CN108515694B - A flexible pressure sensor chip based on 3D printing technology and its manufacturing method - Google Patents

Abstract

A chip of a flexible pressure sensor based on 3D printing technology and a manufacturing method thereof are disclosed, wherein the chip comprises a flexible upper polar plate, the flexible upper polar plate is contacted with a flexible lower polar plate which is uniformly distributed with a miniature pyramid array, flexible film electrodes are manufactured on the contact surfaces of the flexible upper polar plate and the flexible lower polar plate, and the flexible film electrodes on the flexible upper polar plate and the flexible lower polar plate are respectively connected with an external circuit through leads; the manufacturing method comprises the steps of 3D printing flexible upper and lower polar plates, and cleaning; then adopting conductive adhesive to closely adhere the conducting wire on the flexible upper and lower polar plates, and curing; then, carrying out oxygen plasma treatment on the flexible upper and lower electrode plates, soaking a layer of PEDOT (PSS) solution, and baking to finish the manufacture of the flexible film electrode; finally, the flexible upper polar plate and the flexible lower polar plate are stuck together by using a polyimide insulating tape, and a gap between the side surfaces of the flexible upper polar plate and the flexible lower polar plate is sealed; the invention has the advantages of low processing cost, short processing period, simple and convenient manufacture, diversified material selection, integrated structure and the like.

Description

Translated fromChinese

一种基于3D打印技术的柔性压力传感器芯片及其制作方法A flexible pressure sensor chip based on 3D printing technology and its manufacturing method

技术领域technical field

本发明属于增材制造以及传感器技术领域，具体涉及一种基于3D打印技术的柔性压力传感器芯片及其制作方法。The invention belongs to the field of additive manufacturing and sensor technology, and particularly relates to a flexible pressure sensor chip based on 3D printing technology and a manufacturing method thereof.

背景技术Background technique

3D打印属于增材制造技术，是一种在计算机控制下逐层将液体固化或粉末颗粒熔合在一起，实现构造三维物体的技术。近几年，其在建筑、汽车、航空航天、医学等领域零部件的制作上得到了越来越广泛地商业化应用。3D打印应用的材料主要有金属、陶瓷、复合材料、高分子材料等等。传统的传感器制造技术，以MEMS工艺为例，存在难以加工真三维自由形状的结构、难以利用性能优异的复合功能材料、加工工艺复杂，加工效率低下，成本高等缺点。3D printing belongs to additive manufacturing technology, which is a technology that solidifies liquid or powder particles together layer by layer under computer control to realize the construction of three-dimensional objects. In recent years, it has been more and more widely commercialized in the production of parts and components in the fields of construction, automobiles, aerospace, and medicine. The materials used in 3D printing mainly include metals, ceramics, composite materials, polymer materials and so on. The traditional sensor manufacturing technology, taking the MEMS process as an example, has the disadvantages of difficult to process true three-dimensional free-form structures, difficult to use composite functional materials with excellent performance, complex processing technology, low processing efficiency, and high cost.

发明内容SUMMARY OF THE INVENTION

为了克服上述现有技术的缺陷，本发明的目的在于提供一种基于3D打印技术的柔性压力传感器芯片及其制作方法，具有加工成本低、加工周期短、制作简便、材料选择多样化、结构一体化等优点，可用于不规则物体表面如机器人，医学等领域的压力测量。In order to overcome the above-mentioned defects of the prior art, the purpose of the present invention is to provide a flexible pressure sensor chip based on 3D printing technology and a manufacturing method thereof, which has the advantages of low processing cost, short processing cycle, simple manufacturing, diversified material selection, and integrated structure. It can be used for pressure measurement on irregular surfaces such as robotics, medicine and other fields.

