Metamaterial based on curved surface origami, manufacturing method thereof, tactile module based on curved surface origami and method for generating active mechanical tactile sense

Abstract

The invention provides a metamaterial based on curved origami, a manufacturing method thereof, a tactile module based on curved origami and a method for generating active mechanical tactile sense. The metamaterial based on the curved surface origami comprises a panel, the panel is provided with a single curved surface crease extending in the longitudinal direction of the panel, and the single curved surface crease divides the panel into two surfaces on the two opposite sides of the panel. The panel is configured to fold along a single curved fold so as to form a fold angle between the two faces. The folding angle is configured to be adjustable so as to achieve a variable stiffness covering positive to negative stiffness when loaded in a vertical direction of the folding panel.

Description

Technical Field

[0001] The present invention relates to a metamaterial based on curved surface origami, a manufacturing method thereof, a tactile module based on curved surface origami, and a method for generating active mechanical tactile sensation. Background Art

[0002] The emerging metaverse driven by virtual reality (VR) and augmented reality (AR) technologies is transforming current digital media from a third-person perspective into a future immersive platform that vividly renders the physical environment perceived from a first-person perspective. This is achieved by constructing virtual environments with realistic sensory perceptions, including but not limited to vision, hearing, and touch. In this new paradigm of how humans interact with future media, VR / AR technologies are poised to penetrate a range of industry sectors (e.g., entertainment, communications, education, human-computer interaction, teleoperation, clinical treatment, and rehabilitation), while enhancing our VR / AR, tactile experiences with the help of advanced software (i.e., communications technology, various applications, and social networks) and hardware (i.e., VR / AR and haptic devices). Although state-of-the-art VR / AR devices provide stereoscopic visual and auditory sensory perceptions, they are unable to deliver a specific sensory dimension (i.e., touch) in the mechanical realm. Substantial progress has been made to make virtual worlds tactile by bringing passive tactile experiences to users; however, most produce simple, hand-centric motion constraints or vibrations (vibrotactile). This is in stark contrast to the physical environment where humans actively touch natural objects through their hands, feet or other body parts to feel their hardness, softness, and even the moment of breakage of fragile objects.

[0003] Active mechanical haptics, covering both positive stiffness (feeling hardness and softness) and negative stiffness (feeling cracks and falling moments), are considered to be core and part of the first sensory perceptions that humans use to explore / process information and create ontological metaphors in their daily interactions with the physical environment. Currently, these perceptions are missing in body-centered immersive environments. Studies have shown that real and active mechanical haptics can simultaneously induce physiological and psychological responses that are difficult to trigger with visual and auditory stimuli alone. In fact, haptics are very different from our visual and auditory perceptions, which are passive because we humans receive information as a third person. On the other hand, haptics are mainly active because the interaction initiated by actively touching / holding an object generates a sense of psychological ownership, thereby generating personal intrapersonal and interpersonal concepts. The combination of visual, auditory, and active touch sensory perceptions in AR / VR haptic experiences offers exciting potential for extending the realism of virtual worlds.

[0004] The present disclosure is provided to solve the above-mentioned defects in the background technology. Summary of the invention

[0005] Therefore, there is a need for a curved origami-based metamaterial, a method for manufacturing the same, a curved origami-based tactile module, and a method for generating active mechanical tactile sensations, which enable users to actively generate and perceive mechanical tactile sensations with controllable stiffness ranging from hard to soft and from positive to negative.

[0006] The present disclosure provides a metamaterial based on curved origami, a method for manufacturing the metamaterial, a tactile module based on curved origami, and a method for generating active mechanical tactile sensations. The disclosure introduces the mechanism, materials, design principles, system integration, and corresponding sensory perceptions of a human-initiated, body-centric, scalable, and wirelessly controllable tactile device uniquely realized by a curved origami module, enabling users to actively generate and perceive mechanical tactile sensations with controllable stiffness ranging from hard to soft and from positive to negative. These active tactile mechanical devices are designed to generate artificially triggered mechanical sensory perceptions. These devices are expected to enhance VR / AR experiences beyond visual and auditory perceptions, while providing a range of diverse and immersive experiences.

[0007] In a first embodiment of the present disclosure, a metamaterial based on curved origami includes a panel having a single curved crease extending in a longitudinal direction thereof, the single curved crease dividing the panel into two faces on opposite sides thereof. The panel is configured to be folded along the single curved crease so as to form a folding angle between the two faces. The folding angle is configured to be adjustable so as to achieve a variable stiffness ranging from positive stiffness to negative stiffness when loaded in a vertical direction of the folded panel.

[0008] In a second embodiment of the present disclosure, a method for manufacturing a metamaterial based on curved origami includes: providing a substrate; cutting a panel pattern on the substrate to obtain a panel, each panel having a single curved crease extending along a longitudinal direction, the single curved crease dividing the panel into two faces on opposite sides thereof. The method further includes: folding each panel along the single curved crease to form a folding angle between the two faces. The method further includes: connecting a connecting member to each panel, and by driving the connecting member, the folding angle between the two faces can be adjusted, thereby achieving a variable stiffness ranging from positive stiffness to negative stiffness when the folded panel is loaded in a vertical direction.

