Yarn Muscles Research Articles

Direct Catalysis‐Driven Yarn Artificial Muscles: Chemically Induced Actuation

AbstractYarn artificial muscles offer an exciting avenue to replicate the extraordinary efficiency of biological muscles, converting chemical energy directly into mechanical work. Nevertheless, realizing the chemical‐mechanical energy conversion has posed significant challenges. In this study, a novel approach for harnessing direct catalysis to power yarn artificial muscles within a one‐compartment aqueous system is introduced. This research distinguishes itself through an innovative actuation mechanism using nanoscale catalytic particles. These nanoparticles synthesized and integrated onto the yarn surface act as a chemical trigger for muscle actuation. Notably, the resulting yarn muscle demonstrates a reversible tensile stroke of nearly 4% in ≈20 s. By bridging the gap between chemical catalysis and mechanical performance, this study paves the way for innovative applications in fields ranging from robotics to biomedical devices.

Dual-Responsive MXene-Functionalized Wool Yarn Artificial Muscles.

Fiber-based artificial muscles are promising for smart textiles capable of sensing, interacting, and adapting to environmental stimuli. However, the application of current artificial muscle-based textiles in wearable and engineering fields has largely remained a constraint due to the limited deformation, restrictive stimulation, and uncomfortable. Here, dual-responsive yarn muscles with high contractile actuation force are fabricated by incorporating a very small fraction (<1wt.%) of Ti3C2Tx MXene/cellulose nanofibers (CNF) composites into self-plied and twisted wool yarns. They can lift and lower a load exceeding 3400 times their own weight when stimulated by moisture and photothermal. Furthermore, the yarn muscles are coiled homochirally or heterochirally to produce spring-like muscles, which generated over 550% elongation or 83% contraction under the photothermal stimulation. The actuation mechanism, involving photothermal/moisture-mechanical energy conversion, is clarified by a combination of experiments and finite element simulations. Specifically, MXene/CNF composites serve as both photothermal and hygroscopic agents to accelerate water evaporation under near-infrared (NIR) light and moisture absorption from ambient air. Due to their low-cost facile fabrication, large scalable dimensions, and robust strength coupled with dual responsiveness, these soft actuators are attractive for intelligent textiles and devices such as self-adaptive textiles, soft robotics, and wearable information encryption.

Knittable Electrochemical Yarn Muscle for Morphing Textiles.

Morphing textiles, crafted using electrochemical artificial muscle yarns, boast features such as adaptive structural flexibility, programmable control, low operating voltage, and minimal thermal effect. However, the progression of these textiles is still impeded by the challenges in the continuous production of these yarn muscles and the necessity for proper structure designs that bypass operation in extensive electrolyte environments. Herein, a meters-long sheath-core structured carbon nanotube (CNT)/nylon composite yarn muscle is continuously prepared. The nylon core not only reduces the consumption of CNTs but also amplifies the surface area for interaction between the CNT yarn and the electrolyte, leading to an enhanced effective actuation volume. When driven electrochemically, the CNT@nylon yarn muscle demonstrates a maximum contractile stroke of 26.4%, a maximum contractile rate of 15.8% s-1, and a maximum power density of 0.37 W g-1, surpassing pure CNT yarn muscles by 1.59, 1.82, and 5.5 times, respectively. By knitting the electrochemical CNT@nylon artificial muscle yarns into a soft fabric that serves as both a soft scaffold and an electrolyte container, we achieved a morphing textile is achieved. This textile can perform programmable multiple motion modes in air such as contraction and sectional bending.

Carbon nanotube yarn with small outer diameter to maximize the electrochemical performance of artificial muscles

Electrochemically powered carbon nanotube (CNT) artificial muscles have garnered significant attention owing to their chemical stability, low operating voltage, and impressive actuation performance. Notably, twist-based CNT artificial muscles have demonstrated superior actuation performance by maximizing untwisting motion of the CNT yarn. However, the microscopic design of CNTs is yet to be reported, although CNTs comprising CNT yarn muscles are key determinants of performance. Here, we first establish a correlation between the diameter of CNTs and the actuation performance of artificial muscles. The structural reason for the higher deformability is elucidated employing molecular dynamics simulations. The obtained computational simulation results were consistent with the experimentally fabricated yarn. Remarkably, the CNT yarn muscle composed of small-diameter CNTs exhibited a work capacity of 3.57 J/g, significantly higher than previously reported ones. Our findings provide a fundamental design range of CNT diameters that can significantly enhance the performance of electrochemically powered artificial muscles.

