Skin-touch-actuated textile-based triboelectric nanogenerator with black phosphorus for durable biomechanical energy harvesting

Integration of two-dimensional WS2 in flexible textile triboelectric nanogenerators via electronic dyeing for self-powered sensing

We present flexible textile triboelectric nanogenerators by electronically dyeing polyester with two-dimensional tungsten disulfide (2D WS2), thereby enhancing its triboelectric properties when paired with nylon. Drop casting, immersion, and spray coating were evaluated, demonstrating their effectiveness in tailoring the fabric's triboelectric properties, showcasing 2D WS2's potential for self-powered sensors and energy-harvesting applications.

Metal-Organic Framework-Based Tribovoltaic Textile for Human Body Signal Monitoring

The pursuit of sustainable and portable direct current (DC) energy suppliers has ignited considerable interest in tribovoltaic nanogenerators (TVNGs), devices that harvest mechanical energy from the surrounding environment. However, the predominant focus in TVNG research has centered on rigid and silicon-based semiconductors that lack flexibility and are thus ill-suited for integration into common fabrics. Herein, a fully-textile TVNG with a simple design is introduced that enables the real-time monitoring of human physiological signals. The utilization of copper-benzenehexathiol (Cu-BHT), a conductive 2D metal-organic framework is proposed as a p-type semiconductor grown on fabric surfaces. The developed tribovoltaic textile (TVT) consists of Cu-BHT-modified cotton and metallic aluminum textile producing pure DC output due to self-rectification. With excellent flexibility and stability, Cu-BHT TVT is seamlessly integrated into textile-based accessories for continuous monitoring of human motion and respiration.

Interpretable Machine Learning for Evaluating Nanogenerators' Structural Design

The limited battery life in modern mobile, wearable, and implantable electronics critically constrains their operational longevity and continuous use. Consequently, as a self-powered technology, triboelectric nanogenerators (TENGs) have emerged as a promising solution to this. Traditional approaches for evaluating TENG structural design typically require manual, repetitive, time-consuming, and high-cost finite element modeling or experiments. To overcome this bottleneck, we developed a fully automated platform that leverages machine learning (ML) techniques. Our framework contains an artificial neuron network-based surrogate model that can provide accurate and reliable performance predictions for any structural parameters and a TreeSHAP interpretable ML model that can generate precise global and local insights for TENG structural parameters. Our platform shows broad adaptability to multiple TENG structures. In summary, our platform is an integrated platform that utilizes interpretable ML techniques to solve the complex multidimensional TENG structural evaluation problem, marking a significant advancement in TENG design and supporting sustainable energy solutions in mobile electronics.

Graphene-Based Vitrimeric Ink with Self-Healing Properties Enables Simple E-Textile Triboelectric Coating Development

Advances in research in electronic textiles (E-textiles) that primarily cater to wearable sensing technology have found amalgamation with self-powered technology, especially with triboelectric nanogenerators (TENGs). However, developing E-textiles with triboelectric properties involves a multi-step process and a complex device structure, which is unsuitable for actual wearables. Also, the cellulose-based fabrics with the highest wearability are unsuitable for TENG fabrication, limiting the usage to synthetic fabrics. Apart from wearability, self-healing behavior is another significant property recently being looked upon for wearable sensors, providing long-term functionality. Herein, a simple yet effective approach is proposed to develop dielectrically optimized coatings for developing cellulose fabric-based self-powered sensors by leveraging elastomers with tunable dielectric and other properties, otherwise catering to the domain of electronic skin separately. The record high output performance with a power density of 4.69 W m-2 accomplished using a single fabric layer with a thickness of 0.56 mm supports the amalgamation of dielectrically optimized elastomeric coatings with textiles for next-generation self-powered wearables. Also, the strategic utilization of dynamic covalent chemistry imparted self-healing properties to the coating. This report provides a single-step dip coating method for developing a self-powered and self-healable next-generation E-textile.

Cellulose-Templated Nanomaterials for Nanogenerators and Self-Powered Sensors

Energy crisis inspires the development of renewable and clean energy sources, along with related applications such as nanogenerators and self-powered devices. Balancing high performance and environmental sustainability in advanced material innovation is a challenging task. Addressing the global challenges of sustainable development and carbon neutrality lead to increased interest in biopolymer research. Nanocellulose materials, derived from biopolymers, demonstrate potential as template candidates for advanced materials, due to their unique properties, including high strength, high surface area, controllable pore structures and high-water retention. In recent years, cellulose-templated nanomaterials enable delicate nano-/microscale structural construction, thus promoting developments in the field of nanogenerators and self-powered sensors. However, there is still a limited number of reviews focused on cellulose-templated nanomaterials for applications in nanogenerators and self-powered sensors. This review aims to fill this research gap by introducing various cellulose-templated nanomaterials and providing a detailed analysis of their fashionable applications in nanogenerators and self-powered sensors. The goal is to present cellulose-templated nanomaterials as highly promising template and guest materials for templating technologies, offering sustainable nano-/microscale control over advanced materials for the foreseeable future. This potential is promising for new applications in the fields of nanogenerators and self-powered sensors.

Efficient Permeable Monolithic Hybrid Tribo-Piezo-Electromagnetic Nanogenerator Based on Topological-Insulator-Composite

Escalating energy demands of self-independent on-skin/wearable electronics impose challenges on corresponding power sources to offer greater power density, permeability, and stretchability. Here, a high-efficient breathable and stretchable monolithic hybrid triboelectric-piezoelectric-electromagnetic nanogenerator-based electronic skin (TPEG-skin) is reported via sandwiching a liquid metal mesh with two-layer topological insulator-piezoelectric polymer composite nanofibers. TPEG-skin concurrently extracts biomechanical energy (from body motions) and electromagnetic radiations (from adjacent appliances), operating as epidermal power sources and whole-body self-powered sensors. Topological insulators with conductive surface states supply notably enhanced triboelectric and piezoelectric effects, endowing TPEG-skin with a 288 V output voltage (10 N, 4 Hz), ∼3 times that of state-of-the-art devices. Liquid metal meshes serve as breathable electrodes and extract ambient electromagnetic pollution (±60 V, ±1.6 µA cm-2). TPEG-skin implements self-powered physiological and body motion monitoring and system-level human-machine interactions. This study provides compatible energy strategies for on-skin/wearable electronics with high power density, monolithic device integration, and multifunctionality.

Highly Stretchable Composite Conductive Fibers (SCCFs) and Their Applications

Stretchable composite conductive fibers (SCCFs) exhibit remarkable conductivity, stretchability, breathability, and biocompatibility, making them ideal candidates for wearable electronics and bioelectronics. The exploitation of SCCFs in electronic devices requires a careful balance of many aspects, including material selection and process methodologies, to address the complex challenges associated with their electrical and mechanical properties. In this review, we elucidate the conductive mechanism of SCCFs and summarize strategies for integrating various conductors with stretchable fibers, emphasizing the primary challenges in fabricating highly conductive fibers. Furthermore, we explore the multifaceted applications of SCCFs-based frameworks in wearable electronic devices. This review aims to emphasize the significance of SCCFs and offers insights into their conductive mechanisms, material selection, manufacturing technologies, and performance improvement. Hopefully, it can guide the innovative development of SCCFs and broaden their application potential.

