Reconfigurable graphene oxide ball fusion film and preparation method thereof

Abstract

The prior art graphene film structure is poor in precision, and once the intrinsic structure and mechanical properties are formed, it is difficult to greatly adjust them. The application provides a reconfigurable graphene oxide ball fusion film which is formed by mutual fusion and assembly of a plurality of graphene oxide balls after volume synergistic contraction. The graphene oxide ball comprises a core and a shell, and the shell wraps the core. The graphene oxide ball fusion film can be disassembled into a plurality of graphene oxide balls in a polar solvent. The reconfiguration times of assembly-disassembly are up to 20 times, arbitrary mutual conversion of the topologies of the ball fusion film is realized, including animal shape, house shape, submarine shape, tree shape and the like. The elongation at break of the ball fusion film is adjustable between 1.5% and 4%. By using the reversible contraction-swelling property of the graphene oxide ball, the macroscopic film of the fine structure formed by mutual fusion and assembly of a plurality of balls, and the reversible disassembly of the macroscopic film and the green recovery of the ball element are realized.

Description

Technical Field

[0001] This invention relates to the field of functional materials technology, and in particular to a reconfigurable graphene oxide spherical fused film and its preparation method. Background Technology

[0002] Graphene oxide is a novel monolayer two-dimensional material modified with oxygen-containing groups, exhibiting excellent self-assembly, self-healing, and mechanical properties. Stacking graphene oxide sheets layer by layer in a two-dimensional plane can produce macroscopic graphene oxide films, which have significant application value in smart response devices, water treatment, and gas separation. Although structural parameters such as layer orientation and interactions of graphene oxide films can be controlled through methods such as plasticizing and stretching, high-temperature reduction, and composite doping, traditional methods for controlling film structure make it difficult to directly mold the film into a specified precision structure. Furthermore, once the film is formed, its structure is difficult to significantly alter, limiting its intelligent applications. To improve the precision of film structure control, 3D printing is currently the primary method for generating pre-defined patterns or structures. However, this method generally requires printing in sections, resulting in low molding efficiency and hindering the fabrication of large-area customized films. Moreover, the film structure cannot be changed once fixed, and the graphene oxide raw material cannot be recycled and reused. The wrinkled structure of the film is difficult to control, and the intrinsic mechanical properties of the film are difficult to adjust. Due to limitations in structural adjustability, current intelligent membrane functions are mainly centered around stimulus-response actuation, severely hindering the development of novel intelligent membrane functions. Summary of the Invention

[0003] This invention addresses the problems of poor structural precision and the inability to significantly adjust the intrinsic structure and properties of existing membranes by providing a reconfigurable graphene oxide spherical fused membrane and its preparation method.

[0004] This invention utilizes the oxygen-containing functional groups of graphene oxide to perform specific structural design of graphene oxide, obtaining stimulus-responsive graphene oxide spheres. The presence of oxygen-containing functional groups makes graphene oxide highly sensitive to polar solvents; furthermore, they act as defects that can induce wrinkle formation. This invention effectively combines the above-mentioned characteristics of oxygen-containing functional groups with a core-shell structure design. Through the bulging and stretching of hill-like wrinkles, the graphene oxide spheres exhibit reversible three-dimensional large-volume contraction and expansion, undergoing large deformation under the stimulation of polar solvents. This results in large actuation deformation, high responsiveness, numerous cycles of reversible deformation, and a long service life.

[0005] This invention proposes using graphene oxide spheres with reversible shrinkage-expansion capabilities as the building blocks of macroscopic films. This solves the problems of traditional film fabrication methods that directly use single-layer graphene oxide sheets as building blocks, making it difficult to achieve precise film structures in a single step. Furthermore, the uneven internal stress during drying of customized film patterns leads to easy cracking and structural damage, and the intrinsic mechanical properties of the film are difficult to control. When using micron- to millimeter-sized graphene oxide spheres as the building blocks, the robust structure and reversible shrinkage-expansion of the spheres allow multiple spheres to adaptively shrink and fuse together to assemble into a macroscopic graphene oxide film. In this process, the relative positions of the building blocks are easier to control, enabling the fabrication of more refined macroscopic films, including complex animal-shaped topological films and beaded structures. Moreover, the uniform spherical building blocks effectively disperse the internal stress of the film, ensuring uniform drying without cracking, high forming efficiency, and maintaining structural precision and integrity. By changing the diameter of the spherical building blocks, the wrinkle density and intrinsic elongation at break of the film can be controlled, resulting in a customized macroscopic graphene oxide spherical fusion film.

