Origami-inspired Folding Research Articles

Origami-inspired soft fluidic actuation for minimally invasive large-area electrocorticography

Electrocorticography is an established neural interfacing technique wherein an array of electrodes enables large-area recording from the cortical surface. Electrocorticography is commonly used for seizure mapping however the implantation of large-area electrocorticography arrays is a highly invasive procedure, requiring a craniotomy larger than the implant area to place the device. In this work, flexible thin-film electrode arrays are combined with concepts from soft robotics, to realize a large-area electrocorticography device that can change shape via integrated fluidic actuators. We show that the 32-electrode device can be packaged using origami-inspired folding into a compressed state and implanted through a small burr-hole craniotomy, then expanded on the surface of the brain for large-area cortical coverage. The implantation, expansion, and recording functionality of the device is confirmed in-vitro and in porcine in-vivo models. The integration of shape actuation into neural implants provides a clinically viable pathway to realize large-area neural interfaces via minimally invasive surgical techniques.

Mountain-valley crease reconfiguration of 4-crease origami vertices and tessellations

Reconfigurable origami-inspired folding has recently gained significant attention due to its potential to achieve multi-shape changes through crease topological morphing, resulting in multi-functionality from a single original structure. However, it is one of the major challenges to determine all possible mountain-valley crease (MV) assignments that ensure rigid foldability and obtain duplicate configurations in large 2D origami tessellations or 3D cellular structures. In this study, we developed a straightforward algorithm that combines graphic representation and motion compatibility conditions to assess the reconfigurability of origami structures with 4-crease vertices including double corrugated, Miura-ori, and symmetric Eggbox vertices, as well as their 2D and even 3D cellular tessellations. Our analysis has revealed three types of oligo-modal origami tessellations characterised by a consistent number of MV assignments independent of tessellation size, and pluri-modal cellular origami structures that exhibit negative, zero, and positive Poisson's ratios which were verified through experiment. This work could serve as a stepping stone towards developing multifunctional metamaterials and devices based on reconfigurable origami through mountain-valley crease assignment.

Bistable origami-inspired acoustics metasurface for dynamic beam scanning

The synergistic integration of acoustic metasurfaces with the adaptive reconfigurability of origami art has demonstrated significant promise in thedynamic modulation of sound waves. This paper proposes an innovative approach to acoustic metasurfaces that incorporates bistable origami-inspired folding structure and digital coding to enable dynamic reconfiguration of beam scanning. The unit cell of the metasurface is optimized to realize two equilibrium states with 180-degree phase difference that can be coded as binary 0 and 1. In particular, by programming each element of the metasurface with different coding sequences, two symmetric reflected acoustic beams can be manipulated at different angles. The proposed design signifies a noteworthy advancement in the field of acoustic metasurfaces, offering a flexible and versatile solution applicable to acoustic imaging, communication, and sensing applications.

A Highly Compact Zip Chain Arm with Origami-Inspired Folding Chain Structures.

A deployable robotic arm can be a useful tool for mobile systems to widen accessible areas without removing mobility. For practical use, the deployable robotic arm needs to satisfy two requirements: a high extension-compression ratio and robust structural stiffness against the environment. To this end, this paper suggests, for the first time, an origami-inspired zipper chain to achieve a highly compact, one-degree-of-freedom zipper chain arm. The key component is the foldable chain, which innovatively increases the space-saving capability in the stowed state. The foldable chain is fully flattened in the stowed state, allowing for storage of many more chains in the same space. Moreover, a transmission system was designed to transform a 2D flat pattern into a 3D chain shape in order to control the length of the origami zipper. Additionally, an empirical parametric study was performed to choose design parameters to maximize the bending stiffness. For the feasibility test, a prototype was built and performance tests were executed in relation to extension length, speed, and structural robustness.

