Piezoelectric-piezoresistive collaborative mechanism-based sensor array and preparation method and application thereof

Abstract

The invention relates to a piezoelectric-piezoresistive collaborative mechanism-based sensor array and a preparation method and application thereof. The sensor array comprises a flexible packaging substrate layer, a piezoelectric layer, a piezoelectric layer and a piezoelectric layer which are sequentially integrated from bottom to top, the bottom electrode layer is composed of a stretchable silver electrode array subjected to silk-screen printing and serves as a lower electrode of the piezoelectric sensor; the piezoelectric functional layer is composed of a lead zirconate titanate-glass fiber composite film, and the piezoelectric functional layer is subjected to corona polarization treatment; the piezoresistive sensing layer is formed by spraying a polyvinylpyrrolidone modified carbon material dispersion liquid, the piezoresistive sensing layer is used as an upper electrode of the piezoelectric sensor, the piezoresistive sensing layer is directly deposited on the surface of the piezoelectric functional layer, and the piezoresistive sensing layer and the piezoelectric functional layer pass through a common electrode; and packaging a protection layer on the top layer. Compared with the prior art, the method has the advantages of high sensitivity, wide linear range and multi-parameter synchronous detection capability, high-resolution real-time deformation identification can be realized, and key technical support is provided for high-precision sensing application such as profile inversion.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and in particular to a sensor array based on a piezoelectric-piezoresistive synergistic mechanism, and a preparation method and application thereof. Background Art

[0002] With the rapid development of aerospace, wind power, and other fields, the demand for safety and reliability monitoring of complex mechanical structures (such as aircraft and wind turbine blades) is growing. Existing structural health monitoring (SHM) technologies often rely on intrusive sensors, requiring destructive modifications to the structure (such as drilling holes), resulting in reduced aerodynamic performance and increased weight (e.g., CN119845479A).

[0003] Compared to traditional non-contact measurement methods such as optical or laser sensors, flexible strain sensors offer advantages such as strong interference immunity, adaptability to contoured surfaces, and ease of multi-point deployment. They are particularly suitable for reconstructing strain fields on complex curved structures. However, most current sensors focus solely on static strain amplitude and fail to reflect the response characteristics of structures under dynamic loads. Inspired by the lateral line system of aquatic animals, combining the responsiveness of piezoelectric sensors to strain rate and direction with the sensitivity of piezoresistive sensors to loading state, these sensors can be integrated into large-area arrays, enabling coupled acquisition of full-field static and dynamic deformation information from mechanical structures. Currently, existing multi-type sensors are typically arranged coplanarly or stacked vertically, but they still face numerous challenges in miniaturization and integration, including manufacturing process incompatibilities, complex signal fusion, and poor array consistency. Furthermore, the traditional method of sequentially integrating sensor units to fabricate arrays is inefficient and difficult to scale up. While micro-nanofabrication techniques (such as photolithography) offer high precision and high processing speed, they suffer from poor material compatibility and high cost. Therefore, it is urgent to develop new structural designs and advanced manufacturing processes to achieve optimized coordination of multiple types of sensors in terms of sensitivity, linearity, stability and other performance, and to promote the implementation of large-area, highly integrated flexible sensor arrays for structural health monitoring in high-end equipment such as aerospace equipment and wind power equipment.

[0004] While some research attempts to combine piezoelectric and piezoresistive mechanisms, existing technologies still have numerous drawbacks. For example, a piezoelectric-piezoresistive flexible sensor (e.g., CN113267275A) has a complex fabrication process involving multiple bonding and packaging steps, making efficient mass production difficult. Furthermore, this sensor fails to adequately address the mutual interference between the piezoelectric and piezoresistive signals, limiting its performance and reliability in practical applications.

[0005] In summary, there is an urgent need for a new sensor technology that can monitor complex mechanical structures without destroying the structure itself, and solve the problems of large size, low sensitivity and unstable interface in existing technologies. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects of the above-mentioned existing technologies and provide a sensor array based on the piezoelectric-piezoresistive synergistic mechanism and its preparation method and application, which can monitor complex mechanical structures without destroying the structural body, and has high sensitivity, wide linear range and multi-parameter synchronous detection capabilities, effectively solving key problems such as large device size and unstable interface connection in traditional hybrid systems.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A first aspect of the present invention provides a sensor array based on a piezoelectric-piezoresistive synergistic mechanism, comprising:

[0009] a flexible encapsulation base layer composed of cured polyurethane;

[0010] The bottom electrode layer, consisting of a screen-printed stretchable silver electrode array, serves as the lower electrode of the piezoelectric sensor;

[0011] A piezoelectric functional layer is composed of a lead zirconate titanate-glass fiber composite film, and the piezoelectric functional layer is subjected to corona polarization treatment;

[0012] The piezoresistive sensing layer is formed by ultrasonic spraying a dispersion of a carbon material modified with polyvinyl pyrrolidone. The piezoresistive sensing layer serves as the upper electrode of the piezoelectric sensor. The piezoresistive sensing layer is directly deposited on the surface of the piezoelectric functional layer. The piezoresistive sensing layer and the piezoelectric functional layer are coupled by a circuit for synchronous acquisition of piezoelectric-piezoresistive signals via a common electrode.

