Helical cantilever friction-electricity-piezoelectric composite self-powered sensor and preparation method thereof

Abstract

The application discloses a spiral cantilever type triboelectric-piezoelectric composite self-powered sensor and a preparation method thereof. An Archimedes spiral cantilever, an Archimedes spiral cantilever support and an encapsulation box are processed first. Electrodes are arranged on the Archimedes spiral cantilever and the inner wall of the encapsulation box respectively. A polyhexamethylene adipate positive friction layer and a doped zinc oxide polyvinylidene fluoride-hexafluoropropylene / polyvinyl chloride composite negative friction layer are prepared by electrospinning. The Archimedes spiral cantilever is fixed at one end of the encapsulation box, and the positive and negative friction layers are statically kept at a gap. The scheme relies on the spiral topological structure to regulate and control the response frequency domain, covering the low-frequency vibration monitoring interval of the wing. The electrospun fiber constructs a high charge transfer interface, and zinc oxide synchronously generates piezoelectric charges, realizing the superposition and synergistic effect of triboelectric and piezoelectric signals. The composite negative friction layer is hydrophobic and moisture-resistant, and can inhibit the charge attenuation in a high-humidity environment. The application is assembled at room temperature, is simple and convenient to integrate, is suitable for distributed long-term monitoring of the wing, and has stable and reliable sensing performance.

Description

Technical Field

[0001] This invention relates to the fields of triboelectric nanogenerator technology and self-powered sensing technology, specifically to a helical cantilever triboelectric-piezoelectric composite self-powered sensor and its preparation method. Background Technology

[0002] With the rapid development of civil aviation and the low-altitude economy, the frequency of aircraft operation and loads are continuously increasing, placing higher demands on the accuracy, continuity, and reliability of overall aircraft structural safety monitoring. As the core aerodynamic load-bearing component that generates lift, the wing is continuously exposed to complex flow fields such as turbulence, separated flow, and vortex disturbances during flight, making it highly susceptible to various low-frequency vibration phenomena such as flutter, stall flutter, and vortex-induced vibration. Related research indicates that over 90% of harmful vibrations in aircraft wings are concentrated in the 1-50Hz low-frequency range. Long-term accumulation of these low-frequency vibrations can easily lead to wing structural fatigue, deformation, and even stall failures. Currently, vibration-induced stall accidents account for 36% of all aviation accidents and are showing an increasing trend year by year. Therefore, achieving long-term, accurate, and distributed monitoring of low-frequency wing vibrations is a core means of ensuring aircraft flight safety.

[0003] Currently, the mainstream wing vibration monitoring devices in the industry include piezoelectric accelerometers, MEMS inertial measurement units, and fiber Bragg grating sensors. Among them, piezoelectric accelerometers and fiber Bragg grating sensors generally suffer from problems such as dependence on external power supply, complex wiring structure, and large overall device weight, making it difficult to adapt to the application requirements of lightweight wings and distributed multi-point monitoring. At the same time, fiber Bragg grating sensors also have the drawbacks of expensive demodulation equipment and high system integration complexity. Although MEMS inertial sensors have the advantage of miniaturization, their low-frequency response performance is poor, and the detection sensitivity decreases significantly in the low-frequency range below 10Hz, making them unable to meet the requirements of accurate acquisition of ultra-low frequency weak vibrations of wings. All kinds of traditional monitoring devices are difficult to simultaneously meet the core monitoring requirements of self-powered operation, wide-band low-frequency response, high detection sensitivity, and adaptability to complex airborne environments.

[0004] Triboelectric nanogenerators, as a novel mechanical energy to electrical energy conversion device, can directly capture environmental mechanical energy and complete self-powered output by relying on contact electrification and electrostatic induction coupling effects. They have outstanding advantages such as simple structure, wide material adaptability, and no need for external power supply, effectively making up for the power supply shortcomings of traditional aerospace vibration sensors. At present, many triboelectric vibration sensors have been developed and applied to the field of structural vibration monitoring. However, existing devices still have significant technical defects when adapting to low-frequency vibration monitoring scenarios of aircraft wings.

[0005] The generalized structural design does not have a specific wideband optimization for the core low-frequency vibration range of the wing (1~50Hz). The traditional straight cantilever beam structure has a single natural frequency, which cannot cover the wideband low-frequency vibration range of the wing. It is very easy to generate coupling resonance with the aircraft structure. The spring-assisted frequency extension structure has the problems of difficult to accurately control the low-frequency stiffness and insufficient detection sensitivity below 10Hz, which seriously restricts the low-frequency detection performance.

