1 The structure of the sensor / actuator based on piezoelectric composite material of the present invention is schematically shown. Figure 1 .

[0023] Figure 2 The structure of the sensor / actuator based on piezoelectric composite material of the present invention is schematically shown. Figure 2 .

[0024] Figure 3 The present invention is a process flow chart for preparing a sensor / actuator based on a piezoelectric composite material.

[0025] In the figure, 1-upper surface protection film, 2-positive electrode assembly, 3-negative electrode assembly, 4-piezoelectric composite material, 5-lower surface protection film, 201-positive rectangular pad, 301-negative rectangular pad, 401-array micro-piezoelectric unit, 402-positive conductive fiber, 403-negative conductive fiber, 404-bonding fiber, 405-reinforcement frame. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present invention more clear and explicit compared with the prior art, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments. 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 relevant technical personnel in the field without making creative work should fall within the scope of protection of the present invention.

[0027] The following is a detailed description of the sensor / actuator based on the piezoelectric composite material and the preparation method thereof provided in the embodiment of the present invention.

[0028] Please refer to Figure 1 and Figure 2A sensor / actuator based on a piezoelectric composite material provided by an embodiment of the present invention comprises a piezoelectric composite material 4, a positive electrode assembly 2, a negative electrode assembly 3, an upper surface protective film 1 and a lower surface protective film 5; the piezoelectric composite material 4 comprises a plurality of array micro-piezoelectric units 401 with the same lateral spacing and longitudinal spacing, a plurality of bonding fibers 404 having the same length as the longitudinal length of the array micro-piezoelectric units 401 are arranged between the lateral spacing of the array micro-piezoelectric units 401, a plurality of positive conductive fibers 402 and negative conductive fibers 403 alternating between positive and negative are arranged between the longitudinal spacing of the array micro-piezoelectric units 401 and the bonding fibers 404, and a reinforcement frame 405 is arranged around the array micro-piezoelectric units 401; a positive rectangular pad 201 is provided at the circuit end of the positive electrode assembly 2; a negative rectangular pad 301 is provided at the circuit end of the negative electrode assembly 3; and the upper surface protective film 1 is provided with exposed notches at the positive rectangular pad 201 and the negative rectangular pad 301.

[0029] It should be noted that in the sensor / actuator based on piezoelectric composite material provided by the embodiment of the present invention, in the piezoelectric composite material 4, the positive conductive fibers 402 and the negative conductive fibers 403 are parallel to each other, and the electric field formed between them is a uniform electric field, that is, the electric field in the array micro-piezoelectric unit 401 is uniform, which greatly improves the functional utilization rate of the array micro-piezoelectric unit.

[0030] Specifically, the positive electrode assembly 2 and the negative electrode assembly 3 are silver or gold sputtering circuits, and the contact surfaces of the positive conductive fibers 402 and the negative conductive fibers 403 corresponding to their positions of each circuit branch are completely bonded, and charges can move without resistance. The positive electrode assembly 2 and the negative electrode assembly 3 are completely bonded to the contact surfaces of the reinforcement frame 405 and the bonding fiber 404, and the three are insulated and there is no charge movement; the bonding fiber 404 is made of flexible epoxy resin and is seamlessly bonded to the contact surface of the array micro-piezoelectric unit 401; the positive conductive fibers 402 and the negative conductive fibers 403 are made of thermosetting conductive silver glue, and their hardness after curing is equivalent to that of piezoelectric ceramics, and they have a non-resistance conductive function and are seamlessly bonded to the contact surface of the array micro-piezoelectric unit 401; the reinforcement frame 405 is made of flexible epoxy resin, and is seamlessly bonded to the contact surfaces of other phases and locked in the frame; the upper surface protective film 1 and the lower surface protective film 5 are polyimide insulating coatings, which are completely bonded to the upper and lower surfaces of the piezoelectric composite material 4, respectively.

[0031] Specifically, the array micro-piezoelectric unit is made of piezoelectric ceramic material with high d33 and g33 values, and its polarization direction is from the positive conductive fiber to the negative conductive fiber in the longitudinal direction, and it has a high positive piezoelectric effect and inverse piezoelectric effect in its polarization direction.

