Wind Aggregation Enhanced Triboelectric-Electromagnetic Hybrid Generator with Slit Effect

It is of great significance to establish a low-cost, high-efficiency, self-powered micrometeorological monitoring system for agriculture, animal husbandry, and transportation. However, each additional detection element in the meteorological monitoring system increases the power consumption of the whole system by about 0.7 W. As a renewable energy technology, a triboelectric nanogenerator has the advantages of low price and self-powered sensing. To reduce the power consumption of the micrometeorological monitoring system, this work introduces an innovative solution: the wind-gathering enhanced triboelectric-electromagnetic hybrid generator (WGE-TEHG). Coupling the thin-film vibrating triboelectric nanogenerator (TENG) and electromagnetic generator (EMG), the TENG is used to monitor wind direction and the EMG is used to monitor wind speed and provide energy needed by the system. In particular, the TENG can be used as a self-powered sensor to reduce the power consumption of the sensing system. Besides, the TENG is used to produce slit effect to enhance the output performance of EMG. The experimental results show that the WGE-TEHG can build a self-powered natural environment micrometeorological sensing system. It can monitor the wind direction, wind speed, temperature, and relative humidity. This research has great application value for the self-powered sensing implementation of a hybrid TENG and EMG.

Environmentally Robust Triboelectric Tire Monitoring System for Self-Powered Driving Information Recognition via Hybrid Deep Learning in Time-Frequency Representation

Developing a robust artificial intelligence of things (AIoT) system with a self-powered triboelectric sensor for harsh environment is challenging because environmental fluctuations are reflected in triboelectric signals. This study presents an environmentally robust triboelectric tire monitoring system with deep learning to capture driving information in the triboelectric signals generated from tire-road friction. The optimization of the process and structure of a laser-induced graphene (LIG) electrode layer in the triboelectric tire is conducted, enabling the tire to detect universal driving information for vehicles/robotic mobility, including rotation speeds of 200-2000 rpm and contact fractions of line. Employing a hybrid model combining short-term Fourier transform with a convolution neural network-long short-term memory, the LIG-based triboelectric tire monitoring (LTTM) system decouples the driving information, such as traffic lines and road states, from varied environmental conditions of humidity (10%-90%) and temperatures (50-70 °C). The real-time line and road state recognition of the LTTM system is confirmed on a mobile platform across diverse environmental conditions, including fog, dampness, intense sunlight, and heat shimmer. This work provides an environmentally robust monitoring AIoT system by introducing a self-powered triboelectric sensor and hybrid deep learning for smart mobility.

Coaxial Flexible Fiber-Shaped Triboelectric Nanogenerator Assisted by Deep Learning for Self-Powered Vibration Monitoring

Self-powered vibration sensor is highly desired for distributed and continuous monitoring requirements of Industry 4.0. Herein, a flexible fiber-shaped triboelectric nanogenerator (F-TENG) with a coaxial core-shell structure is proposed for the vibration monitoring. The F-TENG exhibits higher adaptability to the complex surfaces, which has an outstanding application prospect due to vital compensation for the existing rigid sensors. Initially, the contact characteristics between the dielectric layers, that related to the perceiving performance of the TENG, are theoretically analyzed. Such a TENG with 1D structure endows high sensitivity, allowing for accurately responding to a wide range of vibration frequencies (0.1 to 100 Hz). Even applying to the real diesel engine, the error in detecting the vibration frequencies is only 0.32% compared with the commercial vibration sensor, highlighting its potential in practical application. Further, assisted by deep learning, the recognition accuracy in monitoring nine operating conditions of the system achieves 97.87%. Overall, the newly designed F-TENG with the merits of high-adaptability, cost-efficiency, and self-powered, has offered a promising solution to fulfill an extensive range of vibration sensing applications in the future.

Durable Roller-Based Swing-Structured Triboelectric Nanogenerator for Water Wave Energy Harvesting

Ocean energy is a kind of clean and renewable energy source, but it cannot be efficiently harvested by traditional electromagnetic generators, due to its low-frequency characteristic. The emergence of triboelectric nanogenerators provides a more promising technology for collecting ocean energy. In this work, a durable roller-based swing-structured triboelectric nanogenerator (RS-TENG) is designed and fabricated for low-frequency water wave energy harvesting. The rolling structure reduces the wear between triboelectric materials and improves the device's durability. After a continuous operation of 1 260 000 cycles, the attenuation of the electrical outputs of the RS-TENG is below 1.6%, exhibiting excellent durability. At the same time, the output current can arrive at 53.2 µA. Under the triggering of water waves, the RS-TENG can generate an output power of 4.27 mW, corresponding to a power density of 1.16 W m-3. After the arraying, the output performance can be doubled, so that the TENG can successfully power an environmental monitoring sensor and ensure long-term stable operation of the sensor. This work provides an effective strategy for improving the device durability, which benefits the practical applications of the TENGs in large-scale blue energy harvesting.

A Flexible, Adaptive, and Self-Powered Triboelectric Vibration Sensor with Conductive Sponge-Silicone for Machinery Condition Monitoring

Vibration sensors for continuous and reliable condition monitoring of mechanical equipment, especially detection points of curved surfaces, remain a great challenge and are highly desired. Herein, a highly flexible and adaptive triboelectric vibration sensor for high-fidelity and continuous monitoring of mechanical vibration conditions is proposed. The sensor is entirely composed of flexible materials. It consists of a conductive sponge-silicone layer and a fluorinated ethylene propylene film. It can detect vibration acceleration of 5 to 50 m s-2 and vibration frequency of 10 to 100 Hz. It has strong robustness and stability, and the output performance barely changes after the durability test of 168 000 working cycles. Additionally, the flexible sensor can work even when the detection point of the mechanical equipment is curved, and the linear fit of the output voltage and acceleration is very close to that when the detection point is flat. Finally, it can be applied to monitoring the working condition of blower and vehicle engine, and can transmit vibration signal to mobile phone application through Wi-Fi module for real-time monitoring. The flexible triboelectric vibration sensor is expected to provide a practical paradigm for smart, green, and sustainable wireless sensor system in the era of Internet of Things.

A Fully Self-Powered Ocean Wave Observation System Empowered by Natural Light Modulated by a Friction-Driven Polymer Network Liquid Crystal

Conventional ocean wave observation instruments are powered by batteries, limiting the continuous observation time. Besides, the waste of batteries brings environmental contaminations. Triboelectric nanogenerators (TENGs) can reveal ocean wave information through their electrical output, taking the triboelectric charge as the information carrier. However, charge amplification is necessary, consuming additional energy. Herein, taking the photons rather than electrons as the information carrier, we developed a fully self-powered natural light-enabled sensing system for ocean wave monitoring by coupling two rotary-freestanding sliding TENGs (RFS-TENGs) and a polymer network liquid crystal (PNLC)-triggered optical system. The natural light is modulated by the PNLC driven by ocean wave-induced friction. With the assistance of a one-way bearing, the rise and fall of the wave will trigger different RFS-TENGs to power the PNLC in different voltage drops, leading to different transmitted natural light intensities. The wave height information can be obtained through the number of pulse signals with the same trough light intensity, while the wave period can be obtained through the duration between the same two sets of pulse signals. The effectiveness of the developed sensing paradigm in practical applications was verified by flume-based experiments, with the highest accuracies of 90.7% in wave height and 99.8% in wave period.

