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.

Development of effective model for non-destructive detection of defective kiwifruit based on graded lines.

The accurate detection of external defects in kiwifruit is an important part of postharvest quality assessment. Previous studies have not considered the problems posed by the actual grading environment. In this study, we designed a novel approach based on improved Yolov5 to achieve real-time and efficient non-destructive detection of multiple defect categories in kiwifruit. First, a kiwifruit image acquisition device based on grading lines was developed to enhance the image acquisition. Subsequently, a kiwifruit dataset was constructed based on the external defect characteristics and a new data enhancement method was proposed to augment the kiwifruit samples. Thereafter, the SPD-Conv and DW-Conv modules were combined to improve Yolov5s, with EIOU as the loss calculation function. The results demonstrated that the improved model training loss value was 0.013 lower, the convergence was accelerated, the number of parameters was reduced, and the computational effort was increased. The detection accuracies of the samples in the test set, which included healthy, leaf-rubbing damaged, healed cuts or scarred, and sunburned samples, were 98.8%, 98.7%, 97.6%, and 95.9%, respectively, with an overall detection accuracy of 97.7%. The detection time was 8.0 ms, thereby meeting real-time sorting demands. The average detection accuracy and model size of SSD, Yolov5s, Yolov7, and Yolov5-Ours were compared. When the confidence threshold was 0.5, the detection accuracy of Yolov5-Ours was 10% and 6.4% higher than that of SSD and Yolov5s, respectively. In terms of the model size, Yolov5-Ours was approximately 6.5- and 4-fold smaller than SSD and Yolov7, respectively. Thus, Yolov5-Ours achieved the highest accuracy, adaptability, and robustness for the detection of all kiwifruit categories as well as a small volume and portability. These results can provide technical support for the non-destructive detection and grading of agricultural products in the future.

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

Artificial yarn muscles show great potential in applications requiring low-energy consumption while maintaining high performance. However, conventional designs have been limited by weak ion-yarn muscle interactions and inefficient "rocking-chair" ion migration. To address these limitations, we present an electrochemical artificial yarn muscle design driven by a dual-ion co-regulation system. By utilizing two reaction channels, this system shortens ion migration pathways, leading to faster and more efficient actuation. During the charging/discharging process, [Formula: see text] ions react with carbon nanotube yarn, while Li+ ions react with an Al foil. The intercalation reaction between [Formula: see text] and collapsed carbon nanotubes allows the yarn muscle to achieve an energy-free high-tension catch state. The dual-ion coordinated yarn muscles exhibit superior contractile stroke, maximum contractile rate, and maximum power densities, exceeding those of "rocking-chair" type ion migration yarn muscles. The dual-ion co-regulation system enhances the ion migration rate during actuation, resulting in improved performance. Moreover, the yarn muscles can withstand high levels of isometric stress, displaying a stress of 61 times that of skeletal muscles and 8 times that of "rocking-chair" type yarn muscles at higher frequencies. This technology holds significant potential for various applications, including prosthetics and robotics.

Pretension-Free and Self-Recoverable Coiled Artificial Muscle Fibers with Powerful Cyclic Work Capability.

Similar to natural muscle fibers, coiled artificial muscle fibers provide a straightforward contraction. However, unlike natural muscle fibers, their recovery from the contracted state to the initial state requires high stress, resulting in almost zero work during a full actuation cycle. Herein, a self-recoverable coiled artificial muscle fiber was prepared by conformally coating an elastic carbon nanotube (CNT) fiber with a very thin liquid crystal elastomer (LCE) sheath. The as-obtained muscle fiber demonstrated excellent actuation properties comprising 56.9% contractile stroke, 1522%/s contraction rate, 7.03 kW kg-1 power density, and 32,000 stable cycles. The LCE chains were helically aligned in a nematic phase, and the phase change of the LCE caused by Joule heating drove the actuation process. Moreover, the LCE/CNT fiber had a well-separated, torsionally stable, and elastic coiled structure, which permitted large contractile strokes and acted as an elastic template for external-stress-free recovery. Thus, the use of self-recoverable muscle fibers to mimic the natural muscles for object dragging, multidirectional bending, and quick striking was demonstrated.

Moisture-Adaptive Contractile Biopolymer-Derived Fibers for Wound Healing Promotion.

The advancement in thermosensitive active hydrogels has opened promising opportunities to dynamic full-thickness skin wound healing. However, conventional hydrogels lack breathability to avoid wound infection and cannot adapt to wounds with different shapes due to the isotropic contraction. Herein, a moisture-adaptive fiber that rapidly absorbs wound tissue fluid and produces a large lengthwise contractile force during the drying process is reported. The incorporation of hydroxyl-rich silica nanoparticles in the sodium alginate/gelatin composite fiber greatly improves the hydrophilicity, toughness, and axial contraction performance of the fiber. This fiber exhibits a dynamic contractile behavior as a function of humidity, generating ≈15% maximum contraction strain or ≈24 MPa maximum isometric contractile stress. The textile knitted by the fibers features excellent breathability and generates adaptive contraction in the target direction during the natural desorption of tissue fluid from the wounds. In vivo animal experiments further demonstrate the advantages of the textiles over traditional dressings in accelerating wound healing.

