On the Electron-Transfer Mechanism in the Contact-Electrification Effect

A Computational Framework for Benchmarking the MXene Family as a Triboelectric Nanogenerator Toolbox

MXenes stand out in Triboelectric Nanogenerator devices due to their tunable surface terminations, structural diversity, and excellent electrical conductivity. However, no consensus has been reached when comparing the performance of MXenes. This study presents the first theory-driven framework that links the triboelectric behavior of MXenes to their atomic-scale properties. It also introduces a computational approach for benchmarking triboelectric materials, offering an alternative to the traditional triboelectric series method. By combining analytical models with density functional theory (DFT) calculations, we evaluate 48 MXene members (M2XT2, M = Ti, V, Cr, and Mn; X = C and N; and Tx = F, O, OH, Cl, H, and N) based on key physicochemical parameters: bandgap, work function, surface charge density, and effective density of states. Results highlight the exceptional potential of specific MXenes, such as Mn2CF2, Mn2NF2, Ti2NN2, and Cr2CO2, as negative friction layers and electron trappers due to their high work function and superior charge density. Additionally, OH MXenes like V2C(OH)2, Cr2N(OH)2, Ti2C(OH)2, and Ti2N(OH)2 demonstrate optimal performance as positive friction layers.

A Wireless Millimeter-Scale Device for in Vivo Electromagnetic Brain Tumor Therapy by Ultrasound-Responsive Ti3C2Tx Hydrogel

Implantable devices that integrate advanced nanomaterials with wireless energy systems represent a transformative approach to tackling brain tumors. Here, a millimeter-scale implantable device based on an MXene/polyvinyl alcohol (PVA) hydrogel is introduced, designed for precise and minimally invasive brain tumor therapy via tunable alternating electric fields. This device presents a novel approach by combining ultrasonic wireless energy transfer with triboelectric energy harvesting, eliminating the need for in vivo batteries and enabling continuous operation in a completely wireless manner. The system not only optimizes energy harvesting efficiency but also ensures the localized delivery of therapeutic electric fields directly to the tumor site. Its compact size and mechanical flexibility allow for precise implantation in the complex brain environment, offering a minimally invasive solution with enhanced safety and adaptability. Preclinical evaluations using U-87 MG orthotopic glioblastoma models demonstrate significant tumor growth inhibition and a marked improvement in survival rates, underscoring its therapeutic potential.

Unveiling Mechanically Driven Catalytic Processes: Beyond Piezocatalysis to Synergetic Effects

Mechanically driven catalysis (MDC) has emerged as an effective strategy for environmental remediation, renewable energy conversion, and cancer therapy; this functions by converting mechanical forces to drive catalytic reactions. This review examines four primary mechanisms, namely, piezocatalysis, flexocatalysis, tribocatalysis, and sonocatalysis, each involving specific catalytic pathways for harnessing mechanical energy at the nanoscale. However, significant challenges arise in decoupling the effects related to each individual mechanism in order to better understand and manipulate their synergies. In this review, the fundamental principles underpinning MDC are systematically interpreted. Beyond mechanistic insights, recent advancements in performance enhancement strategies for these catalysts are highlighted. Potential applications using these mechanistic approaches in environmental remediation (pollutant and antibiotic degradation and microbial disinfection), renewable energy conversion (hydrogen production and greenhouse gas conversion), and biomedical treatments (particularly cancer therapy) are discussed. Finally, the mechanistic synergies and limiting factors are explored, addressing challenges related to the overlooked combined effects of ultrasound as the activation source, complexities in mechanical force interactions at the nanoscale, and the need for targeted application strategies. Additionally, the industrial potential of these catalytic processes with consideration to scalability and practical deployment is evaluated. While challenges remain, this review provides a roadmap for advancing mechanically driven catalyst design and implementation toward real-world applications, offering potential into its future trajectory and transformative impact across numerous fields.

Ultrafast Degradation of Organic Dyes by Water Atomization and Contact-Electro-Catalysis

Contact-electro-catalysis (CEC) has emerged as a novel approach for catalyzing redox reactions. However, there is still significant room for enhancing the catalytic efficiency of CEC. Here, an organic degradation device that combines water atomization and CEC based on a gas-liquid two-phase flow-based triboelectric nanogenerator (GL-TENG) was designed. When using 8 mg/L of crystal violet (CV) as the target dye and the airflow velocity reaches 30 m/s, the degradation rate constant k is as high as 73.15 min-1, significantly exceeding existing contact electrocatalytic efficiencies. The impact of the dye concentration on the output performance of GL-TENG was investigated. It shows a good linear relationship between the concentration and the output signal of the GL-TENG. Real-time monitoring of dye concentration can be achieved using the output signal of the GL-TENG located at the end of the tube. These experimental results not only offer an ultrafast method for degrading organic dyes but also provide new insights into the interactions between dye solutions and solid surfaces.

Two-dimensional chromium telluride-coated 3D-printed architectures for energy harvesting

Rapid development of industries, urbanization, and technological advancements have increased demand for sustainable and cost-effective alternative energy sources. In this work, a self-powered flexible 3D-printed triboelectric nanogenerator coated with 2D chromium telluride (Cr2Te3) (3D-TENG) is presented as an innovative energy harvesting approach from pressure and temperature. The optimized flexible 3D-printed hexagonal structures with coatings show varying specific yield strength and porosity. The 3D-TENGs achieved a maximum output voltage of ∼39 V under periodic impacts of ~0.8 kPa and their performance further increased (∼45 V) in the presence of varied temperatures. The outstanding results and flexibility of the 3D-TENG devices highlight their potential in self-powered energy harvesting from external heat, magnetic fields, and body weight. Density functional theory (DFT) calculations further explained the interaction between 2D Cr2Te3 and the polymer surface under external impact. Therefore, we believe that our findings illustrate the potential of integrating 2D materials with 3D-printed architectures to enhance the efficiency and adaptability of flexible, lightweight, low-cost, and eco-friendly TENG devices for industrial applications.

In Situ Polarization Enables Dipole Alignment of α-Phase Polyamide 11 Nanoribbons for Breathable Triboelectric Textile

Triboelectric textiles have been extensively studied for wearable energy applications, including single-fiber power generation, humidity-resistant power generation, air-breakdown-based power generation, etc. However, intrinsic tribo-charge transfer in fiber- or textile-based triboelectric materials remains at a low level. Here, we propose a polarization strategy to enhance triboelectric performance using α-phase polyamide 11 nanoribbons. By employing a high-voltage electrostatic field during electrospinning, we achieve in situ polarization of polyamide 11, resulting in an 116% improvement in the performance of polyamide 11-based energy nonwovens. Additionally, we apply cold pressing to optimize the specific surface area and air permeability of the all-fiber-energy nonwoven, achieving a balance of high electrical performance and wearability. We further demonstrate applications of this nanofiber-based energy textile in wireless sensing and breathable energy insoles. This all-fiber performance enhancement strategy provides valuable insights for the development of high-performance triboelectric textiles in the future.