[0009] In a third embodiment of the present disclosure, a method for generating active mechanical tactile sensation includes: providing the curved origami-based metamaterial in the first embodiment of the present disclosure. The method further includes: presenting a virtual object in a virtual reality / augmented reality (VR / AR) scene to a user through at least one processor. The method further includes: enabling a user to load strain in the vertical direction of a folding panel, and converting the loaded strain into an interactive operation between the user and the virtual object in the VR / AR scene. The method further includes: determining, through at least one processor, a stiffness-related characteristic of the virtual object under the interactive operation of the user. The method further includes: adjusting the folding angle according to the determined stiffness-related characteristic of the virtual object under the interactive operation of the user through at least one processor, thereby achieving a stiffness ranging from positive stiffness to negative stiffness corresponding to the determined stiffness-related characteristic.

[0010] In a fourth embodiment of the present disclosure, a haptic module based on curved origami includes at least one curved origami-based metamaterial in the first embodiment of the present disclosure. The haptic module based on curved origami further includes at least one connecting member, wherein each panel is connected to at least one connecting member, and the connecting member is configured to be driven by a driving system to adjust the folding angle between two surfaces of the corresponding panel, so as to achieve a variable stiffness ranging from positive stiffness to negative stiffness when the corresponding folding panel is loaded in a vertical direction.

[0011] Other aspects of the disclosure will become apparent by consideration of the detailed description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In the drawings that are not necessarily drawn to scale, the same reference numerals may describe similar parts in different drawings. The same reference numerals with suffixes or different suffixes may represent different examples of similar parts. These figures generally illustrate various embodiments by way of example and not limitation, and together with the description and claims, are used to describe embodiments of the present disclosure. These embodiments are illustrative and are not intended to be exhaustive or exclusive embodiments of the present apparatus or method.

[0013] Figure 1a-1b The 2D pattern and 3D structure of the curved origami-based metamaterial according to an embodiment of the present disclosure are respectively shown.

[0014] Figure 2a The construction of a variant Miura origami with straight creases and rigid panels for theoretical modeling of curved origami is shown in accordance with an embodiment of the present disclosure.

[0015] Figure 2b The force-displacement relationship of a curved origami and a variant Miura origami according to an embodiment of the present disclosure is shown.

[0016] Figure 3a-3cThe working principles of stiffness manipulation of metamaterials based on curved origami according to the embodiments of the present disclosure are respectively shown.

[0017] Figure 4a The force-displacement relationship of the curved origami-based metamaterial at different adjustment angles according to an embodiment of the present disclosure is shown.

[0018] Figure 4b The drop acceleration for different adjustment angle static loads in the negative stiffness domain according to an embodiment of the present disclosure is shown.

[0019] Figure 5a The normalized force / displacement relationships resulting from creases, panels, and overall total effects according to embodiments of the present disclosure are shown.

[0020] Figure 5b-5g The normalized force / displacement relationship of the curved origami module according to the embodiments of the present disclosure is respectively shown.

[0021] Figure 6a Phase plots of normalized secant stiffness as a function of crease angle and adjustment angle are shown according to embodiments of the present disclosure.

[0022] Figure 6b A cyclic compression test of a curved origami module according to an embodiment of the present disclosure is shown.

[0023] Figure 7 and Figure 8a-8b The process of manufacturing a metamaterial based on curved origami according to an embodiment of the present disclosure is shown.

[0024] Fig. 9 The process of the method for generating active mechanical haptics according to an embodiment of the present disclosure is shown.

[0025] Figure 10a-Figure 10e The closed-loop haptic of the curved origami-based metamaterial generated according to an embodiment of the present disclosure is shown.

[0026] Figure 11a-Figure 11b The structure and working principle of a tactile in-hand device according to an embodiment of the present disclosure are respectively shown.

[0027] Figure 12a-12b The structure and working principle of the body-centered, lower limb-triggered pedaling device according to an embodiment of the present disclosure are respectively shown. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solution of the present disclosure, the present disclosure is described in detail below in conjunction with the drawings and specific embodiments. The embodiments of the present disclosure are further described in detail below in conjunction with the drawings and specific embodiments, but they are not intended to limit the present disclosure.

[0029] The words "first", "second" and the like used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprising" and other similar words indicate that the elements appearing before the word include the elements listed after the word, but do not exclude other elements.

[0030] In addition, although exemplary embodiments are described herein, the scope includes any and all embodiments based on the present disclosure with equivalent elements, modifications, omissions, combinations (e.g., scenarios where various embodiments intersect), adjustments, or changes. The elements of the claims are to be interpreted broadly based on the language used in the claims and are not limited to the examples described in this specification or during the practice of this application, which are to be considered non-exclusive. Therefore, this specification and examples should be considered merely as examples, with the true scope and spirit being indicated by the full scope of the following claims and their equivalents.