[0013] The top encapsulation protection layer is made of spin-coated polyurethane and cured.

[0014] A second aspect of the present invention provides a method for preparing a sensor array based on the piezoelectric-piezoresistive synergistic mechanism as described above, comprising the following steps:

[0015] S1: Using ultrasonic spraying technology to deposit lead zirconate titanate sol-gel precursor solution on the surface of glass fiber fabric, followed by drying and annealing to form a perovskite phase lead zirconate titanate-glass fiber composite film;

[0016] S2: The perovskite phase lead zirconate titanate-glass fiber composite film is subjected to corona poling treatment to orient the internal dipoles and obtain a piezoelectric functional layer;

[0017] S3: Mix the polyurethane components A and B after vacuum degassing, and spin-coat them on a substrate to form a flexible encapsulation base layer, and screen-print a bottom electrode layer on the flexible encapsulation base layer;

[0018] S4: Spin-coating a layer of polyurethane on the bottom electrode layer, placing the lead zirconate titanate-glass fiber composite film after corona poling treatment on it, and coating and curing to form a piezoelectric functional layer;

[0019] S5: spraying a dispersion of a carbon material modified with polyvinyl pyrrolidone onto the surface of the piezoelectric functional layer by ultrasonic spraying to form a piezoresistive sensing layer;

[0020] S6: Stretchable silver wires were prepared by screen printing on the piezoresistive sensing layer, and polyurethane was spin-coated on the substrate and cured to form a top encapsulation protective layer.

[0021] Furthermore, in S1, the specific parameters of the ultrasonic spraying process include:

[0022] The operating frequency of the ultrasonic atomizing nozzle was set to 80kHz, and compressed air with a pressure of 0.5-1MPa was used as the guide airflow;

[0023] The glass fiber fabric is fixed on the substrate by a vacuum pump, and the PZT precursor solution is loaded into the ultrasonic sprayer;

[0024] The nozzle movement speed was set to 20 mm / s, the liquid flow rate was controlled between 5-15 μL / s, the spraying width was set to 8 mm, and the spraying process was repeated 5-15 times.

[0025] Furthermore, the annealing method is: heating the sprayed film at 150° C. for 10 minutes, and then annealing at 550-700° C. to form a perovskite phase structure.

[0026] Furthermore, in S2, the specific conditions of the corona polarization treatment include:

[0027] The perovskite phase lead zirconate titanate-glass fiber composite film is placed in a corona poling device and polarized by corona discharge to align the dipoles inside the piezoelectric material, thereby enhancing the piezoelectric effect and improving the performance of the piezoelectric functional layer.

[0028] The voltage of the corona polarization treatment is 2-5 kV, the polarization temperature is controlled between 25-40° C., and the relative humidity is maintained in the range of 30%-60%.

[0029] Furthermore, in S3, the mixing mass ratio of the polyurethane components A and B is 1:1, and the vacuum degassing time is not less than 30 minutes;

[0030] The parameters for spin coating polyurethane are: rotation speed 700 rpm, spin coating time 30 seconds to ensure good flatness and adhesion of the flexible encapsulation substrate layer;

[0031] When screen printing the bottom electrode layer, the stretchable silver paste used has a solid content of 60wt%-70wt% and a viscosity of 10,000-15,000mPa·s. The printed silver electrode array has a line width of 200-500μm and a spacing of 300-800μm. After drying at a temperature of 120-150°C for 10-20 minutes, the silver electrode has excellent conductivity and stretchability, meeting the requirements of the bottom electrode of the piezoelectric sensor.

[0032] Furthermore, in S4, the parameters for spin coating the polyurethane are a rotation speed of 700 rpm and a spin coating time of 30 seconds, to ensure that a uniform polyurethane film is formed on the surface of the bottom electrode layer;

[0033] A lead zirconate titanate-glass fiber composite film that has been corona polarized is quickly placed on it. The composite film is required to fit tightly with the polyurethane film without bubbles and wrinkles. It is then cured at room temperature for 1 hour, and then heated to 60°C for 2-3 hours to allow the polyurethane to completely cover and cure to form a stable piezoelectric functional layer, ensuring good adhesion and electrical contact between the piezoelectric functional layer and the bottom electrode layer.

[0034] Furthermore, in S5, the specific ratio of the polyvinyl pyrrolidone-modified carbon material dispersion is: 5-20 mg / ml of graphene, 5-15 mg / ml of carbon black, and 5-15 mg / ml of polyvinyl pyrrolidone dispersed in alcohol;

[0035] The carbon material dispersion is ultrasonically treated for 1 hour before use and stirred for 1-2 days to ensure sufficient interaction between polyvinyl pyrrolidone and the carbon material;

[0036] The specific parameters of the ultrasonic spraying are a nozzle movement speed of 20 mm / s, a liquid flow rate of 5-15 μL / s, a spray width of 5 mm, and the spraying process is repeated 15-30 times to form a uniform and dense piezoresistive sensing layer. After spraying, the layer is dried at room temperature for 10-20 minutes to ensure that the piezoresistive sensing layer has good conductivity and mechanical properties, and is tightly combined with the piezoelectric functional layer to achieve efficient circuit coupling.