Fe0/PTFE Triboelectric Nanogenerators for Ultrafast Dye and Antibiotic Degradation

Triboelectric catalysis is a new technology that converts mechanical energy to chemical energy. This study presents a novel efficient triboelectric catalytic design based on iron (Fe0) and polytetrafluoroethylene (PTFE). The tribocatalytic effect was evaluated by degrading methyl orange (MO), crystal violet (CV), and tetracycline (TC). The degradation efficiency can reach 95, 97, and 93% within 24 min, respectively, and the kinetic constant K of CV was as high as 0.1460 min-1. The comparison with the stirring experiment showed that the friction catalytic effect between Fe0 and PTFE was significantly enhanced under ultrasonic irradiation. Furthermore, the triboelectric effect is used to provide simplicity and strong triboelectric catalytic activity of Fe0/PTFE, and the influencing factors are analyzed. And the production of reactive oxygen species (ROS) of hydroxyl radicals and superoxide radicals increases during the catalytic process. The mechanism of triboelectric catalysis is discussed in terms of electron transfer and transition. This study utilizes the triboelectric effect of Fe0/PTFE to provide simplicity and superior triboelectric catalytic activity under ultrasonic irradiation.

Nanostructures and Nanomaterials Integrated into Triboelectric Nanogenerators

The pursuit of eco-friendly and renewable power generation has driven technological breakthroughs in nanoscale engineering, particularly regarding triboelectric nanogenerators (TENGs). These devices have become a focus of interest due to their capacity to effectively transform kinetic energy into electrical power via combined triboelectrification and electrostatic charge separation mechanisms. TENGs now find expanding implementations across multiple fields including in flexible electronics, autonomous sensing systems, and ambient energy conversion technologies. Enhancing TENG performance critically depends on the strategic design and application of nanostructures and nanomaterials. Nonetheless, challenges such as material selection, compatibility, homogeneous dispersion, interfacial stability, and production scalability must be overcome to advance TENG technology. Moreover, the mechanisms by which nanomaterials contribute to the triboelectric effect remain insufficiently understood, underscoring the necessity for systematic theoretical models. This review provides a comprehensive overview of recent advancements in integrating nanostructures and nanomaterials into TENGs, elucidating their roles, advantages, and underlying mechanisms in enhancing energy conversion efficiency, while identifying key challenges and proposing future research directions.

Nanoelectronics-enabled reservoir computing hardware for real-time robotic controls

Traditional robotic vehicle control algorithms, implemented on digital devices with firmware, result in high power consumption and system complexity. Advanced control systems based on different device physics are essential for the advancement of sophisticated robotic vehicles and miniature mobile robots. Here, we present a nanoelectronics-enabled analog control system mimicking conventional controllers' dynamic responses for real-time robotic controls, substantially reducing training cost, power consumption, and footprint. This system uses a reservoir computing network with interconnected memristive channels made from layered semiconductors. The network's nonlinear switching and short-term memory characteristics effectively map input sensory signals to high-dimensional data spaces, enabling the generation of motor control signals with a simply trained readout layer. This approach minimizes software and analog-to-digital conversions, enhancing energy and resource efficiency. We demonstrate this system with two control tasks: rover target tracking and drone lever balancing, achieving similar performance to traditional controllers with ~10-microwatt power consumption. This work paves the way for ultralow-power edge computing in miniature robotic systems.

Swing-Arm Triboelectric Nanogenerator for Efficient Wave Energy Harvesting

Ocean waves represent a vast, untapped source of renewable energy, yet current wave energy harvesting technologies often struggle with efficiency, cost, and scale. Triboelectric nanogenerators (TENGs) have emerged as promising devices for mechanical energy harvesting, but their application in wave energy conversion remains limited by challenges in their design and performance. Here, we present a novel swing-arm triboelectric nanogenerator (SA-TENG) specifically designed for wave energy harvesting. Our device employs a pendulum-inspired mechanism with PTFE rollers and nylon tracks, enabling efficient energy capture from the primary motion direction of waves. We developed a dynamic model to characterize the SA-TENG's motion under wave excitation, providing crucial insights into its operational behavior. Through systematic experimentation and optimization, we achieved a maximum open-circuit voltage of 140 V and a short-circuit current of 1.2 μA. The SA-TENG demonstrated its practical applicability by powering 50 LEDs and operating a humidity-temperature sensor in a self-powered system. This work not only introduces an innovative wave energy harvesting device but also provides a comprehensive framework for modeling and optimizing TENG performance in marine environments. The SA-TENG's design principles and analysis methods pave the way for scaling up wave energy harvesting, potentially revolutionizing blue energy utilization and contributing to sustainable coastal and maritime technologies.

Digital light processing 3D printing of flexible devices: actuators, sensors and energy devices

Flexible devices are increasingly crucial in various aspects of our lives, including healthcare devices and human-machine interface systems, revolutionizing human life. As technology evolves rapidly, there is a high demand for innovative manufacturing methods that enable rapid prototyping of custom and multifunctional flexible devices with high quality. Recently, digital light processing (DLP) 3D printing has emerged as a promising manufacturing approach due to its capabilities of creating intricate customized structures, high fabrication speed, low-cost technology and widespread adoption. This review provides a state-of-the-art overview of the recent advances in the creation of flexible devices using DLP printing, with a focus on soft actuators, flexible sensors and flexible energy devices. We emphasize how DLP printing and the development of DLP printable materials enhance the structural design, sensitivity, mechanical performance, and overall functionality of these devices. Finally, we discuss the challenges and perspectives associated with DLP-printed flexible devices. We anticipate that the continued advancements in DLP printing will foster the development of smarter flexible devices, shortening the design-to-manufacturing cycles.

Strategies for Improving Contact-Electro-Catalytic Efficiency: A Review

Contact-electro-catalysis (CEC) has emerged as a promising catalytic methodology, integrating principles from solid-liquid triboelectric nanogenerators (SL-TENGs) into catalysis. Unlike conventional approaches, CEC harnesses various forms of mechanical energy, including wind and water, along with other renewable sources, enabling reactions under natural conditions without reliance on specific energy inputs like light or electricity. This review presents the basic principles of CEC and discusses its applications, including the degradation of organic molecules, synthesis of chemical substances, and reduction of metals. Furthermore, it explores methods to improve the catalytic efficiency of CEC by optimizing catalytic conditions, the structure of catalyst materials, and the start-up mode. The concluding section offers insights into future prospects and potential applications of CEC, highlighting its role in advancing sustainable catalytic technologies.

Self-Powered Artificial Neuron Devices: Towards the All-In-One Perception and Computation System

The increasing demand for energy supply in sensing units and the computational efficiency of computation units has prompted researchers to explore novel, integrated technology that offers high efficiency and low energy consumption. Self-powered sensing technology enables environmental perception without external energy sources, while neuromorphic computation provides energy-efficient and high-performance computing capabilities. The integration of self-powered sensing technology and neuromorphic computation presents a promising solution for an all-in-one system. This review examines recent developments and advancements in self-powered artificial neuron devices based on triboelectric, piezoelectric, and photoelectric effects, focusing on their structures, mechanisms, and functions. Furthermore, it compares the electrical characteristics of various types of self-powered artificial neuron devices and discusses effective methods for enhancing their performance. Additionally, this review provides a comprehensive summary of self-powered perception systems, encompassing tactile, visual, and auditory perception systems. Moreover, it elucidates recently integrated systems that combine perception, computing, and actuation units into all-in-one configurations, aspiring to realize closed-loop control. The seamless integration of self-powered sensing and neuromorphic computation holds significant potential for shaping a more intelligent future for humanity.