[0006] Meanwhile, most existing triboelectric sensors adopt a planar thin-film triboelectric structure, which has a limited contact area and has not undergone hydrophobic modification. In the wide humidity fluctuation environment of 20% to 90% RH on the air, water molecules are easily adsorbed on the surface of the triboelectric layer, causing the interface charge to decay rapidly, resulting in poor environmental stability and long-term service performance of the device.

[0007] In addition, most current triboelectric-piezoelectric composite sensors are simply physical superpositions of two types of functional units, failing to achieve integrated and synergistic optimization of the structure and sensing system. The synergistic effect of force-electric conversion is weak, and the triboelectric layer generally lacks precise micro-nano structure control technology, resulting in low interface charge transfer efficiency. This further leads to the sensor's overall sensitivity, response speed, and power generation sensing efficiency failing to meet the requirements of high-precision long-term monitoring in aviation. Summary of the Invention

[0008] Therefore, the technical problem to be solved by the present invention is to overcome the problems of sensors being difficult to adapt to low-frequency vibration of wings, poor environmental stability and low force-to-electric conversion efficiency in the prior art, and to provide a helical cantilever triboelectric-piezoelectric composite self-powered sensor and its preparation method.

[0009] To solve the above-mentioned technical problems, the present invention provides a spiral cantilever triboelectric-piezoelectric composite self-powered sensor and its preparation method, comprising: step S1, preparing an Archimedes spiral cantilever, an Archimedes spiral cantilever support, and an encapsulation box; step S2, connecting a first electrode layer to the outer surface of the Archimedes spiral cantilever, and simultaneously connecting a second electrode layer to the inner surface of the encapsulation box; step S3, attaching a positive friction layer to the outer surface of the first electrode layer, and simultaneously attaching a negative friction layer to the inner surface of the second electrode layer, wherein the positive friction layer is prepared by dissolving polyhexamethylene adipamide powder in formic acid to obtain a positive friction spinning solution, and electrostatically reacting the positive friction spinning solution... The positive friction layer is obtained by spinning. The negative friction layer is prepared by dissolving polyvinylidene fluoride-hexafluoropropylene and polyvinyl chloride in a mixed solvent of N,N-dimethylformamide and acetone, then adding zinc oxide nanoparticles, dissolving and dispersing them to obtain a negative friction spinning solution, and then electrospinning the negative friction spinning solution to obtain the negative friction layer. Step S4: The processed Archimedes spiral cantilever is vertically fixed to the inner side wall of the encapsulation box through an Archimedes spiral cantilever support, and the positive friction layer and the negative friction layer are gap-fitted in the static state. Step S5: The first electrode layer and the second electrode layer are led out through wires to obtain the target sensor.

[0010] In one embodiment of the present invention, in step S1, the pitch of the Archimedes spiral cantilever structure is 4~12mm, the number of spiral turns is 1.5~5 turns, the thickness is 0.8~1.6mm, and the cantilever width is 0.7~7mm; the height of the Archimedes spiral cantilever support is 0.5~3mm, and the diameter is 0.7~3mm, so that the response bandwidth of the spiral cantilever triboelectric-piezoelectric composite self-powered sensor covers the vibration range of 1~50Hz.

[0011] In one embodiment of the present invention, in step S3, the preparation method of the positive friction layer is as follows: dissolving polyhexamethylene adipamide powder in formic acid to prepare a positive friction spinning solution with a mass fraction of 13-17%, and then electrospinning the positive friction spinning solution under the conditions of voltage 10-22kV, receiving distance 10-15cm, and feed rate 0.4-1.5mL / h to obtain the positive friction layer with a thickness of 100±10μm.

[0012] In one embodiment of the present invention, in step S3, the negative friction layer is prepared by: mixing polyvinylidene fluoride-hexafluoropropylene and polyvinyl chloride at a mass ratio of 85:15 and dissolving them in a mixed solvent of N,N-dimethylformamide and acetone at a volume ratio of 7:3; stirring magnetically at 500 rpm for 6 hours at 50°C; then adding 0.25~5 wt% zinc oxide nanoparticles; stirring magnetically at 500 rpm for 1 hour at room temperature and ultrasonicating in an ice bath for 20 minutes to obtain a negative friction spinning solution; and then electrospinning the negative friction spinning solution to obtain the negative friction layer with a thickness of 80±10 μm.

[0013] In one embodiment of the present invention, both the first electrode layer and the second electrode layer are copper foils with a thickness of 18~22μm. The first electrode layer is bonded and fixed to the Archimedes spiral cantilever by conductive adhesive, and the second electrode layer is bonded and fixed to the inner wall of the encapsulation box by conductive adhesive. The edges of the first electrode layer and the second electrode layer are provided with lead-out ends, and the lead-out ends are connected to insulated wires to realize the external output of electrical signals.

