Chiral metamaterial structures with compressive-torsional coupling and swelling-torsional coupling

Abstract

This application discloses a chiral metamaterial structure with compression-torsional coupling and swelling-torsional coupling, relating to the field of mechanical metamaterials. This chiral metamaterial structure provides a novel unit cell structure design, based on an active material to form a first solid beam and an elastic material to form a second structure. The first and second structures are nested and fixed together, ultimately obtaining a chiral metamaterial structure with compression-torsional coupling and swelling-torsional coupling properties. This chiral metamaterial structure can undergo torsional deformation when subjected to pressure or absorbing environmental moisture, thus exhibiting force field and humidity sensitivity, providing a technical basis for designing novel advanced functional devices with force field and humidity sensitivity.

Description

Technical Field

[0001] This application relates to the field of mechanical metamaterials, and in particular to a chiral mechanical metamaterial structure with compression-torsional coupling and swelling-torsional coupling. Background Technology

[0002] Mechanical metamaterials possess unique mechanical properties such as negative Poisson's ratio, negative compressibility, and negative thermal expansion. Moreover, their properties can be controlled through the design of microstructures to meet different application requirements, thus showing promising application prospects in precision instruments, aerospace, and marine structures.

[0003] The structural forms of mechanical metamaterials mainly include chiral structures, layered structures, origami-like structures, and three-dimensional folded structures. Among these, chiral structures refer to the property that an object and its mirror image cannot be superimposed. Mechanical metamaterials with chiral structures are called chiral mechanical metamaterials, an important structural model for mechanical metamaterials, and have broad application prospects in mechanics, electromagnetics, optics, acoustics, and thermodynamics. In the field of mechanics, two-dimensional and three-dimensional chiral mechanical metamaterials with tensile-shear coupling, tensile-torsional coupling, tensile-bending coupling, and thermo-torsional coupling properties have been designed. These chiral mechanical metamaterials can be used to fabricate highly sensitive sensors, exciters, and wave converters that are sensitive to force and temperature fields. Based on the industrial application value of chiral mechanical metamaterials, chiral mechanical metamaterials with other properties are also urgently needed to meet the needs of different application scenarios. Summary of the Invention

[0004] To address the aforementioned problems and technical requirements, this applicant proposes a chiral metamaterial structure with both compressive-torsional coupling and swelling-torsional coupling. The technical solution of this application is as follows:

[0005] A chiral metamaterial structure with compression-torsional coupling and swelling-torsional coupling is characterized in that the unit cell structure of the chiral metamaterial structure includes a first structure and a second structure. The first structure is composed of several first solid beams and has chiral symmetry, and the second structure is composed of several second solid beams and has cubic symmetry.

[0006] The first structure and the second structure are nested and fixed together, with the first structure forming an external frame structure and the second structure forming an internal support structure.

[0007] All the first solid beams are of the same length and are made of active material, while all the second solid beams are of the same length and are made of elastic material. The chiral metamaterial structure exhibits swelling-torsional coupling characteristics when the active material of the first solid beams absorbs water and expands, and exhibits compression-torsional coupling characteristics when the chiral metamaterial structure is compressed.

[0008] The further technical solution is that the virtual outline of the first structure is a cube structure and includes two virtual side surfaces parallel to the x1-x3 plane, two virtual side surfaces parallel to the x2-x3 plane, and two virtual surfaces parallel to the x1-x2 plane;

[0009] Each virtual surface includes two first solid beams intersecting diagonally, and each virtual side includes one first solid beam arranged diagonally, and the structure of the first structure is the same at each virtual side.

[0010] The further technical solution is that the second structure includes eight second solid beams fixed together, one end of each of the eight second solid beams is connected, and the other end of each of the eight second solid beams is connected to the first solid beams at the eight vertices of the virtual outline of the first structure. Each vertex of the virtual outline of the first structure is connected by two first solid beams.

[0011] A further technical solution is that the chiral metamaterial structure undergoes torsional deformation along the x3 axis when the first solid beam absorbs water and expands, and the chiral metamaterial structure undergoes torsional deformation along the x3 axis when it is compressed along the x3 axis.

[0012] The further technical solution is that the chiral metamaterial structure includes A×B×C stacked unit cell structures, where A≥1, B≥1 and C≥1, A unit cell structures are stacked sequentially along the x1 direction, B unit cell structures are stacked sequentially along the x2 direction, and C unit cell structures are stacked sequentially along the x3 direction.

[0013] The further technical solution is that each first solid beam is made of a protective shell and an active material filled inside the protective shell, and the protective shell is made of an elastic material.

[0014] A further technical solution is that the protective shell of the first solid beam has several water-permeable holes, and the active material filled inside the protective shell is exposed relative to the protective shell.