[0032] It should be noted that the sensor / actuator based on the piezoelectric composite material provided in the embodiment of the present invention adopts micro-piezoelectric units and adhesive fiber arrays to distribute in the lateral direction, which can make the entire device have great flexibility in the lateral direction. The longitudinal direction is also distributed by micro-piezoelectric units and positive and negative conductive fiber arrays, which also has a certain flexibility; the material of the micro-piezoelectric unit is piezoelectric ceramic material with high d33 and g33 values, and the device can be used as a sensor or an actuator; the piezoelectric composite material has a reinforcement frame on the periphery, which can ensure that the materials of each phase are not easy to fall off during the device manufacturing process, thereby greatly improving the manufacturing yield.

[0033] Please refer to Figure 3 The present invention also provides a method for preparing a sensor / actuator based on a piezoelectric composite material, comprising the following steps:

[0034] S1. Preparation of piezoelectric composite material 4: Cut a whole piece of piezoelectric ceramic ① into thin ceramic slices ②, cut a plurality of bonding fiber grooves ③ on the surface of the thin piezoelectric ceramic ② at equal intervals in the horizontal direction without penetrating, and fill the grooves with flexible epoxy resin ④; after solidification, cut a plurality of conductive fiber grooves ⑤ on the surface of the thin piezoelectric ceramic at equal intervals in the vertical direction without penetrating, and fill the grooves with thermosetting conductive silver glue ⑥; after solidification, fill the outer periphery of the thin piezoelectric ceramic with flexible epoxy resin, and form a reinforcement frame after solidification ⑦; grind the upper and lower surfaces of the whole to remove the non-penetrating piezoelectric ceramic layer, and grind to the required thickness ⑧.

[0035] S2. Preparation of positive electrode assembly 2 and negative electrode assembly 3: Etch the positive and negative electrode assembly patterns to the required depth ⑨ on the upper surface of the reinforcement frame and part of the positive and negative conductive fibers, and use plasma sputtering to form positive and negative electrode assemblies of equal thickness ⑩ on the etched patterns.

[0036] S3, device packaging: cover the positive rectangular pad 201 and the negative rectangular pad 301, and apply a polyimide insulating protective layer ⑪ with equal thickness on the upper and lower surfaces of the piezoelectric composite material 4.

[0037] S4. Device polarization: According to the longitudinal unit length L (mm) of the array piezoelectric unit 401, the voltage calculation formula V=2000×L (V) is used to load the polarization voltage on the positive rectangular pad 201 and the negative rectangular pad 301. The array piezoelectric unit 401 is polarized by maintaining the voltage for 20 minutes to form a sensor / actuator based on a piezoelectric composite material ⑫.

[0038] Specifically, the longitudinal unit length L of the array piezoelectric unit 401 can be adaptively calculated based on the wavelength of the sensing / excitation signal, and the groove width of the bonding fiber 404 can be adaptively calculated based on the flexibility in the transverse direction.

[0039] Specifically, the thickness of the piezoelectric composite material 4 can be 0.1-1 mm; the thickness of the upper surface protection film 1 and the lower surface protection film 5 can be 0.01-0.05 mm.