[0014] In one embodiment of the present invention, the Archimedes spiral cantilever, the Archimedes spiral cantilever support and the packaging box are all integrally prepared by fused deposition modeling 3D printing process, and the molding substrate is polylactic acid; the printing layer thickness is set to 0.1~0.2mm and the fill density is 100%.

[0015] This invention also provides a spiral cantilever triboelectric-piezoelectric composite self-powered sensor, which is fabricated using the aforementioned method. It comprises: an encapsulation housing, an Archimedean spiral cantilever, an Archimedean spiral cantilever support column, a first electrode layer, a second electrode layer, a positive friction layer, and a negative friction layer. The inner surface of the encapsulation housing is connected to the second electrode layer, and the inner surface of the second electrode layer is connected to the negative friction layer. The Archimedean spiral cantilever is disposed inside the encapsulation housing and fixedly mounted on the top of the Archimedean spiral cantilever support column, leaving the center end of the Archimedean spiral cantilever suspended. The outer surface of the Archimedean spiral cantilever is connected to the first electrode layer, and the outer surface of the first electrode layer is connected to the positive friction layer. A static gap is maintained between the positive and negative friction layers, allowing the positive and negative friction layers to periodically contact and separate when the Archimedean spiral cantilever is subjected to low-frequency vibration excitation and flexural deformation, thereby collaboratively generating a triboelectric-piezoelectric composite induced electrical signal.

[0016] In one embodiment of the present invention, the encapsulation box is a circular box with an outer diameter of 25-60 mm, a wall thickness of 3 mm, and a vertical distance of 3 mm between the upper and lower inner surfaces of the encapsulation box; the maximum displacement of the Archimedes spiral cantilever under its own gravity does not exceed 0.002 mm.

[0017] The technical solution of the present invention has the following advantages over the prior art: The spiral cantilever triboelectric-piezoelectric composite self-powered sensor and its preparation method described in this invention use an Archimedes spiral cantilever combined with a packaging box as the device support substrate, and construct a complete technical solution covering the selection of electrode layers, electrospinning of polyhexamethylene adipamide positive friction layer and polyvinylidene fluoride-hexafluoropropylene / zinc oxide / polyvinyl chloride composite negative friction layer, and control of friction layer gap.

[0018] Firstly, relying on the unique topology of the Archimedes spiral cantilever, the inherent vibration frequency band of the device can be flexibly adjusted, effectively widening the low-frequency response range and adapting to the 1~50Hz low-frequency vibration monitoring needs of the wing. This overcomes the problems of the traditional straight cantilever structure having a single inherent frequency, being prone to coupling resonance with the measured structure, and the rapid attenuation of sensitivity below 10Hz in the spring-assisted sensing structure.

[0019] Secondly, the nanofiber friction layer prepared by electrospinning can form a rich micro-nano rough interface, which greatly improves the charge transfer efficiency during the contact separation process. At the same time, the zinc oxide nanoparticles doped inside the negative friction layer can generate piezoelectric charges simultaneously when the friction layer is deformed under pressure, realizing the superposition output of triboelectric signal and piezoelectric charge, effectively improving the overall mechanical energy to electrical energy conversion efficiency and sensing signal output intensity of the device.

[0020] Furthermore, the negative friction layer made of polyvinylidene fluoride-hexafluoropropylene, polyvinyl chloride, and zinc oxide nanoparticles has excellent hydrophobic properties. Under conditions of large fluctuations in relative humidity in airborne environments, it can reduce the attenuation of interfacial charge caused by water molecule adsorption and significantly extend the stable monitoring time of the sensor.

[0021] The entire fabrication process requires no external power supply or wiring, and no expensive demodulation equipment. The structural components and sensing functional layers are processed in stages and then integrated into a single unit. The process is highly controllable and easy to assemble. The final sensor is small in size and lightweight, enabling distributed multi-point long-term vibration monitoring of the wing. The sealed enclosure can isolate airborne dust and moisture, further improving the sensor's reliability in complex aviation environments. Moreover, the entire assembly process is carried out at room temperature, which will not damage the micro-nano fiber structure constructed by electrospinning, ensuring the sensor's continuous and stable sensing output performance. Attached Figure Description

