Preparation method of multi-scale cross-linked dual-network C-lignin / graphene oxide composite triboelectric film

Abstract

The invention discloses a preparation method of a multi-scale cross-linked dual-network C-lignin / graphene oxide composite triboelectric film, and belongs to the technical field of biomass-based triboelectric functional materials. The method comprises the following steps: dissolving polyvinyl alcohol (PVA), adding sodium alginate (SA) to construct a dual-network matrix, and introducing graphene oxide (GO) to form a reinforcing system; then dissolving C-lignin (CL) in dimethyl sulfoxide (DMSO), then adding the solution into the system, performing heating reaction to obtain casting liquid, and finally performing casting film forming, drying and constant humidity treatment to prepare the multi-scale cross-linked biomass-based composite triboelectric film. The obtained film realizes structural compactness and mechanical enhancement through collaborative crosslinking of a GO sheet layer and CL, has good flexibility and durability, can be used for constructing a triboelectric nano-generator and a self-powered sensor, and realizes electrical signal output and health monitoring of mechanical stimulation such as human motion; meanwhile, raw material sources are renewable, the preparation process is simple and convenient, conditions are mild, and the method is suitable for large-scale preparation and wearable device integration.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, specifically relating to a method for preparing a multi-scale cross-linked dual-network C-lignin / graphene oxide composite triboelectric thin film. Background Technology

[0002] With the rapid development of wearable electronics, intelligent sensing, and human-computer interaction technologies, how to efficiently acquire and utilize low-frequency mechanical energy such as human motion has become a crucial issue in the field of self-powered electronic systems. Triboelectric nanogenerators can directly convert mechanical stimuli into electrical signals, offering significant application value in motion monitoring, health sensing, and intelligent interaction. As the core functional layer of triboelectric devices, the structural stability and mechanical reliability of triboelectric thin films directly affect the output performance and lifespan of the devices. Existing triboelectric thin films are mostly prepared using a single polymer matrix or simple filler composite method. Under repeated pressing, bending, or impact conditions, structural relaxation or microcrack propagation easily occurs, leading to electrical output attenuation or even failure. Simultaneously, the dispersion stability and interfacial bonding ability of functional components in the film are limited, making it difficult to achieve an effective balance between flexibility, strength, and durability, thus limiting practical application effectiveness. Furthermore, some current triboelectric thin films still rely on petroleum-based polymer materials or complex, energy-intensive preparation processes, which is detrimental to green manufacturing and sustainable development. Therefore, developing a biomass-based triboelectric thin film preparation method that is structurally stable and suitable for self-powered sensing applications based on renewable biomass materials is of great significance for promoting the practical application of green flexible electronics and triboelectric devices. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for preparing a multi-scale cross-linked dual-network C-lignin / graphene oxide composite triboelectric thin film, so that the prepared film has the characteristics of dense structure, strong interfacial bonding, good flexibility and durability, and can be used for the construction of triboelectric nanogenerators and self-powered sensors to achieve stable electrical signal output.

[0004] The present invention solves the above-mentioned technical problems through the following technical solution:

[0005] This invention discloses a method for preparing a multi-scale cross-linked dual-network C-lignin / graphene oxide composite triboelectric thin film, comprising the following steps:

[0006] (1) Add polyvinyl alcohol (PVA) to deionized water and stir at 300-800 rpm for 1-3 h at 90-98℃ to completely dissolve it, to obtain a PVA solution; add sodium alginate (SA) to the PVA solution and continue stirring at 300-800 rpm for 1-3 h to obtain a PVA / SA mixed solution.

[0007] (2) Add graphene oxide (GO) aqueous dispersion to the PVA / SA mixed solution obtained in step (1) and disperse at 300-800 rpm for 0.5-2 h to obtain the first film-forming mixture;

[0008] (3) Dissolve C-lignin (CL) in a polar organic solvent to obtain a CL mixed solution. Add the CL mixed solution to the first film-forming mixture obtained in step (2) at 85-95°C and stir for 0.5-2 h. Cool to obtain a casting liquid.

