A planar-sheet nongraphitic zero-bandgap sp carbon phase made by the low-temperature reaction of γ-graphyne.

The highest sheet symmetry form of graphyne, with one triple bond between each neighboring hexagon in graphene, irreversibly transforms exothermically at ambient pressure and low temperatures into a nongraphitic, planar-sheet, zero-bandgap phase consisting of intrasheet-bonded sp carbons. The synthesis of this sp carbon phase is demonstrated, and other carbon phases are described for possible future synthesis from graphyne without breaking graphyne bonds. While measurements and theory indicate that the reacting graphyne becomes nonplanar because of sheet wrinkling produced by dimensional mismatch between reacted and nonreacted sheet regions, sheet planarity is regained when the reaction is complete.

Large stroke radially oriented MXene composite fiber tensile artificial muscles.

Actuation is normally dramatically enhanced by introducing so much yarn fiber twist that the fiber becomes fully coiled. In contrast, we found that usefully high muscle strokes and contractile work capacities can be obtained for non-twisted MXene (TiCT) fibers comprising MXene nanosheets that are stacked in the fiber direction. The MXene fiber artificial muscles are called MFAMs.

Azobenzene-Functionalized Semicrystalline Liquid Crystal Elastomer Springs for Underwater Soft Robotic Actuators.

As actuated devices become smaller and more complex, there is a need for smart materials and structures that directly function as complete mechanical units without an external power supply. The strategy uses light-powered, twisted, and coiled azobenzene-functionalized semicrystalline liquid crystal elastomer (AC-LCE) springs. This twisting and coiling, which has previously been used for only thermally, electrochemically, or absorption-powered muscles, maximizes uniaxial and radial actuation.

Covalent Organic Framework Derived Oxygen/Sulfur-Doped Porous Carbon for Robust High-Capacitance Symmetric Supercapacitors.

Heteroatom-doped porous carbons (HPCs) have been considered promising electrode materials for supercapacitors due to their improvement of energy density by providing extra pseudocapacity. Covalent organic frameworks (COFs) are obtaining great importance in energy storage because of their designable structure and versatile functionality. Herein, we designed and fabricated oxygen and sulfur dual-doped covalent organic framework (COF) derived HPCs with very high heteroatoms content (up to 25.

Advanced Energy Harvesters and Energy Storage for Powering Wearable and Implantable Medical Devices.

Wearable and implantable active medical devices (WIMDs) are transformative solutions for improving healthcare, offering continuous health monitoring, early disease detection, targeted treatments, personalized medicine, and connected health capabilities. Commercialized WIMDs use primary or rechargeable batteries to power their sensing, actuation, stimulation, and communication functions, and periodic battery replacements of implanted active medical devices pose major risks of surgical infections or inconvenience to users. Addressing the energy source challenge is critical for meeting the growing demand of the WIMD market that is reaching valuations in the tens of billions of dollars.

Underwater Thermoacoustic Generation by a Hierarchical Tetrapodal Carbon Nanotube Network.

Solid-state fabricated carbon nanotube (CNT) sheets have shown promise as thermoacoustic (TA) sound generators, emitting tunable sound waves across a broad frequency spectrum (1-10 Hz) due to their ultralow specific heat capacity. However, their applications as underwater TA sound generators are limited by the reduced mechanical strength of CNT sheets in aqueous environments. In this study, we present a mechanically robust underwater TA device constructed from a three-dimensional (3D) tetrapodal assembly of carbon nanotubes (t-CNTs).

Water-induced strong isotropic MXene-bridged graphene sheets for electrochemical energy storage.

Graphene and two-dimensional transition metal carbides and/or nitrides (MXenes) are important materials for making flexible energy storage devices because of their electrical and mechanical properties. It remains a challenge to assemble nanoplatelets of these materials at room temperature into in-plane isotropic, free-standing sheets. Using nanoconfined water-induced basal-plane alignment and covalent and π-π interplatelet bridging, we fabricated TiCT MXene-bridged graphene sheets at room temperature with isotropic in-plane tensile strength of 1.

High-Performance One-Body Electrochemical Torsional Artificial Muscles Built Using Carbon Nanotubes and Ion-Exchange Polymers.

Electrochemical torsional artificial muscles have the potential to replace electric motors in the field of miniaturization. In particular, carbon nanotubes (CNTs) are some of the best materials for electrochemical torsional artificial muscles due to their remarkable mechanical strength and high electrical conductivity. However, previous studies on CNT torsional muscle utilize only half of the whole potential range for torsional actuation because the actuations in the positive and negative voltage ranges offset each other.

Self-Healing E-tongue.

Self-healing materials inspire the next generation of multifunctional wearables and Internet of Things appliances. They expand the realm of thin film fabrication, enabling seamless conformational coverage irrespective of the shape complexity and surface geometry for electronic skins, smart textiles, soft robotics, and energy storage devices. Within this context, the layer-by-layer (LbL) technique is versatile for homogeneously dispersing materials onto various matrices.

Environment-Adaptable Rotational Energy Harvesters Based on Nylon-core Coiled Carbon Nanotube Yarns.