[0006] Graphene oxide spheres are in a state of swelling in a polar solvent. Multiple swollen spheres are stacked together and fused together after drying to form a film. The film contains many spherical microcells, each formed by the drying and collapse of a single swollen sphere, with raised wrinkles at the cell edges. Therefore, the diameter of the microcell is smaller than the diameter of the swollen sphere. The smaller the diameter of the swollen sphere and the smaller the diameter of the microcell, the more wrinkles are formed at the cell edges per unit area, resulting in a higher wrinkle density. The wrinkles at the edges of the spherical microcells store strain energy, providing the amount of deformation that allows the graphene oxide sheets to be stretched. Therefore, the smaller the diameter of the spherical microcells, the higher the elongation at break of the fused film. The shape of the wrinkles at the edges of the spherical microcells is as follows: Figure 2 As shown in b and c, these are the protrusions at the edges of each spherical microcell within the membrane. These are formed by the bending, folding, and stacking of graphene oxide sheets along the edges of the swollen spheres after drying, resulting in closed rings.

[0007] Applications of spherical fusion membranes: 1. As a novel type of green recyclable membrane. Using polar solvents such as water, the membrane can be disassembled into several small spheres. These spheres can be fused together again to form membranes of other shapes when needed. The spheres can be recycled multiple times, achieving a novel green recycling and reuse of the membrane. Furthermore, using the spheres as the building blocks of the membrane allows for precise control of the membrane's contour structure, while ensuring uniform stress distribution during drying, making the membrane less prone to cracking.

[0008] 2. Used as a deformable smart membrane. For example, when a spherical fusion membrane is bonded together with a hydrophobic membrane, the bonded membrane will bend and deform or return to its original shape when the humidity changes, serving as a novel moisture-driven deformable membrane.

[0009] 3. Used as a membrane device for information encryption and reading. A spherical molten membrane is patterned and irradiated with ultraviolet light, causing a reduction reaction of graphene oxide in the irradiated areas, storing patterned or textual information. When information needs to be read, the spherical molten membrane is immersed in a polar solvent. The parts not reduced by ultraviolet light disintegrate into small spheres, while the parts reduced by ultraviolet light have significantly reduced hydrophilicity due to the reduction reaction of graphene oxide, preventing them from swelling and disintegrating into small spheres, thus forming a complete pattern or text, enabling the reading of patterned or textual information.

[0010] The significance of reconstruction: 1. It enables the membrane to be reconstructed into its original outline structure when needed after disassembly, achieving simple green recycling and multiple uses of the membrane; 2. Or, through reconstruction, the outline structure of the membrane can be changed, realizing the on-demand customization of the membrane structure, breaking through the limitation that the structure of the membrane is fixed once it is formed and cannot be flexibly adjusted or changed.

[0011] Secondly, through solvent swelling treatment, the curvature recovery of the spheres creates mechanical repulsion at the assembly interface, allowing the spherical molten film to be reversibly disassembled into spherical units of the original number, shape, and size. This enables the recycling and reassembly of these units, reconstructing macroscopic films with other fine structures and achieving film structure reconstruction. This avoids the problems of traditional graphene oxide films where strong π-π interactions between monolayer sheets lead to irreversible dispersion in a monolayer state, making it difficult to recover and reuse raw materials, and the inability to significantly alter the film structure once it is fixed. Through repeated disassembly and assembly, the spherical molten film structure can be reconstructed ≥1 times. The graphene oxide spherical molten film prepared by this invention has a thickness ≥1 μm, is composed of spherical microcells formed after the collapse of graphene oxide spheres, with a microcell diameter of 467 μm to 1052 μm, a dense cross-section, and a density ≥1.5 g / cm³. 3 It exhibits a tensile strength ≥40MPa and a reconfigurability ≥1. Furthermore, the fabrication process enables the precise topological structure to be formed in a single step, facilitating scale-up and achieving high forming efficiency. This endows macroscopic graphene oxide films with high structural precision and tunability, making them extremely important for applications in novel membrane materials such as green recyclable membranes, deformable smart membranes, and information encryption and reading membrane devices.

[0012] One of the technical solutions of the present invention is to provide a reconfigurable graphene oxide spherical fusion film, which is formed by the fusion assembly of several graphene oxide spheres after volume shrinkage; the graphene oxide spheres include a core and a shell, the shell encapsulating the core, the core being a network structure formed by overlapping graphene oxide sheets, and the shell being formed by overlapping graphene oxide sheets having a wrinkled structure; after several shells come into contact with each other and collapse, the network structure becomes dense, forming a spherical fusion film, which can be disassembled into the initial several graphene oxide spheres in a polar solvent.

