Preparation method of Ni / Fe3O4 composite nano three-dimensional array strain sensor based on tunneling effect and the sensor

Abstract

The present application relates to a preparation method of a Ni / Fe3O4 composite nano three-dimensional array strain sensor based on the tunneling effect and the sensor. The preparation method includes the steps of: preparing a PDMS base layer through a spin coater; spraying a nano Pt particle conductive layer with a certain thickness on the PDMS base layer using a sputtering coater; evaporating and pasting a copper conductive tape on the PDMS base layer as an electrode; depositing nickel nanowires; depositing a nickel nanowire array on the surface of the PDMS base layer sprayed with the nano Pt electron layer, and deviating the deposition position of the nickel nanowire array from the central axis in the width direction of the PDMS base layer; growing Fe3O4 nanoparticles on the surface of the nickel nanowire array to form a Ni / Fe3O4 composite nano three-dimensional array sensing layer; encapsulating the Ni / Fe3O4 composite nano three-dimensional array strain sensing layer. The present application can respond to triple anisotropic strain signals, has accurate decoupling characteristics, and has the ability to detect multi-dimensional strain amplitudes and directions.

Description

Technical Field

[0001] The present application relates to the technical field of tunnel detectors, and particularly relates to a preparation method and a sensor of a Ni / Fe3O4 composite nano three-dimensional array strain sensor based on the tunneling effect. Background Art

[0002] Tunnels usually bear complex geological, environmental and traffic loads. Tunnel construction faces various uncertain factors, such as geological conditions, various loads and construction methods, etc., which may all lead to the deformation and damage of the tunnel structure. It is urgent to monitor its strain state. The forms of tunnel strain are diverse, and various strains affect each other, and comprehensive consideration is needed to ensure the safety and stability of the tunnel.

[0003] For the detection of one-dimensional strain of a tunnel, a strain sensor needs to detect the amplitude (or angle) of the tunnel displacement; for the detection of multi-dimensional strain, in addition to the amplitude, the strain sensor also needs to detect the direction of the displacement change. In actual monitoring and analysis, multiple sensors are usually used to measure different forms of strain to obtain comprehensive tunnel health state information. However, at present, strain sensors often lack sufficient sensitivity and cannot provide sufficient sensitivity under low strain, making it difficult to detect minute deformations in real time; there are measurement range limitations, and the measurement range of strain sensors sometimes may not meet the requirements of high-strain applications. Especially in an environment of high-frequency vibration or rapid dynamic changes, strain sensors cannot respond quickly, affecting the accuracy of real-time monitoring results. At the same time, strain sensors often can only monitor one-dimensional or two-dimensional strain and cannot accurately respond to three-dimensional strain; moreover, the coupling effect between different forms of strain sensors is poor, resulting in large deviations in strain monitoring.

[0004] The strain sensors for monitoring tunnel displacement mainly include four types: resistive, capacitive, piezoelectric and triboelectric. Piezoelectric and triboelectric sensors are restricted in the application of tunnel monitoring because they work in a high-frequency environment and the charge transfer speed is fast, resulting in their inability to capture static strain. Considering the multi-dimensional characteristics of the tunnel structure strain, a sensor that can detect anisotropic displacement strain is needed. However, due to structural limitations, it is difficult for capacitive sensors to achieve this. In contrast, resistive sensors are favored by researchers in the field of multi-dimensional displacement strain detection because of their structural diversity. These sensors reflect the structural movement by monitoring the change of the electrical signal and have the advantages of high sensitivity, scalability, fast response, stability, low cost and easy manufacturing. However, how to apply resistive sensors to tunnel detection to solve the above technical problems still requires creative efforts. Summary of the Invention

[0005] We expect to provide a preparation process and a sensor for a three-dimensional strain sensor for tunnels with excellent sensitivity, linearity, accuracy, and good frequency response characteristics by solving the above-mentioned technical problems existing in traditional uniaxial strain sensors, which is convenient for monitoring the multi-dimensional dynamic deformation of tunnel structures.

