Self-folding film hinge structure based on shape memory polymer and application

Abstract

The invention belongs to the technical field of self-folding structures, and particularly relates to a self-folding film hinge structure based on a shape memory polymer and application. The self-folding film hinge structure is arranged between two paper folding plates and comprises a first hinge plate, a second hinge plate and a shape memory polymer film structure, the thickness of each hinge plate is equal to that of the paper folding plate, one end, close to the paper folding plate, of each hinge plate is fixedly connected with the paper folding plate, and one end, far away from the paper folding plate, of each hinge plate is in contact with a rolling cambered surface; the shape memory polymer film structure comprises two end bonding parts and a middle deformation part, and the bonding parts are fixedly bonded with the top surface of the paper folding plate; and in the process that the shape memory polymer film structure drives the paper folding plate to be folded to a target angle, the first hinge plate and the second hinge plate rotate along the rolling cambered surface. The self-folding film hinge structure can achieve the folding driving effect of a paper folding structure under thermal stimulation, can be suitable for interference-free folding of paper folding plate structures of various thicknesses, guarantees design and accurate control of specific-angle folding, and is wide in application range.

Description

Technical Field

[0001] This invention belongs to the field of self-folding structure technology, specifically relating to a self-folding membrane hinge structure based on shape memory polymer and its application. Background Technology

[0002] Foldable structures can transform planar two-dimensional structures into complex three-dimensional structures through folding. The rich mechanical properties of three-dimensional structures are crucial in engineering applications. Foldable structures have a high fold-to-spread ratio, effectively utilizing material properties and structural strength after folding. However, as the complexity of foldable structures increases, achieving folding through external drives, such as external drive motors, becomes more difficult. Self-folding refers to the process by which an initial structure spontaneously or in response to stimuli, folding into different shapes without external driving force input. The self-folding method enables integrated structure-function design, circumventing the challenges of driving the folding of complex structures under manufacturing constraints. Self-folding structures have been widely used in robotics, multimodal structures, electronic devices, antennas, space structures, and biomedicine.

[0003] Currently, various methods exist for transforming planar structures into three-dimensional structures using self-folding technology. One common method involves structural design, combining two printing materials into a bilayer structure, utilizing the difference in their shrinkage or expansion rates under external stimuli to achieve self-folding. Stimulus-responsive materials, which change size under specific stimuli, are widely used in self-folding. Shape memory materials are a type of stimulus-responsive material, capable of recovering their original shape from a deformed state under specific external stimuli. Thermally responsive shape memory polymers have attracted significant attention in the field of self-folding due to their simple actuation mechanism and wide range of applications. Shape memory polymers are first processed into a permanent shape. When heated above their glass transition temperature, they can be deformed into a temporary shape by external force. Once the temperature drops below the glass transition temperature, the temporary shape is retained, and the external force can be removed. This process is called pre-programming the shape memory polymer. When this pre-programmed shape memory polymer is reheated, the material returns to its initial shape. This reversible deformation capability makes shape memory polymers a promising candidate for self-folding technology.

[0004] Patent application 201810132594X, titled "A Light-Driven Self-Folding Origami Structure," describes a structure controlled by light-driven folding and unfolding. Specifically, it consists of several rectangular units arranged in a series. Each rectangular unit is a thin sheet structure with two sides, symmetrical about its center line. Photosensitive patches are located on both sides of each unit. Under light, these patches bend away from the rectangular unit, causing the entire structure to bend along the center line and the boundary line between adjacent rectangular units towards the opposite side, while simultaneously bending towards the front along the diagonals on both sides. However, in engineering applications, the panel thickness of the origami structure is not negligible due to limitations in material properties and manufacturing processes. For foldable origami structures with thick panels, simply increasing the panel thickness of a zero-thickness origami structure would lead to mechanical interference between the panels. Furthermore, the aforementioned origami structure is a thin sheet, and the thickness impact of the origami structure in practical engineering applications has not been considered.

