Self-Healable Multifunctional Fibers via Thermal Drawing.

The development of soft electronics and soft fiber devices has significantly advanced flexible and wearable technology. However, they still face the risk of damage when exposed to sharp objects in real-life applications. Taking inspiration from nature, self-healable materials that can restore their physical properties after external damage offer a solution to this problem. Nevertheless, large-scale production of self-healable fibers is currently constrained. To address this limitation, this study leverages the thermal drawing technique to create elastic and stretchable self-healable thermoplastic polyurethane (STPU) fibers, enabling cost-effective mass production of such functional fibers. Furthermore, despite substantial research into the mechanisms of self-healable materials, quantifying their healing speed and time poses a persistent challenge. Thus, transmission spectra are employed as a monitoring tool to observe the real-time self-healing process, facilitating an in-depth investigation into the healing kinetics and efficiency. The versatility of the fabricated self-healable fiber extends to its ability to be doped with a wide range of functional materials, including dye molecules and magnetic microparticles, which enables modular assembly to develop distributed strain sensors and soft actuators. These achievements highlight the potential applications of self-healable fibers that seamlessly integrate with daily lives and open up new possibilities in various industries.

High-Fluidity/High-Strength Dual-Layer Gel Electrolytes Enable Ultra-Flexible and Dendrite-Free Fiber-Shaped Aqueous Zinc Metal Battery.

Fiber-shaped aqueous zinc-ion batteries (FAZIBs) with intrinsic safety, highcapacity, and superb omnidirectional flexibility hold promise for wearable energy-supply devices. However, the interfacial separation of fiber-shaped electrodes and electrolytes caused by Zinc (Zn) stripping process and severe Zn dendrites occurring at the folded area under bending condition seriously restricts FAZIBs' practical application. Here, an advanced confinement encapsulation strategy is originally reported to construct dual-layer gel electrolyte consisting of high-fluidity polyvinyl alcohol-Zn acetate inner layer and high-strength Zn alginate outer layer for fiber-shaped Zn anode. Benefiting from the synergistic effect of inner-outer gel electrolyte and the formation of solid electrolyte interphase on Zn anode surface by lysine additive, the resulting fiber-shaped Zn-Zn symmetric cell delivers long cycling life over 800 h at 1 mA cm-2 with dynamic bending frequency of 0.1 Hz. The finite element simulation further confirms that dual-layer gel electrolyte can effectively suppress the interfacial separation arising from the Zn stripping and bending process. More importantly, a robust twisted fiber-shaped Zn/zinc hexacyanoferrate battery based on dual-layer gel electrolyte is successfully assembled, achieving a remarkable capacity retention of 97.7% after bending 500 cycles. Therefore, such novel dual-layer gel electrolyte design paves the way for the development of long-life fiber-shaped aqueous metal batteries.

High-quality semiconductor fibres via mechanical design.

Recent breakthroughs in fibre technology have enabled the assembly of functional materials with intimate interfaces into a single fibre with specific geometries1-11, delivering diverse functionalities over a large area, for example, serving as sensors, actuators, energy harvesting and storage, display, and healthcare apparatus12-17. As semiconductors are the critical component that governs device performance, the selection, control and engineering of semiconductors inside fibres are the key pathways to enabling high-performance functional fibres. However, owing to stress development and capillary instability in the high-yield fibre thermal drawing, both cracks and deformations in the semiconductor cores considerably affect the performance of these fibres. Here we report a mechanical design to achieve ultralong, fracture-free and perturbation-free semiconductor fibres, guided by a study on stress development and capillary instability at three stages of the fibre formation: the viscous flow, the core crystallization and the subsequent cooling stage. Then, the exposed semiconductor wires can be integrated into a single flexible fibre with well-defined interfaces with metal electrodes, thereby achieving optoelectronic fibres and large-scale optoelectronic fabrics. This work provides fundamental insights into extreme mechanics and fluid dynamics with geometries that are inaccessible in traditional platforms, essentially addressing the increasing demand for flexible and wearable optoelectronics.

Emerging Amorphous to Crystalline Conversion Chemistry in Ca-Doped VO2 Cathodes for High-Capacity and Long-Term Wearable Aqueous Zinc-Ion Batteries.