[0006] In the first aspect, a preparation method for a Ni / Fe3O4 composite nano three-dimensional array strain sensor based on the tunneling effect provided by this application adopts the following technical solutions:

[0007] A preparation method for a Ni / Fe3O4 composite nano three-dimensional array strain sensor based on the tunneling effect includes the steps:

[0008] Prepare a PDMS base layer through a spin coater;

[0009] Spray a 30 - 80 nm thick nano Pt particle conductive layer on the PDMS base layer using a sputtering coater;

[0010] Evaporate and paste copper conductive tapes at both ends in the length direction of the PDMS base layer as electrodes;

[0011] Prepare an ordered array of nickel nanowires through electrochemical deposition;

[0012] Deposit an ordered nickel nanowire array on the surface of the PDMS base layer sprayed with a nano Pt electron layer, and deviate the deposition position of the nickel nanowire array from the central axis in the width direction of the PDMS base layer;

[0013] Grow Fe3O4 nanoparticles on the surface of the nickel nanowire array to form a Ni / Fe3O4 composite nano three-dimensional array sensing layer;

[0014] Encapsulate the Ni / Fe3O4 composite nano three-dimensional array strain sensing layer: Select thermoplastic polyimide resin as the raw material, add a plasticizer and a stabilizer for mixing, and prepare a TPI film through a casting method after mixing and melting. Place the TPI film on the Ni / Fe3O4 composite nano three-dimensional array sensing layer and perform hot press welding to bond and seal the TPI film with the Ni / Fe3O4 composite nano three-dimensional array sensing layer.

[0015] By adopting the above technical solutions, the nano Pt particle conductive layer is the nano platinum particle conductive layer, which can enhance the frequency response characteristics of the sensor, improve the response ability to dynamic strain, and the response time is between 2 - 7 s. The Ni / Fe3O4 composite nano three-dimensional array has high sensing accuracy, and the minimum resolution of its strain detection response reaches 0.2%; Growing Fe3O4 nanoparticles on the surface of the nickel nanowire array improves the sensitivity of the sensor, which can reach more than 300. Use thermoplastic polyimide as the encapsulation layer of the encapsulation film, thermoplastic polyimide is TPI, and PDMS is polydimethylsiloxane.

[0016] In the width direction of the base layer, the deposition position of the nickel nanowire array sensing layer is deviated from the central axis, so that the sensor presents asymmetry in the width direction, and further has the ability to detect the amplitude and direction of in-plane bending strain. The entire sensor has three-dimensional spatial dimensional asymmetry in the three-dimensional spatial structure, can respond to triple anisotropic strain signals, has accurate decoupling characteristics, and has the ability to detect multi-dimensional strain amplitude and direction.

[0017] In addition, the base layer and the encapsulation layer are made of different materials, and the thickness of both can be adjusted, so that an asymmetric structure can be formed in the thickness direction of the sensor; further, this asymmetric structure has anisotropy when responding to out-of-plane bending strain, enabling it to have the ability to detect the amplitude and direction of out-of-plane bending strain.

[0018] Optionally, the step of preparing the PDMS base layer by the spin coating machine includes:

[0019] Weigh the PDMS two-component liquid, select a substrate and clean it with plasma water or absolute ethanol. Place the uniformly stirred PDMS prepolymer in the center of the substrate and spin coat the PDMS prepolymer through a spin coater. Then, put the substrate with the spin-coated PDMS prepolymer into a constant temperature oven for heating and curing.

[0020] By adopting the above technical solution, weigh an appropriate amount of PDMS two-component liquid, namely the curing agent and the silicone rubber main agent, and stir well in a certain proportion to remove air bubbles. Adjust the spin coating speed and time to prepare PDMS films with different thicknesses.

[0021] Optionally, the PDMS base layer after heating and curing is treated with oxygen plasma to increase its surface hydrophilicity.

[0022] By adopting the above technical solution, the surface of the PDMS film is modified by oxygen plasma treatment to increase its surface viscosity. The bonding degree between the base layer, the sensing layer and the encapsulation layer of the Ni / Fe3O4 composite nano three-dimensional array strain sensor prepared by the present invention is good, with good linearity, acid and alkali corrosion resistance, good stability and high reliability.