Multistrand Twisted Triboelectric Kevlar Yarns for Harvesting High Impact Energy, Body Injury Location and Levels Evaluation

Developing ultrahigh-strength fabric-based triboelectric nanogenerators for harvesting high-impact energy and sensing biomechanical signals is still a great challenge. Here, the constraints are addressed by design of a multistrand twisted triboelectric Kevlar (MTTK) yarn using conductive and non-conductive Kevlar fibers. Manufactured using a multistrand twisting process, the MTTK yarn offers superior tensile strength (372 MPa), compared to current triboelectric yarns. In addition, a self-powered impact sensing fabric patch (SP-ISFP) comprising signal acquisition, processing, communication circuit, and MTTK yarns is integrated. The SP-ISFP features withstanding impact (4 GPa) and a sensitivity and response time under the high impact condition (59.68 V GPa-1 ; 0.4 s). Furthermore, a multi-channel smart bulletproof vest is developed by the array of 36 SP-ISFPs, enabling the reconstruction of impact mapping and assessment of body injury location and levels by real-time data acquisition. Their potential to reduce body injuries, professional security, and construct a multi-point personal vital signs dynamic monitoring platform holds great promise.

Cellulose Nanofiber-Based Triboelectric Nanogenerators for Efficient Air Filtration in Harsh Environments

Advanced portable healthcare devices with high efficiencies, small pressure drops, and high-temperature resistance are urgently desired in harsh environments with high temperatures, high humidities, and high levels of atmospheric pollution. Triboelectric nanogenerators (TENGs), which serve as energy converters in a revolutionary self-powered sensor device, present a sustainable solution for meeting these requirements. In this work, we developed a porous negative triboelectric material by synthesizing ZIF-8 on the surface of a cellulose/graphene oxide aerogel, grafting it with trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane, and adding a negative corona treatment, and it was combined with a positive triboelectric material to create a cellulose nanofiber-based TENG self-powered filter. The devices achieved a balance between a small pressure drop (53 Pa) and high filtration efficiency (98.97%, 99.65%, and 99.93% for PM0.3, PM0.5, and PM1, respectively), demonstrating robust filtration properties at high temperatures and high humidities. Our work provides a new approach for developing self-powered wearable healthcare devices with excellent air filtration properties.

Fish Scale for Wearable, Self-Powered TENG

Flexible and wearable devices are attracting more and more attention. Herein, we propose a self-powered triboelectric nanogenerator based on the triboelectric effect of fish scales. As the pressure on the nanogenerator increases, the output voltage of the triboelectric nanogenerator increases. The nanogenerator can output a voltage of 7.4 V and a short-circuit current of 0.18 μA under a pressure of 50 N. The triboelectric effect of fish scales was argued to be related to the lamellar structure composed of collagen fiber bundles. The nanogenerator prepared by fish scales can sensitively perceive human activities such as walking, finger tapping, and elbow bending. Moreover, fish scales are a biomass material with good biocompatibility with the body. The fish-scale nanogenerator is a kind of flexible, wearable, and self-powered triboelectric nanogenerator showing great prospects in healthcare and body information monitoring.

A Rolling-Bead Triboelectric Nanogenerator for Harvesting Omnidirectional Wind-Induced Energy toward Shelter Forests Monitoring

Shelter forests (or shelter-belts), while crucial for climate regulation, lack monitoring systems, e.g., Internet of Things (IoT) devices, but their abundant wind energy can potentially power these devices using the trees as mounting points. To harness wind energy, an omnidirectional fluid-induced vibration triboelectric nanogenerator (OFIV-TENG) has been developed. The device is installed on shelter forest trees to harvest wind energy from all directions, employing a fluid-induced vibration (FIV) mechanism (fluid-responding structure) that can capture and use wind energy, ranging from low wind speeds (vortex vibration) to high wind speeds (galloping). The rolling-bead triboelectric nanogenerator (TENG) can efficiently harvest energy while minimizing wear and tear. Additionally, the usage of double electrodes results in an effective surface charge density of 21.4 µC m-2 , which is the highest among all reported rolling-bead TENGs. The collected energy is utilized for temperature and humidity monitoring, providing feedback on the effect of climate regulation in shelter forests, alarming forest fires, and wireless wind speed warning. In general, this work provides a promising and rational strategy, using natural resources like trees as the supporting structures, and shows broad application prospects in efficient energy collection, wind speed warning, and environmentally friendliness.

Largely Improving the Output Performance of Stretchable Triboelectric Nanogenerators via Thermo-Compressive Technology

Stretchable triboelectric nanogenerators (TENGs) are widely applied in wearable and implantable electronics, smart medical devices, and soft robots. However, it is still a challenge to produce stretchable TENGs with both exceptional elasticity and output performance, which limits their application scope. In this work, high-performance stretchable TENGs are developed through a thermo-compression (TC) fabrication process. In particular, a poly(vinylidene fluoride) film is compactly bound to the elastic thermoplastic polyurethane substrate, which inherits excellent stretchability with a strain of up to 815%. Furthermore, owing to the large surface area, tight contact, and effective vertical transport of tribo-induced charges between the coupled fibrous tribo-layer and soft substrate, the TC composite film-based TENGs exhibit a greater output (2-4 times) than unlaminated film-based TENGs. Additionally, the broad universality of this method is proven using various tribo- and substrate materials. The proposed technology provides a novel and effective approach to conjointly boost the output and stretchability of TENGs, showing encouraging application prospects in self-powered wearable and flexible electronics.

Strategies to Improve the Output Performance of Triboelectric Nanogenerators

Triboelectric nanogenerators (TENGs) can collect and convert random mechanical energy into electric energy, with remarkable advantages including broadly available materials, straightforward preparation, and multiple applications. Over the years, researchers have made substantial advancements in the theoretical and practical aspects of TENG. Nevertheless, the pivotal challenge in realizing full applications of TENG lies in ensuring that the generated output meets the specific application requirements. Consequently, substantial research is dedicated to exploring methods and mechanisms for enhancing the output performance of TENG devices. This review aims to comprehensively examine the influencing factors and corresponding improvement strategies of the output performance based on the contact electrification mechanism and operational principles that underlie TENG technology. This review primarily delves into five key areas of improvement: materials selection, surface modification, component adjustments, structural optimization, and electrode enhancements. These aspects are crucial in tailoring TENG devices to meet the desired performance metrics for various applications.

Triboelectric Nanogenerators for Preventive Health Monitoring

With the improvement in life quality, the increased focus on health has expedited the rapid development of portable preventative-health-monitoring devices. As one of the most attractive sensing technologies, triboelectric nanogenerators (TENGs) are playing a more and more important role in wearable electronics, machinery condition monitoring, and Internet of Things (IoT) sensors. TENGs possess many advantages, such as ease of fabrication, cost-effectiveness, flexibility, material-selection variety, and the ability to collect low-frequency motion, offering a novel way to achieve health monitoring for human beings in various aspects. In this short review, we initially present the working modes of TENGs based on their applications in health monitoring. Subsequently, the applications of TENG-based preventive health monitoring are demonstrated for different abnormal conditions of human beings, including fall-down detection, respiration monitoring, fatigue monitoring, and arterial pulse monitoring for cardiovascular disease. Finally, the discussion summarizes the current limitations and future perspectives. This short review encapsulates the latest and most influential works on preventive health monitoring utilizing the triboelectric effect for human beings and provides hints and evidence for future research trends.