[0013] When the polar solvent is removed from these core-shell structured graphene oxide spheres, the wrinkled structure of the shell graphene oxide bulges, the core network structure tightens and densifies, and the core-shell structure shrinks in three dimensions. When placed in a polar solvent, the wrinkled structure of the shell graphene oxide sheets relaxes, the core network structure unfolds, and the core-shell structure expands in three dimensions. In some embodiments of the present invention, the volume change rate during the shrinkage and expansion process is ≥90%, the Young's modulus changes from 10 kPa to 10 GPa (spanning up to 6 orders of magnitude), and the multi-level shape recovery rate is ≥90%, which has extremely important application value in biomimetic machines, biological tissue engineering, and wastewater treatment.

[0014] In a preferred embodiment of the present invention, the network structure is a porous network structure.

[0015] In a preferred embodiment of the present invention, a polar solvent is dispersed within the porous network structure. This graphene oxide-solvent composite system can achieve structural shrinkage directly through solvent removal. In this case, the solvent removal process directly induces the shrinkage of the graphene oxide sheets in the core portion, pulling the shell to form a smaller core-shell structure.

[0016] In a preferred embodiment of the present invention, the graphene oxide in the core portion has a wrinkled structure. When the polar solvent is removed, the wrinkled structure in the core portion bulges and shrinks together with the wrinkles in the graphene oxide in the shell portion. Similarly, those skilled in the art should know that the initial state of the wrinkled structure of the graphene oxide in the core portion can also be a hill-like low-wrinkle structure or a ridge-like high-wrinkle structure. The low-wrinkle structure has a greater shrinkage amount when the polar solvent is removed compared to the high-wrinkle structure, but as in the present invention, both low-wrinkle and high-wrinkle structures can achieve a solvent-stimulated response.

[0017] In a preferred embodiment of the present invention, the folded structure is a hilly structure with small contractions or a ridge structure with large contractions.

[0018] Therefore, those skilled in the art should understand that in this invention, the initial state of the wrinkled structure of the shell graphene oxide can be either a hill-like low-wrinkle structure or a ridge-like high-wrinkle structure. Low-wrinkle structures exhibit greater shrinkage during polar solvent removal compared to high-wrinkle structures; however, in this invention, both low-wrinkle and high-wrinkle structures can achieve a solvent-stimulated response.

[0019] As is common knowledge in this field, the wrinkles in graphene oxide refer to the bending or folding of its two-dimensional sheets caused by factors such as uneven distribution of oxygen-containing functional groups on the surface, stress shrinkage during drying, or interlayer interactions. Smaller wrinkles and a flatter structure are called hill-like low wrinkles; conversely, larger wrinkles and obvious three-dimensional bending or folding in the structure are called ridge-like high wrinkles.

[0020] In this invention, the graphene oxide spheres are in a swollen state with a porous network structure. After drying, the spheres fuse together to form a membrane, transforming from "spheres" into "spherical microcells." Multiple graphene oxide spheres swollen in a polar solvent are stacked together in a circular or other shaped mold, and after drying, form a dense membrane. The membrane's outline is determined by the shape of the mold. This membrane, immersed in a polar solvent, can reversibly swell and disassemble into multiple swollen spheres. These spheres can then be reassembled and dried as needed to form a membrane. The membrane's outline can be customized according to the mold. This assembly-disassembly process allows for membrane customization and on-demand sphere disassembly and recycling.

[0021] After the shell collapses, the graphene oxide spheres in this invention become spherical microcells. The diameter of the spherical microcells is 467 μm to 1052 μm. The diameter of the spherical microcells depends on the diameter of the graphene oxide spheres before assembly. The size of the spheres prepared by wet spinning is determined by the size of a droplet. The diameter of a droplet will not be too small, nor will it be infinitely large. If the diameter of the spherical microcells is too large, approaching the width of a conventional membrane, it becomes difficult to adjust the mechanical properties of the spherical fused membrane.

[0022] The graphene oxide spherical fusion film can form circular or complex animal-shaped topological films or beaded structures. The spherical fusion film has a dense cross-section with a density ≥1.5 g / cm³. 3 It has a tensile strength ≥40 MPa, an adjustable elongation at break within the range of 1.5% to 4%, and a reconfigurability of ≥1. It is used in green recyclable membranes, deformable smart membranes, and information encryption and reading membrane devices.

