CN101464126A - Production method of integrated submissive sensor for measuring curve clearance and force - Google Patents

Abstract

The invention relates to a preparation method of an integrated flexible sensor for measuring curved surface gap and force, and belongs to the technical field of sensors. Prepare the planar eddy current sensitive element and the ultra-thin compliant conductive polymer sensitive element respectively: use positioning glue and packaging glue to coat the base periphery of the planar eddy current sensitive element pasted with the ultra-thin compliant conductive polymer sensitive element with thermosetting encapsulation Glue, another layer of planar eddy current sensitive element is adhered to the surface with packaging glue to obtain an integrated flexible sensor. When adhering, the upper and lower layers of planar eddy current coils, inner leads and openings are opposite to each other. The sensor prepared by this method can measure the surface gap and extrusion force at the same time; it can be attached to any shape of the surface for measurement, and it is suitable for installation in a narrow space for measurement; it can be used in high temperature, radiation and other measurement occasions; and the measurement range Wide, high measurement accuracy.

Description

Preparation method of an integrated compliant sensor for measuring surface gap and force

technical field

The invention relates to a preparation method of an integrated flexible sensor for measuring curved surface gap and force, and belongs to the technical field of sensors.

Background technique

The concept of "compliant sensor" can be traced back to the late 1980s. Many special structures in aerospace vehicles have brought great difficulties to the installation of traditional rigid sensors. People hope that the sensor has good flexibility, is not limited by the shape of the object to be measured, and can be attached to various regular or irregular surfaces to achieve normal sensing functions. After entering the 1990s, scientists in the United States, France, Japan, Switzerland, Portugal and other countries began to conduct research on compliant sensors, and many new sensor materials and structures were applied to this research field.

In 2001, Professor Lumelsky, a well-known scholar in the field of sensors in the United States, put forward a bold vision for the development direction of compliant sensors. Professor Lumelsky believes that the sensitive epidermis will be a large-area array of compliant sensors, like the human skin, able to cover the entire surface of the measuring mechanism. It has the ability to perceive the external environment, and can more accurately measure changes in extrusion force, shear force, proximity distance, light intensity, temperature, humidity, and certain gas concentrations, thereby helping some autonomous control mechanisms (such as: robots) Accurately perform tasks in complex environments. It can be predicted that compliant sensor technology will bring a new revolution to the field of sensors, and will drive the development of related technologies in the fields of industrial automation, medical and health, aerospace, environmental monitoring, and robotics.

(1) Compliant eddy current sensor: At the 16th World Conference on Nondestructive Testing in 2004, Frenchman C.Gilles-Pascaud demonstrated a newly researched sensor array probe used in the detection of surface resistance cracks in the aviation field . The instrument includes a set of eddy current coil arrays containing 32 sensitive units and a high-resolution camera, which can realize real-time, complete and reliable detection of potential surface cracks, and can be well applied to various alloy materials, cracks The depth detection accuracy is about 0.2mm. The biggest feature of this system is that it realizes the real-time fusion of two different detection technologies, thereby improving the detection ability of small surface resistance cracks. It can be seen that the compliant eddy current sensor processed on the flexible substrate material can be well applied to the measurement of the gap between curved surfaces and the detection of cracks on curved surfaces.

(2) Conductive polymer material compliant force sensor: Conductive polymer composite materials refer to conductive rubber, conductive plastic, conductive paint, conductive adhesive and conductive film that have been common in recent years. Conductive polymer composite materials are divided into two types: filled type and compound type. The former is a mixture of two or more materials that mixes conductive particles into the polymer matrix to form a conductive channel; while the latter is only a single material with conductivity itself. Research in the field of functional materials has found that filled conductive polymer composites have piezoresistive effects, so some research institutions have used them as sensitive element materials to develop compliant force sensors.

Tekscan Corporation of the United States has been conducting research on compliant sensors since the 1990s. In 2003, the company launched a compliant force sensor made of conductive polymer composite material, with an area ranging from a dozen square centimeters to one square meter and a thickness of 0.15mm. The sensitive unit of the sensor is composed of upper and lower layers of electrodes and a layer of conductive polymer composite material, and the length of the lead wire can reach 700mm. The upper and lower layers of electrodes and a layer of conductive polymer composite material are packaged into a sensor as a whole by polyimide film, which ensures flexibility and reliability, and the minimum allowable bending radius reaches 100mm.