Triboelectric Nanogenerators Based on Fluid Medium: From Fundamental Mechanisms toward Multifunctional Applications

Fluid-based triboelectric nanogenerators (FB-TENGs) are at the forefront of promising energy technologies, demonstrating the ability to generate electricity through the dynamic interaction between two dissimilar materials, wherein at least one is a fluidic medium (such as gas or liquid). By capitalizing on the dynamic and continuous properties of fluids and their interface interactions, FB-TENGs exhibit a larger effective contact area and a longer-lasting triboelectric effect in comparison to their solid-based counterparts, thereby affording longer-term energy harvesting and higher-precision self-powered sensors in harsh conditions. In this review, various fluid-based mechanical energy harvesters, including liquid-solid, gas-solid, liquid-liquid, and gas-liquid TENGs, have been systematically summarized. Their working mechanism, optimization strategies, respective advantages and applications, theoretical and simulation analysis, as well as the existing challenges, have also been comprehensively discussed, which provide prospective directions for device design and mechanism understanding of FB-TENGs.

Maximizing Triboelectric Nanogenerators by Physics-Informed AI Inverse Design

Triboelectric nanogenerators offer an environmentally friendly approach to harvesting energy from mechanical excitations. This capability has made them widely sought-after as an efficient, renewable, and sustainable energy source, with the potential to decrease reliance on traditional fossil fuels. However, developing triboelectric nanogenerators with specific output remains a challenge mainly due to the uncertainties associated with their complex designs for real-life applications. Artificial intelligence-enabled inverse design is a powerful tool to realize performance-oriented triboelectric nanogenerators. This is an emerging scientific direction that can address the concerns about the design and optimization of triboelectric nanogenerators leading to a next generation nanogenerator systems. This perspective paper aims at reviewing the principal analysis of triboelectricity, summarizing the current challenges of designing and optimizing triboelectric nanogenerators, and highlighting the physics-informed inverse design strategies to develop triboelectric nanogenerators. Strategic inverse design is particularly discussed in the contexts of expanding the four-mode analytical models by physics-informed artificial intelligence, discovering new conductive and dielectric materials, and optimizing contact interfaces. Various potential development levels of artificial intelligence-enhanced triboelectric nanogenerators are delineated. Finally, the potential of physics-informed artificial intelligence inverse design to propel triboelectric nanogenerators from prototypes to multifunctional intelligent systems for real-life applications is discussed.

Bulk Schottky Junctions-Based Flexible Triboelectric Nanogenerators to Power Backscatter Communications in Green 6G Networks

This work introduces a novel method to construct Schottky junctions to boost the output performance of triboelectric nanogenerators (TENGs). Perovskite barium zirconium titanate (BZT) core/metal silver shell nanoparticles are synthesized to be embedded into electrospun polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) nanofibers before they are used as tribo-negative layers. The output power of TENGs with composite fiber mat exhibited >600% increase compared to that with neat polymer fiber mat. The best TENG achieved 1339 V in open-circuit voltage, 40 µA in short-circuit current and 47.9 W m-2 in power density. The Schottky junctions increased charge carrier density in tribo-layers, ensuring a high charge transfer rate while keeping the content of conductive fillers low, thus avoiding charge loss and improving performance. These TENGs are utilized to power radio frequency identification (RFID) tags for backscatter communication (BackCom) systems, enabling ultra-massive connectivity in the 6G wireless networks and reducing information communications technology systems' carbon footprint. Specifically, TENGs are used to provide an additional energy source to the passive tags. Results show that TENGs can boost power for BackCom and increase the communication range by 386%. This timely contribution offers a novel route for sustainable 6G applications by exploiting the expanded communication range of BackCom tags.

Compositional Engineering of Hybrid Organic-Inorganic Lead-Halide Perovskite and PVDF-Graphene for High-Performance Triboelectric Nanogenerators

Triboelectric nanogenerators (TENGs) have attracted a great deal of attention since they can convert ubiquitous mechanical energy into electrical energy and serve as a continuous power source for self-powered sensors. Optimization of the dielectric material composition is an effective way to improve the triboelectric output performance of TENGs. Herein, the hybrid organic-inorganic lead-iodide perovskite Cs0.05FA0.95-xMAxPbI3 was prepared by blade coating and used as a positive friction layer material. Moreover, PVDF-graphene (PG) nanofibers were prepared as negative friction layer materials by electrostatic spinning. The output performance of the TENG was enhanced by varying the MA content of the pervoskite films and the graphene content of the PG nanofibers. The champion output TENG based on Cs0.05FA0.9MA0.05PbI3/PG-0.15 achieved an open-circuit voltage of 245 V, a short-circuit current of 24 μA, and a charge transfer of 80.2 nC. Meanwhile, a maximum power density of 11.23 W m-2 was obtained at 100 MΩ. Moreover, the device exhibits excellent energy-harvesting properties, including excellent stability and durability, rapidly charges capacitors, and lights commercial LEDs and digital tubes.

Nanofibrous PAN-PDMS Films-Based High-Performance Triboelectric Artificial Whisker for Self-Powered Obstacle Detection

Avoiding collisions is a key necessity for any autonomous mobile robot, and obstacle mapping enables them to maneuver in an uncharted area. In this era of the Internet of Things, with the emerging need for a multitude of sensors, adopting self-powered technologies is more practically viable than batteries for powering the same. Herein, with the fabrication of a triboelectric artificial whisker (TAW), a self-powered obstacle detection is demonstrated via tactile perception. The mechanical contact with the obstacle gives rise to an electrical signal from the TAW owing to the embedded triboelectric sensor. In addition, the triboelectric nanogenerator (TENG) based on electrospun polyacrylonitrile (PAN) nanofibers and polydimethylsiloxane film, which facilitates this self-powered artificial sensation, generates an output voltage of 720 V and current density of 5 mA m-2 with 1.7 W m-2 of maximum power delivery from a force of 10 N. The electro-spinning aided enhancement in contact area of the PAN is responsible for the remarkable improvement in the performance of the TENG, 3.4 times enhancement in power density, when compared to the nonsurface-modified ones. In addition, the TENG is able to charge commercial capacitors up to appreciable values and demonstrates powering different electronic gadgets such as calculators and thermometers.

Revamping Triboelectric Output by Deep Trap Construction

High output performance is critical for building triboelectric nanogenerators (TENGs) for future multifunctional applications. Unfortunately, the high triboelectric charge dissipation rate has a significant negative impact on its electrical output performance. Herein, a new tribolayer is designed through introducing self-assembled molecules with large energy gaps on commercial PET fibric to form carrier deep traps, which improve charge retention while decreasing dissipation rates. The deep trap density of the PET increases by two orders of magnitude, resulting in an 86% reduction in the rate of charge dissipation and a significant increase in the charge density that can be accumulated on tribolayer during physical contact. The key explanation is that increasing the density of deep traps improves the dielectric's ability to store charges, making it more difficult for the triboelectric charges trapped by the tribolayer to escape from the deep traps, lowering the rate of charge dissipation. This TENG has a 1300% increase in output power density as a result of altering the deep trap density, demonstrating a significant improvement. This work describes a simple yet efficient method for building TENGs with ultra-high electrical output and promotes their practical implementation in the sphere of the Internet of Things.