Artificial neuromuscular fibers by multilayered coaxial integration with dynamic adaption.

Integrating sense in a thin artificial muscle fiber for environmental adaption and actuation path tracing, as a snail tentacle does, is highly needed but still challenging because of the interfacing mismatch between the fiber's actuation and sensing components. Here, we report an artificial neuromuscular fiber by wrapping a carbon nanotube (CNT) fiber core in sequence with an elastomer layer, a nanofiber network, and an MXene/CNT thin sheath, achieving the ingenious sense-judge-act intelligent system in an elastic fiber. The CNT/elastomer components provide actuation, and the sheath enables touch/stretch perception and hysteresis-free cyclic actuation tracing due to its strain-dependent resistance. As a whole, the coaxial structure builds a dielectric capacitor that enables sensitive touchless perception. The key to seamless integration is to use a nanofiber interface that allows the sensing layer to adaptively trace but not restrict actuation. This work provides promising solutions for closed-loop control for future intelligent soft robots.

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.

Fabrication of high-performance carbon nanotube/copper composite fibers by interface thiol-modification.

Carbon nanotube (CNT)/copper (Cu) composite fibers are placed great expectations as the next generation of light-weight, conductive wires. However, the electrical and mechanical performances still need to be enhanced. Herein, we demonstrate a strategy that is electrodeposition Cu on thiolated CNT fibers to solve the grand challenge which is enhancing the performance of CNT/Cu composite fibers. Thiol groups are introduced to the surface of the CNT fibers through a controllable O2plasma carboxylation process and amide reaction. Compared with CNT/Cu composite fibers, there are 82.7% and 29.6% improvements in electrical conductivity and tensile strength of interface thiol-modification composite fibers. The enhancement mechanism is also explored that thiolated CNT fibers could make strong interactions between Cu and CNT, enhancing the electrical and mechanical performance of CNT/Cu composites. This work proposes a convenient, heat-treatment-free strategy for high-performance CNT/Cu composite fibers, which can be manufactured for large-scale production and applied to next-generation conductive wires.

Self-sensing coaxial muscle fibers with bi-lengthwise actuation.

Artificial muscle fibers as a promising biomimetic actuator are needed for such applications as smart soft robots, muscle function restoration, and physical augmentation. Currently developed artificial muscle fibers have shown attractive performance in contractile and torsional actuations. However, the contractile muscle fibers do not have the capability of stimulus-responsive elongation, and real-time identifying their contractile position by themselves is still challenging. We report herein the preparation of a Ti3C2Tx MXene/single walled carbon-nanotubes (SWCNTs)-coated carbon nanotube (CNT)@polydimethylsiloxane (PDMS) coaxial muscle fiber that integrates the important features of self-position sensing and bi-lengthwise actuation. The bi-lengthwise actuation is realized by utilizing the large expansion coefficient difference of PDMS in response to solvent and heat, which results in ∼5% maximum elongation by n-heptane adsorption and ∼19% maximum contraction by electric heating under the optimal conditions. Meanwhile, due to the piezoresistive effect of the MXene/SWCNTs layer, the resistance change of this coating layer is almost linearly dependent on the contraction of the coaxial muscle fiber, providing a function of real-time self-position sensing. Furthermore, an application of using a bundle of these multifunctional coaxial muscle fibers for a bionic arm has been demonstrated, which provides new insights into the design of integrated intelligent artificial muscles with synergistic multiple functions.

Programmable Contractile Actuations of Twisted Spider Dragline Silk Yarns.

The contraction behavior of spider dragline silk upon water exposure has drawn particular interest in developing humidity-responsive smart materials. We report herein that the spider dragline silk yarns with moderate twists can generate much improved lengthwise contraction of 60% or an isometric stress of 11 MPa when wetted by water. Upon the removal of the absorbed water, the dried and contracted spider silk yarns showed programmable contractile actuations. These yarns can be plastically stretched to any specified lengths between the fully contracted state and the state before supercontraction and return to the fully contracted state when wetted. Moreover, the generated isometric stress of these yarns is also programmable, depending on the stretching ratio. The mechanism of the programmable reversible contraction is based on the plastic mechanical property of the dried and contracted spider silk yarns, which can be explained by the variation of the hydrogen bonds and the secondary structures of the proteins in spider dragline silk. Humidity alarm switches, smart doors, and wound healing devices based on the programmable contractile actuations of the spider silk yarns were demonstrated, which provide application scenarios for the supercontraction of spider dragline silk.

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 10.8 MPa (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.