为了实现上述目的，本发明采用的技术方案为：In order to achieve the above object, the technical scheme adopted in the present invention is:

一种基于3D打印技术的柔性压力传感器芯片，包括柔性上极板1，柔性上极板1和均匀分布微型金字塔阵列3的柔性下极板2相接触，在柔性上极板1和柔性下极板2接触表面制作柔性薄膜电极4，柔性上极板1上的柔性薄膜电极4和柔性下极板2上的柔性薄膜电极4通过导线与外部电路相连接，导线位于柔性上极板1和柔性下极板2对应的角上设有的通孔5内。A flexible pressure sensor chip based on 3D printing technology, including a flexibleupper plate 1, a flexibleupper plate 1 and a flexiblelower plate 2 of a uniformly distributedmicro pyramid array 3 are in contact, and the flexibleupper plate 1 and the flexible lower plate are in contact. The contact surface of theboard 2 is made of aflexible film electrode 4, and theflexible film electrode 4 on the flexibleupper plate 1 and theflexible film electrode 4 on the flexiblelower plate 2 are connected to the external circuit through wires, and the wires are located between the flexibleupper plate 1 and the flexible The throughholes 5 are provided on the corresponding corners of thelower pole plate 2 .

所述的柔性上极板1和柔性下极板2由光敏柔性聚氨酯树脂材料制成。The flexibleupper electrode plate 1 and the flexiblelower electrode plate 2 are made of photosensitive flexible polyurethane resin material.

所述的柔性薄膜电极4由柔性导电聚合物PEDOT:PSS[聚(3,4-亚乙二氧基噻吩)-聚(苯乙烯磺酸)]制成。The flexiblethin film electrode 4 is made of flexible conductive polymer PEDOT:PSS [poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid)].

一种基于3D打印技术的柔性压力传感器芯片的制作方法，包括以下步骤：A manufacturing method of a flexible pressure sensor chip based on 3D printing technology, comprising the following steps:

1)运用DLP 3D打印机固化处于液态的光敏柔性聚氨酯树脂材料形成预定尺寸的柔性上极板1和均匀分布微型金字塔阵列3的柔性下极板2，柔性上极板1、柔性下极板2对应的角上预留通孔5；1) Use a DLP 3D printer to cure the photosensitive flexible polyurethane resin material in liquid state to form a flexibleupper plate 1 of a predetermined size and a flexiblelower plate 2 with uniformly distributedmicro-pyramid arrays 3. The flexibleupper plate 1 and the flexiblelower plate 2 correspond to Reserve throughholes 5 on the corners;

2)加工好的柔性上极板1和柔性下极板2依次置于清洗液、酒精中各超声清洗处理5min；取出柔性上极板1和柔性下极板2后置于紫外灯箱中20min使其完全固化；2) The processed flexibleupper plate 1 and flexiblelower plate 2 are placed in cleaning solution and alcohol for ultrasonic cleaning treatment for 5 minutes in turn; take out the flexibleupper plate 1 and the flexiblelower plate 2 and place them in a UV light box for 20 minutes. its fully cured;

3)将两根导线分别穿过柔性上极板1和柔性下极板2上预留的通孔5，并采用导电胶将导线紧密的黏附在柔性上极板1、柔性下极板2上，置于强制对流烘箱中，100℃烘烤10分钟使导电胶完全固化，取出后自然冷却至室温；3) Pass the two wires through the throughholes 5 reserved on the flexibleupper plate 1 and the flexiblelower plate 2 respectively, and use conductive glue to tightly adhere the wires on the flexibleupper plate 1 and the flexiblelower plate 2 , placed in a forced convection oven, baked at 100°C for 10 minutes to completely solidify the conductive adhesive, and cooled to room temperature after taking it out;

4)将与导线相连接的柔性上极板1、柔性下极板2置于等离子处理机中进行氧等离子体处理，处理时间90s；4) Place the flexibleupper electrode plate 1 and the flexiblelower electrode plate 2 connected with the wires in a plasma processor for oxygen plasma treatment, and the treatment time is 90s;

5)将经过氧等离子体处理的柔性上极板1、柔性下极板2置于液态导电聚合物溶液PEDOT:PSS中，使柔性上极板1、柔性下极板2表面完全浸润一层PEDOT:PSS溶液；5) Place the flexibleupper electrode plate 1 and the flexiblelower electrode plate 2 treated with oxygen plasma in the liquid conductive polymer solution PEDOT:PSS, so that the surfaces of the flexibleupper electrode plate 1 and the flexiblelower electrode plate 2 are completely infiltrated with a layer of PEDOT : PSS solution;

6)取出表面浸润了PEDOT:PSS溶液的柔性上极板1、柔性下极板2，置于强制对流烘箱中，100℃烘烤15min，取出后自然冷却至室温，完成柔性薄膜电极4的制作；6) Take out the flexibleupper electrode plate 1 and the flexiblelower electrode plate 2 whose surfaces have been soaked with PEDOT:PSS solution, place them in a forced convection oven, bake at 100° C. for 15 minutes, take out and naturally cool to room temperature, and complete the production of flexiblethin film electrodes 4 ;