All in all, the conductive polymer composite compliant force sensor has the advantages of good compliance, large measuring range and effective area, relatively simple processing technology, and low processing cost.

In summary, the compliant eddy current sensor and the compliant force sensor can measure the surface gap and the extrusion force between surfaces well, respectively. However, with the development of science and technology and production, the shapes of key parts of some major equipment are becoming more and more complex, and the requirements for processing and assembly positioning accuracy are getting higher and higher, and the requirements for measurement are also higher. Parts with thin-walled surfaces of revolution are widely used in national defense and various daily life products, and the processing, measurement and monitoring of these parts are often limited by special conditions such as the size of the space structure and the medium of the material to be measured. Increased difficulty. When measuring the gap and extrusion force between the same curved surfaces, two kinds of sensors need to be installed, and the installation position and lead wire method are often restricted by the space structure and cannot be realized.

Contents of the invention

The purpose of the present invention is to propose an integrated flexible sensor for measuring the surface gap and force, which overcomes the deficiencies of the prior art, and makes the sensor have a thin structure, good flexibility, large range, high precision, high resolution, and can simultaneously The characteristics of measuring gap and extrusion force are suitable for online detection of curved surface gap and extrusion force in industrial production and human medical rehabilitation.

The preparation method of the integrated compliant sensor for measuring surface gap and force proposed by the present invention comprises the following steps:

(1) Preparation of planar eddy current sensitive elements:

(1-1) Open holes in rows and columns on the polyimide film substrate, the thickness of the polyimide film is 100 μm-200 μm, and the aperture of the holes is 250-350 μm;

(1-2) Copper foil is respectively plated on the front and back surfaces of the polyimide film substrate and the surface of the above-mentioned opening, and the thickness of the copper foil is 15 μm-20 μm;

(1-3) Photolithography is carried out on the above-mentioned reverse copper foil, an eddy current coil is formed centering on the above-mentioned opening, an inner lead is formed on one side of each eddy-current coil, the above-mentioned front copper foil is photo-etched, and an electric current coil is formed on the above-mentioned opening. Outer leads are formed between the holes;

(2) Preparation of ultra-thin and flexible conductive polymer sensitive elements:

(2-1) Mix the conductive carbon black powder with a particle size of less than 1 micron, the silicon dioxide dispersant powder with a particle size of 10-50 nanometers, and the liquid one-component silicone rubber in an acetone organic solvent with a concentration of more than 95%. , the volume percent concentration of each composition when mixing is: single-component silicone rubber: conductive carbon black powder: silicon dioxide dispersant powder: acetone organic solvent=100:10—15:1—3:300—500;

(2-2) Perform mechanical stirring under ultrasonic vibration, the temperature of the stirring environment is 40-60° C., and the stirring time is 2-4 hours to obtain a gel state mixture;

(2-3) Add 3-5% butadiene rubber particles accounting for the total volume of the mixture into the mixture, continue mechanical stirring for 20-30 minutes, and volatilize the acetone;

(2-4) dripping the above-mentioned acetone volatilized mixture into the rotating platform, and spin-coating to obtain a conductive polymer film with a thickness of 70-100 microns;

(2-5) the tetraethyl orthosilicate crosslinking agent accounting for 1% of the total volume of the above-mentioned conductive polymer film and the dibutyltin dilaurate catalyst accounting for 2% of the total volume of the above-mentioned conductive polymer film are mixed into a solution, and the mixed The solution is coated on the surface of the conductive polymer film to vulcanize the conductive polymer film, and the vulcanization time is more than 24 hours to obtain an ultra-thin and flexible conductive polymer sensitive element;

(3) Packaging of integrated flexible sensors:

(3-1) Coating a layer of positioning glue between every adjacent two rows of eddy current coils of the above-mentioned planar eddy current sensitive element;

(3-2) Cut the ultra-thin and compliant conductive polymer sensitive element prepared above into strips, and paste the ultra-thin and compliant conductive polymer sensitive element cut into strips on the above-mentioned positioning glue;

(3-3) Coat the periphery of the substrate of the above-mentioned planar eddy current sensitive element pasted with ultra-thin and flexible conductive polymer sensitive element with thermosetting encapsulation glue, and use the encapsulation glue to adhere another layer of planar eddy current sensitive element to the surface , to obtain an integrated flexible sensor, when adhering, the upper and lower layers of planar eddy current coils, inner leads and openings are respectively opposite.