[0005] Patent application 2007100718750, entitled "Shape Memory Composite Material Hinge Driven Deployment Device," includes a shape memory composite material drive body, a first connector, and a second connector. The two connectors are fixed to both ends of the shape memory composite material drive body. Driven by different shapes of drive bodies, such as flat, double-curved, and quadruple-curved surfaces, it functions as an actuator for deployable solar panels, deployable antennas, deployable reflectors, and deployable trusses for aerospace applications under thermal deformation. The requirement is for smooth, reliable, and slow self-starting motion. However, as a self-folding panel with an origami structure, the hinge structure design is crucial when specific folding angles are required. It needs to adapt to different thicknesses of the self-folding panel and ensure no mechanical interference during the folding process. Furthermore, as a self-folding panel with an origami structure, the focus is on the process of transforming a planar structure for easy transport into a three-dimensional structure with practical use. This patent only realizes the process from a folded structure to a planar structure, failing to meet the usage requirements of a self-folding panel with an origami structure.

[0006] Therefore, in order to ensure the motion coordination and precise control of the thick-panel origami structure in practical engineering applications, the hinge of the origami structure is specially designed to meet the above requirements and broaden the application range of the self-folding membrane hinge structure, which is the focus of this invention. Summary of the Invention

[0007] This invention provides a self-folding membrane hinge structure and its application based on shape memory polymer. It can achieve the folding drive effect of origami structure under thermal stimulation, and can be used for interference-free folding of origami cardboard structures of various thicknesses. It ensures the design and precise control of folding at specific angles, has a wide range of applications, and solves the problems existing in the prior art.

[0008] This invention provides one of the following technical solutions:

[0009] A self-folding membrane hinge structure based on shape memory polymer is disclosed, which is positioned between two folded cardboard pieces intended to achieve folding. The self-folding membrane hinge structure includes a first hinge plate, a second hinge plate, and a shape memory polymer membrane structure. The thickness of the first and second hinge plates is equal to the thickness of the folded cardboard pieces. The ends of the first and second hinge plates near the folded cardboard pieces are fixedly connected to each folded cardboard piece, while the ends of the first and second hinge plates away from the folded cardboard pieces contact each other via a rolling arc surface. The shape memory polymer membrane structure includes adhesive portions at both ends and a deformable portion disposed between the adhesive portions. The adhesive portions are fixed to the top surface of the folded cardboard pieces, and the deformable portion covers the top surface of the first and second hinge plates. During the process of the shape memory polymer membrane structure driving the folded cardboard pieces to fold to a target angle, the first and second hinge plates rotate along the rolling arc surface.

[0010] Each hinge plate includes a top surface and a bottom surface arranged in parallel, and an outer arc surface located between the top surface and the bottom surface. The side of the hinge plate opposite to the outer arc surface is fixedly connected to the folding paper; the outer arc surfaces of the two hinge plates form the rolling arc surface.

[0011] On the longitudinal section of the self-folding membrane hinge structure, the first hinge plate is marked with ABCD. Assuming that the length of the bottom edge AB of the first hinge plate is L, the thickness of BC is b, and the length of the top edge CD is S, the center of the circle O' is the perpendicular of the straight line that is perpendicular to the bottom edge AB of the first hinge plate and passes through point D upwards, and the horizontal distance from the center O' to point A is a. Then the arc edge AD of the first hinge plate is 1 / 4 arc edge of an ellipse formed by O' as the center and a and b as radii.

[0012] Furthermore, the shape memory polymer film structure is provided with one or more spaced apart between adjacent folding plates; the shape memory polymer film structure is a rectangular shape memory polymer film, the length of the deformable part of the rectangular shape memory polymer film is equal to the sum of the bottom edges of the first and second hinge plates, and the adhesive parts at both ends of the rectangular shape memory polymer film are respectively set to ≥5mm in the length direction of the shape memory polymer film structure.

[0013] Furthermore, the dimension of the bonding portion of the shape memory polymer membrane structure in the length direction of the membrane structure is set to 5 mm.

