Origami NdFeB Flexible Magnetic Membranes with Enhanced Magnetism and Programmable Sequences of Polarities

Permanent magnets are essential components for many biomedical systems and electromechanical devices, which may be made into flexible formats to achieve wearable monitoring and effective integration with biological tissues. However, the development of high‐performance flexible permanent magnets is challenging due to their ultrathin geometries, which contradict with the thickness‐dependent magnetic properties. In addition, magnetic membranes with controllable sequences of polarities are difficult to achieve. Here, origami techniques to achieve flexible permanent magnetic membranes with enhanced magnetic field strength and programmable sequences of polarities are presented. Linear Halbach arrays, circular Halbach arrays, and concentric magnets with thicknesses ranging from 130 to 500 µm and bending curvatures ranging from 0.039 to 0.0043 µm^?1 are achieved through different folding mechanisms. The origami membranes offer a maximum field intensity of 72 mT and extremely strong magnetic force of 0.21 N cm^?2, allowing various novel applications demonstrated through electronics interfacing, cell manipulations, and soft robotics. The origami techniques offer large magnetism and complex spatial field distribution, and enable practical use of thin flexible magnetic membranes in constructing miniaturized or even flexible electromechanical systems and biomedical instruments for magnetic resonance imaging, targeted drug delivery, health monitoring, and cancer therapy.     

Elastically and Plastically Foldable Electrothermal Micro‐Origami for Controllable and Rapid Shape Morphing

Integrating origami principles within traditional microfabrication methods can produce shape morphing microscale metamaterials and 3D systems with complex geometries and programmable mechanical properties. However, available micro‐origami systems usually have slow folding speeds, provide few active degrees of freedom, rely on environmental stimuli for actuation, and allow for either elastic or plastic folding but not both. This work introduces an integrated fabrication–design–actuation methodology of an electrothermal micro‐origami system that addresses the above‐mentioned challenges. Controllable and localized Joule heating from electrothermal actuator arrays enables rapid, large‐angle, and reversible elastic folding, while overheating can achieve plastic folding to reprogram the static 3D geometry. Because the proposed micro‐origami do not rely on an environmental stimulus for actuation, they can function in different atmospheric environments and perform controllable multi‐degrees‐of‐freedom shape morphing, allowing them to achieve complex motions and advanced functions. Combining the elastic and plastic folding enables these micro‐origami to first fold plastically into a desired geometry and then fold elastically to perform a function or for enhanced shape morphing. The proposed origami systems are suitable for creating medical devices, metamaterials, and microrobots, where rapid folding and enhanced control are desired.     

Graphene‐Based Actuator with Integrated‐Sensing Function

Flexible actuators have important applications in artificial muscles, robotics, optical devices, and so on. However, most of the conventional actuators have only actuation function, lacking in real‐time sensing signal feedbacks. Here, to break the limitation and add functionality in conventional actuators, a graphene‐based actuator with integrated‐sensing function is reported, which avoids the dependence on image post‐processing for actuation detection and realizes real‐time measurement of the shape‐deformation amplitudes of the actuator. The actuator is able to show a large bending actuation (curvature of 1.1 cm^?1) based on a dual‐mode actuation mechanism when it is driven by near infrared light. Meanwhile, the relative resistance change of the actuator is ?17.5%. The sensing function is attributed to piezoresistivity and thermoresistivity of the reduced graphene oxide and paper composite. This actuator can be used as a strain sensor to monitor human motions. A smart gripper based on the actuators demonstrates perfect integration of the actuating and sensing functions, which can not only grasp and release an object, but also sense every actuation state of the actuator. The developed integrated‐sensing actuator is hopeful to open new application fields in soft robotics, artificial muscles, flexible wearable devices, and other integrated‐multifunctional devices.     

Protein‐Based Hydrogels that Actuate Self‐Folding Systems

An approach to build a chemomechatronic system inspired by self‐folding robots is described. This system, which comprises a protein‐based hydrogel bound to a low‐profile laminate, responds to different aqueous environments by undergoing geometric transformations. This response is dependent on the thickness and stiffness of the templating hydrogel, which directly regulates the diffusion of water into and out of the platform to initiate its reversible shape changes. When modified to include more complex geometries, these controllable shape changes can also be used to selectively trigger multiple folding events, illustrating a new platform for chemically initiated mechatronic devices. Together, these data show how compositionally discrete components are physically, chemically, and mechanically coupled together to generate a new actuator for biohybrid self‐folding systems.     