[0031] structure

[0032] Figure 1a and Figure 1b The 2D pattern and 3D structure of the metamaterial based on curved origami according to the embodiment of the present disclosure are shown respectively. Figure 1a and Figure 1b As shown, the metamaterial based on curved origami includes a panel having a single curved crease extending along its longitudinal direction, the crease dividing the panel into two faces at two opposite sides thereof. The panel is configured to be folded along the single curved crease to form a folding angle β between the two faces (see Figure 1b ), wherein the folding angle is configured to be adjustable so as to achieve a variable stiffness ranging from positive stiffness to negative stiffness when loaded in the vertical direction of the folding panel.

[0033] In a preferred embodiment, the single curved fold is formed by a circular arc cutting groove at a portion thereof, such as Figure 1a More preferably, the single curved fold is constructed from the following parts: two end extensions, a middle extension and two arc-shaped cutting grooves, each of the arc-shaped cutting grooves connects its adjacent end extension and middle extension.

[0034] like Figure 1a As shown, each of the arc-shaped cutting grooves includes a cutting line, where α is the angle between the normal line at the midpoint of the curved crease and the tangent line at the end of the curved crease, representing the normalized curvature of the crease; β is the angle between the two curved panels (i.e., the folding angle), representing the folding of the plastic origami. By simply introducing an arc-shaped cutting line characterized by an angle α, the relationship between the angle and the radius ρ of the circle is Where a×b is the geometric shape of a rectangular plate, and the curved origami can be formed by folding the two-dimensional panel along the curved crease. Figure 1b As shown, the folding angle β between the two surfaces is determined by the plasticity applied by the folding process. The greater the bending deformation of the bent panel, the smaller β is, and the smaller the bending deformation, the larger β is.

[0035] As mentioned above, for ease of explanation, Figure 1a and Figure 1b A rectangular 2D panel is used in the embodiment. However, the shape of the panel is not limited thereto, and other shapes such as a circle, a square, or an ellipse may also be used. However, in any of the above shapes, the bending angle (angle α) between the normal line at the midpoint of the curved fold and the tangent line at the end of the curved fold is fixed. Figure 1a In the specific example shown, the angle α between the horizontal edge and the tangent line at the end of the curved fold is fixed.

[0036] Curved origami belongs to the category of deformable origami and therefore has infinite degrees of freedom. Instead of using the finite element method to obtain the spatial distribution of stress and strain during deformation, an analytical analysis was used in terms of geometry and mechanics to combine curved origami (deformable origami) with Figure 2a The variant Miura origami (rigid origami) shown is bridged to allow for a detailed analysis of the mechanical properties of curved origami. Figure 2a The construction of a variant Miura origami with straight creases and a rigid panel for theoretical modeling of curved origami is shown, where the angle γ is related to the plastic folding angle β, i.e., γ(β). The model is then used to predict the stiffness of the curved origami and guide design choices. The solid lines represent the peak creases and the dashed lines represent the valley creases. After a vertical load is applied to the top of the origami, the curved origami will exhibit different force-displacement relationships depending on the competition between the bending deformation (providing positive stiffness) and the folding deformation along the curved creases (providing negative stiffness). Figure 2b The force-displacement relationship of a curved origami and a variant Miura origami (defined as α=80° and a / b=1.25) at different folding angles β (i.e., initial state) of 60°, 90°, and 120° is shown, where the horizontal axis represents the compressive vertical displacement caused by the vertical load applied to the top of the origami, and the vertical axis represents the normalized force generated by the folded panel accordingly.

[0037] In a preferred embodiment, the folding panel is configured to exhibit positive stiffness and negative stiffness when the folding angle β is within a first angle range, and to exhibit only positive stiffness when the folding angle β is within a second angle range, wherein the first angle range is greater than the second angle range and greater than the angle threshold. Figure 2b It can be seen that when the folding angle β is 90° or 120°, the folded panel exhibits positive stiffness and negative stiffness, while when the folding angle β is 60°, only positive stiffness is exhibited.

[0038] Further, in this embodiment, if the folding angle β is within the first angle range, the folding panel is configured to exhibit negative stiffness when the compressive vertical displacement is greater than the first displacement threshold, and exhibit positive stiffness when the compressive vertical displacement is less than the first displacement threshold. For example, when the folding angle β is 120°, the normalized force increases with displacement (positive stiffness) and then decreases (negative stiffness).

[0039] Therefore, for a given curved origami (i.e., a given angle β), the stiffness can be easily tuned by changing the folding angle β using the curved origami-based metamaterial, e.g., by Figure 3a-3c The connecting member driving method shown in the figure, wherein the connecting member is constructed to include, for example, a cable connecting two surfaces. Specifically, Figure 3a An initial state of a curved origami-based metamaterial with an integrated cable and a fixed edge is shown, wherein a first hole is cut on one of the two surfaces and a second hole is cut on the other of the two surfaces for the cable to pass through the two holes in sequence, for example, a knotted portion of the cable is suppressed by the first hole, thereby performing a pulling operation to reduce the folding angle or a releasing operation to increase the folding angle. Figure 3b It is shown that the folding angle β is changed by Δβ through a pulling operation using a cable. Figure 3c It is shown that when the curved origami is actively pressed in the vertical direction, the combined panel bending and origami folding define its stiffness.