Owing to increasing amount of research on energy harvesting, studies on harvesters for practical application and their performance are attracting attention. Therefore, studies on the use of continuous energy as an energy source for energy-harvesting devices are being conducted, and fluid flows, e.g.

Recent Advances in Carbon Nanotube-Based Energy Harvesting Technologies.

There has been enormous interest in technologies that generate electricity from ambient energy such as solar, thermal, and mechanical energy, due to their potential for providing sustainable solutions to the energy crisis. One driving force behind the search for new energy-harvesting technologies is the desire to power sensor networks and portable devices without batteries, such as self-powered wearable electronics, human health monitoring systems, and implantable wireless sensors. Various energy harvesting technologies have been demonstrated in recent years.

The Stiffest and Strongest Predicted Material: C N Atomic Chains Approach the Theoretical Limits.

Though linear atomic chains exhibit extreme properties, it is presently unclear how these properties can be maximized by the choice of elemental composition. Considering that boron, carbon, and nitrogen can form high modulus and high strength atomic chains, here an algorithm is developed to construct 143 possible atomic chains of these elements with 6 or fewer atoms in the primitive cell and explore their stabilities and mechanical properties by first-principles calculations. It is found that the gravimetric modulus (1032 GPa g cm ) and strength (108 GPa g cm ) of the C N chain significantly exceed those of any known material, including the previously stiffest predicted material (C chain, 945 GPa g cm ) and the previously strongest predicted material (BC chain, 92 GPa g cm ), and also approach the theoretical limits of gravimetric modulus (1036 GPa g cm ) and strength (130 GPa g cm ).

Insect-scale jumping robots enabled by a dynamic buckling cascade.

Millions of years of evolution have allowed animals to develop unusual locomotion capabilities. A striking example is the legless-jumping of click beetles and trap-jaw ants, which jump more than 10 times their body length. Their delicate musculoskeletal system amplifies their muscles' power.

Morphology modulation of artificial muscles by thermodynamic-twist coupling.

Human muscles can grow and change their length with body development; therefore, artificial muscles that modulate their morphology according to changing needs are needed. In this paper, we report a strategy to transform an artificial muscle into a new muscle with a different morphology by thermodynamic-twist coupling, and illustrate its structural evolution during actuation. The muscle length can be continuously modulated over a large temperature range, and actuation occurs by continuously changing the temperature.

More Powerful Twistron Carbon Nanotube Yarn Mechanical Energy Harvesters.

Stretching a coiled carbon nanotube (CNT) yarn can provide large, reversible electrochemical capacitance changes, which convert mechanical energy to electricity. Here, it is shown that the performance of these "twistron" harvesters can be increased by optimizing the alignment of precursor CNT forests, plastically stretching the precursor twisted yarn, applying much higher tensile loads during precoiling twist than for coiling, using electrothermal pulse annealing under tension, and incorporating reduced graphene oxide nanoplates. The peak output power for a 1 and a 30 Hz sinusoidal deformation are 0.

The Power of Fiber Twist.

Nature's evolution over billions of years has led to the development of different kinds of twisted structures in a variety of biological species. Twisted fibers from nanoscale- to micrometer-scale diameter have been prepared by mimicking natural twisted structures. Mechanically inserting twist in a yarn is an efficient and important method, which generates internal stress, changes the macromolecular orientation, and increases compactness.

High-strength scalable graphene sheets by freezing stretch-induced alignment.

Efforts to obtain high-strength graphene sheets by near-room-temperature assembly have been frustrated by the misalignment of graphene layers, which degrades mechanical properties. While in-plane stretching can decrease this misalignment, it reappears when releasing the stretch. Here we use covalent and π-π inter-platelet bridging to permanently freeze stretch-induced alignment of graphene sheets, and thereby increase isotropic in-plane sheet strength to 1.

Unipolar stroke, electroosmotic pump carbon nanotube yarn muscles.

Success in making artificial muscles that are faster and more powerful and that provide larger strokes would expand their applications. Electrochemical carbon nanotube yarn muscles are of special interest because of their relatively high energy conversion efficiencies. However, they are bipolar, meaning that they do not monotonically expand or contract over the available potential range.

Humidity- and Water-Responsive Torsional and Contractile Lotus Fiber Yarn Artificial Muscles.

Materials that dynamically respond to their environment have diverse applications in artificial muscles, soft robotics, and smart textiles. Inspired by biological systems, humidity- and water-responsive actuators that bend, twist, and contract have been previously demonstrated. However, more powerful artificial muscles with large strokes and high work densities are needed, especially those that can be made cost-effectively from eco-friendly materials.

Predicted Confinement-Enhanced Stability and Extraordinary Mechanical Properties for Carbon Nanotube Wrapped Chains of Linear Carbon.

The demand for high-modulus, high-strength, lightweight materials has continuously driven the bottom-up assembly of carbon nanostructures into high-performance bulk carbon materials, such as graphene sheets and carbon nanotube yarns. Carbyne, often called linear carbon, has a higher predicted gravimetric modulus and gravimetric strength than any other form of carbon, but possibly reacts under near-ambient conditions because of the extended hybridization. The successful fabrication of carbon nanotube wrapped single carbyne chain (Shi .