Recent Advances in Wearable Textile-Based Triboelectric Nanogenerators

We review recent results on textile triboelectric nanogenerators (T-TENGs), which function both as harvesters of mechanical energy and self-powered motion sensors. T-TENGs can be flexible, breathable, and lightweight. With a combination of traditional and novel manufacturing methods, including nanofibers, T-TENGs can deliver promising power output. We review the evolution of T-TENG device structures based on various textile material configurations and fabrication methods, along with demonstrations of self-powered systems. We also provide a detailed analysis of different textile materials and approaches used to enhance output. Additionally, we discuss integration capabilities with supercapacitors and potential applications across various fields such as health monitoring, human activity monitoring, human-machine interaction applications, etc. This review concludes by addressing the challenges and key research questions that remain for developing viable T-TENG technology.

Carbon Nanotube Sheets/Elastomer Bilayer Harvesting Electrode with Biaxially Generated Electrical Energy

Mechanical energy harvesters made from soft and flexible materials can be employed as energy sources for wearable and implantable devices. However, considering how human organs and joints expand and bend in many directions, the energy generated in response to a mechanical stimulus in only one direction limits the applicability of mechanical energy harvesters. Here, we report carbon nanotube (CNT) sheets/an elastomer bilayer harvesting electrode (CBHE) that converts two-axis mechanical stimulation into electrical energy. The novel microwinkled structure of the CBHE successfully demonstrates an electrochemical double-layer (EDL) capacitance change from biaxial mechanical stimulation, thereby generating electrical power (0.11 W kg-1). Additionally, the low modulus (0.16 MPa) and high deformability due to the elastomeric substrate suggest that the CBHE can be applied to the human body.

Visualization and standardized quantification of surface charge density for triboelectric materials

Triboelectric nanogenerator (TENG) operates on the principle of utilizing contact electrification and electrostatic induction. However, visualization and standardized quantification of surface charges for triboelectric materials remain challenging. Here, we report a surface charge visualization and standardized quantification method using electrostatic surface potential measured by Kevin probe and the iterative regularization strategy. Moreover, a tuning strategy on surface charge is demonstrated based on the corona discharge with a three-electrode design. The long-term stability and dissipation mechanisms of the injected negative or positive charges demonstrate high dependence on deep carrier traps in triboelectric materials. Typically, we achieved a 70-fold enhancement on the output voltage (~135.7 V) for the identical polytetrafluoroethylene (PTFE) based TENG (neg-PTFE/PTFE or posi-PTFE/PTFE triboelectric pair) with stable surface charge density (5% decay after 140 days). The charged PTFE was demonstrated as a robot e-skins for non-contact perception of object geometrics. This work provides valuable tools for surface charge visualization and quantification, giving a new strategy for a deeper understanding of contact electrification.

Zebra-Patterned Stretchable Helical Yarn for Triboelectric Self-Powered Multifunctional Sensing

Smart textiles capable of both energy harvesting and multifunctional sensing are highly desirable for next-generation portable electronics. However, there are still challenges that need to be conquered, such as the innovation of an energy-harvesting model and the optimization of interface bonding between fibers and active materials. Herein, inspired by the spiral structure of natural vines, a highly stretchable triboelectric helical yarn (TEHY) was manufactured by twisting the carbon nanotube/polyurethane nanofiber (CNT/PU NF) Janus membrane. The TEHY had a zebra-stripe-like design that was composed of black interval conductive CNTs and white insulative PU NFs. Due to the different electron affinity, the zebra-patterned TEHY realized a self-frictional triboelectric effect because the numerous microscopic CNT/PU triboelectric interfaces generated an alternating current in the external conductive circuit without extra external friction layers. The helical geometry combined with the elastic PU matrix endowed TEHY with superelastic stretchability and outstanding output stability after 1000 cycles of the stretch-release test. By virtue of the robust mechanical and electrical stability, the TEHY can not only be used as a high-entropy mechanical energy harvester but also serve as a self-powered sensor to monitor the stretching or deforming stimuli and human physiological activities in real time. These merits manifested the versatile applications of TEHY in smart fabrics, wearable power supplies, and human-machine interactions.

Flexible and Ultra Low Weight Energy Harvesters Based on 2D Phosphorene or Black phosphorus (BP): Current and Futuristic Prospects

Phosphorene, or two-dimensional (2D) black phosphorus, has recently emerged as a competitor of graphene as it offers several advantages, including a tunable band gap, higher on/off current ratio, piezoelectric nature, and biocompatibility. Researchers have succeeded in obtaining several forms of phosphorene, such as nanosheets, nanorods, nanoribbons, and quantum dots, with satisfactory yields. Nanostructures with various controlled properties have been fabricated in multiple devices for energy production. These phosphorene-based devices are lightweight, flexible, and efficient, demonstrating great potential for energy-harvesting applications in sensors and nanogenerators. While ongoing exploration and advancements continue for these lightweight energy harvesters, it is essential to review the current progress in order to develop a future roadmap for the potential use of these phosphorene-based energy harvesters in space programs. They could be employed in applications such as wearable devices for astronauts, where ultralow weight is a vital component of any integrated device. This review also anticipates the growing significance of phosphorene in various emerging applications such as robots, information storage devices, and artificial intelligence.

Wearable, Machine Washable, Breathable Polyethylenimine/Sodium Alginate Layer-by-Layer-Coated Cotton-Based Multifunctional Triboelectric Nanogenerators

Cotton-based textiles are ubiquitous in daily life and are prime candidates for application in wearable triboelectric nanogenerators. However, pristine cotton is vulnerable to bacterial attack, lacks antioxidant and ultraviolet (UV)-protective abilities, and shows lower triboelectric charge generation against tribonegative materials because it is present in the neutral region of the triboelectric series. To overcome such drawbacks, herein, a facile layer-by-layer method is proposed, involving the deposition of alternate layers of polyethylenimine (PEI) and sodium alginate (SA) on cotton. Such modified fabric remains breathable and flexible, retains its comfort properties, and simultaneously shows multifunctionalities and improved triboelectric output, which are retained even after 50 home laundering cycles. Also, the modified fabric becomes more tribopositive than nylon, silk, and wool. A triboelectric nanogenerator consisting of modified cotton and polyester fabric is proposed that shows a maximum power density of 338 mW/m2. An open-circuit voltage of ∼97.3 V and a short-circuit current of ∼4.59 μA are obtained under 20 N force and 1 Hz tapping frequency. Further, the modified cotton exhibits excellent antibacterial, antioxidant, and UV-protective properties because of the incorporation of PEI, and its moisture management properties are retained due to the presence of sodium alginate in the layer. This study provides a simple yet effective approach to obtaining durable multifunctionalities and improved triboelectric performance in cotton substrates.