Underwater Biomimetic Lateral Line Sensor Based on Triboelectric Nanogenerator for Dynamic Pressure Monitoring and Trajectory Perception

Developing desirable sensors is crucial for underwater perceptions and operations. The perceiving organs of marine creatures have greatly evolved to react accurately and promptly underwater. Inspired by the fish lateral line, this study proposes a triboelectric dynamic pressure sensor for underwater perception. The biomimetic lateral line sensor (BLLS) has high sensitivity to the disturbance amplitude/frequency, good adaptability to underwater environments and (relative) low cost. The sensors are deployed at the bottom of the test basin to perceive various moving objects, such as a robotic fish, robotic seal, etc. By analyzing the electrical signal of the sensor, the motion parameters of the objects passed over can be obtained. By monitoring signal variations across multiple sensors, the ability to sense different disturbance movement trajectories, including linear and angular trajectories, is achievable. The study will prove significant in forming an unconventional underwater perceiving method, which can back-up the sonic/optical sensors when are impaired in complex underwater environments.

Electrospun Cellulose Nanocrystals Reinforced Flexible Sensing Paper for Triboelectric Energy Harvesting and Dynamic Self-Powered Tactile Perception

The technical synergy between flexible sensing paper and triboelectric nanogenerator (TENG) in the next stage of artificial intelligence Internet of Things engineering makes the development of intelligent sensing paper with triboelectric function very attractive. Therefore, it is extremely urgent to explore functional papers that are more suitable for triboelectric sensing. Here, a cellulose nanocrystals (CNCs) reinforced PVDF hybrid paper (CPHP) is developed by electrospinning technology. Benefitting from the unique effects of CNCs, CPHP forms a solid cross-linked network among fibers and obtains a high-strength (25 MPa) paper-like state and high surface roughness. Meanwhile, CNCs also improve the triboelectrification effect of CPHP by assisting the PVDF matrix to form more electroactive phases (96% share) and a higher relative permittivity (17.9). The CPHP-based TENG with single electrode configuration demonstrates good output performance (open-circuit voltage of 116 V, short-circuit current of 2.2 µA and power density of 91 mW m-2 ) and ultrahigh pressure-sensitivity response (3.95 mV Pa-1 ), which endows CPHP with reliable power supply and sensing capability. More importantly, the CPHP-based flexible self-powered tactile sensor with TENG array exhibits multifunctional applications in imitation Morse code compilation, tactile track recognition, and game character control, showing great prospects in the intelligent inductive device and human-machine interaction.

A Rotating Triboelectric Nanogenerator Driven by Bidirectional Swing for Water Wave Energy Harvesting

Due to the simple installation and convenient maintenance, the floating water wave energy harvesting devices have significant economic advantages. Mass power density is the most important index to evaluate the advancement of floating wave energy harvesting devices. Herein, a self-adaptive rotating triboelectric nanogenerator (SR-TENG) with a compound pendulum and a functional gear-set is provided for wave energy harvesting. First, a compound pendulum structure with a low center of gravity and high moment of inertia is obtained by the geometric design and mechanical study. Besides, compared with the previous triboelectric nanogenerator with one-way clutch, SR-TENG can harvest twice the kinetic energy utilization through the functional gear-set. Importantly, depending on the structure design, the SR-TENG obtains the average mass power density of 45.18 mW kg-1 under low frequency driving conditions, which is about 10 times the reference electromagnetic generator with a similar structure and size. This result shows that the SR-TENG has a significant advantage in small water wave energy harvesting. These findings provide an important example of the floating water wave energy harvesting devices.

Multi-Layered Triboelectric Nanogenerators with Controllable Multiple Spikes for Low-Power Artificial Synaptic Devices

In the domains of wearable electronics, robotics, and the Internet of Things, there is a demand for devices with low power consumption and the capability of multiplex sensing, memory, and learning. Triboelectric nanogenerators (TENGs) offer remarkable versatility in this regard, particularly when integrated with synaptic transistors that mimic biological synapses. However, conventional TENGs, generating only two spikes per cycle, have limitations when used in synaptic devices requiring repetitive high-frequency gating signals to perform various synaptic plasticity functions. Herein, a multi-layered micropatterned TENG (M-TENG) consisting of a polydimethylsiloxane (PDMS) film and a composite film that includes 1H,1H,2H,2H-perfluorooctyltrichlorosilane/BaTiO3 /PDMS are proposed. The M-TENG generates multiple spikes from a single touch by utilizing separate triboelectric charges at the multiple friction layers, along with a contact/separation delay achieved by distinct spacers between layers. This configuration allows the maximum triboelectric output charge of M-TENG to reach up to 7.52 nC, compared to 3.69 nC for a single-layered TENG. Furthermore, by integrating M-TENGs with an organic electrochemical transistor, the spike number multiplication property of M-TENGs is leveraged to demonstrate an artificial synaptic device with low energy consumption. As a proof-of-concept application, a robotic hand is operated through continuous memory training under repeated stimulations, successfully emulating long-term plasticity.

Implantable Triboelectric Nanogenerators for Self-Powered Cardiovascular Healthcare

Triboelectric nanogenerators (TENGs) have gained significant traction in recent years in the bioengineering community. With the potential for expansive applications for biomedical use, many individuals and research groups have furthered their studies on the topic, in order to gain an understanding of how TENGs can contribute to healthcare. More specifically, there have been a number of recent studies focusing on implantable triboelectric nanogenerators (I-TENGs) toward self-powered cardiac systems healthcare. In this review, the progression of implantable TENGs for self-powered cardiovascular healthcare, including self-powered cardiac monitoring devices, self-powered therapeutic devices, and power sources for cardiac pacemakers, will be systematically reviewed. Long-term expectations of these implantable TENG devices through their biocompatibility and other utilization strategies will also be discussed.

Passive Internet of Events Enabled by Broadly Compatible Self-Powered Visualized Platform Toward Real-Time Surveillance

Surveillance is an intricate challenge worldwide especially in those complicated environments such as nuclear plants, banks, crowded areas, barns, etc. Deploying self-powered wireless sensor nodes can increase the system's event detection capabilities by collecting environmental changes, while the incompatibility among components (energy harvesters, sensors, and wireless modules) limits their application. Here, a broadly compatible self-powered visualized platform (SPVP) is reported to construct a passive internet of events (IoE) network for surveillance systems. By encoding electric signals into reference and working LEDs, SPVP can visualize resistance change generated by commercial resistive sensors with a broad working range (<107  Ω) and the transmission distance is up to 30 meters. Visible light signals are captured by surveillance cameras and processed by the cloud to achieve real-time event monitoring and identification, which forms the passive IoE network. It is demonstrated that the passive-IoE-based surveillance system can detect intrusion, theft, fire alarm, and distress signals quickly (30 ms) for 106 cycles. Moreover, the confidential information can be encrypted by SPVPs and accessed through a phone application. This universal scheme may have huge potential for the construction of safe and smart cities.