[0037] Furthermore, in S6, when screen printing is used to prepare the stretchable silver wire, the silver paste used has a solid content of 60wt%-70wt% and a viscosity of 10,000-15,000mPa·s. The printed silver wire has a line width of 300-600μm and a spacing of 400-900μm. After printing, the wire is dried at 120-150°C for 10-20 minutes to ensure that the wire has good conductivity and stretchability.

[0038] When spin-coating polyurethane and curing it to form the top encapsulation protective layer, the mixing mass ratio of polyurethane A and B components is 1:1, the vacuum degassing time is not less than 30 minutes, the spin coating speed is 700 rpm, the spin coating time is 30 seconds, and then it is cured at room temperature for 2 hours, and then heated to 60°C for curing for 2-3 hours, so that the top encapsulation protective layer has good sealing and flexibility, effectively isolates environmental interference, and protects the stable operation of the entire sensor array.

[0039] The second aspect of the present invention provides an application of a sensor array based on the piezoelectric-piezoresistive synergistic mechanism as described above, in which the sensor array based on the piezoelectric-piezoresistive synergistic mechanism is attached to the surface of a deformable body, and static strain monitoring, dynamic strain identification, and deformation path tracking are achieved by synchronously collecting the resistance change of the piezoresistive sensing layer and the output voltage of the piezoelectric functional layer.

[0040] Furthermore, the deformable body includes one of a wind turbine blade, a spacecraft skin, and a robotic arm curved surface structure.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. The present invention provides a new integration strategy for the integration of piezoelectric and piezoresistive sensors, effectively solving key problems in traditional hybrid systems such as bulky devices and unstable interface connections.

[0043] 2. The present invention innovatively applies low-cost and simple ultrasonic spraying technology to the preparation process of large-area sensor arrays, providing a new path and new ideas for efficient integrated sensor units.

[0044] 3. The piezoresistive sensor prepared by the present invention exhibits an excellent single-segment linear resistance response within an ultra-wide strain range of 0.001% to 45%, and the output voltage of the piezoelectric sensor also shows a good linear relationship within the strain rate range of 2.01 mm / s to 70.37 mm / s.

[0045] 4. The sensor developed by the present invention has the ability to perceive the deformation path in real time, and can realize the accurate tracking and monitoring of the structural strain state. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a flow chart of the preparation of the piezo-piezoresistive multimodal sensing array in the embodiment.

[0047] Figure 2 This is a characterization diagram of hydrogen bond formation of PVP in the piezoresistive layer in Example 1

[0048] Figure 3 The cross-section and surface transmission electron microscope images of the piezoresistive layer prepared in Example 1 are

[0049] Figure 4This is a performance characterization diagram of the piezoresistive sensor prepared in Example 1

[0050] Figure 5 Schematic diagram of the mechanism for improving the linearity of the piezoresistive sensor prepared in Example 1

[0051] Figure 6 Transmission electron microscope images of the cross section and surface of the piezoelectric film prepared in Example 1

[0052] Figure 7 This is a characterization diagram of the piezoelectric properties and phase of the piezoelectric film prepared in Example 1

[0053] Figure 8 This is a graph showing the output performance of the piezoelectric sensor prepared in Example 1.

[0054] Figure 9 This is a diagram showing the mechanism of independent output of the piezoresistive sensor and the piezoelectric sensor in Example 1.

[0055] Figure 10 This is a test diagram and output performance diagram of the multimodal sensor simultaneously detecting the film deformation path.

[0056] Figure 11 This is a schematic diagram of the structure of the piezoelectric sensor in the present invention.

[0057] Figure 12 This is a photo of the piezoelectric sensor in Example 1. DETAILED DESCRIPTION

[0058] Overall, the present invention relates to the design and preparation of a multimodal flexible sensing array based on a dual sensing mechanism of piezoelectric and piezoresistive sensing. The sensing array achieves all-round and multi-angle sensing capabilities for strain behavior by integrating piezoelectric and piezoresistive sensors into the same device. Through the ultrasonic spraying process, the present invention successfully constructed a large-area, uniformly distributed sensor array with a size of 8cm×8cm, which has good scalability and batch production capabilities. The sensing system can simultaneously obtain the strain amplitude (measured by the piezoresistive sensor) and the strain rate (measured by the piezoelectric sensor), and can comprehensively analyze and monitor the structural response within the dynamic load frequency range of 20-700Hz. In order to improve the performance of the piezoresistive sensing layer, the carbon material was modified with polyvinyl pyrrolidone (PVP), which significantly improved its dispersibility in ethanol and effectively extended the crack propagation path to form a spider-web-like crack structure, avoiding through-fracture, thereby achieving an ultra-wide single-segment linear response range of 0.001%-45%. Furthermore, the piezoelectric sensor exhibited good linear voltage output characteristics over a strain rate range of 2.01 mm / s to 70.37 mm / s, validating its feasibility as a velocity sensor. The proposed multimodal flexible sensor array boasts high sensitivity, a wide linear range, and the ability to simultaneously detect multiple parameters. It enables high-resolution, real-time deformation recognition, providing key technical support for high-precision sensing applications such as surface inversion.

