Electrochromic spiral coated piezoelectric composite yarn and preparation method thereof

Abstract

The invention introduces an electrochromic spiral coated piezoelectric composite yarn and a preparation method thereof, and belongs to the technical field of functional materials, the electrochromic spiral coated piezoelectric composite yarn comprises a silver-plated nylon core yarn, and a nanofiber layer, a packaging layer, a transparent conductive layer, an electrochromic active layer, an ionic gel electrolyte layer and an ion storage layer which are sequentially arranged outside the silver-plated nylon core yarn; wherein the nanofiber layer is PVDF / BaTiO3 nanofiber yarn spirally and crosswise wrapping the surface of the silver-plated nylon core yarn, the transparent conductive layer is formed by curing PEDOT: PSS conductive polymer dispersion liquid, the electrochromic active layer is tungsten trioxide nanowires uniformly deposited on the transparent conductive layer, and the ion storage layer is a Prussian blue nanolayer. The problems that an existing piezoelectric yarn is poor in environmental adaptability, insufficient in mechanical durability and unstable in piezoelectric output are solved.

Description

Technical Field

[0001] The invention relates to an electrochromic spiral-coated piezoelectric composite yarn and a preparation method thereof, and belongs to the technical field of functional materials. Background Art

[0002] With breakthroughs in flexible electronics, demand for piezoelectric materials in applications such as smart textiles, wearable health monitoring, and ambient energy harvesting is rapidly increasing. Traditional piezoelectric materials, primarily inorganic ceramics, offer high piezoelectric coefficients and stable output. However, their inherent brittleness, high stiffness, and incompatibility with flexible substrates severely limit their direct application in deformable electronic devices. In recent years, polymer piezoelectric materials have become a research hotspot due to their flexibility. Polyvinylidene fluoride (PVDF) and its copolymers, owing to their excellent piezoelectric response, chemical stability, and ease of processing, have been widely used in flexible piezoelectric sensors and energy harvesting devices. To enhance the comprehensive performance of PVDF-based piezoelectric materials, researchers have conducted multi-dimensional composite modification efforts. Firstly, by introducing conductive fillers or piezoelectric-enhancing phases, a "conductive-piezoelectric" synergistic network is constructed, simultaneously improving the material's conductivity and piezoelectric output. Secondly, structural design strategies are employed to optimize stress transfer and energy conversion efficiency. Furthermore, surface encapsulation techniques are being used to enhance the material's environmental stability and mechanical durability. These technological approaches have, to a certain extent, facilitated the transition of flexible piezoelectric materials from the laboratory to practical applications.

[0003] Although existing technologies have improved the performance of PVDF-based piezoelectric materials through composite modification and structural design, they still face three core bottlenecks that restrict their practical application in complex scenarios. Pure PVDF and most modified materials are highly sensitive to humidity. After absorbing moisture, they are prone to a decrease in crystallinity and polarization degradation, resulting in a decrease in piezoelectric performance. At the same time, their chemical corrosion resistance is limited. They are prone to swelling or degradation in complex liquid environments such as sweat and seawater, which limits their application in scenarios such as underwater sensors and wearable medical devices. The interfacial bonding between the conductive / piezoelectric filler and the polymer matrix in the composite material is weak. During long-term repeated deformation, the filler is prone to fall off or agglomeration, resulting in a break in the conductive network and unstable piezoelectric output. In addition, due to the structural anisotropy of fibrous piezoelectric materials, fibers are prone to breakage or interlayer delamination under dynamic loads, further reducing the life of the device. Existing piezoelectric materials mostly focus on the output of a single piezoelectric signal and lack the ability to simultaneously perceive multimodal signals, making it difficult to meet the integrated "perception-feedback-interaction" needs of smart fabrics. At the same time, during long-term cyclic use, the material's output performance continues to decay due to polarization fatigue and structural aging, limiting its application in high-frequency energy harvesting or long-term health monitoring.

[0004] Therefore, existing piezoelectric yarns have problems such as poor environmental adaptability, insufficient mechanical durability and unstable piezoelectric output. Summary of the Invention

[0005] The purpose of the present invention is to provide an electrochromic spiral-coated piezoelectric composite yarn and a preparation method thereof. By using a nanofiber layer to perform multi-layer coating and packaging process on the silver-plated nylon core yarn, the problems of poor environmental adaptability, insufficient mechanical durability and unstable piezoelectric output of existing piezoelectric yarns are solved, and the piezoelectric performance, mechanical flexibility and long-term stability of the fiber are significantly improved, providing a new solution for the application of flexible electronic devices.

[0006] In order to solve the above technical problems, the present invention is implemented by adopting the following technical solutions:

[0007] In a first aspect, the present invention provides an electrochromic spiral-wrapped piezoelectric composite yarn, comprising a silver-plated nylon core yarn and a nanofiber layer, an encapsulation layer, a transparent conductive layer, an electrochromic active layer, an ion gel electrolyte layer, and an ion storage layer sequentially arranged on the outside of the silver-plated nylon core yarn;

[0008] Among them, the nanofiber layer is PVDF / BaTiO3 nanofiber yarn spirally cross-wrapped on the surface of silver-plated nylon core yarn, the transparent conductive layer is formed by curing PEDOT:PSS conductive polymer dispersion, the electrochromic active layer is tungsten trioxide nanowires uniformly deposited on the transparent conductive layer, and the ion storage layer is a Prussian blue nanolayer.

[0009] Furthermore, the number of coating layers of the nanofiber layer is 2-8;

[0010] And / or, the thickness of the transparent conductive layer is 0.5-2 μm;

[0011] and / or, the thickness of the electrochromic active layer is 5-20 μm;

[0012] and / or, the thickness of the ion storage layer is 3-15 μm;

[0013] And / or, the thickness of the ion gel electrolyte layer is 10-30 μm.

[0014] Furthermore, the encapsulation layer is a PDMS (polydimethylsiloxane) encapsulation layer with a thickness of 20-30 μm.