The Role of Interfaces and Charge for Chemical Reactivity in Microdroplets

A wide variety of reactions are reported to be dramatically accelerated in aqueous microdroplets, making them a promising platform for environmentally clean chemical synthesis. However, to fully utilize the microdroplets for accelerating chemical reactions requires a fundamental understanding of how microdroplet chemistry differs from that of a homogeneous phase. Here we provide our perspective on recent progress to this end, both experimentally and theoretically. We begin by reviewing the many ways in which microdroplets can be prepared, creating water/hydrophobic interfaces that have been frequently implicated in microdroplet reactivity due to preferential surface adsorption of solutes, persistent electric fields, and their acidity or basicity. These features of the interface interplay with specific mechanisms proposed for microdroplet reactivity, including partial solvation, possible gas phase channels, and the presence of highly reactive intermediates. We especially highlight the role of droplet charge and associated electric fields, which appears to be key to understanding how certain reactions, like the formation of hydrogen peroxide and reduced transition metal complexes, are thermodynamically possible in microdroplets. Lastly, we emphasize opportunities for theoretical advances and suggest experiments that would greatly enhance our understanding of this fascinating subject.

Mechanical-Stimuli-Driven Pseudo-Conductive Channels Along Dielectric Heterojunction Interfaces for Mechanoelectric Energy Conversion and Transmission

Mechanoelectric energy conversion holds promise for energy conversion and transmission devices, yet conventional configurations rely on large-area conductive materials in active regions, limiting architectural design for cutting-edge devices. Here, a rational strategy is reported to create mechanical stimuli-driven pseudo-conductive (MSPC) channels entirely from dielectric materials, eliminating the need for electrodes in active regions. An in-depth investigation of MSPC channel formation mechanism at dielectric interfaces is conducted, employing energy band analyses. Following the mechanical stimuli-driven charging process, MSPC device effectively transmits electrical signals over 42 mm, achieving remarkable 512% enhancement compared to its pristine state. Control devices with non-continuous dielectric configurations highlight the impact of heterojunction interfaces on MSPC channels. A resistor-capacitor charging test reveals up to 49% reduction in voltage change rate, indicating a substantial decrease in electrical impedance along the MSPC channel. Furthermore, MSPC devices demonstrate information transmission capabilities, such as sequences of bits or letters, utilizing solely dielectric configurations. This study paves the way to reduce conductive materials of wearable electronics, biomedical implants, and IoT technologies, overcoming significant challenges such as potential electrical shortages, design inflexibility, limited manufacturing scalability, and maintenance issues.

Recent Progress of Chemical Reactions Induced by Contact Electrification

Contact electrification (CE) spans from atomic to macroscopic scales, facilitating charge transfer between materials upon contact. This interfacial charge exchange, occurring in solid-solid (S-S) or solid-liquid (S-L) systems, initiates radical generation and chemical reactions, collectively termed contact-electro-chemistry (CE-Chemistry). As an emerging platform for green chemistry, CE-Chemistry facilitates redox, luminescent, synthetic, and catalytic reactions without the need for external power sources as in traditional electrochemistry with noble metal catalysts, significantly reducing energy consumption and environmental impact. Despite its broad applicability, the mechanistic understanding of CE-Chemistry remains incomplete. In S-S systems, CE-Chemistry is primarily driven by surface charges, whether electrons, ions, or radicals, on charged solid interfaces. However, a comprehensive theoretical framework is yet to be established. While S-S CE offers a promising platform for exploring the interplay between chemical reactions and triboelectric charge via surface charge modulation, it faces significant challenges in achieving scalability and optimizing chemical efficiency. In contrast, S-L CE-Chemistry focuses on interfacial electron transfer as a critical step in radical generation and subsequent reactions. This approach is notably versatile, enabling bulk-phase reactions in solutions and offering the flexibility to choose various solvents and/or dielectrics to optimize reaction pathways, such as the degradation of organic pollutants and polymerization, etc. The formation of an interfacial electrical double layer (EDL), driven by surface ion adsorption following electron transfer, plays a pivotal role in CE-Chemical processes within aqueous S-L systems. However, the EDL can exert a screening effect on further electron transfer, thereby inhibiting reaction progress. A comprehensive understanding and optimization of charge transfer mechanisms are pivotal for elucidating reaction pathways and enabling precise control over CE-Chemical processes. As the foundation of CE-Chemistry, charge transfer underpins the development of energy-efficient and environmentally sustainable methodologies, holding transformative potential for advancing green innovation. This review consolidates recent advancements, systematically classifying progress based on interfacial configurations in S-S and S-L systems and the underlying charge transfer dynamics. To unlock the full potential of CE-Chemistry, future research should prioritize the strategic tuning of material electronegativity, the engineering of sophisticated surface architectures, and the enhancement of charge transport mechanisms, paving the way for sustainable chemical innovations.

Research on the Performance of a Liquid-Solid Triboelectric Nanogenerator Prototype Based on Multiphase Liquid

In recent years, liquid-solid triboelectric nanogenerators (L-S TENGs) have been rapidly developed in the field of liquid energy harvesting and self-powered sensing. This is due to a number of advantages inherent in the technology, including the low cost of fabricated materials, structural diversity, high charge-energy conversion efficiency, environmental friendliness, and a wide range of applications. As liquid phase dielectric materials typically used in L-S TENG, a variety of organic and inorganic single-phase liquids, including distilled water, acidic solutions, sodium chloride solutions, acetone, dimethyl sulfoxide, and acetonitrile, as well as paraffinic oils, have been used in experiments. However, it is noteworthy that the function of multiphase liquids as dielectric materials is still understudied. The "Multiphase Liquid Triboelectric Nanogenerator Prototype (ML-TENG Pro)" presented in this paper takes a single-electrode solid-liquid triboelectric nanogenerator as the basic model and uses lubricating oil and deionized water as dielectric materials. After verifying the stability of single-phase liquid materials (e.g., DI water, seawater, ethanol, etc.) for power generation, the power generation performances of oil-water two-phase, gas-oil-water three-phase (with a small number of bubbles), and gas-oil-water three-phase (with many bubbles) in open space are further investigated. COMSOL Multiphysics 6.0 software was used to investigate the material transport mechanism and formation of oil-water two-phase and gas-oil-water three-phase. Finally, this study presents the power generation performance of ML-TENG Pro in the extreme state of gas-oil-water three-phase "emulsification". This paper outlines the limitations of the ML-TENG, named PRO, and suggests avenues for future improvement. The research presented in this paper provides a theoretical basis for evaluating the quality of lubricants for mechanical power equipment.

Textile-Based TENG Woven with Fluorinated Polyimide Yarns for Motion and Position Monitoring

Polyimide-based triboelectric nanogenerators (TENGs) capable of energy harvesting in harsh environments (high temperature and high humidity) have been extensively studied. However, most polyimide-based TENGs have the disadvantages of poor air permeability and poor softness. In this study, a core-shell yarn with good air permeability, softness, and high electric output performance was successfully prepared by conjugate electrospinning. FEP-doped FPI and nickel-plated aramid yarn were employed as the shell and core materials, respectively. Due to the unique hierarchical porous structure and fluorinated functional group modification, the yarns exhibit excellent output performance (maximum open-circuit voltage is 22.7 V per length of 10 cm) compared to traditional polyimide yarns. The textile woven with this yarn has good high-temperature resistance, antifouling, waterproof, and self-cleaning performance, and still maintains an output performance of about 80% under 99% relative humidity. Moreover, this textile-based TENG has no significant attenuation after 10,000 cycles, showing good stability and durability. Finally, the TENG based on the intelligent fire suit is designed, which can be used for the movement and position monitoring of firefighters in high-temperature and high-humidity environments. This fluorinated polyimide yarn prepared in this study provides a promising solution for the development of self-powered sensors capable of monitoring the movement status and position of firefighters in high-temperature and high-humidity environments.

