A pneumatic metamaterial, its preparation method and application

Abstract

This invention discloses an aerodynamic metamaterial, its preparation method, and its applications. The aerodynamic metamaterial comprises a matrix and a photosensitive gel material; the matrix is ​​a thermosetting polymer; the photosensitive gel material is a wet gel, asymmetrically dispersed in the matrix in the form of fibrous strips. Under heating conditions, the solvent inside the gel material vaporizes and evaporates from the matrix, generating numerous microcracks in situ within the microstructure, becoming permanent physical cavities or structural defects. This drives the overall structure to undergo pre-programmed macroscopic autonomous deformation towards the side with the smaller expansion rate. Subsequently, by lowering the ambient temperature below the glass transition temperature of the polymer matrix, the matrix transforms from a highly elastic state to a rigid glassy state, thereby locking the three-dimensional configuration and endowing the aerodynamic metamaterial with excellent mechanical strength and engineering load-bearing capacity.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing technology, and in particular relates to a pneumatic metamaterial, its preparation method and application. Background Technology

[0002] 4D printing refers to the use of 3D printing technology to create three-dimensional objects that can change their physical properties (including shape, color, elasticity, conductivity, optical properties, and electromagnetic properties) under predetermined stimuli (such as immersion in water, or exposure to electricity or light). The fourth dimension of 4D printing is time. Based on its unique deformation mechanism, 4D-printed structures can undergo reversible or irreversible shape changes in response to external stimuli. This characteristic overcomes the limitations of static structures in traditional 3D printing, endowing materials with adaptive and programmable intelligent properties. The deformation mechanism of 4D printing mainly relies on the intrinsic properties of the material and stress design during the printing process, and can be divided into three main types: 4D printing based on gel-like materials, 4D printing based on polymer shape memory effects, and deformation driven by internal stress generated during the printing process.

[0003] Gel-based materials play a crucial role in 4D printing technology due to their significant responsiveness to external environmental stimuli such as moisture, solvent concentration, and pH value. Their deformation mechanism primarily relies on the macroscopic volume expansion or contraction within the gel network. Typically, under specific environmental conditions, these materials undergo solvent absorption or desizing processes through permeation and diffusion; or, a temperature field induces a change in the hydrophilic / hydrophobic properties of the material's molecular chains, resulting in drastic volume changes. When this volume change is constrained by geometry or local material layers, driving internal stresses are generated within the component, triggering macroscopic three-dimensional shape evolution. However, solvent absorption and desizing processes based on solution diffusion mechanisms usually involve long time periods, leading to a relatively slow structural response rate. Furthermore, maintaining a specific post-deformation shape requires a strict dynamic balance of solvent content within the component, which is extremely difficult to achieve in real-world open environments. Therefore, these solvent-driven 4D printed components lack long-term stability in shape maintenance, and the overall mechanical load-bearing capacity is significantly limited after the material swells and softens. For example, researchers often utilize the principle of anisotropic expansion to 4D print composites of hydrogels and rigid polymers, creating biomimetic smart structures (such as biomimetic petals or environmentally responsive smart valves). When this component is placed in a water environment, the difference in water absorption and expansion rates in different internal regions will spontaneously produce a preset bending or folding motion. However, the complete completion of this deformation process requires sufficient diffusion of water molecules within the polymer network, and once removed from the specific humid environment, its predetermined geometric shape is difficult to solidify and maintain for a long period.

[0004] In contrast, shape memory polymers (SMPs), as another mainstream type of 4D printing smart material, can precisely recover from a temporarily set shape to its initial permanent shape by being stimulated by external physical fields (such as heat and light). Their core shaping principle relies on thermomechanical programming cycles. With this unique shape memory effect, SMPs have shown great potential in deformable structures and smart devices. In recent years, research on 4D printing-based SMPs has deepened significantly. They not only possess advantages such as low material cost and wide adaptability to molding processes, but also, due to their ability to output extremely large recoverable strain and multifunctional fusion characteristics, have become a research hotspot in the field of smart molding.