[0022] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0023] Figure 1 This is a schematic diagram of the macroscopic structure of the spiral cantilever triboelectric-piezoelectric composite self-powered sensor in a preferred embodiment of the present invention; Figure 2 yes Figure 1 The diagram shows the structure of the Archimedes spiral cantilever in the spiral cantilever triboelectric-piezoelectric composite self-powered sensor. Figure 3 yes Figure 1 The diagram shows the structural distribution of the first electrode layer, the second electrode layer, the positive friction layer, and the negative friction layer in the spiral cantilever triboelectric-piezoelectric composite self-powered sensor. Figure 4 yes Figure 1 The diagram shows the structure of the spiral cantilever triboelectric-piezoelectric composite self-powered sensor in the static state (a), vibration excitation state (b), and vibration rebound state (c). Figure 5 yes Figure 1 The image shows a comparison of the SEM microstructure of the negative tribological layer in a spiral cantilever triboelectric-piezoelectric composite self-powered sensor with different zinc oxide doping amounts. Figure 6 These are comparison charts of multiple sets of negative friction layer water contact angle tests; Figure 7 This is a schematic diagram of the electrospinning process for preparing the negative friction layer in a preferred embodiment of the present invention, specifically a spiral cantilever triboelectric-piezoelectric composite self-powered sensor and its preparation method.

[0024] Explanation of reference numerals in the accompanying drawings: 100, encapsulation housing; 200, Archimedes spiral cantilever; 300, Archimedes spiral cantilever support; 400, first electrode layer; 500, second electrode layer; 600, positive friction layer; 700, negative friction layer. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0026] Example 1: This example provides a method for fabricating a helical cantilever triboelectric-piezoelectric composite self-powered sensor, which includes: Step S1: Prepare the Archimedes spiral cantilever, the Archimedes spiral cantilever support, and the packaging box respectively. The Archimedes spiral cantilever serves as the elastic vibration deformation carrier of the device. Under vibration conditions, it can undergo reciprocating up-and-down flexural deformation, which drives the surface positive friction layer to complete the periodic contact and separation with the negative friction layer.

[0027] Furthermore, in this embodiment, the pitch of the Archimedes spiral cantilever structure is 8mm, the number of spiral turns is 3, the thickness is 1.0mm, and the width is 5mm; the Archimedes spiral cantilever support column is 1.5mm high and 1.5mm in diameter, and is fitted and fixed to the inner side wall of the encapsulation box, supporting the outer fixed end of the Archimedes spiral cantilever, so that the response bandwidth of the spiral cantilever triboelectric-piezoelectric composite self-powered sensor covers the vibration range of 1~50Hz. In different embodiments, the pitch of the Archimedes spiral cantilever structure can be configured to 4~12mm, the number of spiral turns can be configured to 1.5~5, the thickness can be configured to 0.8~1.6mm, and the cantilever width can be configured to 0.7~7mm. Through this set of parameter matching design, the natural frequency of the Archimedes spiral cantilever itself is precisely controlled, so that the sensor can be adapted to the target vibration range.

[0028] The encapsulation enclosure provides a sealed space for the entire device, supporting the inner second electrode layer and negative friction layer. It also provides physical protection for the internal sensing structure, limiting the maximum bonding gap between the positive and negative friction layers and constraining the deformation range of the Archimedes spiral cantilever. Separate fabrication of the Archimedes spiral cantilever and the encapsulation enclosure allows for independent control of the dimensional accuracy and surface flatness of both structural components, facilitating subsequent electrode and friction layer bonding and assembly. The completed enclosure, once formed, can isolate the device from dust and moisture in the aerospace environment, improving its environmental tolerance.

[0029] In this embodiment, both the Archimedes spiral cantilever and the encapsulation box are integrally fabricated using fused deposition modeling (FDM) 3D printing, with polylactic acid as the substrate. The printing layer thickness is set to 0.15 mm, and the infill density is 100%. This process enables rapid mold-free customization of the Archimedes spiral structure, balancing high structural precision and lightweight requirements. Furthermore, the room-temperature molding process does not damage the subsequent bonding and fixation with electrodes and friction layers. Simultaneously, the sealed box structure provides environmental protection for the sensing unit, effectively ensuring the structural reliability and sensing stability of the sensor during long-term vibration monitoring.

[0030] Step S2: Connect a first electrode layer to the outer surface of the Archimedean spiral cantilever, and simultaneously connect a second electrode layer to the inner surface of the encapsulation housing. The first electrode layer is attached to the outer side of the Archimedean spiral cantilever to collect the triboelectric charge generated during the contact separation process of the positive friction layer; the second electrode layer is attached to the inner wall of the encapsulation housing to simultaneously collect the triboelectric charge and piezoelectric charge generated by the negative friction layer. The two sets of electrodes serve as charge discharge carriers, adapting to the sensor's contact-separation working mode and constructing a complete charge collection circuit.