7)使用聚酰亚胺绝缘胶带将柔性上极板1、柔性下极板2粘贴在一起，同时封闭柔性上极板1、柔性下极板2侧面间隙。7) Use polyimide insulating tape to stick the flexibleupper electrode plate 1 and the flexiblelower electrode plate 2 together, and close the side gaps of the flexibleupper electrode plate 1 and the flexiblelower electrode plate 2 at the same time.

本发明的有益效果为：The beneficial effects of the present invention are:

采用3D打印工艺(光固化成型)为制作方法，将柔性压阻材料PEDOT:PSS和柔性树脂相结合，拓展了传统传感器的材料选择范围。采用的光固化成型的3D打印工艺，具有较高的精度，可以制作复杂形状的微型结构，具有加工成本低、加工周期短、制作简便、材料选择多样化、结构一体化等优点。本发明的力传感器可应用在压力测量领域。Using 3D printing process (light curing molding) as the manufacturing method, the flexible piezoresistive material PEDOT:PSS and flexible resin are combined to expand the material selection range of traditional sensors. The photo-curing 3D printing process adopted has high precision and can produce micro-structures with complex shapes. It has the advantages of low processing cost, short processing cycle, simple production, diversified material selection, and structural integration. The force sensor of the present invention can be applied in the field of pressure measurement.

附图说明Description of drawings

图1为本发明柔性压力传感器芯片的结构示意图。FIG. 1 is a schematic structural diagram of a flexible pressure sensor chip of the present invention.

图2为本发明柔性压力传感器芯片的截面电阻模型示意图。FIG. 2 is a schematic diagram of a cross-sectional resistance model of the flexible pressure sensor chip of the present invention.

图3为本发明柔性压力传感器芯片的一种惠斯通测量电桥示意图。FIG. 3 is a schematic diagram of a Wheatstone measurement bridge of the flexible pressure sensor chip of the present invention.

具体实施方式Detailed ways

下面结合附图对本发明做详细描述。The present invention will be described in detail below with reference to the accompanying drawings.

如图1和图2所示，一种基于3D打印技术的柔性压力传感器芯片，包括柔性上极板1，柔性上极板1和均匀分布微型金字塔阵列3的柔性下极板2相接触，在柔性上极板1和柔性下极板2接触表面制作柔性薄膜电极4，柔性上极板1上的柔性薄膜电极4和柔性下极板2上的柔性薄膜电极4通过导线与外部电路连接，导线位于柔性上极板1和柔性下极板2对应的角上设有的通孔5内。As shown in Figures 1 and 2, a flexible pressure sensor chip based on 3D printing technology includes a flexibleupper plate 1, the flexibleupper plate 1 and the flexiblelower plate 2 of the uniformly distributedmicro pyramid array 3 are in contact. The contact surface of the flexibleupper plate 1 and the flexiblelower plate 2 is made into aflexible film electrode 4, and theflexible film electrode 4 on the flexibleupper plate 1 and theflexible film electrode 4 on the flexiblelower plate 2 are connected to the external circuit through wires. It is located in thethrough hole 5 provided on the corresponding corner of the flexibleupper electrode plate 1 and the flexiblelower electrode plate 2 .

所述的柔性上极板1和柔性下极板2由光敏柔性聚氨酯树脂材料制成。The flexibleupper electrode plate 1 and the flexiblelower electrode plate 2 are made of photosensitive flexible polyurethane resin material.

所述的柔性薄膜电极4由柔性导电聚合物PEDOT:PSS[聚(3,4-亚乙二氧基噻吩)-聚(苯乙烯磺酸)]制成。The flexiblethin film electrode 4 is made of flexible conductive polymer PEDOT:PSS [poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid)].