The preparation method of the integrated compliant sensor for measuring surface gap and force proposed by the present invention has the advantages of:

1. The integrated sensitive element of the integrated flexible sensor prepared by the present invention integrates the ultra-thin planar eddy current coil and the conductive polymer force sensitive element on the same flexible substrate material, and can simultaneously measure the surface gap and extrusion force.

2. The conductive polymer force sensitive element in the integrated flexible sensor prepared by the present invention adopts a new material design and processing technology, has a large measuring range, and high force-sensing precision and resolution.

3. The ultra-thin planar eddy current coil and its lead-out cables in the integrated flexible sensor prepared by the present invention have good flexibility. Therefore, the sensor can be attached to any shape of surface for measurement. However, traditional eddy current sensors cannot be installed on curved surfaces for measurement.

4. The integrated flexible sensor prepared by the present invention can perform rapid measurement in a large area. Due to the use of printed circuit board technology, the integrated sensor array can be distributed in a large area (400mm×700mm or even larger), thereby realizing the measurement of a large area. However, other processes, such as MEMS and other microfabrication processes, cannot fabricate large-area flexible sensor arrays, so it is also difficult to achieve large-area measurement. If a single sensor is used to measure a large area, it is necessary to use a mechanical device to control the sensor or the measured target to move regularly, which will inevitably affect the speed and accuracy of the measurement. However, in the present invention, a multiplex switch is used to realize fast cycle scanning of the sensor array. Scanning a channel takes only 20 milliseconds.

5. The integrated flexible sensor prepared by the present invention has ultra-thin characteristics. The minimum thickness of the integrated sensor array and its outgoing cables can be 0.3mm, which is suitable for installation in a small space for measurement.

6. The integrated flexible sensor prepared by the present invention can form a close-packed cable. The leads of the sensor array are brought together to form a densely packed long cable, making the structure more compact. Due to the measurement method of circular scanning, at any time, only one group of lines in the cable has signal transmission, so the signals transmitted by the cable do not interfere with each other.

7. Compared with traditional gap measurement and force measurement sensors, the integrated flexible sensor prepared by the present invention can be applied to many measurement occasions, such as curved surface measurement, rapid measurement in a large area, and measurement in a narrow space. If the base material is polyimide, the sensor array can also be used in high temperature (300-400° C.), radiation and other measurement occasions.

8. The integrated flexible sensor prepared by the present invention has a thickness of only 0.3mm; good compliance performance, and the minimum bending radius can reach 200mm; the sensor array area can be customized, and the range is 400-700mm ² ; the measuring range of force: 0～ 2MPa; force measurement accuracy: 1% FS; force measurement resolution: 0.2% FS; measurement gap resolution: 1μm; measurement gap sensitivity: 100Hz/μm; measurement gap accuracy: ±1% FS; measurement gap Measuring range: 0~5mm.

Description of drawings

Fig. 1 is a front plan view of the sensor before packaging in the process of preparing the integrated flexible sensor of the present invention.

FIG. 2 is a reverse plan view of the front-of-package sensor shown in FIG. 1 .

Fig. 3 is an A-A sectional view of the sensor shown in Fig. 1 after packaging.

Fig. 4 is a B-B sectional view of the sensor shown in Fig. 1 after packaging.

In Figure 1-Figure 3, 1 is the base, 2 is the outer lead, 3 is the inner lead, 4 is the opening, 5 is the ultra-thin conductive polymer material sensitive element, 6 is the positioning glue, 7 is the eddy current coil, 8 is the sealant.

Detailed ways

The preparation method of the integrated compliant sensor for measuring the surface gap and force proposed by the present invention, the front plan view of the sensor before packaging during the preparation process is shown in Figure 1, including the following steps:

(1) Preparation of planar eddy current sensitive elements:

(1-1) On the polyimide film substrate 1, holes 4 are opened in rows and columns, the thickness of the polyimide film is 100 μm-200 μm, and the aperture of the holes is 250-350 μm;

(1-2) Copper foil is respectively plated on the front and back surfaces of the polyimide film substrate and the surface of the above-mentioned opening, and the thickness of the copper foil is 15 μm-20 μm;