[0014] Furthermore, when the first and second hinge plates are folded to the target folding angle θ by the shape memory polymer film structure, the straight lines containing the side lengths in the thickness direction of the first and second hinge plates extend and intersect to form the folding angle θ, and this intersection point is denoted by F; at this time, the tangent point of the two hinge plates on the rolling arc surface is denoted by E, and the intersection point of the straight line passing through point E and perpendicular to the line connecting EF with the bottom edge AB of the first hinge plate is denoted by O; then the length a on the bottom edge of the first hinge plate is obtained by the following algorithm:

[0015] Establish a Cartesian coordinate system with point O' on the bottom edge of the first hinge plate as the origin, and the positive x-axis along the direction BA of the bottom edge of the first hinge plate. Solve for the geometric coordinates of points E and O using analytical geometry principles:

[0016]

[0017] Given the coordinates of points E and O, calculate the lengths of line segments OE and OB, where the coordinates of point B are (x, y, y). B ,y B )=(aL,0); Substitute the target folding angle θ into the following equation and solve analytically to obtain a, thereby determining the geometric dimensions of the self-folding membrane hinge structure;

[0018]

[0019] Furthermore, the first and second hinge plates of the self-folding membrane hinge structure are integrally formed with the folding cardboard that is respectively fixed to them.

[0020] Furthermore, the cardboard is a polylactic acid panel.

[0021] Furthermore, the shape memory polymer film structure is a PLA-based shape memory polymer film.

[0022] Furthermore, the shape memory polymer membrane structure is preloaded at high temperature and then cooled and unloaded to remember the stretching deformation, which acts as an actuator to drive the self-folding membrane hinge structure.

[0023] Furthermore, the above process of "high-temperature preloading followed by cooling and unloading to memorize the stretching deformation" is a pre-programming of the shape memory polymer film; the shape memory polymer film obtained in this way acts as an actuator under thermal stimulation, providing folding driving force for the cardboard to which it is attached during the recovery deformation process.

[0024] Furthermore, the above shape memory polymer film was obtained by pre-programming a dog bone-shaped specimen, and the middle long strip of the dog bone-shaped specimen after stretching deformation was selected as the shape memory polymer film.

[0025] Furthermore, the pre-programmed dog-bone specimen was subjected to uniform stretching at 2 mm / min in a 65℃ oven. When the deformation reached twice the original length, the specimen was kept deformed and cooled to room temperature via air convection. At this point, the external load was unloaded, completing the pre-programming process. In actual use, the pre-programmed dog-bone shape is processed according to the required length of the shape memory polymer membrane structure based on the shape memory structure of the self-folding membrane hinge.

[0026] Furthermore, the bonding of the adhesive portion of the shape memory polymer film structure to the cardboard can be achieved by applying water.

[0027] The present invention provides the following second technical solution:

[0028] The above-described self-folding film hinge structure is applied in self-folding origami paperboard. The first and second hinge plates of the self-folding hinge structure are respectively fixed to the side of the connecting plate of each pair of paperboards to be folded. The shape memory polymer film structure of the self-folding hinge structure is covered on the folding side of each pair of paperboards. The adhesive portions at both ends of the shape memory polymer film structure are bonded to the top surface of the two paperboards fixed to the outside of the first and second hinge plates.

[0029] Furthermore, the self-folding cardboard is a Miura cardboard or a hexahedral cardboard.

[0030] Furthermore, the self-folding origami board is a Miura origami board, and the unit plates of the Miura origami board are provided with vertically mirrored first hinge plates or second hinge plates on opposite sides, and adjacent unit plates of the Miura origami board are assembled and connected according to the self-folding membrane hinge structure; or, the self-folding origami board is a hexahedral origami board, and the unit plates of the hexahedral origami board are provided with first hinge plates or second hinge plates on all four sides, and adjacent unit plates of the hexahedral origami board are assembled and connected according to the self-folding membrane hinge structure.

[0031] Furthermore, when the above-mentioned cardboard structure is subjected to thermal stimulation, the self-folding membrane hinge structure set between the unit boards drives the self-folding deformation.