[0015] In a first aspect, the present invention provides a method for preparing the electrochromic spiral-coated piezoelectric composite yarn as described in the first aspect, characterized by comprising:

[0016] The PVDF / BaTiO3 nanofiber yarn was spirally cross-wrapped along the axial direction of the silver-coated nylon core yarn to form a nanofiber layer;

[0017] The nanofiber layer is encapsulated with PDMS as a curing liquid to form an encapsulation layer, and then immersed in a PEDOT:PSS conductive polymer dispersion to form a transparent conductive layer;

[0018] An electrochromic layer is formed by spraying a tungsten trioxide nanowire ethanol suspension on the surface of the transparent conductive layer;

[0019] The ion gel electrolyte is spin-coated on the surface of the electrochromic layer and covered with a Prussian blue nanolayer after curing to form an ion storage layer.

[0020] Furthermore, the calculation expression of the twist between the silver-plated nylon core yarn and the nanofiber layer is expressed as:

[0021] ;

[0022] Where, represents the twist between the silver-plated nylon core yarn and the nanofiber layer, in r / m, Indicates the speed of the silver-plated nylon core yarn in m / min. It represents the wrapping speed of the nanofiber layer in m / min.

[0023] Furthermore, the thickness of the solidified layer was adjusted to 20-30 μm by simulating the interfacial stress distribution between the encapsulation layer and the nanofiber layer using COMSOL.

[0024] Furthermore, the preparation method of the PVDF / BaTiO3 nanofiber yarn comprises:

[0025] Dissolve the PVDF masterbatch in dimethylformamide solvent to prepare a 10-20 wt% PVDF solution, and stir magnetically in a 60°C water bath for 1-3 hours until completely dissolved;

[0026] Weigh 5-15 wt% of barium titanate nanopowder based on the mass of the PVDF masterbatch and add it to the above solution. After ultrasonic dispersion for 8-16 hours, a uniformly dispersed spinning solution is obtained.

[0027] The spinning solution was injected into the electrospinning nozzle and reciprocatingly cross-wrapped with 4-8 layers of silver-plated nylon core yarn and dried at 60°C for 1-3 h to remove the residual solvent to obtain PVDF / BaTiO3 nanofiber yarn.

[0028] Furthermore, the method of encapsulating the nanofiber layer using PDMS as a curing liquid to form an encapsulation layer includes:

[0029] Mix the base glue and PDMS in a mass ratio of 8:1-12:1, stir for 20-40 minutes, and then stand for pre-curing for 10-14 hours to obtain a PDMS solution;

[0030] The nanofiber layer was immersed in the PDMS solution and brushed for 3-7 minutes to ensure uniform coverage. After that, it was straightened and fixed and dried at 60°C for 20-40 minutes for secondary curing to form an encapsulation layer with a thickness of about 20-30 μm.

[0031] Furthermore, the method for preparing the electrochromic active layer comprises:

[0032] The tungsten trioxide nanowires were uniformly deposited on the surface of the transparent conductive layer by electrostatic spraying of an ethanol suspension of tungsten trioxide nanowires at a concentration of 20-40 min, and an electrochromic active layer with a thickness of 10±2 μm was formed after drying.

[0033] Furthermore, the method for preparing the ion storage layer includes:

[0034] Spin-coating an ion gel electrolyte on the surface of the electrochromic layer to form an ion gel electrolyte layer after curing;

[0035] The ion gel electrolyte layer is covered with a Prussian blue nanolayer to form an ion storage layer.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. The electrochromic spirally coated piezoelectric composite yarn provided by the present invention realizes a multimodal response from mechanical stimulation perception to electrical signal transmission, and from electrical signal transmission to visual feedback through the coordinated design of the spirally cross-coated nanofiber layer and the packaging layer: when the electrochromic spirally coated piezoelectric composite yarn is subjected to external force, the spirally coated nanofiber layer converts mechanical energy into an electrical signal, and the electrical signal is transmitted to the electrochromic active layer through the transparent conductive layer on the surface of the packaging layer, driving the migration of ions between the active layer and the ion storage layer through the ion gel electrolyte layer, triggering real-time color change; at the same time, the spiral cross-coating structure enhances the interfacial bonding force between the piezoelectric layer and the silver-plated nylon core yarn, and combined with the moisture resistance and bending resistance of the packaging layer and the solidified layer, significantly improves the mechanical durability and functional stability of the material in complex environments.

[0038] 2. The preparation method of the electrochromic spiral-coated piezoelectric composite yarn provided by the present invention optimizes stress transfer and charge accumulation by using a silver-plated nylon core yarn as a conductive core yarn and forming a nanofiber layer. By encapsulating the nanofiber layer, the hydrophobicity, mechanical stability and environmental adaptability of the electrochromic spiral-coated piezoelectric composite yarn are improved. At the same time, it also suppresses moisture penetration and friction loss, so that the output voltage fluctuation of the electrochromic spiral-coated piezoelectric composite yarn is less than the preset range within the preset temperature range. The present invention realizes self-powered color change driven by piezoelectric signals by sequentially arranging a transparent conductive layer, an electrochromic active layer and an ion storage layer on the upper surface of the encapsulation layer, while improving the external stress transfer efficiency and charge collection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 1 is a schematic flow chart of a method for preparing an electrochromic spiral-coated piezoelectric composite yarn provided by an embodiment of the present invention;

[0040] Figure 2 Schematic diagram of the structure of a yarn spiral coating device provided by an embodiment of the present invention;

[0041] Figure 3 2 is a schematic diagram of a piezoelectric output performance test curve of an electrochromic spiral-coated piezoelectric composite yarn provided by an embodiment of the present invention;

[0042] Figure 4 This is a mechanical performance test diagram of the electrochromic spiral-coated piezoelectric composite yarn provided by an embodiment of the present invention.

