Preparation method, sensor and equipment for static and dynamic three-dimensional microcrack extension sensor

Abstract

The present invention belongs to the field of sensor technology, and provides a method for preparing a static and dynamic three-dimensional microcrack extension sensor, a sensor and a device. The preparation method includes preparing a piezoresistive / piezoelectric sensing functional material dispersion, and attaching it to the surface of a fiber cloth substrate to obtain a piezoresistive / piezoelectric sensing fiber cloth; pre-stretching the piezoresistive / piezoelectric sensing fiber cloth to obtain a piezoresistive / piezoelectric sensing three-dimensional microcrack fiber cloth; microwave ablating the piezoresistive / piezoelectric sensing three-dimensional microcrack fiber cloth, removing the fiber cloth substrate, and obtaining a piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton; coating conductive layers on both sides of the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton to form electrodes; polarizing the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton with electrodes formed on the surface; and encapsulating the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton to obtain a static and dynamic three-dimensional microcrack extension sensor.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, and in particular relates to a preparation method of a static and dynamic three-dimensional micro-crack extension sensor, a sensor and equipment. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Sensors are the key to achieve structural health monitoring. Conductive / piezoelectric materials such as piezoresistive materials (such as graphite, carbon black, carbon fiber, carbon nanotubes, graphene) and piezoelectric ceramics (such as lead titanate, zinc oxide, lead zirconate titanate) are added to cement concrete to make intrinsic sensing blocks. Cement-based piezoelectric sensing blocks need to go through a series of processes such as mixing, pressing, polarization, and buried or embedded in various structural systems. The operation is complicated and not suitable for actual construction. At the same time, with the development of sensing functional materials, resistance strain gauges (wires), piezoelectric ceramics, fatigue life wires, shape memory alloys, fiber gratings, etc. have appeared one after another, but these sensors for the engineering field either need to be buried in the structural system, the embedding process is complex, the survival rate is low, or the cost is high and the life is short, or the anti-interference ability and corrosion resistance are poor, or the compatibility with concrete is poor, which affects the mechanical properties of the structure.

[0004] Compared with the above-mentioned intrinsic sensing block materials, the flexible sensing film can be prepared in advance, eliminating the on-site production process, and can be well applied to the surface and interior of the structure, adapting to the requirements of various special sizes and shapes of structures, and pasting it on the structure has little effect on the performance of the sensing material itself.

[0005] Flexible sensing film sensors can be divided into four types according to their working principles: piezoresistive, capacitive, piezoelectric and triboelectric. Since the initial capacitance of capacitive sensors is very small, they are easily affected by the random parasitic capacitance formed by the measuring circuit and the surrounding conductors, which makes them unstable during operation. Triboelectric sensors have strict packaging requirements in practical applications, and attention should be paid to waterproof and moisture-proof treatment. In addition, the triboelectric effect of triboelectric sensors will decrease with the increase of working time, and the mechanical stability is poor. Piezoresistive sensors and piezoelectric sensors have simple processes, low costs, and stable sensing performance. Therefore, they are more suitable for structural health monitoring than capacitive sensors and triboelectric sensors.

[0006] However, piezoresistive film sensors can only detect static signals of structures, but cannot sense the deformation state of the structure, and are not sensitive to strain rate. Although piezoelectric sensor films respond quickly, they are only suitable for detecting dynamic signals, such as transient force changes, deformation rate, etc., and cannot reflect the final strain state. Therefore, single-mode piezoresistive sensor films or piezoelectric sensor films will cause information loss during the static / dynamic signal detection process of structures. In order to solve these shortcomings, static / dynamic dual-mode sensors are proposed.

[0007] Chinese patent CN105953821B first disclosed a piezoresistive / piezoelectric sandwich sensor, including: a tough substrate, 5-50 self-assembled thin film piezoresistive sensing functional layers (top / bottom electrode layers) and a piezoelectric sensing elastic sandwich functional layer; wherein, the piezoelectric sensing elastic sandwich functional layer is made of nano ZnO / PDMS or PVDF / PDMS, which can effectively monitor static and dynamic signals, but the zinc sheet has poor flexibility, and the pasting effect is not ideal when the working surface is irregular, and the encapsulated elastomer and the conductive layer are mechanically unstable under external forces, and the conductive layer is easily separated from the elastomer and loses its function. At the same time, this type of sensor film is thick and has poor sensitivity, and it is difficult to have high sensitivity and high flexibility at the same time. Summary of the invention

[0008] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a method for preparing a static and dynamic three-dimensional microcrack extension sensor, a sensor and a device, which are suitable for structural monitoring and have the characteristics of high flexibility, rapid and sensitive perception of static and dynamic signals.