[0023] Optionally, the steps of preparing nickel nanowires by electrochemical deposition method include:

[0024] Select an anodic aluminum oxide film with regular pore diameter as the deposition template, and sputter a metal back electrode on the back of the anodic aluminum oxide film in a vacuum sputtering chamber. The sputtering time is 5 - 20 min, and the sputtering power is 60 - 250 W;

[0025] Prepare a nickel ion electrolyte solution with a certain concentration, place the anodic aluminum oxide membrane in the nickel ion electrolyte solution, and pass a constant current for electrochemical deposition. Immerse the anodic aluminum oxide membrane of the deposited nickel nanowires in a NaOH solution with a mass fraction of 5-10%, and let it stand at 60-80 °C for 2.5-7 h until the anodic aluminum oxide membrane is completely dissolved to obtain nickel nanowires. Wash the nickel nanowires and place them in absolute ethanol, and use ultrasonic waves to uniformly disperse the nickel nanowires to make a suspension.

[0026] By adopting the above technical solution, AAO, that is, the anodic aluminum oxide membrane, plays a role of a template in the process of preparing nickel nanowires. Its pore distribution is uniform, the pore density is high, and the diameter and length of the pores can be artificially controlled, which enables the AAO template to provide regular pores for the growth of nickel nanowires, thereby preparing nickel nanowires with uniform size and consistent morphology.

[0027] Immerse the deposited nickel nanowire / AAO composite membrane in a NaOH solution with a mass fraction of 5-10%, and let it stand at 60-80 °C for 2.5-7 hours until the AAO template is completely dissolved.

[0028] Optionally, the step of depositing an ordered nickel nanowire array on the surface of the PDMS substrate layer sprayed with a nano-Pt electron layer and deviating the deposition position of the nickel nanowire array from the central axis in the width direction of the PDMS substrate layer includes:

[0029] Place a double-pass polymethyl methacrylate square box container on the PDMS substrate layer, seal the contact part, and then place it in a parallel magnetic field with the magnetic field direction consistent with the width direction of the PDMS substrate layer. Use a pipette to transfer the uniformly dispersed nickel nanosuspension into the double-pass polymethyl methacrylate square box container and let it stand to deposit a highly ordered nickel nanowire array on the PDMS substrate.

[0030] By adopting the above technical solution, the position where the double-pass polymethyl methacrylate square box container is placed at the bottom is the deposition position of the ordered nickel nanowire array of the sensing layer. Use a pipette to transfer the uniformly dispersed nickel nanosuspension into the container and let it stand until the absolute ethanol completely volatilizes, thereby depositing and preparing a highly ordered nickel nanowire array on the PDMS substrate.

[0031] Optionally, use ultrasonic waves to clean the surface of the anodic aluminum oxide membrane;

[0032] Wash the nickel nanowires repeatedly with deionized water and absolute ethanol.

[0033] By adopting the above technical solution, use ultrasonic waves to clean the surface of the AAO anodic membrane to remove impurities and obtain a pure AAO thin film. Wash the nickel nanowires repeatedly with deionized water and absolute ethanol to obtain pure nickel nanowires.

[0034] Optionally, the nickel nanowire array exhibits asymmetry in the direction orthogonal to the stretching plane.

[0035] By adopting the above technical solution, the nickel nano-ordered array sensing layer exhibits asymmetry in the direction orthogonal to the stretching plane, making it anisotropic in the stretching plane and further having the ability to detect the strain amplitudes in different directions within the stretching plane. The nickel nano-ordered array sensing layer has good linearity, reaching more than 95%.