(1-3) The above-mentioned reverse copper foil is carried out photoetching, the eddy current coil 7 is formed centering on the above-mentioned opening 4, and the inner lead 3 is formed on one side of each eddy current coil 7, and the above-mentioned front copper foil is photo-etched. , forming an outer lead 2 between the above-mentioned openings 4, as shown in FIG. 2 ;

(2) Preparation of ultra-thin and flexible conductive polymer sensitive elements:

(2-1) Mix the conductive carbon black powder with a particle size of less than 1 micron, the silicon dioxide dispersant powder with a particle size of 10-50 nanometers, and the liquid one-component silicone rubber in an acetone organic solvent with a concentration of more than 95%. , the volume percent concentration of each composition when mixing is: single-component silicone rubber: conductive carbon black powder: silicon dioxide dispersant powder: acetone organic solvent=100:10—15:1—3:300—500;

(2-2) Perform mechanical stirring under ultrasonic vibration, the temperature of the stirring environment is 40-60° C., and the stirring time is 2-4 hours to obtain a gel state mixture;

(2-3) Add 3-5% butadiene rubber particles accounting for the total volume of the mixture into the mixture, continue mechanical stirring for 20-30 minutes, and volatilize the acetone;

(2-4) dripping the above-mentioned acetone volatilized mixture into the rotating platform, and spin-coating to obtain a conductive polymer film with a thickness of 70-100 microns;

(2-5) the tetraethyl orthosilicate crosslinking agent accounting for 1% of the total volume of the above-mentioned conductive polymer film and the dibutyltin dilaurate catalyst accounting for 2% of the total volume of the above-mentioned conductive polymer film are mixed into a solution, and the mixed The solution is coated on the surface of the conductive polymer film to vulcanize the conductive polymer film, and the vulcanization time is more than 24 hours to obtain an ultra-thin and flexible conductive polymer sensitive element;

(3) Packaging of integrated flexible sensors:

(3-1) Coating a layer of positioning glue 6 between every adjacent two rows of eddy current coils of the above-mentioned planar eddy current sensitive element;

(3-2) Cut the ultra-thin and compliant conductive polymer sensitive element prepared above into strips, and paste the ultra-thin and compliant conductive polymer sensitive element cut into strips on the above-mentioned positioning glue;

(3-3) Coat the periphery of the substrate of the above-mentioned planar eddy current sensitive element pasted with ultra-thin and flexible conductive polymer sensitive element with thermosetting encapsulation glue, and use the encapsulation glue to adhere another layer of planar eddy current sensitive element to the surface , to obtain an integrated flexible sensor, when adhering, the upper and lower layers of planar eddy current coils, inner leads and openings are respectively opposite.

In the above method, the formulations of two examples for preparing ultra-thin and flexible conductive polymer sensitive elements are:

The volume percent concentration of each composition during mixing is: single-component silicone rubber: conductive carbon black powder: silicon dioxide dispersant powder: acetone organic solvent=100:12:2:350;

Or the volume percent concentration of each component during mixing is: single-component silicone rubber: conductive carbon black powder: silicon dioxide dispersant powder: acetone organic solvent=100:14:2.5:400.

The integrated flexible sensor prepared by the present invention is composed of upper and lower electrode layers packaged into one body and an array of conductive polymer force sensitive elements pressed therebetween, as shown in Fig. 3 and Fig. 4 .

The integrated flexible sensor prepared by the present invention adopts a conductive polymer material with piezoresistive effect as a sensitive element for measuring stress. The material uses conductive carbon black powder as a conductive phase and silicone rubber as an insulating phase, and is mixed according to an optimized ratio. Mixing techniques such as ultrasonic oscillation, organic solvent dissolution, heating and stirring, nano-dispersion and elastomer blending have been introduced.

The electrode layer of the conductive polymer force sensitive element used in the integrated flexible sensor prepared by the present invention is made on the film substrate by using the flexible printed circuit board technology, wherein the upper and lower electrodes adopt ultra-thin planar eddy current coils instead of traditional plate electrodes. The upper and lower electrodes can use ultra-thin planar eddy-current coils separately, or can use ultra-thin planar eddy-current coils simultaneously. Thus, the upper and lower electrodes form a single-layer or double-layer eddy current detection structure. The ultra-thin planar eddy current coil is integrated with the conductive polymer force sensing element to form an integrated sensing element capable of simultaneously measuring gap and extrusion force.