[0040] Figure 4a The metamaterial based on curved origami (where α = 80°, β = 120° and a / b = 1.25) is shown by Figure 3a-3c The force-displacement relationship of the cable-pulling method shown in at different cable-pulling angles Δβ = 0°, 35°, and 60° presents stiffnesses spanning both the positive and negative ranges. This establishes the effectiveness of using the cable-driven approach to adjust the stiffness of the origami in real time. As for tactile perception, different positive stiffness values ​​reflect the level of hardness, while negative stiffness mimics the feeling of crushing an object or dropping it. Therefore, during the process of actively pressing the origami with negative stiffness with a constant force, its acceleration becomes an important indicator to characterize this feature. Figure 4a For the same curved origami, when β = 120° and Δβ = 0°, 35°, and 40°, the acceleration of the static load (i.e., constant force) can be as high as 0.6G (free fall is 1G), as shown in Figure 4b shown.

[0041] In addition to the fold angle β described above, the stiffness of the folded panel can also vary as a function of the panel material, panel geometry, arrangement of the cut grooves, and the bending angle α between the normal at the midpoint of the curved crease and the tangent at the end of the curved crease.

[0042] For example, Figure 5a The figure shows the normalized force / displacement relationship produced by the creases, panels, and overall total effect. As shown in the figure, the creases and panels provide negative and positive stiffness, respectively. Obviously, by properly configuring the creases and panels, the mechanical response of the curved origami can be designed as desired. Figure 5b-5d The normalized force / displacement relationship of the curved origami modules with different initial folding angles β are respectively shown, where the angle α=50°, 60°, and 70°. Figure 5e-5g The normalized force / displacement relationship of the curved origami module with a fixed initial folding angle β=120° and different controllable angles Δβ are respectively shown, where the angle α=50°, 60°, and 70°.

[0043] To guide the design of curved origami to achieve more significant mechanical perception, Figure 6a A phase diagram of normalized secant stiffness as a function of crease angle α (30°<α<85°) and adjustment angle Δβ is provided, wherein the initial folding angle β=120°, i.e., the actual angle when the cable is pulled, ranging from 0° to 120°. In order to utilize the most significant stiffness perception, when the origami has a range of both positive and negative stiffness, only the maximum negative stiffness is selected. When it has only a positive stiffness range, the maximum positive stiffness is adopted. From a practical point of view, the angle α is a predetermined parameter because it defines the curved origami pattern. Therefore, the phase diagram provides a design (through angle α) and an operating guide (through adjustment angle Δβ) for achieving stiffness sensory perception using curved origami. For example, in order to obtain both positive and negative stiffness, the bending angle α between the tangent at the end of the curved crease and the normal at the midpoint of the curved crease is set between 55° and 85°, and the folding angle β is adjusted between 30° and 130°.

[0044] Similar to the elastic deformation during cable pulling, the deformation during cyclic pressing on the top of the curved origami is also elastic ( Figure 6b ), where both negative and positive stiffness can be clearly seen in each cycle.

[0045] Manufacturing method

[0046] Reference Figure 7 and Figure 8a-8b , the following describes a method for manufacturing a metamaterial based on curved origami according to an embodiment of the present invention. When manufacturing a metamaterial based on curved origami, a curved origami pattern is produced based on 2D processing and manual folding. Figure 7 In the present invention, the manufacturing method 100 includes the following steps.

[0047] At step S110 , the method includes providing a substrate.

[0048] A substrate of various materials can be used to make a curved origami pattern. Preferably, the substrate of the panel is made of plastic, metal or alloy. Here, the handheld device (described later) uses a PET (polyethylene terephthalate) film with a thickness of 0.2 mm (as an example of plastic), and the treading device (described later) uses a 65Mn spring steel plate with a thickness of 0.15 mm (as an example of alloy).

[0049] At step S120 , the method includes cutting a pattern of panels on a substrate to obtain panels, each panel having a single curved fold extending along a longitudinal direction, the fold dividing the panel into two faces at two opposite sides thereof.

[0050] like Figure 8a As shown, the panel pattern includes edges, arc-shaped cutting grooves, and holes in the panel. The contours and creases of the curved origami made of PET film were made using a Silhouette Cameo 3 cutting machine (Silhouette America Inc.), and the contours and creases made of spring steel were made using an industrial engraving machine.

[0051] At step S130 , the method includes folding each panel along the single curved crease to form a folding angle between two surfaces.

[0052] Initial manual folding forms the 3D structure of the curved origami starting from the 2D sheet and determines the initial fold angles.

[0053] At step S140 , the method includes coupling a connection member to each panel, and the folding angle between two faces can be adjusted by driving the connection member to achieve variable stiffness ranging from positive stiffness to negative stiffness when the folding panel is loaded in a vertical direction.

[0054] In order to actively control the folding angle in real time and achieve stiffness adjustment, such as Figure 8a As shown, each panel also has a first hole and a second hole located on both sides of the cutting groove, and the connecting member can be connected to each panel in the following manner. First, a cable can be used as a connecting member, and the cable passes through the first hole and the second hole of each panel in sequence, so that both sides of the cable extend out of the corresponding surface. Then, one side of the cable (the side opposite to the second hole of the first hole) can be knotted so that the other side of the cable can be driven while being prevented from passing through the first hole and the second hole.