Lightweight Liquid Metal Entity

Liquid metals are of great importance in developing wearable devices and soft robotics owing to its high conductivity and flexibility. However, the high density of such metals turned out to be big concern for many practical situations. With generalized purpose, a new conceptual material as lightweight liquid metal entity, which can be as light as water, is proposed here. For illustration, an unconventionally ultralight material composed of eutectic galliumindium alloys (eGaIn) and glass bubbles is demonstrated, whose density can be reduced below 2.010 even 0.448 g cm^‐3, even lighter than water, but still maintains excellent conformability, electric conductivity, and stiffness variety under temperature regulation. Such material is further adopted to build various complicated structures through origami or force regulation, representing various application scenarios and can be reused for eight times without evident loss in function. Based on these tests, buoyancy component for water‐related devices is designed, which offers the functions of a switch and loading element. The lightweight liquid metal entities are promising for making diverse advanced soft robotics and underwater devices in the near future.     

Cell Generator: A Self‐Sustaining Biohybrid System Based on Energy Harvesting from Engineered Cardiac Microtissues

Biohybrid soft robotic devices present unique advantages for designing biologically active machines that can dynamically sense and interact with complex bioelectrical signals. Here, a controllable cell‐based machine is developed that harvests energy from arrays of beating cardiomyocytes to generate electricity for biomedical microscale robotic applications. The “Cell Generator” device is based on an array of piezoelectric microcantilevers wrapped with 3D patterned cardiac cells. Spontaneous contraction of the engineered cardiac constructs provides the source of mechanical energy for electricity generation. It is demonstrated that a single “Cell Generator” unit with 40 cantilevers can output peak voltages of ≈70 mV, and a larger array of 540 cantilevers can directly generate a pulsed output as high as ≈1 V. When integrated with an electrical rectification and storage circuit, it is further shown that the “Cell Generator” can provide functional outputs and work as a self‐powered neural stimulator to evoke action potentials in cultured neuronal networks. This demonstration of “Cell Generator” technology provides an innovative perspective of exploiting live biological powering system on biomedical microscale robotic devices in the human body.     

Unprecedentedly Tough,Folding‐Endurance,and Multifunctional Graphene‐Based Artificial Nacre with Predesigned 3D Nanofiber Network as Matrix

Mimicking the hierarchical brick‐and‐mortar architecture of natural nacre provides great opportunities for the design and synthesis of multifunctional artificial materials. The crucial challenge to push nacre‐mimetic functional materials toward practical applications is to achieve ample ductility, toughness, and folding endurance with simultaneously maintaining high‐level functional properties. In this study, the microstructure of nacre‐mimetics is reformed through predesigning a 3D nanofiber network to replace conventional polymer matrices. A unique sol–gel–film transformation approach is developed to fabricate a graphene‐based artificial nacre containing a preforming 3D, interconnective, inhomogeneous poly(p‐phenylene benzobisoxazole) nanofiber network. The fabulous coupling of the extensive sliding of graphene nanoplatelets and intensive stretching of the 3D nanofiber network over a large scale enables the artificial nacre to display natural nacre‐like deformation behavior, achieving ultralarge strain‐to‐failure (close to 35%), unprecedented toughness (close to 50 MJ m^?3), and fold endurance (no decrease in tensile properties after folding for 10 000 times or folding at increasing stress). The new levels of ductility, toughness, and folding endurance are integrated with outstanding thermal properties, including thermal conductivity (≈130 W m^?1 K^?1), thermal stability (520 °C) and nonflammability, rendering the lightweight nacre‐mimetics promising in flexible electronic devices, particularly for aerospace electronics.     

Ultralarge Contraction Directed by Light‐Driven Unlocking of Prestored Strain Energy in Linear Liquid Crystal Polymer Fibers

Anisotropic 1D contraction motion of polymeric actuating materials has drawn growing interests in fields ranging from soft robotics to biomimetic muscles. Although light‐driven liquid crystal polymers (LCPs) represent promising candidates to realize contraction (<20%) triggered remotely and spatially, there remain multitudes of challenges to develop an LCP system possessing ultralarge contraction rate. Here, a novel strategy combining shape memory effect and photochemical phase transition is presented to realize light‐driven contraction as large as 81% in a newly designed linear liquid crystal copolymer, where the eutectic mesogens of azobenzene and phenyl benzoate self‐organize into the smectic B phase. Importantly, this highly ordered structure as the switching segment firmly locks the stress‐induced strain energy, which is rapidly released by reversible trans–cis photoisomerization that destroys the lamellar liquid crystal phase, therefore leading to such ultralarge contraction. Fibers serve as light‐driven building blocks to achieve precise origami, to mimic the recovery of a “broken” spider web and to screen objects in different sizes, laying new ground for advanced applications of light‐driven LCPs from biomimetic robots to human assists.     