[0031] Furthermore, in this embodiment, both the first and second electrode layers are configured as copper sheets, and both are copper foils with a thickness of 20 μm. The first electrode layer is bonded to the Archimedean spiral cantilever by curing conductive adhesive at room temperature for 24 hours, and the second electrode layer is bonded to the inner wall of the packaging box by curing conductive adhesive at room temperature for 24 hours. In this embodiment, a copper foil with a thickness of 18~22 μm is used. This copper foil has both good conductivity and flexibility, and it does not break or delaminate as the Archimedean spiral cantilever reciprocates. Moreover, the room temperature curing bonding process does not damage the micro-nano fiber structure of the electrospun friction layer. Combined with the edge lead-out end and insulated wire, it achieves low-noise and continuous electrical signal output even when contact is separated.

[0032] Step S3: A positive friction layer is attached to the outer surface of the first electrode layer, and a negative friction layer is attached to the inner surface of the second electrode layer. This ensures that the positive friction layer on the Archimedes spiral cantilever can fully contact the upper and lower negative friction layers successively during vibration deformation, thus extending the charge generation cycle. The friction functional layer is prepared by electrospinning in an integrated manner. The process is standardized, can be replicated in batches, and does not require additional micro-nano processing steps, simplifying the overall preparation process.

[0033] Furthermore, in this embodiment, the preparation method of the positive friction layer is as follows: Polyhexamethylene adipamide powder is dissolved in formic acid, and a positive friction spinning solution with a mass fraction of 15% is prepared by magnetic stirring at 350 rpm for 4 hours at 70°C. Then, the positive friction spinning solution is electrospun under conditions of 18 kV voltage, 12 cm receiving distance, and a feed rate of 0.8 mL / h to obtain the positive friction layer with a thickness of 100 ± 10 μm. As the positive electrode friction material of the triboelectric system, it stably loses electrons and generates positive charges during vibration and contact. The porous morphology of the nanofibers can significantly increase the effective contact area of ​​friction and improve the interfacial charge transfer efficiency. Simultaneously, the electrospinning process is conducted at low temperatures throughout, which does not damage the electrode conductivity, and the film thickness is controllable, meeting the miniaturization requirements of sensors.

[0034] In different embodiments, a positive triboelectric spinning solution with a mass fraction of 13-17% is prepared by dissolving polyhexamethylene adipamide powder in formic acid. Electrospinning is then carried out under process conditions of 10-22 kV voltage, 10-15 cm receiving distance, and 0.4-1.5 mL / h feed rate, ultimately forming a positive triboelectric layer with a thickness controlled within the range of 100±10 μm. The above parameter range can be flexibly adjusted according to actual process requirements to prepare a positive triboelectric functional layer that is free of beads and broken fibers, has uniform fiber thickness, and consistent electromechanical conversion performance. This ensures that the sensor continuously outputs a uniform and stable positive charge within the target frequency range, providing a reliable contact separation interface for the triboelectric-piezoelectric composite sensing system.

[0035] Accordingly, in this embodiment, the negative friction layer is prepared as follows: polyvinylidene fluoride-hexafluoropropylene and polyvinyl chloride are mixed and dissolved in a mixed solvent of N,N-dimethylformamide and acetone in a volume ratio of 7:3 at a mass ratio of 85:15. After magnetic stirring at 500 rpm for 6 hours at 50°C, 1.0 wt% of zinc oxide nanoparticles are added. After magnetic stirring at 500 rpm for 1 hour at room temperature and ultrasonication in an ice bath for 20 minutes, a negative friction spinning solution is obtained. The negative friction spinning solution is then electrospun to obtain the negative friction layer with a thickness of 80±10 μm. The negative friction layer prepared by this method has a uniform fiber morphology without beading, well dispersed zinc oxide particles, and a uniform and stable microstructure. Furthermore, the composite fiber is intrinsically hydrophobic, which can effectively suppress the decay of interfacial charge under high humidity conditions.

[0036] In different embodiments, polyvinylidene fluoride-hexafluoropropylene and polyvinyl chloride are mixed at a fixed mass ratio of 85:15 and dissolved in a mixed solvent of N,N-dimethylformamide and acetone with a volume ratio of 7:3. The mixture is magnetically stirred at 500 rpm for 6 hours at 50°C. Then, 0.25~5% zinc oxide nanoparticles are added. After magnetic stirring at room temperature for 1 hour, the mixture is ultrasonically stirred in an ice bath for 20 minutes to obtain a uniformly dispersed and non-agglomerated negative friction spinning solution. The solution is then electrospun to form a negative friction layer with a thickness controlled at 80±10 μm.

[0037] The above parameter ranges can be flexibly adjusted according to actual needs, and the zinc oxide doping amount can be matched to different piezoelectric output requirements; the fixed ratio of polymer substrate can not only ensure stable film formation by electrospinning, but also endow the film with excellent electron-acquiring properties and hydrophobic stability. Ultimately, a stable output of a composite electrical signal of triboelectric and piezoelectric superposition is achieved at the target vibration monitoring frequency, improving the sensor's low-frequency sensitivity and long-term environmental adaptability.