[0059] The present invention aims to prepare a large-area sensing array that integrates piezoelectric and piezoresistive mechanisms, capable of simultaneously sensing the amplitude and rate of change of strain. The sensor uses ultrasonic spraying, a process suitable for large-area manufacturing, to deposit the piezoresistive layer directly on the surface of the piezoelectric material, which is used as a single-sided electrode, achieving a highly integrated structural design. This compact integration method effectively overcomes the problems of bulky devices and unstable interface connections in traditional hybrid systems, while ensuring that both piezoelectric and piezoresistive sensors maintain excellent performance in key performance indicators such as sensitivity, linearity, and stability. On this basis, the technology demonstrates good practicality and broad application prospects.

[0060] The purpose of the present invention can be achieved through the following technical solution: an anisotropic high-sensitivity flexible piezoelectric sensor, comprising a packaging layer, a piezoelectric layer, a piezoresistive layer and an electrode layer, wherein the piezoresistive layer is directly used as one side electrode of the piezoelectric sensor.

[0061] See also Figure 1 , the specific preparation comprises the following steps:

[0062] 1) Preparation of Lead Zirconate Titanate-Glass Fiber Composite Piezoelectric Thin Film (PZT-GFF): The composite film was prepared using a template-assisted sol-gel method. A PZT sol-gel precursor solution was uniformly deposited onto the surface of GFF (glass fiber) fabric using an ultrasonic spray coating system (YMUS-ZM200). After spraying, the sample was annealed to form a perovskite phase structure.

[0063] 2) Polarization of piezoelectric film: The PZT-GFF composite film was directly subjected to corona poling treatment for 40 minutes to orient the internal dipoles.

[0064] 3) Preparation of dual-modal P-GC sensor array: The P-GC sensor array is integrated by a bottom-up stacking method. First, the polyurethane (PU) A and B components are vacuum degassed and mixed, and then spin-coated on a 12cm×12cm PTFE substrate at a speed of 700rpm. After curing at room temperature to form the bottom substrate, a stretchable silver electrode array is printed on it using screen printing technology as the bottom electrode of the piezoelectric layer. Subsequently, a layer of PU is spin-coated on the silver electrode surface at 700rpm again (for 30 seconds), and the PZT-GFF is quickly placed on it so that the PU covers the PZT-GFF, and then cured at room temperature. Next, an alcohol suspension of carbon material is sprayed onto the piezoelectric layer using a template mask. Finally, a stretchable silver wire is prepared by screen printing, and PU is spin-coated as a top encapsulation protective layer to isolate it from environmental interference.

[0065] In a specific implementation, the glass fiber filaments described in step 1) are high-strength electronic-grade glass fibers. Glass fiber fabric (GFF, Honghe Electronic Materials Co., Ltd.) can withstand high-temperature sintering temperatures up to 900°C, allowing it to withstand the high temperatures required during the crystallization of lead zirconate titanate.

[0066] In specific implementation, the preparation method of the piezoelectric composite film described in step 1) is combined with the large-area preparation method assisted by an ultrasonic sprayer. The specific steps include:

[0067] 1-1. Set the operating frequency of the ultrasonic atomizing nozzle to 80kHz and use compressed air with a pressure of 0.5-1MPa as the guide airflow.

[0068] 1-2. Fix a glass fiber fabric of 30 cm × 30 cm on a substrate using a vacuum pump. Place 50 ml of PZT precursor solution into an ultrasonic sprayer.

[0069] 1-3. Set the nozzle to move at a speed of 20 mm / s, control the liquid flow rate to 5-15 μL / s, set the spray width to 8 mm, and repeat the spraying process 5-15 times.

[0070] The preparation method of the PZT sol-gel precursor solution used in this embodiment is as follows:

[0071] 1. Raw material pretreatment: Lead acetate (Pb(CH3COO)2·3H2O) was vacuum dried at 110°C for 6 hours to remove crystal water;

[0072] 2. Zirconium / Titanium Alkoxide Dissolution: According to Pb(Zr 0.52 Ti 0.48 )O3 stoichiometric ratio, zirconium n-propoxide (Zr(OCH2CH2CH3)4) and tetrabutyl titanate (Ti(OCH(CH3)2)4) were dissolved in ethylene glycol methyl ether to a concentration of 0.5M and stirred at 40°C for 1 hour;

[0073] 3. Lead source introduction: Dissolve dehydrated lead acetate (10% excess) in a mixed solvent of ethylene glycol methyl ether / acetylacetone (acetylacetone and lead in the same molar ratio) to a concentration of 0.5 M. Add the zirconium-titanium mixture dropwise and stir at 65°C for 3 hours.

