Exciting advancements have been made in the field of flexible electronic devices in the last two decades and will certainly lead to a revolution in peoples’ lives in the future. However, because of the poor sustainability of the active materials in complex stress environments, new requirements have been adopted for the construction of flexible devices. Thus, hierarchical architectures in natural materials, which have developed various environment-adapted structures and materials through natural selection, can serve as guides to solve the limitations of materials and engineering techniques. This review covers the smart designs of structural materials inspired by natural materials and their utility in the construction of flexible devices. First, we summarize structural materials that accommodate mechanical deformations, which is the fundamental requirement for flexible devices to work properly in complex environments. Second, we discuss the functionalities of flexible devices induced by nature-inspired stru...

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Nature-Inspired Structural Materials for Flexible Electronic Devices

Origami robots are created using folding processes, which provide a simple approach to fabricating a wide range of robot morphologies. Inspired by biological systems, engineers have started to explore origami folding in combination with smart material actuators to enable intrinsic actuation as a means to decouple design from fabrication complexity. The built-in crease structure of origami bodies has the potential to yield compliance and exhibit many soft body properties. Conventional fabrication of robots is generally a bottom-up assembly process with multiple low-level steps for creating subsystems that include manual operations and often multiple iterations. By contrast, natural systems achieve elegant designs and complex functionalities using top-down parallel transformation approaches such as folding. Folding in nature creates a wide spectrum of complex morpho-functional structures such as proteins and intestines and enables the development of structures such as flowers, leaves and insect wings. Inspired by nature, engineers have started to explore folding powered by embedded smart material actuators to create origami robots. The design and fabrication of origami robots exploits top-down, parallel transformation approaches to achieve elegant designs and complex functionalities. In this Review, we first introduce the concept of origami robotics and then highlight advances in design principles, fabrication methods, actuation, smart materials and control algorithms. Applications of origami robots for a variety of devices are investigated, and future directions of the field are discussed, examining both challenges and opportunities. Inspired by biological systems, engineers are exploring origami folding with smart material actuation to enable intrinsically actuated designs with complex functionalities and easy fabrication. This Review highlights recent advances in the design, fabrication and control of these origami robots.

Design, fabrication and control of origami robots

Origami enables folding of objects into a variety of shapes in arts, engineering, and biological systems. In contrast to well-known paper-folded objects, the wing of the earwig has an exquisite natural folding system that cannot be sufficiently described by current origami models. Such an unusual biological system displays incompatible folding patterns, remains open by a bistable locking mechanism during flight, and self-folds rapidly without muscular actuation. We show that these notable functionalities arise from the protein-rich joints of the earwig wing, which work as extensional and rotational springs between facets. Inspired by this biological wing, we establish a spring origami model that broadens the folding design space of traditional origami and allows for the fabrication of precisely tunable, four-dimensional–printed objects with programmable bioinspired morphing functionalities.

http://science.sciencemag.org/content/sci/359/6382/1386.full.pdf

Bioinspired spring origami

Origami, the ancient Japanese art of paper folding, is not only an inspiring technique to create sophisticated shapes, but also a surprisingly powerful method to induce nonlinear mechanical properties. Over the last decade, advances in crease design, mechanics modeling, and scalable fabrication have fostered the rapid emergence of architected origami materials. These materials typically consist of folded origami sheets or modules with intricate 3D geometries, and feature many unique and desirable material properties like auxetics, tunable nonlinear stiffness, multistability, and impact absorption. Rich designs in origami offer great freedom to design the performance of such origami materials, and folding offers a unique opportunity to efficiently fabricate these materials at vastly different sizes. Here, recent studies on the different aspects of origami materials-geometric design, mechanics analysis, achieved properties, and fabrication techniques-are highlighted and the challenges ahead discussed. The synergies between these different aspects will continue to mature and flourish this promising field.

https://par.nsf.gov/servlets/purl/10197964

Architected Origami Materials: How Folding Creates Sophisticated Mechanical Properties.

DOI: 10.1002/admi.201800284 expand the range of accessible 3D geometries.[5–8] Due to their shape-adaptive nature, origami and kirigami, originally applied only to paper, can serve as routes to large-scale structural systems that require packaging and deployment, such as foldable solar panels,[9,10] retractable roofs,[11] deployable sunshields,[12] and many others.[13] More recent work demonstrates that these and related methods for assembling planar materials into complex 3D structures can exploit sophisticated 2D fabrication technologies and thin film materials from the electronics/optoelectronics industries, to yield functional systems in 3D designs that were previously unachievable.[14–18] In this way, the techniques of origami/kirigami can enable many classes of nontraditional devices not only at the macroscale but also at the micro/ nanoscale, with the potential to open up opportunities for unusual engineering designs in microsystems technologies.[19–22] Much research in origami/kirigami assembly aims to extend the range of length scales and the scope of functional materials that can be realized in 3D systems, and to transfer those ideas and Origami and kirigami, the ancient techniques for making paper works of art, also provide inspiration for routes to structural platforms in engineering applications, including foldable solar panels, retractable roofs, deployable sunshields, and many others. Recent work demonstrates the utility of the methods of origami/kirigami and conceptually related schemes in cutting, folding, and buckling in the construction of devices for emerging classes of technologies, with examples in mechanical/optical metamaterials, stretchable/ conformable electronics, micro/nanoscale biosensors, and large-amplitude actuators. Specific notable progress is in the deployment of functional materials such as single-crystal silicon, shape memory polymers, energy-storage materials, and graphene into elaborate 3D micro and nanoscale architectures. This review highlights some of the most important developments in this field, with a focus on routes to assembly that apply across a range of length scales and with advanced materials of relevance to practical applications. Hall of Fame Article

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Assembly of Advanced Materials into 3D Functional Structures by Methods Inspired by Origami and Kirigami: A Review

This is an overview of current research in origami applied to mechanical engineering. Fundamental concepts and definitions commonly used in origami are introduced, including a background on key mat...

https://journals.sagepub.com/doi/pdf/10.1177/0954406215597713

Nicholas Turner

Papers

A review of origami applications in mechanical engineering