[0036] Optionally, the step of growing Fe3O4 nanoparticles on the surface of the nickel nanowire array to form a Ni / Fe3O4 composite nano three-dimensional array sensing layer includes:

[0037] Adding a mixed solution of ferric chloride hexahydrate and ferrous chloride tetrahydrate to the highly ordered nickel nanowire array deposited in a double-pass polymethyl methacrylate square box container, adding ammonia water to adjust the pH value of the solution to 10 - 12, and a precipitation reaction occurs in the mixed solution, and Fe3O4 nanoparticles adhere and grow on the surface of the nickel nanowire array to form a Ni / Fe3O4 composite nano three-dimensional array sensing layer.

[0038] By adopting the above technical solution, an appropriate amount of ferric chloride hexahydrate (FeCl3·6H2O) and ferrous chloride tetrahydrate (FeCl2·4H2O) with a molar ratio of 2:1 are weighed, and the two are dissolved in plasma water and stirred evenly. Adding an appropriate amount of the mixed solution of ferric chloride hexahydrate (FeCl3·6H2O) and ferrous chloride tetrahydrate (FeCl2·4H2O) to the container deposited with the nickel nanowire array, adding ammonia water (NH3·H2O) to adjust the pH value of the solution to 10 - 12, and a precipitation reaction occurs in the mixed solution, and Fe3O4 nanoparticles adhere and grow on the surface of the nickel nanowire array. After the reaction ends, it is washed with plasma water and absolute ethanol and dried in a vacuum oven to obtain a Ni / Fe3O4 composite nano three-dimensional array. Growing Fe3O4 nanoparticles on the surface of the nickel nanowire array improves the sensitivity of the sensor, which can reach more than 300.

[0039] Optionally, the substrate is selected from any one of glass, quartz, polyethylene terephthalate (PET), and nickel substrate.

[0040] In a second aspect, the present application provides a Ni / Fe3O4 composite nano three-dimensional array strain sensor based on the tunneling effect, using the aforementioned preparation method and adopting the following technical solution:

[0041] A Ni / Fe3O4 composite nano three-dimensional array strain sensor based on the tunneling effect, using the above preparation method, includes: a base layer, a nano thin film layer, a Ni / Fe3O4 composite nano three-dimensional array sensing layer, and a packaging layer.

[0042] By adopting the above technical solution, the sensor base layer and the encapsulation layer are made of different materials, and the thickness of both can be adjusted, and an asymmetric structure can be formed in the thickness direction of the sensor.

[0043] In summary, the present application includes at least one of the following beneficial technical effects:

[0044] 1. The preparation process of the present invention is simple, the preparation cost is low, and the sensor prepared by the present invention can monitor three-dimensional strain, has excellent sensitivity, linearity and accuracy, good frequency response characteristics, and is convenient for monitoring the multi-dimensional dynamic deformation of tunnel structures; at the same time, it has mechanical flexibility, can closely fit the surface of the tunnel structure to be detected, and is not affected by harsh tunnel conditions such as temperature and humidity changes, is resistant to acid and alkali corrosion, has good durability, and has broad application prospects in the field of strain response detection of tunnel construction and operation structures.

[0045] 2. The thickness of the sensor base layer and the encapsulation layer of the Ni / Fe3O4 composite nano three-dimensional array prepared by the invention, and the density of the ordered nickel nanowire array can be adjusted, and the adjustment method is accurate and the process is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is a preparation flow chart showing the Ni / Fe3O4 composite nano three-dimensional array strain sensor of the present application;

[0047] Figure 2 is a SEM image showing the highly ordered nickel nanowire array of the present application;

[0048] Figure 3 is a schematic diagram showing the asymmetric structure of the Ni / Fe3O4 composite nano three-dimensional array strain sensor of the present application;

[0049] Figure 4 is an optical micrograph showing the Ni / Fe3O4 composite nano three-dimensional array of the present application;

[0050] Figure 5 is a sample diagram showing the Ni / Fe3O4 composite nano three-dimensional array strain sensor of the present application;

[0051] Figure 6 is a schematic diagram showing the asymmetric structure in the thickness direction of the Ni / Fe3O4 composite nano three-dimensional array strain sensor of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] Next, the technical solutions in the embodiments of the present application will be described in conjunction with the attached Figures 1-6 , in the embodiments of the present application.