[0032] Furthermore, the steps for making the above origami cardboard are as follows:

[0033] S1. Draw the structural plan view and determine the size of the origami cardboard and the folding direction and folding angle of each crease;

[0034] S2. Calculate the hinge size of the self-folding film corresponding to each crease based on the size of the cardboard and the required folding angle of the crease;

[0035] S3. During the process of making origami, corresponding hinge structures are reserved on the edge of the origami, which are then processed by a 3D printer to obtain an origami panel with hinge structures on all four sides.

[0036] S4. In the corresponding area of ​​the adjacent origami board, according to the hinge plate size of the self-folding film hinge, paste the pre-stretched shape memory polymer film structure of the corresponding length to obtain the final origami structure.

[0037] Furthermore, in the above manufacturing steps, the length of the bottom edge of the hinge plate of the self-folding membrane hinge structure is specified before design. The principle of specification is to avoid affecting the normal function of the folding board, and it is generally much smaller than the length of the panel body of the folding board in that direction. Under the premise that the bottom edge of the hinge plate is determined, the thickness (same as the folding board) is known, and the target folding angle is known, the length of 'a' is calculated according to the aforementioned algorithm, and the length of the top edge S of the hinge plate and the outer arc shape are determined accordingly. Thus, the geometric dimensions of the self-folding membrane hinge structure are determined.

[0038] The beneficial effects of this invention are:

[0039] 1. The self-folding membrane hinge structure of this invention is located between origami panels of a certain thickness. It adopts hinge offset technology combined with rolling contact to solve the folding interference problem between origami panels of a certain thickness. It can spontaneously realize the transformation of the origami structure from a planar state to a folded state under thermal stimulation, and reproduce the movement completely consistent with zero-thickness origami. The membrane structure in the membrane hinge structure of this invention is manufactured by using a pre-programmed shape memory polymer, which is convenient to drive, has low design complexity, can be applied to various complex origami structures, and has higher adjustability.

[0040] 2. The self-folding membrane hinge structure of this invention can eliminate bifurcation, achieve planar folding, and reduce parasitic motion. Based on achieving the self-folding function of the thick-plate origami structure, the folding angle can be precisely controlled by adjusting the specific geometric parameters of the membrane hinge structure. Attached Figure Description

[0041] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0042] Figure 1 A schematic diagram illustrating the editing (pre-programming) process for shape memory polymers;

[0043] Figure 2 Reference images of dog bone-shaped shape memory polymer specimens before and after pre-programming;

[0044] Figure 3 This is a schematic diagram of the self-folding membrane hinge structure of Embodiment 1 of the present invention;

[0045] Figure 4 for Figure 1 Schematic diagram of the connection structure between the self-folding membrane hinge structure and the cardboard.

[0046] Figure 5 This is a simplified theoretical model diagram of the self-folding membrane hinge structure of the present invention (a schematic diagram of the structural state when folded to the target folding angle θ);

[0047] Figure 6 This is a schematic diagram of the structure of Embodiment 2 of the present invention;

[0048] Figure 7 for Figure 6 A schematic diagram of the overall structure within the central platform area;

[0049] Figure 8 for Figure 7 Top view of the structure;

[0050] Figure 9 for Figure 7 Reference diagram of the folded state of the middle structure;

[0051] Figure 10 A single sheet of Miura origami paperboard with the self-folding membrane hinge structure of the present invention;

[0052] Figure 11 For inclusion Figure 10 A structural diagram of the Miura origami cardboard in the single-layer board;

[0053] Figure 12 for Figure 11 Miura Origami provides a reference diagram simulating the original and folded states of a product.

[0054] Figure 13 A single sheet of a hexahedral folding cardboard with the self-folding membrane hinge structure of the present invention;

[0055] Figure 14 For inclusion Figure 13 A schematic diagram of the structure of a six-sided origami cardboard sheet;

[0056] Figure 15 for Figure 14 Reference diagram showing the original state and folding deformation process of a six-sided origami cardboard model.

[0057] In the figure, 1 is the first hinge plate, 2 is the second hinge plate, 3 is the shape memory polymer film structure, 301 is the bonding part, 302 is the deformation part, 4 is the platform area, 401 is the groove part, 5 is the cardboard body, 6 is the hinge plate, 7 is the square cardboard body, and 8 is the cardboard. Detailed Implementation

[0058] The present invention will be further described below with reference to specific embodiments, but the scope of protection of this application is not limited to these embodiments.