Autonomous Triboelectric Smart Textile Sensor for Vital Sign Monitoring

Wearable smart textile sensors for monitoring vital signs are fast, noninvasive, and highly desirable for personalized health management to diagnose health anomalies such as cardiovascular diseases and respiratory dysfunction. Traditional biosignal sensors, with power consumption issues, constrain the use of wearable medical devices. This study introduces an autonomous triboelectric smart textile sensor (AUTS) made of reduced graphene oxide/manganese dioxide/polydimethylsiloxane (RGO-M-PDMS) and polytetrafluoroethylene (TEFLON)-knitted silver electrode, offering promise for vital sign monitoring with self-powering, flexibility, and wearability. The sensor exhibits impressive output performance, with a sensitivity of 7.8 nA/kPa, response time of ≈40 ms, good stability of >15,000 cycles, stretchability of up to 40%, and machine washability of >20 washes. The AUTS has been integrated to the TriBreath respiratory belt for monitoring respiratory signals and pulse strap for pulse signals concurrently at different body pulse points. These sensors wirelessly transmitted the acquired biosignals to a smartphone, demonstrating the potential of a self-powered and real-time vital sign monitoring system.

Achieving Self-Reinforcing Triboelectric-Electromagnetic Hybrid Nanogenerator by Magnetocaloric and Magnetization Effects of Gadolinium

Triboelectric-electromagnetic hybrid nanogenerator (TEHG) has emerged as a promising technology for distributed energy harvesting. However, currently reported hybrid generators are straightforward combinations of two functional components. Moreover, inevitable heat from friction intensifies material abrasion and degrades the performance of polymer-based triboelectric nanogenerators (TENGs). Here, a self-reinforcing TEHG (SR-TEHG) that harnesses the magnetocaloric and magnetization effects of gadolinium (Gd), is proposed. The synergy between TENG and electromagnetic generator (EMG) renders them an indivisible unit. Leveraging Gd's magnetocaloric effect, an efficient heat transfer mechanism is constructed to cool the tribolayer and strengthen the device's electrical stability. After 80 h of continuous operation, the optimized TENG occupies a charge decay rate of only 0.32% per hour, significantly outperforming most existing TENGs. Additionally, Gd's magnetization effect boosts the power of EMG by ≈80.84%. This work provides a universal solution in hybrid generators where internal components reinforce each other, achieving a synergistic effect of 1 + 1 > 2.

Improved Electrical Output Performance of Cellulose-Based Triboelectric Nanogenerators Enabled by Negative Triboelectric Materials

Cellulose-based triboelectric nanogenerators (TENGs) have attracted widespread attention due to the low cost and environmentally friendly characteristics of cellulose. However, achieving high electrical energy output from these generators still presents significant challenges. Here, cellulose is dissolved-regenerated to form a composite aerogel with high specific surface area, in which cellulose-based composites with excellent negative triboelectric properties are developed by coupling the rich 3D network structure of the regenerated cellulose aerogel, modified barium titanate, and poly(vinylidene fluoride). The TENGs assembled from the composite materials exhibit an output voltage of 1040 V and a current of 1.165 mA at an external force of 8 N and a frequency of 4 Hz, outperforming all cellulose-based negative triboelectric materials. In addition, the nanogenerators have a stable electrical energy output capacity, with no significant property degradation in 100 000 contact-separation tests. The excellent electrical output property of the composite materials enables them to harvest energy from human movement and waterdrops, demonstrating their great application prospects in wearable devices, energy harvesting devices, self-powered sensors, and other fields.

A three-dimensional liquid diode for soft, integrated permeable electronics

Wearable electronics with great breathability enable a comfortable wearing experience and facilitate continuous biosignal monitoring over extended periods1-3. However, current research on permeable electronics is predominantly at the stage of electrode and substrate development, which is far behind practical applications with comprehensive integration with diverse electronic components (for example, circuitry, electronics, encapsulation)4-8. Achieving permeability and multifunctionality in a singular, integrated wearable electronic system remains a formidable challenge. Here we present a general strategy for integrated moisture-permeable wearable electronics based on three-dimensional liquid diode (3D LD) configurations. By constructing spatially heterogeneous wettability, the 3D LD unidirectionally self-pumps the sweat from the skin to the outlet at a maximum flow rate of 11.6 ml cm-2 min-1, 4,000 times greater than the physiological sweat rate during exercise, presenting exceptional skin-friendliness, user comfort and stable signal-reading behaviour even under sweating conditions. A detachable design incorporating a replaceable vapour/sweat-discharging substrate enables the reuse of soft circuitry/electronics, increasing its sustainability and cost-effectiveness. We demonstrated this fundamental technology in both advanced skin-integrated electronics and textile-integrated electronics, highlighting its potential for scalable, user-friendly wearable devices.

High-Performance All-Textile Triboelectric Nanogenerator toward Intelligent Sports Sensing and Biomechanical Energy Harvesting

Merging textiles with advanced energy harvesting technology via triboelectric effects brings novel insights into self-powered wearable textile electronics. However, fabrication of a comfortable textile-based triboelectric nanogenerator (TENG) with high outputs remains challenging. Herein, we propose a highly flexible, tailorable, single-electrode all-textile TENG (t-TENG) with both wear comfort and high outputs. A dielectric modulated porous composite coating containing poly(vinylidene fluoride)-hexafluoropropylene copolymer and barium titanate nanoparticles is constructed on conductive fabric to counterpart with highly positive glass fiber fabric through knotted yarn bonding, maintaining the superiority of textiles and strong triboelectricity. Through the synergistic optimization of charge storage via dielectric modulation and charge dissipation offset by electrical poling, remarkable outputs (261 V, 1.5 μA, and 12.7 nC) are obtained from a miniaturized, lightweight t-TENG (2 × 2 cm2, 130 mg) with an instantaneous power density of 654.48 mW·m-2, as well as excellent electrical robustness and device durability over 20,000 cycles. The t-TENG also exhibits a high sensitivity of 3.438 V·kPa-1 in the force region (1-10 N), demonstrating great potential in TENG-based intelligent sports sensing applications for monitoring and correcting the basketball shooting hand and foot arch posture. Furthermore, over 110 light-emitting diode arrays can be lightened up by gently tapping this miniaturized t-TENG. It also offers a wearable power source scheme through integrating the single-electrode device into clothing and utilizing the skin as the grounded electrode, revealing its ease of integration and biomechanical energy harvesting capability. This work provides an attractive paradigm for next-generation textile electronics with well-balanced device performance and wear comfort.

Environmental and Health Impacts of Graphene and Other Two-Dimensional Materials: A Graphene Flagship Perspective

Two-dimensional (2D) materials have attracted tremendous interest ever since the isolation of atomically thin sheets of graphene in 2004 due to the specific and versatile properties of these materials. However, the increasing production and use of 2D materials necessitate a thorough evaluation of the potential impact on human health and the environment. Furthermore, harmonized test protocols are needed with which to assess the safety of 2D materials. The Graphene Flagship project (2013-2023), funded by the European Commission, addressed the identification of the possible hazard of graphene-based materials as well as emerging 2D materials including transition metal dichalcogenides, hexagonal boron nitride, and others. Additionally, so-called green chemistry approaches were explored to achieve the goal of a safe and sustainable production and use of this fascinating family of nanomaterials. The present review provides a compact survey of the findings and the lessons learned in the Graphene Flagship.