Liquid-Solid Triboelectric Nanogenerator-Based DNA Barcode Detection Biosensor for Species Identification

DNA barcode detection method is widely applied for species identification, which is imperative to evaluate the effect of human economic activities on the biodiversity of ecosystem. However, the wide utilization of existing detection biosensors is limited by bulky and expensive instruments, such as Raman spectroscopy and electrochemical station. Herein, a liquid-solid triboelectric nanogenerator (TENG)-based DNA barcode detection biosensor is proposed, which consists of water flow, fluid channel, and PDMS film attached by specifically designed capture probe. Through sequentially combining capture probe, targeted DNA barcode, and signal probe with Au nanoparticles (NPs), the surface charge density of friction layer of TENG decreases under the effect of AuNPs, verified by the density functional theory (DFT) method. Consequently, the peak value of output current spike signal for targeted DNA is smaller than that for other DNA, which is the working mechanism of the present TENG-based biosensor. Such biosensor successfully recognizes Alvinocaris muricola among different types of Alvinocarididae shrimps, and its low limit detection can reach 1×10-12 m. The present work provides a paradigm-shift way to develop an inexpensive and accurate technique to detect DNA barcode for species identification, and paves a novel way for the application of liquid-solid TENG.

Biocompatible Triboelectric Nanogenerators for Self-Powered Microelectronics: Design, Performance, and Real-Time Applications

In the present study, we demonstrated a cost-effective chia seed-based triboelectric nanogenerator (C-TENG), leveraging the triboelectric properties of chia seeds. The C-TENGs are fabricated with a simple architecture, establishing adaptability, cost effectiveness, and versatility as an ecofriendly harvester of mechanical energy. The C-TENG exhibits open- circuit voltage and short-circuit currents on the order of 501.8 V and 24.5 μA, respectively. Load matching reveals the maximum power density output at a load resistance of 5 MΩ, reaching 290 mW/m2. The cycle test over 3400 cycles confirms the C-TENG's stability. Furthermore, its capability to charge capacitors with different capacitances highlights its potential as a biomechanical energy harvester. The prototype device for evaluating the real-time applications demonstrated the C-TENG's, ability to illuminate LEDs, power a calculator, capture kinetic energy during walking, and transducer as an electronic switch. This investigation pioneered the exploration of chia seeds in TENGs, presenting a sustainable and efficient solution for self-powered microelectronic devices. The electron affinity of materials has been analyzed through inter- and intramolecular charge distribution using density functional theory. The direction of charge transfer was estimated through frontier molecular orbital analysis supported by the experimental findings of triboelectrification via contact separation from the molecule to polytetrafluoroethylene (PTFE).

Advancements in Solid-Liquid Nanogenerators: A Comprehensive Review and Future Prospects

In recent years, the advent of the smart era has confronted a novel "energy crisis"-the challenge of distributed energy provision, necessitating an imperative for clean energy development. Encompassing 71% of the Earth's surface, water stands as the predominant conduit for energy transfer on our planet, effectively harnessing a fraction thereof to fulfill global energy demands. Modern hydropower technology primarily harnesses concentrated low-entropy water energy. However, the majority of natural water energy is widely dispersed in the environment as high-entropy distributed water energy, encompassing raindrop energy, stream energy, wave energy, evaporation energy, and other small-scale forms of water energy. While these energies are readily available, their collection poses significant challenges. Consequently, researchers initiated investigations into high-entropy water energy harvesting technology based on the electrodynamic effect, triboelectric effect, water volt effect, and other related phenomena. The present paper provides a comprehensive review of high-entropy water energy harvesting technologies, encompassing their underlying mechanisms, optimization strategies, and diverse applications. The current bottlenecks of these technologies are comprehensively analyzed, and their future development direction is prospectively discussed, thereby providing valuable guidance for future research on high-entropy water energy collection technology.

Comprehensive Insights on MXene-Based TENGs: from Structures, Functions to Applications

The rapid advancement of triboelectric nanogenerators (TENGs) has introduced a transformative approach to energy harvesting and self-powered sensing in recent years. Nonetheless, the untapped potential of TENGs in practical scenarios necessitates multiple strategies like material selections and structure designs to enhance their output performance. Given the various superior properties, MXenes, a kind of novel 2D materials, have demonstrated great promise in enhancing TENG functionality. Here, this review comprehensively delineates the advantages of incorporating MXenes into TENGs, majoring in six pivotal aspects. First, an overview of TENGs is provided, stating their theoretical foundations, working modes, material considerations, and prevailing challenges. Additionally, the structural characteristics, fabrication methodologies, and family of MXenes, charting their developmental trajectory are highlighted. The selection of MXenes as various functional layers (negative and positive triboelectric layer, electrode layer) while designing TENGs is briefed. Furthermore, the distinctive advantages of MXene-based TENGs and their applications are emphasized. Last, the existing challenges are highlighted, and the future developing directions of MXene-based TENGs are forecasted.

Advanced Dielectric Materials for Triboelectric Nanogenerators: Principles, Methods, and Applications

Triboelectric nanogenerator (TENG) manifests distinct advantages such as multiple structural selectivity, diverse selection of materials, environmental adaptability, low cost, and remarkable conversion efficiency, which becomes a promising technology for micro-nano energy harvesting and self-powered sensing. Tribo-dielectric materials are the fundamental and core components for high-performance TENGs. In particular, the charge generation, dissipation, storage, migration of the dielectrics, and dynamic equilibrium behaviors determine the overall performance. Herein, a comprehensive summary is presented to elucidate the dielectric charge transport mechanism and tribo-dielectric material modification principle toward high-performance TENGs. The contact electrification and charge transport mechanism of dielectric materials is started first, followed by introducing the basic principle and dielectric materials of TENGs. Subsequently, modification mechanisms and strategies for high-performance tribo-dielectric materials are highlighted regarding physical/chemical, surface/bulk, dielectric coupling, and structure optimization. Furthermore, representative applications of dielectric materials based TENGs as power sources, self-powered sensors are demonstrated. The existing challenges and promising potential opportunities for advanced tribo-dielectric materials are outlined, guiding the design, fabrication, and applications of tribo-dielectric materials.

Charge Generation and Enhancement of Key Components of Triboelectric Nanogenerators: A Review

The past decade has witnessed remarkable progress in high-performance Triboelectric nanogenerators (TENG) with the design and synthesis of functional dielectric materials, the exploration of novel dynamic charge transport mechanisms, and the innovative design of architecture, making it one of the most crucial technologies for energy harvesting. High output charge density is fundamental for TENG to expand its application scope and accelerate industrialization; it depends on the dynamic equilibrium of charge generation, trapping, de-trapping, and migration within its core components. Here, this review classifies and summarizes innovative approaches to enhance the charge density of the charge generation, charge trapping, and charge collection layers. The milestone of high charge density TENG is reviewed based on material selection and innovative mechanisms. The state-of-the-art principles and techniques for generating high charge density and suppressing charge decay are discussed and highlighted in detail, and the distinct charge transport mechanisms, the technologies of advanced materials preparation, and the effective charge excitation strategy are emphatically introduced. Lastly, the bottleneck and future research priorities for boosting the output charge density are summarized. A summary of these cutting-edge developments intends to provide readers with a deep understanding of the future design of high-output TENG.