Liquid Metal Based Island‐Bridge Architectures for All Printed Stretchable Electrochemical Devices

The adoption of epidermal electronics into everyday life requires new design and fabrication paradigms, transitioning away from traditional rigid, bulky electronics towards soft devices that adapt with high intimacy to the human body. Here, a new strategy is reported for fabricating achieving highly stretchable “island‐bridge” (IB) electrochemical devices based on thick‐film printing process involving merging the deterministic IB architecture with stress‐enduring composite silver (Ag) inks based on eutectic gallium‐indium particles (EGaInPs) as dynamic electrical anchors within the inside the percolated network. The fabrication of free‐standing soft Ag‐EGaInPs‐based serpentine “bridges” enables the printed microstructures to maintain mechanical and electrical properties under an extreme (≈800%) strain. Coupling these highly stretchable “bridges” with rigid multifunctional “island” electrodes allows the realization of electrochemical devices that can sustain high mechanical deformation while displaying an extremely attractive and stable electrochemical performance. The advantages and practical utility of the new printed Ag‐liquid metal‐based island‐bridge designs are discussed and illustrated using a wearable biofuel cell. Such new scalable and tunable fabrication strategy will allow to incorporate a wide range of materials into a single device towards a wide range of applications in wearable electronics.     

Versatile Electronic Skins for Motion Detection of Joints Enabled by Aligned Few‐Walled Carbon Nanotubes in Flexible Polymer Composites

Here, novel multifunctional electronic skins (E‐skins) based on aligned few‐walled carbon nanotube (AFWCNT) polymer composites with a piezoresistive functioning mechanism different from the mostly investigated theory of “tunneling current channels” in randomly dispersed CNT polymer composites are demonstrated. The high performances of as‐prepared E‐skins originate from the anisotropic conductivity of AFWCNT array embedded in flexible composite and the distinct variation of “tube‐to‐tube” interfacial resistance responsive to bending or stretching. The polymer/AFWCNT‐based flexion‐sensitive E‐skins exhibit high precision and linearity, together with low power consumption (<10 µW) and good stability (no degradation after 15 000 bending–unbending cycles). Moreover, polymer/AFWCNT composites can also be used for the construction of tensile‐sensitive E‐skins, which exhibit high sensitivity toward tensile force. The polymer/AFWCNT‐based E‐skins show remarkable performances when applied to monitor the motions and postures of body joints (such as fingers), a capability that can find wide applications in wearable human–machine communication interfaces, portable motion detectors, and bionic robots.     

Molecular Engineering of “Click”‐Phospholes Towards Self‐Assembled Luminescent Soft Materials

Inspired by the self‐assembled bilayer structures of natural amphiphilic phospholipids, a new class of highly luminescent “click”‐phospholes with exocyclic alkynyl group at the phosphorus center is reported. These molecules can be easily functionalized with a self‐assembly group to generate neutral “phosphole‐lipids”. This novel approach retains the versatile reactivity of the phosphorus center, allowing further engineering of the photophysical and self‐assembly properties of the materials at a molecular level. The results of this study highlight the importance of being able to balance weak intermolecular interactions for controlling the self‐assembly properties of soft materials. Only molecules with the appropriate set of intermolecular arrangement/interactions show both organogel and liquid crystal mesophases with well‐ordered microstructures. Moreover, an efficient energy transfer of the luminescent materials is demonstrated and applied in the detection of organic solvent vapors.     

A Flexible 3D Multifunctional MgO‐Decorated Carbon Foam@CNTs Hybrid as Self‐Supported Cathode for High‐Performance Lithium‐Sulfur Batteries