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.

Boosting the output performance of triboelectric nanogenerators via surface engineering and structure designing

Triboelectric nanogenerators (TENGs) have been utilized in a wide range of applications, including smart wearable devices, self-powered sensors, energy harvesting, and high-voltage power sources. The surface morphology and structure of TENGs play a critical role in their output performance. In this review, we analyze the working mechanism of TENGs with the aim to improve their output performance and systematically summarize the morphological engineering and structural design strategies for TENGs. Additionally, we present the emerging applications of TENGs with specific structures and surfaces. Finally, we discuss the potential future development and industrial application of TENGs. By deeply exploring the surface and structural design strategy of high-performance TENGs, it is conducive to further promote the application of TENGs in actual production. We hope that this review provides insights and guidance for the morphological and structural design of TENGs in the future.

Construction of Triboelectric Series and Chirality Detection of Amino Acids Using Triboelectric Nanogenerator

Triboelectrification necessitates a frictional interaction between two materials, and their contact electrification is characteristically based on the polarity variance in the triboelectric series. Utilizing this fundamental advantage of the triboelectric phenomenon, different materials can be identified according to their contact electrification capability. Herein, an in-depth analysis of the amino acids present in the stratum corneum of human skin is performed and these are quantified regarding triboelectric polarization. The principal focus of this study lies in analyzing and identifying the amino acids present in copious amounts in the stratum corneum to explain their positive behavior during the contact electrification process. Thus, an augmented triboelectric series of amino acids with quantified triboelectric charging polarity by scrutinizing the transfer charge, work function, and atomic percentage is presented. Furthermore, the chirality of aspartic acid as it is most susceptible to racemization with clear consequences on the human skin is detected. The study is expected to accelerate research exploiting triboelectrification and provide valuable information on the surface properties and biological activities of these important biomolecules.

Contact efficiency optimization for tribovoltaic nanogenerators

Energy harvesters based on the tribovoltaic effect that can convert mechanical energy into electricity offer a potential solution for the energy supply of decentralized sensors. However, a substantial disparity in output current, exceeding 106 times, exists between micro- and macro-contact tribovoltaic nanogenerators (TVNGs). To tackle this challenge, we develop a quantification method to determine the effective contact efficiency of conventional large-scale TVNGs, revealing a mere 0.038% for a TVNG of 1 cm2. Thus, we implement an optimization strategy by contact interface design resulting in a remarkable 65-fold increase in effective contact efficiency, reaching 2.45%. This enhancement leads to a current density of 23 A m-2 and a record-high charge density of 660 mC m-2 for the TVNG based on Cu and p-type silicon. Our study reveals that increasing the effective contact efficiency will not only address the existing disparities but also have the potential to significantly enhance the output current in future advancements of large-scale TVNGs.

Recent Advances in Flexible Multifunctional Sensors

Wearable electronics have received extensive attention in human-machine interactions, robotics, and health monitoring. The use of multifunctional sensors that are capable of measuring a variety of mechanical or environmental stimuli can provide new functionalities for wearable electronics. Advancements in material science and system integration technologies have contributed to the development of high-performance flexible multifunctional sensors. This review presents the main approaches, based on functional materials and device structures, to improve sensing parameters, including linearity, detection range, and sensitivity to various stimuli. The details of electrical, biocompatible, and mechanical properties of self-powered sensors and wearable wireless systems are systematically elaborated. Finally, the current challenges and future developmental directions are discussed to offer a guide to fabricate advanced multifunctional sensors.

Porous Polymer Materials in Triboelectric Nanogenerators: A Review

Since the invention of the triboelectric nanogenerator (TENG), porous polymer materials (PPMs), with different geometries and topologies, have been utilized to enhance the output performance and expand the functionality of TENGs. In this review, the basic characteristics and preparation methods of various PPMs are introduced, along with their applications in TENGs on the basis of their roles as electrodes, triboelectric surfaces, and structural materials. According to the pore size and dimensionality, various types of TENGs that are built with hydrogels, aerogels, foams, and fibrous media are classified and their advantages and disadvantages are analyzed. To deepen the understanding of the future development trend, their intelligent and multifunctional applications in human-machine interfaces, smart wearable devices, and self-powering sensors are introduced. Finally, the future directions and challenges of PPMs in TENGs are explored to provide possible guidance on PPMs in various TENG-based intelligent devices and systems.

Easy-To-Wear Auxetic SMA Knot-Architecture for Spatiotemporal and Multimodal Haptic Feedbacks

Wearable haptic interfaces prioritize user comfort, but also value the ability to provide diverse feedback patterns for immersive interactions with the virtual or augmented reality. Here, to provide both comfort and diverse tactile feedback, an easy-to-wear and multimodal wearable haptic auxetic fabric (WHAF) is prepared by knotting shape-memory alloy wires into an auxetic-structured fabric. This unique meta-design allows the WHAF to completely expand and contract in 3D, providing superior size-fitting and shape-fitting capabilities. Additionally, a microscale thin layer of Parylene is coated on the surface to create electrically separated zones within the WHAF, featuring zone-specified actuation for conveying diverse spatiotemporal information to users with using the WHAF alone. Depending on the body part it is worn on, the WHAF conveys either cutaneous or kinesthetic feedback, thus, working as a multimodal wearable haptic interface. As a result, when worn on the forearm, the WHAF intuitively provides spatiotemporal information to users during hands-free navigation and teleoperation in virtual reality, and when worn on the elbow, the WHAF guides users to reach the desired elbow flexion, like a personal exercise advisor.

Fabrication of a textile-based triboelectric nanogenerator toward high-efficiency energy harvesting and material recognition

Textile-based triboelectric nanogenerator (T-TENG) devices, particularly, narrow-gap mode, have been conceived and developed for obtaining energy harvesting and tactile sensing devices unaffected by the external environment. Enhancing the interfacial area of T-TENG materials offers exciting opportunities to improve the device output performance. In this work, a narrow-gap T-TENG was fabricated with a facile process, and a new strategy for improving the device output is proposed. The new structural sensor (polydimethylsiloxane (PDMS)-encapsulated electroless copper plating (EP-Cu) cotton) with multiple electricity generation mechanism was designed and fabricated for enhancing recognition accuracy. The result shows that only PDMS layer strain was established at an external stress of 1.24-12.4 kPa and the fibers laterally slip at a stress of 12.4-139 kPa; more importantly, the output performance of the TENG displayed a linear relationship under corresponding stress ranges. The as-fabricated device demonstrated the ability to convert different energies such as vibration, raindrops, wind and human motions into electrical energy with excellent sensitivity. Interestingly, the output signal of the as-fabricated TENG device is a combination of output signals from PDMS/EP-Cu and PDMS/recognition object devices. To be precise, there are two TENG devices (PDMS/EP-Cu and PDMS/recognition object) that work when the as-fabricated TENG device is under 12.4-139 kPa stress. Accompanied by unique characteristics, the generated TENG signals are capable of recognition of contact materials. Combining the TENG signal and deep learning technology, we explore a strategy that can enable the as-fabricated device to recognize 8 different materials with 99.48% recognition accuracy in the natural environment.