[0023] This invention also provides a method for preparing the graphene oxide spherical molten film, the method comprising the following steps: dripping a graphene oxide dispersion into a non-ionic coagulation bath via a needle to form graphene oxide gel spheres; drying the graphene oxide gel spheres to form dried gel spheres; soaking the dried gel spheres in a polar solvent to swell them and obtain graphene oxide spheres; placing a plurality of the graphene oxide spheres into a mold with a customized pattern and drying them to obtain a spherical molten film. The spherical molten film can be disassembled into the initial plurality of graphene oxide spheres by immersion in a polar solvent.

[0024] The diameter of the graphene oxide spheres ranges from 1086 μm to 2446 μm.

[0025] The height of the needle from the surface of the coagulation bath is 1 mm to 10 mm. Different needle diameters can be selected to match a suitable needle height, ensuring that the graphene oxide gel has a regular spherical shape.

[0026] The mold is a 3D-printed polymer and metal mold or a cast metal mold. Patterns include any complex shapes such as beaded, house, submarine, tree, and animal shapes. The graphene oxide spheres are tightly packed within the mold, ensuring a precise topological structure for the fused film.

[0027] Furthermore, the polar solvent includes one or more of water, ethanol, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, ethylene glycol, isopropanol, methanol, acetic acid, trifluoroacetic acid, acetonitrile, acetone, and dichloromethane. After gel drying and swelling, its morphology and structural stability are further improved, enabling the aggregates to exhibit reversible large shrinkage-swelling capacity during solvent desorption and adsorption cycles. When the polar solvent is water, after solvent replacement, freeze-drying can be performed to obtain solvent-free graphene oxide spheres that maintain the gel morphology.

[0028] In this invention, a coagulation bath system without metal ions is used to coagulate graphene oxide dispersion droplets to prepare graphene oxide aggregates. This method preserves the complex fluid shape while preventing the introduction of additional chemical interactions between the layers, thus avoiding the loss of interlayer ionic cross-linking and reversible large-volume change capability caused by metal ion coagulation bath preparation. The stability of the complex shape of the aggregates is achieved through near-room temperature drying and solvent swelling.

[0029] Generally, the concentration of the graphene oxide dispersion is 1–10 mg / g, and the dispersion solvent is a polar organic solvent, including one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), and ethylene glycol. The non-ionic coagulation bath refers to a coagulation bath free of metal ions, including one or more of ethyl acetate, ethanol, isopropanol, methanol, dichloromethane, and acetone. The coagulation time is ≥1 min. The non-ionic coagulation bath, free of metal ions, allows the graphene oxide fluid to solidify and maintain a specific shape without introducing additional chemical reactions, ensuring that the solidified aggregates maintain reversible large shrinkage-expansion capacity during solvent desorption-adsorption.

[0030] The number of graphene oxide spheres is ≥10.

[0031] Furthermore, different numbers of graphene oxide spheres can be selected to adjust the thickness of the spherical molten film, with the thickness of the spherical molten film being ≥1 μm.

[0032] Furthermore, the solvent soaking time is ≥10 min to ensure the reversibility of the membrane disassembly process, so that the original spherical units can be completely restored, recycled, and reassembled, thereby improving the reconfigurability of the membrane.

[0033] Furthermore, the number of disassembly-assembly cycles is ≥1.

[0034] Compared with the prior art, the present invention has the following advantages: 1) The reconfigurable graphene oxide sphere molten film of the present invention adopts an organic solvent system to prepare graphene oxide spheres of different diameters as building blocks of macroscopic films, which improves the controllability of the arrangement of building blocks and is conducive to the preparation of graphene oxide films with more refined and diverse structures.

[0035] 2) Utilizing the reversible shrinkage-expansion properties of graphene oxide spheres, a macroscopic membrane with a fine structure was assembled from multiple spheres, enabling reversible disassembly of the macroscopic membrane and the green recycling of the sphere units. Room temperature drying allows multiple spheres to adaptively shrink and assemble into a membrane with a specific structure. Solvent treatment restores the curvature of the sphere units within the membrane, creating mechanical repulsion at the assembly interface. This results in the reversible disassembly of the fused sphere membrane into sphere units of the original number, shape, and size, achieving the recycling of the sphere units.

[0036] 3) Through repeated drying-solvent treatment, disassembly-assembly can be repeated multiple times, and the number of times the membrane can be reconfigured is ≥1, realizing the mutual transformation of complex membrane structures and facilitating intelligent applications.