[0009] (4) The casting liquid is cast into a film. First, the polar organic solvent is removed by drying treatment to induce the film-forming system to concentrate and densify. Then, the dried film is subjected to constant humidity treatment to induce the hydration rearrangement and crystal reconstruction of the dual network system, thereby obtaining a C-lignin / graphene oxide composite triboelectric thin film with a multi-scale cross-linked dual network structure.

[0010] In step (1) of the present invention, the method for preparing a multi-scale cross-linked dual-network C-lignin / graphene oxide composite triboelectric thin film is characterized in that, in step (1), the amount of PVA is 2-5 g, the volume of deionized water is 30-80 mL, and the amount of SA is 0.5-2 g.

[0011] In step (2) of the present invention, the concentration of the GO aqueous dispersion is 0.5-5 mg / mL, and the added volume is 1-5 mL.

[0012] In step (3) of the present invention, the mass concentration of CL in the polar organic solvent is 5% to 30%, and the CL mixed solution is added to the first film-forming mixture in multiple batches, wherein "multiple batches" refers to more than 2 batches; the polar organic solvent is one or more of dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), ethylene glycol, and propylene glycol.

[0013] In step (4) of the present invention, the mold used for casting the film is a polytetrafluoroethylene mold, and the volume of the casting liquid is 10-30 mL; the drying temperature of the first stage is 40-80℃ and the time is 1-6 h; the relative humidity of the constant humidity treatment in the second stage is 40%-80% and the treatment time is 2-24 h; the thickness of the prepared film is 50-150 μm and the tensile strength exceeds 40 MPa; the film has a multi-scale cross-linked dual-network composite structure, including a PVA crystallization / physical cross-linking network, an SA network and bridging nodes composed of GO sheets and CL.

[0014] The present invention also provides a multi-scale cross-linked dual-network C-lignin / graphene oxide composite triboelectric thin film, which is prepared by the above-described method.

[0015] This invention also provides the application of the above-mentioned multi-scale cross-linked dual-network C-lignin / graphene oxide composite triboelectric thin film in self-powered materials.

[0016] This invention also provides the application of the above-mentioned multi-scale cross-linked dual-network C-lignin / graphene oxide composite triboelectric thin film in the preparation of a self-powered pressure sensor triboelectric nanogenerator.

[0017] This invention uses the aforementioned multi-scale cross-linked dual-network C-lignin / graphene oxide composite triboelectric thin film as the positive triboelectric material layer, a perfluoroethylene propylene copolymer (FEP) film as the negative triboelectric material layer, a double-sided copper (Cu) film as the electrode layer, and an acrylic sheet or polyethylene terephthalate (PET) sheet as the support layer. This triboelectric nanogenerator exhibits fast response time, excellent electrical signal output performance, outstanding environmental stability, and long operating cycle life.

[0018] The method of this invention constructs a dual-network matrix composed of polyvinyl alcohol and sodium alginate in the film-forming system, introduces the synergistic effect of graphene oxide and C-lignin, and uses a staged drying and constant humidity treatment process after casting to induce structural reconstruction of the material system, thereby producing a multi-scale cross-linked dual-network C-lignin / graphene oxide composite triboelectric thin film.

[0019] The C-lignin used in this invention is an aromatic polymer material derived from biomass. Its molecules contain abundant phenolic hydroxyl groups and polar groups, enabling it to participate in charge generation and transfer processes under external mechanical stimulation. By introducing C-lignin into the polymer film-forming system, the charge trapping ability and triboelectric properties of the material surface can be effectively controlled, which is an important way to improve the output performance of biomass-based triboelectric films.

[0020] Multi-scale cross-linked structures refer to the synergistic structures built simultaneously at the molecular, nanoscale, and network scales within the same thin film system. In this invention, polyvinyl alcohol and sodium alginate form an interpenetrating double network as the main supporting structure, graphene oxide sheets serve as two-dimensional reinforcement and bridging nodes, and C-lignin achieves uniform dispersion and participates in multi-point interactions under the action of polar solvents, thereby constructing a stable multi-scale cross-linked network structure. This structure is beneficial for improving the mechanical stability, structural durability, and consistency of triboelectric properties of the thin film.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] (1) By regulating the dual network structure and designing multi-scale crosslinking, the structure of biomass-based triboelectric thin films is stabilized. The preparation process is simple and the conditions are mild, which is in line with the development direction of green and sustainable materials.