Controlled metal crumpling as an alternative to folding for the fabrication of nanopatterned meta-biomaterials

We designed and fabricated a simple setup for the controlled crumpling of nanopatterned, surface-porous flat metallic sheets for the fabrication of volume-porous biomaterials and showed that crumpling can be considered as an efficient alternative to origami-inspired folding. Before crumpling, laser cutting was used to introduce pores to the sheets. We then fabricated titanium (Ti) nanopatterns through reactive ion etching on the polished Ti sheets. Thereafter, nanopatterned porous Ti sheets were crumpled at two deformation velocities (i.e., 2 and 100 mm/min). The compression tests of the scaffolds indicated that the elastic modulus of the specimens vary in the range of 11.8–13.9 MPa. Micro-computed tomography scans and computational simulations of crumpled scaffolds were performed to study the morphological properties of the resulting meta-biomaterials. The porosity and pore size of the scaffolds remained within the range of those reported for trabecular bone. Finally, the in vitro cell preosteoblasts culture demonstrated the cytocompatibility of the nanopatterned scaffolds. Moreover, the aspect ratio of the cells residing on the nanopatterned surfaces was found to be significantly higher than those cultured on the control scaffolds, indicating that the nanopatterned surface may have a higher potential for inducing the osteogenic differentiation of the preosteoblasts.

Origami-inspired folding assembly of dielectric elastomers for programmable soft robots

Origami has become an optimal methodological choice for creating complex three-dimensional (3D) structures and soft robots. The simple and low-cost origami-inspired folding assembly provides a new method for developing 3D soft robots, which is ideal for future intelligent robotic systems. Here, we present a series of materials, structural designs, and fabrication methods for developing independent, electrically controlled origami 3D soft robots for walking and soft manipulators. The 3D soft robots are based on soft actuators, which are multilayer structures with a dielectric elastomer (DE) film as the deformation layer and a laser-cut PET film as the supporting flexible frame. The triangular and rectangular design of the soft actuators allows them to be easily assembled into crawling soft robots and pyramidal- and square-shaped 3D structures. The crawling robot exhibits very stable crawling behaviors and can carry loads while walking. Inspired by origami folding, the pyramidal and square-shaped 3D soft robots exhibit programmable out-of-plane deformations and easy switching between two-dimensional (2D) and 3D structures. The electrically controllable origami deformation allows the 3D soft robots to be used as soft manipulators for grasping and precisely locking 3D objects. This work proves that origami-inspired fold-based assembly of DE actuators is a good reference for the development of soft actuators and future intelligent multifunctional soft robots.

Circularly‐polarised origami‐inspired folding patch antenna sub‐array

This work discusses the design of a microstrip patch antenna and its use as an orientation-agnostic radiator in an origami-inspired folding antenna array. The antenna is based on a perturbed circular patch design that is impedance matched to reside in a radial feed network for a 2 × 2 array. This 2 × 2 array can be switched to provide sum and difference pattern behaviour. Both the feed network and the ground plane are modified to enable folding of the structure according to the Miura-ori pattern. The performance of a circularly polarised array is evaluated for a comprehensive range of fold angles to evaluate the impact of physical reconfiguration. Results for a simulated and fabricated circularly polarised array are provided for a 3 GHz design.

Hyperbolic origami-inspired folding of triply periodic minimal surface structures

Origami-inspired folding methods present novel pathways to fabricate three-dimensional (3D) structures from 2D sheets. A key advantage of this approach is that planar printing and patterning processes could be used prior to folding, affording enhanced surface functionality to the folded structures. This is particularly useful for 3D lattices, possessing very large internal surface areas. While folding polyhedral strut-based lattices has already been demonstrated, more complex, curved sheet-based lattices have not yet been folded due to inherent developability constraints of conventional origami. Here, a novel folding strategy is presented to fold flat sheets into topologically complex cellular materials based on triply periodic minimal surfaces (TPMS), which are attractive geometries for many applications. The approach differs from traditional origami by employing material stretching to accommodate non-developability. Our method leverages the inherent hyperbolic symmetries of TPMS to assemble complex 3D structures from a net of self-foldable patches. We also demonstrate that attaching 3D-printed foldable frames to pre-strained elastomer sheets enables self-folding and self-guided minimal surface shape adaption upon release of the pre-strain. This approach effectively bridges the Euclidean nature of origami with the hyperbolic nature of TPMS, offering novel avenues in the 2D-to-3D fabrication paradigm and the design of architected materials with enhanced functionality.