[0009] In order to achieve the above object, the present invention adopts the following technical solution:

[0010] The first aspect of the present invention provides a method for preparing a static and dynamic three-dimensional microcrack extension sensor, which comprises:

[0011] Preparing a piezoresistive / piezoelectric sensing functional material dispersion and attaching it to the surface of a fiber cloth substrate to obtain a piezoresistive / piezoelectric sensing fiber cloth;

[0012] Pre-stretching the piezoresistive / piezoelectric sensing fiber cloth to obtain the piezoresistive / piezoelectric sensing three-dimensional micro-crack fiber cloth;

[0013] Microwave ablation of piezoresistive / piezoelectric sensing three-dimensional microcrack fiber cloth, removing the fiber cloth matrix, and obtaining a piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton;

[0014] Conductive layers are coated on both sides of the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton to form electrodes;

[0015] The piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton with electrodes formed on the surface is polarized;

[0016] The piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton is encapsulated with an elastomer to obtain a static and dynamic three-dimensional microcrack extension sensor.

[0017] As an implementation method, in the process of polarizing the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton with electrodes formed on the surface, a conductor with a set thickness and an area equal to the area of ​​the coated silver paste is superimposed on the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton and placed between the point contact electrode and the bottom electrode of the polarization device for polarization treatment.

[0018] As an implementation method, the process of preparing the piezoresistive / piezoelectric sensing functional material dispersion is as follows:

[0019] Preparing a piezoelectric functional material precursor solution;

[0020] By using an ultrasonic surfactant method, the material with piezoresistive function is mixed and dispersed in a piezoelectric functional material precursor solution to obtain a piezoresistive / piezoelectric sensing functional material dispersion.

[0021] As an implementation mode, the conductive layer coated on both sides of the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton is a conductive silver paste.

[0022] As an embodiment, the piezoresistive functional material is one or a mixture of CNT, GO, GO grafted carbon fiber, GO grafted carbon nanofiber, GnP.

[0023] As an implementation mode, the piezoelectric functional material is a PZT precursor / powder, a nano ZnO precursor / powder or an aluminum nitride powder.

[0024] As an embodiment, the fiber cloth substrate is synthetic fiber fabric or cotton cloth.

[0025] As an implementation method, before the conductive layers are coated on both sides of the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton respectively, the following steps are also included:

[0026] Cleaning piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton.

[0027] As an embodiment, after the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton with electrodes formed on the surface is polarized, it also includes:

[0028] Removing silicone oil from the surface of the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton.

[0029] A second aspect of the present invention provides a static and dynamic three-dimensional microcrack extension sensor, which is prepared by the static and dynamic three-dimensional microcrack extension sensor preparation method as described above.

[0030] The third aspect of the present invention provides a structural monitoring device, which includes the static and dynamic three-dimensional micro-crack extension sensor described above.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The present invention provides a method for preparing a static and dynamic three-dimensional micro-crack extension sensor, which comprises attaching a dispersed material of a piezoresistive / piezoelectric sensing functional material onto a flexible fiber cloth; generating three-dimensional annular microcracks through pre-stretching, and forming a three-dimensional curled tubular skeleton through microwave ablation; and obtaining a crack sensor pasted on the surface or inside of a structure after electrode coating, polarization, and elastomer packaging. The static and dynamic three-dimensional micro-crack extension sensor has the characteristics of high piezoresistive and piezoelectric dual-mode sensitivity and a high piezoelectric coefficient, and has many advantages such as three-dimensional crack sensing capability, good flexibility, flexible size adjustment, and good static / dynamic sensing stability. Moreover, applying the sensor to the structure will not affect the performance of the structure and the material, and can be tightly adhered to the surface of the structure, thereby realizing rapid and stable monitoring of static / dynamic performance index parameters of the structure covering the entire frequency domain.