Amorphous transition metal oxides have attracted significant attention in energy storage devices owing to their potentially desirable electrochemical properties caused by abundant unsaturated dangling bonds. However, the amorphization further amplifies the shortcoming of the poor intrinsic electronic conductivity of the metal oxides, resulting in unsatisfying rate capability and power density. Herein, freestanding amorphous Ca-doped V2 O5 (a-Ca-V2 O5 ) cathodes are successfully prepared via in situ electrochemical oxidation of Ca-doped VO2 nanoarrays for wearable aqueous zinc-ion batteries. The doping of Ca and construction of freestanding structure effectively uncover the potential of amorphous V2 O5 , which can make full use of the abundant active sites for high volumetric capacity and simultaneously achieve fast reaction kinetics for excellent rate performance. More importantly, the introduction of Ca can notably reduce the formation energy of VO2 according to theoretical calculation results and realizes amorphous to crystalline reversible conversion chemistry in the charge/discharge procedure, thereby facilitating the reversible capacity of the newly developed a-Ca-V2 O5 . This work provides an innovative design strategy to construct high-rate capacity amorphous metal oxides as freestanding electrodes for low-cost and high-safe wearable energy-storage technology.

Intuition-and-Tactile Bimodal Sensing Based on Artificial-Intelligence-Motivated All-Fabric Bionic Electronic Skin for Intelligent Material Perception.

Developing electronic skins (e-skins) with extraordinary perception through bionic strategies has far-reaching significance for the intellectualization of robot skins. Here, an artificial intelligence (AI)-motivated all-fabric bionic (AFB) e-skin is proposed, where the overall structure is inspired by the interlocked bionics of the epidermis-dermis interface inside the skin, while the structural design inspiration of the dielectric layer derives from the branch-needle structure of conifers. More importantly, AFB e-skin achieves intuition sensing in proximity mode and tactile sensing in pressure mode based on the fringing and iontronic effects, respectively, and is simulated and verified through COMSOL finite element analysis. The proposed AFB e-skin in pressure mode exhibits maximum sensitivity of 15.06 kPa-1 (<50 kPa), linear sensitivity of 6.06 kPa-1 (50-200 kPa), and fast response/recovery time of 5.6 ms (40 kPa). By integrating AFB e-skin with AI algorithm, and with the support of material inference mechanisms based on dielectric constant and softness/hardness, an intelligent material perception system capable of recognizing nine materials with indistinguishable surfaces within one proximity-pressure cycle is established, demonstrating abilities that surpass human perception.

In Situ Etching of Multifunctional Three-Dimensional Interfacial Layers for the Construction of Porous Zn Anodes with Enhanced Surface Textures.

Aqueous Zn-ion batteries offer the advantages of greater security and lower fabrication costs over their lithium-ion counterparts. However, their further advancement and practical application are hindered by the drastic decay in their performance due to the uncontrollable dendrite growth on Zn anodes. In this study, we fabricated a versatile three-dimensional (3D) interfacial layer (3D PVDF-Zn(TFO)2 (PVDF: poly(vinylidene fluoride); TFO: trifluoromethanesulfonate), which simultaneously formed porous Zn-metal anodes (PZn) with an enhanced (002) texture, via a in situ etching scheme. The 3D PVDF-Zn(TFO)2@PZn symmetrical cells leverage the advantages of surface coating and 3D porous architectures to yield extra-long cyclic lifetimes of over 5300 h (0.1 mA cm-2). The fabricated anodes were found to be compatible with MnO2 cathodes, and the resulting full batteries delivered an outstanding capacity of 336 mAh g-1 at 0.1 A g-1 and exhibited impressive long-term reversibility with a capacity retention of 78.7% for 2000 cycles. The proposed coating strategy is viable for developing porous structures with cutting-edge designs and for textured surface engineering.

High-Sensitivity Self-Powered Photodetector Fibers Using Hierarchical Heterojunction Photoelectrodes Enable Wearable Amphibious Optoelectronic Textiles.