Flexible triboelectric nanogenerators of Au-g-C3N4/ZnO hierarchical nanostructures for machine learning enabled body movement detection

Here we report the development of triboelectric nanogenerator (TENG) based self-powered human motion detector with chemically developed Au-g-C3N4/ZnO based nanocomposite on common cellulose paper platform. Compared to bare g-C3N4, the nanocomposite in the form of hierarchical morphology is found to exhibit higher output voltage owing to the contribution of Au and ZnO in increasing the dielectric constant and surface roughness. While generating power ∼3.5μW cm-2and sensitivity ∼3.3 V N-1, the flexible TENG, is also functional under common biomechanical stimuli to operate as human body movement sensor. When attached to human body, the flexible TENG is found to be sensitive towards body movement as well as the frequency of movement. Finally upon attaching multiple TENG devices to human body, the nature of body movement has been traced precisely using machine learning (ML) techniques. The execution of the learning algorithms like artificial neural network and random forest classifier on the data generated from these multiple sensors can yield an accuracy of 99% and 100% respectively to predict body movement with great deal of precision. The exhibition of superior sensitivity and ML based biomechanical motion recognition accuracy by the hierarchical structure based flexible TENG sensor are the prime novelties of the work.

Renaissance of elemental phosphorus materials: properties, synthesis, and applications in sustainable energy and environment

The polymorphism of phosphorus-based materials has garnered much research interest, and the variable chemical bonding structures give rise to a variety of micro and nanostructures. Among the different types of materials containing phosphorus, elemental phosphorus materials (EPMs) constitute the foundation for the synthesis of related compounds. EPMs are experiencing a renaissance in the post-graphene era, thanks to recent advancements in the scaling-down of black phosphorus, amorphous red phosphorus, violet phosphorus, and fibrous phosphorus and consequently, diverse classes of low-dimensional sheets, ribbons, and dots of EPMs with intriguing properties have been produced. The nanostructured EPMs featuring tunable bandgaps, moderate carrier mobility, and excellent optical absorption have shown great potential in energy conversion, energy storage, and environmental remediation. It is thus important to have a good understanding of the differences and interrelationships among diverse EPMs, their intrinsic physical and chemical properties, the synthesis of specific structures, and the selection of suitable nanostructures of EPMs for particular applications. In this comprehensive review, we aim to provide an in-depth analysis and discussion of the fundamental physicochemical properties, synthesis, and applications of EPMs in the areas of energy conversion, energy storage, and environmental remediation. Our evaluations are based on recent literature on well-established phosphorus allotropes and theoretical predictions of new EPMs. The objective of this review is to enhance our comprehension of the characteristics of EPMs, keep abreast of recent advances, and provide guidance for future research of EPMs in the fields of chemistry and materials science.

Recent Advances in the Biological Responses to Nano-black Phosphorus: Understanding the Importance of Intrinsic Properties and Cell Types

The production scalability and increasing demand for nano-black phosphorus materials (nano-BPs) inevitably lead to their environmental leakage, thereby raising the risk of human exposure through inhalation, ingestion, dermal, and even intravenous pathways. Consequently, a systematic evaluation of their potential impacts on human health is necessary. This Review outlines recent progress in the understanding of various biological responses to nano-BPs. Attention is particularly given to the inconsistent toxicological findings caused by a wide variation of nano-BPs' physicochemical properties, toxicological testing methods, and cell types examined in each study. Additionally, cellular uptake and intracellular trafficking, cell death modes, immunological effects, and other biologically relevant processes are discussed in detail, providing evidence for the potential health implications of nano-BPs. Finally, we address the remaining challenges related to the health risk evaluation of nano-BPs and propose a broader range of applications for these promising nanomaterials.

Flexible triboelectric nanogenerators using transparent copper nanowire electrodes: energy harvesting, sensing human activities and material recognition

Triboelectric nanogenerators (TENGs) have emerged as a promising green technology to efficiently harvest otherwise wasted mechanical energy from the environment and human activities. However, cost-effective and reliably performing TENGs require rational integration of triboelectric materials, spacers, and electrodes. The present work reports for the first time the use of oxydation-resistant pure copper nanowires (CuNWs) as an electrode to develop a flexible, and inexpensive TENG through a potentially scalable approach involving vacuum filtration and lactic acid treatment. A ∼6 cm2 device yields a remarkable open circuit voltage (Voc) of 200 V and power density of 10.67 W m-2 under human finger tapping. The device is robust, flexible and noncytotoxic as assessed by stretching/bending maneuvers, corrosion tests, continuous operation for 8000 cycles, and biocompatibility tests using human fibroblast cells. The device can power 115 light emitting diodes (LEDs) and a digital calculator; sense bending and motion from the human hand; and transmit Morse code signals. The robustness, flexibility, transparency, and non-cytotoxicity of the device render it particularly promising for a wide range of energy harvesting and advanced healthcare applications, such as sensorised smart gloves for tactile sensing, material identification and safer surgical intervention.

Electron Transfer in Contact Electrification under Different Atmospheres Packaged inside TENG

Contact electrification (CE), a common physical phenomenon, is worth discussing. However, there are few reports on the influence of atmosphere on CE, or on the performance of triboelectric nanogenerators (TENG), based on CE by encapsulating gas inside. Here, we propose physical processes of electron transfer to interpret the impact of the gaseous atmosphere on CE. An atmosphere-filled triboelectric nanogenerator (AF-TENG) encapsulated five different gas-components of air based on the vertical contact separation mode was prepared. The sensitivity (1.02 V·N^-1) and the power density (9.63 μW·m^-2) of the oxygen-atmosphere-filled AF-TENG were 229.03% and 157.81% higher than these (0.31 V·N^-1 and 3.84 μW·m^-2) of the nitrogen-atmosphere-filled AF-TENG. As the oxygen atom possesses more atomic energy levels than other atoms, this could act as a "bridge" for more electrons to directly transfer between the two materials. The device package under different atmospheres could not only strengthen understanding of CE and improve the performance of TENG, but also be potentially applicable to prevent and control unnecessary damage caused by static electricity.