[0038] Step S4: The processed Archimedes spiral cantilever is vertically fixed to the inner side wall of the packaging box via the Archimedes spiral cantilever support, and a gap is left between the positive friction layer and the negative friction layer in the static state to avoid continuous wear of the friction layer and generation of baseline stray electrical signals due to static contact. Under vibration excitation, the free end of the Archimedes spiral cantilever can bend up and down reciprocally, realizing the periodic contact and separation of the positive friction layer and the negative friction layers on the upper and lower sides of the packaging box.

[0039] Step S5: After leading out the first electrode layer and the second electrode layer through wires, the target spiral cantilever triboelectric-piezoelectric composite self-powered sensor is obtained. The wires connect the two sets of electrodes respectively, and the alternating charge signal generated by the superposition of triboelectric and piezoelectric signals is exported to the outside, realizing the external transmission of vibration electrical signals for the back-end acquisition equipment to read vibration amplitude and frequency data.

[0040] Furthermore, the electrode wires are independently led out from the reserved holes in the packaging box, which can simultaneously complete the box sealing, taking into account both signal output and environmental protection. The molded device does not require an additional external power supply, and relies on the mechanical energy of environmental vibration to drive the sensing, eliminating the need for airborne wiring and external power supply supporting structures, and adapting to the distributed multi-point lightweight deployment requirements of aircraft wings.

[0041] Example 2: See Figures 1 to 7 As shown, this embodiment provides a spiral cantilever triboelectric-piezoelectric composite self-powered sensor, which is processed using the spiral cantilever triboelectric-piezoelectric composite self-powered sensor manufacturing method described in Embodiment 1. It includes: a package housing 100, an Archimedes spiral cantilever 200, an Archimedes spiral cantilever support 300, a first electrode layer 400, a second electrode layer 500, a positive friction layer 600, and a negative friction layer 700.

[0042] In this design, the upper and lower surfaces of the Archimedes spiral cantilever 200 are sequentially bonded and fixed with a first electrode layer 400 and a positive friction layer 600, and then vertically fixed to the inner wall of the encapsulation housing 100 via an Archimedes spiral cantilever support 300, allowing the center end of the Archimedes spiral cantilever 200 to be in a free-floating state. The upper and lower inner surfaces of the encapsulation housing 100 are sequentially bonded and fixed with a second electrode layer 500 and a negative friction layer 700, providing an attachment surface and sealing protection for the internal sensing components, while limiting the deformation range of the Archimedes spiral cantilever 200 and maintaining the static gap reference between the positive friction layer 600 and the negative friction layer 700. Under vibration excitation, the Archimedes spiral cantilever 200 undergoes flexural deformation, causing the positive friction layer 600 and the negative friction layer 700 to periodically contact and separate, collaboratively generating a triboelectric-piezoelectric composite induced electrical signal.

[0043] Furthermore, in this embodiment, the encapsulation box 100 is a circular box with an outer diameter of 40mm, a wall thickness of 3mm, and a vertical distance of 3mm between the upper and lower inner surfaces. In different embodiments, the outer diameter of the encapsulation box 100, combined with the cantilever size, can be adjusted within the range of 25~60mm. The circular box has no stress-prone sharp corners, resulting in uniform stress distribution. The 3mm wall thickness ensures structural strength to resist environmental impacts and moisture intrusion. The fixed 3mm inner distance precisely limits the deflection stroke of the Archimedes spiral cantilever 200, preventing excessive compression of the friction layer and causing microstructural damage, while ensuring the consistency of the sensor signal output within the target frequency response range. The Archimedes spiral cantilever 200 is fixed at one end to the inner wall of the packaging box 100 via the Archimedes spiral cantilever support 300, forming a cantilever structure. Relying on its own spiral topological mechanical properties, it exhibits a sensitive response to low-frequency vibrations of 1-50Hz. When excited by vibration, it undergoes reciprocating flexural deformation, causing the surface positive friction layer 600 and negative friction layer 700 to periodically contact and separate. It is the core elastic deformation carrier for achieving contact separation at the friction interface. In this embodiment, the maximum displacement of the Archimedes spiral cantilever 200 under its own gravity does not exceed 0.002mm. This ensures that when the sensor is in a static state without external vibration excitation, the surface positive friction layer 600 of the Archimedes spiral cantilever 200 always maintains a stable gap with the negative friction layer 700 inside the packaging box 100. This fundamentally prevents continuous frictional loss of the friction layer's micro / nano fiber structure and zinc oxide nanoparticles under vibration-free conditions, while also avoiding stray baseline electrical signals from static contact interfering with low-frequency vibration signal recognition.