Fully Wireless and Self-Powered Ocean Wave Observation System Empowered by the Friction-Driven Polymer Network Liquid Crystal-Based Smart Reflector

Current ocean wave observation is achieved by separate battery-powered sensing and signal transmission modules. Owing to the limited electrical supply and information channel space, the long-time span observation is restricted and only wave height and period information rather than the whole wave profile are sent back to the receiver. In this work, a self-powered ocean wave observation system was achieved by a developed polymer network liquid crystal (PNLC)-based smart reflector powered by a tailored triboelectric nanogenerator embedded with one-way overrunning clutches. The off-shore smart reflector modulated the on-shore emitted laser light, where ocean wave motion information can be revealed from the remotely detected reflected laser light without cable connections. The ocean wave rise and fall are distinguished by the developed one-way overrunning clutch, which selects the TENG to power the PNLC. Through the developed paradigm, ocean wave sensing and signal transmission can be achieved simultaneously, which is fully self-powered and free-of-cable. The flume-based self-powered ocean observation was performed with demonstrated wave height and period sensing accuracies of 92.66 and 97.32%, respectively.

Polyvinyl alcohol-based economical triboelectric nanogenerator for self-powered energy harvesting applications

Triboelectric nanogenerators (TENGs) have emerged as a promising alternative for powering small-scale electronics without relying on traditional power sources, and play an important role in the development of the internet of things (IoTs). Herein, a low-cost, flexible polyvinyl alcohol (PVA)-based TENG (PVA-TENG) is reported to harvest low-frequency mechanical vibrations and convert them into electricity. PVA thin film is prepared by a simple solution casting technique and utilized to serve as the tribopositive material, polypropylene film as tribonegative, and aluminum foil as electrodes of the device. The dielectric-dielectric model is implemented with an arch structure for the effective working of the PVA-TENG. The device showed promising electrical output by generating significant open-circuit voltage, short-circuit current, and power . Also, PVA-TENG is subjected to a stability test by operating the device continuously for 5000 cycles. The result shows that, the device is mechanically durable and electrically stable. Further, the as-fabricated PVA-TENG is demonstrated to show feasible applications, such as charging two commercial capacitors with capacitances 1.1 and 4.7μF and powering green light-emitting diodes. The stored energy in the 4.7μF capacitor is utilized to power a digital watch and humidity and temperature sensor without the aid of an external battery. Thus, the PVA-TENG facilitates ease of fabrication, robustness, and cost-effective strategy in the field of energy harvesting for powering lower-grid electronics by demonstrating their potential as a sustainable energy source.

Mechano-Driven Tribo-Electrophoresis Enabled Human-Droplet Interaction in 3D Space

Electronically controlled droplet manipulation has widespread applications in biochemistry, life sciences, and industry. However, current technologies such as electrowetting, electrostatics, and surface charge printing rely on complex electrode arrays and external power supplies, leading to inefficient manipulation. In light of these limitations, a novel method is proposed, which leverages tribo-electrophoresis (TEP) to pipette in an oil medium, thereby enabling human-droplet interactions to be constructed with greater efficiency. The approach involves the rational design of a triboelectric nanogenerator-electrostatic tweezer that generates an electric field to charge the droplet and improves the maneuverability of the charged droplet, including aligned/non-aligned pipetting and stable transport in the clamped state, which can be accomplished solely by hand motion. The TEP method not only provides droplets with freedom to move in three dimensions but also offers a feasibility case for chemical reactions in the liquid phase and non-invasive sample extraction. This breakthrough establishes a cornerstone for human-droplet interactions capitalized on triboelectric nanogenerators, opening new avenues for research in droplet manipulation.

Boosting Output Performance of Sliding Mode Triboelectric Nanogenerator by Shielding Layer and Shrouded-Tribo-Area Optimized Ternary Electrification Layered Architecture

Sliding mode triboelectric nanogenerator (S-TENG) is effective for low-frequency mechanical energy harvesting owing to their more efficient mechanical energy extraction capability and easy packaging. Ternary electrification layered (TEL) architecture is proven useful for improving the output performance of S-TENG. However, the bottleneck of electric output is the air breakdown on the interface of tribo-layers, which seriously restricts its further improvement. Herein, a strategy is adopted by designing a shielding layer to prevent air breakdown on the central surface of tribo-layers. And the negative effects of air breakdown on the edge of sliding layer are averted by increasing the shrouded area of tribo-layers on slider. Output charge of this shielding-layer and shrouded-tribo-area optimized ternary electrification layered triboelectric nanogenerator (SS-TEL-TENG) achieves 3.59-fold enhancement of traditional S-TENG and 1.76-fold enhancement of TEL-TENG. Furthermore, even at a very low speed of 30 rpm, output charge, current, and average power of the rotation-type SS-TEL-TENG reach 4.15 µC, 74.9 µA, and 25.4 mW (2.05 W m-2 Hz-1 ), respectively. With such high-power output, 4248 LEDs can be lighted brightly by SS-TEL-TENG directly. The high-performance SS-TEL-TENG demonstrated in this work will have great applications for powering ubiquitous sensor network in the Internet of Things (IoT).

Lignocellulosic Biomass for the Fabrication of Triboelectric Nano-Generators (TENGs)-A Review

Growth in population and increased environmental awareness demand the emergence of new energy sources with low environmental impact. Lignocellulosic biomass is mainly composed of cellulose, lignin, and hemicellulose. These materials have been used in the energy industry for the production of biofuels as an eco-friendly alternative to fossil fuels. However, their use in the fabrication of small electronic devices is still under development. Lignocellulose-based triboelectric nanogenerators (LC-TENGs) have emerged as an eco-friendly alternative to conventional batteries, which are mainly composed of harmful and non-degradable materials. These LC-TENGs use lignocellulose-based components, which serve as electrodes or triboelectric active materials. These materials can be derived from bulk materials such as wood, seeds, or leaves, or they can be derived from waste materials from the timber industry, agriculture, or recycled urban materials. LC-TENG devices represent an eco-friendly, low-cost, and effective mechanism for harvesting environmental mechanical energy to generate electricity, enabling the development of self-powered devices and sensors. In this study, a comprehensive review of lignocellulosic-based materials was conducted to highlight their use as both electrodes and triboelectric active surfaces in the development of novel eco-friendly triboelectric nano-generators (LC-TENGs). The composition of lignocellulose and the classification and applications of LC-TENGs are discussed.

Fabrication of high-performance triboelectric nanogenerator based on Ni3C nanosheets to self-power thermal patch for pain relief

In this work, we report a vertical contact-separation mode triboelectric nanogenerators (TENG) comprising of Ni3C/PDMS composite and Nylon Nanofibers for self-powering a nichrome wire-based thermal patch for muscular/joint relaxation. An optimised composition of Ni3C (25 wt%) and PDMS as a tribo-negative material and Nylon Nanofibers synthesised via electrospinning on copper electrode foil as a tribo-positive material were used to fabricate the TENG. The fabricated TENG exhibits outstanding output generating an average open circuit voltage of ∼252 V, an average short circuit current of ∼40.87μA and a peak power of ∼562.35μW cm-2at a matching resistance of 20 MΩ by manual tapping. Enhancement in contact area due to electrospun nylon and micro capacitive Ni3C flakes in dielectric PDMS contribute to the exceptional performance of the TENG. The optimised TENG is then connected to a full bridge rectifier with a 100 nF filtering capacitor to convert the AC voltage to a DC output with a peak voltage of ∼5.4 V and a ripple voltage of ∼1.04 V to recharge an ICR 18650 Li-ion battery, which functions as a medium to improve electrical energy flow to the heat patch. The electrical energy is converted into heat energy by a wounded nichrome wire placed inside the heat patch. The nichrome wire of length 3 cm with appropriate number of windings was employed in the heat patch. An increment of 45 °F can be observed by switching the charged Li-ion battery-based circuit ON for just 30 s. The strategy of self-powering a heat patch using this TENG finds enormous applications in physiotherapy and sports to relieve muscle and joint pains.