[0074] 4. Hydrolysis and aging: React at room temperature for 12 hours to obtain a light yellow transparent sol.

[0075] In a specific implementation, in the annealing method described in step 1), the sprayed piezoelectric film is heated at 150° C. for 10 minutes, and then annealed at 550-700° C. in a muffle furnace to form a perovskite phase structure.

[0076] In specific implementation, the large-area preparation method of the piezoresistive layer described in step 3) includes the following steps:

[0077] 3-1. Disperse graphene (5-20 mg / ml), carbon black (5-15 mg / ml) and PVP (5-15 mg / ml) in alcohol. Ultrasonicate the mixture for 1 hour and stir for 1-2 days before use to ensure that hydrogen bonds are fully formed between PVP and the dangling bonds on the graphene surface.

[0078] 3-2. Load the prepared suspension into an ultrasonic sprayer, fix the mask on the piezoelectric layer, and then fix it on the substrate via a vacuum pump.

[0079] 3-3. Set the spraying parameters as nozzle movement speed 20 mm / s, liquid flow rate 5-15 μL / s, spray width 5 mm, and spray the suspension onto the piezoelectric layer for a total of 15-30 times.

[0080] Specifically, a multimodal hybrid piezoelectric sensor array is prepared by the method described above.

[0081] In a specific implementation, the multi-modal hybrid piezoelectric sensing unit as described above is applied, and the sensor can be used to determine the deformation path.

[0082] In specific implementation, the specific application method of the handwriting intelligent recognition is: the hybrid sensor is bent in different sizes, speeds and directions, and the voltage output of the piezoelectric sensor and the resistance change of the piezoresistive sensor can be used to determine the deformation path applied to the sensor.

[0083] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Any features such as preparation methods, materials, structures or composition ratios not explicitly described in this technical solution are considered to be common technical features disclosed in the prior art.

[0084] Before further describing the specific embodiments of the present invention, it should be understood that the scope of the present invention is not limited to the specific embodiments described below. It should also be understood that the terminology used in the examples is intended to describe specific embodiments and is not intended to limit the scope of the present invention. The experimental procedures in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers.

[0085] When the embodiments provide numerical ranges, it should be understood that, unless otherwise specified in the present invention, both endpoints of each numerical range and any numerical value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those generally understood by those skilled in the art. In addition to the specific methods, equipment, and materials used in the embodiments, according to the understanding of the prior art by those skilled in the art and the description of the present invention, any methods, equipment, and materials of the prior art similar or equivalent to the methods, equipment, and materials described in the embodiments of the present invention may also be used to implement the present invention.

[0086] Example 1

[0087] A method for preparing a multimodal large-area sensor array in this embodiment includes the following steps:

[0088] Step 1: Preparation of Lead Zirconate Titanate-Glass Fiber Composite Piezoelectric Thin Film (PZT-GFF): The composite film was prepared using a template-assisted sol-gel method. A PZT sol-gel precursor solution was uniformly deposited onto the GFF fabric surface using an ultrasonic spraying device (YMUS-ZM200). The ultrasonic atomizing nozzle operated at an 80 kHz frequency, using compressed air at a pressure of 0.5 MPa as the guide airflow. A 30 cm × 30 cm glass fiber fabric was fixed to a substrate using a vacuum pump. The nozzle was moved at a speed of 20 mm / s, with a liquid flow rate of 7 μL / s. The spray width was set to 8 mm, and the spraying process was repeated 15 times. After spraying, the sample was annealed at 150°C for 10 minutes and then at 700°C for 1 hour to form the perovskite phase.

[0089] Step 2: Polarization of the piezoelectric film: The PZT-GFF composite film was directly subjected to a 40-min corona poling treatment to orient the internal dipoles.

[0090] Step 3: Preparation of dual-modal P-GC sensor array: The P-GC sensor array is integrated by a bottom-up stacking method. First, the polyurethane (PU) A and B components are vacuum degassed and mixed, and then spin-coated on a 12cm×12cm PTFE substrate at a speed of 700rpm. After curing at room temperature to form the bottom substrate, a stretchable silver electrode array is printed on it using screen printing technology as the bottom electrode of the piezoelectric layer. Subsequently, a layer of PU is spin-coated on the surface of the silver electrode at 700rpm again (for 30 seconds), and the PZT-GFF is quickly placed on it so that the PU covers the PZT-GFF, and then cured at room temperature. Next, an alcohol suspension of carbon material is sprayed onto the piezoelectric layer using a template mask. Finally, a stretchable silver wire is prepared by screen printing, and PU is spin-coated as a top encapsulation protective layer to isolate it from environmental interference.

[0091] Figure 11 It is a structural diagram of a piezoelectric sensor. Figure 12 This is a real photo of the piezoelectric sensor in Example 1.