Synergistic actuation performance of artificial fern muscle with a double nanocarbon structure

Electrochemically powered carbon nanotube (CNT) yarn muscles are of increasing interest because of their advantageous features as artificial muscles. They are light, and have high electrical properties, mechanical strength, and chemical stability. Twist-based CNT yarn muscles show superior actuation performance: 30 times the work capacity and 85 times the power density of natural muscles. Despite achieving these high performances, there is still potential for performance improvement because their twisted structure is not fully utilized. In particular, designing a cross-sectional structure that allows ions to freely enter and exit the twisted structure of the yarn muscle is necessary. Here, we propose highly enhanced artificial muscles with high chemical stability that consist of only nanocarbon materials of carbon nanoscroll (CNS) and twisted CNT yarns. The CNS/CNT yarn muscles (CCYM) can improve the ion accessibility and utilization of the twist structure. The maximum contractile stroke, work capacity, power density, and energy conversion efficiency of the CCYM were 20.11%, 2.26 J g−1, 0.53 W g−1, and 3.39%, which are 1.4-, 1.4-, 4.8, and 4.3 times that of the pristine CNT yarn muscles, respectively. The effects of CNS on CCYM were confirmed by experimental and theoretical analyses. Additionally, in a solid electrolyte, which opens up new application possibilities, the CCYM demonstrates high actuation performance (16.38%) with very low input energy.

Fast and Strong Carbon Nanotube Yarn Artificial Muscles by Electro-osmotic Pump.

Previous electrochemically powered yarn muscles cannot be usefully operated between extreme negative and extreme positive potentials, since generated stresses during anion injection and cation injection partially cancel because they are in the same direction. We here report an ionomer-infiltrated hybrid carbon nanotube (CNT) yarn muscle that shows unipolar stress behavior in the sense that stress generation between extreme potentials is additive, resulting in an enhanced stress generation. Moreover, the stress generated by this muscle unexpectedly increases with the potential scan rate, which contradicts the fact that scan-rate-induced stress decreases for neat CNT muscles. It is revealed by the electro-osmotic pump effect that the effective ion size injected into the muscle increases with an increase in the scan rate. We demonstrate an electrochemically powered gel-elastomer-yarn muscle adhesive that generates and delivers muscle-contraction-mimicking stimulation to a target tissue.

Ultrawide-color-gamut single-pixel dynamic color manipulation based on yarn muscles–graphene MEMS

Herein, the single-pixel color modulation in a composite structure based on a yarn muscles–graphene mechanical system and photonic crystal multimode microcavity is investigated. The position of graphene in the microcavity is changed by varying the stretching of yarn muscles using different current levels. This aids in adjusting the light absorption of graphene to different colors. Hence, red, green, blue, and their mixed colors can be displayed using a single pixel; moreover, the color gamut of this system can reach 96.5% of sRGB space. The proposed system can avoid the spontaneous oscillation caused by large strain energy. This solution can provide insights into the design of low-power, ultrahigh-resolution, and ultrawide-color-gamut interferometric modulator display technologies.

Dual-Ion Co-Regulation System Enabling High-Performance Electrochemical Artificial Yarn Muscles with Energy-Free Catch States

HighlightsThe dual-ion co-regulation system shortens ion migration pathways, which endow the yarn muscle with high contractile stroke (34.7%) and contractile rate (9.4% s−1), more than twice that of the “rocking-chair” -type ion migration yarn muscles.The yarn muscle shows high isometric stress of 18.4 MPa (61 times that of skeletal muscles) and 8 times the isometric stress of the “rocking-chair” -type yarn muscles at a higher frequency.The intercalation reaction between {text{PF}}_{6}^{ - }and collapsed carbon nanotubes allows the yarn muscle to achieve an energy-free high-tension catch state

Wet-Driven Bionic Actuators from Wool Artificial Yarn Muscles.