[0005] In summary, the shape deformation process of some 4D printed structures currently requires additional mechanical intervention, or suffers from instability in spontaneous deformation. Therefore, developing new deformation mechanisms for 4D printing is crucial. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a gas-driven deformation-based aerodynamic metamaterial, its preparation method, and its applications. This invention disperses a gel within a polymer matrix. Utilizing the expansion pressure generated by the gel components during solvent evaporation and gas volatilization under heating conditions, cracks are induced within the matrix, releasing significant internal stress and driving the material structure to undergo pre-programmed autonomous deformation. As the temperature decreases, the polymer matrix transforms from a rubbery state to a glassy state, firmly locking the complex gas-driven configuration and endowing the final structure with excellent mechanical strength and engineering load-bearing capacity, thus expanding the application depth of 4D printing technology in engineering fields such as adaptive structures.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: On one hand, the present invention provides a pneumatic metamaterial, the pneumatic metamaterial comprising a matrix and a photosensitive gel material; the matrix is ​​a thermosetting polymer; the photosensitive gel material is a wet gel, asymmetrically dispersed in the matrix in the form of fibrous strips.

[0008] In a preferred embodiment, the thermosetting polymer is a photosensitive resin, and the photosensitive resin is an acrylate resin.

[0009] In some specific embodiments, the photosensitive resin may include photosensitive resins such as VeroClear and VeroBlack.

[0010] In the technical solution of this invention, there are no particular limitations on the type of photosensitive gel material; any photosensitive gel material commonly used in photopolymerization printing can be used. In some specific embodiments, the photosensitive resin gel Support705B can be used.

[0011] In some specific embodiments, the photosensitive gel material is dispersed in parallel fibrous strips on one side of the matrix.

[0012] In some specific embodiments, the diameter of the fiber strip is 0.2 to 0.4 mm.

[0013] In another aspect, the present invention provides a method for preparing the above-mentioned aerodynamic metamaterial, comprising the following steps: The aerodynamic metamaterial is obtained by photopolymerization printing of the raw materials for preparing the matrix and the raw materials for preparing the photosensitive gel material according to a preset structure.

[0014] On the other hand, the present invention provides the application of the above-mentioned aerodynamic metamaterials or the above-mentioned preparation methods in 4D printing.

[0015] The above technical solution has the following advantages or beneficial effects: In the technical solution of this invention, the thermosetting polymer serves as the continuous phase matrix of the aerodynamic metamaterial; the photosensitive gel material is asymmetrically dispersed in the matrix in the form of fibrous strips, thereby constructing a component-asymmetric aerodynamic metamaterial. Under heating conditions, the solvent inside the gel material vaporizes and violently evaporates from the matrix. During this process, a large number of microcracks are generated in situ within the microstructure of the gel material. These cracks themselves remain inside the matrix as permanent physical cavities or structural defects. The formation and opening of these irreversible microcracks cause significant volume expansion and axial elongation in the distribution area of ​​the gel material, thereby generating bending moments by utilizing the huge strain mismatch between different regions, driving the overall structure to undergo pre-programmed macroscopic autonomous deformation towards the side with a smaller expansion rate. Subsequently, by lowering the ambient temperature below the glass transition temperature of the polymer matrix, the matrix transforms from a highly elastic state to a rigid glassy state, thereby locking the three-dimensional configuration and endowing the aerodynamic metamaterial with excellent mechanical strength and engineering load-bearing capacity. Attached Figure Description

[0016] Figure 1 This is a front view of the pre-designed structure of the aerodynamic metamaterial in Example 1.

[0017] Figure 2 This is a cross-sectional perspective view of the aerodynamic metamaterial pre-designed structure in Example 1.

[0018] Figure 3 This is a scanning electron microscope image of the wet gel in Example 1 before heating.

[0019] Figure 4 This is a scanning electron microscope image of the wet gel in Example 1 after heating.

[0020] Figure 5 This is a thermogravimetric diagram of the wet gel in Example 1.

[0021] Figure 6 This is a thermomechanical analysis diagram of the matrix resin of the aerodynamic metamaterial in Example 1.

[0022] Figure 7 This is a graph showing the change in curvature of the aerodynamic metamaterial in Example 1 during the thermal cycling process.

[0023] Figure 8 This is a diagram of the deformed structure of the aerodynamic metamaterial after heating in Application Example 1.

[0024] Figure 9 This is a diagram showing the deformed structure of the aerodynamic metamaterial after heating, as well as its load-bearing application, in Application Example 2. Detailed Implementation

[0025] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0026] In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The methods described in the following embodiments are conventional methods in the art, unless otherwise specified.

[0027] Example 1: This embodiment follows Figure 1-2 The pre-defined structure was used to print aerodynamic metamaterials via photoresponse printing, as detailed below: Figure 1-2 In this structure, the matrix is ​​a thermosetting polymer (photosensitive resin VeroClear, purchased from Wuhan Xingjie 3D Co., Ltd.), with overall dimensions of 60 mm × 5 mm × 0.8 mm. The photosensitive gel material is a wet-gel photosensitive resin Support705B (purchased from Wuhan Xingjie 3D Co., Ltd.), which is dispersed in parallel fiber strips on one side of the matrix. The diameter of each fiber strip is 0.3 mm, and its length is 58 mm. The surface formed by the fiber strips of photosensitive gel material is parallel to the matrix surface, and the distance between the fiber strips and the parallel surface is 0.2 mm.