[0023] (2) The triboelectric thin film prepared by the method of the present invention has both good flexibility and durability, and can achieve stable electrical signal output under periodic mechanical stimulation, making it suitable for applications such as triboelectric nanogenerators and self-powered sensors.

[0024] (3) The multi-scale cross-linked dual network structure described in this invention significantly improves the overall mechanical properties of the film. For example, when the amount of C-lignin added is 0.2 g, the tensile strength of the film can reach 41.56 MPa and the fracture toughness can reach 159.67 MJ / m³, which can effectively support the repeated bending and complex load requirements in wearable scenarios.

[0025] (4) The self-powered sensor constructed by the triboelectric thin film of the present invention has a fast dynamic response capability, for example, the response time and recovery time are 68 ms and 65 ms respectively, which can meet the requirements of real-time signal acquisition and stable output under high frequency mechanical excitation.

[0026] (5) The device described in this invention has high energy output and application availability, for example, when the external resistance is 10... 7 The instantaneous power density can reach 325.9 mW / m² at Ω, and a 22.0 μF capacitor can be charged to 3.0 V in 60 s; at the same time, the output remains stable after 2000 continuous cycle tests under different environmental conditions, demonstrating good durability and environmental adaptability. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the preparation process and structural design of the multi-scale cross-linked dual-network C-lignin / graphene oxide composite triboelectric thin film (PSGCL-0.2) in Example 1.

[0028] Figure 2 The image shown is a scanning electron microscope (SEM) image of PSGCL-0.2 in Example 1.

[0029] Figure 3 The tensile stress-strain curves are for composite films with different C-lignin (CL) contents in Example 1.

[0030] Figure 4 The ATR-FTIR spectrum of PSGCL-0.2 in Example 1 is shown.

[0031] Figure 5 The image shows the XRD pattern of PSGCL-0.2 in Example 1.

[0032] Figure 6 The thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) curves of PSGCL-0.2 in Example 1 are shown.

[0033] Figure 7 The UV-Vis transmittance curve of PSGCL-0.2 in Example 1 is shown.

[0034] Figure 8 The image shows the DPPH radical scavenging activity curve of PSGCL-0.2 in Example 1.

[0035] Figure 9 This is a schematic diagram illustrating the structure and working mechanism of the triboelectric nanogenerator (TENG) based on PSGCL-0.2 in Example 2.

[0036] Figure 10 The output curves of the open-circuit voltage (Voc) of TENG under different pressures in Example 2 are shown.

[0037] Figure 11 The stability test curves of TENG after 9 hours of cycling under different conditions are shown in Example 2.

[0038] Figure 12 The image shows two-dimensional small-angle X-ray scattering (2D-SAXS) patterns of PSGCL-0.2 in Test Example 1 at strains of 0% and 300%.

[0039] Figure 13 This is a schematic diagram of the Mott-Schottky curve and band structure of PSGCL-0.2 in Test Example 2. Detailed Implementation

[0040] To enable those skilled in the art to better understand the technical solutions described in this invention, the following embodiments are provided to better illustrate the invention, but the scope of protection of this invention is not limited to the following examples.

[0041] Example 1: Preparation of a multi-scale cross-linked dual-network C-lignin / graphene oxide composite triboelectric thin film (PSGCL-0.2)

[0042] This embodiment provides a method for preparing a multi-scale cross-linked dual-network C-lignin / graphene oxide composite triboelectric thin film, the specific steps of which are as follows:

[0043] (1) Add 3.0 g of polyvinyl alcohol (PVA) to 48 mL of deionized water and stir at 95 °C and 500 rpm for 2 h until completely dissolved. Add 1.0 g of sodium alginate (SA) to the solution and continue stirring under the same conditions for 2 h to obtain a homogeneous PVA / SA mixed solution.