[0033] (2) In the present invention, the piezoresistive / piezoelectric sensing functional material dispersion is attached to the flexible fiber matrix, the fiber structure of the fiber cloth is used to form a skeleton structure, and the flexible fiber cloth matrix is ​​removed by microwave ablation. The elastomer can pass through the skeleton gap and interweave with the skeleton to ensure that the sensor has sufficient mechanical stability when an external force acts, avoiding the problem of poor mechanical stability of the sensor caused by separation due to differences in mechanical properties between the sensing functional layer and the flexible fiber cloth matrix or between the sensing functional layer and the elastomer. At the same time, removing the flexible fiber cloth matrix is ​​beneficial to improving sensitivity; a small pre-stretching strain can generate three-dimensional microcracks, so that the final sensor can respond under a small external disturbance, and the change in the spacing between the numerous three-dimensional microcracks causes a change in contact resistance; at the same time, after the fiber is removed by microwave ablation, the sensing functional material is in a three-dimensional curled tube shape. Again, the fiber cloth is removed by microwave ablation, and the elastomer is filled to further avoid the debonding of the functional material and the fiber cloth under static and dynamic loads, causing sensor failure; under the triple action, the static and dynamic three-dimensional microcrack extension sensor has higher sensitivity, solving the problem that the cracks in the sensing layer of the crack sensor are generally two-dimensional planar structures, which limits the improvement of the sensor sensitivity. The resulting sensor has both high piezoresistive and piezoelectric dual-mode sensitivity and flexibility.

[0034] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0036] Figure 1 This is a preparation process of a static and dynamic three-dimensional micro-crack extension sensor according to an embodiment of the present invention;

[0037] Figure 2 It is an enlarged schematic diagram of a static and dynamic three-dimensional micro-crack extension sensor according to an embodiment of the present invention.

[0038] Among them: 1. Piezoresistive / piezoelectric sensing three-dimensional microcrack functional layer; 2. three-dimensional microcracks; 3. packaging layer; 4. electrode. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0040] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0041] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0042] Embodiment 1

[0043] Reference Figure 1 This embodiment provides a method for preparing a static and dynamic three-dimensional microcrack extension sensor, which includes:

[0044] Step 1: Prepare a piezoresistive / piezoelectric sensing functional material dispersion and attach it to the surface of a fiber cloth substrate to obtain a piezoresistive / piezoelectric sensing fiber cloth.

[0045] In step 1, the process of preparing the piezoresistive / piezoelectric sensing functional material dispersion is as follows:

[0046] Preparing a piezoelectric functional material precursor solution;

[0047] By using an ultrasonic surfactant method, the material with piezoresistive function is mixed and dispersed in a piezoelectric functional material precursor solution to obtain a piezoresistive / piezoelectric sensing functional material dispersion.

[0048] The piezoelectric functional material precursor solution can be prepared by a sol-gel method well known to those skilled in the art. The piezoresistive functional material is one or a mixture of CNT, GO, GO-grafted carbon fiber, GO-grafted carbon nanofiber, GnP; the piezoelectric functional material is a PZT precursor / powder, a nano ZnO precursor / powder or an aluminum nitride powder.

[0049] In one embodiment, the piezoresistive functional material is CNT, and the piezoelectric functional material is PZT precursor / powder, and the preparation process is as follows:

[0050] 36 parts of zirconium oxynitrate are dissolved in 500 parts of distilled water, 49 parts of butyl titanate are dissolved in 200 parts of ethylene glycol, and 107 parts of lead acetate are dissolved in 230 parts of ethylene glycol. The zirconium oxynitrate aqueous solution and the butyl titanate ethylene glycol solution are mixed at 60°C and magnetically stirred for 30 minutes. The lead acetate ethylene glycol solution is slowly added dropwise. Glacial acetic acid and ammonia water are added to adjust the pH value to 4.6. The reaction is continued at 60°C for 4 hours to obtain a PZT piezoelectric functional material precursor solution.

[0051] Two portions of CNT were added into the PZT piezoelectric functional material precursor solution, and ultrasonic treatment was performed with a 200W probe for 30 minutes to obtain a CNT / PZT piezoresistive / piezoelectric sensing functional material dispersion.

[0052] Wherein, the fiber cloth matrix is ​​a fiber fabric or a cotton cloth. The fiber fabric can be a polyurethane (PU) fiber cloth with a low elastic modulus, a polyamide fiber cloth, etc.

[0053] Specifically, the prepared piezoresistive / piezoelectric sensing functional material dispersion can be attached to the surface of the flexible fiber cloth substrate by methods well known to technicians in this field, such as immersion pulling, manual coating, and spray gun coating, and then heated volatilization or natural drying can be used to obtain the piezoresistive / piezoelectric sensing fiber cloth.