[0037] 4) The prepared spherical fusion membrane is composed of spherical microcells formed by the collapse of graphene oxide spheres. By changing the diameter of the spherical unit, the density of the edge wrinkles of the microcells in the spherical fusion membrane can be controlled, making the intrinsic elongation at break of the membrane adjustable within the range of 1.5% to 4%. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the spherical fusion film preparation method. Figure 1 a is a schematic diagram of the preparation and disassembly process of the precision topological spherical fusion film; Figure 1 b is a schematic diagram of the cross-sectional structure of graphene oxide spheres and fused sphere film.

[0039] Figure 2 Photographs and microstructures of the spherical fusion film prepared in Example 1. Figure 2 a shows the preparation process and macroscopic photograph of the house-shaped topological spherical fusion film; Figure 2 b is a polarized microscope image of the spherical fusion film surface and its magnified image; Figure 2 c shows the SEM image and its magnified view of the spherical fusion film surface; Figure 2 d is a SEM image and its magnified view of the cross-section of the spherical fusion film.

[0040] Figure 3 This describes the reconstruction process of the spherical fusion film prepared in Example 1.

[0041] Figure 4 The elongation at break of the spherical fusion film prepared in Example 1 varies with the cell diameter. Detailed Implementation

[0042] The following examples are provided to further illustrate the present invention and are intended to explain the invention, not to limit its scope. Unless otherwise specified, all figures are expressed in parts by weight and weight percentages.

[0043] Unless otherwise specified, the raw materials used in this invention are all conventional commercially available products; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0044] The embodiments of the present invention will be further described below with reference to several examples.

[0045] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0046] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0047] The reconstruction described in this invention refers to the rebuilding process. In this invention, the smaller the diameter of the spherical microcells, the higher the elongation at break of the spherical fusion membrane.

[0048] See Figures 1-4 The preparation of graphene oxide sphere fused film in this invention includes the following steps: (1) The organic solvent dispersion of graphene oxide is dripped into a non-ionic coagulation bath through a needle with an inner diameter of 60 μm to 1500 μm and coagulated for a certain time to obtain a batch of graphene oxide gel spheres. (2) After the above gel spheres were vacuum dried at room temperature of 25 °C and pressure of 0.1 kPa, they were soaked in solvent to make them swell and stabilize, thus obtaining graphene oxide spheres; (3) Select a mold with a specific complex pattern and place it on a sand core funnel lined with a filter membrane. Take a certain number of graphene oxide balls and pour them into the mold (the balls can be stacked naturally without special control of the gaps). Ensure that the balls are evenly distributed on the bottom of the mold. Dry at room temperature of 25 ℃ to obtain a reconfigurable graphene oxide ball molten film. (4) Immerse the spherical molten film in a solvent for ≥0.5 h to disassemble the film into graphene oxide spheres of the original shape and size. Pour the spheres back into molds with other patterns and dry them to complete the reconstruction of the spherical molten film structure.

[0049] (5) The above disassembly-assembly process can be repeated up to 19 times or more.

[0050] The disassembly process takes ≥0.5 hours, and the assembly and drying process takes ≥12 hours. Once disassembled or assembled, it can be stored for a long time and can be reassembled or disassembled again when needed.

[0051] Example 1: 1. Prepare a 3 mg / g graphene oxide DMF dispersion. Extrude the dispersion dropwise through a needle at a rate of 0.29 mL / min into an ethyl acetate rotary coagulation bath. The needle inner diameter was 210 μm, the needle height above the coagulation bath surface was 4 mm, and the rotation speed of the coagulation bath was 10 rpm. After coagulation for 30 min, the dispersion solidified to obtain graphene oxide gel spheres. 2. The gel spheres were filtered out and placed in a vacuum oven to dry under vacuum at room temperature for 12 hours to ensure that the solvent in the gel spheres was completely dried. Then, the dried particles were immersed in water for 30 minutes to allow them to fully absorb water and swell, resulting in graphene oxide spheres with a diameter of 1.5 mm. 3. Select a 3D-printed house-shaped resin mold and place it on a sand core funnel lined with a water-based mixed cellulose filter membrane with a pore size of 5 μm. Pour 190 prepared graphene oxide spheres into the house-shaped mold and dry them at room temperature for 2 days using vacuum filtration. During the drying process, the close packing between the sphere units precisely constructs the house shape while uniformly dispersing the stress within the membrane, making it less prone to cracking and damage during drying, resulting in a reconfigurable, precise house-shaped topological graphene oxide sphere molten film. Figure 2 As shown, the house-shaped topological spherical fusion film has a length of 1.4 cm, a width of 1.5 cm, accurately exhibiting a house-shaped topology, a thickness of 32 μm, and a cross-section showing a dense stacked sheet structure with a density of 1.5 g / cm³. 3 The membrane is composed of spherical microcells formed by the collapse of spheres. Each microcell has a diameter of 617 μm, and the edges of the microcells form protruding folds, which together constitute a periodic fold structure on the membrane surface. The tensile strength of the spherical fusion membrane is 46 MPa, and the elongation at break is 2.8%.