[0028] The preparation method of the aerodynamic metamaterial in this embodiment is as follows: according to Figure 1-2 The pre-defined structure in the image is used to obtain aerodynamic metamaterials through photopolymerization printing.

[0029] Figure 3-4The images show scanning electron microscope (SEM) images of the aerodynamic metamaterial before and after heating at 120°C. Before heating, the material surface is relatively flat and dense. After heating, the aerodynamic metamaterial overflows with gas, forming many irreversible micropores, which change the material structure and provide driving force for subsequent deformation.

[0030] Figure 5 The graph shows the thermogravimetric curve of the aerodynamic metamaterial, obtained from a thermogravimetric analyzer. The measurement temperature range was 25–600 °C, and the heating rate was 20 °C / min. As can be seen from the graph, the material weight gradually decreases with increasing temperature.

[0031] Figure 6 The thermomechanical diagram of the aerodynamic metamaterial matrix in this embodiment is shown. The test sample measures 20 mm × 5 mm × 0.6 mm, and its modulus and glass transition temperature (T0) are measured under programmed temperature control. g The test procedure is as follows: The temperature was increased from -30℃ to 90℃ at a heating rate of 2℃ / min, then held at 90℃ for 5 minutes, and finally decreased from 90℃ to -30℃ at a cooling rate of 2℃ / min. The peak amplitude was maintained at 0.1% of the strain, and the vibration frequency was set to 1 Hz. g The value was determined by the peak value of the tan delta curve. As shown in the figure, the polymer modulus is approximately 1000 MPa at room temperature. g The temperature is 58.5℃. The high modulus polymer matrix at room temperature provides the basis for locking the deformable structural shape.

[0032] Figure 7 The figure shows the curvature of the printed structure after undergoing a thermal cycle of 25℃-120℃-25℃-120℃-25℃-120℃. As can be seen from the figure, after the printed structure completes the deformation and cools down, the curvature decreases slightly, but it still maintains a relatively high curvature. After undergoing the thermal cycle, the curvature still has good stability.

[0033] Application Example 1 In this embodiment, a flat aerodynamic metamaterial with a hollow structure was prepared using the same method as in Example 1. The aerodynamic metamaterial was heated to 120°C for 5 minutes. It was observed that the solvent inside the gel evaporated, causing the material's structure to bend and deform. Figure 8 The three-dimensional curved structure shown.

[0034] Application Example 2 In this embodiment, a planar aerodynamic metamaterial was prepared using the same method as in Example 1. Heating the aerodynamic metamaterial at 120°C for 5 minutes revealed that the solvent inside the gel vaporized and expanded, transforming the structure into a complex arched 3D structure. The deformed shape maintained high curvature and high stiffness, exhibiting excellent load-bearing capacity. Figure 9).

[0035] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A pneumatic metamaterial, characterized in that, The aerodynamic metamaterial comprises a matrix and a photosensitive gel material; the matrix is ​​a thermosetting polymer; the photosensitive gel material is a wet gel, asymmetrically dispersed in the matrix in the form of fibrous strips.

2. The aerodynamic metamaterial according to claim 1, characterized in that, The thermosetting polymer is a photosensitive resin, and the photosensitive resin is an acrylate resin.

3. The aerodynamic metamaterial according to claim 2, characterized in that, The photosensitive resin is either VeroClear or VeroBlack.

4. The aerodynamic metamaterial according to claim 1, characterized in that, The photosensitive gel material is the photosensitive resin Support705B.

5. The aerodynamic metamaterial according to claim 1, characterized in that, The photosensitive gel material is dispersed in parallel fiber strips on one side of the matrix.

6. The aerodynamic metamaterial according to claim 1, characterized in that, The diameter of the fiber strips is 0.2~0.4 mm.

7. The method for preparing the aerodynamic metamaterial according to any one of claims 1-6, characterized in that, Includes the following steps: The aerodynamic metamaterial is obtained by photopolymerization printing of the raw materials for the matrix and the raw materials for the photosensitive gel material according to a preset structure.

8. The application of the aerodynamic metamaterial according to any one of claims 1-6 or the preparation method according to claim 7 in 4D printing.

Images