[0054] In one embodiment, the process of introducing CNT / PZT piezoresistive / piezoelectric sensing functional materials into the fiber cloth matrix is ​​as follows:

[0055] Step 1.1: Cut the fiber cloth into long strips (e.g. 10×70 mm), lay the fiber cloth flat in a container, and fix the two ends with tape;

[0056] Step 1.2: Use the spray coating method to evenly spray the CNT / PZT piezoresistive / piezoelectric sensing functional material dispersion obtained in step 1.1 on the fiber cloth, only spraying the middle 50mm range, the spray pressure is 0.2MPa, the spray gun is sprayed at a distance of 15cm from the fiber cloth, and the spraying time is 15s;

[0057] Step 1.3: Set the temperature of the thermostat to 60-80℃, evaporate in the fume hood for 1-2 hours, and after the ammonia evaporates, place it in a vacuum drying oven at 100℃ for 3-5 hours to remove all moisture, then heat it to 120℃ and keep it for 1-2 hours to remove all glacial acetic acid, and finally heat it to 200℃ and keep it for 3-6 hours to remove all ethylene glycol;

[0058] Step 1.4: Repeat steps 1.2 and 1.3 to spray the other side of the fiber cloth to obtain the CNT / PZT piezoresistive / piezoelectric sensing fiber cloth.

[0059] Step 2: Pre-stretch the piezoresistive / piezoelectric sensing fiber cloth to obtain the piezoresistive / piezoelectric sensing three-dimensional micro-crack fiber cloth.

[0060] The piezoresistive / piezoelectric sensing functional material attached to the surface of the flexible fiber cloth substrate is stretched to a certain extent by film pre-tensioning, roller bending, material tensile testing machine or manual pre-stretching, thereby forming three-dimensional microcracks to obtain a piezoresistive / piezoelectric sensing three-dimensional microcrack fiber cloth.

[0061] In this embodiment, the CNT / PZT piezoresistive / piezoelectric sensing fiber cloth is clamped on a stretching fixture and pre-stretched using a material stretching testing machine. The stretching rate is 5 mm / min, the pre-stretching strain is 7% (42 s), the stretching process lasts for a set time (e.g. 42 s), and the stretching is maintained for a set time (e.g. 30 s) after the stretching is completed to obtain a CNT / PZT piezoresistive / piezoelectric sensing three-dimensional micro-crack fiber cloth.

[0062] Step 3: Microwave ablation of the piezoresistive / piezoelectric sensing three-dimensional microcrack fiber cloth to remove the fiber cloth matrix to obtain a piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton.

[0063] For example: the piezoresistive / piezoelectric sensing three-dimensional microcrack fiber cloth is treated with 700-1500W microwave ablation for 30-40s to obtain a piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton.

[0064] In this embodiment, the obtained CNT / PZT piezoresistive / piezoelectric sensing three-dimensional microcrack fiber cloth is subjected to 1000W microwave treatment for 30s, and the flexible fiber cloth matrix is ​​removed to obtain a CNT / PZT piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton.

[0065] Step 4: Coat conductive layers on both sides of the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton to form electrodes. The conductive layers coated on both sides of the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton are conductive silver paste.

[0066] For example, conductive silver paste is coated on the surface of the prepared piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton by methods such as manual coating and vacuum evaporation well known to those skilled in the art to form cross-finger electrodes or stripe electrodes.

[0067] Before the conductive layers are coated on both sides of the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton, the following steps are also included:

[0068] Clean the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton. For example: clean with anhydrous ethanol.

[0069] In one embodiment, the prepared CNT / PZT piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton is cleaned with anhydrous ethanol, and then a fine brush is dipped in low-temperature conductive silver paste to slowly infiltrate and apply the conductive silver paste on one side of the film, and the wire is glued on, and dried at 60°C for 30 minutes, and then the other side of the CNT / PZT piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton is applied.

[0070] Step 5: Polarize the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton with electrodes formed on the surface.

[0071] In a specific implementation, during the polarization process of the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton with electrodes formed on the surface, a conductor with a set thickness and an area equal to the area of ​​the silver paste coating is stacked on the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton and placed between the point contact electrode of the polarization device and the bottom electrode for polarization treatment. This can prevent the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton from being broken down.