[0043] Reference numerals: 1 - double helical chuck device; 2 - silver-plated nylon core yarn; 3 - sliding device; 4 - nanofiber layer. DETAILED DESCRIPTION

[0044] The technical solution of the present invention is described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations on the technical solution of the present invention. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0045] Example 1

[0046] This embodiment introduces an electrochromic spiral-coated piezoelectric composite yarn, comprising:

[0047] A silver-plated nylon core yarn and a nanofiber layer, an encapsulation layer, a transparent conductive layer, an electrochromic active layer, an ion gel electrolyte layer and an ion storage layer which are sequentially arranged on the outside of the silver-plated nylon core yarn.

[0048] Among them, the nanofiber layer is PVDF / BaTiO3 nanofiber yarn spirally cross-wrapped on the surface of silver-plated nylon core yarn, the transparent conductive layer is formed by curing PEDOT:PSS conductive polymer dispersion, the electrochromic active layer is tungsten trioxide nanowires uniformly deposited on the transparent conductive layer, and the ion storage layer is a Prussian blue nanolayer.

[0049] In this embodiment, the number of coating layers of the nanofiber layer is 2-8;

[0050] And / or, the thickness of the transparent conductive layer is 0.5-2 μm;

[0051] and / or, the thickness of the electrochromic active layer is 5-20 μm;

[0052] and / or, the thickness of the ion storage layer is 3-15 μm;

[0053] and / or, the thickness of the ion gel electrolyte layer is 10-30 μm;

[0054] And / or, the encapsulation layer is a PDMS encapsulation layer with a thickness of 20-30 μm.

[0055] In this embodiment, the silver-plated nylon core yarn serves as the conductive yarn core of the electrochromic spiral-coated piezoelectric composite yarn. Its silver plating treatment gives the core yarn high conductivity, which can efficiently transmit the electrical signals generated by the piezoelectric layer; the nylon substrate retains flexibility and mechanical strength, which can serve as the supporting skeleton of the nanofiber layer and ensure that the electrochromic spiral-coated piezoelectric composite yarn maintains structural stability during dynamic deformation, avoiding functional failure due to core yarn breakage.

[0056] In this embodiment, the spirally cross-wrapped nanofiber layer significantly improves the piezoelectric performance through a multi-layer structural design: the spiral cross-wrapping method increases the contact area between the nanofiber and the core yarn, and strengthens the interfacial bonding force; this embodiment improves the piezoelectric coefficient of PVDF through the piezoelectric enhancement effect by introducing barium titanate nanoparticles, and the multi-layer structure further optimizes the stress distribution, so that when the electrochromic spiral-wrapped piezoelectric composite yarn is subjected to external force, the piezoelectric layer can respond uniformly and output a stable electrical signal, avoiding the stress concentration or signal attenuation problems that are prone to occur in single-layer coating.

[0057] In this embodiment, the PDMS encapsulation layer balances environmental adaptability and flexibility through a thickness design of 20-30 μm. The hydrophobicity and chemical stability of PDMS can effectively block erosion by water vapor, sweat or seawater, and avoid the decrease of β-phase crystallinity caused by moisture absorption of the nanofiber layer; at the same time, the thickness of 20-30 μm retains the flexibility of the electrochromic spiral-coated piezoelectric composite yarn, ensuring that it does not crack or fall off during dynamic deformation, significantly improving the durability of the nanofiber layer in complex environments.

[0058] In this embodiment, the transparent conductive layer achieves a synergistic combination of high transmittance and low resistivity. The thickness of 0.5-2 μm avoids the decrease in transmittance caused by excessive thickness while ensuring conductivity by optimizing the film-forming quality of PEDOT:PSS. The transparent conductive layer serves as the electrode of the electrochromic active layer and can efficiently transmit the electrical signals generated by the piezoelectric layer while retaining the transparent properties of the electrochromic spiral-coated piezoelectric composite yarn.

[0059] In this embodiment, the electrochromic active layer accelerates the lithium ion Li + and hydrogen ions H + The embedding / extraction of plasma and the thickness of 5-20μm optimize the color change speed and cycle stability; when the electrical signal output by the piezoelectric layer is applied to the electrochromic active layer, the tungsten trioxide nanowires can quickly undergo redox reactions to trigger obvious color changes, realizing visual feedback of mechanical stimulation.

[0060] In this embodiment, the Prussian blue ion storage layer covering the electrochromic active layer balances the charge in the electrochromic process through its high ion storage capacity, and the thickness of 3-15μm adjusts the ion buffering capacity; when the active layer undergoes an oxidation reaction, the Prussian blue can synchronously receive and store ions of opposite charge, maintain the charge balance of the system, avoid color shift or failure due to charge accumulation, and significantly improve the cyclic stability of the electrochromic function.

[0061] In this embodiment, the ion gel electrolyte layer provided between the transparent conductive layer and the ion storage layer promotes the transfer of lithium ions Li + and hydrogen ions H + The rapid migration of plasma between the active layer and the storage layer, and the thickness of 10-30 μm balance the ion transmission efficiency and yarn flexibility; the ion gel electrolyte layer acts as an ion transmission channel, which can respond to the electrical signal output by the piezoelectric layer, driving the ions to migrate directionally between the tungsten trioxide active layer and the ion storage layer formed by Prussian blue, realizing the rapid response and low-voltage drive of the electrochromic function, adapting to the low power consumption requirements of wearable devices.

[0062] In this embodiment, the 6 V voltage generated by the composite electrochromic layer under a pressure of 10 N can directly trigger the blue / white state switching. Figure 4 and as shown in Table 1.

[0063] Table 1 Piezoelectric electrochromic synergistic performance test data Test conditions Performance parameters 10 N pressure drive Output voltage: 6.0 ± 0.2 V Transmittance change (ΔT): 42% Color switching time: 4.3 s Underwater 90° bend Output voltage: 0.31 V → triggers light blue color change

[0064] Example 2

[0065] like Figure 1 As shown, this embodiment introduces a method for preparing an electrochromic spiral-coated piezoelectric composite yarn, comprising:

[0066] Step 1: The PVDF / BaTiO3 nanofiber yarn is spirally cross-wrapped along the axial direction of the silver-plated nylon core yarn to form a nanofiber layer.