Influence of phase-separated structural morphologies on the piezo and triboelectric properties of polymer composites

Simplified and flexible fabrication methods, high output performance, and extreme flexibility of polymer-based nanocomposites represent versatile designs in self-powering devices for wearable electronics, sensors, and smart societies. Examples include polyvinylidene fluoride and its copolymers-based piezoelectric nanogenerators, green and recyclable triboelectric nanogenerators, etc. Advanced functionalities, multi-functional properties, and the extensive lifetime required for nanogenerators inspire researchers to focus on structural modifications of the polymeric materials, to fully exploit their performances. Phase separation is a physicochemical process in which polymeric phases rearrange, resulting in specific structures and properties, that ultimately influence mechanical, electronic, and other functional properties. This article will study the phase separation strategies used to modify the polymeric base, both physically and chemically, to generate the maximum electric power upon mechanical and frictional deformation. The effect of interfacial modification on the efficiency of the nanogenerators, chemical and mechanical stability, structural integrity, durable performance, and morphological appearance will be extensively covered in this review. Moreover, piezo- and triboelectric power generation have numerous challenges, such as poor resistance to mechanical deformation, reduced cyclic performance stability, and a high cost of production. These often depend on the method of developing the nanogenerators, and phase separation provides a unique advantage in reducing them. The current review provides a one-stop solution to understand and disseminate the phase separation process, types and mechanisms, advantages, and role in improving the piezoelectric and triboelectric performances of the nanogenerators.

Recent Advances in Triboelectric Nanogenerators: From Technological Progress to Commercial Applications

Serious climate changes and energy-related environmental problems are currently critical issues in the world. In order to reduce carbon emissions and save our environment, renewable energy harvesting technologies will serve as a key solution in the near future. Among them, triboelectric nanogenerators (TENGs), which is one of the most promising mechanical energy harvesters by means of contact electrification phenomenon, are explosively developing due to abundant wasting mechanical energy sources and a number of superior advantages in a wide availability and selection of materials, relatively simple device configurations, and low-cost processing. Significant experimental and theoretical efforts have been achieved toward understanding fundamental behaviors and a wide range of demonstrations since its report in 2012. As a result, considerable technological advancement has been exhibited and it advances the timeline of achievement in the proposed roadmap. Now, the technology has reached the stage of prototype development with verification of performance beyond the lab scale environment toward its commercialization. In this review, distinguished authors in the world worked together to summarize the state of the art in theory, materials, devices, systems, circuits, and applications in TENG fields. The great research achievements of researchers in this field around the world over the past decade are expected to play a major role in coming to fruition of unexpectedly accelerated technological advances over the next decade.

Transparent Pneumatic Tactile Sensors for Soft Biomedical Robotics

Palpation is a simple but effective method to distinguish tumors from healthy tissues. The development of miniaturized tactile sensors embedded on endoscopic or robotic devices is key to achieving precise palpation diagnosis and subsequent timely treatment. This paper reports on the fabrication and characterization of a novel tactile sensor with mechanical flexibility and optical transparency that can be easily mounted on soft surgical endoscopes and robotics. By utilizing the pneumatic sensing mechanism, the sensor offers a high sensitivity of 1.25 mbar and negligible hysteresis, enabling the detection of phantom tissues with different stiffnesses ranging from 0 to 2.5 MPa. Our configuration, combining pneumatic sensing and hydraulic actuating, also eliminates electrical wiring from the functional elements located at the robot end-effector, thereby enhancing the system safety. The optical transparency path in the sensors together with its mechanical sensing capability open interesting possibilities in the early detection of solid tumor as well as in the development of all-in-one soft surgical robots that can perform visual/mechanical feedback and optical therapy.

Skin-Inspired Highly Sensitive Tactile Sensors with Ultrahigh Resolution over a Broad Sensing Range

Flexible tactile sensors with high sensitivity, a broad pressure detection range, and high resolution are highly desired for the applications of health monitoring, robots, and the human-machine interface. However, it is still challenging to realize a tactile sensor with high sensitivity and resolution over a wide detection range. Herein, to solve the abovementioned problem, we demonstrate a universal route to develop a highly sensitive tactile sensor with high resolution and a wide pressure range. The tactile sensor is composed of two layers of microstructured flexible electrodes with high modulus and conductive cotton fabric with low modulus. By optimizing the sensing films, the fabricated tactile sensor shows a high sensitivity of 8.9 × 10⁴ kPa^-1 from 2 Pa to 250 kPa because of the high structural compressibility and stress adaptation of the multilayered composite films. Meanwhile, a fast response speed of 18 ms, an ultrahigh resolution of 100 Pa over 100 kPa, and excellent durability over 20 000 loading/unloading cycles are demonstrated. Moreover, a 6 × 6 tactile sensor array is fabricated and shows promising potential application in electronic skin (e-skin). Therefore, employing multilayered composite films for tactile sensors is a novel strategy to achieve high-performance tactile perception in real-time health monitoring and artificial intelligence.

The Design and Development of Woven Textile Solar Panels

Over the past few years, alternative power supplies to either supplement or replace batteries for electronic textile and wearable applications have been sought, with the development of wearable solar energy harvesting systems gaining significant interest. In a previous publication the authors reported a novel concept to craft a yarn capable of harvesting solar energy by embedding miniature solar cells within the fibers of a yarn (solar electronic yarns). The aim of this publication is to report the development of a large-area textile solar panel. This study first characterized the solar electronic yarns, and then analyzed the solar electronic yarns once woven into double cloth woven textiles; as part of this study, the effect of different numbers of covering warp yarns on the performance of the embedded solar cells was explored. Finally, a larger woven textile solar panel (510 mm × 270 mm) was constructed and tested under different light intensities. It was observed that a P_MAX = 335.3 ± 22.4 mW of energy could be harvested on a sunny day (under 99,000 lux lighting conditions).

Black phosphorus quantum dots induce autophagy and apoptosis of human bronchial epithelial cells via endoplasmic reticulum stress

PURPOSE

The board application of black phosphorus quantum dots (BP-QDs) increases the risk of inhalation exposure in the manufacturing process. The aim of this study is to explore the toxic effect of BP-QDs on human bronchial epithelial cells (Beas-2B) and lung tissue of Balb/c mice.

METHODS

The BP-QDs were characterized using transmission electron microscopy (TEM) and a Malvern laser particle size analyzer. Cell Counting Kit-8 (CCK-8) and TEM were used to detect cytotoxicity and organelle injury. Damage to the endoplasmic reticulum (ER) was detected by using the ER-Tracker molecular probe. Rates of apoptosis were detected by AnnexinV/PI staining. Phagocytic acid vesicles were detected using AO staining. Western blotting and immunohistochemistry were used to examine the molecular mechanisms.

RESULTS

After treatment with different concentrations of BP-QDs for 24 h, the cell viability decreased, as well as activation of the ER stress and autophagy. Furthermore, the rate of apoptosis was increased. Inhibition of ER stress caused by 4-phenyl butyric acid (4-PBA) was shown to significantly inhibit both apoptosis and autophagy, suggesting that ER stress could be an upstream mediator of both autophagy and apoptosis. BP-QD-induced autophagy can also inhibit the occurrence of apoptosis using molecules related to autophagy including rapamycin (Rapa), 3-methyladenine (3-MA), and bafilomycin A1 (Bafi A1). In general, BP-QDs activate ER stress in Beas-2B cells, which further induces autophagy and apoptosis, and autophagy may be activated as a factor that protects against apoptosis. We also observed strong staining of related proteins of ER stress, autophagy, and apoptosis proteins in mouse lung tissue following intracheal instillation over the course of a week.