Fiber-shaped photodetectors (FPDs) with multidirectional light absorption properties offer exciting opportunities for intelligent optoelectronic textiles. However, achieving FPDs capable of working in ampule environments, especially with high sensitivity, remains a fundamental challenge. Here, quasi-solid-state twisted-fiber photoelectrochemical photodetectors (FPPDs) consisting of photoanode, gel electrolyte, and counter electrode are successfully assembled. In situ decorated n-type one-dimensional (1D) TiO2 nanowire arrays with 2D Ni-Fe metal-organic framework (NiFeMOF) nanosheets serve as hierarchical heterojunction photoanodes, thereby optimizing carrier transfer dynamics at the photoanode/electrolyte interface. As expected, the resulting self-powered FPPD exhibits 88.6 mA W-1 high responsiveness and a < 30 ms fast response time. Significantly, our FPPD can operate in both terrestrial and aquatic environments thanks to its intrinsic ionic properties, making it a versatile tool for detecting ultraviolet light on land and facilitating optical communication underwater. These high-sensitivity self-powered FPPDs with hierarchical heterojunction photoelectrodes hold promise for the development of wearable amphibious optoelectronic textiles.

Integrating High-Sensitivity Photodetector and High-Energy Aqueous Battery in All-in-One Triple-Twisted Fiber.

Fiber-shaped photodetectors (FPDs) have attracted special attention to wearable health monitoring due to their 3D absorption capabilities. However, the practical application of traditional FPDs is severely limited by the irreversible degradation of performance caused by vulnerable interface compatibility on complex deformation and a single function. Here, an integrated photoelectrochemical FPD/battery device (FPDB) is designed, consisting of a common electrode, photoanode, anode, and sol-gel electrolyte as an isolation layer, which not only effectively avoids the short circuit problem of FPD but also endows high-efficiency energy storage capacity. As expected, the resulting all-in-one triple-twisted fiber-shaped FPDB simultaneously achieves high responsiveness of 151.45 mA W-1 and excellent volume capacity of 18.75 mAh cm-3. Such a stable architectural design and multifunctional integration of functional fibers accelerate the development of next-generation wearable fabrics.

Fluorescent Fiber-Shaped Aqueous Zinc-Ion Batteries for Bifunctional Multicolor-Emission/Energy-Storage Textiles.

Wearable smart textiles are natural carriers to enable imperceptible and highly permeable sensing and response to environmental conditions via the system integration of multiple functional fibers. However, the existing massive interfaces between different functional fibers significantly increase the complexity and reduce the wearability of the textile system. Thus, it is significant yet challenging to achieve all-in-one multifunctional fibers for realizing miniaturized and lightweight smart textiles with high reliability. Herein, as bifunctional electrolyte additives, fluorescent carbon dots with abundant zincophilic functional groups are introduced into electrolytes to develop fluorescent fiber-shaped aqueous zinc-ion batteries (FFAZIBs). Originating from effective dendrite suppression of Zn anodes and multiple active sites of freestanding Prussian blue cathodes, high energy density (0.17 Wh·cm-3) and long-term cyclability (78.9% capacity retention after 1500 cycles) are achieved for FFAZIBs. More importantly, the one-dimensional structure ensures the same luminance in all directions of FFAZIBs, enabling the form of multicolor display-in-battery textiles.

Free-standing conductive nickel metal-organic framework nanowires as bifunctional electrodes for wearable pressure sensors and Ni-Zn batteries.

Free-standing metal-organic frameworks (MOFs) with controllable structure and good stability are emerging as promising materials for applications in flexible pressure sensors and energy-storage devices. However, the inherent low electrical conductivity of MOF-based materials requires complex preparation processes that involve high-temperature carbonization. This work presents a simple method to grow conductive nickel MOF nanowire arrays on carbon cloth (Ni-CAT@CC) and use Ni-CAT@CC as the functional electrodes for flexible piezoresistive sensor. The resulting sensor is able to monitor human activity, including elbow bending, knee bending, and wrist bending. Besides, the soft-packaged aqueous Ni-Zn battery is assembled with Ni-CAT@CC, a piece of glass microfiber filters, and Zn foil acting as cathode, separator, and anode, respectively. The Ni-Zn battery can be used as a power source for finger pressure monitoring. This work demonstrates free-standing MOF-based nanowires as bifunctional fabric electrodes for wearable electronics.

Fiber Crossbars: An Emerging Architecture of Smart Electronic Textiles.