[0015] The further technical solution is that the cross-sectional shape of any first solid beam is a square, rectangle, circle, annulus or trapezoid, and the cross-sectional shape of any second solid beam is a square, rectangle, circle, annulus or trapezoid.

[0016] A further technical solution is that the chiral metamaterial structure recovers torsional deformation when the active material of the first solid beam returns to a dry state, and the chiral metamaterial structure recovers torsional deformation after the compression is removed.

[0017] A further technical solution is that the active material used to make the first solid beam is a hydrogel active filler, and the elastic material used to make the second solid beam is a rubber elastomer.

[0018] The beneficial technical effects of this application are:

[0019] This application discloses a chiral metamaterial structure with compression-torsional coupling and swelling-torsional coupling. This chiral metamaterial structure provides a novel unit cell structure design, which can ultimately obtain a chiral metamaterial structure with compression-torsional coupling and swelling-torsional coupling properties. This chiral metamaterial structure can undergo torsional deformation when subjected to pressure or absorbing environmental moisture, thereby exhibiting force field and humidity sensitivity, providing a technical basis for designing novel advanced functional devices with force field and humidity sensitivity.

[0020] The single-cell structure of this chiral metamaterial is simple and can be easily fabricated using multi-material 3D printing. Attached Figure Description

[0021] Figure 1 This is a structural diagram of a unit cell structure in one embodiment of this application.

[0022] Figure 2 This is a structural diagram of the first structural diagram in one embodiment of this application.

[0023] Figure 3 This is a structural diagram of the second structural diagram in one embodiment of this application.

[0024] Figure 4 This is a schematic diagram of the protective shell of the first solid beam in one embodiment of this application.

[0025] Figure 5 This is a schematic diagram of a structure in one embodiment of the present application, showing multiple unit cell structures stacked sequentially along the x3 direction.

[0026] Figure 6 It is a schematic diagram of a structure in which multiple single-cell structures are stacked sequentially along the x1 and x2 directions.

[0027] Figure 7 This is a schematic diagram illustrating the swelling and torsional coupling characteristics of a chiral metamaterial structure in an example.

[0028] Figure 8 This is a schematic diagram of the swelling-torsional coupling characteristics of a chiral mechanical metamaterial structure in another example.

[0029] Figure 9 This is a schematic diagram illustrating the compressive-torsional coupling characteristics of a chiral metamaterial structure in an example. Detailed Implementation

[0030] The specific embodiments of this application will be further described below with reference to the accompanying drawings.

[0031] This application discloses a chiral metamaterial structure with compression-torsional coupling and swelling-torsional coupling. Please refer to [reference needed]. Figure 1 The diagram shows the structure of a unit cell, which includes a first structure and a second structure. The first structure is composed of several first solid beams 1 and has chiral symmetry, while the second structure is composed of several second solid beams 2 and has cubic symmetry. Figure 1 The black solid beams in the middle are all first solid beams 1, and all the first solid beams 1 constitute the first structure. Figure 1 All the white solid beams in the middle are the second solid beams 2, and all the second solid beams 2 together form the second structure.

[0032] The first and second structures are nested and fixed together, with the first structure forming the outer frame and the second structure forming the inner support structure. All the first solid beams are of the same length and are made of an active material, while all the second solid beams are of the same length and are made of an elastic material.

[0033] Based on this structure, the chiral metamaterial exhibits swelling-torsional coupling characteristics by undergoing torsional deformation when the active material of the first solid beam 1 absorbs water and expands. Furthermore, due to the chiral symmetry of the first structure, the chiral metamaterial exhibits compression-torsional coupling characteristics by undergoing torsional deformation under compression. Additionally, the chiral metamaterial recovers its torsional deformation and returns to its initial state when the active material of the first solid beam 1 returns to a dry state, and it also recovers its torsional deformation and returns to its initial state after the compression is removed.

[0034] In one embodiment, such as Figure 2 As shown, the virtual outline of the first structure is a cube and includes two virtual sides parallel to the x1-x3 plane, two virtual sides parallel to the x2-x3 plane, and two virtual surfaces parallel to the x1-x2 plane. The x1 and x2 directions are perpendicular to each other in the x1-x2 plane, the x1 and x3 directions are perpendicular to each other in the x1-x3 plane, and the x2 and x3 directions are perpendicular to each other in the x2-x3 plane. Each virtual surface includes two first solid beams 1 intersecting diagonally, and each virtual side includes one first solid beam 1 arranged diagonally. The structure of the first structure is identical at all virtual sides. That is, for example... Figure 2In this configuration, when considering each virtual side from the outside, the first solid beam 1 at each virtual side is set along a diagonal line from the upper left corner to the lower right corner. Alternatively, the first solid beam 1 at each virtual side can be set along a diagonal line from the upper right corner to the lower left corner, which also achieves the desired effect. The cross-sectional shape of any first solid beam 1 can be a square, rectangle, circle, annulus, or trapezoid, and the length of all first solid beams 1 is L. a The cross-sectional dimensions are all d. a Taking the example that all the first solid beams 1 have a circular cross-sectional shape, the cross-sectional dimension d of the first solid beam 1 is... a This means that the diameter of the first solid beam 1 is d. a .