One of the critical challenges to develop advanced lithium‐sulfur (Li‐S) batteries lies in exploring a high efficient stable sulfur cathode with robust conductive framework and high sulfur loading. Herein, a 3D flexible multifunctional hybrid is rationally constructed consisting of nitrogen‐doped carbon foam@CNTs decorated with ultrafine MgO nanoparticles for the use as advanced current collector. The dense carbon nanotubes uniformly wrapped on the carbon foam skeletons enhance the flexibility and build an interconnected conductive network for rapid ionic/electronic transport. In particular, a synergistic action of MgO nanoparticles and in situ N‐doping significantly suppresses the shuttling effect via enhanced chemisorption of lithium polysulfides. Owing to these merits, the as‐built electrode with an ultrahigh sulfur loading of 14.4 mg cm^?2 manifests a high initial areal capacity of 10.4 mAh cm^?2, still retains 8.8 mAh cm^?2 (612 mAh g^?1 in gravimetric capacity) over 50 cycles. The best cycling performance is achieved upon 800 cycles with an extremely low decay rate of 0.06% at 2 C. Furthermore, a flexible soft‐packaged Li‐S battery is readily assembled, which highlights stable electrochemical characteristics under bending and even folding. This cathode structural design may open up a potential avenue for practical application of high‐sulfur‐loading Li‐S batteries toward flexible energy‐storage devices.     

Electrically and Sunlight‐Driven Actuator with Versatile Biomimetic Motions Based on Rolled Carbon Nanotube Bilayer Composite

Designing multistimuli responsive soft actuators which can mimic advanced and sophisticated biological movements through simple configuration is highly demanded for the biomimetic robotics application. Here, inspired by the human's flick finger behavior which can release large force output, a soft jumping robot mimicking the gymnast's somersault is designed based on the rolled carbon nanotube/polymer bilayer composite actuator. This new type of rolled bilayer actuator with tubular shape is fabricated and shows electrically and sunlight‐induced actuation with remarkable performances including ultralarge deformation from tubular to flat (angel change >200° or curvature >2 cm^?1), fast response (<5 s), and low actuation voltage (≤10 V). Besides jumping, the uniquely reversible rolling–unrolling actuation can lead to other smart soft robots with versatile complex biomimetic motions, including light‐induced tumbler with cyclic wobbling, electrically/light‐induced crawling‐type walking robots and grippers, electrically induced mouth movement, and ambient‐sunlight‐induced blooming of a biomimetic flower. These results open the way for using one simple type of actuator structure for the construction of various soft robots and devices toward practical biomimetic applications.     

An Autonomous Soft Actuator with Light‐Driven Self‐Sustained Wavelike Oscillation for Phototactic Self‐Locomotion and Power Generation

Mimicking the intelligence of biological organisms in artificial systems to design smart actuators that act autonomously in response to constant environmental stimuli is crucial to the construction of intelligent biomimetic robots and devices, but remains a great challenge. Here, a light‐driven autonomous carbon‐nanotube‐based bimorph actuator is developed through an elaborate structural design. This curled droplet‐shaped actuator can be simply driven by constant white light irradiation, self‐propelled by a light‐mechanical negative feedback loop created by light‐driven actuation, time delay in the photothermal response along the actuator, and good elasticity from the curled structure, performing a continuously self‐oscillating motion in a wavelike fashion, which mimics the human sit‐up motion. Moreover, this autonomous self‐oscillating motion can be further tuned by controlling the intensity and direction of the incident light. The autonomous actuator with continuous wavelike oscillating motion shows immense potential in light‐driven biomimetic soft robots and optical‐energy‐harvesting devices. Furthermore, a self‐locomotive artificial snake with phototaxis is constructed, which autonomously and continuously crawls toward the light source in a wave‐propagating manner under constant light irradiation. This snake can be placed on a substrate made of triboelectric materials to realize continuous electric output when exposed to constant light illumination.     

Kirigami‐Inspired Self‐Assembly of 3D Structures

Self‐assembly of 3D structures presents an attractive and scalable route to realize reconfigurable and functionally capable mesoscale devices without human intervention. A common approach for achieving this is to utilize stimuli‐responsive folding of hinged structures, which requires the integration of different materials and/or geometric arrangements along the hinges. It is demonstrated that the inclusion of Kirigami cuts in planar, hingeless bilayer thin sheets can be used to produce complex 3D shapes in an on‐demand manner. Nonlinear finite element models are developed to elucidate the mechanics of shape morphing in bilayer thin sheets and verify the predictions through swelling experiments of planar, millimeter‐scaled PDMS (polydimethylsiloxane) bilayers in organic solvents. Building upon the mechanistic understandings, The transformation of Kirigami‐cut simple bilayers into 3D shapes such as letters from the Roman alphabet (to make “ADVANCED FUNCTIONAL MATERIALS”) and open/closed polyhedral architectures is experimentally demonstrated. A possible application of the bilayers as tether‐less optical metamaterials with dynamically tunable light transmission and reflection behaviors is also shown. As the proposed mechanistic design principles could be applied to a variety of materials, this research broadly contributes toward the development of smart, tetherless, and reconfigurable multifunctional systems.     