[0072] Specifically, after the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton with electrodes formed on the surface is polarized, it also includes:

[0073] Removing silicone oil from the surface of the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton.

[0074] For example: use anhydrous ethanol to remove the silicone oil on the surface of the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton.

[0075] In one embodiment, the electrode-coated CNT / PZT piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton is placed in 60°C silicone oil and polarized at 50MV / m for 1 hour, then cooled to room temperature under an external electric field. After the polarization, the silicone oil on the surface is removed by washing with anhydrous ethanol and allowed to stand for 24 hours.

[0076] Step 6: Encapsulate the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton to obtain a static and dynamic three-dimensional microcrack extension sensor.

[0077] In step 6, an elastic packaging layer is used to encapsulate the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton.

[0078] The piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton is encapsulated using elastic packaging layers such as polydimethylsiloxane (PDMS), polyacrylate, polyurethane, ultra-soft silicone rubber, EPDM rubber and hydrogel materials using methods well known to those skilled in the art, and ultimately a static and dynamic three-dimensional microcrack extension sensor is obtained.

[0079] For example: the CNT / PZT piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton will be placed in a silicone mold that has been previously coated with a release agent. The size of the silicone mold is 90×20×3mm. The PDMS main agent and the curing agent are mixed in a mass ratio of 10:1. Stir slowly during mixing, let it stand for 30 minutes before potting, inject PDMS, let it stand for 15-30 minutes after potting to remove bubbles, and then heat and cure at 60°C for 4 hours to finally obtain a CNT / PZT static and dynamic three-dimensional microcrack extension sensor.

[0080] Using quasi-static 33 / d 31 The measuring instrument tests the piezoelectric strain coefficient d of the CNT / PZT piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton after polarization 33 -19.8pC / N,d 31 The sensor resistivity changes when the sensor is attached to the simply supported beam system under three-point bending conditions at mid-span under static strain. The sensitivity is 294 and the linearity is 0.999. The sensor voltage change sensitivity is 180 and the linearity is 0.99 when the dynamic strain acts. The structural strain in the range of 0-60% can be sensitively sensed. A 2kHz dynamic pressure (2.44kPa) was applied to the sensor for a cyclic stability test, and the corresponding output voltage was recorded by a static / dynamic signal acquisition instrument. After 5000 cycles, the output voltage of the sensor was almost constant during the entire stability test, and the performance did not decrease. The entire sensor still maintained its integrity, and the surface flexible seal was not damaged.

[0081] Embodiment 2

[0082] This embodiment provides a method for preparing a static and dynamic three-dimensional microcrack extension sensor. The difference between this method and the first embodiment is that the piezoresistive / piezoelectric sensing functional material in step 1 is different, and the other steps are similar to those of the first embodiment.

[0083] In this embodiment, the preparation process of the CNT piezoresistive sensing functional material dispersion is as follows:

[0084] 3 parts of CTAB and 1 part of CNT were added into 500 parts of deionized water, and the dispersion was immersed in ultrasound for 5 min and ultrasound was performed with a 200 W probe for 30 min to obtain CNT slurry.

[0085] The process of introducing the CNT piezoresistive sensing functional material into the fiber cloth matrix is ​​as follows: refer to steps 1.1 and 1.2 in Example 1, dry at 80°C for 15 minutes after spraying, and repeat step 1.4.

[0086] The process of introducing nano zinc oxide (ZnO) piezoelectric sensing functional materials is as follows:

[0087] After 100 parts of PDMS main agent and 50 parts of ZnO nanopowder were uniformly dispersed by ultrasonic method (ultrasonic energy 5 kJ / mL), 10 parts of PDMS curing agent were added and stirred to obtain ZnO / PDMS slurry. Then, a glass rod was used to apply the slurry to the prepared CNT piezoresistive sensing fiber cloth, and the slurry was cured by heating at 60°C for 4 hours. Then, the other side of the CNT piezoresistive sensing fiber cloth was treated by the same process.

[0088] Repeat steps 2 to 5 in Example 1. Before coating the ZnO / PDMS piezoelectric functional layer, apply a layer of conductive silver paste on the CNT piezoresistive sensing fiber cloth and lead it out with a wire to finally obtain a CNT / ZnO static and dynamic three-dimensional microcrack extension sensor.