Heat-Excitation-Based Triboelectric Charge Promotion Strategy

The surface charge decay is observed at high temperatures due to thermionic emission, which, however, may not be the only mechanism contributing to the surface charge variation. Here, a triboelectric charge promotion strategy due to the heat-excitation effect of hot electrons near the fermi level is demonstrated, while the final charge is determined by the balance between thermionic emission and the heat-excitation effect. It is demonstrated that metals with lower work function exhibit a better heat excitation capability, and polymers with lower fluorine content in molecule chains further boost the charge output, where metal/Kapton pairs demonstrated a charge promotion of over 2 times at the temperature of 383 K with good durability during 90 min measurement. The heat-excitation effect and charge durability in sliding freestanding-triboelectric-layer (SFT) mode triboelectric nanogenerator (TENG) is demonstrated as well, where the energy is promoted by over 3 times and the capacitor charging speed is doubled as well, with an energy promotion from 109.34 to 373 µJ per cycle to successfully trigger a discharger. This work suggests a promising future of the heat-excitation effect as a new charge promotion strategy for TENG toward different applications in high-temperature environments.

Multi-Attribute Triboelectric Materials and Innovative Applications Via TENGs

Triboelectric nanogenerators (TENGs) as an avant-garde technology that transforms mechanical energy into electrical energy, offering a new direction for green energy and sustainable development. By means of high-efficiency TENGs, conventional materials as new triboelectric materials have exhibited multi-attribute characteristics, achieving innovative applications in the field of micro-nano energy harvesting and self-powered sensing. The progress of TENGs technology with the triboelectric materials is complementary and mutually promoting. On the one hand, one of the cruxes of TENGs lies in the triboelectric materials, which have a decisive impact on their performance. On the other hand, as the research and application of TENGs continue to deepen, higher demands are placed on triboelectric materials, which in turn promotes the advancement of the entire material system as well as the fields of materials science and physics. This work aims to delve into the characteristics, types, preferred choices, and modification treatments of triboelectric materials on the performances of TENGs, hoping to provide guidance and insights for future research and applications.

Biowaste-Derived Triboelectric Nanogenerators for Emerging Bioelectronics

Triboelectric nanogenerators (TENGs) combine contact electrification and electrostatic induction effects to convert waste mechanical energy into electrical energy. As conventional devices contribute to electronic waste, TENGs based on ecofriendly and biocompatible materials have been developed for various energy applications. Owing to the abundance, accessibility, low cost, and biodegradability of biowaste (BW), recycling these materials has gained considerable attention as a green approach for fabricating TENGs. This review provides a detailed overview of BW materials, processing techniques for BW-based TENGs (BW-TENGs), and potential applications of BW-TENGs in emerging bioelectronics. In particular, recent progress in material design, fabrication methods, and biomechanical and environmental energy-harvesting performance is discussed. This review is aimed at promoting the continued development of BW-TENGs and their adoption for sustainable energy-harvesting applications in the field of bioelectronics.

Unleashing the Potential of Electroactive Hybrid Biomaterials and Self-Powered Systems for Bone Therapeutics

The incidence of large bone defects caused by traumatic injury is increasing worldwide, and the tissue regeneration process requires a long recovery time due to limited self-healing capability. Endogenous bioelectrical phenomena have been well recognized as critical biophysical factors in bone remodeling and regeneration. Inspired by bioelectricity, electrical stimulation has been widely considered an external intervention to induce the osteogenic lineage of cells and enhance the synthesis of the extracellular matrix, thereby accelerating bone regeneration. With ongoing advances in biomaterials and energy-harvesting techniques, electroactive biomaterials and self-powered systems have been considered biomimetic approaches to ensure functional recovery by recapitulating the natural electrophysiological microenvironment of healthy bone tissue. In this review, we first introduce the role of bioelectricity and the endogenous electric field in bone tissue and summarize different techniques to electrically stimulate cells and tissue. Next, we highlight the latest progress in exploring electroactive hybrid biomaterials as well as self-powered systems such as triboelectric and piezoelectric-based nanogenerators and photovoltaic cell-based devices and their implementation in bone tissue engineering. Finally, we emphasize the significance of simulating the target tissue's electrophysiological microenvironment and propose the opportunities and challenges faced by electroactive hybrid biomaterials and self-powered bioelectronics for bone repair strategies.

Evolution of Tribotronics: From Fundamental Concepts to Potential Uses

The intelligent sensing network is one of the key components in the construction of the Internet of Things, and the power supply technology of sensor communication nodes needs to be solved urgently. As a new field combining tribo-potential with semiconductor devices, tribotronics, based on the contact electrification (CE) effect, realizes direct interaction between the external environment and semiconductor devices by combining triboelectric nanogenerator (TENG) and field-effect transistor (FET), further expanding the application prospects of micro/nano energy. In this paper, the research progress of tribotronics is systematically reviewed. Firstly, the mechanism of the CE effect and the working principles of TENG are introduced. Secondly, the regulation theory of tribo-potential on carrier transportation in semiconductor devices and the research status of tribotronic transistors are summarized. Subsequently, the applications of tribotronics in logic circuits and memory devices, smart sensors, and artificial synapses in recent years are demonstrated. Finally, the challenges and development prospects of tribotronics in the future are projected.

Triboelectric Nanogenerator Made with Stretchable, Antibacterial Hydrogel Electrodes for Biomechanical Sensing

Triboelectric nanogenerators (TENGs) have attracted widespread attention as a promising candidate for energy harvesting due to their flexibility and high power density. To meet diverse application scenarios, a highly stretchable (349%), conductive (1.87 S m-1), and antibacterial electrode composed of carbon quantum dots/LiCl/agar-polyacrylamide (CQDs/LiCl/agar-PAAm) dual-network (DN) hydrogel is developed for wearable TENGs. Notably, the concentration of agar alters the pore spacing and pore size of the DN hydrogel, thereby impacting the network cross-linking density and the migration of conductive ions (Li+ and Cl-). This variation further affects the mechanical strength and conductivity of the hydrogel electrode, thus modulating the mechanical stability and electrical output performance of the TENGs. With the optimal agar content, the tensile strength and conductivity of the hydrogel electrode increase by 211 and 719%, respectively. This enhancement ensures the stable output of TENGs during continuous operation (6000 cycles), with open-circuit voltage, short-circuit current, and transferred charge increasing by 200, 530, and 155%, respectively. Additionally, doping with CQDs enables the hydrogel electrode to effectively inhibit the Gram-negative bacterium Escherichia coli. Finally, the TENGs are utilized as a self-power smart ring for efficient and concise information transmission via Morse code. Consequently, this study introduces a creative approach for designing and implementing multifunctional, flexible wearable devices.