[0059] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0060] In the description of this invention, the term "shape memory polymer" refers to a class of stimulus-responsive smart materials whose core characteristic is the ability to recover from a temporary deformed state to a pre-set original shape under the influence of external stimuli (such as temperature, humidity, light, chemical substances, etc.). The term "shape memory effect" refers to the property of certain materials to recover from a temporary deformed state to their original (permanent) shape under the influence of specific external stimuli (such as temperature, light, magnetic field, chemical substances, etc.). The term "pre-programming" refers to the process of pre-loading a shape memory polymer specimen at high temperature, followed by cooling and unloading to memorize the tensile deformation.

[0061] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0062] In order to achieve interference-free folding of origami structures with a certain thickness and ensure precise control of folding at a specific angle, this invention proposes a self-folding membrane hinge structure based on shape memory polymer. When this membrane hinge structure is applied to a self-folding origami board with a certain thickness, it can achieve excellent self-folding driving effect under thermal stimulation.

[0063] Example 1

[0064] A novel membrane hinge structure with self-folding function was designed by combining a pre-programmed shape memory polymer membrane structure with a cardboard structure with thickness.

[0065] See Figure 1 This diagram illustrates the pre-programming process of a shape memory polymer membrane structure. Specifically, shape memory polymer membrane pre-programming involves high-temperature pre-loading followed by cooling and unloading to memorize the stretched deformation, which then acts as an actuator to provide driving force for folding. As one implementation method, the pre-programming operation of the shape memory polymer membrane is as follows: A shape memory polymer dog-bone-shaped specimen is uniformly stretched at a speed of 2 mm / min in a 65°C chamber. When the deformation reaches twice the original length, the specimen is kept deformed and cooled down to room temperature via air convection. At this point, the external load is unloaded, completing the pre-programming step. Figure 2The image shows the state of the dog bone-shaped shape memory polymer specimen before and after pre-programming. The square dashed frame in the pre-programmed specimen below outlines the part that can be cut to be used in the fabrication of the shape memory polymer membrane structure in the self-folding membrane hinge structure of this invention.

[0066] See Figure 3 This paper demonstrates a self-folding membrane hinge structure based on shape memory polymer. Figure 4 for Figure 3 The self-folding membrane hinge structure is connected to the folding cardboard it is attached to. This self-folding membrane hinge structure is located between two foldable cardboards 8 of a certain thickness and includes a first hinge plate 1, a second hinge plate 2, and a shape memory polymer membrane structure 3. The thickness of the first and second hinge plates is equal to the thickness of the folding cardboards. The ends of the first and second hinge plates near the folding cardboards are fixedly connected to each folding cardboard, specifically integrally formed with the folding cardboards. The ends of the first and second hinge plates away from the folding cardboards contact each other with a rolling arc surface. The shape memory polymer membrane structure includes two bonding portions 301 at both ends and a deformable portion 302 located between the bonding portions. The bonding portions are fixed to the top surface of the folding cardboard, and the deformable portion covers the top surface of the first and second hinge plates. During the process of the shape memory polymer membrane structure driving the folding cardboard to fold to the target angle, the first and second hinge plates rotate along the rolling arc surface.

[0067] Each hinge plate includes a top surface and a bottom surface arranged in parallel, and an outer arc surface disposed between the top surface and the bottom surface. The side of the hinge plate opposite to the outer arc surface is vertical and fixed to the folding paper; the outer arc surfaces of the two hinge plates form the rolling arc surface.

[0068] On the longitudinal section of the self-folding membrane hinge structure, the corners of the first hinge plate are marked with ABCD. Assuming that the length of the bottom edge AB of the first hinge plate is L, the thickness of BC is b, and the length of the top edge CD is S, the orthocenter of the straight line perpendicular to the bottom edge AB of the first hinge plate and passing through point D is the center O' of the circle, and the horizontal distance from the center O' to point A is a. Then the arc edge AD of the first hinge plate is 1 / 4 arc edge of the ellipse formed by O' as the center and a and b as radii.