Enhancing Output Signals of Sport Monitors Based on Triboelectric Porous PVDF Nanogenerators via Concaving Cells and Cell-Packing Structures

Porous triboelectric polymer materials are widely used in portable sensors due to their lightweight and suitable mechanical performance, but their triboelectric properties need to be improved. Here, we propose a two-step strategy to concave the cell and cell-packing structure of triboelectric materials based on porous poly(vinylidene fluoride) (PVDF). The first step is to prepare triboelectric nanogenerators (TENGs) of PVDF with a concave cell-packing structure via oriented phase inversion. The second step is to concave the cells by radial and axial compression. The results reveal that the concavities in the cell structure at the radial direction and in the cell-packing structure at the axial direction improve the output signals of the porous PVDF TENG by ca. 150 and 110%, respectively. By contrast, the concaving in cell structure at the radial direction exerts a positive effect on triboelectric performance only when the radial compression strain is not bigger than 17.5%, especially when the cell wall is thin (ca. 0.85 μm). Meanwhile, the concavity-based strategy eliminates the irreversible deformation behavior of the porous PVDF material, enhancing its elasticity. The stability test shows that the sensor based on those materials is stable under 12,500 cycles, and the variance in the square derivation of output voltage is less than 1% during the cycle friction. Such stable and triboelectric-improved materials are assembled into sports-monitoring devices, providing an idea for the application of TENG in smart sensing.

Design and Fabrication of Polymer Triboelectric Nanogenerators for Self-Powered Insole Applications

Triboelectric nanogenerators (TENGs) are a kind of mechanical energy harvester with a larger force sensing range and good energy conversion, which is often applied to human kinetic energy collection and motion sensing devices. Polymer materials are the most commonly used materials in TENGs' triboelectric layers due to their high plasticity and good performance. Regarding the application of TENGs in insoles, research has often used brittle Teflon for high output performance together with hard materials, such as springs, for the mechanism to maintain its stability. However, these combined materials increase the weight and hardness of the insoles. Here, we propose a polyethylene terephthalate (PET)-based TENG with a micro-needle polydimethylsiloxane (PDMS) elastomer, referred to as MN-PDMS-TENG, to enhance performance and maintain comfort flexibility, and structural stability. Compared with a flat PDMS, the TENG with a microstructure enhances the output open-circuit voltage (Voc) from 54.6 V to 129.2 V, short-circuit current (Isc) from 26.16 μA to 64.00 μA, power from 684 µW to 4.1 mW, and ability to light up from 70 to 120 LEDs. A special three-layer TENG insole mechanism fabricated with the MN-PDMS-TENG and elastic materials gives the TENG insole high stability and the ability to maintain sufficient flexibility to fit in a shoe. The three-layer TENG insole transforms human stepping force into electric energy of 87.2 V, which is used as a self-powered force sensor. Moreover, with the calibration curve between voltage and force, it has a sensitivity of 0.07734 V/N with a coefficient of determination of R2 = 0.91 and the function between force and output voltage is derived as F = 12.93 V - 92.10 under human stepping force (300~550 N). Combined with a micro-control unit (MCU), the three-layer TENG insole distinguishes the user's motion force at different parts of the foot and triggers a corresponding device, which can potentially be applied in sports and on rehabilitation fields to record information or prevent injury.

Wheel-structured Triboelectric Nanogenerators with Hyperelastic Networking for High-Performance Wave Energy Harvesting

Developing clean and renewable energy sources is an important strategy to reduce carbon emission and achieve carbon neutrality. As one of the most promising clean energy sources, large-scale, and efficient utilization of ocean blue energy remains a challenging problem to be solved. In this work, a hyperelastic network of wheel-structured triboelectric nanogenerators (WS-TENGs) is demonstrated to efficiently harvest low-frequency and small-amplitude wave energy. Different from traditional designs of smooth shell, the external blades on the TENG allow tighter interaction between the wave and the device, which can roll on the water surface like a wheel, continuously agitating internal TENGs. Moreover, the hyperelastic networking structure can stretch and shrink like a spring with stored wave energy, further intensifying the roll of the device, and connecting the WS-TENGs to form a large-scale network. Multiple driving modes with synergistic effects can be realized under wave and wind excitations. Self-powered systems are fabricated based on the WS-TENG network, showing the capability of the device in real wave environment. The work provides a new driving paradigm that can further enhance the energy harvesting capability toward large-scale blue energy utilization based on TENGs.

Recent Progress of Advanced Materials for Triboelectric Nanogenerators

Triboelectric nanogenerators (TENGs) have received intense attention due to their broad application prospects in the new era of internet of things (IoTs) as distributed power sources and self-powered sensors. Advanced materials are vital components for TENGs, which decide their comprehensive performance and application scenarios, opening up the opportunity to develop efficient TENGs and expand their potential applications. In this review, a systematic and comprehensive overview of the advanced materials for TENGs is presented, including materials classifications, fabrication methods, and the properties required for applications. In particular, the triboelectric, friction, and dielectric performance of advanced materials is focused upon and their roles in designing the TENGs are analyzed. The recent progress of advanced materials used in TENGs for mechanical energy harvesting and self-powered sensors is also summarized. Finally, an overview of the emerging challenges, strategies, and opportunities for research and development of advanced materials for TENGs is provided.

From Triboelectric Nanogenerator to Hybrid Energy Harvesters: A Review on the Integration Strategy toward High Efficiency and Multifunctionality

The rapid development of smart devices and electronic products puts forward higher requirements for power supply components. As a promising solution, hybrid energy harvesters that are based on a triboelectric nanogenerator (HEHTNG) show advantages of both high energy harvesting efficiency and multifunctionality. Aiming to systematically elaborate the latest research progress of a HEHTNG, this review starts by introducing its working principle with a focus on the combination of triboelectric nanogenerators with various other energy harvesters, such as piezoelectric nanogenerators, thermoelectric/pyroelectric nanogenerators, solar cells, and electromagnetic nanogenerators. While the performance improvement and integration strategies of HEHTNG toward environmental energy harvesting are emphasized, the latest applications of HEHTNGs as multifunctional sensors in human health detection are also illustrated. Finally, we discuss the main challenges and prospects of HEHTNGs, hoping that this work can provide a clear direction for the future development of intelligent energy harvesting systems for the Internet of Things.

A Robust Triboelectric Impact Sensor with Carbon Dioxide Precursor-Based Calcium Carbonate Layer for Slap Match Application

As an urgent international challenge, the sudden change in climate due to global warming needs to be addressed in the near future. This can be achieved through a reduction in fossil fuel utilization and through carbon sequestration, which reduces the concentration of CO2 in the atmosphere. In this study, a self-sustainable impact sensor is proposed through implementing a triboelectric nanogenerator with a CaCO3 contact layer fabricated via a CO2 absorption method. The triboelectric polarity of CaCO3 with the location between the polyimide and the paper and the effects of varying the crystal structure are investigated first. The impact sensing characteristics are then confirmed at various input frequencies and under applied forces. Further, the high mechanical strength and strong adherence of CaCO3 on the surface of the device are demonstrated through enhanced durability compared to the unmodified device. For the intended application, the as-fabricated sensor is used to detect the turning state of the paper Ddakji in a slap match game using a supervised learning algorithm based on a support vector machine presenting a high classification accuracy of 95.8%. The robust CaCO3-based triboelectric device can provide an eco-friendly advantage due to its self-powered characteristics for impact sensing and carbon sequestration.