Molecular Simulation of the Water Diffusion Behavior and Electronic Properties of Boron-Nitride-Composited Mineral Oil

Despite the fact that doping nanoparticles into insulating transformer oil has proven to be an effective method of enhancing its dielectric and electrical properties, it remains unclear how different types and surface conditions of nanoparticles may affect their dielectric and electrical properties. Therefore, the effect of doping various types of BN nanoparticles (nanosphere, nanotube, and nanosheet) in insulating mineral oil (MO) on the diffusion properties of water molecules and electrical properties across the BN/MO interface was investigated using molecular dynamics (MD) and Density Functional Theory (DFT) simulations. Our results show that different surface morphology and grafted functional groups in different types of BN nanoparticles have a significant impact both on the water diffusion behavior and the interfacial potential barrier across the interface between BN and MO. In the MO system directly doped by BN nanospheres, water diffusion behavior is not significantly restricted. However, grafting -NH2 polar groups onto the BN nanoparticle surface may significantly limit the diffusion behavior of water due to the strong attraction between the -NH2 polar groups and water molecules; the most significant effect is with nanospheres, followed by nanotubes and nanosheets. In terms of electrical properties across the interface between BN and MO, the h-BN surface (derived from BN nanosheets and nanotubes) acts as a trap for electrons in MO (-0.59 eV), while the c-BN surface (derived from BN nanospheres) acts as a potential barrier for electrons in MO (1.45 eV), and it is noteworthy that the presence of water molecules near the interface between BN and MO has little impact on the potential barriers. Advancing a fundamental understanding of the electrical and water diffusion properties of MO in correlation with the surface morphology of different types of nanoparticles is key to improving the insulation properties of oil-impregnated power transformers.

A Study on the Mechanisms and Performance of a Polyvinyl Alcohol-Based Nanogenerator Based on the Triboelectric Effect

Polyvinyl alcohol (PVA), a versatile polymer, is extensively used across many industries, such as chemicals, food, healthcare, textiles, and packaging. However, research on applying PVA to triboelectric nanogenerators (TENGs) remains limited. Consequently, we chose PVA as the primary material to explore its contact electrification mechanisms at the molecular level, alongside materials like Polyethylene (PE), Polyvinylidene fluoride (PVDF), and Polytetrafluoroethylene (PTFE). Our findings show that PVA has the highest band gap, with the smallest band gap occurring between the HOMO of PVA and the LUMO of PTFE. During molecular contact, electron transfer primarily occurs in the outermost layers of the molecules, influenced by the functional groups of the polymers. The presence of fluorine atoms enhances the electron transfer between PVA and PTFE to maximum levels. Experimental validation confirmed that PVA and PTFE contact yields the highest triboelectric performance: VOC of 128 V, ISC of 2.83 µA, QSC of 82 nC, and an output power of 384 µW. Moreover, P-TENG, made of PVA and PTFE, was successfully applied in self-powered smart devices and monitored human respiration and bodily movements effectively. These findings offer valuable insights into using PVA in triboelectric nanogenerator technologies.

Harvesting Water Energy through the Liquid-Solid Triboelectrification

The escalating energy and environmental challenges have catalyzed a global shift toward seeking more sustainable, economical, and eco-friendly energy solutions. Water, capturing 35% of the Earth's solar energy, represents a vast reservoir of clean energy. However, current industrial capabilities harness only a fraction of the energy within the hydrological cycle. The past decade has seen rapid advancements in nanoscience and nanomaterials leading to a comprehensive exploration of liquid-solid triboelectrification as a low-carbon, efficient method for water energy harvesting. This review explores two fundamental principle models involved in liquid-solid triboelectrification. On the basis of these models, two distinct types of water energy harvesting devices, including droplet-based nanogenerators and water evaporation-induced nanogenerators, are summarized from their working principles, recent developments, materials, structures, and performance optimization techniques. Additionally, the applications of these nanogenerators in energy harvesting, self-powered sensing, and healthcare are also discussed. Ultimately, the challenges and future prospects of liquid-solid triboelectrification are further explored.

Electrostatic energy-driven contact electrification mechanism from the ReaxFF molecular dynamics perspective

Understanding the underlying principles of contact electrification is critical for more efficient triboelectric nanogenerator (TENG) development. Herein, we use ReaxFF molecular dynamics simulations in conjunction with a charge equilibration method to investigate the contact electrification mechanism in polyisoprene (PI), a natural rubber polymer, when it comes into contact with copper (Cu) and polytetrafluoroethylene (PTFE). The simulations reveal that the charge transfer directions in the PI/Cu and PI/PTFE contact models are opposite, and the amount of charge transfer in the former is substantially less than that in the latter, which are consistent with our TENG measurements. Contact electrification is revealed to be a spontaneous process that occurs to lower electrostatic energy, and the electrostatic energy released during contact electrification of PI/PTFE is greater than that of PI/Cu, which can be correlated with the relative strength of triboelectric charging observed for the two systems. A compression simulation of the PI/Cu contact model reveals that the quantity of charge transfer grows exponentially as compressive strain increases. Despite increasing the total energy of the system due to densification and distortion of the polymer structure, the applied deformation results in an energetically more stable electrostatic arrangement. We also find that the incorporation of a carbonaceous material into a polyisoprene matrix causes a faster increase in the amount of charge transfer with compressive strain, which is governed by a steeper electrostatic energy profile. This study provides an alternative perspective on the contact electrification mechanism, which could be beneficial for the development of energy harvesting devices.

Contact Electrification as an Emerging Strategy for Controlling the Performance of Metal Nanoparticle Catalysts

Contact electrification (CE) is an emerging strategy for controlling the performance of metal nanoparticle (NP) catalysts. The underlying physical principle of this control is the sensitivity of the Fermi level to metal-metal contacts. This change in electronic structure has a direct impact on surface properties and chemical reactivity. The concept article briefly introduces the basic theory of CE and its relationship to catalytic performance. We then highlight selected recent examples of advances in the preparation of hybrid metal NP assemblies, experimental techniques for characterizing CE, and finally applications of CE for altering catalytic performance.

Tailoring morphological and chemical contributions of nanoscale charge transfer for enhanced triboelectric nanogenerators

Triboelectric devices, operating through contact electrification (CE) and electrostatic induction, have shown great promise in energy harvesting applications. However, optimizing charge transfer at the interface remains crucial for enhancing device performance. This study introduces a novel approach to harnessing CE by employing morphological and chemical modifications of polymers. Our strategy involves adjusting the elastomer base to curing agent ratio to fine-tune the chemical properties of polydimethylsiloxane (PDMS) and introducing morphological modifications through a peeling and flipping (P/F) process of PDMS off the Si-substrate. Unlike conventional methods, the P/F-method minimally alters the intrinsic properties of PDMS, creating nanoscale surface corrugations adiabatically. We explore the mechanical, tribological, and electrical properties of the surface at the nano-scale and demonstrate that our approach allows for precise control of energy dissipation and electric potential at the surface, thereby optimizing charge transfer. Furthermore, we show that using a plasma-treated Si-substrate can further increase device performance up to 80% without affecting other properties. This study presents a comprehensive strategy for fine-tuning CE to enhance the performance of triboelectric nanogenerators.

Integrated triboelectric nanogenerator and radiative cooler for all-weather transparent glass surfaces

Sustainable energies from weather are the most ubiquitous and non-depleted resources. However, existing devices exploiting weather-dependent energies are sensitive to weather conditions and geographical locations, making their universal applicability challenging. Herein, we propose an all-weather sustainable glass surface integrating a triboelectric nanogenerator and radiative cooler, which serves as a sustainable device, harvesting energy from raindrops and saving energy on sunny days. By systematically designing transparent, high-performance triboelectric layers, functioning as thermal emitters simultaneously, particularly compatible with radiative cooling components optimized with an evolutionary algorithm, our proposed device achieves optimal performance for all-weather-dependent energies. We generate 248.28 Wm-2 from a single droplet with an energy conversion ratio of 2.5%. Moreover, the inner temperature is cooled down by a maximum of 24.1 °C compared to pristine glass. Notably, as the proposed device is realized to provide high transparency up to 80% in the visible range, we are confident that our proposed device can be applied to versatile applications.