一种基于3D打印技术的柔性压力传感器芯片的制作方法，包括以下步骤：A manufacturing method of a flexible pressure sensor chip based on 3D printing technology, comprising the following steps:

1)运用DLP 3D打印机固化处于液态的光敏柔性聚氨酯树脂材料形成预定尺寸的柔性上极板1和均匀分布微型金字塔阵列3的柔性下极板2，柔性上极板1、柔性下极板2对应的角上预留通孔5；1) Use a DLP 3D printer to cure the photosensitive flexible polyurethane resin material in liquid state to form a flexibleupper plate 1 of a predetermined size and a flexiblelower plate 2 with uniformly distributedmicro-pyramid arrays 3. The flexibleupper plate 1 and the flexiblelower plate 2 correspond to Reserve throughholes 5 on the corners;

2)加工好的柔性上极板1和柔性下极板2依次置于清洗液、酒精中各超声清洗处理5min以去除表面杂质及污染物；取出柔性上极板1和柔性下极板2后置于紫外灯箱中20min使其完全固化；2) The processed flexibleupper plate 1 and flexiblelower plate 2 are placed in cleaning solution and alcohol for ultrasonic cleaning for 5 minutes each to remove surface impurities and contaminants; after taking out the flexibleupper plate 1 and the flexiblelower plate 2 Put it in the UV light box for 20min to make it fully cured;

3)将两根导线分别穿过柔性上极板1和柔性下极板2上预留的通孔5，并采用导电胶将导线紧密的黏附在柔性上极板1、柔性下极板2上，置于强制对流烘箱中，100℃烘烤10分钟使导电胶完全固化，取出后自然冷却至室温；3) Pass the two wires through the throughholes 5 reserved on the flexibleupper plate 1 and the flexiblelower plate 2 respectively, and use conductive glue to tightly adhere the wires on the flexibleupper plate 1 and the flexiblelower plate 2 , placed in a forced convection oven, baked at 100°C for 10 minutes to completely solidify the conductive adhesive, and cooled to room temperature after taking it out;

4)将与导线相连接的柔性上极板1、柔性下极板2置于等离子处理机中进行氧等离子体处理，处理时间90s，增加柔性上极板1、柔性下极板2的亲水性，更加容易浸润液体；4) Place the flexibleupper plate 1 and the flexiblelower plate 2 connected to the wires in a plasma processor for oxygen plasma treatment, and the treatment time is 90s to increase the hydrophilicity of the flexibleupper plate 1 and the flexiblelower plate 2. sex, easier to wet the liquid;

5)将经过氧等离子体处理的柔性上极板1、柔性下极板2置于液态导电聚合物溶液PEDOT:PSS中30s，使柔性上极板1、柔性下极板2表面完全浸润一层PEDOT:PSS溶液，尽量保证浸润的均匀度与一致性；5) Place the flexibleupper electrode plate 1 and the flexiblelower electrode plate 2 after the oxygen plasma treatment in the liquid conductive polymer solution PEDOT:PSS for 30s, so that the surface of the flexibleupper electrode plate 1 and the flexiblelower electrode plate 2 is completely infiltrated with a layer of PEDOT:PSS solution, try to ensure the uniformity and consistency of infiltration;

6)取出表面浸润了PEDOT:PSS溶液的柔性上极板1、柔性下极板2，置于强制对流烘箱中，100℃烘烤15min，取出后自然冷却至室温，完成柔性薄膜电极4的制作；6) Take out the flexibleupper plate 1 and the flexiblelower plate 2 whose surfaces have been soaked with PEDOT:PSS solution, place them in a forced convection oven, bake at 100° C. for 15 minutes, and then naturally cool to room temperature after taking out, to complete the production of flexiblethin film electrodes 4 ;

7)使用聚酰亚胺绝缘胶带将柔性上极板1、柔性下极板2粘贴在一起，同时封闭柔性上极板1、柔性下极板2侧面间隙，避免柔性薄膜电极4受空气湿度影响其压阻特性稳定性。7) Use polyimide insulating tape to stick the flexibleupper plate 1 and the flexiblelower plate 2 together, and at the same time close the side gap of the flexibleupper plate 1 and the flexiblelower plate 2 to prevent theflexible film electrode 4 from being affected by air humidity Its piezoresistive characteristics are stable.