Smart wearables have a significant impact on people's daily lives, enabling personalized motion monitoring, realizing the Internet of Things, and even reshaping the next generation of telemedicine systems. Fiber crossbars (FCs), constructed by crossing two fibers, have become an emerging architecture among the accessible structures of state-of-the-art smart electronic textiles. The mechanical, chemical, and electrical interactions between crossing fibers result in extensive functionalities, leading to the significant development of innovative electronic textiles employing FCs as their basic units. This review provides a timely and comprehensive overview of the structure designs, material selections, and assembly techniques of FC-based devices. The recent advances in FC-based devices are summarized, including multipurpose sensing, multiple-mode computing, high-resolution display, high-efficient power supply, and large-scale textile systems. Finally, current challenges, potential solutions, and future perspectives for FC-based systems are discussed for their further development in scale-up production and commercial applications.

In situ crafting of a 3D N-doped carbon/defect-rich V2O5-x·nH2O nanosheet composite for high performance fibrous flexible Zn-ion batteries.

Aqueous fibrous batteries with tiny volume, light weight and stretchability have furthered wearable smart textile systems like biocompatible electronics for a more efficient use of electricity. Challenges still faced by fibrous batteries include not only the deficient actual capacity but the cyclability on the cathode side. Herein, an in situ anodic oxidation strategy is reported to prepare 3D N-doped/defect-rich V2O5-x·nH2O nanosheets (DVOH@NC) as fibrous cathodes for aqueous zinc-ion batteries (AZIBs). Benefiting from the substantially abundant reaction sites, enhanced electrical conductivity, short electron/ion diffusion path and high mass loading, the newly designed DVOH@NC fibrous electrode delivers impressive capacity (711.9 mA h cm-3 at 0.3 A cm-3) and long-term durability (95.5% capacity retention after 3000 cycles), substantially outperforming previously reported fibrous vanadium-based cathodes. First-principles density functional theory (DFT) calculations further revealed that the oxygen vacancies can weaken the electrostatic interaction between Zn2+ and the host cathode accompanying the low Zn2+ diffusion energy barrier. To highlight the potential applications, a prototype wearable fiber-shaped AZIB (FAZIB) with remarkable flexibility and extraordinary weaving capability was demonstrated. More encouragingly, the resulting FAZIB could be charged with solar cells and power a pressure sensor. Thus, our work provides a promising strategy to rationally construct high-performance flexible vanadium-based cathodes for next-generation wearable AZIBs.

Vanadium Dioxide Nanosheets Supported on Carbonized Cotton Fabric as Bifunctional Textiles for Flexible Pressure Sensors and Zinc-Ion Batteries.

Flexible pressure sensors and aqueous batteries have been widely used in the rapid development of wearable electronics. The synergistic functionalities of versatile materials with multidimensional architectures are recognized to have a significant impact on the performance of flexible electronics. Herein, a facile hydrothermal strategy was demonstrated to conformally grow vanadium dioxide nanosheets on carbonized cotton fabrics (VO2/CCotton), which is a candidate material used in flexible piezoresistive sensors. As a result, the VO2/CCotton-based pressure sensor behaved with high sensitivity (S = 7.12 kPa-1 in the pressure range of 0-2.0 kPa) and a stable sensing ability in a wide pressure scale of 0-120 kPa. Further practical applications were performed in monitoring delicate physiological signals as well, such as twisting, blowing, and voice vibration recognitions. In addition, another application for energy storage was investigated as well. A quasi-solid-state aqueous zinc-ion battery was assembled with VO2/CCotton as the cathode and a film of Zn nanosheets/carbon nanotube as the anode. A capacity as high as 301.5 mAh g-1 and remarkable durability of 88.7% capacity retention after 5000 cycles at 10 A g-1 were found. These exceptional outcomes are attributed to the unique three-dimensional architecture and the prominent synergetic effects of CCotton and VO2 and allow for the proposal of novel guidelines for next-generation multifunctional flexible electronics.

Arrayed Heterostructures of MoS2 Nanosheets Anchored TiN Nanowires as Efficient Pseudocapacitive Anodes for Fiber-Shaped Ammonium-Ion Asymmetric Supercapacitors.