[0044] (2) Add 2 mL of graphene oxide (GO) aqueous dispersion with a concentration of 2 mg / mL to the above mixed solution, stir and disperse at 500 rpm for 1 h to obtain the first film-forming mixture.

[0045] (3) Dissolve 0.2 g C-lignin (CL) in 2 mL dimethyl sulfoxide (DMSO) and slowly add it dropwise to the mixture in step (2) at 90 °C. Continue stirring for 1 h to obtain a uniform and viscous casting liquid.

[0046] (4) Pour 15 mL of casting liquid into a polytetrafluoroethylene mold and dry it in an oven at 60 °C for 3 h to remove the solvent and induce the system to concentrate and densify. Then place the initially dried membrane in an environment with a relative humidity of 60% for 12 h to complete the hydration-induced PVA / SA dual network rearrangement and crystal reconstruction, and finally obtain a composite film with a thickness of about 100 μm, denoted as PSGCL-0.2.

[0047] Figure 1 The above preparation process and the resulting multi-scale cross-linked dual-network structure are illustrated in the diagram. The surface morphology of the film was observed using scanning electron microscopy (SEM). Figure 2 As can be seen, the surface of PSGCL-0.2 exhibits continuous and dense groove-like textures and micro-nano aggregates, indicating that CL and GO are uniformly dispersed and form a tight interfacial bond with the PVA / SA matrix, with no significant phase separation.

[0048] Example 2: Fabrication of a triboelectric nanogenerator (TENG) based on PSGCL-0.2

[0049] This embodiment provides a method for preparing a triboelectric nanogenerator (TENG), the specific steps of which are as follows:

[0050] (1) Cut the PSGCL-0.2 film into squares of 2 cm × 2 cm as the positive electrode layer.

[0051] (2) A commercial fluorinated ethylene propylene copolymer (FEP) film is used as the negative electrode layer, double-sided copper foil is used as the electrode, and acrylic plate is used as the support layer.

[0052] (3) The PSGCL-0.2 and FEP film are respectively attached to both sides of the support layer, and the copper foil electrode is attached to the back and the wire is led out to form the TENG device.

[0053] Figure 9This demonstrates the structure and operating principle of the fabricated triboelectric nanogenerator (TENG). Electrical signals are transmitted via external wires. When the positive triboelectric material layer comes into contact with the negative triboelectric material layer, contact electrification occurs due to the difference in electron affinity. After separation, the charges remain on their respective surfaces, forming a potential difference. This potential difference drives electrons to flow back and forth through the external circuit, thereby outputting an electrical signal.

[0054] The performance of the TENG, including voltage, current, and charge, was tested using an electrometer (Keithley 6514) and a data acquisition card (NI-USB6259). A linear motor was used to control the TENG's operating frequency at 1 Hz, and the contact pressure was varied by an external load. Test conditions were maintained at approximately 40% RH humidity and 25°C. Figure 10 As shown, at a contact pressure of approximately 20 kPa, the open-circuit voltage (Voc) of the TENG reaches 102.5 V, and Voc increases linearly with increasing pressure, demonstrating good pressure sensitivity. The device underwent 2000 consecutive cycle tests. Figure 11 Its Voc output remains stable with negligible attenuation, proving that the TENG based on the thin film of this invention has excellent durability and reliability.

[0055] Example 3: A self-powered smart insole system based on PSGCL-0.2 for gait monitoring

[0056] This embodiment applies the PSGCL-0.2 thin film prepared in Example 1 to a self-powered pressure sensor. Utilizing the flexibility and TENG output performance of the PSGCL-0.2 thin film, PSGCL-0.2 is used as a triboelectric functional layer to construct an array device and achieve signal acquisition and recognition, specifically as follows: This embodiment integrates it into a smart insole to achieve wireless, self-powered plantar pressure monitoring.

[0057] (1) Cut the PSGCL-0.2 film into 48 independent sensing units and attach them to the PDMS spacer layer with copper foil electrodes.

[0058] (2) Based on the physiological characteristics of the foot (dense in the forefoot and heel, sparse in the arch), 48 sensor units are arrayed and integrated into the insole lining.