[0052] 4. Immerse the house-shaped topological graphene oxide spherical molten film obtained in step 3 in water for 2 hours. The film gradually disassembles into multiple graphene oxide spheres with a diameter of 1.5 mm. Pour the spheres back into a tiger-shaped mold, filter and dry for 2 days to obtain a tiger-shaped topological graphene oxide spherical molten film, completing the first reconstruction of the spherical molten film structure. Figure 3 As shown, the tiger-shaped topological spherical fusion membrane has a length of 1.5 cm, a width of 1.4 cm, and a microcell diameter of 617 μm.

[0053] 5. The above disassembly-assembly process is repeated three more times to obtain dragon-shaped, snake-shaped, and sheep-shaped topological fusion membranes, respectively. The dragon-shaped topological fusion membrane has a length of 1.7 cm, a width of 1.4 cm, and a microcell diameter of 617 μm. The snake-shaped topological fusion membrane has a length of 1.6 cm, a width of 2.5 cm, and a microcell diameter of 617 μm. The sheep-shaped topological fusion membrane has a length of 1.3 cm, a width of 1.7 cm, and a microcell diameter of 617 μm.

[0054] 6. The needle inner diameter in step 1 was changed to 60 μm, 420 μm, 840 μm, and 1500 μm, while steps 2 and 3 remained unchanged, resulting in house-shaped topological graphene oxide spherical films with different microcell diameters of 467 μm, 717 μm, 1038 μm, and 1052 μm. The wrinkle density and elongation at break of the spherical film surface increased with decreasing microcell diameter, with the elongation at break increasing from 1.5% to 4%. Figure 4 As shown; the density of the spherical fusion film was maintained at 1.5 g / cm³. 3 .

[0055] Comparative Example 1 This comparative example is the same as Example 1, except that the graphene oxide spheres are replaced with a single-layer graphene oxide dispersion to prepare the film.

[0056] 1. A 3 mg / g aqueous dispersion of graphene oxide was prepared and poured into a house-shaped mold. The mixture was then filtered and dried at room temperature for 2 days. During the drying process, the stress on the sheets near and away from the mold contour differed significantly. The uneven distribution of internal stress due to sheet shrinkage led to severe cracking of the film, resulting in an irregularly shaped, cracked graphene oxide film that could not maintain a precise house-shaped topology. The film had a length of 1.3 cm, a width of 1.2 cm, a thickness of 30 μm, and a density of 1.5 g / cm³. 3 The membrane is composed of stacked monolayers of graphene oxide sheets along its thickness direction, with irregular wrinkles on the surface. The membrane has a tensile strength of 42 MPa and an elongation at break of 1.9%.

[0057] 2. The irregularly shaped, cracked graphene oxide membrane obtained in step 1 was immersed in water for 2 hours. The membrane did not completely disintegrate into a uniform monolayer graphene oxide dispersion; instead, it formed membrane fragments of varying sizes, with only a small amount of graphene oxide sheets dissolving in the water. This fragmented dispersion was poured into a tiger-shaped mold and filtered and dried for 2 days, resulting in an even more irregularly shaped, non-uniform graphene oxide membrane. This membrane was difficult to peel off completely from the filter membrane; only thicker fragments could be removed, making membrane structure reconstruction impossible. The fragmented membrane was approximately 1 cm long and 0.5 cm wide.

[0058] Comparative Example 2 This comparative example is the same as Example 1, except that graphene oxide gel spheres are prepared by dropping an aqueous dispersion of graphene oxide into a rotating coagulation bath containing magnesium chloride aqueous solution.

[0059] 1. Prepare an aqueous dispersion of graphene oxide with a concentration of 3 mg / g. Extrude the dispersion dropwise through a needle at a rate of 0.29 mL / min and add it to an 8 wt.% magnesium chloride aqueous solution in a rotating coagulation bath to solidify for 30 min to obtain graphene oxide gel spheres. 2. The gel spheres were filtered out, washed with water, and then vacuum dried at room temperature for 12 h to ensure the solvent in the gel spheres was completely dried. Subsequently, the dried irregularly shaped particles were immersed in water for 30 min. The diameter of the particles only increased by 16%, and they could not fully expand to return to a regular spherical shape, resulting in irregular graphene oxide particles with a diameter of 472 μm.