[0055] In particular, a cable (connecting member) is inserted through two holes (i.e., a first hole and a second hole) on a panel of the curved origami, with one side being tied behind the panel. It should be noted that the size of the cable knot is larger than the size of the first hole so that when the other side of the cable is driven to reduce the folding angle, it can be maintained against the first hole without passing through the first hole. In this way, by pulling and releasing the inserted cable, the movement of the movable panel can be controlled to form an adjustable folding angle relative to the fixed panel.

[0056] In a preferred embodiment, Figure 8b As shown, before cutting the panel pattern, a sensor layer is deposited on the substrate on the origami structure by an easily replicable coating method, and the sensor layer is used to sense the loaded strain and change its electrical properties. Specifically, the deposition of the sensor layer on the substrate includes: coating a suspension including the sensor layer material onto the substrate and drying it in a vacuum oven at 120°C for 6 hours. In a preferred embodiment, the sensor layer can be made of various materials, such as silver nanowires (AgNW, XFNano Inc.), graphene, etc.

[0057] application

[0058] In an embodiment of the present disclosure, a haptic module based on curved origami is provided as an application of a metamaterial based on curved origami. The haptic module based on curved origami includes at least one metamaterial based on curved origami and at least one connecting member as described above, wherein each panel is connected to at least one connecting member, and the connecting member is configured to be driven by a driving system to adjust the folding angle between two faces of the corresponding panel, so as to achieve a variable stiffness ranging from positive stiffness to negative stiffness when the corresponding folded panel is loaded in the vertical direction.

[0059] Furthermore, in order to establish a two-way interface between the physical world and the virtual world, a closed-loop tactile sensation is constructed using a curved origami-based tactile module, using a curved origami-based metamaterial coated with AgNWs as the medium. Fig. 9 , describes a method for generating active mechanical tactile sensations. Fig. 9 As shown, the generation method 200 includes the following steps.

[0060] In step S210, a metamaterial based on curved origami according to any embodiment of the present disclosure is provided.

[0061] Specifically, this step can be performed as follows: presetting the bending angle between the tangent line at the end of the curved surface crease and the normal line at the midpoint of the curved surface crease within a range of 55° to 85°, within which the folding panel can exhibit positive stiffness and negative stiffness.

[0062] In step S220, the virtual object is presented to the user in a virtual reality / augmented reality (VR / AR) scene through at least one processor.

[0063] In step S230 , the user is enabled to apply strain in the vertical direction of the folding panel, and the applied strain is converted into an interactive operation between the user and the virtual object in the VR / AR scene.

[0064] Specifically, this step can be performed by the following means: a pressing member is set on the top of multiple curved origami-based metamaterials, so that when the user presses and / or releases the pressing member, the curved origami-based metamaterial is displaced accordingly in the vertical direction; and the achieved stiffness corresponding to the determined stiffness-related characteristics can be perceived by the user via the pressing member.

[0065] In step S240, the stiffness-related characteristics of the virtual object under the user's interactive operation are determined by at least one processor.

[0066] In step S250, at least one processor is used to adjust (regulate) the folding angle according to the determined stiffness-related characteristics of the virtual object under the user's interactive operation, so as to achieve a stiffness ranging from positive stiffness to negative stiffness corresponding to the determined stiffness-related characteristics.

[0067] Specifically, if the determined stiffness-related characteristic is hard or soft, the folding angle is adjusted so that the folding panel exhibits positive stiffness; if the determined stiffness-related characteristic is broken or dropped, the folding angle is adjusted at an angle greater than the positive stiffness so that the folding panel exhibits negative stiffness.

[0068] Further, the method 200 may also include depositing a sensor layer on each panel, so that the user's pressing operation and / or releasing operation on the pressing member is sensed by the sensor layer as a resistance change; and converting the resistance change into a voltage change. Then, the VR / AR processor may perform the following processing: obtaining the voltage change, determining the corresponding interaction operation between the user and the virtual object in the VR / AR scene according to the voltage change, and presenting the corresponding interaction operation of the user together with the virtual object in the VR / AR scene.

[0069] In an embodiment of the present invention, the corresponding interaction operation between the user and the virtual object includes breaking, crushing or falling off the virtual object.

[0070] Figure 10a-Figure 10e The closed-loop tactile sensations generated based on the curved origami-based metamaterial according to the embodiments of the present disclosure are respectively shown, wherein: Fig.10a Figure 2 shows a schematic diagram of a curved origami-based metamaterial coated with AgNW as an interface between the physical and virtual environments. Fig.10bThe figure shows the system integration and circuit diagram of the tactile device built using curved origami. Fig.10c The figure shows the resistance of the coated AgNW sensing layer when cyclically compressed at different folding angles of the curved origami (α = 80° and β = 120°). Fig.10d The figure shows the deformation response of the virtual object triggered by the actual deformation of the origami module during active cyclic compression, demonstrating the highly synchronized deformation between the physical and virtual environments connected by the origami. Fig.10e The figure shows the power consumption of the actuation system during haptic processing.