[0044] Furthermore, in this embodiment, the Archimedes spiral cantilever support 300 has a height of 1.5 mm and a diameter of 1.5 mm. In different embodiments, to match the encapsulation box 100 with different outer diameters and the Archimedes spiral cantilever 200 with different geometric parameters, its height can be adjusted within the range of 0.5~3 mm, and its diameter can be adjusted within the range of 0.7~3 mm, thereby forming an auxiliary limiting support for the free end of the Archimedes spiral cantilever 200.

[0045] In this embodiment, the first electrode layer 400 is attached to the outside of the Archimedes spiral cantilever 200 to collect the positive friction charge generated during the contact separation process of the positive friction layer 600, and conducts the charge signal outward by relying on the edge lead-out end; the second electrode layer 500 is attached to the inner surface of the encapsulation box 100 to simultaneously capture the negative friction charge generated by the negative friction layer 700 and the piezoelectric charge generated by the pressure deformation, and cooperates with the first electrode layer 400 to form a complete charge acquisition circuit.

[0046] The positive friction layer 600 is attached to the first electrode layer 400. When vibrating and in contact, it loses electrons and generates positive frictional charge. The nanofiber microstructure greatly improves the charge transfer efficiency. The negative friction layer 700 is attached to the second electrode layer 500. When rubbing and in contact, it captures electrons and generates negative frictional charge. When under pressure, it synchronously outputs piezoelectric charge. The superposition of the two types of charge enhances the sensing output and completes the self-powered vibration information acquisition.

[0047] See Figure 5 As shown in the figure, the electron microscope of the negative friction layer 700 after the above treatment shows that there are no large number of beads in the fibers and no agglomeration of zinc oxide particles. The thickness error is controlled within ±10μm. This proves that the complete set of preparation process parameters of the negative friction layer 700 of the present invention has good adaptability and strong molding stability. It can produce composite nanofiber membranes with regular fibers, uniform zinc oxide dispersion, and uniform thickness. It takes into account stable triboelectricity, piezoelectric synergy and moisture resistance for long-term working performance, ensuring the consistency and long-term reliability of the sensor's low-frequency monitoring output.

[0048] See Figure 6 As can be seen, the 700-nano fiber membrane of negative friction layer formed by electrospinning of polyvinylidene fluoride-hexafluoropropylene and polyvinyl chloride composite substrate and doped with zinc oxide nanoparticles has excellent hydrophobic properties. It can significantly reduce the amount of water molecules adsorbed at the friction interface in a wide humidity environment on the air, suppress the surface charge decay caused by water vapor, and effectively improve the signal stability of the sensor under long-term monitoring conditions of 20%~90% relative humidity.

[0049] In summary, the spiral cantilever triboelectric-piezoelectric composite self-powered sensor and its fabrication method described in this invention, after being formed through the above-mentioned process, can stably respond to low-frequency vibration excitation of 1~50Hz and output a composite electrical signal superimposed by triboelectric and piezoelectric forces. The nanofiber triboelectric layer constructed by electrospinning has a uniform morphology and high interfacial charge transfer efficiency, and the zinc oxide nanoparticles doped in the negative triboelectric layer are well dispersed, resulting in significant synergistic effects of piezoelectricity. Simultaneously, the composite negative triboelectric layer possesses excellent hydrophobic properties, maintaining stable charge output under wide humidity fluctuations in airborne environments. The entire device requires no external power supply or complex wiring, is compact in size, and can be adapted to the distributed multi-point long-term monitoring needs of airfoils.

[0050] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for fabricating a helical cantilever triboelectric-piezoelectric composite self-powered sensor, characterized in that: include: Step S1: Prepare the Archimedes spiral cantilever, the Archimedes spiral cantilever support, and the encapsulation box respectively; Step S2: The first electrode layer is attached and fixed to the outer surface of the Archimedes spiral cantilever, and the second electrode layer is connected to the inner surface of the encapsulation box. Step S3: A positive friction layer is attached to the outer surface of the first electrode layer, and a negative friction layer is attached to the inner surface of the second electrode layer. The positive friction layer is prepared by dissolving polyhexamethylene adipamide powder in formic acid to obtain a positive friction spinning solution, and then obtaining the positive friction layer by electrospinning the positive friction spinning solution. The negative friction layer is prepared by dissolving polyvinylidene fluoride-hexafluoropropylene and polyvinyl chloride in a mixed solvent of N,N-dimethylformamide and acetone, then adding zinc oxide nanoparticles, dissolving and dispersing them to obtain a negative friction spinning solution, and then obtaining the negative friction layer by electrospinning the negative friction spinning solution. Step S4: The processed Archimedes spiral cantilever is vertically fixed to the inner side wall of the encapsulation box through the Archimedes spiral cantilever support, and a gap is maintained between the positive friction layer and the negative friction layer in the static state. Step S5: After leading out the first electrode layer and the second electrode layer through wires, the target sensor is obtained.