[0092] Figure 2 a Comparison of the dispersion effects of graphene and carbon black in ethanol solutions without PVP and ethanol solutions containing PVP. It can be observed that in the alcohol solution containing PVP, the carbon material remains well dispersed within 24 hours without sedimentation. This stability is attributed to the strong affinity between PVP and the carbon material. During the stirring process, PVP can be adsorbed on the surface of the carbon material, providing steric hindrance and stabilization, thereby achieving good stable dispersion in the alcohol solution. This also ensures the uniformity and stability of the film composition after spraying. The electron transfer mechanism between PVP and PU was further analyzed using Fourier transform infrared spectroscopy (FTIR). PVP contains amide groups (-CONH-), while PU contains carbamate groups (-NHCOO-). As Figure 2 As shown in b, compared with pure PVP, the amide A peak of PVP-PU composite film is from 3412 cm -1 Red shift to 3404 cm -1 , indicating that a large number of hydrogen bonds were formed between PVP and PU after spraying.

[0093] Figure 3 a shows a cross-sectional scanning electron microscope image of the piezoresistive layer. It can be seen that in the film prepared by ultrasonic spraying, graphene has a layered stacking structure, and carbon black is distributed in a spherical shape between the layers of graphene, which effectively improves the conductivity of the film. Figure 3b shows the surface morphology of the piezoresistive layer. The surface of the piezoresistive film is uniform, which proves the reliability of large-area preparation using ultrasonic spraying technology.

[0094] This embodiment pioneers a novel integration strategy by synergistically integrating piezoelectric and piezoresistive sensors. The piezoresistive layer is deposited directly on the surface of the piezoelectric material and serves as its top electrode. This design effectively avoids the signal interference and performance loss issues associated with bulky devices and unstable interface connections in traditional hybrid systems, significantly improving the stability and reliability of the integrated system.

[0095] This embodiment innovatively utilizes ultrasonic spray coating technology to fabricate large-area sensor arrays. This technology is a low-cost, simple, and large-area coating process. It deposits a lead zirconate titanate sol-gel precursor solution evenly onto a glass fiber fabric surface. This is then dried and annealed to form a perovskite-phase lead zirconate titanate-glass fiber composite film. Ultrasonic spray coating ensures film uniformity and consistency, providing a new path for efficient integrated sensing units.

[0096] The piezoresistive sensor in this embodiment uses a polyvinyl pyrrolidone (PVP)-modified carbon material dispersion, with the piezoresistive sensing layer formed by ultrasonic spray coating. The PVP modification significantly improves the carbon material's dispersibility in ethanol and promotes the formation of a spiderweb-like crack structure during stretching, preventing through-breaks. This results in the piezoresistive sensor exhibiting an excellent single-segment linear resistance response over an ultra-wide strain range of 0.001% to 45%.

[0097] The piezoelectric sensor, constructed from a lead zirconate titanate-glass fiber composite film and subjected to corona poling, converts mechanical stress into a voltage signal. The output voltage of the piezoelectric sensor exhibits excellent linearity over a strain rate range of 2.01 mm / s to 70.37 mm / s. This linearity enables the sensor to accurately convert strain rate into a voltage signal, providing reliable dynamic response data for structural health monitoring.

[0098] Verification Example 1

[0099] Clamp the piezoresistive sensor to a mechanical testing machine and stretch it at a speed of 5 mm / min while recording the resistance change of the piezoresistive sensor. Observe how the resistance changes with strain.

[0100] Verification Example 2

[0101] Fix the two ends of the piezoresistive sensor, apply a fixed strain in the middle with an exciter, and observe how the resistance changes with the loading frequency.

[0102] Figure 4a Comparison of the sensing curves of pure graphene-carbon black and PU composite sensing membrane (PU / GH-CB) and PVP-modified graphene-carbon black and PU composite sensing membrane (PU / PVP-GH-CB) ( Figure 4 a) The results show that the linear sensing range of PU / GH-CB is limited to less than 20%. However, after adding PVP, its stable resistance growth range is significantly widened to 45%, while maintaining an excellent linearity of 0.99. Figure 4 b shows that the resistance change of the sensor remains stable under excitation of 20 Hz and 700 Hz, proving that the piezoresistive sensor in the present invention has a frequency stability up to 700 Hz.

[0103] Figure 5 a explained the phenomenon of linear range widening through the crack propagation path, and used scanning electron microscopy (SEM) to demonstrate the internal crack propagation behavior of the film under strain. Under tensile strain, a typical brittle film will have through-cracks perpendicular to the strain direction, resulting in a nonlinear increase in resistance. In the sensor prepared by the present invention, the interaction between PVP, carbon material and PU substrate inhibits the expansion of cracks during the stretching process, forcing the cracks to change their extension direction. Ultimately, a spider web-like crack structure is formed, replacing the traditional through-cracks, thereby making the resistance change under strain more gentle. Figure 5 b shows the crack morphology in the resistive sensing film under 20% strain, clearly showing a spider-web-like crack propagation pattern.

[0104] Figure 6 a shows the surface of the PZT-GFF composite film, and it is observed that PZT grows continuously along the GFF surface. Figure 6 b shows that the growth thickness of PZT on the surface of each GFF fiber bundle is about 610nm.

