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

In the environment, there is an abundance of gust energy which is challenging to harvest with conventional rotating wind turbines, such as the gusts generated by passing vehicles along roadsides. Addressing the irregular and low‐frequency characteristics of gusts, a bladeless wind turbine triboelectric nanogenerator (BWT‐TENG) with enhanced aerodynamic performance is proposed, enabling effective harvesting of random gust energy. First, a bladeless wind turbine with a cylindrical bluff body shape is designed, and its aerodynamic principles under gust‐driven conditions are elucidated through the computational fluid dynamics method. Subsequently, parameter optimization is conducted for the multilayered TENG. Systematic experiments demonstrated that the BWT‐TENG achieved a peak power density of 4.08 W m−3 driven by a gust of 10 m s−1, and can even operate at frequencies as low as 0.1 Hz. Finally, experiments showcased the BWT‐TENG powering a warning light in a simulated rainfall environment and harvesting gust energy from vehicles passing by real roadside to power wireless gyroscopic sensors, thereby achieving self‐powered structural health monitoring of roads or bridges. This work provides a novel strategy for utilizing TENGs in the harvest of environmental gust energy and demonstrates the vast potential of TENGs in the field of self‐powered structural health monitoring. [ABSTRACT FROM AUTHOR]

Hydrokinetic energy, a vital renewable resource, holds promise for addressing fossil fuel shortages to ensure a sustainable future. This study proposes an efficient and stable ocean wave energy harvesting system that combines a triboelectric nanogenerator (TENG), an electromagnetic generator (EMG) with a planetary gear system, and a driving turbine. The turbine transforms the up‐and‐down motion in water into continuous, unidirectional rotational motion. An EMG device accelerated by a planetary gear system further ensures sustained output at very low frequencies (0.25 Hz) and boosts the upper limit of power generation at medium to high frequencies. Under water wave conditions with a 1 Hz frequency, the TENG component yields an output of up to 2200 V and 122 µA, while the average EMG output is 15 V and 80 mA. Remarkably, the entire system maintains a steady and uninterrupted output even at extremely low frequencies (0.25 Hz). The peak power outputs for the TENG and EMG components are 115 and 350 mW, respectively, with power densities of 32.55 and 329.78 W m−3, surpassing prior achievements. This research demonstrates self‐powered applications and provides an efficient method to amplify water wave forces, enhancing energy harvesting capabilities for practical marine environmental monitoring. [ABSTRACT FROM AUTHOR]

Driver's driving behavior and driving style have a crucial impact on traffic safety, capacity, and efficiency, so it is of great significance to monitor the driver's driving behavior and recognize their driving style. In this work, an intelligent driving monitoring system based on a triboelectric nanogenerator and electromagnetic generator is designed. The system consists of a self‐powered pedal motion sensor (SPMS) and an intelligent data processing unit (IDPU), which can monitor driving behavior and recognize driving style. SPMS is used for driving behavior monitoring, which mainly consists of a six‐phase triboelectric nanogenerator (S‐TENG) and a free‐rotating disk electromagnetic generator (FD‐EMG). S‐TENG can recognize information such as pedal movement direction, movement amplitude, and movement speed, and FD‐EMG can realize the function of a self‐powered driver's driving behavior warning. The IDPU includes a numerical calculation system for driving style characteristic variables and a driving style classifier. It can recognize the driving style based on the driving data collected by SPMS. The driving style classifier design is based on a combination of simulated driving experiments and machine learning techniques, and its accuracy is verified through experiments. This work has important potential applications in the field of traffic safety and intelligent driving. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerator (TENG) is one promising method of wave energy harvesting for marine ranching monitoring. Different from previous studies with complex structures (gears, racks, worm gears, or screw‐nut), a bow‐drill structured TENG (BS‐TENG) with a simple, cheap but effective rope‐roller structure is proposed and investigated to magnify the wave motion frequency. Inspired by the bow‐drill for carpentry, the proposed structure only simply needs a rope and roller to transfer the random wave motion into regular rotary motion with higher frequency. Results show that the structure parameters (flexible paddle number NP flexible paddle length L, electrode number NE and shaft side length D) have a great influence on the working performance of the BS‐TENG. The maximum frequency magnification ration (Rm) is 74 under the condition of 130 mm wave height (Hw); the maximum output power (P) is 450 µW. Demonstration experiments verify that the BS‐TENG is able to charge the thermo‐hygrometer and light emitting diode lights for marine ranching. Combined with the Internet of Things and 5G technologies, the BS‐TENG could be applied in the offshore sensor system for the monitoring of marine ranching information. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicle (UAV) is widely used in various industries due to their high flexibility and large maneuverable space. Abnormal vibration of UAV motors can prevent it from working properly due to the abnormal state of the motors and the harsh external environment. There is no suitable method to monitor the UAV motors vibration in real time. At the same time, commercial sensors require an additional power supply to power the sensor, which indirectly limited their application in UAVs. A vibration sensor (AV-TENG) with magnetic spring structure was proposed in this paper for monitoring the vibration of UAV motors. The experimental results show that the magnetic spring has excellent stability. AV-TENG can achieve frequency detection in a wide frequency band. It also has excellent linearity with a maximum error of only 0.0062 %. Simultaneously, to verify the performance of AV-TENG in various environments and simulate its loading, the results demonstrate that AV-TENG can adapt well to the working conditions of UAV. Finally, this paper constructs a low-cost (less than $7), easy-to-manufacture signal acquisition system, and conducts a field demonstration, realizing the monitoring of the vibration frequency and acceleration of the UAV motors, and realizing the early warning, which is expected to promote the development of the field of UAV as well as the practical application of the triboelectric nanogenerator. [Display omitted] • Based on TENG, the vibration sensor designed in this paper was used to monitor the vibration of the motor part of the UAV. • A novel magnetic spring structure is designed, which has the advantages of high reliability and high stability. • A low-cost, high-accuracy acquisition system for TENG is designed. UAV-carrying experiments were conducted in practice. [ABSTRACT FROM AUTHOR]