[0067] Step 1.1: Fix the silver-plated nylon core yarn 2 on the double spiral chuck device 1 of the yarn spiral coating device and control the twisting speed of the silver-plated nylon core yarn 2 to be 500 r / min. The yarn spiral coating device used in this embodiment is as follows: Figure 2 shown.

[0068] Step 1.2: Use the sliding device 3 to spirally cross-wrap the PVDF / BaTiO3 nanofiber yarn along the axial direction of the silver-plated nylon core yarn 2 at a first linear speed, and at the same time form the nanofiber layer 4 by adjusting the speed of the sliding device 3.

[0069] Step 1.2.1: Prepare the PVDF / BaTiO3 nanofiber yarn by electrospinning.

[0070] The PVDF masterbatch was dissolved in dimethylformamide solvent to prepare a 15 wt% PVDF solution, and magnetically stirred in a 60 °C water bath for 2 h until it was completely dissolved.

[0071] Barium titanate nanopowder accounting for 10 wt% of PVDF was weighed and added to the above solution. After ultrasonic dispersion for 12 h, a uniformly dispersed spinning solution was obtained.

[0072] The spinning solution was injected into the electrospinning nozzle with a voltage of 15 kV and a receiving distance of 15 cm, and six layers of silver-plated nylon core yarn were reciprocally cross-wrapped and dried at 60°C for 2 h to remove the residual solvent to obtain PVDF / BaTiO3 nanofiber yarn.

[0073] In this embodiment, the calculation expression of the twist between the silver-plated nylon core yarn and the nanofiber layer is expressed as:

[0074] ;

[0075] Where, represents the twist between the silver-plated nylon core yarn and the nanofiber layer, in r / m, Indicates the speed of the silver-plated nylon core yarn in m / min. It represents the wrapping speed of the nanofiber layer in m / min.

[0076] In this embodiment, the speed adjustment range of the sliding device 3 is 300-700 r / min. When the speed of the sliding device is adjusted to 300 r / min, 500 r / min, and 700 r / min, respectively, the twist of the corresponding PVDF / BaTiO3 nanofiber yarn is 2400 TPM, 1600 TPM, and 1000 TPM, respectively.

[0077] Step 2: Encapsulate the nanofiber layer with PDMS as a curing liquid to form an encapsulation layer, and immerse it in a PEDOT:PSS conductive polymer dispersion to form a transparent conductive layer.

[0078] Step 2.1: Mix the base glue and PDMS in a mass ratio of 10:1, stir for 30 minutes, and then stand for pre-curing for 12 hours to obtain a PDMS solution.

[0079] In this embodiment, the base glue is a liquid silicone prepolymer.

[0080] Step 2.2: Immerse the nanofiber layer in the PDMS solution, apply it by brush for 5 minutes to ensure uniform coverage, then straighten and fix it at 60°C and dry it for 30 minutes for secondary curing to form an encapsulation layer with a thickness of about 20-30 μm.

[0081] In this embodiment, the hydrophobicity of the encapsulated nanofiber layer reaches 124°.

[0082] In this embodiment, COMSOL is used to simulate the interfacial stress distribution between the packaging layer and the nanofiber layer 4, and the thickness of the packaging layer is optimized to 20-30 μm, so that the surface potential difference between the silver-plated nylon core yarn 2 and the nanofiber layer 4 is maximized to 6 V. At the same time, the separation distance between the two is stably controlled at 15 mm, which significantly improves the charge separation efficiency and power output performance of the piezoelectric nanofiber layer.

[0083] In this embodiment, the fracture strength retention rate of the encapsulation layer after 50 times of 20% strain stretching is ≥95%, and the output voltage stability deviation after 7500 cycle tests is ≤3%.

[0084] Step 3: Immerse the encapsulated nanofiber layer in a PEDOT:PSS conductive polymer dispersion (solid content 1.5 wt%) and dry it at 60°C for a preset time to form a transparent conductive layer.

[0085] Step 4: Form an electrochromic layer by spraying a tungsten trioxide nanowire ethanol suspension on the surface of the transparent conductive layer.

[0086] In this embodiment, the voltage of the electrostatic spraying is set to 12 kV, and a 20 mg / mL tungsten trioxide nanowire ethanol suspension is electrostatically sprayed to uniformly deposit the tungsten trioxide nanowires on the surface of the transparent conductive layer. After drying, an electrochromic active layer with a thickness of 10±2 μm is formed.

[0087] Step 5: Spin-coating an ion gel electrolyte on the surface of the electrochromic layer and curing the ion gel electrolyte layer;

[0088] The ion gel electrolyte layer is covered with a Prussian blue nanolayer to form an ion storage layer.

[0089] Example 3

[0090] This embodiment provides a comparative verification method for electrochromic spiral-coated piezoelectric composite yarn. In order to verify and illustrate the technical effects adopted in this method, this embodiment adopts a traditional technical solution and the method of the present invention for comparative testing, and compares the test results by means of scientific demonstration to verify the real effect of this method.

[0091] 1. Comparative experiment:

[0092] Experiment 1: Barium titanate doping concentration comparison experiment:

[0093] Experimental purpose: To verify whether barium titanate affects the charge transfer efficiency of electrochromic spiral-coated piezoelectric composite yarn.

[0094] Experimental variables: Barium titanate doping concentration: 5 wt%, 10 wt%, 15 wt%.

[0095] Experimental steps:

[0096] (1) Prepare three spinning solution systems, including:

[0097] System A: 15 wt% PVDF + 5 wt% barium titanate;

[0098] System B: 15 wt% PVDF + 10 wt% barium titanate;

[0099] System C: 15 wt% PVDF + 15 wt% barium titanate;

[0100] (2) The three spinning solutions of system A, system B and system C were ultrasonically dispersed for 12 h to obtain uniformly dispersed spinning solutions. The spinning solutions were injected into an electrospinning nozzle with a voltage of 15 kV and a receiving distance of 15 cm, and then reciprocally cross-wrapped with three identical silver-plated nylon core yarns in 6 layers and dried at 60 °C for 2 h to remove the residual solvent, thereby obtaining three types of PVDF / BaTiO3 nanofiber yarns.