[0105] Figure 7 Figure a shows the piezoelectric properties of the composite film, monitored using an atomic force microscope (AFM) in piezoelectric force microscopy (PFM) mode. When a voltage of 26 V is applied, the PZT-GFF composite film exhibits a 180° phase angle shift, indicating domain reversal capability. The butterfly-shaped hysteresis loop further demonstrates the excellent ferroelectric properties of the grown PZT. Figure 7 a shows the X-ray diffraction (XRD) pattern of the composite film, which shows that PZT forms a pure perovskite phase after sintering without any impurity phase.

[0106] Verification Example 3

[0107] The piezoelectric-piezoresistive multimodal sensing unit is fixed on all sides, and deformations of different frequencies are applied to the middle of the sensor using an exciter. The output performance of the sensor is observed under different frequencies with the same deformation size, and the changes in the output corresponding to different strain rates are also observed. The output voltage of the piezoelectric sensor is recorded using a low-voltage probe of an oscilloscope.

[0108] Figure 8 a shows that the output voltage of the piezoelectric sensor increases with the increase of frequency. Figure 8 b shows that the piezoelectric output is linearly related to the strain rate in the strain rate range of 2.01 mm / s-70.37 mm / s.

[0109] Verification Example 4

[0110] A PZT-GFF piezoelectric sensor with Ag electrodes on the top and bottom is connected to resistors of different sizes. Loads of the same size and frequency are applied to the sensor, and the output changes across the sensor and the series resistor are observed.

[0111] Figure 9 Figure a-9c shows the changing trends of the piezoelectric sensor's output voltage and charge when the external resistance changes from 0 ohms to 100 megohms. It is noteworthy that when the external resistance is less than 10 megohms, the piezoelectric output remains stable. By using the conductive resistor layer as the working electrode of the piezoelectric sensor, the two sensing mechanisms can be integrated into the same device without interference, achieving a high degree of integration. This possibility of synchronous operation is due to the extremely high impedance of the piezoelectric sensor itself (over 100 MΩ), which allows its electrode resistance to fluctuate within a certain range without affecting performance.

[0112] Verification Example 5

[0113] Stick the piezoelectric and piezoresistive hybrid sensor on the film. First, use the conical tip to push the center of the film forward 1.5 mm and then start recording the signal changes of the piezoelectric and piezoresistive sensors. Then pull the tip outward 1.3 mm at a speed of 20 mm / s, push the tip inward 1 mm at a speed of 20 mm / s, and finally push the tip inward 0.3 mm at a speed of 30 mm / s.

[0114] Figure 10 The displayed piezoelectric signal produced three spikes corresponding to the three processes in Verification Example 5, at -23.4 mm / s, 22 mm / s, and 32.6 mm / s. The piezoresistive sensor also produced three step-like resistance changes corresponding to the three processes in Verification Example 5, corresponding to strains from 15.45% to 0.59%, then to 11.81%, and finally to 15.45%. This is consistent with the actual conditions in Verification Example 5.

[0115] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A sensor array based on a piezoelectric-piezoresistive synergistic mechanism, characterized in that: Including bottom-up integration: a flexible encapsulation base layer composed of cured polyurethane; The bottom electrode layer, consisting of a screen-printed stretchable silver electrode array, serves as the lower electrode of the piezoelectric sensor; A piezoelectric functional layer is composed of a lead zirconate titanate-glass fiber composite film, and the piezoelectric functional layer is subjected to corona polarization treatment; The piezoresistive sensing layer is formed by ultrasonic spraying a dispersion of a carbon material modified with polyvinyl pyrrolidone. The piezoresistive sensing layer serves as the upper electrode of the piezoelectric sensor. The piezoresistive sensing layer is directly deposited on the surface of the piezoelectric functional layer. The piezoresistive sensing layer and the piezoelectric functional layer are coupled by a circuit for synchronous acquisition of piezoelectric-piezoresistive signals via a common electrode. The top encapsulation protection layer is made of spin-coated polyurethane and cured.

2. A method for preparing a sensor array based on a piezoelectric-piezoresistive synergistic mechanism as claimed in claim 1, characterized in that: The following steps are involved: S1: Using ultrasonic spraying technology to deposit lead zirconate titanate sol-gel precursor solution on the surface of glass fiber fabric, and then annealing to form a perovskite phase lead zirconate titanate-glass fiber composite film; S2: The perovskite phase lead zirconate titanate-glass fiber composite film is subjected to corona poling treatment to orient the internal dipoles and obtain a piezoelectric functional layer; S3: Mix the polyurethane components A and B after vacuum degassing, and spin-coat them on a substrate to form a flexible encapsulation base layer, and screen-print a bottom electrode layer on the flexible encapsulation base layer; S4: Spin-coating a layer of polyurethane on the bottom electrode layer, placing the lead zirconate titanate-glass fiber composite film after corona poling treatment on it, and coating and curing to form a piezoelectric functional layer; S5: spraying a dispersion of a carbon material modified with polyvinyl pyrrolidone onto the surface of the piezoelectric functional layer by ultrasonic spraying to form a piezoresistive sensing layer; S6: Stretchable silver wires were prepared by screen printing on the piezoresistive sensing layer, and polyurethane was spin-coated on the substrate and cured to form a top encapsulation protective layer.