[0071] By combining the tactile perception generated by actively pressing the origami-based metamaterial with the synchronized visual information from traditional VR devices, a highly immersive, touchable closed-loop virtual world can be constructed, such as Fig.10a Here, through the touch or press action initiated by the user through the haptic device, the user can actively and physically feel what she / he sees in VR, where the origami-based metamaterial is the key stiffness-adjusting component. Virtual scenes (e.g., city landscapes, ice surfaces, grass fields, see Fig.10a ) acts as a tactile device (e.g. Fig.10a Based on this input, the folding angle β is adjusted by an integrated motor by Δβ to simulate the expected stiffness response of what the user sees in the VR device. Therefore, the user can feel the mechanical stiffness of the objects seen in the VR device in real time through active hand grasping or body-centered foot-stepping actions. On the other hand, the user's active interaction with the origami-based metamaterial (such as pressing) is recorded as resistance changes, which is achieved through silver nanowires (AgNW) deposited on the origami panel as a sensing layer. These changes are then converted into voltage changes ( Fig.10b ). The voltage changes on the haptic device are wirelessly communicated with the virtual environment engine (such as Unity) in the PC, and then wirelessly transmitted to the VR device to provide the necessary changes in real time, such as breaking the ice surface when the user triggers negative stiffness. Of course, if the determined stiffness-related characteristics of the virtual object will cause changes in the virtual object or its environment under the user's interactive operation, the virtual environment engine can present the corresponding changed VR / AR scene to the user.

[0072] Fig.10cThe figure shows the relative resistance change (ΔR / R0) of the sensing layer during periodic and active pressing on the curved origami (with a nominal strain of 30% height change) at different folding angles (β = 120°, Δβ = 0°, 30°, 60° and 90°). Two characteristics are observed here: first, the change in resistance is highly repeatable during periodic pressing and release; second, the influence of the folding angle Δβ is negligible, which is very important for using a general algorithm (i.e., a Δβ-independent algorithm) to change the virtual environment. Therefore, in active human interaction, the virtual environment changes according to the deformation measured by the resistance change. Fig.10d The device is shown to have very stable virtual-real synchronization via its wireless transmission system. Note that the integrated motor drive cable is activated only when the folding angle of the curved origami needs to be changed according to the virtual scene. It then provides the user with a variety of stiffness perceptions without further complex control algorithms or additional actuation. Therefore, only about 150mW of power dissipation is generated when adjusting the stiffness ( Fig.10e ), resulting in an energy-efficient system for human-triggered active haptics.

[0073] As specific examples of curved origami-based haptics, a handheld haptic device and a body-centered stepping device will be described below.

[0074] The object-like handheld tactile device provides human-triggered active mechanical tactile sensations with stiffness sensing covering both positive and negative ranges. The device consists of four main subsystems: Fig.11a ): 1) Five buttons, built with origami-based metamaterials, that generate virtual-physical environment feedback when actively pressed by the user; 2) An actuation system that adjusts the stiffness of the origami-based metamaterial by transmitting motor rotation to cable pull / release actions; 3) Electronic control components, namely microcontrollers, for feedback loops (i.e. stiffness adjustment, actuation, sensing) and wireless transmission; and 4) A support shell that accommodates buttons based on finger positions, electronics, and ergonomic considerations to enable human gripping actions. The origami module connects the virtual environment with actual perception, achieving "what the user sees is what the user feels" ( Fig.11b ) feeling.

[0075] On the other hand, a body-centered, lower-limb-triggered pedaling device was developed that integrates larger-scale origami-based metamaterials to support full-body motion and provide corresponding stiffness perception, which will further expand immersive active mechanical tactile sensations beyond the hand-centered experience. The pedaling device consists of four main subsystems ( Fig.12a): 1) A mobile tactile platform for pedaling interaction; 2) A tessellation for user weight support and feedback during active pedaling; 3) A base platform for positioning the tessellation and supporting the entire structure; 4) An actuation system that adjusts the stiffness of the tessellation by transmitting the motor rotation to the folds of the tessellation through cables. The two-stage transmission of the parallel worm gears and multi-knot cables can simultaneously adjust the stiffness of the tessellation and generate a variety of closed-loop tactile perceptions. The device realizes "what the user is immersed in is what the user steps on" ( Figure 12b ).

[0076] The active mechanical haptics based on origami-based metamaterials introduced in this paper use delicate origami as a medium between the virtual environment and the physical environment to create a human-centered active tactile experience with high-fidelity stiffness perception from positive to negative. The mechanism shifts from the existing machine-triggered passive tactile to a human-triggered interface that is closer to interacting with the physical universe. In addition, by reproducing the heartbeat moment of crushing an object or losing one's footing, as well as touching and pressing objects of different hardness, the newly introduced negative stiffness as well as various positive stiffness can significantly enrich the user's immersive experience in the virtual world. The working principle and characteristics combined with the system's integration strategy make the system easily replicable. Two demonstration devices (i.e., a handheld device and a pedaling device) quantitatively verify that users can feel high-fidelity first-person sensory, physiological, and psychological experiences in the constructed highly immersive virtual environment, further affirming the potential for widespread use of the device.