[0101] (3) Three types of PVDF / BaTiO3 nanofiber yarns were spirally cross-wrapped along the axial direction of the silver-coated nylon core yarn to form nanofiber layers with the same number of coating layers;

[0102] (4) Encapsulating the nanofiber layer with PDMS as a curing liquid to form an encapsulation layer, and immersing it in a PEDOT:PSS conductive polymer dispersion to form a transparent conductive layer;

[0103] (5) forming an electrochromic layer by spraying a tungsten trioxide nanowire ethanol suspension on the surface of the transparent conductive layer;

[0104] (6) The ion gel electrolyte was spin-coated on the surface of the electrochromic layer and covered with a Prussian blue nanolayer after curing to form an ion storage layer, thereby obtaining three types of electrochromic spiral-coated piezoelectric composite yarns.

[0105] According to the barium titanate doping concentration comparison experiment and Figure 3 And Table 5, we can see that:

[0106] The electrochromic spiral-coated piezoelectric composite yarn made of 5 wt% barium titanate has an output voltage of 4.8 V, a low piezoelectric response sensitivity of 0.75 V / N, and a dielectric constant of 45; the electrochromic spiral-coated piezoelectric composite yarn made of 10 wt% barium titanate has an output voltage of 6.0 V, a significantly improved piezoelectric response sensitivity of 1.00 V / N, and a dielectric constant increased to 60; the electrochromic spiral-coated piezoelectric composite yarn made of 15 wt% barium titanate has an output voltage slightly decreased to 5.2 V, a piezoelectric response sensitivity of 0.85 V / N, and a dielectric constant of 55.

[0107] Experiments show that 10 wt% barium titanate is the optimal doping concentration, achieving the best balance between piezoelectric and dielectric properties. Doping concentrations too high, such as 15 wt%, can cause nanoparticles to agglomerate, affecting charge transfer efficiency.

[0108] Experiment 2: Comparison of the number of nanofiber coating layers:

[0109] Experimental purpose: To verify whether the number of nanofiber coating layers affects the piezoelectric response sensitivity and output voltage of electrochromic spiral-coated piezoelectric composite yarn.

[0110] Experimental variables: Number of nanofiber coating layers: 2 layers, 4 layers, 6 layers, and 8 layers.

[0111] Experimental steps:

[0112] (1) Prepare a spinning solution of 15 wt% PVDF + 10 wt% barium titanate;

[0113] (2) The spinning solution was ultrasonically dispersed for 12 h to obtain a uniformly dispersed spinning solution. The spinning solution was injected into an electrospinning nozzle with a voltage of 15 kV and a receiving distance of 15 cm. The spinning solution was reciprocally cross-wrapped with four identical silver-plated nylon core yarns in 6 layers and dried at 60 °C for 2 h to remove the residual solvent. Four types of PVDF / BaTiO3 nanofiber yarns were obtained.

[0114] (3) The four PVDF / BaTiO3 nanofiber yarns were spirally cross-wrapped along the axial direction of the silver-plated nylon core yarn at a first linear speed using the sliding device of the yarn spiral wrapping equipment. At the same time, 2, 4, 6, and 8 nanofiber layers were wrapped respectively by adjusting the speed of the sliding device.

[0115] (4) Encapsulating the nanofiber layer with PDMS as a curing liquid to form an encapsulation layer, and immersing it in a PEDOT:PSS conductive polymer dispersion to form a transparent conductive layer;

[0116] (5) forming an electrochromic layer by spraying a tungsten trioxide nanowire ethanol suspension on the surface of the transparent conductive layer;

[0117] (6) The ion gel electrolyte was spin-coated on the surface of the electrochromic layer and covered with a Prussian blue nanolayer after curing to form an ion storage layer, thereby obtaining four electrochromic spiral-coated piezoelectric composite yarns with different numbers of coating layers.

[0118] According to the comparison experiment of the number of nanofiber coating layers and Figure 4 and Table 5, where Figure 4 (a) represents the voltage of the electrochromic spiral-wrapped piezoelectric composite yarn modified with 10wt% barium titanate at different frequencies under a fixed force of 10 N, (b) represents the current of the electrochromic spiral-wrapped piezoelectric composite yarn modified with 10wt% barium titanate at different frequencies under a fixed force of 10 N, (c) represents the charge of the electrochromic spiral-wrapped piezoelectric composite yarn modified with 10wt% barium titanate at different frequencies under a fixed force of 10 N, (d) represents the charge of the electrochromic spiral-wrapped piezoelectric composite yarn at different forces at a fixed frequency of 3 Hz, (e) represents the current of the electrochromic spiral-wrapped piezoelectric composite yarn at different forces at a fixed frequency of 3 Hz, and (f) represents the charge of the electrochromic spiral-wrapped piezoelectric composite yarn at different forces at a fixed frequency of 3 Hz. It can be seen that:

[0119] The 2-layer coated electrochromic spiral coated piezoelectric composite yarn has an output voltage of 3.2 V, weak mechanical properties of 0.8 MPa, and a stress transfer efficiency of only 20%; the 4-layer coated electrochromic spiral coated piezoelectric composite yarn has an output voltage of 4.1 V, a tensile strength of 1.4 MPa, and an external stress transfer efficiency of 25%; the 6-layer coated electrochromic spiral coated piezoelectric composite yarn has an output voltage increased to 6.0 V, significantly enhanced mechanical properties of 1.8 MPa, and a stress transfer efficiency of 30%; the 8-layer coated electrochromic spiral coated piezoelectric composite yarn has an output voltage slightly reduced to 5.5 V, but the mechanical properties are further improved to 2.1 MPa.

[0120] Experiments show that 6 layers of coating are the optimal solution, taking into account both high voltage output and mechanical properties. Too many coating layers may lead to a decrease in yarn flexibility and affect practical applications.

[0121] Experiment 3: Packaging material comparison experiment:

[0122] Experimental purpose: To verify whether the packaging material of the packaging layer affects the performance of electrochromic spiral-wrapped piezoelectric composite yarn.