[0089] Using quasi-static 33 / d 31 The measuring instrument tests the piezoelectric strain coefficient d of the CNT / ZnO piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton after polarization 33 -23pC / N,d 31 The sensor resistivity changes when the sensor is attached to the simply supported beam system under three-point bending conditions at mid-span under static strain. The sensitivity is 273 and the linearity is 0.97. The sensor voltage change sensitivity is 98 and the linearity is 0.98 when the dynamic strain acts. The structural strain in the range of 0-60% can be sensitively sensed. A 2kHz dynamic pressure (2.44kPa) was applied to the sensor for a cyclic stability test, and the corresponding output voltage was recorded by a static / dynamic signal acquisition instrument. After 5000 cycles, the output voltage of the sensor was almost constant during the entire stability test, and the performance did not decrease. The entire sensor still maintained its integrity, and the surface flexible seal was not damaged.

[0090] Embodiment 3

[0091] This embodiment provides a method for preparing a static and dynamic three-dimensional microcrack extension sensor. The difference from the first embodiment is that the piezoresistive sensing functional material used is reduced graphene oxide (rGO); and the piezoelectric sensing functional material is nano zinc oxide.

[0092] Using quasi-static 33 / d 31The piezoelectric strain coefficient d of the rGO / ZnO piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton after polarization was tested by the measuring instrument 33 -25pC / N,d 31 The sensor resistivity changes under static strain under three-point bending conditions in the span of a simply supported beam system with a sensitivity of 211 and a linearity of 0.98. The sensor voltage change sensitivity under dynamic strain is 220 and the linearity is 0.99. It can sensitively sense structural strains in the range of 0-60%. A 2kHz dynamic pressure (2.44kPa) was applied to the sensor for a cyclic stability test, and the corresponding output voltage was recorded by a static / dynamic signal acquisition instrument. After 5000 cycles, the output voltage of the sensor was almost constant during the entire stability test, and the performance did not decrease. The entire sensor still maintained its integrity, and the surface flexible seal was not damaged.

[0093] Table 1 Comparison results of static / dynamic three-dimensional microcrack sensor performance tests in the embodiments

[0094]

[0095]

[0096] Table 1 shows the comparative results of the static / dynamic three-dimensional microcrack sensor performance tests in the above three embodiments. According to the above data analysis, the performance of the static / dynamic three-dimensional microcrack sensors prepared in the three embodiments of the present invention is superior to that of the sensors prepared in the existing patents CN105953821B, CN113074622A and CN111721192B.

[0097] Embodiment 4

[0098] This embodiment provides a static and dynamic three-dimensional micro-crack extension sensor, which is prepared by using the static and dynamic three-dimensional micro-crack extension sensor preparation method described in any of the above embodiments.

[0099] like Figure 2 As shown, the static and dynamic three-dimensional microcrack extension sensor described in this embodiment includes a piezoresistive / piezoelectric sensing three-dimensional microcrack functional layer 1, a three-dimensional microcrack 2, a packaging layer 3 and an electrode 4. Among them, the piezoresistive / piezoelectric sensing three-dimensional microcrack functional layer 1 contains top / bottom electrodes. It is connected to the electrode static / dynamic signal acquisition system through the wires connected to the top / bottom electrodes.

[0100] The static and dynamic three-dimensional microcrack extension sensor of this embodiment introduces piezoresistive and piezoelectric functional materials at the same time to avoid information loss caused by single-mode sensors during structural monitoring; the piezoresistive / piezoelectric sensing functional material dispersion is attached to the flexible fiber matrix and subjected to pre-stretching and microwave treatment to form a piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton, the fiber structure of the fiber cloth is used to form a functional material skeleton, and the flexible fiber cloth matrix is ​​removed by microwave ablation, the elastomer can pass through the skeleton gap and interweave with the skeleton, ensuring that the sensor has sufficient mechanical stability when external force acts, avoiding the separation of the sensor due to differences in mechanical properties between the sensing functional layer and the flexible fiber cloth matrix or between the sensing functional layer and the elastomer, resulting in mechanical instability of the sensor. The problem of poor performance is solved. At the same time, removing the flexible fiber cloth matrix is ​​conducive to improving sensitivity. Small pre-stretching strain can produce three-dimensional microcracks, so that the final sensor can respond to small external disturbances. The change in the spacing between many three-dimensional microcracks causes the change in contact resistance. At the same time, after microwave ablation removes the fiber, the sensing functional material is in a three-dimensional curled tube shape. Again, microwave ablation removes the fiber cloth, and filling it with an elastomer further avoids the debonding of the functional material and the fiber cloth under static and dynamic loads, causing sensor failure. The triple action makes the static and dynamic three-dimensional microcrack extension sensor have higher sensitivity, solving the problem that the cracks in the crack sensor sensing layer are generally two-dimensional planar structures, which limits the improvement of sensor sensitivity. The final sensor has both high piezoresistive and piezoelectric dual-mode sensitivity and flexibility.