CONCLUSION

BP-QD-induced ER stress facilitates autophagy and apoptosis in Beas-2B cells and autophagy may be activated as a protective factor against apoptosis. Under conditions of ER stress induced by BP-QDs, The interplay between autophagy and apoptosis determines cell fate.

A review on accelerated development of skin-like MXene electrodes: from experimental to machine learning

Foreshadowing future needs has catapulted the progress of skin-like electronic devices for human-machine interactions. These devices possess human skin-like properties such as stretchability, self-healability, transparency, biocompatibility, and wearability. This review highlights the recent progress in a promising material, MXenes, to realize soft, deformable, skin-like electrodes. Various structural designs, fabrication strategies, and rational guidelines adopted to realize MXene-based skin-like electrodes are outlined. We explicitly discussed machine learning-based material informatics to understand and predict the properties of MXenes. Finally, an outlook on the existing challenges and the future roadmap to realize soft skin-like MXene electrodes to facilitate technological advances in the next-generation human-machine interactions has been described.

Fully stretchable textile-based triboelectric nanogenerators with crepe-paper-induced surface microstructures

Currently, major energy sources such as fossil fuels and nuclear fuels face various issues such as resource depletion, environmental pollution, and climate change. Therefore, there is increasing interest in technology that converts mechanical, heat, vibration, and solar energy discarded in nature and daily life into electrical energy. As various wearable devices have been released in recent years, wearable energy-harvesting technologies capable of self-power generation have garnered attention as next-generation technologies. Among these, triboelectric nanogenerators (TENGs), which efficiently convert mechanical energy into electrical energy, are being actively studied. Textile-based TENG (T-TENGs) are one of the most promising energy harvesters for realizing wearable devices and self-powered smart clothing. This device exhibited excellent wearability, biocompatibility, flexibility, and breathability, making it ideal for powering wearable electronic devices. Most existing T-TENGs generate energy only in the intentional vertical contact mode and exhibit poor durability against twisting or bending deformation with metals. In this study, we propose a sandwich-structured T-TENG (STENG) with stretchability and flexibility for use in wearable energy harvesting. The STENG is manufactured with a structure that can maintain elasticity and generate a maximum voltage of 361.4 V and current of 58.2 μA based on the contact between the upper and lower triboelectric charges. In addition, it exhibited a fast response time and excellent durability over 5000 cycles of repetitive pushing motions. Consequently, the STENG could operate up to 135 light-emitting diodes (with output) without an external power source, and as an energy harvester, it could successfully harvest energy for various operations. These findings provide textile-based power sources with practical applications in e-textiles and self-powered electronics.

Density-of-States Matching-Induced Ultrahigh Current Density and High-Humidity Resistance in a Simply Structured Triboelectric Nanogenerator

Triboelectric nanogenerators (TENGs) can covert mechanical energy into electricity in a clean and sustainable manner. However, traditional TENGs are mainly limited by the low output current, and thus their practical applications are still limited. Herein, a new type of TENG is developed by using conductive materials as the triboelectric layers and electrodes simultaneously. Because of the matched density of states between the two triboelectric layers, this simply structured device reaches an open-circuit voltage of 1400 V and an ultrahigh current density of 1333 mA m^-2 when poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) film and copper (Cu) or aluminum (Al) foil are used as the triboelectric pair. The current density increases by nearly three orders of magnitude compared with traditional TENGs. More importantly, this device can work stably in high-humidity environments, which is always a big challenge for traditional TENGs. Surprisingly, this TENG can even perform well in the presence of water droplets. This work provides a new and effective strategy for constructing high-performance TENGs, which can be used in many practical applications in the near future.

An Advanced Strategy to Enhance TENG Output: Reducing Triboelectric Charge Decay

The Internet of Things (IoT) is poised to accelerate the construction of smart cities. However, it requires more than 30 billion sensors to realize the IoT vision, posing great challenges and opportunities for industries of self-powered sensors. Triboelectric nanogenerator (TENG), an emerging new technology, is capable of easily converting energy from surrounding environment into electricity, thus TENG has tremendous application potential in self-powered IoT sensors. At present, TENG encounters a bottleneck to boost output for large-scale commercial use if just by promoting triboelectric charge generation, because the output is decided by the triboelectric charge dynamic equilibrium between generation and decay. To break this bottleneck, the strategy of reducing triboelectric charge decay to enhance TENG output is focused. First, multiple mechanisms of triboelectric charge decay are summarized in detail with basic theoretical principles for future research. Furthermore, recent advances in reducing triboelectric charge decay are thoroughly reviewed and outlined in three aspects: inhibition and application of air breakdown, simultaneous inhibition of air breakdown and triboelectric charge drift/diffusion, and inhibition of triboelectric charge drift/diffusion. Finally, challenges and future research focus are proposed. This review provides reference and guidance for enhancing TENG output.

Stretchable Woven Fabric-Based Triboelectric Nanogenerator for Energy Harvesting and Self-Powered Sensing

With the triboelectric nanogenerator developing in recent years, it has gradually become a promising alternative to fossil energy and batteries. Its rapid advancements also promote the combination of triboelectric nanogenerators and textiles. However, the limited stretchability of fabric-based triboelectric nanogenerators hindered their development in wearable electronic devices. Here, in combination with the polyamide (PA) conductive yarn, polyester multifilament, and polyurethane yarn, a highly stretchable woven fabric-based triboelectric nanogenerator (SWF-TENG) with the three elementary weaves is developed. Different from the normal woven fabric without elasticity, the loom tension of the elastic warp yarn is much larger than non-elastic warp yarn in the weaving process, which results in the high elasticity of the woven fabric coming from the loom. Based on the unique and creative woven method, SWF-TENGs are qualified with excellent stretchability (up to 300%), flexibility, comfortability, and excellent mechanical stability. It also exhibits good sensitivity and fast responsibility to the external tensile strain, which can be used as a bend-stretch sensor to detect and identify human gait. Its collected power under pressure mode is capable of lighting up 34 light-emitting diodes (LEDs) by only hand-tapping the fabric. SWF-TENG can be mass-manufactured by using the weaving machine, which decreases fabricating costs and accelerates industrialization. Based on these merits, this work provides a promising direction toward stretchable fabric-based TENGs with wide applications in wearable electronics, including energy harvesting and self-powered sensing.