Active Reconfigurable Tristable Square‐Twist Origami

Origami structures offer valuable applications in many fields, ranging from metamaterials to robotics. The multistable characteristics of origami structures have been pursued for acquiring unique reconfigurable features. For achieving this goal, an unusual polymeric tristable origami structure is demonstrated using a classic square‐twist origami configuration. By manipulating both material properties and geometric parameters of the heteropolymer structures, a design principle for tailoring the multistable configuration in the square‐twist origami is established based on variation of the structural potential energy. Under thermal triggering, the stiffness of the deformable structure is dramatically reduced, which causes an increase in the structural degree of freedom, allowing for self‐deployment via release of the prestored energy in the elastic twisted hinges. Utilizing such unique features and design principles, a prototype of frequency reconfigurable origami antenna of five diverse operating modes and a programmable multiple‐input multiple‐output communication system is subsequently designed and assembled, aiming to substantially promote the channel capacity and communication reliability. The findings and results firmly provide a remarkable design principle and strategy for advancing active origami structures and devices in shape‐morphing systems.     

Integrated Biomonitoring Sensing with Wearable Asymmetric Supercapacitors Based on Ti3C2 MXene and 1T‐Phase WS2 Nanosheets

Research on wearable sensing technologies has been gaining considerable attention in the development of portable bio‐monitoring devices for personal health. However, traditional energy storage systems with defined size and shape have inherent limitations in satisfying the performance requirements for flexible electronics. To overcome this constraint, three different configurations of flexible asymmetric supercapacitor (FASC) are fabricated on polyester/cellulose blend (PCB) cloth substrate using Ti₃C₂ nanosheet (NS) and 1T WS₂ NS as electrodes, and aqueous pluronic gel as an electrolyte. Benefiting from the 2D material electrodes, the interdigitated FASC configuration exhibits excellent performance, flexibility, cyclic stability, wearability and can be configured into multiple units and shapes, which far exceed that exhibited by the textile‐based FASC. Furthermore, the arbitrary (“AFN”) and sandwich (“FLOWER”) configurations Ti₃C₂ NS/1T WS₂ NS FASC can be assembled directly on a PCB cloth substrate, thereby offering good structural integrity coupled with ease of assembly into integrated circuits of different shapes. More specifically, a lightweight, flexible, and wearable bio‐monitoring system is developed by integrating force sensing device with interdigitated FASC, which can be used to monitor the physical status of human body during various activities. A potential application of this system in healthcare is successfully demonstrated and discussed.     

Design of an “Active Defense” System as Drug Carriers for Cancer Therapy

A novel intelligent “active defense” system that can specially respond to cancerous tissues for drug release was designed and prepared. The “active defense” system consists of a biodegradable dextran microgel core cross‐linked by a Schiff's base and a surrounding layer formed by Layer‐by‐Layer (LbL) assembly. The loading and release of macromolecular model drug, dex‐FITC, as well as antineoplastic drug, DOX, was investigated. The in vitro cell inhibition and drug release behavior of the drug delivery system were studied and the results showed that the entrapped drug could be explosively released from the microcapsules and thereafter taken up by cancer cells upon the trigger of the acidic environment around tumor tissues.     

Controlled Mechanical Buckling for Origami‐Inspired Construction of 3D Microstructures in Advanced Materials

Origami is a topic of rapidly growing interest in both the scientific and engineering research communities due to its promising potential in a broad range of applications. Previous assembly approaches for origami structures at the micro/nanoscale are constrained by the applicable classes of materials, topologies, and/or capability for reversible control over the transformation process. Here, a strategy is introduced that exploits mechanical buckling for autonomic origami assembly of 3D structures across material classes from soft polymers to brittle inorganic semiconductors, and length scales from nanometers to centimeters. This approach relies on a spatial variation of thickness in the initial 2D structures as a means to produce engineered folding creases during the compressive buckling process. The elastic nature of the assembly scheme enables active, deterministic control over intermediate states in the 2D to 3D transformation in a continuous and reversible manner. Demonstrations include a broad set of 3D structures formed through unidirectional, bidirectional, and even hierarchical folding, with examples ranging from half cylindrical columns and fish scales, to cubic boxes, pyramids, starfish, paper fans, skew tooth structures, and to amusing system‐level examples of soccer balls, model houses, cars, and multifloor textured buildings.