[0123] Experimental variables: Encapsulation material type: PDMS, thermoplastic polyurethane elastomer TPU (Thermoplastic Polyurethane).

[0124] Experimental steps:

[0125] Step 1: Preparation of electrochromic spiral-coated piezoelectric composite yarn encapsulated with PDMS as curing liquid:

[0126] (1) A spinning solution of 15 wt% PVDF + 10 wt% barium titanate was prepared. After ultrasonic dispersion for 12 h, a uniformly dispersed spinning solution was obtained. The spinning solution was injected into an electrospinning nozzle with a voltage of 15 kV and a receiving distance of 15 cm. The spinning solution was reciprocally cross-wrapped with four identical silver-plated nylon core yarns in 6 layers and dried at 60 °C for 2 h to remove the residual solvent, thereby obtaining PVDF / BaTiO3 nanofiber yarns.

[0127] (2) The PVDF / BaTiO3 nanofiber yarn is spirally cross-wrapped along the axial direction of the silver-coated nylon core yarn to form a nanofiber layer;

[0128] (3) The nanofiber layer is encapsulated with PDMS as a curing liquid to form an encapsulation layer, and then immersed in a PEDOT:PSS conductive polymer dispersion to form a transparent conductive layer;

[0129] (4) forming an electrochromic layer by spraying a tungsten trioxide nanowire ethanol suspension on the surface of the transparent conductive layer;

[0130] (5) The ion gel electrolyte is spin-coated on the surface of the electrochromic layer, and after curing, it is covered with a Prussian blue nanolayer to form an ion storage layer, thereby obtaining a PDMS-encapsulated electrochromic spiral-coated piezoelectric composite yarn.

[0131] Step 2: Preparation of an electrochromic spiral-coated piezoelectric composite yarn encapsulated with thermoplastic polyurethane (TPU) as a curing liquid:

[0132] (1) A spinning solution of 15 wt% PVDF + 10 wt% barium titanate was prepared. After ultrasonic dispersion for 12 h, a uniformly dispersed spinning solution was obtained. The spinning solution was injected into an electrospinning nozzle with a voltage of 15 kV and a receiving distance of 15 cm. The spinning solution was reciprocally cross-wrapped with four identical silver-plated nylon core yarns in 6 layers and dried at 60 °C for 2 h to remove the residual solvent, thereby obtaining PVDF / BaTiO3 nanofiber yarns.

[0133] (2) The PVDF / BaTiO3 nanofiber yarn is spirally cross-wrapped along the axial direction of the silver-coated nylon core yarn to form a nanofiber layer;

[0134] (3) The nanofiber layer is encapsulated with a thermoplastic polyurethane elastomer (TPU) solution as a curing liquid to form an encapsulation layer, and then immersed in a PEDOT:PSS conductive polymer dispersion to form a transparent conductive layer, including the following steps:

[0135] The base rubber and thermoplastic polyurethane (TPU) were mixed, stirred at 80°C for 4 hours until completely dissolved, and then allowed to stand for pre-curing for 12 hours to obtain a 15 wt% TPU solution.

[0136] The nanofiber layer wrapped with the nanofiber layer was immersed in a 15 wt% thermoplastic polyurethane elastomer (TPU) solution and brushed for 5 minutes to ensure uniform coverage. After straightening and fixing, the nanofiber layer was dried at 60°C for 30 minutes for secondary curing to form a thermoplastic polyurethane elastomer (TPU) encapsulation layer with uniform thickness. The encapsulation layer was dried at 60°C for 30 minutes for secondary curing to form an encapsulation layer with a thickness of about 20-30 μm.

[0137] (4) forming an electrochromic layer by spraying a tungsten trioxide nanowire ethanol suspension on the surface of the transparent conductive layer;

[0138] (5) The ion gel electrolyte is spin-coated on the surface of the electrochromic layer, and after curing, it is covered with a Prussian blue nanolayer to form an ion storage layer, thereby obtaining an electrochromic spiral-coated piezoelectric composite yarn encapsulated by thermoplastic polyurethane elastomer (TPU).

[0139] According to the packaging material comparison experiment and Figure 4 From Tables 4 to 6, we can see that:

[0140] PDMS-encapsulated electrochromic spiral-wrapped piezoelectric composite yarn: output voltage 6.0 V, hydrophobic angle of 124°, and excellent water-wash resistance, i.e., 98% retention rate;

[0141] Electrochromic spiral-wrapped piezoelectric composite yarn encapsulated by thermoplastic polyurethane elastomer (TPU): output voltage is 5.0 V, the hydrophobic angle is low, i.e. 92°, and the water washing resistance is poor, i.e. 85% retention rate.

[0142] Experiments show that PDMS significantly improves the environmental adaptability of electrochromic spiral-coated piezoelectric composite yarns due to its excellent hydrophobicity and interfacial stress optimization capabilities.

[0143] 2. Performance test:

[0144] The electrochromic spiral-coated piezoelectric composite yarns prepared in the above experiments were subjected to system performance tests. The specific test methods are as follows:

[0145] Piezoelectric Performance Testing: Piezoelectric constants were measured using a quasi-static D33 tester in accordance with GB / T 3389-2008, "Test Methods for Properties of Piezoelectric Ceramic Materials." The dielectric constant and electromechanical coupling coefficient were determined using an impedance analyzer. The test environment was maintained at 25±1°C and a relative humidity of 50±5%.

[0146] Dynamic energy harvesting test: Build a custom dynamic load simulation test platform, apply a 0.5-10N periodic load with a frequency of 1-5Hz, and record the changes in open-circuit voltage and short-circuit current in real time.

[0147] Hydrophobicity test: Surface contact angles were measured using a contact angle meter according to HY / T 266-2018. The test was conducted using a 3μL droplet of deionized water at 24°C.

[0148] Washability test: According to GB / T 3921-2008, the test was conducted using a standard washing machine type A. The test conditions were: detergent concentration 2g / L, water temperature 40°C, and each wash time 30 minutes.