[0053] To help those in the technical field better understand the present invention, specific embodiments will be described in detail below in conjunction with the accompanying drawings. It should be noted that the described embodiments only represent a part of the present invention, not all of it. All other implementation manners obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts should fall within the protection scope of the present invention.

[0054] In addition, in this article, when a certain element is described as "disposed on" another element, it can be directly disposed, or there may be an intermediate element. When a certain element is described as "connected to" another element, it can also be directly connected, or there may be an intermediate connecting member.

[0055] Furthermore, terms such as "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc. used in the text are only for the convenience of description and simplification of the explanation, and do not mean that the device or element referred to must have a specific orientation or position.

[0056] Unless otherwise specifically stated, all technical and scientific terms used in this article are the same as those commonly understood by those skilled in the art. The terms used in the text are only for describing specific embodiments and are not intended to limit the present invention. The term "and / or" means any combination of the listed items.

[0057] Design an ordered array of Ni nanowires based on the tunneling effect conduction mechanism. The theoretical basis of the tunneling effect conduction mechanism is as follows:

[0058] R_t = V / AJ = (h^2 d) / (Ae^2 √2mγ) exp(4πd / h √2mγ)

[0059] Where R_t represents the tunneling resistance, A is the cross-sectional area of the tunneling junction in the transverse direction, V represents the electrode potential, J is the tunneling current density of the tunnel, d represents the adjacent distance between nanomaterials, e is the electron charge, h is the Planck constant, γ is the height of the non-conductive energy barrier, and m is the mass of a single electron.

[0060] The tunneling effect means that when the distance between conductive nanomaterials is very small but non-contact, electrons will undergo quantum tunneling effect, so that non-conductive materials also have the ability to conduct electricity. Based on this, the ordered array of Ni nanowires (i.e., nickel nanowire array) prepared in the present invention will have a tunneling effect in the strain stretching plane of the Ni nanowire sensing array, resulting in a change in resistance. Further due to the tunneling effect, in the direction orthogonal to the strain stretching, the relative change rate of the resistance of the sensing layer of the Ni nanowire sensing array is different. This difference endows the sensing layer with the decoupling characteristic of the response signal to the strain direction in the stretching plane, and further the sensor has the ability to detect the strain amplitude and direction in the stretching plane.

[0061] The following are specific embodiments. It should be noted that these embodiments are relatively preferred examples of the present invention for those skilled in the art to understand the present invention, but the present invention is not limited to these embodiments.

[0062] As Figure 1 shown, a preparation method of a Ni / Fe3O4 composite nano three-dimensional array strain sensor based on the tunneling effect includes preparing a PDMS flexible base layer, spraying a nano thin film layer (i.e., a nano Pt particle conductive layer), preparing an ordered array of nickel nanowires and growing Fe3O4 nanoparticles on its surface, and finally encapsulating the ordered array of nickel nanowires with Fe3O4 nanoparticles grown thereon with TPI. PDMS is polydimethylsiloxane, and thermoplastic polyimide is TPI.

[0063] A preparation method of a Ni / Fe3O4 composite nano three-dimensional array strain sensor based on the tunneling effect in this embodiment includes the following steps:

[0064] Step S1: Prepare a PDMS base layer through a spin coater: Weigh an appropriate amount of PDMS two-component liquid (curing agent and silicone rubber main agent), and stir thoroughly at a ratio of curing agent to silicone rubber main agent of 1:10 to remove air bubbles. Select a glass substrate and clean it with plasma water or absolute ethanol. Place the uniformly stirred PDMS prepolymer at the center of the substrate, set the rotation speed of the spin coater to 150 r / min, and the time to 5 min. Place the substrate with PDMS spin-coated on it in an 80°C constant temperature oven and heat it for 0.5 h for curing. After curing, modify the surface of the PDMS film by oxygen plasma treatment to prepare the PDMS base layer.

[0065] Step S2: Use a sputtering coater to spray a 30-nm-thick nano Pt particle conductive layer on the PDMS base layer.

[0066] Step S3: Evaporate and paste copper conductive tapes at both ends in the length direction of the PDMS base layer as electrodes.