Currently, unmanned aerial vehicles (UAVs) play a pivotal role in meteorological wind speed measurements. Nevertheless, existing anemometers exhibit notable issues, including excessive weight, high cost and high cut-in wind speed. This investigation introduces a biomimetic owl wing airfoil wind speed sensor utilizing the principles of the triboelectric nanogenerator (BOW-TENG) designed for UAV applications. Inspired by owl wings, an airfoil configuration with superior aerodynamic characteristics is ascertained, subsequently fabricating it into an impeller, and a wind speed sensor with low weight, low cost and low cut-in wind speed is developed. Experimental results affirm the BOW-TENG's precision in depicting wind speed across the range of 1.6–10.7 m/s, featuring a sensitivity of 21.893 Hz/(m·s−1), a goodness of fit R2 of 0.9995, and a remarkable resolution of 0.057 m/s. The sensor weighs only 30 g. Furthermore, a cost-effective triboelectric signal processing system is devised for integrating the BOW-TENG into the UAV, as well as the optimal positioning for BOW-TENG on the UAV is identified through simulations. The relative wind direction can be calculated from signals of the BOW-TENGs on the four arms of the UAV. Ultimately, application experiments demonstrate the feasibility of employing BOW-TENG for wireless wind speed transmission from UAVs. This work incorporates bionics and proposes a practical application of triboelectric sensors for UAVs, as well as a solution for developing wind speed sensors in the field of meteorological UAV detection. [Display omitted] • BOW-TENG is used for wind speed measurements of meteorological UAVs. • The structural is combined with bionics to give the sensor a lower cut-in wind speed. • An excellent signal processing wireless transmission system is designed for UAV applications. [ABSTRACT FROM AUTHOR]