Each planar eddy current coil of the sensor array in the integrated flexible sensor prepared by the present invention has two signal wires, and the lead wires of the upper and lower electrodes naturally form the signal wires of the conductive polymer force sensitive elements. The signal wires of the sensitive elements are collected together to form a close-packed outgoing cable, and the other end of the cable is provided with a plug connected with a multi-way strobe switch.

The conductive polymer force sensitive element in the integrated flexible sensor prepared by the present invention can be made into single layer, double layer or even multilayer, and the shape of the planar eddy current coil can be circular, square or other shapes.

The preparation process of the integrated flexible sensor prepared by the present invention adopts the technological process of photoetching leads, coating positioning glue, attaching force sensitive elements, coating encapsulation glue and hot-pressing encapsulation. Material selection and design are carried out according to measurement conditions and requirements. The film base can be made of flexible materials suitable for printed circuit board technology, such as polyimide film, polyester film, etc.

The working principle of the integrated flexible sensor sensitive element prepared by the present invention is introduced below:

The integrated sensitive element of the present invention is composed of a planar eddy current sensitive element and a conductive polymer force sensitive element, and the signal leads of the planar eddy current sensitive element are simultaneously used as signal leads of the conductive polymer force sensitive element.

a. Working principle of eddy current sensitive element measuring gap:

The general working principle of eddy current testing is to detect the interaction between the magnetic field of the excitation coil and the induced eddy current magnetic field of the conductor under test. When the sensitive coil is fed with alternating current, an alternating magnetic field will be generated around the coil. If the metal conductor target is moved into this alternating magnetic field at this time, an eddy current will be induced on the surface of the target, and this eddy current will generate A magnetic field whose direction is exactly opposite to the direction of the original coil magnetic field, thus weakening the original magnetic field and causing a change in the magnetic field. The change of the magnetic field is reflected by the impedance change of the sensitive coil, and the equivalent impedance Z of the coil can generally be expressed as the following function:

Z=F(σ, μ, f, x, r)

Among them, σ, μ are the electrical conductivity and magnetic permeability of the metal conductor to be tested, f is the frequency of the excitation signal, x is the distance between the coil and the metal conductor, r is the size factor of the coil, and the structure and shape of the coil and size related. It can be seen that the change of coil impedance completely and uniquely reflects the eddy current effect of the metal conductor under test. In the actual detection, the detection of a relevant quantity in the above formula can be realized by controlling the unnecessary influencing factors. As a proximity sensor, the distance between the coil and the metal target is directly related to the impedance of the coil, and when detecting defects on the metal surface or near the surface, the existence of defects will cause changes in the electrical conductivity and magnetic permeability of the measured conductor, and then Change the impedance parameters of the coil. The measurement data of the spherical gap at the measuring point can be obtained through the eddy current sensor.

b. The working principle of the conductive polymer sensitive element to measure the extrusion force:

From the perspective of the microscopic conductive mechanism, the reason for the piezoresistive effect of carbon black-filled silicone rubber composites can be attributed to the change in the distribution of carbon black particles in the silicone rubber matrix, more precisely, the change in the distance between conductive carbon black particles . The external pressure can compress the volume of the composite material. Since the compressibility of the conductive carbon black particles is much smaller than that of the silicone rubber matrix, the distance between the conductive particles is reduced, which increases the probability of contact conduction and tunneling. As the pressure increases, the distance between the conductive carbon black particles gradually decreases, and due to the contact conduction and tunneling mechanism, a conductive channel is formed inside the material. The generation of contact conduction and tunnel effect mechanism is affected by the particle size and shape of conductive particles, so the piezoresistive effect of the material shows a close relationship with the shape parameters. The larger the shape parameter value of the material, the higher the probability of contact conduction and tunneling effect, and the more obvious the piezoresistive effect of the material.

From the perspective of the conductive seepage phenomenon, the resistivity of the material changes significantly with the volume concentration of the conductive filler in the conductive seepage area. This is because, when the external pressure reduces the volume of the polymer matrix, the volume concentration of conductive particles increases correspondingly, causing a significant change in the resistivity of the material. The deformation of the material causes the change of the conductive seepage. With the deformation of the material, the volume concentration of carbon black and the resistivity of the material decrease. When the volume concentration of carbon black is closer to the percolation threshold, the piezoresistive effect of the material is more obvious. In the effective medium universal equation, the volume concentration of carbon black, the percolation threshold and the shape parameters of the material together characterize the conductive percolation phenomenon, which also shows that the piezoresistive effect of carbon black-filled silicone rubber composites is a specific aspect of its conductive percolation phenomenon. Performance. In addition, the deformation of the material not only causes a change in resistivity, but also changes its geometric coefficient of resistance (that is, the ratio of the length of the material to the cross-sectional area along the current direction). In summary, the stress deformation of carbon black-filled silicone rubber composites is the direct cause of the piezoresistive effect.