[0067] Step S4. Preparation of nickel nanowires by electrochemical deposition method: Select an anodic aluminum oxide (AAO) membrane with a thickness of 100 µm and a pore size of 250 nm as the deposition template. Sputter a certain thickness of metal back electrode on the back of the AAO membrane in a vacuum sputtering chamber. Set the sputtering time to 20 min and the sputtering power to 150 W. Prepare a 0.5 mol / L nickel chloride (NiCl) electrolyte solution, place the AAO anode membrane in the NiCl electrolyte solution, and perform electrochemical deposition with a constant current of 7 mA. Set the deposition time to 1.5 h. Immerse the deposited nickel nanowire / AAO composite membrane in a 10% mass fraction of NaOH solution and let it stand at 75 °C for 7 h until the AAO template is completely dissolved, thereby obtaining nickel nanowires. Wash the nickel nanowires and place them in absolute ethanol, and use ultrasonic waves to uniformly disperse the nickel nanowires to make a suspension.

[0068] Step S5. Deposit an ordered Ni nanowire array on the surface of the PDMS substrate layer sprayed with a nano-Pt electron layer: Place a double-pass polymethyl methacrylate (PMMA) square box container on the PDMS substrate layer and seal the contact part. Place the double-pass polymethyl methacrylate (PMMA) square box container in a parallel magnetic field, and the magnetic field direction is consistent with the width direction of the PDMS substrate layer film. Use a pipette to transfer the uniformly dispersed nickel nanosuspension into the double-pass polymethyl methacrylate (PMMA) square box container, and let it stand until the absolute ethanol completely evaporates, thereby depositing and preparing a highly ordered Ni nanowire array on the PDMS substrate. As Figure 2 , the SEM image of the Ni nanowire array shows a highly ordered arrangement structure.

[0069] Furthermore, as Figure 3 , in the width direction of the PDMS substrate layer, the deposition position of the Ni nanowire array sensing layer deviates from the central axis of the PDMS substrate layer by a certain distance, so that the sensor shows asymmetry in the width direction and further has the ability to detect the amplitude and direction of in-plane bending strain.

[0070] Step S6. Growing Fe3O4 nanoparticles on the surface of the nickel nanowire array: Weigh an appropriate amount of 20 g each of ferric chloride hexahydrate (FeCl3·6H2O) and ferrous chloride tetrahydrate (FeCl2·4H2O) with a molar ratio of 2:1, dissolve the two in 1 L of deionized water, and stir evenly. Add 50 ml of the mixed solution of ferric chloride hexahydrate (FeCl3·6H2O) and ferrous chloride tetrahydrate (FeCl2·4H2O) into the double-pass polymethyl methacrylate (PMMA) square box container deposited with the nickel nanowire array, add ammonia water (NH3·H2O) to adjust the pH value of the solution to 11, and a precipitation reaction occurs in the mixed solution, and Fe3O4 nanoparticles adhere and grow on the surface of the nickel nanowire array. After the reaction is completed, wash with deionized water and absolute ethanol, and dry in a vacuum oven to obtain the Ni / Fe3O4 composite nano three-dimensional array, as Figure 4 .

[0071] Step S7. Encapsulating the Ni / Fe3O4 composite nano three-dimensional array sensing layer: Select thermoplastic polyimide resin as the raw material, add plasticizer and stabilizer for mixing, and prepare a TPI film by casting method after melting and kneading. Place the TPI film on the Ni / Fe3O4 composite nano three-dimensional array sensing layer, and perform thermocompression welding under certain temperature and pressure to bond and seal it on the surface of the Ni / Fe3O4 composite nano three-dimensional array sensing layer. The plasticizer can be selected from any one of phthalate esters, aliphatic dibasic acid esters or polyethylene glycol (PEG). The stabilizer can be any one of triethanolamine, antioxidant or ultraviolet absorber. Thus, a structurally complete Ni / Fe3O4 composite nano three-dimensional array sensor is obtained, as Figure 5 .