Flexible Self-Powered Energy Systems Based on H2 O/Ni2+ Intercalated Nix V2 O5 ⋅ nH2 O

The development of portable electronic devices has created greater demands for multifunctional energy integration systems. Self-powered systems have gained widespread interest because they can collect and storage renewable environmental energy and provide stable electricity to electronic devices. Herein, we developed a flexible self-charging energy system, involving textile-based zinc-ion hybrid (ZIHC) and triboelectric nanogenerator (TENG), which demonstrates wearable, compatibility, lightweight and can quickly harvest and store energy. Nix V2 O5  ⋅ nH2 O (NVO) loaded on carbon cloth (CC) with Ni2+ /H2 O ions intercalated as the cathode was assembled with activated CC to form a ZIHC, which has a voltage range of 2.0 V and capacitance value of 267.1 mF cm-2 as well as good charge and discharge rates and excellent cycling stability. At the same time, the NVO/CC can be assembled with PDMS to form a TENG achieving a maximum instantaneous power of 18.5 mW cm-2 . The device can be flexibly worn over the body to continuously harvest and store biomechanical energy and charge the electronic wristwatch successfully. This work demonstrates great convenience and promising practical applications as sustainable flexible energy system for portable electronic devices.

Multifunctional Silk Fibroin/Carbon Nanofiber Scaffolds for In Vitro Cardiomyogenic Differentiation of Induced Pluripotent Stem Cells and Energy Harvesting from Simulated Cardiac Motion

In this proof-of-concept study, cardiomyogenic differentiation of induced pluripotent stem cells (iPSCs) is combined with energy harvesting from simulated cardiac motion in vitro. To achieve this, silk fibroin (SF)-based porous scaffolds are designed to mimic the mechanical and physical properties of cardiac tissue and used as triboelectric nanogenerator (TENG) electrodes. The load-carrying mechanism, β-sheet content, degradation characteristics, and iPSC interactions of the scaffolds are observed to be interrelated and regulated by their pore architecture. The SF scaffolds with a pore size of 379 ± 34 μm, a porosity of 79 ± 1%, and a pore interconnectivity of 67 ± 1% upregulated the expression of cardiac-specific gene markers TNNT2 and NKX2.5 from iPSCs. Incorporating carbon nanofibers (CNFs) enhances the elastic modulus of the scaffolds to 45 ± 3 kPa and results in an electrical conductivity of 0.021 ± 0.006 S/cm. The SF and SF/CNF scaffolds are used as conjugate TENG electrodes and generate a maximum power output of 0.37 × 10-3 mW/m2, with an open-circuit voltage and a short circuit current of 0.46 V and 4.5 nA, respectively, under simulated cardiac motion. A novel approach is demonstrated for fabricating scaffold-based cardiac patches that can serve as tissue scaffolds and simultaneously allow energy harvesting.

Structure-Crack Detection and Digital Twin Demonstration Based on Triboelectric Nanogenerator for Intelligent Maintenance

The accomplishment of condition monitoring and intelligent maintenance for cantilever structure-based energy harvesting devices remains a challenge. Here, to tackle the problems, a novel cantilever-structure freestanding triboelectric nanogenerator (CSF-TENG) is proposed, which can capture ambient energy or transmit sensory information. First, with and without a crack in cantilevers, the simulations are carried out. According to simulation results, the maximum change ratios of natural frequency and amplitude are 1.1% and 2.2%, causing difficulties in identifying defects by these variations. Thus, based on Gramian angular field and convolutional neural network, a defect detection model is established to achieve the condition monitoring of the CSF-TENG, and the experimental result manifests that the accuracy of the model is 99.2%. Besides, the relation between the deflection of cantilevers and the output voltages of the CSF-TENG is first built, and then the defect identification digital twin system is successfully created. Consequently, the system is capable of duplicating the operation of the CSF-TENG in a real environment, and displaying defect recognition results, so the intelligent maintenance of the CSF-TENG can be realized.

A Stretchable Solid Ionic Electrode-Based Triboelectric Nanogenerator for Biomechanical Energy Harvesting and Self-Powered Sensors

Stretchable power devices and self-powered sensors have become increasingly desired for wearable electronics and artificial intelligence. In this study, an all-solid-state triboelectric nanogenerator (TENG) is reported, whose one solid-state structure prevents delamination during stretch and release cycles and increasing the patch adhesive force (3.5 N) and strain (586% elongation at break). Through the synergetic virtues of stretchability, ionic conductivity, and excellent adhesion to the tribo-layer, reproducible open-circuit voltage (VOC ) of 84 V, charge (QSC ) of 27.5 nC, and short-circuit current (ISC ) of 3.1 µA after drying at 60°C or 20,000 contact-separation cycles are obtained. Apart from contact-separation, this device shows unprecedented electricity generation through stretch-release of solid materials leading to a linear relationship between VOC and strain. For the first time, this work provides a clear explanation of the working mechanism of contact-free stretching-releasing and investigates the relationships of exerted force, strain, thickness of the device, and electric output. Benefitting from the one solid-state structure, this contact-free device remains stable even after repeated stretch-release cycling, maintaining 100% of its VOC after 2500 stretch-release cycles. These findings provide a strategy toward highly conductive and stretchable electrodes for harvesting mechanical energy and health monitoring.

Eco-friendly triboelectric nanogenerator based on degradable rape straw powder for monitoring human movement

Green energy from the surrounding environment has great potential for reducing environmental pollution and sustainable development. Triboelectric nanogenerators (TENGs) are of great interest as they can easily harvest mechanical energy from the environment. Here, we present a triboelectric nanogenerator (RS-TENG) based on rape straw (RS), which was developed from a film composed of waste RS and polyvinyl alcohol (PVA). Due to the high content of carbonyl, hydroxyl and amino acid functional groups in RS, the ability of RS/PVA to lose electrons is increased. The proposed RS-TENG device with a size of 6.25 cm2exhibits open circuit voltage (78 V), short circuit current (5.3μA) performance under uniform external stress at a frequency of 3.5 Hz and 10 N in the cylinder motor. 104.5μW was obtained with a load resistance of 25 MΩ. Results obtained from degradability tests revealed that the RS/PVA film was able to degrade over a period of 30 d (In PBS solution). The RS-TENG produces a significantly high current signal under conditions of finger bending, elbow movements, and foot tapping. Practical tests of the RS-TENG have shown that it is a promising sensing device that will be widely used in the future.

A Bistable Triboelectric Nanogenerator for Low-Grade Thermal Energy Harvesting and Solar Thermal Energy Conversion

Converting ubiquitous ambient low-grade thermal energy into electricity is of great significance for tackling the fossil energy shortage and environmental crisis but poses a considerable challenge. Here, a novel thermal-driven triboelectric nanogenerator (TD-TENG) is developed, which utilizes a bimetallic beam with a bi-stable dynamic feature to induce continuous mechanical oscillations, and the mechanical motion is then converted into electric power using a contact-separation TENG. The thermal process inside the device is systematically investigated and effective thermal management is conducted accordingly. After optimization, the TD-TENG can produce a power density of 323.9 mW m-2 at 59.5 °C, obtaining the highest record of TENG-based thermal energy harvesters. Besides, the first prototype of TENG-based solar thermal harvester is successfully demonstrated, with a power density of 364.4 mW m-2 . Moreover, the TD-TENG can harvest and dissipate the heat at the same time, exhibiting great potential in over-heated electronics protection as well as architectural energy conservation. Most importantly, the operation temperature range of the TD-TENG is tunable by adjusting the bimetal parameters, allowing the device a wide and flexible working thermal gradient. These unique properties validate the TD-TENG is a simple, feasible, cost-effective, and high-efficient low-grade thermal energy harvester.