[0069] The shape memory polymer film structure 3 is arranged in one or more intervals along the width direction between adjacent folded cardboard sections; the shape memory polymer film structure is a rectangular shape memory polymer film, and the length of the deformable part of the rectangular shape memory polymer film is equal to the sum of the bottom sides of the first and second hinge plates. The adhesive portions at both ends of the rectangular shape memory polymer film are each set to 5mm along the length direction of the shape memory polymer film. Therefore, the total length of the rectangular shape memory polymer film is 2 × the bottom side length of the first or second hinge plate + 2 × 5mm.

[0070] See Figure 5This is a simulation diagram of the state of the above self-folding membrane hinge structure when folded to the target folding angle θ. In this state, as... Figure 5 The straight lines containing the thickness directions of the first and second hinge plates, as marked in the diagram, extend and intersect to form the folding angle θ, and this intersection point is denoted by F; at this time, the tangent point of the two hinge plates on the rolling arc surface is denoted by E, and the intersection point of the straight line passing through point E and perpendicular to the line connecting EF with the bottom edge AB of the first hinge plate is denoted by O; then the length a on the bottom edge of the first hinge plate is obtained by the following algorithm:

[0071] Establish a Cartesian coordinate system with point O' on the bottom edge of the first hinge plate as the origin and the positive x-axis along the BA direction. Solve for the geometric coordinates of points E and O using analytical geometry principles:

[0072]

[0073] Given the coordinates of points E and O, calculate the lengths of line segments OE and OB, where the coordinates of point B are (x, y, y). B ,y B )=(aL,0); Substituting the target folding angle θ into the following equation, we can obtain a analytically, thereby determining the geometric dimensions of the self-folding membrane hinge structure;

[0074]

[0075] Taking a 90° target folding angle as an example, such as Figure 5 The length of segment CC' marked in the middle is represented by d0 at the target folding angle. Substituting L = 15.5 mm, b = 10 mm, d0 = 15.5 mm, and θ = 90° into the above equation, we can obtain a = 4 mm. At this point, the rotation angle of the self-folding membrane hinge is 90°. This method can be applied to solving the geometry of membrane hinges at any folding angle (the folding angle ranges from 0° to 180°).

[0076] In actual operation, the pre-programmed dog bone-shaped specimen is processed according to the required length of the shape memory polymer membrane structure 3, and the middle strip of the required length is cut for use.

[0077] The above origami board is made of polylactic acid (PLA). The obtained shape memory polymer film structure is bonded and fixed to the origami board with glue.

[0078] The two-fold cardboard with the self-folding membrane hinge structure is initially in a horizontal state. When subjected to high temperature load again, the membrane hinge will fold outward. Figure 7 , Figure 9 The shapes of the membrane hinge before and after deformation are shown.

[0079] Compared to shape memory polymer membrane structures, polylactic acid (PLA) panels (folding boards) can be considered to maintain constant mechanical properties and geometry under thermal loads. A pre-programmed shape memory polymer membrane structure is combined with the panel to form a self-folding membrane hinge. Under thermal loads, the shape memory polymer membrane structure exhibits shape memory behavior, tending to recover its initial shape, while the geometry of the panel remains unchanged. This difference in deformation under thermal loads causes the membrane hinge to fold inwards to the target folding angle.

[0080] Example 2

[0081] See Figure 6-9 This embodiment illustrates another structure for connecting the self-folding film hinge structure of Embodiment 1 to the origami board. A platform area 4 is provided on the top surface of the origami board at the bonding position between the shape memory polymer film structure and the origami board. A groove 401 is provided in the platform area to facilitate the bonding of the shape memory polymer adhesive portion. Alternatively, after the adhesive portion is bonded, the platform area can be provided to conceal the shape memory polymer film structure bonding area within the origami panel area for a more aesthetically pleasing result.

[0082] Example 3

[0083] The self-folding membrane hinge structure adopted in the above embodiments can be applied to origami board with various complex origami structures, and can avoid the influence of the thickness of the origami board on the degree of freedom of folding.