[0060] 3. The prepared irregular graphene oxide particles were poured into a house-shaped mold and dried by vacuum filtration at room temperature for 2 days. Due to the particle volume shrinkage of only 36% during drying, they could not fuse together through adaptive shrinkage; the particles only weakly overlapped, making them prone to falling off during membrane removal. This resulted in an irregularly shaped densely packed particle mass, failing to produce a complete self-supporting membrane. The particle mass had a length of 0.9 cm, a width of 0.8 cm, and a density of 1 g / cm³. 3 Its tensile strength is only 900 kPa and its elongation at break is 0.5%.

[0061] 4. The graphene oxide particle pack obtained in step 3 was immersed in water for 2 hours. Only a small number of particles fell off the membrane, and most remained stuck together, unable to spontaneously disintegrate completely. The particle and pack dispersion were poured back into a tiger-shaped mold, filtered, and dried for 2 days to obtain an irregularly shaped, non-uniform graphene oxide pack. This pack was more non-uniform in structure than the pack obtained in step 3, with a length of 0.7 cm, a width of 0.6 cm, and a density of 1 g / cm³. 3 The tensile strength is only 840 kPa, and the elongation at break is 0.4%. Therefore, membrane fabrication and membrane structure reconstruction cannot be achieved.

[0062] Example 2: 1. Prepare a 5 mg / g graphene oxide NMP phase dispersion. Extrude the dispersion dropwise through a needle at a rate of 0.8 mL / min into an acetone rotating coagulation bath. The needle inner diameter is 1100 μm, the needle height above the coagulation bath surface is 6 mm, and the rotation speed of the coagulation bath is 20 rpm. After coagulation in the coagulation bath, the dispersion solidifies for 1 h to obtain graphene oxide gel spheres. 2. The gel spheres were filtered out and placed in a vacuum oven to dry under vacuum at room temperature for 24 h. Then the dried particles were immersed in DMAc for 1 h to allow them to fully expand, resulting in graphene oxide spheres with a diameter of 2.4 mm. 3. Select a 3D-printed linear polylactic acid (PLA) mold and place it on a sand core funnel lined with an organic nylon filter membrane with a pore size of 1.2 μm. Pour 11 prepared graphene oxide spheres into the linear mold, forming a single layer of spheres within the mold. Dry the mixture at room temperature for one day using vacuum filtration to obtain a reconfigurable, precise linear beaded topological graphene oxide sphere fused film. The film has a length of 1.1 cm, a width of 0.1 cm, precisely exhibits a beaded topology, a thickness of 6 μm, and a density of 1.5 g / cm³. 3 The microcell diameter is 1043 μm. The tensile strength of the spherical fusion film is 48 MPa, and the elongation at break is 1.6%.

[0063] 4. The beaded graphene oxide spherical molten film obtained in step 3 was immersed in DMAc for 1.5 h, and the film gradually disintegrated into 11 graphene oxide spheres with a diameter of 2.4 mm. The spheres were poured back into a V-shaped mold, forming a single layer of spheres inside the mold. After filtration and drying for 1 day, a V-shaped beaded graphene oxide spherical molten film was obtained, completing the first reconstruction of the spherical molten film structure. The film has a length of 0.5 cm, a width of 0.6 cm, and a cell diameter of 1043 μm.

[0064] 5. The above disassembly-assembly process is repeated twice more to obtain annular beaded topological fusion membranes and wavy beaded topological fusion membranes, respectively. The annular beaded topological fusion membrane has an outer diameter of 0.4 cm, an inner diameter of 0.3 cm, a microcell diameter of 1043 μm, and a breakage elongation of 1.6%. The wavy beaded topological fusion membrane has a length of 1 cm, a width of 0.3 cm, a microcell diameter of 1043 μm, and a breakage elongation of 1.6%.

[0065] Example 3: 1. Prepare a 4 mg / g graphene oxide DMSO dispersion. Extrude the dispersion dropwise through a needle at a rate of 0.35 mL / min into a rotating coagulation bath containing a 9:1 volume ratio of isopropanol and ethanol. The needle inner diameter is 420 μm, the needle height above the coagulation bath surface is 5 mm, and the rotation speed of the coagulation bath is 15 rpm. After coagulation, the dispersion solidifies for 40 min to obtain graphene oxide gel spheres. 2. The gel spheres were filtered out and placed in a vacuum oven to dry at room temperature for 18 h. Then, the dried particles were immersed in a mixed solution of NMP and ethylene glycol with a volume ratio of 1:9 for 1 h to allow them to fully expand, resulting in graphene oxide spheres with a diameter of 1.6 mm. 3. Select a 3D-printed tree-shaped polylactic acid mold and place it on a sand core funnel lined with an organic nylon filter membrane with a pore size of 0.8 μm. Pour 150 prepared graphene oxide spheres into the tree-shaped mold and dry them at room temperature for 2 days to obtain a reconfigurable precision tree-shaped topological graphene oxide sphere fused membrane. The membrane has a length of 1 cm, a width of 1.2 cm, a thickness of 28 μm, and a density of 1.5 g / cm³. 3 The microcell diameter is 715 μm, the tensile strength is 45 MPa, and the elongation at break is 1.7%.