Developing high-performance triboelectric nanogenerators (HP-TENGs) is paramount for expanding their commercial utility. Presently, HP-TENGs predominantly concentrate on augmenting surface charge density. Here, we introduce an innovative strategy, denoted ACT-TENG (Accelerated Charge Transfer TENG), which markedly enhances TENG's performance by effectively accelerating charge transfer between materials, all while preserving the original charge density. We substantiate the feasibility of this approach through systematic investigations, employing magnetic field modulation and bidirectional rotation mode to verify the gain effect of ACT-TENG. Notably, compared to conventional free-standing TENG (FS-TENG), ACT-TENG achieves a 4-fold increase in charge transfer rate and a remarkable 14.6-fold enhancement in output power. This leads to an impressive average power density of 499.05 mW m-² Hz-¹ , showcasing superior performance compared to previously reported FS-TENG designs. Furthermore, ACT-TENG exhibits exceptional characteristics when deployed in a water flow environment, generating the power of 10.76 mW at a flow rate of 180 L min−1. Finally, we utilize ACT-TENG to harvest energy from water flow, constructing a self-powered Internet of Things (IoT) system within the underground pipeline gallery. This study addresses existing limitations in TENG technology and offers valuable insights into further advancements in enhancing TENG's performance. [Display omitted] • A generalized strategy (ACT-TENG) is proposed to improve the performance of TENG by accelerating the charge transfer. • The power of ACT-TENG is 14.6 times higher than free-standing TENG, and an excellent average power density is achieved. • An IoT self-powered system for the underground smart pipeline gallery is developed by harvesting water flow energy. [ABSTRACT FROM AUTHOR]

To enhance the adaptability and usability of the triboelectric nanogenerator (TENG) in wave environments, a current-enhanced TENG with crossed rollers (CE-TENG) is proposed in this work for harvesting wave energy. This study successfully addresses the issue of charge neutralization in roller-type TENGs with an innovative design of cross-roller electrodes, significantly enhancing wave energy harvesting ability. Based on this novel design, the CE-TENG exhibits excellent performance in various conditions and applications, showing its practical usability in real-world scenarios. The results indicate that the CE-TENG, compared with traditional designs, boosts the mean output current by 2.53 times and enhances energy harvesting ability by 10.27 times. The CE-TENG achieves a mean power of 274.48 µW and peak output power of 2.27 mW, successfully enabling data transmission for wireless sensors and powering warning radar monitoring. The cross-roller electrodes in CE-TENG realize the efficient utilization of space and performance enhancement of roller-type TENGs. This study expands the high-performance electrode design possibilities of TENGs for harvesting wave energy, improving their service capabilities in wave energy environments and offering a power supply solution for low-power marine equipment. [Display omitted] • A current-enhanced triboelectric nanogenerator with crossed rollers (CE-TENG) for harvesting wave energy is proposed. • The crossed roller is adopted to realize the current and energy of CE-TENG is also increased by more than 2.5 and 10 times. • The CE-TENG can be used to supply energy for the wireless sensor or radar module to realize the early warning. [ABSTRACT FROM AUTHOR]

Abstract Water wave energy is regarded as one of the most prospective renewable energy sources, while most of it has not been utilized for numerous technology defects. As a new energy technology, triboelectric nanogenerator (TENG) has been widely utilized for low frequency and random mechanical energy harvesting, which is very suitable for scavenging water wave energy. In this paper, we present a torus structured triboelectric nanogenerator (TS-TENG) which consists of an inner ball and a torus shell. Triggered by water waves, the ball revolves in the torus shell for triboelectric power generation, and the TS-TENG can harvest random wave energy from all directions. Moreover, to scavenge large-scale water wave energy, the TS-TENG array is fabricated and presented as a power source for persistently powering electronic devices and charging a battery or capacitor. With an agitation frequency of 2 Hz and an oscillation angle of 5°, the TS-TENG is expected to give a maximum peak power density of 0.21 W/m2. Take advantage of low-cost, environment-friendly and easy- implement, the development of the TS-TENG is of great significance for harvesting large-scale ocean wave energy and other potential applications in blue energy. Graphical abstract Triggered by water waves, the inner ball revolves in the torus shell for triboelectric power generation, and the TS-TENG can harvest random wave energy from all directions. Moreover, to scavenge large-scale water wave energy, the TS-TENG array is fabricated and presented as a power source for persistently powering electronic devices and charging a battery or capacitor. fx1 Highlights • A torus structured triboelectric nanogenerator (TS-TENG) which encloses an inner ball inside a torus shell is investigated. • Triggered by water waves, the ball revolves in the torus shell for triboelectric power generation, and the TS-TENG can harvest random wave energy from all directions. • The TS-TENG array is fabricated and demonstrated as a power source for continuously driving electronic devices and charging an energy storage unit. • With an agitations frequency of 2 Hz and an oscillation angle of 5°, the TS-TENG is expected to give a maximum peak power density of 0.21 W/m2. [ABSTRACT FROM AUTHOR]