[0149] Mechanical properties test: Tensile strength test is carried out in accordance with GB / T 14337-2008 standard using a universal material testing machine; fatigue performance test refers to ISO 12106:2017 "Metallic materials fatigue test - Axial force control method".

[0150] Electrochromic performance test: According to GB / T 25284-2010, Test Method for Optical Performance of Electrochromic Devices, the transmittance change ΔT is measured at a voltage of 0-6V within the wavelength range of 380-780nm, and the test is cycled for no less than 500 times.

[0151] The above comparative experiments and performance tests were performed by professionals in this field in strict accordance with relevant standard operating procedures. The detailed information of the experimental conditions and the experimental results are shown in Tables 2 to 6:

[0152] Table 2 Reagent specifications name Specification factory Silver-plated nylon yarn 210 D 3 shares Suzhou Tektronix Silver Fiber barium titanate 99.5% 3 μm McLean Biochemical Technology Co., Ltd. <![CDATA[PVDF / BaTiO3 nanofiber yarn]]> JDF05 Changsha Nayi Instrument Technology Co., Ltd. dimethylformamide analytically pure Shanghai Aladdin Biochemical Reagent Co., Ltd. Tetrahydrofuran (THF) analytically pure Shanghai Titan Technology Co., Ltd. PDMS Dow Corning DC184 The Dow Chemical Company Thermoplastic polyurethane elastomer TPU Elastollan® 1185A10 BASF PI tape 0.05 mm Suzhou Zhihe Adhesive Products Conductive copper foil tape 0.1 mm Shenzhen Benyida Technology Co., Ltd. Prussian blue nanoparticles Particle size 100 nm McLean Biotechnology PEDOT:PSS dispersion Solid content 1.5 wt% Suzhou Nanotech Tungsten trioxide nanowires Purity 99.9%, Ø50 nm Aladdin Reagent

[0153] Table 3 Comparison of experimental data of barium titanate doping concentration Barium titanate doping concentration (wt%) Output voltage (V) Piezoelectric response sensitivity (V / N) Dielectric constant (ε) 5 4.8 0.75 45 10 6.0 1.00 60 15 5.2 0.85 55

[0154] Table 4 Comparative experimental data of the number of nanofiber coating layers Number of coating layers Output voltage (V) Mechanical properties (MPa) External stress transmission efficiency (%) 2 3.2 0.8 20 4 4.1 1.4 25 6 6.0 1.8 30 8 5.5 2.1 28

[0155] Table 5 Packaging material comparison experimental data Packaging material type Output voltage (V) Contact angle (°) Water washing cycle performance (%) PDMS 6.0 124 98 Thermoplastic polyurethane elastomer TPU 5.0 92 85

[0156] Table 6 Mechanical properties test data Test conditions Performance parameters After 50 times of 20% strain stretching Strength retention rate: ≥95% After folding thousands of times Deformation recovery rate: ≥98% 7500 cycle test Output voltage stability deviation: ≤3%

[0157] In summary, the electrochromic spiral-coated piezoelectric composite yarn provided by the present invention is encapsulated by using PDMS as a curing liquid for the nanofiber layer, and the PDMS encapsulation layer is formed by multiple brushing and drying. Based on the hydrophobic properties and interfacial stress optimization of the PDMS encapsulation layer, when the thickness is adjusted to 20-30 μm, the hydrophobic angle reaches 124°. In addition, the present invention provides an ion gel electrolyte layer between the transparent conductive layer and the ion storage layer, and adopts a spiral cross-coating structure, that is, the spiral directions of adjacent nanofiber layers change alternately, thereby ensuring that the voltage attenuation rate of the electrochromic spiral-coated piezoelectric composite yarn does not exceed 5% after 10 standard water washes, and can still stably output a voltage of 0.3V when bent 90° underwater. The synergistic effect of these technical features enables the nanofiber layer to maintain stable performance in complex environments such as moisture and water washing, broadening the application scenarios. It is particularly suitable for wearable devices and other fields that may come into contact with water or humid environments.

[0158] The electrochromic spiral-coated piezoelectric composite yarn provided by the present invention adopts a spiral cross-coating structure and, based on the piezoelectric response characteristics of the nanofiber layer, can stably output a 6V voltage under a 3Hz dynamic load and can charge a 1μF capacitor to 0.4V within 20 seconds; at the same time, the twist of the nanofiber layer is optimized by jointly regulating the spiral speed of the double-helical chuck device and the first linear speed of the PVDF / BaTiO3 nanofiber yarn, ensuring that the output voltage is not less than 6V under a pressure of 10N. These technical features enable the electrochromic spiral-coated piezoelectric composite yarn to provide reliable power support for small electronic devices, meeting the needs for continuous and stable power supply in scenarios such as wearable energy supply and motion monitoring.

[0159] The electrochromic spiral-coated piezoelectric composite yarn provided by the present invention, by adopting a spiral cross-coating structure and adjusting the thickness of the PDMS encapsulation layer to 20-30 μm, can withstand letter deformation such as the letters A / D / U / S and multiple folding and curling, with a deformation recovery rate of ≥98%, thereby optimizing the flexibility and interfacial stress of the PDMS encapsulation layer. At the same time, the present invention uses the flexible conductive support function of the silver-plated nylon core yarn and the spiral coating reinforcement effect of the nanofiber layer to ensure that the electrochromic spiral-coated piezoelectric composite yarn retains ≥95% of its strength after 50 times of 20% strain stretching and can withstand 10,000 foldings. The synergistic effect of these technical features gives the electrochromic spiral-coated piezoelectric composite yarn excellent mechanical properties, making it less susceptible to damage in frequently deformed use environments, extending its service life and reducing its cost.

[0160] The electrochromic spiral-coated piezoelectric composite yarn provided by the present invention improves the external stress transmission efficiency by adopting a spiral cross-coating structure and a multi-layer spiral coating design based on a nanofiber layer. When the number of coating layers is 2-8 layers, the external stress transmission efficiency is improved by ≥30%. At the same time, the present invention also optimizes the interfacial stress through the efficient conductive properties of the silver-plated nylon core yarn and the PDMS encapsulation layer. When the thickness of the PDMS encapsulation layer is adjusted to 20-30 μm, the charge collection efficiency is improved by ≥25%. The synergistic effect of these technical features significantly improves the stress-electrical energy conversion efficiency, so that more electricity can be generated under the same external force, thereby improving energy utilization efficiency and enhancing power generation capacity.