本发明柔性力传感器芯片的工作原理为：The working principle of the flexible force sensor chip of the present invention is as follows:

如图2所示，一个微型金字塔处的电阻模型，当某一均布载荷F作用于传感器柔性上极板1上表面时，微型金字塔阵列3受压力作用产生形变，从而改变柔性上极板1、柔性下极板2表面的柔性薄膜电极4的接触面积，即柔性上极板1、柔性下极板2间的总电阻R发生变化，总电阻R由上极板电阻R_t，上下极板接触电阻R_c，以及下极板电阻R_b组成，即As shown in Figure 2, a resistance model at a micro pyramid, when a uniform load F acts on the upper surface of the flexibleupper plate 1 of the sensor, themicro pyramid array 3 is deformed by the pressure, thereby changing the flexibleupper plate 1 , the contact area of theflexible film electrode 4 on the surface of the flexiblelower plate 2, that is, the total resistance R between the flexibleupper plate 1 and the flexiblelower plate 2 changes, and the total resistance R is determined by the upper plate resistance R_t , the upper and lower plates The contact resistance R_c and the lower plate resistance R_b are composed, namely

R＝R_t+R_c+R_bR=R_t +R_c +R_b

当柔性上极板1、柔性下极板2间距发生变化时，When the distance between the flexibleupper plate 1 and the flexiblelower plate 2 changes,

ΔR＝R-R₀＝(R_t+R_c+R_b)-(R_t0+R_c0+R_b0)ΔR=RR₀ =(R_t +R_c +R_b )-(R_t0 +R_c0 +R_b0 )

由于柔性上极板1、柔性下极板2的电阻几乎不变，上式可近似为Since the resistances of the flexibleupper plate 1 and the flexiblelower plate 2 are almost unchanged, the above formula can be approximated as

ΔR≈(R_c-R_c0)+(R_b-R_b0)ΔR≈(R_c -R_c0 )+(R_b -R_b0 )

根据电阻定律According to the law of resistance

其中ρ：导体材料的电阻率，L：导体的长度，S：导体的横截面积，where ρ: the resistivity of the conductor material, L: the length of the conductor, S: the cross-sectional area of the conductor,

电阻值的变化表达式如下：The expression for the change of resistance value is as follows:

其中ρ_c为柔性薄膜电极材料的电阻率，A_c为上下极板表面的柔性薄膜电极的接触面积，L_c为上下极板接触位置柔性薄膜电极的厚度，D_b为柔性薄膜电极在微型金字塔侧面的厚度，C_b为上下极板表面的柔性薄膜电极接触面的周长，L_b为薄膜电极在微型金字塔侧面的长度。where ρ_c is the resistivity of the flexible thin film electrode material, A_c is the contact area of the flexible thin film electrode on the surface of the upper and lower electrode plates, L_c is the thickness of the flexible thin film electrode at the contact position of the upper and lower electrode plates, D_b is the flexible thin film electrode in the micro pyramid The thickness of the side, C_b is the perimeter of the contact surface of the flexible thin film electrode on the surface of the upper and lower plates, and L_b is the length of the thin film electrode on the side of the micro pyramid.

通过外接惠斯通电桥电路，如图3所示，其中R为待测压阻材料薄膜电阻，Vc为恒压源，R1，R2，R3为电桥电阻，Vo为输出电压，将这一阻值变化转变为电信号输出，从而实现传感器芯片的作用力—电信号转换，完成对作用力的测量。Through an external Wheatstone bridge circuit, as shown in Figure 3, where R is the film resistance of the piezoresistive material to be measured, Vc is a constant voltage source, R1, R2, and R3 are bridge resistances, and Vo is the output voltage. The value change is converted into an electrical signal output, so as to realize the force-electrical signal conversion of the sensor chip, and complete the measurement of the force.

Claims (1)