[0035] In one embodiment, please refer to Figure 3 The second structure comprises eight fixed second solid beams 2, each connected at one end, and the other ends of each beam connected to a first solid beam 1 at one of the eight vertices of the virtual outline of the first structure. The cross-sectional shape of any one of the second solid beams 2 is square, rectangular, circular, annular, or trapezoidal, and the length of each second solid beam 2 is L. b The cross-sectional dimensions are all d. b Taking the example that all the cross-sectional shapes of the second solid beam 2 are circular, the cross-sectional dimension d of the second solid beam 2 is as follows: b This refers to the diameter of the second solid beam 2 being d. b Please combine Figure 1 The virtual outline of the first structure has two first solid beams 1 connected at the ends of each vertex, namely a first solid beam 1 at a virtual side and a first solid beam 1 at a virtual surface. The end of the second solid beam 2 is also connected to the ends of the two first solid beams 1. Thus, the first structure and the second structure are nested and fixed together.

[0036] In one embodiment, all first solid beams 1 have the same cross-sectional shape, or at least two first solid beams 1 have different cross-sectional shapes. In another embodiment, all second solid beams 2 have the same cross-sectional shape, or at least two second solid beams 2 have different cross-sectional shapes. The first solid beams 1 and second solid beams 2 may have the same or different cross-sectional shapes. However, for ease of analysis and explanation, in practical applications, it is generally configured that all first solid beams and all second solid beams have the same cross-sectional shape.

[0037] based on Figures 1-3 The chiral metamaterial structure shown in the figure undergoes torsional deformation along the x3 axis when the first solid beam absorbs water and expands, and also undergoes torsional deformation along the x3 axis when compressed along the x3 axis.

[0038] In one embodiment, the active material used to form the first solid beam 1 is a hydrogel active filler, and the elastic material used to form the second solid beam 2 is a rubber elastomer. For example, in one instance, the rubber elastomer used to form the second solid beam 2 is the elastomer TangoBlackPlus (Stratasys), and the hydrogel active filler used to form the first solid beam 1 is the hydrogel active filler Hydroge SUP705 (Stratasys). In one embodiment, in addition to using the active material to form the first solid beam 1, a protective shell 3 made of an elastic material is also provided outside the active material. Each first solid beam 1 is made of the protective shell 3 and the active material filled inside the protective shell 3, giving the first solid beam 1 better elasticity. The elastic material used to form the protective shell is generally the same as the elastic material used for the second solid beam 2. Based on this, such as Figure 4 As shown, the protective shell 3 of the first solid beam 1 has several water-permeable holes 4. The active material filled inside the protective shell 3 is exposed relative to the protective shell 3, which facilitates the active material to absorb water and drain water to restore its dry state.

[0039] Based on the unit cell structure provided in this application, the chiral metamaterial structure can also be extended in three dimensions, such that the chiral metamaterial structure includes A×B×C stacked unit cell structures, where A≥1, B≥1, and C≥1. The A unit cell structures are stacked sequentially along the x1 direction, the B unit cell structures are stacked sequentially along the x2 direction, and the C unit cell structures are stacked sequentially along the x3 direction. Figure 5 A schematic diagram shows multiple unit cell structures stacked sequentially along the x3 direction. (See diagram.) Figure 6 A schematic diagram showing multiple unit cell structures stacked sequentially along the x1 and x2 directions is shown.

[0040] In one instance, based on such Figure 1 The chiral metamaterial structure shown, consisting of a single-cell structure and two stacked single-cell structures along the x3 direction, is a 1×1×2 structure. This chiral metamaterial structure can be fabricated using photopolymerization 3D printing. Its top view along the x3 direction is shown below. Figure 7 As shown, when the fabricated chiral metamaterial structure is placed in water, the active materials of all the first solid beams 1 absorb water and expand, causing the chiral metamaterial structure to undergo torsional deformation about the x3 axis. After the chiral metamaterial structure is removed from the water and allowed to dry or evaporate on its own, allowing the active materials to return to a dry state, the torsional deformation of the chiral metamaterial structure can be recovered.