[0161] The electrochromic spiral-coated piezoelectric composite yarn provided by the present invention has an electrochromic active layer. The 6V voltage generated under a pressure of 10N can directly trigger the blue / white state switching. The 6V voltage under a pressure of 10N triggers a transmittance change ΔT≥40%, and the switching time is ≤5s. The self-powered electrochromic characteristics enable it to achieve color changes without an additional power supply. It is suitable for fields such as smart color-changing fabrics, adding unique visual effects and intelligent interactive functions to the products.

[0162] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which are all protected by the present invention.

Claims

1. An electrochromic spiral-coated piezoelectric composite yarn, characterized in that: The invention comprises a silver-plated nylon core yarn and a nanofiber layer, an encapsulation layer, a transparent conductive layer, an electrochromic active layer, an ion gel electrolyte layer and an ion storage layer which are sequentially arranged on the outside of the silver-plated nylon core yarn; Among them, the nanofiber layer is PVDF / BaTiO3 nanofiber yarn spirally cross-wrapped on the surface of silver-plated nylon core yarn, the transparent conductive layer is formed by curing PEDOT:PSS conductive polymer dispersion, the electrochromic active layer is tungsten trioxide nanowires uniformly deposited on the transparent conductive layer, and the ion storage layer is a Prussian blue nanolayer.

2. The electrochromic spiral-coated piezoelectric composite yarn according to claim 1, characterized in that: The number of coating layers of the nanofiber layer is 2-8; And / or, the thickness of the transparent conductive layer is 0.5-2 μm; and / or, the thickness of the electrochromic active layer is 5-20 μm; and / or, the thickness of the ion storage layer is 3-15 μm; And / or, the thickness of the ion gel electrolyte layer is 10-30 μm.

3. The electrochromic spiral-coated piezoelectric composite yarn according to claim 1, characterized in that: The encapsulation layer is a PDMS encapsulation layer with a thickness of 20-30 μm.

4. A method for preparing the electrochromic spiral-coated piezoelectric composite yarn according to any one of claims 1 to 3, characterized in that: include: The PVDF / BaTiO3 nanofiber yarn was spirally cross-wrapped along the axial direction of the silver-coated nylon core yarn to form a nanofiber layer; The nanofiber layer is encapsulated with PDMS as a curing liquid to form an encapsulation layer, and then immersed in a PEDOT:PSS conductive polymer dispersion to form a transparent conductive layer; An electrochromic layer is formed by spraying a tungsten trioxide nanowire ethanol suspension on the surface of the transparent conductive layer; The ion gel electrolyte is spin-coated on the surface of the electrochromic layer and covered with a Prussian blue nanolayer after curing to form an ion storage layer.

5. The method for preparing the electrochromic spiral-coated piezoelectric composite yarn according to claim 4, characterized in that: The calculation expression of the twist between the silver-plated nylon core yarn and the nanofiber layer is expressed as: ； Where, represents the twist between the silver-plated nylon core yarn and the nanofiber layer, in r / m, Indicates the speed of the silver-plated nylon core yarn in m / min. It represents the wrapping speed of the nanofiber layer in m / min.

6. The method for preparing the electrochromic spiral-coated piezoelectric composite yarn according to claim 5, characterized in that: The thickness of the solidified layer was adjusted to 20-30 μm by simulating the interfacial stress distribution between the encapsulation layer and the nanofiber layer using COMSOL.

7. The method for preparing the electrochromic spiral-coated piezoelectric composite yarn according to claim 4, characterized in that: The preparation method of the PVDF / BaTiO3 nanofiber yarn comprises: Dissolve the PVDF masterbatch in dimethylformamide solvent to prepare a 10-20 wt% PVDF solution, and stir magnetically in a 60°C water bath for 1-3 hours until completely dissolved; Weigh 5-15 wt% of barium titanate nanopowder based on the mass of the PVDF masterbatch and add it to the above solution. After ultrasonic dispersion for 8-16 hours, a uniformly dispersed spinning solution is obtained. The spinning solution was injected into the electrospinning nozzle and reciprocatingly cross-wrapped with 4-8 layers of silver-plated nylon core yarn and dried at 60°C for 1-3 h to remove the residual solvent to obtain PVDF / BaTiO3 nanofiber yarn.

8. The method for preparing the electrochromic spiral-coated piezoelectric composite yarn according to claim 4, characterized in that: The method of encapsulating the nanofiber layer using PDMS as a curing liquid to form an encapsulation layer comprises: Mix the base glue and PDMS in a mass ratio of 8:1-12:1, stir for 20-40 minutes, and then stand for pre-curing for 10-14 hours to obtain a PDMS solution; The nanofiber layer was immersed in the PDMS solution and brushed for 3-7 minutes to ensure uniform coverage. After that, it was straightened and fixed and dried at 60°C for 20-40 minutes for secondary curing to form an encapsulation layer with a thickness of about 20-30 μm.

9. The method for preparing the electrochromic spiral-coated piezoelectric composite yarn according to claim 4, characterized in that: The method for preparing the electrochromic active layer comprises: The tungsten trioxide nanowires were evenly deposited on the surface of the transparent conductive layer by electrostatic spraying of an ethanol suspension of tungsten trioxide nanowires with a concentration of 15-25 mg / mL. After drying, an electrochromic active layer with a thickness of 10±2 μm was formed.

10. The method for preparing the electrochromic spiral-coated piezoelectric composite yarn according to claim 4, characterized in that: The method for preparing the ion storage layer comprises: Spin-coating an ion gel electrolyte on the surface of the electrochromic layer to form an ion gel electrolyte layer after curing; The ion gel electrolyte layer is covered with a Prussian blue nanolayer to form an ion storage layer.

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