[0101] The static / dynamic three-dimensional micro-crack extension sensor of this embodiment can be flexibly bent at 0-180°. The sensor can be pasted on the surface or inside of the structure. The flexibility of the film enables it to flexibly adapt to working surfaces of various shapes, such as suspension bridge cables, special-shaped steel structures, etc. At the same time, it has high static / dynamic dual-mode sensitivity, can respond sensitively to tiny disturbances, and can monitor the displacement or strain changes of the structure in the full frequency domain.

[0102] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a static and dynamic three-dimensional microcrack extension sensor, characterized in that: include: Prepare a piezoresistive / piezoelectric sensing functional material dispersion, and attach it to the surface of a fiber cloth substrate to obtain a piezoresistive / piezoelectric sensing fiber cloth; wherein the process of preparing the piezoresistive / piezoelectric sensing functional material dispersion is: prepare a piezoelectric functional material precursor solution; use an ultrasonic surfactant method to mix and disperse a material having a piezoresistive function in the piezoelectric functional material precursor solution to obtain a piezoresistive / piezoelectric sensing functional material dispersion; Pre-stretching the piezoresistive / piezoelectric sensing fiber cloth to generate three-dimensional microcracks, and obtain the piezoresistive / piezoelectric sensing three-dimensional microcrack fiber cloth; specifically, the piezoresistive / piezoelectric sensing fiber cloth is clamped on a stretching fixture and pre-stretched using a material stretching testing machine, the stretching rate is set, the pre-stretching strain is 7%, the stretching process lasts for a set time, and the set time is maintained after the stretching is completed, to obtain the piezoresistive / piezoelectric sensing three-dimensional microcrack fiber cloth; Microwave ablation of piezoresistive / piezoelectric sensing three-dimensional microcrack fiber cloth, removing the fiber cloth matrix, forming a three-dimensional curled skeleton, and obtaining a piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton; Conductive layers are coated on both sides of the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton to form electrodes; The piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton with electrodes formed on the surface is polarized; specifically: a conductor with a set thickness and an area equal to the area of ​​the coated silver paste is stacked on the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton, and placed between the point contact electrode and the bottom electrode of the polarization device for polarization treatment; The piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton is encapsulated with an elastomer, and the elastomer can pass through the skeleton gaps and interweave with the skeleton to obtain a static and dynamic three-dimensional microcrack extension sensor.

2. The method for preparing a static and dynamic three-dimensional microcrack extension sensor according to claim 1, characterized in that: The conductive layers coated on both sides of the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton are conductive silver paste.

3. The method for preparing a static and dynamic three-dimensional microcrack extension sensor according to claim 1, characterized in that: The piezoresistive functional material is one or a mixture of CNT, GO, GO-grafted carbon fiber, GO-grafted carbon nanofiber, and GnP.

4. The method for preparing a static and dynamic three-dimensional microcrack extension sensor according to claim 1, characterized in that: The piezoelectric functional material is a PZT precursor / powder, a nano ZnO precursor / powder or an aluminum nitride powder; Or the fiber cloth matrix is ​​synthetic fiber fabric or cotton cloth.

5. The method for preparing a static and dynamic three-dimensional microcrack extension sensor according to claim 1, characterized in that: Before the conductive layers are coated on both sides of the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton, the following steps are also included: Cleaning piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton.

6. The method for preparing a static and dynamic three-dimensional microcrack extension sensor according to claim 1, characterized in that: After the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton with electrodes formed on the surface is polarized, it also includes: Removing silicone oil from the surface of the piezoresistive / piezoelectric sensing three-dimensional microcrack functional skeleton.

7. A static and dynamic three-dimensional micro-crack extension sensor, characterized in that: The sensor is prepared by the method for preparing a static and dynamic three-dimensional microcrack extension sensor as described in any one of claims 1 to 6.

8. A structural monitoring device comprising the static and dynamic three-dimensional micro-crack extension sensor according to claim 7.

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