Downhole motors are essential in providing rotational power to the drill bit and achieving the desired trajectory of the wellbore, making them the most reliable component of the bottom-hole assembly. Monitoring their speed and direction is critical to improving drilling efficiency. In this paper, we propose the use of a triangular electrode triboelectric nanogenerator (T-TENG) for monitoring downhole motor speed and direction. The T-TENG employs triangular copper foils as the electrode layer and can determine the direction of rotation based on the transient characteristics of the output signal. Experimental results show that the T-TENG exhibits a measurement error of less than 3 % for speeds within the monitoring range of 0–1200 rpm, and demonstrates good linearity. To enable real-time detection of the downhole motor's instantaneous speed, we introduce an instantaneous speed algorithm based on MATLAB. The average speed curve is obtained by fitting the instantaneous speed using variational mode decomposition (VMD) analysis. Furthermore, the T-TENG exhibits impressive power generation performance and can simultaneously power a low-power temperature and humidity sensor and 436 series-connected light-emitting diodes (LEDs). Compared to conventional downhole sensors, the T-TENG obviates the requirement for an external power source and enables simultaneous measurement of speed and direction. Hence, it offers a fresh perspective for the advancement of next-generation downhole sensors. [Display omitted] • This study proposes a novel monitoring approach for downhole motors using the T-TENG. • For real-time monitoring of downhole motor speed, an instant speed calculation algorithm is developed. • Using output signal transients, accurate rotation direction determination is achieved. [ABSTRACT FROM AUTHOR]

Automobile flow sensors are critical in ensuring the engine air-fuel ratio, improving fuel efficiency, and reducing pollution. This paper presents a self-powered shaftless turbine intake flow sensor (STIFS) for automobiles consisting of a ball-bearing triboelectric nanogenerator (BB-TENG) and a magnetic field modulation type magnetic gear electromagnetic generator (MG-EMG). The contact electrification between the rolling ball and the outer ring of the BB-TENG generates a periodic electrical signal for flow sensing. In particular, the magnetic gear can improve the BB-TENG signal frequency and MG-EMG output performance. The smoothness of the airflow is improved by designing the shaftless turbine using the computational fluid dynamics (CFD) method, and the start flow of the STIFS is 160 L/min. The sensing sensitivity of the STIFS reaches 0.71 Hz/L·min−1·in the monitoring range of 300–900 L/min, and there is a well linear relationship between frequency and flow rate. In addition, the MG-EMG can generate output voltages and currents of 374 V and 31 mA to power data analysis and transmission modules in real-time. This work presents a novel methodology for self-powered wireless airflow sensing in large-flow pipelines, such as automobile intake pipes. [Display omitted] • The shaftless turbine reduces the obstruction of the turbine blades to the airflow making the airflow smoother. • Magnetic field modulation type magnetic gear can improve the BB-TENG signal frequency and MG-EMG power generation. • Self-powered intelligent wireless system designed for real-time air flow monitoring. [ABSTRACT FROM AUTHOR]

At present, it is significant for unmanned aerial vehicle (UAV) to sense the external information in the interference environment. Therefore, an arc-shaped flutter-driven wind speed sensor based on triboelectric nanogenerator (AW-TENG) for UAV is proposed in this work. The arc structure of AW-TENG, which adopts contact separation mode through air vibration, is designed according to the working principle and simulation. Then the three influencing factors of plate spacing, radian and radian direction are carried out to determine its optimal structure. The performance of the optimal structure is verified: the voltage frequency that AW-TENG can reach in the wind speed range of 6–20 m/s is 50–200 Hz, the sensitivity is 9.88 Hz/(m s−1) and the goodness of fit R2 = 0.998. Meanwhile, the voltage range that AW-TENG can reach is about 30–55 V, the generated current range is about 8–28 μA. Finally, the application experiment of the wireless wind speed transmission of the UAV with AW-TENG is carried out. The experiment proves that TENG has the ability to apply the wind speed sensor for UAV, and provides experimental support for the wind speed monitoring of the overall structural unit of UAV in the future. [Display omitted] • This work converts the frequency signal of voltage into wind speed value to realize the sensing function of AW-TENG. • AW-TENG solved the problem of wind speed sensor through a designed arc structure oriented to the application of UAV. • Methods of wireless transmission of triboelectric nanogenerators and their fields of application have been expanded. [ABSTRACT FROM AUTHOR]