Nonmetallic ammonium ions that feature high safety, low molar mass, and small hydrated radius properties have shown great advantages in wearable aqueous supercapacitors. The construction of high-energy-density flexible ammonium-ion asymmetric supercapacitors (AASCs) is promising but still challenging due to the lack of high-capacitance pseudocapacitive anodes. Herein, freestanding core-shell heterostructures supported on carbon nanotube fibers were designed by anchoring MoS2 nanosheets on nanowires (MoS2@TiN/CNTF) as anodes for AASCs. With contributions of abundant active sites and conspicuous synergistic effects of multiple components for arrayed heterostructure engineering, the developed MoS2@TiN/CNTF anodes exhibit a specific capacitance of 1102.5 mF cm-2 at 2 mA cm-2. Theoretical calculations confirm the dramatic enhancement of the binding strength of ammonium ions on the MoS2 shell layer at the heterostructure, where a built-in electric field exists to accelerate the charge transfer. By utilizing a MnO2/CNTF cathode and NH4Cl/poly(vinyl alcohol) (PVA) as a gel electrolyte, quasi-solid-state fiber-shaped AASCs were successfully constructed, achieving a specific capacitance of 351.2 mF cm-2 and an energy density of 195.1 µWh cm-2, outperforming most recently reported fiber-shaped supercapacitors. This work provides a promising strategy to rationally design heterostructure engineering of MoS2@TiN nanoarrays toward advanced anodes for application in next-generation AASCs.

Freestanding Metal-Organic Frameworks and Their Derivatives: An Emerging Platform for Electrochemical Energy Storage and Conversion.

Metal-organic frameworks (MOFs) have recently emerged as ideal electrode materials and precursors for electrochemical energy storage and conversion (EESC) owing to their large specific surface areas, highly tunable porosities, abundant active sites, and diversified choices of metal nodes and organic linkers. Both MOF-based and MOF-derived materials in powder form have been widely investigated in relation to their synthesis methods, structure and morphology controls, and performance advantages in targeted applications. However, to engage them for energy applications, both binders and additives would be required to form postprocessed electrodes, fundamentally eliminating some of the active sites and thus degrading the superior effects of the MOF-based/derived materials. The advancement of freestanding electrodes provides a new promising platform for MOF-based/derived materials in EESC thanks to their apparent merits, including fast electron/charge transmission and seamless contact between active materials and current collectors. Benefiting from the synergistic effect of freestanding structures and MOF-based/derived materials, outstanding electrochemical performance in EESC can be achieved, stimulating the increasing enthusiasm in recent years. This review provides a timely and comprehensive overview on the structural features and fabrication techniques of freestanding MOF-based/derived electrodes. Then, the latest advances in freestanding MOF-based/derived electrodes are summarized from electrochemical energy storage devices to electrocatalysis. Finally, insights into the currently faced challenges and further perspectives on these feasible solutions of freestanding MOF-based/derived electrodes for EESC are discussed, aiming at providing a new set of guidance to promote their further development in scale-up production and commercial applications.

Advanced Multifunctional Aqueous Rechargeable Batteries Design: From Materials and Devices to Systems.

Multifunctional aqueous rechargeable batteries (MARBs) are regarded as safe, cost-effective, and scalable electrochemical energy storage devices, which offer additional functionalities that conventional batteries cannot achieve, which ideally leads to unprecedented applications. Although MARBs are among the most exciting and rapidly growing topics in scientific research and industrial development nowadays, a systematic summary of the evolution and advances in the field of MARBs is still not available. Therefore, the review presented comprehensively and systematically summarizes the design principles and the recent advances of MARBs by categories of smart ARBs and integrated systems, together with an analysis of their device design and configuration, electrochemical performance, and diverse smart functions. The two most promising strategies to construct novel MARBs may be A) the introduction of functional materials into ARB components, and B) integration of ARBs with other functional devices. The ongoing challenges and future perspectives in this research and development field are outlined to foster the future development of MARBs. Finally, the most important upcoming research directions in this rapidly developing field are highlighted that may be most promising to lead to the commercialization of MARBs and to a further broadening of their range of applications.

Flexible Tactile Sensor Based on Patterned Ag-Nanofiber Electrodes through Electrospinning.