Nature-similar muscle is one of the ultimate goals of advanced artificial muscle materials. Currently, a variety of chemical and natural materials have been gradually developed for the preparation of artificial muscles. However, due to the scarcity, biological exclusion, and poor flexibility of the abovementioned materials, it is still a challenging process to maximize the imitation of behaviors shown by real muscles and commercial development. Here, this article presents multidimensional wool yarn artificial muscles, and the wet response behavior of fibers is induced in yarn muscles successfully by virtue of weakening the water-repellent effect of wool scales. Wool artificial muscles are cost-effective and widely available and have good biocompatibility. In addition, wool fiber assemblies are structurally stable, soft, and flexible to be processed into artificial muscles with torsional, contractile, and even multilayered structures, enabling various wet-driven behaviors. On the basis of the theoretical model and numerical simulation, we explained and verified the working mechanism employed in wool artificial yarn muscles. Finally, the yarn muscle was integrated into a wool muscle group through the textile technology, followed by the application to robot bionic arms, displaying the great potential of wool artificial yarn muscles in bionic drivers and the intelligent textile industry.

Linear contracting and air-stable electrochemical artificial muscles based on commercially available CNT yarns and ionically selective ionogel coatings

Artificial muscles, or soft actuators, that could exhibit contractile stroke and operate in open-air, would be crucial for many applications, such as robotics, prosthetics, or powered exoskeletons. Amongst the different artificial muscle technologies, electrochemical carbon nanotube (CNT) yarn muscles, transducing capacitively ionic accumulation at the electrochemical double layer into linear contraction, are amongst the most promising candidates. However, their performances are either limited by an undesired bipolar behaviour or short lifetime due to the inevitable drying of water-based electrolytes. In this paper, we present here the fabrication of air-operating contractile linear artificial muscles from commercially available CNT yarns exhibiting outstanding performance. The synthesis and the junction of two ionogels based on cationic and anionic polyelectrolyte have been designed for the coating process on CNT yarns, and for selectively orienting the ionic flow allowing optimal electromechanical energy conversion. The dual-electrode CNT yarn actuators showed air-stable unipolar contractile stroke, reaching 9.7% without loss of performances after 2000 cycles.

Self-Aware Artificial Coiled Yarn Muscles with Enhanced Electrical Conductivity and Durability via a Two-Step Process.

Muscles are capable of modulating the body and adapting to environmental changes with a highly integrated sensing and actuation. Inspired by biological muscles, coiled/twisted fibers are adopted that can convert volume expansion into axial contraction and offer the advantages of flexibility and light weight. However, the sensing-actuation integrated fish line/yarn-based artificial muscles are still barely reported due to the poor actuation-sensing interface with off-the-shelf fibers. We report herein artificial coiled yarn muscles with self-sensing and actuation functions using the commercially available yarns. Via a two-step process, the artificial coiled yarn muscles are proved to obtain enhanced electrical conductivity and durability, which facilitates the long-term application in human-robot interfaces. The resistivity is successfully reduced from 172.39 Ω·cm (first step) to 1.27 Ω·cm (second step). The multimode sense of stretch strain, pressure, and actuation-sensing are analyzed and proved to have good linearity, stability and durability. The muscles could achieve a sensitivity (gauge factor, GF) of the contraction strain perception up to 1.5. We further demonstrate this self-aware artificial coiled yarn muscles could empower non-active objects with actuation and real-time monitoring capabilities without causing damage to the objects. Overall, this work provides a facile and versatile tool in improving the actuation-sensing performances of the artificial coiled yarn muscles and has the potential in building smart and interactive soft actuation systems.

Moisture-Sensitive Response and High-Reliable Cycle Recovery Effectiveness of Yarn-Based Actuators with Tether-Free, Multi-Hierarchical Hybrid Construction.