Surfactant Self-Assembly Enhances Tribopositivity of Stretchable Ionic Conductors for Wearable Energy Harvesting and Motion Sensing

Boosting stretchability and electric output is critical for high-performance wearable triboelectric nanogenerators (TENG). Herein, for the first time, a new approach for tuning the composition of surface functional groups through surfactant self-assembly to improve the tribopositivity, where the assembly increases the transferred charge density and the relative permittivity of water polyurethane (WPU). Incorporating bis(trifluoromethanesulfonyl)imide (TFSI-) and alkali metal ions into a mixture of WPU and the surfactant forms a stretchable film that simultaneously functions as positive tribolayer and electrode, preventing the conventional detachment of tribolayer and electrode in long term usage. Further, the conductivity of the crosslinked film reaches 3.3 × 10-3 mS cm-1 while the elongation at break reaches 362%. Moreover, the surfactant self-assembly impedes the adverse impact of the fluorine-containing groups on tribopositivity. Consequently, the charge density reaches 155 µC m-2, being the highest recorded for WPU and stretchable ionic conductor based TENG. This work introduces a novel approach for boosting the output charge density while avoiding the adverse effect of ionic salts in solid conductors through a universal surfactant self-assembly strategy, which can be extended to other materials. Further, the device is used to monitor and harvest the kinetic energy of human body motion.

Valorization of Food Waste: Utilizing Natural Porous Materials Derived from Pomelo-Peel Biomass to Develop Triboelectric Nanogenerators for Energy Harvesting and Self-Powered Sensing

Food waste is an enormous challenge, with implications for the environment, society, and economy. Every year around the world, 1.3 billion tons of food are wasted or lost, and food waste-associated costs are around $2.6 trillion. Waste upcycling has been shown to mitigate these negative impacts. This study's optimized pomelo-peel biomass-derived porous material-based triboelectric nanogenerator (PP-TENG) had an open circuit voltage of 58 V and a peak power density of 254.8 mW/m2. As porous structures enable such triboelectric devices to respond sensitively to external mechanical stimuli, we tested our optimized PP-TENG's ability to serve as a self-powered sensor of biomechanical motions. As well as successfully harvesting sufficient mechanical energy to power light-emitting diodes and portable electronics, our PP-TENGs successfully monitored joint motions, neck movements, and gait patterns, suggesting their strong potential for use in healthcare monitoring and physical rehabilitation, among other applications. As such, the present work opens up various new possibilities for transforming a prolific type of food waste into value-added products and thus could enhance long-term sustainability while reducing such waste.

Catalyst-free contact-electro-catalytic H2O2 synthesis via simple combination of a poly(tetrafluoroethylene) stir bar and ultrasound

Herein, we present a catalyst-free contact-electro-catalytic method for synthesizing hydrogen peroxide (H2O2) by combining continuous agitation with a poly(tetrafluoroethylene) (PTFE) stir bar and ultrasonication. A high H2O2 production rate of 256.6 μM h-1 is achieved under ambient conditions without adding particle catalysts and sacrificial agents, which is competitive with recent advancements in redox technology. Eco-friendliness, convenience and efficiency make this process a promising alternative method for H2O2 synthesis.

Triboelectric Nanogenerators: State of the Art

The triboelectric nanogenerator (TENG), as a novel energy harvesting technology, has garnered widespread attention. As a relatively young field in nanogenerator research, investigations into various aspects of the TENG are still ongoing. This review summarizes the development and dissemination of the fundamental principles of triboelectricity generation. It outlines the evolution of triboelectricity principles, ranging from the fabrication of the first TENG to the selection of triboelectric materials and the confirmation of the electron cloud overlapping model. Furthermore, recent advancements in TENG application scenarios are discussed from four perspectives, along with the research progress in performance optimization through three primary approaches, highlighting their respective strengths and limitations. Finally, the paper addresses the major challenges hindering the practical application and widespread adoption of TENGs, while also providing insights into future developments. With continued research on the TENG, it is expected that these challenges can be overcome, paving the way for its extensive utilization in various real-world scenarios.

Triboelectric Basalt Textiles Efficiently Operating within an Ultrawide Temperature Range

With the continuous upsurge in demand for wearable energy, nanogenerators are increasingly required to operate under extreme environmental conditions. Even though they are at the cutting edge of technology, nanogenerators have difficulty producing high-quality electrical output at very extreme temperatures. Here, a triboelectric basalt textile (TBT) with an ultrawide operational temperature range (from -196 to 520 °C) is created employing basalt material as the main body. The output power density of the TBT, in contrast to most conventional nanogenerators, would counterintuitively rise by 2.3 times to 740.6 mW m-2 after heating to 100 °C because the high temperature will enhance the material's interface polarization and electronic kinetic energy. The TBT retains ≈55% of its initial electrical output even after heating in the flame of an alcohol lamp (520 °C). Surprisingly, the TBTs output voltage may retain over 85% of its initial value even after submerging in liquid nitrogen. The TBTs exceptional resistance to heat and cold indicates its possible use in high and low latitudes, high altitudes, deserts, and even space settings.

Directional Moisture-Wicking Triboelectric Materials Enabled by Laplace Pressure Differences

Wearable sensors are experiencing vibrant growth in the fields of health monitoring systems and human motion detection, with comfort becoming a significant research direction for wearable sensing devices. However, the weak moisture-wicking capability of sensor materials leads to liquid retention, severely restricting the comfort of the wearable sensors. This study employs a pattern-guided alignment strategy to construct microhill arrays, endowing triboelectric materials with directional moisture-wicking capability. Within 2.25 s, triboelectric materials can quickly and directionally remove the droplets, driven by the Laplace pressure differences and the wettability gradient. The directional moisture-wicking triboelectric materials exhibit excellent pressure sensing performance, enabling rapid response/recovery (29.1/37.0 ms), thereby achieving real-time online monitoring of human respiration and movement states. This work addresses the long-standing challenge of insufficient moisture-wicking driving force in flexible electronic sensing materials, holding significant implications for enhancing the comfort and application potential of electronic skin and wearable electronic devices.

Charge Redistribution in Mechanochemical Reactions for Solid Interfaces

Mechanochemical strategies are widely used in various fields, ranging from friction and wear to mechanosynthesis, yet how the mechanical stress activates the chemical reactions at the electronic level is still open. We used first-principles density functional theory to study the rule of the stress-modified electronic states in transmitting mechanical energy to trigger chemical responses for different mechanochemical systems. The electron density redistribution among initial, transition, and final configurations is defined to correlate the energy evolution during reactions. We found that stress-induced changes in electron density redistribution are linearly related to activation energy and reaction energy, indicating the transition from mechanical work to chemical reactivity. The correlation coefficient is defined as the term "interface reactivity coefficient" to evaluate the susceptibility of chemical reactivity to mechanical action for material interfaces. The study may shed light on the electronic mechanism of the mechanochemical reactions behind the fundamental model as well as the mechanochemical phenomena.