Translated fromChinese

1.一种基于3D打印技术的柔性压力传感器芯片的制作方法，其特征在于，包括以下步骤：1. a manufacturing method of a flexible pressure sensor chip based on 3D printing technology, is characterized in that, comprises the following steps:1)运用DLP 3D打印机固化处于液态的光敏柔性聚氨酯树脂材料形成预定尺寸的柔性上极板(1)和均匀分布微型金字塔阵列(3)的柔性下极板(2)，柔性上极板(1)、柔性下极板(2)对应的角上预留通孔(5)；1) Using a DLP 3D printer to cure a photosensitive flexible polyurethane resin material in a liquid state to form a flexible upper plate (1) of a predetermined size and a flexible lower plate (2) with uniformly distributed micro-pyramid arrays (3), a flexible upper plate (1) ), a through hole (5) is reserved on the corresponding corner of the flexible lower plate (2);2)加工好的柔性上极板(1)和柔性下极板(2)依次置于清洗液、酒精中各超声清洗处理5min；取出柔性上极板(1)和柔性下极板(2)后置于紫外灯箱中20min使其完全固化；2) The processed flexible upper electrode plate (1) and flexible lower electrode plate (2) are placed in cleaning solution and alcohol for ultrasonic cleaning for 5 minutes in sequence; take out the flexible upper electrode plate (1) and the flexible lower electrode plate (2) Then put it in the UV light box for 20min to make it fully cured;3)将两根导线分别穿过柔性上极板(1)和柔性下极板(2)上预留的通孔(5)，并采用导电胶将导线紧密的黏附在柔性上极板(1)、柔性下极板(2)上，置于强制对流烘箱中，100℃烘烤10分钟使导电胶完全固化，取出后自然冷却至室温；3) Pass the two wires through the through holes (5) reserved on the flexible upper plate (1) and the flexible lower plate (2) respectively, and use conductive glue to tightly adhere the wires to the flexible upper plate (1). ), on the flexible lower plate (2), placed in a forced convection oven, baked at 100°C for 10 minutes to completely solidify the conductive adhesive, and then cooled to room temperature naturally after being taken out;4)将与导线相连接的柔性上极板(1)、柔性下极板(2)置于等离子处理机中进行氧等离子体处理，处理时间90s；4) placing the flexible upper electrode plate (1) and the flexible lower electrode plate (2) connected with the wires in a plasma processor for oxygen plasma treatment, and the treatment time is 90s;5)将经过氧等离子体处理的柔性上极板(1)、柔性下极板(2)置于液态导电聚合物溶液PEDOT:PSS中，使柔性上极板(1)、柔性下极板(2)表面完全浸润一层PEDOT:PSS溶液；5) The flexible upper electrode plate (1) and the flexible lower electrode plate (2) treated with oxygen plasma are placed in the liquid conductive polymer solution PEDOT:PSS, so that the flexible upper electrode plate (1) and the flexible lower electrode plate ( 2) The surface is completely soaked with a layer of PEDOT:PSS solution;6)取出表面浸润了PEDOT:PSS溶液的柔性上极板(1)、柔性下极板(2)，置于强制对流烘箱中，100℃烘烤15min，取出后自然冷却至室温，完成柔性薄膜电极(4)的制作；6) Take out the flexible upper plate (1) and the flexible lower plate (2) with the surface soaked with the PEDOT:PSS solution, place them in a forced convection oven, bake at 100° C. for 15 minutes, and then naturally cool to room temperature after taking out to complete the flexible film the production of electrodes (4);7)使用聚酰亚胺绝缘胶带将柔性上极板(1)、柔性下极板(2)粘贴在一起，同时封闭柔性上极板(1)、柔性下极板(2)侧面间隙；7) Use polyimide insulating tape to stick the flexible upper electrode plate (1) and the flexible lower electrode plate (2) together, and simultaneously close the side gaps of the flexible upper electrode plate (1) and the flexible lower electrode plate (2);所述的一种基于3D打印技术的柔性压力传感器芯片，包括柔性上极板(1)，柔性上极板(1)和均匀分布微型金字塔阵列(3)的柔性下极板(2)相接触，在柔性上极板(1)和柔性下极板(2)接触表面制作柔性薄膜电极(4)，柔性上极板(1)上的柔性薄膜电极(4)和柔性下极板(2)上的柔性薄膜电极(4)通过导线与外部电路相连接，导线位于柔性上极板(1)和柔性下极板(2)对应的角上设有的通孔(5)内。The flexible pressure sensor chip based on 3D printing technology includes a flexible upper electrode plate (1), the flexible upper electrode plate (1) and the flexible lower electrode plate (2) of the uniformly distributed micro-pyramid array (3) being in contact with each other , making a flexible membrane electrode (4) on the contact surface of the flexible upper plate (1) and the flexible lower plate (2), the flexible membrane electrode (4) and the flexible lower plate (2) on the flexible upper plate (1) The upper flexible film electrode (4) is connected to an external circuit through wires, and the wires are located in through holes (5) provided on the corresponding corners of the flexible upper electrode plate (1) and the flexible lower electrode plate (2).

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