[0059] (3) The sensor array output is connected to the microcontroller (MCU) motherboard with built-in multi-channel ADC and Bluetooth module.

[0060] (4) Develop a mobile APP to receive real-time voltage signals via Bluetooth and use an interpolation algorithm to convert discrete signals into high-resolution plantar pressure distribution heat maps to achieve visual monitoring.

[0061] This system can achieve long-term, high spatiotemporal resolution gait monitoring without external power supply, demonstrating its application potential in intelligent interaction and wearable scenarios.

[0062] Comparative Example 1: Preparation of C-lignin-free composite film (PSG)

[0063] The only difference from Example 1 is that in step (3), CL is not added, but only an equal volume (2 mL) of pure DMSO solvent is added. The resulting film is denoted as PSG.

[0064] Comparative Example 2: Preparation of a composite film with excessively high C-lignin content (PSGCL-0.25)

[0065] The only difference from Example 1 is that the amount of CL added in step (3) is increased to 0.25 g. The resulting film is denoted as PSGCL-0.25.

[0066] Comparative Example 3: Preparation of a composite film (PSGPOL-0.2) based on traditional hardwood lignin

[0067] The only difference from Example 1 is that in step (3), C-lignin (CL) is replaced with an equal mass (0.2 g) of alkali lignin (POL). The resulting film is denoted as PSGPOL-0.2.

[0068] Test Example 1: Analysis of the Mechanical Properties and Microstructure Mechanism of Composite Thin Films

[0069] Tensile tests were performed on the films obtained in Example 1 and Comparative Examples 1-3. The results are as follows: Figure 3 As shown, the tensile strength (41.56 MPa), Young's modulus (41.25 MPa), and toughness (159.67 MJ / m³) of PSGCL-0.2 are significantly better than those of the comparative sample, demonstrating the significant enhancement effect of CL on mechanical properties through multi-scale crosslinking at appropriate content.

[0070] The structural evolution of PSGCL-0.2 under tension was analyzed using in-situ small-angle X-ray scattering (SAXS). Figure 12 As shown, under 300% strain, the SAXS spectrum changes from isotropic to significantly anisotropic, with the scattering peaks shifting to higher q values. This indicates that the stretch-induced polymer chains are highly oriented along the direction of the external force, resulting in a denser nanoscale structure. This is the microstructural basis for the material's high strength and high toughness.

[0071] Test Example 2: Chemical Properties, Multifunctionality, and Band Structure of Composite Thin Films

[0072] via ATR-FTIR ( Figure 4 ) and XRD ( Figure 5Chemical structure analysis revealed a shift in the -OH stretching vibration peak (~3419 cm⁻¹) of PSGCL-0.2, along with a decrease in XRD crystallization peak intensity. This confirmed the formation of strong hydrogen bonds between CL, GO, and the PVA / SA matrix, inhibiting excessive PVA crystallization and contributing to improved toughness. TGA-DSC curves ( Figure 6 The results show that PSGCL-0.2 has a higher char residue and glass transition temperature, indicating that its thermal stability is enhanced.

[0073] Testing multifunctional properties: UV-Vis spectrum ( Figure 7 The results show that PSGCL-0.2 has excellent shielding effect on the UVA-C band. DPPH free radical scavenging experiment ( Figure 8 This indicates that it has good antioxidant activity.

[0074] Band structure was analyzed by Mott-Schottky test and XPS valence band spectrum. Figure 13 The introduction of CL shifts the conduction band position of the composite film upwards and the valence band position downwards, significantly reducing the band gap from approximately 4.16 eV in the pure PVA / SA system to approximately 3.27 eV. The narrower band gap facilitates the generation of photogenerated carriers and the release of heat energy through non-radiative transitions, explaining the mechanism by which CL imparts efficient photothermal conversion capabilities to the material from an electronic structure perspective.