3. The method for preparing a sensor array based on a piezoelectric-piezoresistive synergistic mechanism according to claim 2, characterized in that: In S1, the specific parameters of the ultrasonic spraying process include: The operating frequency of the ultrasonic atomizing nozzle was set to 80kHz, and compressed air with a pressure of 0.5-1MPa was used as the guide airflow; The glass fiber fabric is fixed on the substrate by a vacuum pump, and the PZT precursor solution is loaded into the ultrasonic sprayer; Set the nozzle movement speed to 20 mm / s, control the liquid flow rate between 5-15 μL / s, set the spray width to 8 mm, and repeat the spraying process 5-15 times; The annealing method is: heating the sprayed film at 150° C. for 10 minutes, and then annealing at 550-700° C. to form a perovskite phase structure.

4. The method for preparing a sensor array based on a piezoelectric-piezoresistive synergistic mechanism according to claim 2, characterized in that: In S2, the specific conditions of the corona polarization treatment include: The perovskite phase lead zirconate titanate-glass fiber composite film is placed in a corona poling device and polarized by corona discharge to align the dipoles inside the piezoelectric material. The voltage of the corona polarization treatment is 2-5 kV, the polarization temperature is controlled between 25-40° C., and the relative humidity is maintained in the range of 30%-60%.

5. The method for preparing a sensor array based on a piezoelectric-piezoresistive synergistic mechanism according to claim 2, characterized in that: In S3, the mixing mass ratio of the polyurethane A and B components is 1:1, and the vacuum degassing time is not less than 30 minutes; The parameters for spin coating polyurethane were: rotation speed 700 rpm, spin coating time 30 s; When preparing the bottom electrode layer by screen printing, the solid content of the stretchable silver paste used is 60wt%-70wt%, the viscosity of the silver paste is 10000-15000mPa·s, the line width of the printed silver electrode array is 200-500μm, the spacing is 300-800μm, and it is dried at a temperature of 120-150℃ for 10-20 minutes.

6. The method for preparing a sensor array based on a piezoelectric-piezoresistive synergistic mechanism according to claim 2, characterized in that: In S4, the parameters for spin coating polyurethane are a rotation speed of 700 rpm and a spin coating time of 30 seconds; The lead zirconate titanate-glass fiber composite film that has been treated with corona polarization is quickly placed on it. The composite film is required to fit tightly with the polyurethane film without bubbles and wrinkles. It is then cured at room temperature for 1 hour, and then heated to 60°C for 2-3 hours to allow the polyurethane to completely cover and cure to form a stable piezoelectric functional layer.

7. The method for preparing a sensor array based on a piezoelectric-piezoresistive synergistic mechanism according to claim 2, characterized in that: In S5, the specific ratio of the polyvinyl pyrrolidone-modified carbon material dispersion is: 5-20 mg / ml of graphene, 5-15 mg / ml of carbon black, and 5-15 mg / ml of polyvinyl pyrrolidone dispersed in alcohol; The carbon material dispersion was ultrasonically treated for 1 hour and stirred for 1-2 days before use; The specific parameters of the ultrasonic spraying are a nozzle movement speed of 20 mm / s, a liquid flow rate of 5-15 μL / s, a spray width of 5 mm, and the spraying process is repeated 15-30 times to form a uniform and dense piezoresistive sensing layer. After spraying, the layer is dried at room temperature for 10-20 minutes.

8. The method for preparing a sensor array based on a piezoelectric-piezoresistive synergistic mechanism according to claim 2, characterized in that: In S6, when screen printing the stretchable silver wire, the silver paste used has a solid content of 60 wt% to 70 wt% and a viscosity of 10,000 to 15,000 mPa·s. The printed silver wire has a line width of 300 to 600 μm and a spacing of 400 to 900 μm. After printing, the silver wire is dried at 120 to 150° C. for 10 to 20 minutes. When the spin-coated polyurethane is cured to form the top encapsulation protective layer, the mixing mass ratio of the polyurethane A and B components is 1:1, the vacuum degassing time is not less than 30 minutes, the spin coating speed is 700 rpm, the spin coating time is 30 seconds, and then it is cured at room temperature for 2 hours, and then heated to 60°C for curing for 2-3 hours.

9. An application of the sensor array based on the piezoelectric-piezoresistive synergistic mechanism as claimed in claim 1, characterized in that: The sensor array based on the piezoelectric-piezoresistive synergistic mechanism is attached to the surface of the deformable object. By synchronously collecting the resistance change of the piezoresistive sensing layer and the output voltage of the piezoelectric functional layer, static strain monitoring, dynamic strain identification, and deformation path tracking are achieved.

10. The application of the sensor array based on the piezoelectric-piezoresistive synergistic mechanism according to claim 9, characterized in that: The deformable body includes one of a wind turbine blade, a spacecraft skin, and a robotic arm curved surface structure.

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