Yarn-based muscle actuators are highly desired for applications in soft robotics, flexible sensors, and other related applications due to their actuation properties. Although the tethering avoiding release of inserted twist, the complex preparation process and harsh experimental conditions make tether-free structures yarn actuator with reliable cycle recovery effectiveness is needed. Herein, a tether-free, multi-hierarchical hybrid construction of a moisture-sensitive responsive yarn-based actuator with the viscose/PET ratio (VPR) = 0.9 exhibited a contraction stroke of 83.15%, a work capacity of 52.98 J·kg-1, and an exerting force of 0.15 MPa. Additionally, the maximum cycle recovery rate of 99% is comparable to that of human skeletal muscles, confirming the advantages of a two-component hybrid structure. The underlying mechanism is discussed based on geometric characterization and energy conversion analysis between the actuation source and the spring frame. The mechanical manufacturing process makes it simple to expand the structurally stable yarn muscles into fabric muscles, opening up new opportunities to advance the usage of yarn-based actuators in smart textiles, medical materials, intelligent plants, and other versatile fields.

High-performance carbon nanotube/polyaniline artificial yarn muscles working in biocompatible environments

High-performance carbon nanotube/polyaniline artificial yarn muscles working in biocompatible environments

Stepwise Artificial Yarn Muscles with Energy-Free Catch States Driven by Aluminum-Ion Insertion.

Present artificial muscles have been suffering from poor actuation step precision and the need of energy input to maintain actuated states due to weak interactions between guest and host materials or the unstable structural changes. Herein, these challenges are addressed by deploying a mechanism of reversible faradaic insertion and extraction reactions between tetrachloroaluminate ions and collapsed carbon nanotubes. This mechanism allows tetrachloroaluminate ions as a strong but dynamic "locker" to achieve an energy-free high-tension catch state and programmable stepwise actuation in the yarn muscle. When powered off, the muscle nearly 100% maintained any achieved contractile strokes even under loads up to 96,000 times the muscle weight. The actuation mechanism allowed the programmable control of stroke steps down to 1% during reversible actuation. The isometric stress generated by the yarn muscle (14.6 MPa in maximum, 40 times that of skeletal muscles) was also energy freely lockable and step controllable with high precision. Importantly, when fully charged, the muscle stored energy with a high capacity of 102 mAh g-1, allowing the muscle as a battery to power secondary muscles or other devices.

Free-standing single-helical woolen yarn artificial muscles with robust and trainable humidity-sensing actuation by eco-friendly treatment strategies

Twisted yarn artificial muscles have attracted great interests for diverse applications, such as soft robotics, miniaturization controllers and smart textiles. A challenging issue in fabricating the twisted yarn artificial muscles is to retain the inserted twist. Different from the exiting strategies of forming double-helical structures or harnessing complex chemical technologies, we herein propose a simple combination of plasma and UV-light treatments to train natural wools into twist-stable single-helical yarn artificial muscles without external torsional tethering, which realizes easy fabrication of twisted actuators, and achieves better moisture-actuating performance (nearly five times higher in maximum rotation) compared to equivalent double-helical actuators. The stable morphology of woolen yarn muscles affected by the opening and closing of disulfide bonds is explained from microstructure characterization and theoretical analysis. The charming properties of single-helical yarn muscles will provide new inspiration for the development of fiber-based actuators in industrial routines, which is expected to promote the practical application of yarn muscles in smart textiles and wider fields.

Fast Large‐Stroke Sheath‐Driven Electrothermal Artificial Muscles with High Power Densities

AbstractElectrothermal carbon nanotube (CNT) yarn muscles can provide large strokes during thermal cycling. However, the slow cooling rate of thermal muscles limits their applications, since large diameter prior‐art thermal muscles cannot be rapidly cycled. Herein, a fast thermally powered sheath‐driven yarn muscle that uses a hybrid CNT sheath and an inexpensive polymer core, is reported. The stroke recovery rate for the hybrid muscle is much lower at all frequencies than for about the same diameter sheath‐driven muscle, which means that the full cycle contractile mechanical power is much higher than for comparable prior‐art hybrid muscle. More specifically, the coiled sheath‐driven muscle contracts 14.3% at 1 Hz and 7.3% at 8 Hz in air when powered by a square‐wave electrical voltage input, which is 2.9‐ and 11.4‐times the stroke of the coiled hybrid muscle at these respective frequencies. An average power density of 12 kW kg−1 is obtained for a sheath‐driven muscle, which is 42‐times that for human skeletal muscle. These high‐performance results since the heating that drives fast actuation cycles are largely restricted to the muscle sheath, and this sheath is in direct contact with ambient temperature air.

Hierarchically Structured and Scalable Artificial Muscles for Smart Textiles.