[0041] In another instance, based on such Figure 1The shown unit cell structure was used to fabricate a 2×2×1 chiral metamaterial structure with four unit cells stacked along the x1 and x2 directions. Its top view along the x3 direction is shown below. Figure 8 As shown, when the fabricated chiral metamaterial structure is placed in water, the active materials of all the first solid beams 1 absorb water and expand, causing the chiral metamaterial structure to undergo torsional deformation about the x3 axis. After the chiral metamaterial structure is removed from the water and allowed to dry or evaporate on its own, allowing the active materials to return to a dry state, the torsional deformation of the chiral metamaterial structure can be recovered.

[0042] In another instance, based on such Figure 1 The shown unit cell structure was used to fabricate a 1×1×2 chiral metamaterial structure with two unit cells stacked along the x3 direction. For compression along the x3 direction, please refer to [reference needed]. Figure 9 The chiral metamaterial structure undergoes torsional deformation about the x3 axis. When the compression in the x3 direction is removed, the torsional deformation of the chiral metamaterial structure can be recovered.

[0043] The above descriptions are merely preferred embodiments of this application, and this application is not limited to the above embodiments. It is understood that other improvements and variations that can be directly derived or conceived by those skilled in the art without departing from the spirit and concept of this application should be considered to be included within the protection scope of this application.

Claims

1. A chiral metamaterial structure with compressive and expansive torsional coupling, characterized in that, The unit cell structure of the chiral mechanical metamaterial structure comprises a first structure and a second structure, the first structure is formed by a plurality of first solid beams and has chiral symmetry, and the second structure is formed by a plurality of second solid beams and has cubic symmetry; The first structure and the second structure are fixedly nested together, and the first structure is formed as an external frame structure and the second structure is formed as an internal support structure; All the first solid beams have the same length and are made of active material, and all the second solid beams have the same length and are made of elastic material; the chiral mechanical metamaterial structure exhibits swelling torsional coupling characteristics when the active material of the first solid beams swells by water absorption, and exhibits compression torsional coupling characteristics when the chiral mechanical metamaterial structure is compressed; the virtual outer contour of the first structure is a right cuboid structure and comprises two virtual side faces parallel to the plane, two virtual side faces parallel to the plane and two virtual surfaces parallel to the plane; each virtual surface comprises two of the first solid beams arranged across a diagonal, each virtual side face comprises one of the first solid beams arranged along a diagonal, and the structure of the first structure is identical at each virtual side face; the directions and the directions are perpendicular to each other in the plane, the directions and the directions are perpendicular to each other in the plane, the directions and the directions are perpendicular to each other in the plane; The second structure comprises 8 second solid beams fixedly nested together, one ends of the 8 second solid beams are connected together, and the other ends of the 8 second solid beams are connected to the first solid beams at 8 vertices of a virtual external contour of the first structure, and two first solid beams are connected together at each vertex of the virtual external contour of the first structure.

2. The chiral-mechanics metamaterial structure of claim 1, wherein, The chiral metamaterial structure undergoes a torsional deformation along the direction axis upon water absorption expansion of the first solid beam, the chiral metamaterial structure undergoes a torsional deformation along the direction axis upon compression along the direction axis.

3. The chiral-mechanics metamaterial structure of claim 1, wherein, The chiral mechanical metamaterial structure comprises a plurality of the unit cell structures stacked with each other, and , a plurality of the unit cell structures are stacked along a direction in sequence, a plurality of the unit cell structures are stacked along a direction in sequence, a plurality of the unit cell structures are stacked along a direction in sequence.​ 4. The chiral-mechanics metamaterial structure of claim 1, wherein, Each first solid beam is made of a protective shell and active material filled in the protective shell, and the protective shell is made of elastic material.

5. The chiral-mechanics metamaterial structure of claim 4, wherein, A plurality of water-permeable holes are formed in the protective shell of the first solid beam, and the active material filled in the protective shell is exposed relative to the protective shell.

6. The chiral-mechanics metamaterial structure of claim 1, wherein, The cross-sectional shape of any first solid beam is square, rectangular, circular, annular or trapezoidal, and the cross-sectional shape of any second solid beam is square, rectangular, circular, annular or trapezoidal.

7. The chiral-mechanics metamaterial structure of claim 1, wherein, The chiral mechanical metamaterial structure restores torsional deformation when the active material of the first solid beams returns to a dry state, and the chiral mechanical metamaterial structure restores torsional deformation when the compression action is removed.

8. The chiral-mechanical metamaterial structure of claim 1, wherein, The active material used to make the first solid beams is a hydrogel active filler, and the elastic material used to make the second solid beams is a rubber elastomer.

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