The growing demand for intelligent equipment has greatly inspired the development of flexible devices. Thus, disparate flexible multifunctional devices, including pressure sensitive flexible/stretchable displays, have drawn worldwide research attention. Electrodes maintaining conductivity and mechanical strength against deformations are indispensable components in all prospective applications. In this work, a flexible pressure mapping sensor array is developed based on patterned Ag-nanofibers (Ag-NFs) electrode through electrospinning and lithography. The metallic Ag layer is sputtered onto the electrospinning polyvinyl alcohol (PVA) NFs. A uniform and super conductive electrode layer with outstanding mechanical performance is thus formed after dissolving PVA. Followed by the traditional lithography method, a patterned electrode array (4 × 4 sensors) is obtained. Based on the newly developed triboelectric nanogenerator (TENG) technology, a flexible pressure-mapping sensor with excellent stability towards bending deformations is further demonstrated. Moreover, a letter "Z" is successfully visualized by this pressure sensor array, encouraging more human-machine interactive implementations, such as multi-functional tactile screens.

Self-powered multifunctional sensing based on super-elastic fibers by soluble-core thermal drawing.

The well-developed preform-to-fiber thermal drawing technique owns the benefit to maintain the cross-section architecture and obtain an individual micro-scale strand of fiber with the extended length up to thousand meters. In this work, we propose and demonstrate a two-step soluble-core fabrication method by combining such an inherently scalable manufacturing method with simple post-draw processing to explore the low viscosity polymer fibers and the potential of soft fiber electronics. As a result, an ultra-stretchable conductive fiber is achieved, which maintains excellent conductivity even under 1900% strain or 1.5 kg load/impact freefalling from 0.8-m height. Moreover, by combining with triboelectric nanogenerator technique, this fiber acts as a self-powered self-adapting multi-dimensional sensor attached on sports gears to monitor sports performance while bearing sudden impacts. Next, owing to its remarkable waterproof and easy packaging properties, this fiber detector can sense different ion movements in various solutions, revealing the promising applications for large-area undersea detection.

Designer patterned functional fibers via direct imprinting in thermal drawing.

Creating micro/nanostructures on fibers is beneficial for extending the application range of fiber-based devices. To achieve this using thermal fiber drawing is particularly important for the mass production of longitudinally uniform fibers up to tens of kilometers. However, the current thermal fiber drawing technique can only fabricate one-directional micro/nano-grooves longitudinally due to structure elongation and polymer reflow. Here, we develop a direct imprinting thermal drawing (DITD) technique to achieve arbitrarily designed surface patterns on entire fiber surfaces with high resolution in all directions. Such a thermal imprinting process is simulated and confirmed experimentally. Key process parameters are further examined, showing a process feature size as small as tens of nanometers. Furthermore, nanopatterns are fabricated on fibers as plasmonic metasurfaces, and double-sided patterned fibers are produced to construct self-powered wearable touch sensing fabric, revealing the bright future of the DITD technology in multifunctional fiber-based devices, wearable electronics, and smart textiles.

High-Performance and Ultraflexible Aqueous Rechargeable Lithium-Ion Batteries Developed by Constructing All Binder-free Electrode Materials.

Aqueous rechargeable lithium-ion batteries (ARLIBs) as alternative energy storage devices have attracted tremendous attention because of their low cost and high safety. However, it is still a significant challenge to develop flexible high-performance ARLIBs for powering wearable devices because of the lack of all binder-free electrode materials. In this study, we develop one-step hydro-/solvothermal methods to design binder-free electrodes of LiCoO2 polygonal-sheeted arrays and rugby ball-shaped NaTi2(PO4)3 on carbon nanotube fibers as the cathode (LCO@CNTF) and the anode (NTP@CNTF). Both the electrodes are prepared at low temperatures without an extra calcination process, which is a great improvement for the growth process. The electrodes deliver remarkable capacity and extraordinary rate performance in a saturated Li2SO4 solution. Meanwhile, because of the synergy of LCO@CNTF and NTP@CNTF, an impressive capacity of 45.24 mA h cm-3 and an admirable energy density of 67.86 mW h cm-3 are achieved for the assembled quasi-solid-state fiber-shaped flexible ARLIB (FARLIB), which outperform most reported fiber-shaped aqueous rechargeable batteries. More encouragingly, our FARLIB possesses good flexibility, with a 94.74% capacity retention after bending 3000 times. Thus, this work represents a significant step toward developing FARLIBs and provides a new prospect in the design of wearable energy storage devices.