[0040] It should be noted that the method for preparing a sensor / actuator based on a piezoelectric composite material provided in an embodiment of the present invention and the method for preparing the positive and negative electrode assemblies are prepared by etching and sputtering. The process method is precise and solves the problem of structural electrical conduction between the positive and negative bus circuits and all the positive and negative conductive fibers, thereby ensuring the yield of the device during the preparation process.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, relevant technical personnel in the field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalent or similar ones, without making the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sensor / actuator based on a piezoelectric composite material, characterized in that: It comprises a piezoelectric composite material, a positive electrode assembly, a negative electrode assembly, an upper surface protective film and a lower surface protective film; the piezoelectric composite material comprises a plurality of array micro-piezoelectric units with the same lateral spacing and longitudinal spacing, a plurality of bonding fibers with the same length as the longitudinal length of the array micro-voltage units are arranged between the lateral spacing of the array micro-piezoelectric units, a plurality of positive conductive fibers and negative conductive fibers alternating between positive and negative are arranged between the longitudinal spacing of the array micro-piezoelectric units and the bonding fibers, and a reinforcement frame is arranged around the array micro-piezoelectric units; a positive rectangular pad is provided at the circuit end of the positive electrode assembly; a negative rectangular pad is provided at the circuit end of the negative electrode assembly; and the upper surface protective film is provided with exposed notches at the negative rectangular pad and the positive rectangular pad; The positive electrode assembly is a silver or gold sputtering circuit, each circuit branch is completely bonded to the positive conductive fiber contact surface corresponding to its position, and the charge can move without resistance. The positive electrode assembly is completely bonded to the reinforcement frame and the bonding fiber contact surface, and the three are insulated and there is no charge movement. The negative electrode assembly is a silver or gold sputtering circuit, each circuit branch is completely bonded to the negative conductive fiber contact surface corresponding to its position, and the charge can move without resistance. The negative electrode assembly is completely bonded to the reinforcement frame and the bonding fiber contact surface, and the three are insulated and there is no charge movement. The upper surface protective film and the lower surface protective film are polyimide insulating coatings, which are completely bonded to the upper and lower surfaces of the piezoelectric composite material respectively; The array micro-piezoelectric unit is made of piezoelectric ceramic material with high d33 and g33 values, and its polarization direction is that the positive conductive fiber points to the negative conductive fiber in the longitudinal direction, and has a high positive piezoelectric effect and inverse piezoelectric effect in its polarization direction; The bonding fiber is made of flexible epoxy resin, and is seamlessly bonded to the contact surface of the array micro-piezoelectric unit; the positive conductive fiber and the negative conductive fiber are made of thermosetting conductive silver glue, which has a hardness equivalent to that of piezoelectric ceramics after curing, has a non-resistance conductive function, and is seamlessly bonded to the contact surface of the array micro-piezoelectric unit; the reinforcement frame is made of flexible epoxy resin, and is seamlessly bonded to each contact surface and locked in the frame.

2. The sensor / actuator based on piezoelectric composite material according to claim 1, characterized in that: The overall structure of the piezoelectric composite sensor / actuator has greater lateral flexibility and certain longitudinal flexibility.

3. A method for preparing a sensor / actuator based on a piezoelectric composite material, applied to the sensor / actuator based on a piezoelectric composite material according to any one of claims 1 to 2, characterized in that: The following steps are involved: Cut the whole piezoelectric ceramic into thin slices, cut a plurality of bonding fiber grooves in a non-penetrating manner and at equal intervals on the surface of the thin piezoelectric ceramic, and fill the grooves with flexible epoxy resin; After solidification, a plurality of conductive fiber grooves are cut longitudinally and non-penetratingly at equal intervals on the surface of the thin piezoelectric ceramic, and thermosetting conductive silver glue is filled in the grooves; After solidification, a flexible epoxy resin is filled around the thin piezoelectric ceramic to form a reinforcement frame after solidification; The entire upper and lower surfaces are ground to remove the non-penetrating piezoelectric ceramic layer and ground to the required thickness; Etch the positive and negative electrode assembly patterns to the required depth on the upper surface of the reinforcement frame and part of the positive and negative conductive fibers, use plasma sputtering to form positive and negative electrode assemblies of equal thickness on the etched patterns, cover the positive and negative rectangular pads, and apply a polyimide insulating protective layer of equal thickness on the upper and lower surfaces; According to the longitudinal unit length L (mm) of the array piezoelectric unit, the voltage calculation formula V=2000×L (V) is used to load the polarization voltage on the positive and negative rectangular pads. The array piezoelectric unit is polarized by maintaining the voltage for 20 minutes to form a sensor / actuator based on piezoelectric composite materials.

4. The method for preparing a sensor / actuator based on a piezoelectric composite material according to claim 3, characterized in that: The longitudinal unit length L of the array piezoelectric unit can be adaptively calculated based on the wavelength of the sensing / excitation signal, and the bonding fiber groove width can be adaptively calculated based on the flexibility in the transverse direction.

5. The method for preparing a sensor / actuator based on a piezoelectric composite material according to claim 3, characterized in that: The thickness of the piezoelectric composite material is 0.1-1 mm; the thickness of the protective films on the upper and lower surfaces is 0.01-0.05 mm.

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