[0072] Furthermore, as Figure 6 , the base layer and the encapsulation layer of the sensor are made of different materials, and the thickness of the base layer is greater than that of the encapsulation layer, so an asymmetric structure can be formed in the thickness direction of the sensor; further, this asymmetric structure has anisotropy when responding to out-of-plane bending strain, enabling it to have the ability to detect the amplitude and direction of out-of-plane bending strain.

[0073] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0074] (1). The bonding degree between the base layer, the sensing layer and the encapsulation layer of the Ni / Fe3O4 composite nano three-dimensional array strain sensor prepared by the present invention is good, it has good linearity, is resistant to acid and alkali corrosion, has good stability and high reliability.

[0075] (2) The thicknesses of the base layer and the encapsulation layer, and the density of the ordered nickel nanowire array of the Ni / Fe₃O₄ composite nano three-dimensional array strain sensor prepared by the present invention can all be adjusted, and the adjustment method is precise and the process is simple.

[0076] (3) In the Ni / Fe₃O₄ composite nano three-dimensional array strain sensor prepared by the present invention based on the tunneling effect, the nano-Pt particle conductive layer enhances the frequency response characteristics of the sensor, improves the response ability to dynamic strain, and the response time is 2 - 7 s; the Ni / Fe₃O₄ composite nano three-dimensional array strain sensing accuracy is high, and the minimum resolution of its strain detection response reaches 0.2%; the growth of Fe₃O₄ nanoparticles on the surface of the nickel nanowire array improves the sensitivity of the sensor, which can reach more than 300.

[0077] (4) The Ni / Fe₃O₄ composite nano three-dimensional array strain sensor prepared by the present invention based on the tunneling effect has asymmetry in the three-dimensional space structure, can respond to triple anisotropic strain signals, has precise decoupling characteristics, and has the ability to detect multi-dimensional strain amplitude and direction.

[0078] The embodiments of the present application also disclose a Ni / Fe₃O₄ composite nano three-dimensional array strain sensor using the preparation method of the above-mentioned Ni / Fe₃O₄ composite nano three-dimensional array strain sensor based on the tunneling effect.

[0079] A Ni / Fe₃O₄ composite nano three-dimensional array strain sensor based on the tunneling effect includes a base layer, a nano thin film layer, a Ni / Fe₃O₄ composite nano three-dimensional array sensing layer, and an encapsulation layer.

[0080] The above are all the preferred embodiments of the present application. The protection scope of the present application is not limited by this. Therefore, all equivalent changes made according to the structure, shape, and principle of the present application should be covered within the protection scope of the present application.

Claims

1. A method for preparing a Ni / Fe3O4 composite nano three-dimensional array strain sensor based on tunneling effect, characterized in that: Includes steps: Prepare the PDMS base layer by a gel spinning machine; Use a gold spraying device to spray a 30-80 nm thick nano Pt particle conductive layer on the PDMS substrate layer; Copper conductive strips are deposited and pasted on both ends of the PDMS substrate layer in the length direction as electrodes; Well-aligned nickel nanowires were prepared by electrochemical deposition; An ordered nickel nanowire array is deposited on the surface of a PDMS substrate layer sprayed with a nano-Pt particle conductive layer, and the deposition position of the nickel nanowire array is deviated from the central axis in the width direction of the PDMS substrate layer; Growing Fe3O4 nanoparticles on the surface of the nickel nanowire array to form a Ni / Fe3O4 composite nano three-dimensional array sensing layer; Encapsulating the Ni / Fe3O4 composite nano three-dimensional array strain sensing layer: using thermoplastic polyimide resin as a raw material, adding a plasticizer and a stabilizer to mix, kneading and melting, preparing a TPI film by a casting method, placing the TPI film on the Ni / Fe3O4 composite nano three-dimensional array sensing layer, and performing hot pressing welding to bond and seal the TPI film to the Ni / Fe3O4 composite nano three-dimensional array sensing layer; The steps of preparing nickel nanowires by electrochemical deposition include: An anodized aluminum film with regular pores is selected as a deposition template, and a layer of metal back electrode is sputtered on the back of the anodized aluminum film in a vacuum sputtering chamber. The sputtering time is 5-20 minutes and the sputtering power is 60-250W. A nickel ion electrolyte solution with a certain concentration is prepared, and an anodized aluminum film is placed in the nickel ion electrolyte solution, a constant current is passed for electrochemical deposition, and the anodized aluminum film on which the deposited nickel nanowires are made is immersed in a 5-10% by mass NaOH solution, and allowed to stand at 60-80° C. for 2.5-7 hours until the anodized aluminum film is completely dissolved to obtain nickel nanowires, and the nickel nanowires are cleaned and placed in anhydrous ethanol, and the nickel nanowires are uniformly dispersed by ultrasound to form a suspension; The step of depositing an ordered nickel nanowire array on the surface of the PDMS substrate layer sprayed with a nano Pt particle conductive layer, and deviating the deposition position of the nickel nanowire array from the central axis in the width direction of the PDMS substrate layer comprises: A double-pass polymethyl methacrylate square box container is placed on the PDMS substrate layer, and the contact part is sealed. It is then placed in a parallel magnetic field with the direction of the magnetic field consistent with the width direction of the PDMS substrate layer. A pipette is used to transfer the evenly dispersed nickel nanosuspension into the double-pass polymethyl methacrylate square box container and let it stand to deposit a highly ordered nickel nanowire array on the PDMS substrate.