[0084] The steps for making the corresponding origami cardboard using a self-folding membrane hinge structure are as follows:

[0085] S1. Draw a plan view of the origami board structure, and determine the dimensions of the origami board and the folding direction and folding angle of each crease;

[0086] S2. Calculate the hinge size of the self-folding film corresponding to each crease based on the size of the cardboard and the required folding angle of the crease;

[0087] S3. During the process of making origami, corresponding hinge structures are reserved on the edge of the origami, which are then processed by a 3D printer to obtain an origami panel with hinge structures on all four sides.

[0088] S4. In the corresponding area of ​​the adjacent origami board, according to the hinge plate size of the self-folding film hinge, paste the pre-stretched shape memory polymer film structure of the corresponding length to obtain the final origami structure.

[0089] In the above steps, since the bottom edge, thickness, and target folding angle of the hinge plate are known, the length of 'a' is calculated according to the aforementioned algorithm, thus determining the fixed edge length and outer arc shape of the hinge plate, and consequently, the geometric dimensions of the self-folding membrane hinge structure. Based on this, unit boards for the folding paperboard are integrally formed, and finally, shape memory polymer films of the required length are pasted at the target positions to complete the assembly and fabrication of the folding paperboard.

[0090] The obtained origami paper structure is shown in the following figure. Figure 10 , 11 The origami board includes an origami board body 5, and a hinge plate 6 is vertically mirrored on the outer side of each pair of opposite sides of the origami board body. The hinge plate is the structure of the first hinge plate or the second hinge plate mentioned in the previous embodiment. Adjacent origami boards are assembled by connecting them in the form of a shape memory polymer film structure 3 that has been pre-programmed as in the previous embodiment, so that the Miura origami board with no mechanical interference to the target folding angle can be obtained.

[0091] like Figure 12 , showed Figure 11 The image shows a reference diagram of the original and folded states of a Miura origami simulation product. This Miura origami is composed of a polylactic acid panel (red) and a pre-programmed shape memory polymer film structure (white), combined according to the hinge requirements of Miura origami during folding. When the origami structure is subjected to heat, the hinges fold spontaneously, causing the entire origami structure to fold.

[0092] Example 4

[0093] join Figure 13 , 14 The origami board includes a square origami board body 7. Hinge plates 5 are symmetrically arranged on the outer sides of each pair of opposite sides of the square origami board body. These hinge plates are the structure of the aforementioned first or second hinge plates. A platform area 4 is also provided in the middle of each square origami board body. Two recessed platforms are spaced apart on each side of the platform area. The bottom surface of the recessed platforms is used for bonding the shape memory polymer film structure's adhesive portion 301. Adjacent origami boards are assembled using a shape memory polymer film structure connection method with pre-programmed film hinge structures as described in Embodiments 1 or 2, resulting in a hexahedral folding board with a specific folding angle without mechanical interference.

[0094] like Figure 15 Show Figure 14 A reference view of a hexahedral origami cardboard simulation product and its folding deformation process. The deformation shown in the figure represents the deformation process of the hexahedral origami cardboard structure in a 65°C water bath.

[0095] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0096] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A self-folding membrane hinge structure based on shape memory polymer, disposed between two folded cardboard panels, characterized in that, The self-folding membrane hinge structure includes a first hinge plate, a second hinge plate, and a shape memory polymer membrane structure. The thickness of the first and second hinge plates is equal to the thickness of the folding cardboard. The ends of the first and second hinge plates near the folding cardboard are fixed to each folding cardboard, and the ends of the first and second hinge plates away from the folding cardboard are in contact with each other via a rolling arc surface. The shape memory polymer membrane structure includes two bonding portions and a deformable portion disposed between the bonding portions. The bonding portions are fixed to the top surface of the folding cardboard, and the deformable portion covers the top surface of the first and second hinge plates. During the process of the shape memory polymer membrane structure driving the folding cardboard to fold to the target angle, the first and second hinge plates rotate along the rolling arc surface. Each hinge plate includes a top surface and a bottom surface arranged in parallel, and an outer arc surface located between the top surface and the bottom surface. The side of the hinge plate opposite to the outer arc surface is fixedly connected to the folding paper; the outer arc surfaces of the two hinge plates form the rolling arc surface. On the longitudinal section of the self-folding membrane hinge structure, the first hinge plate is marked with ABCD. Assuming that the length of the bottom edge AB of the first hinge plate is L, the thickness of BC is b, and the length of the top edge CD is S, the center of the circle O' is the perpendicular of the straight line that is perpendicular to the bottom edge AB of the first hinge plate and passes through point D upwards, and the horizontal distance from the center O' to point A is a. Then the arc edge AD of the first hinge plate is 1 / 4 arc edge of an ellipse formed by O' as the center and a and b as radii.