On the macro surface, due to the effect of pressure, the conductive polymer material that constitutes the sensitive element produces a change in resistance, and this change is linearly proportional to the pressure within a certain range.

The working mode of the array integrated compliant sensor prepared by the present invention is introduced as follows:

In actual work, attach the sensor between the curved surfaces. The impedance change of each eddy current coil of the sensor is measured by the oscillating circuit, the resistance change between each pair of electrodes of the sensor is measured by the resistance sampling circuit, and the corresponding gap value and extrusion force value are obtained according to the calibration curve. Through the signal sampling and array scanning circuit and the multi-way strobe switch, the sensitive element can be scanned in a fast cycle, and the measured value of each sensitive element can be measured. Since the distribution of these sensitive elements is known, the distribution of surface clearance and extrusion force can be obtained by data processing of the measurement results.

Claims (1)

1. A method for preparing an integrated compliant sensor for measuring surface gap and force, characterized in that the method comprises the following steps: (1) Preparation of planar eddy current sensitive elements: (1-1) Open holes in rows and columns on the polyimide film substrate, the thickness of the polyimide film is 100 μm-200 μm, and the aperture of the holes is 250-350 μm; (1-2) Copper foil is respectively plated on the front and back surfaces of the polyimide film substrate and the surface of the above-mentioned opening, and the thickness of the copper foil is 15 μm-20 μm; (1-3) Photolithography is carried out on the above-mentioned reverse copper foil, an eddy current coil is formed centering on the above-mentioned opening, an inner lead is formed on one side of each eddy-current coil, the above-mentioned front copper foil is photo-etched, and an electric current coil is formed on the above-mentioned opening. Outer leads are formed between the holes; (2) Preparation of ultra-thin and flexible conductive polymer sensitive elements: (2-1) Mix the conductive carbon black powder with a particle size of less than 1 micron, the silicon dioxide dispersant powder with a particle size of 10-50 nanometers, and the liquid one-component silicone rubber in an acetone organic solvent with a concentration of more than 95%. , the volume percent concentration of each composition when mixing is: single-component silicone rubber: conductive carbon black powder: silicon dioxide dispersant powder: acetone organic solvent=100:10—15:1—3:300—500; (2-2) Perform mechanical stirring under ultrasonic vibration, the temperature of the stirring environment is 40-60° C., and the stirring time is 2-4 hours to obtain a gel state mixture; (2-3) Add 3-5% butadiene rubber particles accounting for the total volume of the mixture into the mixture, continue mechanical stirring for 20-30 minutes, and volatilize the acetone; (2-4) drop the above-mentioned acetone volatilized mixture into a rotating platform, and spin-coat to form a conductive polymer film with a thickness of 70-100 microns; (2-5) the tetraethyl orthosilicate crosslinking agent accounting for 1% of the total volume of the above-mentioned conductive polymer film and the dibutyltin dilaurate catalyst accounting for 2% of the total volume of the above-mentioned conductive polymer film are mixed into a solution, and the mixed The solution is coated on the surface of the conductive polymer film to vulcanize the conductive polymer film, and the vulcanization time is more than 24 hours to obtain an ultra-thin and flexible conductive polymer sensitive element; (3) Packaging of integrated flexible sensors: (3-1) Coating a layer of positioning glue between every adjacent two rows of eddy current coils of the above-mentioned planar eddy current sensitive element; (3-2) Cut the ultra-thin and compliant conductive polymer sensitive element prepared above into strips, and paste the ultra-thin and compliant conductive polymer sensitive element cut into strips on the above-mentioned positioning glue; (3-3) Coat the periphery of the substrate of the above-mentioned planar eddy current sensitive element pasted with ultra-thin and flexible conductive polymer sensitive element with thermosetting encapsulation glue, and use the encapsulation glue to adhere another layer of planar eddy current sensitive element to the surface , to obtain an integrated flexible sensor, when adhering, the upper and lower layers of planar eddy current coils, inner leads and openings are respectively opposite.

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