Claims

1. A method for preparing a multiscale crosslinked double network C-lignin / graphene oxide composite triboelectric film, characterized in that, The preparation method comprises the following steps: (1) adding polyvinyl alcohol (PVA) into deionized water, stirring at 300-800 rpm at 90-98 ℃ for 1-3 h to completely dissolve PVA, and obtaining a PVA solution; adding sodium alginate (SA) into the PVA solution, and continuing to stir at 300-800 rpm for 1-3 h to obtain a PVA / SA mixed solution; (2) adding a graphene oxide (GO) aqueous dispersion into the PVA / SA mixed solution obtained in step (1), and dispersing at 300-800 rpm for 0.5-2 h to obtain a first film-forming mixture; (3) dissolving C-lignin (CL) in a polar organic solvent to obtain a CL mixed solution, adding the CL mixed solution into the mixture obtained in step (2) at 85-95 ℃, and stirring and reacting for 0.5-2 h to obtain a casting liquid; (4) casting and cooling the casting liquid into a film, first performing drying treatment to remove the polar organic solvent to induce concentration and densification of the film-forming system; and then performing constant humidity treatment on the dried film to induce hydration rearrangement and crystallization reconstruction of the double network system, thereby obtaining a C-lignin / graphene oxide composite triboelectric film with a multi-scale cross-linked double network structure.

2. The method for preparing a multi-scale cross-linked dual-network C-lignin / graphene oxide composite triboelectric thin film according to claim 1, characterized in that, In step (1), the amount of PVA is 2-5 g, and the volume of deionized water is 30-80 mL; the amount of SA is 0.5-2 g.

3. The method for preparing a multi-scale cross-linked dual-network C-lignin / graphene oxide composite triboelectric thin film according to claim 1, characterized in that, In step (2), the concentration of the GO aqueous dispersion is 0.5-5 mg / mL, and the added volume is 1-5 mL.

4. The method for preparing a multi-scale cross-linked dual-network C-lignin / graphene oxide composite triboelectric thin film according to claim 1, characterized in that, In step (3), the mass concentration of CL in the polar organic solvent is 5%-30%, and the CL mixed solution is added into the film-forming mixture in multiple times, wherein the multiple times refer to 2 times or more; the polar organic solvent is one or more of dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methyl pyrrolidone (NMP), ethylene glycol, and propylene glycol.

5. The method for preparing a multi-scale cross-linked dual-network C-lignin / graphene oxide composite triboelectric thin film according to claim 1, characterized in that, In step (4), the mold used for casting the film is a polytetrafluoroethylene mold, and the volume of the casting liquid is 10-30 mL; the drying temperature is 40-80 ℃, and the drying time is 1-6 h; the relative humidity of the constant humidity treatment is 40%-80%, and the treatment time is 2-24 h; the prepared film has a thickness of 50-150 μm, and the tensile strength exceeds 40 MPa; the film has a multi-scale cross-linked double network composite structure, which comprises a PVA crystallization / physical cross-linking network, an SA network, and a bridging node composed of GO layers and CL.

6. A multiscale crosslinked dual-network C-lignin / graphene oxide composite triboelectric film, characterized in that, The preparation method is prepared by any one of claims 1-5.

7. The multi-scale cross-linked double network C-lignin / graphene oxide composite triboelectric film of claim 6 is applied in a triboelectric material layer.

8. The multi-scale cross-linked double network C-lignin / graphene oxide composite triboelectric film of claim 6 is applied in a self-powered pressure sensor.

9. Use of the multiscale cross-linked double network C-lignin / graphene oxide composite triboelectric thin film of claim 6 in the preparation of a triboelectric nanogenerator.

10. A triboelectric nanogenerator, characterized in that, The positive triboelectric material layer is the multiscale cross-linked double network C-lignin / graphene oxide composite triboelectric thin film of claim 6; the negative triboelectric material layer is one of a perfluoroethylene propylene copolymer (FEP) film, a polytetrafluoroethylene (PTFE) film, or a polyvinylidene fluoride (PVDF) film; the counter electrode layer is a metal electrode, the metal electrode is one of a copper foil, an aluminum foil, or a gold film; and the support layer is a flexible support substrate, the flexible support substrate is one of a polyethylene terephthalate (PET) sheet, a polyimide (PI) film, or an acrylic plate.

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