High-Power Hydro-Actuators Fabricated from Biomimetic Carbon Nanotube Coiled Yarns with Fast Electrothermal Recovery

Electro-Responsive Thermochromic and Mechanically Enhanced CNT Yarns through Solution Blow Spinning Encapsulation

Carbon nanotube (CNT) yarns combine textile adaptability, conductivity, and electrothermal functionality, positioning them as a key material for advancing flexible smart fabrics, particularly in electrothermal applications. However, their widespread use is hindered by safety concerns related to exposed CNT yarns acting as electrical heating elements and their intrinsic black color, which limits aesthetic flexibility in textile design. Therefore, flexible encapsulation of CNTs is essential for unlocking their full industrial potential. This study demonstrates the successful application of solution blow spinning (SBS) technology for encapsulating CNT yarns, emphasizing its scalability and efficiency in producing flexible, electro-responsive conductive yarns with significantly enhanced mechanical properties. Various polymers, including ultrahigh molecular weight polyethylene (UHMWPE), polylactic acid (PLA), polyacrylonitrile (PAN), and polyvinylidene fluoride (PVDF), are explored for encapsulating CNT yarns, significantly reducing the risk of electrical exposure and providing tunable color options by effectively covering the yarns' intrinsic blackness. SBS also enhances yarn performance and durability. Among them, C-PE (CNT core with UHMWPE sheath) exhibits a remarkable improvement in abrasion resistance, with the cycle count increasing from 35 to 3115. C-PVDF (CNT core with PVDF sheath) demonstrates significant improvements in elongation, increasing from 42.8% to 63.6%. Furthermore, incorporating thermochromic-enhanced polymers enables real-time temperature visualization, offering both functional and aesthetic versatility. These advancements pave the way for high-performance, multifunctional smart textiles tailored for wearable electronic applications.

Dual-Scale Hydration-Induced Electrical and Mechanical Torsional Energy Harvesting in Heterophilically Designed CNT Yarns

Water holds vast potential for a useful energy source, yet traditional approaches capture only a fraction of it. This study introduces a heterophilically designed carbon nanotube (CNT) yarn with an asymmetric configuration. This yarn is capable of both electrical and mechanical torsional energy harvesting through dual-scale hydration. Fabricated via half-electrochemical oxidation, the yarn contains a hydrophilic region enriched with oxygen-containing functional groups and a hydrophobic pristine CNT region. Molecular-scale hydration triggers proton release in the hydrophilic region. Consequently, a concentration gradient is established that generates a peak open-circuit voltage of 106.0 mV and a short-circuit current of 20.6 mA cm-2. Simultaneously, microscale hydration induces water absorption into inter-bundle microchannels, resulting in considerable yarn volume expansion. This process leads to hydro-driven actuation with a torsional stroke of 78.8° mm-1 and a maximum rotational speed of 1012 RPM. The presented simultaneous harvesting results in electrical and mechanical power densities of 3.5 mW m-2 and 34.3 W kg-1, respectively, during a hydration cycle. By integrating molecular and microscale hydrations, the proposed heterophilic CNT yarns establish an unprecedented platform for simultaneous electrical and mechanical energy harvesting from water, representing a groundbreaking development for sustainable applications.

Enhanced Electrothermal Properties of Core-Sheath Lignin-Derived Carbon Nanotube Yarns with UHMWPE Insulation

A critical challenge in wearable electrothermal textiles is achieving effective insulation while maintaining sheath flexibility, which is essential for enhancing the mechanical properties and durability of conductive materials under everyday conditions, such as washing, stretching, and twisting. In this work, we employ a coaxial tubular braiding technique to coat a high-conductivity carbon nanotube (CNT) yarn with a high-strength insulation layer made of ultra-high-molecular-weight polyethylene (UHMWPE) multifilaments, resulting in a core-sheath-structure CNT yarn with excellent electrothermal performance. By adjusting the number of UHMWPE multifilaments and the sheath braiding angle, we achieve high flexibility, high tensile strength, and abrasion and wash resistance, as well as improved electrical stability for the CNT yarns. Additionally, the CNT yarns with an insulation layer effectively prevent short-circuiting during use and achieve superior thermal management, with a significant increase in steady-state temperature under operational conditions, exhibiting significant potential for applications in wearable electronic devices.