Enhanced triboelectric properties of Eu2O3-doped BaTiO3/PVDF-HFP nanofibers

Because triboelectric nanogenerators (TENGs) convert mechanical energy into electricity, they are sustainable energy sources for powering a diverse range of intelligent sensing and monitoring devices. To enhance the electrical output of polymer-based TENGs, nanofillers are commonly incorporated into polymers. In this study, we developed a simple low-temperature process for preparing high-performance ceramic powder-based TENGs comprising electrospun fibrous surfaces based on poly(vinylidene difluoride-co-hexafluoropropylene) (PVDF-HFP) and dispersed Eu₂O₃-doped BaTiO₃ nanofillers. Herein, we discuss the effect of the modified dielectric properties and transferred charge of the electrification film on the performance of the TENGs. After incorporating the Eu₂O₃-doped BaTiO₃ nanofiller, the maximum output voltage of the 10 wt% Eu₂O₃-BaTiO₃/PVDF-HFP electrospun-nanofiber TENG reached as high as 1004 V with a corresponding current density of 9.9 μA cm^-2. The enhancement in the triboelectric properties of the Eu₂O₃-BaTiO₃/PVDF-HFP electrospun-nanofiber TENGs was due to their high amounts of interface polarization and transferred charge, suggesting improved capture and storage of triboelectric electrons. These Eu₂O₃-BaTiO₃/PVDF-HFP electrospun-nanofiber TENGs could harvest mechanical energy and power electronic devices; they were robust and not affected by the operating temperature or humidity. Furthermore, we used a fabricated device as a sensor for application as a light-emitting diode dimmer switch and for the tracking of leg movement.

Anatomically Designed Triboelectric Wristbands with Adaptive Accelerated Learning for Human-Machine Interfaces

Recent advances in flexible wearable devices have boosted the remarkable development of devices for human-machine interfaces, which are of great value to emerging cybernetics, robotics, and Metaverse systems. However, the effectiveness of existing approaches is limited by the quality of sensor data and classification models with high computational costs. Here, a novel gesture recognition system with triboelectric smart wristbands and an adaptive accelerated learning (AAL) model is proposed. The sensor array is well deployed according to the wrist anatomy and retrieves hand motions from a distance, exhibiting highly sensitive and high-quality sensing capabilities beyond existing methods. Importantly, the anatomical design leads to the close correspondence between the actions of dominant muscle/tendon groups and gestures, and the resulting distinctive features in sensor signals are very valuable for differentiating gestures with data from 7 sensors. The AAL model realizes a 97.56% identification accuracy in training 21 classes with only one-third operands of the original neural network. The applications of the system are further exploited in real-time somatosensory teleoperations with a low latency of <1 s, revealing a new possibility for endowing cyber-human interactions with disruptive innovation and immersive experience.

Self-Assembly of Magnetic Nanochains in an Intrinsic Magnetic Dipole Force-Dominated Regime

Magnetic nanoparticle chains offer the anisotropic magnetic properties that are often desirable for micro- and nanoscale systems; however, to date, large-scale fabrication of these nanochains is limited by the need for an external magnetic field during the synthesis. In this work, the unique self-assembly of nanoparticles into chains as a result of their intrinsic dipolar interactions only is examined. In particular, it is shown that in a high concentration reaction regime, the dipole-dipole coupling between two neighboring magnetic iron cobalt (FeCo) nanocubes, was significantly strengthened due to small separation between particles and their high magnetic moments. This dipole-dipole interaction enables the independent alignment and synthesis of magnetic FeCo nanochains without the assistance of any templates, surfactants, or even external magnetic field. Furthermore, the precursor concentration ([M] = 0.016, 0.021, 0.032, 0.048, 0.064, and 0.096 m) that dictates the degree of dipole interaction is examined-a property dependent on particle size and inter-particle distance. By varying the spinner speed, it is demonstrated that the balance between magnetic dipole coupling and fluid dynamics can be used to understand the self-assembly process and control the final structural topology from that of dimers to linear chains (with aspect ratio >10:1) and even to branched networks. Simulations unveil the magnetic and fluid force landscapes that determine the individual nanoparticle interactions and provide a general insight into predicting the resulting nanochain morphology. This work uncovers the enormous potential of an intrinsic magnetic dipole-induced assembly, which is expected to open new doors for efficient fabrication of 1D magnetic materials, and the potential for more complex assemblies with further studies.

A Review of Recent Development of Wearable Triboelectric Nanogenerators Aiming at Human Clothing for Energy Conversion

Research in the field of wearable triboelectric generators is increasing, and pioneering research into real applications of this technology is a growing need in both scientific and industry research. In addition to the two key characteristics of wearable triboelectric generators of flexibility and generating friction, features such as softness, breathability, washability, and wear resistance have also attracted a lot of attention from the research community. This paper reviews wearable triboelectric generators that are used in human clothing for energy conversion. The study focuses on analyzing fabric structure and examining the integration method of flexible generators and common fibers/yarns/textiles. Compared to the knitting method, the woven method has fewer restrictions on the flexibility and thickness of the yarn. Remaining challenges and perspectives are also investigated to suggest how to bring fully generated clothing to practical applications in the near future.

Deep Trap Boosted Ultrahigh Triboelectric Charge Density in Nanofibrous Cellulose-Based Triboelectric Nanogenerators

For their use in self-powered implantable or wearable electronics, cellulose nanofiber (CNF)-based triboelectric nanogenerators (TENGs) have drawn a lot of attention. However, the low triboelectric charge density (TECD) hinders its further application as a tribolayer for TENGs. In this work, a sulfonated cellulose nanofiber was prepared as an electropositive tribolayer for TENGs to obtain ultrahigh electrical output performance. Since the introduction of sulfonic acid effectively increased the dielectric properties and hole deep trap density of the CNF film, the triboelectric charge storage capacity of the CNF-SO₃Na film was improved. The results showed that the TECD of the CNF-SO₃Na film increased by 460% compared with the pristine CNF film. Furthermore, the dielectric constant and deep trap density of the CNF-SO₃Na film increased by 2.4 times and 8.1 times. This work encourages the use of TENGs in real-world wireless transmission applications by outlining an easy and effective method for building high-performance TENGs.

Intelligent wearable devices based on nanomaterials and nanostructures for healthcare

Emerging classes of flexible electronic sensors as alternatives to conventional rigid sensors offer a powerful set of capabilities for detecting and quantifying physiological and physical signals from human skin in personal healthcare. Unfortunately, the practical applications and commercialization of flexible sensors are generally limited by certain unsatisfactory aspects of their performance, such as biocompatibility, low sensing range, power supply, or single sensory function. This review intends to provide up-to-date literature on wearable devices for smart healthcare. A systematic review is provided, from sensors based on nanomaterials and nanostructures, algorithms, to multifunctional integrated devices with stretchability, self-powered performance, and biocompatibility. Typical electromechanical sensors are investigated with a specific focus on the strategies for constructing high-performance sensors based on nanomaterials and nanostructures. Then, the review emphasizes the importance of tailoring the fabrication techniques in order to improve stretchability, biocompatibility, and self-powered performance. The construction of wearable devices with high integration, high performance, and multi-functionalization for multiparameter healthcare is discussed in depth. Integrating wearable devices with appropriate machine learning algorithms is summarized. After interpretation of the algorithms, intelligent predictions are produced to give instructions or predictions for smart implementations. It is desired that this review will offer guidance for future excellence in flexible wearable sensing technologies and provide insight into commercial wearable sensors.