[0077] The above description is intended to illustrate rather than limit. For example, the above examples (or one or more solutions thereof) can be used in combination with each other. For example, a person of ordinary skill in the art may use other embodiments when reading the above description. In addition, in the above-mentioned specific embodiments, various features can be combined together to simplify the present disclosure. This should not be interpreted as an intention that the features that do not need to be protected in the present disclosure are necessary for any claim. On the contrary, the subject matter of the present disclosure may be less than the full range of features of the specific disclosed embodiments. Therefore, the following claims are incorporated herein as examples or embodiments in the specific embodiments, and each claim is separately used as a separate embodiment, and it should be considered that these embodiments can be combined with each other in various combinations or arrangements. The scope of the present disclosure should be determined with reference to the full scope of the attached claims and the equivalent forms to which these claims are assigned.

[0078] The above embodiments are only exemplary embodiments of the present disclosure and are not intended to limit the present disclosure. The protection scope of the present invention is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present disclosure, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present invention.

Claims

1. A metamaterial based on curved origami, characterized in that: include: A panel having a single curved fold extending in a longitudinal direction thereof, wherein the single curved fold divides the panel into two faces at two opposite sides thereof; The panel is configured to be folded along the single curved crease to form a fold angle between the two faces; The folding angle is configured to be adjustable so as to achieve variable stiffness ranging from positive stiffness to negative stiffness when the folding panel is loaded in a vertical direction.

2. The curved origami-based metamaterial according to claim 1, characterized in that: The single curved fold is partially formed by an arc-shaped cutting groove.

3. The curved origami-based metamaterial according to claim 2, characterized in that: The single curved fold is constructed from the following parts: two end extensions, a middle extension and two arc-shaped cutting grooves, each of which connects its adjacent end extension and middle extension.

4. The curved origami-based metamaterial according to claim 3, characterized in that: The cutting groove includes a cutting line.

5. The curved origami-based metamaterial according to claim 1, characterized in that: The bending angle between the normal line at the midpoint of the curved surface crease and the tangent line at the end of the curved surface crease is fixed.

6. The curved origami-based metamaterial according to claim 1, characterized in that: The folding panel is constructed to exhibit positive stiffness and negative stiffness when the folding angle is within a first angle range, and to exhibit only positive stiffness when the folding angle is within a second angle range, wherein the first angle range is greater than the second angle range and greater than an angle threshold.

7. The curved origami-based metamaterial according to claim 6, characterized in that: If the folding angle is within the first angle range, the folding panel is configured to exhibit negative stiffness when the compressive vertical displacement is greater than a first displacement threshold, and to exhibit positive stiffness when the compressive vertical displacement is less than the first displacement threshold.

8. The curved origami-based metamaterial according to claim 6, characterized in that: The stiffness of the folded panel varies depending on the material of the panel, the geometry of the panel, the fold angle, and the bending angle between the normal line at the midpoint of the curved crease and the tangent line at the end of the curved crease.

9. The curved origami-based metamaterial according to claim 2, characterized in that: The stiffness of the folded panel varies depending on the material of the panel, the geometry of the panel, the arrangement of the cut grooves, the folding angle, and the bending angle between the normal line at the midpoint of the curved crease and the tangent line at the end of the curved crease.

10. The curved origami-based metamaterial according to claim 1, characterized in that: The bending angle between the tangent line at the end of the curved surface crease and the normal line at the midpoint of the curved surface crease is set in the range of 55° to 85°, and the folding angle is adjusted between 30° and 130°.

11. The curved origami-based metamaterial according to claim 1, characterized in that: The panel is made of plastic, metal or alloy.

12. The curved origami-based metamaterial according to claim 11, characterized in that: The panel is made of a substrate of plastic, metal or alloy on which a sensor layer is deposited for sensing the strain of loading and changing its electrical properties.

13. The curved origami-based metamaterial according to claim 11, characterized in that: A first hole is cut on one of the two surfaces, and a second hole is cut on the other of the two surfaces, so that a connecting member passes through the two holes in sequence, thereby performing a pulling operation for reducing the folding angle or a releasing operation for increasing the folding angle.

14. The curved origami-based metamaterial according to claim 13, characterized in that: At least one of the first hole and the second hole is sized to prevent a knotted portion of the connecting member from passing therethrough.

15. The curved origami-based metamaterial according to claim 13, characterized in that: The connecting member includes a cable.

16. A method for manufacturing a metamaterial based on curved origami, characterized in that: include: providing a substrate; Cutting a panel pattern on the substrate to obtain panels, each panel having a single curved fold extending along the longitudinal direction, the single curved fold dividing the panel into two surfaces at two opposite sides thereof; folding each panel along the single curved crease to form a fold angle between the two faces; A connection member is coupled to each panel, and the folding angle between the two faces can be adjusted by driving the connection member, thereby achieving a variable stiffness ranging from positive stiffness to negative stiffness when loaded in the vertical direction of the folding panel.

17. The method according to claim 16, characterized in that The single curved fold is partially formed by an arc-shaped cutting groove.