Recent advances of cellular stimulation with triboelectric nanogenerators

Triboelectric nanogenerators (TENGs) are new energy collection devices that have the characteristics of high efficiency, low cost, miniaturization capability, and convenient manufacture. TENGs mainly utilize the triboelectric effect to obtain mechanical energy from organisms or the environment, and this mechanical energy is then converted into and output as electrical energy. Bioelectricity is a phenomenon that widely exists in various cellular processes, including cell proliferation, senescence, apoptosis, as well as adjacent cells' communication and coordination. Therefore, based on these features, TENGs can be applied in organisms to collect energy and output electrical stimulation to act on cells, changing their activities and thereby playing a role in regulating cellular function and interfering with cellular fate, which can further develop into new methods of health care and disease intervention. In this review, we first introduce the working principle of TENGs and their working modes, and then summarize the current research status of cellular function regulation and fate determination stimulated by TENGs, and also analyze their application prospects for changing various processes of cell activity. Finally, we discuss the opportunities and challenges of TENGs in the fields of life science and biomedical engineering, and propose a variety of possibilities for their potential development direction.

Laminating Structure for Interlayer Corona Discharge Treatment Toward Ion-Based Nanogenerators

A corona discharge treatment (CDT) is utilized to maximize the performance of triboelectric nanogenerators (TENGs) by injecting extra electrons into the negative tribomaterials. Increased performance of CDT TENGs, however, exhibits rapid degradation due to the electron dissipation by air moisture or thermal emission. To overcome such drawbacks and circumvent such dissipation, the source of charges should be replaced with ionic charges. This study reports a Ag nanowires (NWs)-embedded laminating structure (AeLS) with a unique fabrication procedure for ionic charge injection by CDT. The injection of ions is achieved by interlayer-CDT (i-CDT), in which positive charges are dissipated by Ag NWs, and the opposite negative ions can remain on the outmost surface. The AeLS TENGs with i-CDT exhibit high performance, long-term stability, and durability. It shows voltage, current, and maximum power outputs of 380 V, 15 µA, and 827 mW m^-2 , respectively. As a practical demonstration, rotational TENG integrated with a direct discharge system is realized, and its current and voltage reach 7.4 mA and 7800 V, respectively. This work can pave the way for the design of ion-based TENGs with high performance and long-lasting retention of triboelectric charges.

Cross-Link-Dependent Ionogel-Based Triboelectric Nanogenerators with Slippery and Antireflective Properties

Given the ability to convert various ambient unused mechanical energies into useful electricity, triboelectric nanogenerators (TENGs) are gaining interest since their inception. Recently, ionogel-based TENGs (I-TENGs) have attracted increasing attention because of their excellent thermal stability and adjustable ionic conductivity. However, previous studies on ionogels mainly pursued the device performance or applications under harsh conditions, whereas few have investigated the structure-property relationships of components to performance. The results indicate that the ionogel formulation-composed of a crosslinking monomer with an ionic liquid-affects the conductivity of the ionogel by modulating the cross-link density. In addition, the ratio of cross-linker to ionic liquid is important to ensure the formation of efficient charge channels, yet increasing ionic liquid content delivers diminishing returns. The ionogels are then used in I-TENGs to harvest water droplet energy and the performance is correlated to the ionogels structure-property relationships. Improvement of the energy harvesting is further explored by the introduction of surface polymer brushes on I-TENGs via a facile and universal method, which enhances droplet sliding by means of ideal surface contact angle hysteresis and improves its anti-reflective properties by employing the I-TENG as a surface covering for solar cells.

Recent Advances in Mechanical Vibration Energy Harvesters Based on Triboelectric Nanogenerators

With the development of autonomous/smart technologies and the Internet of Things (IoT), tremendous wireless sensor nodes (WSNs) are of great importance to realize intelligent mechanical engineering, which is significant in the industrial and social fields. However, current power supply methods, cable and battery for instance, face challenges such as layout difficulties, high cost, short life, and environmental pollution. Meanwhile, vibration is ubiquitous in machinery, vehicles, structures, etc., but has been regarded as an unwanted by-product and wasted in most cases. Therefore, it is crucial to harvest mechanical vibration energy to achieve in situ power supply for these WSNs. As a recent energy conversion technology, triboelectric nanogenerator (TENG) is particularly good at harvesting such broadband, weak, and irregular mechanical energy, which provides a feasible scheme for the power supply of WSNs. In this review, recent achievements of mechanical vibration energy harvesting (VEH) related to mechanical engineering based on TENG are systematically reviewed from the perspective of contact-separation (C-S) and freestanding modes. Finally, existing challenges and forthcoming development orientation of the VEH based on TENG are discussed in depth, which will be conducive to the future development of intelligent mechanical engineering in the era of IoT.

From Biochemical Sensor to Wearable Device: The Key Role of the Conductive Polymer in the Triboelectric Nanogenerator

Triboelectric nanogenerators (TENGs) have revolutionized energy harvesting and active sensing, holding tremendous potential in personalized healthcare, sustainable diagnoses, and green energy applications. In these scenarios, conductive polymers play a vital role in enhancing the performance of both TENG and TENG-based biosensors, enabling the development of flexible, wearable, and highly sensitive diagnostic devices. This review summarizes the impact of conductive polymers on TENG-based sensors, focusing on their contributions to triboelectric properties, sensitivity, detection limits, and wearability. We discuss various strategies for incorporating conductive polymers into TENG-based biosensors, promoting the creation of innovative and customizable devices tailored for specific healthcare applications. Additionally, we consider the potential of integrating TENG-based sensors with energy storage devices, signal conditioning circuits, and wireless communication modules, ultimately leading to the development of advanced, self-powered diagnostic systems. Finally, we outline the challenges and future directions in developing TENGs that integrate conducting polymers for personalized healthcare, emphasizing the need to improve biocompatibility, stability, and device integration for practical applications.

Ultrasound-Driven Injectable and Fully Biodegradable Triboelectric Nanogenerators

Implantable medical devices (IMDs) provide practical approaches to monitor physiological parameters, diagnose diseases, and aid treatment. However, device installation, maintenance, and long-term implantation increase the risk of infection with conventional IMDs. Therefore, medical devices with biocompatibility, controllability, and miniaturization are highly demandable. An ultrasound-driven, biodegradable, and injectable triboelectric nanogenerator (I-TENG) is demonstrated to reduce the risks of implant-related injuries and infections. The injection can be given by subcutaneous injection with a needle to minimize the implantation incision. The stable output of I-TENG is driven by ultrasound (20 kHz, 1 W cm^-2 ), with a voltage of 356.8 mV and current of 1.02 µA during in vivo studies and an electric field of about 0.92 V mm^-1 during ex vivo experiments. The cell scratch and proliferation assays showed that the delivered electric field effectively increased cell migration and proliferation, indicating a significant potential to accelerate healing with electricity.