2. The method for preparing a Ni / Fe3O4 composite nano three-dimensional array strain sensor based on tunneling effect according to claim 1, characterized in that: The step of preparing the PDMS base layer by a gelling machine comprises: Weigh the PDMS two-component liquid, select the substrate and clean it with plasma water or anhydrous ethanol, place the evenly stirred PDMS prepolymer at the center of the substrate and spin-coat the PDMS prepolymer using a coater, and then place the substrate spin-coated with the PDMS prepolymer in a constant temperature oven for heating and curing.

3. The method for preparing the Ni / Fe3O4 composite nano three-dimensional array strain sensor based on the tunnel effect according to claim 2 is characterized in that: The PDMS substrate layer after heating and curing is modified by oxygen plasma to increase the surface hydrophilicity.

4. The method for preparing a Ni / Fe3O4 composite nano three-dimensional array strain sensor based on tunneling effect according to claim 1, characterized in that: Use ultrasonic waves to clean the surface of anodized aluminum film; The nickel nanowires were washed repeatedly with deionized water and anhydrous ethanol.

5. The method for preparing the Ni / Fe3O4 composite nano three-dimensional array strain sensor based on the tunnel effect according to claim 1, characterized in that: The nickel nanowire array exhibits asymmetry in the direction orthogonal to the stretching surface.

6. The method for preparing a Ni / Fe3O4 composite nano three-dimensional array strain sensor based on tunneling effect according to claim 1, characterized in that: The step of growing Fe3O4 nanoparticles on the surface of the nickel nanowire array to form a Ni / Fe3O4 composite nano three-dimensional array sensing layer comprises: A mixed solution of ferric chloride hexahydrate and ferrous chloride tetrahydrate is added to a highly ordered nickel nanowire array deposited in a double-pass polymethyl methacrylate square box container, and ammonia water is added to adjust the pH of the solution to 10-12. The mixed solution undergoes a precipitation reaction, and Fe3O4 nanoparticles adhere and grow on the surface of the nickel nanowire array to form a Ni / Fe3O4 composite nano three-dimensional array sensing layer.

7. The method for preparing a Ni / Fe3O4 composite nano three-dimensional array strain sensor based on tunneling effect according to claim 2, characterized in that: The substrate can be any one of glass, quartz, polyethylene terephthalate (PET), and nickel substrate.

8. A Ni / Fe3O4 composite nano three-dimensional array strain sensor based on tunneling effect, using the preparation method according to any one of claims 1 to 7, characterized in that: It includes a base layer, a nano film layer, a Ni / Fe3O4 composite nano three-dimensional array sensing layer and a packaging layer.

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