18. The method according to claim 17, characterized in that Each panel also has a first hole and a second hole located on both sides of the cutting groove; Connecting the connecting members to each panel further comprises: Passing the cable as the connecting member through the first hole and the second hole of each panel in sequence, so that both sides of the cable extend out of the corresponding surface; One side of the cable is knotted on the side of the first hole opposite to the second hole so that the other side of the cable can be driven.

19. The method according to claim 18, characterized in that The size of the cable knot is larger than the size of the first hole so that when the other side of the cable is driven to reduce the folding angle, it can be maintained against the first hole without passing through the first hole.

20. The method according to claim 16, characterized in that Further including: Before cutting the panel pattern, a sensor layer for sensing the applied strain and changing its electrical properties is deposited on the substrate.

21. The method according to claim 20, characterized in that Depositing the sensor layer on the substrate further includes: coating a suspension of the material comprising the sensor layer onto the substrate and drying.

22. The method according to claim 18, characterized in that The panel pattern includes an edge, the arc-shaped cutting groove and holes of the panel.

23. The method according to claim 17, characterized in that For each panel, two arc-shaped cutting grooves are cut so that there is a middle extension between the two cutting grooves and each cutting groove has adjacent end extensions.

24. The method according to claim 17, characterized in that The panel is cut into an initial rectangular shape with a horizontal bottom edge, and the arc-shaped cutting groove is cut so that the normal at its midpoint is parallel to the horizontal bottom edge, and the bending angle between the tangent at the end of the cutting groove or the curved fold and the horizontal bottom edge is set in the range of 55° to 85°.

25. The method according to claim 16, characterized in that The substrate is made of plastic, metal or alloy.

26. A method for generating active mechanical tactile sensation, characterized in that: The method comprises: Providing the curved origami-based metamaterial according to claim 1; Presenting virtual objects in a virtual reality / augmented reality (VR / AR) scene to a user via at least one processor; Enable the user to load strain in the vertical direction of the folding panel, and convert the loaded strain into an interactive operation between the user and the virtual object in the VR / AR scene; Determining, by at least one processor, a stiffness-related characteristic of the virtual object under the interactive operation of the user; The folding angle is adjusted according to the determined stiffness-related characteristic of the virtual object under the interactive operation of the user through the at least one processor, so as to achieve a stiffness ranging from positive stiffness to negative stiffness corresponding to the determined stiffness-related characteristic.

27. The method according to claim 26, characterized in that Adjusting the folding angle according to the determined stiffness-related characteristic of the virtual object further comprises: If the determined stiffness-related characteristic is hard or soft, adjusting the folding angle so that the folded panel exhibits positive stiffness; If the stiffness-related characteristic determined is cracking or falling, the folding angle is adjusted to an angle greater than that for positive stiffness, so that the folding panel exhibits negative stiffness.

28. The method according to claim 26, characterized in that Further including: If it is determined that the stiffness-related characteristic of the virtual object under the interactive operation of the user will cause the virtual object or its environment to change, the corresponding changed VR / AR scene is presented to the user through the at least one processor.

29. The method according to claim 27, characterized in that Enabling the user to apply strain in the vertical direction of the folding panel further comprises: A pressing member is arranged on the top of the plurality of curved origami-based metamaterials, so that when the user presses and / or releases the pressing member, the curved origami-based metamaterial is displaced in the vertical direction accordingly; And the achieved stiffness corresponding to the determined stiffness-related characteristic can be perceived by the user via the pressing member.

30. The method according to claim 29, characterized in that Further including: Depositing a sensor layer on each panel so that a pressing operation and / or a releasing operation of the user on the pressing member is sensed by the sensor layer as a resistance change; converting the resistance change into a voltage change; The following processing is performed by the VR / AR processor: acquiring the voltage change, determining the corresponding interaction operation between the user and the virtual object in the VR / AR scene according to the voltage change, and presenting the corresponding interaction operation of the user together with the virtual object in the VR / AR scene.

31. The method according to claim 30, characterized in that The corresponding interaction operation between the user and the virtual object includes breaking, crushing or falling off the virtual object.

32. The method according to claim 26, characterized in that A metamaterial based on curved origami is provided, further comprising: presetting a bending angle between a tangent line at an end of a curved crease and a normal line at a midpoint of the curved crease within a range of 55° to 85°, within which a folded panel can exhibit positive stiffness and negative stiffness.

33. A tactile module based on curved origami, characterized in that: include: At least one curved origami-based metamaterial according to any one of claims 1 to 15, At least one connecting member, wherein each panel is connected to the at least one connecting member, and the connecting member is configured to be driven by a drive system to adjust the folding angle between two faces of the corresponding panel, thereby achieving a variable stiffness ranging from positive stiffness to negative stiffness when loaded in the vertical direction of the corresponding folding panel.

34. The tactile module based on curved origami according to claim 33, characterized in that: For each curved origami-based metamaterial, a first hole is cut on one surface, and a second hole is cut on another surface; The connecting member includes a cable, and the cable is configured to pass through the first hole and the second hole in sequence, so as to be pulled by the driving system to reduce the folding angle or released by the driving system to increase the folding angle.

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