Fiber-based artificial muscles with excellent actuation performance are gaining great attention as soft materials for flexible actuators; however, current advances in fiber-based artificial muscles generally suffer from high cost, harsh stimulation regimes, limiting deformations, chemical toxicity, or complex manufacturing processing, which hinder the widespread application of those artificial muscles in engineering and practical usage. Herein, a facile cross-scale processing strategy is presented to construct commercially available nontoxic viscose fibers into fast responsive and humidity-driven yarn artificial muscles with a recorded torsional stroke of 1752° cm-1 and a maximum rotation speed up to 2100 rpm, which are comparable to certain artificial muscles made from carbon-based composite materials. The underlying mechanism of such outstanding actuation performance that begins to form at a mesoscale is discussed by theoretical modeling and microstructure characterization. The as-prepared yarn artificial muscles are further scaled up to large-sized fabric muscles through topological weaving structures by integrating different textile technologies. These fabric muscles extend the simple motion of yarn muscles into higher-level diverse deformations without any composite system, complex synthetic processing, and component design, which enables the development of new fiber-based artificial muscles for versatile applications, such as smart textiles and intelligent systems.

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. We here derive such muscles from naturally abundant lotus fibers. A coiled lotus fiber yarn muscle provides a large, reversible tensile stroke of 38% and a work capacity during contraction of 450 J/kg, which is 56 times higher than that of natural skeletal muscles and higher than that for any other reported natural fiber muscles. In addition, highly twisted lotus fiber yarn muscles provide a fully reversible torsional stroke of 200°/mm of muscle length and a peak rotation speed of 200 rpm, with a generated specific torque of 488 mN·m/kg for a 2.5 cm long muscle. Potential applications of these lotus fiber yarn muscles are demonstrated for a weight-lifting artificial limb and a smart textile.

Strong and Robust Electrochemical Artificial Muscles by Ionic-Liquid-in-Nanofiber-Sheathed Carbon Nanotube Yarns.

To address the lack of a suitable electrolyte that supports the stable operation of the electrochemical yarn muscles in air, an ionic-liquid-in-nanofibers sheathed carbon nanotube (CNT) yarn muscle is prepared. The nanofibers serve as a separator to avoid the short-circuiting of the yarns and a reservoir for ionic liquid. The ionic-liquid-in-nanofiber-sheathed yarn muscles are strong, providing an isometric stress of 10.8MPa (about 31 times the skeletal muscles). The yarn muscles are highly robust, which can reversibly contract stably at such conditions as being knotted, wide-range humidity (30 to 90 RH%) and temperature (25 to 70 °C), and long-term cycling and storage in air. By utilizing the accumulated isometric stress, the yarn muscles achieve a high contraction rate of 36.3% s-1 . The yarn muscles are tightly bundled to lift heavy weights and grasp objects. These unique features can make the strong and robust yarn muscles as a desirable actuation component for robotic devices.

Moisture-sensitive torsional cotton artificial muscle and textile**Project supported by the National Key Research and Development Program of China (Grant No. 2017YFB0307001), the National Natural Science Foundation of China (Grant Nos. U1533122 and 51773094), the Natural Science Foundation of Tianjin, China (Grant No. 18JCZDJC36800), the Science Foundation for Distinguished Young Scholars of Tianjin, China (Grant No. 18JCJQJC46600), the Fundamental Research Funds

Developing moisture-sensitive artificial muscles from industrialized natural fibers with large abundance is highly desired for smart textiles that can respond to humidity or temperature change. However, currently most of fiber artificial muscles are based on non-common industrial textile materials or of a small portion of global textile fiber market. In this paper, we developed moisture-sensitive torsional artificial muscles and textiles based on cotton yarns. It was prepared by twisting the cotton yarn followed by folding in the middle point to form a self-balanced structure. The cotton yarn muscle showed a torsional stroke of 42.55 °/mm and a rotational speed of 720 rpm upon exposure to water moisture. Good reversibility and retention of stroke during cyclic exposure and removal of water moisture were obtained. A moisture-sensitive smart window that can close when it rains was demonstrated based on the torsional cotton yarn muscles. This twist-based technique combining natural textile fibers provides a new insight for construction of smart textile materials.