[0066] 4. The tree-shaped topological graphene oxide spherical fused membrane obtained in step 3 was immersed in a mixed solution of NMP and ethylene glycol at a volume ratio of 1:9 for 2 h. The membrane gradually disintegrated into multiple graphene oxide spheres with a diameter of 1.6 mm. The spheres were poured back into a dog-shaped mold, filtered, and dried for 2 days to obtain a dog-shaped topological graphene oxide spherical fused membrane, completing the first reconstruction of the spherical fused membrane structure. The membrane had a length of 1.4 cm, a width of 1.6 cm, a cell diameter of 715 μm, and a breaking elongation of 1.7%.

[0067] 5. The above disassembly-assembly process was repeated 19 times to obtain mouse-shaped, cow-shaped, rabbit-shaped, horse-shaped, monkey-shaped, chicken-shaped, pig-shaped, dragonfly-shaped, snail-shaped, submarine-shaped, Great Wall-shaped, Eiffel Tower-shaped, Statue of Liberty-shaped, windmill-shaped, rocket-shaped, "B"-shaped, "ZJU"-shaped, "five"-shaped, and "moon"-shaped topological fusion membranes. The membrane cell diameter was 715 μm, and the intrinsic elongation at break was 1.7%.

[0068] The above embodiments describe in detail the structure, features, and effects of the present invention. The above description is only a preferred embodiment of the present invention. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, shall still fall within the scope of protection of the present invention if they do not exceed the scope covered by the specification.

[0069] Although embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the scope of the invention is not limited to the contents disclosed in the embodiments.

Claims

1. A reconfigurable graphene oxide spherical molten film, characterized in that, The graphene oxide spheres are assembled by fusing and interlocking after shrinking in volume. The method is as follows: graphene oxide dispersion is dripped into a non-ionic coagulation bath through a needle to form graphene oxide gel spheres; the graphene oxide gel spheres are dried to form dried gel spheres; the dried gel spheres are soaked in a polar solvent to swell and obtain graphene oxide spheres; several graphene oxide spheres are placed in a mold with a customized pattern and dried to obtain a spherical molten film; the spherical molten film is disassembled into the initial several graphene oxide spheres by soaking in a polar solvent. The graphene oxide spheres include a core and a shell. The shell encloses the core. The core is a network structure formed by overlapping graphene oxide sheets. The shell is formed by overlapping graphene oxide sheets, which have a wrinkled structure. After several shells come into contact with each other and collapse, the network structure becomes dense, forming a spherical molten film. The spherical molten film is disassembled in a polar solvent into several initial graphene oxide spheres. The diameter of the graphene oxide spheres is 1086 μm to 2446 μm.

2. The graphene oxide spherical molten film according to claim 1, characterized in that, The network structure is a porous network structure.

3. The graphene oxide spherical molten film according to claim 2, characterized in that, The porous network structure contains a polar solvent.

4. The graphene oxide spherical molten film according to claim 3, characterized in that, The folded structure is either a hilly structure with small contractions or a ridge structure with large contractions.

5. The graphene oxide spherical molten film according to claim 4, characterized in that, After the shell collapses, the graphene oxide spheres become spherical microcells.

6. The graphene oxide spherical molten film according to claim 5, characterized in that, The diameter of the spherical microcells ranges from 467 μm to 1052 μm.

7. The graphene oxide spherical molten film according to claim 6, characterized in that, The graphene oxide spherical fusion film forms a circular or complex animal-shaped topological film or a beaded structure film; the cross-section of the spherical fusion film is a dense stack of sheets, and the density of the spherical fusion film is 1.5 g / cm³. 3 Tensile strength ≥ 40 MPa.

8. The graphene oxide spherical molten film according to claim 7, characterized in that, The graphene oxide spherical fusion membrane is applied to green recyclable membranes, deformable smart membranes, and information encryption and reading membrane devices.

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