2. The method for fabricating a helical cantilever triboelectric-piezoelectric composite self-powered sensor according to claim 1, characterized in that: In step S1, the pitch of the Archimedes spiral cantilever structure is 4~12mm, the number of spiral turns is 1.5~5, the thickness is 0.8~1.6mm, and the width is 0.7~7mm, so that the response bandwidth of the spiral cantilever triboelectric-piezoelectric composite self-powered sensor covers the vibration range of 1~50Hz; the height of the Archimedes spiral cantilever support is 0.5~3mm, and the diameter is 0.7~3mm, and the diameter of the Archimedes spiral cantilever support matches the outer end mounting dimensions of the Archimedes spiral cantilever.

3. The method for fabricating a helical cantilever triboelectric-piezoelectric composite self-powered sensor according to claim 1, characterized in that: In step S3, the preparation method of the positive friction layer is as follows: dissolve polyhexamethylene adipamide powder in formic acid to prepare a positive friction spinning solution with a mass fraction of 13~17%, and then perform electrospinning on the positive friction spinning solution under the conditions of voltage 10~22kV, receiving distance 10~15cm, and feed rate 0.4~1.5mL / h to obtain the positive friction layer with a thickness of 100±10μm.

4. The method for fabricating a helical cantilever triboelectric-piezoelectric composite self-powered sensor according to claim 1, characterized in that: In step S3, the negative friction layer is prepared as follows: polyvinylidene fluoride-hexafluoropropylene and polyvinyl chloride are mixed and dissolved in a mixed solvent of N,N-dimethylformamide and acetone with a volume ratio of 7:3 at a mass ratio of 85:

15. After stirring magnetically at 500 rpm for 6 hours at 50°C, 0.25~5 wt% of zinc oxide nanoparticles are added. After stirring magnetically at 500 rpm for 1 hour at room temperature and ultrasonicating in an ice bath for 20 minutes, a negative friction spinning solution is obtained. The negative friction spinning solution is electrospinned to obtain the negative friction layer with a thickness of 80±10 μm.

5. The method for fabricating a helical cantilever triboelectric-piezoelectric composite self-powered sensor according to claim 1, characterized in that: Both the first electrode layer and the second electrode layer are copper foils with a thickness of 18~22μm. The first electrode layer is bonded and fixed to the Archimedes spiral cantilever with conductive adhesive, and the second electrode layer is bonded and fixed to the inner wall of the encapsulation box with conductive adhesive. The edges of the first electrode layer and the second electrode layer are provided with lead-out ends, which are connected to insulated wires to realize the external output of electrical signals.

6. The method for fabricating a helical cantilever triboelectric-piezoelectric composite self-powered sensor according to claim 1, characterized in that: The Archimedes spiral cantilever, the Archimedes spiral cantilever support, and the encapsulation box are all integrally prepared using fused deposition modeling 3D printing technology, with polylactic acid as the substrate. The printing layer thickness is set to 0.1~0.2mm, and the fill density is 100%.

7. A spiral cantilever triboelectric-piezoelectric composite self-powered sensor, characterized in that: The sensor is fabricated using the method described in any one of claims 1 to 6 for a helical cantilever triboelectric-piezoelectric composite self-powered sensor, comprising: The package includes an enclosure, an Archimedes cantilever, an Archimedes cantilever support, a first electrode layer, a second electrode layer, a positive friction layer, and a negative friction layer. The inner surface of the encapsulation box is connected to the second electrode layer, and the inner surface of the second electrode layer is connected to the negative friction layer. The Archimedes spiral cantilever is fixedly installed on the top of the Archimedes spiral cantilever support, so that the center end of the Archimedes spiral cantilever is suspended in the air. The outer surface of the Archimedes spiral cantilever is connected to the first electrode layer, and the outer surface of the first electrode layer is connected to the positive friction layer. The positive friction layer and the negative friction layer maintain a static gap, so that when the Archimedes spiral cantilever is subjected to low-frequency vibration excitation and flexural deformation, the positive friction layer and the negative friction layer can achieve periodic contact separation and jointly generate a triboelectric-piezoelectric composite induced electrical signal.

8. The spiral cantilever triboelectric-piezoelectric composite self-powered sensor according to claim 7, characterized in that: The encapsulation box is a circular box with an outer diameter of 25-60mm and a wall thickness of 3mm. The vertical distance between the upper and lower inner surfaces of the encapsulation box is 3mm. The maximum displacement of the Archimedes spiral cantilever under its own gravity does not exceed 0.002mm.

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