Contactless laser fabrication and propulsion of freely moving structures

Origami-inspired folding is a well-established method for creating 3D shapes from two dimensional sheets. Here we demonstrate for the first time using a laser to fold, assemble and propel the resulting free-moving part, all without any need for handling. Being able to remotely assemble and move complex parts is an important manufacturing innovation, with potential for controlling doors and latches as well as launching parts off of the build platform without direct assistance. Beginning with only a blank sheet of metal, the parts are first cut and folded using laser forming, where a laser is used to create localized plastic stresses to bend the workpiece. After dropping into place with a final cut, the resulting rotor is actuated with laser ablation propulsion, using a jet of ablated material to apply thrust.

Analysis of foldable acoustic arrays from piecewise linear, conformal, and tessellated topologies

Arrays of acoustic sources distributed over the tessellated frameworks of origami-inspired folding patterns demonstrate exceptional and straightforward adaptivity of acoustic wave guiding architecture to contrast to the challenges manifest in digital wave guiding control methods. Yet, when the concept of folding arrays is applied to tessellations formed by single patterns, acoustic fields with distinct distributions of energy delivery cannot be realized. To overcome this limitation, here multiple folding patterns are assembled by piecewise geometries that permit the array to conform to unique topologies when reconfigured by physical folding actions. An analytical model is developed to predict the acoustic pressure radiated from the acoustic sources arranged on piecewise-continuous surfaces, while experiments are conducted to demonstrate the concept and validate the model. Parametric investigations are then undertaken to uncover the relations of modularity and folding of the acoustic array and the resulting acoustic energy delivery and distributions. The results find that the assembly of tessellated arrays from multiple distinct folding pattern sub-elements may replicate the acoustic wave guiding of complex acoustic sources that traditionally do not enable adaptive wave radiation properties.

An Extensible Continuum Robot With Integrated Origami Parallel Modules

This paper presents a novel design of extensible continuum robots in light of origami-inspired folding techniques. The design starts from a modularized crease pattern, which consists of two triangular bases and three waterbomb bases, and generates a folding process for creating an origami waterbomb parallel structure. This further progresses to generating a compliant module with the origami parallel structure and a helical compression spring. A novel extensible continuum robot with the integrated compliant parallel modules is then proposed to imitate not only the bending motion but also the contraction of continuum creatures in nature. Mapping the origami parallel structure to an equivalent kinematic model, the motion characteristics of the origami structure are explored in terms of kinematic principles. The analysis reveals the mixed rotational and translational motion of the origami parallel module and the virtual axes for yaw and pitch motions. Following kinematics of the proposed continuum robot and features of the integrated helical spring in each module, three actuation schemes and resultant typical working phases with a tendon-driven system are presented. The design and analysis are then followed by a prototype of the extensible continuum robot with six integrated compliant modules connected in serial. The functionality of the proposed continuum robot with the origami parallel structure as its skeleton and the helical springs as the compliant backbone is validated by experimental results.

Hierarchical Kinematic Design of Foldable Hexapedal Locomotion Platforms

Origami-inspired folding enables integrated design and manufacturing of intricate kinematic mechanisms and structures. Here, we present a hierarchical development process of foldable robotic platforms as combinations of fundamental building blocks to achieve arbitrary levels of complexity and functionality. Rooted in theoretical linkage kinematics, designs for static structures and functional units, respectively, offer rigidity and mobility for robotic systems. The proposed approach is demonstrated on the design, fabrication, and experimental verification of three distinct types of hexapedal locomotion platforms covering a broad range of features and use cases.