Recent advances in wearable flexible electronic skin: types, power supply methods, and development prospects

In recent years, wearable e-skin has emerged as a prominent technology with a wide range of applications in healthcare, health surveillance, human-machine interface, and virtual reality. Inspired by the properties of human skin, arrayed wearable e-skin is a novel technology that offers multifunctional sensing capabilities. It can detect and quantify various stimuli, mimicking the human somatosensory system, and record a wide range of physical and physiological parameters in real time. By combining flexible electronic device units with a data acquisition system, specific functional sensors can be distributed in targeted areas to achieve high sensitivity, resolution, adjustable sensing range, and large-area expandability. This review provides a comprehensive overview of recent advances in wearable e-skin technology, including its development status, types of applications, power supply methods, and prospects for future development. The emphasis of current research is on enhancing the sensitivity and stability of sensors, improving the comfort and reliability of wearable devices, and developing intelligent data processing and application algorithms. This review aims to serve as a scientific reference for the intelligent development of wearable e-skin technology.

Bioinspired integrated triboelectric electronic tongue

An electronic tongue (E-tongue) comprises a series of sensors that simulate human perception of taste and embedded artificial intelligence (AI) for data analysis and recognition. Traditional E-tongues based on electrochemical methods suffer from a bulky size and require larger sample volumes and extra power sources, limiting their applications in in vivo medical diagnosis and analytical chemistry. Inspired by the mechanics of the human tongue, triboelectric components have been incorporated into E-tongue platforms to overcome these limitations. In this study, an integrated multichannel triboelectric bioinspired E-tongue (TBIET) device was developed on a single glass slide chip to improve the device's taste classification accuracy by utilizing numerous sensory signals. The detection capability of the TBIET was further validated using various test samples, including representative human body, environmental, and beverage samples. The TBIET achieved a remarkably high classification accuracy. For instance, chemical solutions showed 100% identification accuracy, environmental samples reached 98.3% accuracy, and four typical teas demonstrated 97.0% accuracy. Additionally, the classification accuracy of NaCl solutions with five different concentrations reached 96.9%. The innovative TBIET exhibits a remarkable capacity to detect and analyze droplets with ultrahigh sensitivity to their electrical properties. Moreover, it offers a high degree of reliability in accurately detecting and analyzing various liquid samples within a short timeframe. The development of a self-powered portable triboelectric E-tongue prototype is a notable advancement in the field and is one that can greatly enhance the feasibility of rapid on-site detection of liquid samples in various settings.

Contact-electro-catalysis (CEC)

Contact-electro-catalysis (CEC) is an emerging field that utilizes electron transfer occurring at the liquid-solid and even liquid-liquid interfaces because of the contact-electrification effect to stimulate redox reactions. The energy source of CEC is external mechanical stimuli, and solids to be used are generally organic as well as in-organic materials even though they are chemically inert. CEC has rapidly garnered extensive attention and demonstrated its potential for both mechanistic research and practical applications of mechanocatalysis. This review aims to elucidate the fundamental principle, prominent features, and applications of CEC by compiling and analyzing the recent developments. In detail, the theoretical foundation for CEC, the methods for improving CEC, and the unique advantages of CEC have been discussed. Furthermore, we outline a roadmap for future research and development of CEC. We hope that this review will stimulate extensive studies in the chemistry community for investigating the CEC, a catalytic process in nature.

Free Radicals Generated in Perfluorocarbon-Water (Liquid-Liquid) Interfacial Contact Electrification and Their Application in Cancer Therapy

Electron transfer during solid-liquid contact electrification has been demonstrated to produce reactive oxygen species (ROS) such as hydroxyl radicals (•OH) and superoxide anion radicals (•O2-). Here, we show that such a process also occurs in liquid-liquid contact electrification. By preparing perfluorocarbon nanoemulsions to construct a perfluorocarbon-water "liquid-liquid" interface, we confirmed that electrons were transferred from water to perfluorocarbon in ultrasonication-induced high-frequency liquid-liquid contact to produce •OH and •O2-. The produced ROS could be applied to ablate tumors by triggering large-scale immunogenic cell death in tumor cells, promoting dendritic cell maturation and macrophage polarization, ultimately activating T cell-mediated antitumor immune response. Importantly, the raw material for producing •OH is water, so the tumor therapy is not limited by the endogenous substances (O2, H2O2, etc.) in the tumor microenvironment. This work provides new perspectives for elucidating the mechanism of generation of free radicals in liquid-liquid contact and provides an excellent tumor therapeutic modality.

Quantifying Dielectric Material Charge Trapping and De-Trapping Ability Via Ultra-Fast Charge Self-Injection Technique

Recently, utilizing the air breakdown effect in the charge excitation strategy proves as an efficient charge injection technique to increase the surface charge density of dielectric polymers for triboelectric nanogenerators (TENGs). However, quantitative characterization of the ability of dielectric polymers to trap reverse charges and the effect on the startup time of secondary self-charge excitation (SSCE) are essential for extensive applications. Here, an ultra-fast charge self-injection technique based on a self-charge excitation strategy is proposed, and a standard method to quantify the charge trapping and de-trapping abilities of 23 traditional tribo-materials is introduced. Further, the relationship among the distribution of dielectric intrinsic deep, shallow trap states, and transportation of trapped charges is systematically analyzed in this article. It shows that the de-trapping rate of charges directly determines the reactivation and failure of SSCE. Last, independent of TENG contact efficiency, an ultra-high charge density of 2.67 mC m-2 and an ultra-fast startup time of SSCE are obtained using a 15 µm poly(vinylidene fluoride-trifluoroethylene) film, breaking the historical record for material modification. As a standard for material selection, this work quantifies the charge trapping and de-trapping ability of the triboelectric dielectric series and provides insights for understanding the charge transport in dielectrics.

Influence of MXene Composition on Triboelectricity of MXene-Alginate Nanocomposites

MXenes are highly versatile and conductive 2D materials that can significantly enhance the triboelectric properties of polymer nanocomposites. Despite the growing interest in the tunable chemistry of MXenes for energy applications, the effect of their chemical composition on triboelectric power generation has yet to be thoroughly studied. Here, we investigate the impact of the chemical composition of MXenes, specifically the Ti3CNTx carbonitride vs the most studied carbide, Ti3C2Tx, on their interactions with sodium alginate biopolymer and, ultimately, the performance of a triboelectric nanogenerator (TENG) device. Our results show that adding 2 wt % of Ti3CNTx to alginate produces a synergistic effect that generates a higher triboelectric output than the Ti3C2Tx system. Spectroscopic analyses suggest that a higher oxygen and fluorine content on the surface of Ti3CNTx enhances hydrogen bonding with the alginate matrix, thereby increasing the surface charge density of the alginate oxygen atoms. This was further supported by Kelvin probe force microscopy, which revealed a more negative surface potential on Ti3CNTx-alginate, facilitating high charge transfer between the TENG electrodes. The optimized Ti3CNTx-alginate nanogenerator delivered an output of 670 V, 15 μA, and 0.28 W/m2. Additionally, we demonstrate that plasma oxidation of the MXene surface further enhances triboelectric performance. Due to the diverse surface terminations of MXene, we show that Ti3CNTx-alginate can function as either tribopositive or tribonegative material, depending on the counter-contacting material. Our findings provide a deeper understanding of how MXene composition affects their interaction with biopolymers and resulting tunable triboelectrification behavior. This opens up new avenues for developing flexible and efficient MXene-based TENG devices.