2. The self-folding membrane hinge structure based on shape memory polymer according to claim 1, characterized in that, The shape memory polymer film structure is provided with one or more between adjacent folding plates; the shape memory polymer film structure is a rectangular shape memory polymer film, the length of the deformable part of the rectangular shape memory polymer film is equal to the sum of the bottom edges of the first and second hinge plates, and the adhesive parts at both ends of the rectangular shape memory polymer film are respectively set to ≥5mm in the length direction of the shape memory polymer film structure.

3. The self-folding membrane hinge structure based on shape memory polymer according to claim 1, characterized in that, When the first and second hinge plates are folded to the target folding angle θ by the shape memory polymer film structure, the straight lines containing the side lengths in the thickness direction of the first and second hinge plates extend and intersect to form the folding angle θ, and this intersection point is denoted by F; at this time, the tangent point of the two hinge plates on the rolling arc surface is denoted by E, and the intersection point of the straight line passing through point E and perpendicular to the line connecting EF with the bottom edge AB of the first hinge plate is denoted by O; then the length a on the bottom edge of the first hinge plate is obtained by the following algorithm: Establish a Cartesian coordinate system with point O' on the bottom edge of the first hinge plate as the origin and the positive x-axis along the BA direction. Solve for the geometric coordinates of points E and O using analytical geometry principles: Given the coordinates of points E and O, calculate the lengths of line segments OE and OB, where the coordinates of point B are (x, y). B ,y B )=(aL,0); Substitute the target folding angle θ into the following equation and solve analytically to obtain a, thereby determining the geometric dimensions of the self-folding membrane hinge structure; 4. The self-folding membrane hinge structure based on shape memory polymer according to claim 1, characterized in that, The first and second hinge plates of the self-folding membrane hinge structure are integrally formed with the folding cardboard that is fixed to them respectively.

5. The self-folding membrane hinge structure based on shape memory polymer according to claim 1, characterized in that, The shape memory polymer membrane structure is preloaded at high temperature and then cooled and unloaded to remember the stretching deformation, which acts as an actuator to drive the self-folding membrane hinge structure.

6. The application of the self-folding membrane hinge structure as described in any one of claims 1-5 in self-folding origami paperboard, characterized in that, The first and second hinge plates of the self-folding membrane hinge structure are respectively fixed at the connection of each pair of folded paperboards to be folded. The shape memory polymer film structure of the self-folding membrane hinge structure is covered on the folded side of each pair of folded paperboards. The adhesive portions at both ends of the shape memory polymer film structure are bonded to the two folded paperboards on the outside of the first and second hinge plates.

7. The application according to claim 6, characterized in that, The self-folding cardboard is either Miura cardboard or a hexahedral cardboard.

8. The application according to claim 7, characterized in that, The self-folding folding board is a Miura folding board, in which a first hinge plate or a second hinge plate is provided on the opposite sides of the unit plate of the Miura folding board, and adjacent unit plates of the Miura folding board are assembled and connected according to the self-folding film hinge structure; or, the self-folding folding board is a hexahedral folding board, in which the first hinge plate or the second hinge plate is provided on all four sides of the unit plate of the hexahedral folding board, and adjacent unit plates of the hexahedral folding board are assembled and connected according to the self-folding film hinge structure.

Images