Sodium alginate-based coaxial fibers synergistically integrate moisture actuation, length tracing, humidity sensing, and electric heating

The development of wearable electronics has driven the need for smart fibers with advanced multifunctional synergy. In this paper, we present a design of a multifunctional coaxial fiber that is composed of a biopolymer-derived core and an MXene/silver nanowire (AgNW) sheath by wet spinning. The fiber synergistically integrates moisture actuation, length tracing, humidity sensing, and electric heating, making it highly promising for portable devices and protective systems. The biopolymer-derived core provides deformation for moisture-sensitive actuation, while the MXene/AgNW sheath with good conductivity enables the fiber to perform electric heating, humidity sensing, and self-sensing actuation. The coaxial fiber can be programmed to rapidly desorb water molecules to shrink to its original length by using the MXene/AgNW sheath as an electrical heater. We demonstrate proof-of-concept applications based on the multifunctional fibers for thermal physiotherapy and wound healing/monitoring. The sodium alginate@MXene-based coaxial fiber presents a promising solution for the next-generation of smart wearable electronics.

Soft Fiber/Textile Actuators: From Design Strategies to Diverse Applications

Fiber/textile-based actuators have garnered considerable attention due to their distinctive attributes, encompassing higher degrees of freedom, intriguing deformations, and enhanced adaptability to complex structures. Recent studies highlight the development of advanced fibers and textiles, expanding the application scope of fiber/textile-based actuators across diverse emerging fields. Unlike sheet-like soft actuators, fibers/textiles with intricate structures exhibit versatile movements, such as contraction, coiling, bending, and folding, achieved through adjustable strain and stroke. In this review article, we provide a timely and comprehensive overview of fiber/textile actuators, including structures, fabrication methods, actuation principles, and applications. After discussing the hierarchical structure and deformation of the fiber/textile actuator, we discuss various spinning strategies, detailing the merits and drawbacks of each. Next, we present the actuation principles of fiber/fabric actuators, along with common external stimuli. In addition, we provide a summary of the emerging applications of fiber/textile actuators. Concluding with an assessment of existing challenges and future opportunities, this review aims to provide a valuable perspective on the enticing realm of fiber/textile-based actuators.

Transition of Carbon Nanotube Sheets from Hydrophobicity to Hydrophilicity by Facile Electrochemical Wetting

The present study delves into the transformative effects of electrochemical oxidation on the hydrophobic-to-hydrophilic transition of carbon nanotube (CNT) sheets. The paper elucidates the inherent advantages of CNT sheets, such as high electrical conductivity and mechanical strength, and contrasts them with the limitations posed by their hydrophobic nature. A comprehensive investigation is conducted to demonstrate the efficacy of electrochemical oxidation treatment in modifying the surface properties of CNT sheets, thereby making them hydrophilic. The study reveals that the treatment not only is cost-effective and time-efficient compared to traditional plasma treatment methods but also results in a significant decrease in water contact angle. Mechanistic insights into the hydrophilic transition are provided, emphasizing the role of oxygen-containing functional groups introduced during the electrochemical oxidation process.

Electrochemically Oxidized Carbon Nanotube Sheets for High-Performance and Flexible-Film Supercapacitors

The development of flexible, high-performance supercapacitors has been a focal point in energy storage research. While carbon nanotube (CNT) sheets offer promising mechanical and electrical properties, their low electrical double-layer capacitance significantly limits their practicability. Herein, we introduce a novel approach to address this challenge via the electrochemical oxidation treatment of CNT sheets stacked on a polyethylene terephthalate substrate. This introduces oxygen-containing functional groups onto the CNT surface, thereby dramatically enhancing the pseudocapacitive effect and improving ion adsorption. Consequently, using the material in a two-electrode system increased the capacitance by 54 times compared to pristine CNT. The results of electrochemical performance characterization, including cyclic voltammograms, galvanostatic charge/discharge curves, and capacitance retention testing data, confirm the efficacy of the electrochemical oxidation approach. Furthermore, the mechanical flexibility of the electrochemically wetted CNT sheets was validated through resistance and discharge retention testing under repetitive bending (98% capacitance retention after 1000 bending cycles). The results demonstrate that electrochemically wetted CNT sheets retain their intrinsic mechanical and electrical properties while significantly enhancing the electrochemical performance (0.59 mF/cm2 or 97.8 F/g). This work represents a significant advancement in the development of flexible, high-performance supercapacitors with potential applicability to wearable electronics, flexible displays, and next-generation energy storage solutions.

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.