The renewable mechanical energy is pervasive but mainly contained in diverse, low-frequency and irregular motions, making its efficient exploitation highly difficult. Here, a multi-purpose triboelectric-electromagnetic hybrid nanogenerator (M-TEHG) is developed to tackle this issue through an ingenious mechanical motion-controlled switch (MMS). Consisting of a sprung-pendulum, a stiffness-adaptive plectrum and a slideable rotor, the MMS can not only transform low-frequency motions to one-way and high-speed spin but also enable the M-TEHG to automatically switch between non-contact state and contact state under the action of the rotor gravity. The M-TEHG exhibits frequency-multiplied outputs, improved durability, and superior adaptability to various motions. When triggered by low-frequency (≤ 5 Hz) swings and vibrations, the watch-sized M-TEHG can provide milliwatt-level electric power. When the M-TEHG is exposed to irregular water waves of around 1 Hz, the output power can reach roughly 0.7 mW. By harvesting human arm motions and water waves, the M-TEHG can power an electronic watch, drive a hygrometer, and light up 120 LEDs. This work provides a prospective strategy for tapping diverse low-frequency irregular motions as a green power source for wearable electronics and environment sensing systems. [Display omitted] • A multi-purpose triboelectric-electromagnetic hybrid nanogenerator (M-TEHG) is proposed for tapping low-frequency motions. • The M-TEHG can convert various low-frequency and irregular motions to high-speed rotation. • The M-TEHG can automatically switch working mode to achieve high durability. [ABSTRACT FROM AUTHOR]

The traditional tipping-bucket rain gauge (TBR) has the problems of low measurement accuracy and severe abrasion under heavy rainfall conditions, and cannot realize the real-time rainfall monitoring and rain energy harvesting. In this work, a TBR based on manifold triboelectric nanogenerator (TENG) units is proposed to solve the above problems. The significant parameters affecting the electrical output performances of freestanding TENG (F-TENG) and contact-separation mode TENG (CS-TENG) units are comprehensively explored and then optimized from the theoretical and experimental perspectives. Based on the optimized structure of TENG units, a series of experiments for sensing and power generation performances and demonstrations of the TENGs-based TBR are carried out. The experimental results indicate that the proposed TBR can detect the real-time and average rainfall intensities ranging from 0 to 288 mm/d with a minimum rainfall amount resolution of 5.5 µm. Besides, the frequency of the output electrical signal varies linearly with the rainfall intensity but invariant as the humidity changes. More importantly, the rain gauge can obtain the peak output power of 7.63 mW by the CS-TENG unit with a multilayered structure at 250 mm/d. Therefore, the proposed TENGs-based TBR as a rainfall sensor has real-time measurement ability, high resolution, excellent anti-humidity interference ability, as well as rainwater energy harvesting function. The presented multi-functional TBR has great potential to achieve monitoring and data delivery of rainfall information in extreme environments, contributing to the further development of self-powered wireless sensor networks of rainfall information. [Display omitted] A novel tipping-bucket rain gauge (TBR) integrated with triboelectric nanogenerators (TENGs) is proposed, which can realize real-time rainfall sensing by a freestanding TENG (F-TENG) and rainwater energy harvesting by a contact-separation mode TENG (CS-TENG). Moreover, it has excellent anti-humidity interference ability and high resolution using a novel approach of sensing index with output frequency of the F-TENG. This work has great potential to achieve monitoring and data delivery of rainfall information in extreme environments, contributing to the further development of self-powered wireless sensor networks of rainfall information. • A TENGs-based TBR for real-time rainfall sensing and energy harvesting is proposed. • Sensing index with frequency of a F-TENG realizes anti-humidity interference ability. • The raindrops are collected by TBR for a CS-TENG to capture more electrical energy. [ABSTRACT FROM AUTHOR]

In vehicle electronic systems, acceleration sensors play an irreplaceable role in improving vehicle performances. The on-board acceleration sensor is suitable for common operating conditions, not only requires an external power supply and charge amplifier, but also has the defect of high noise. In this work, a magnetic-assisted self-powered acceleration sensor (MSAS) based on the triboelectric nanogenerator is proposed to monitor the low acceleration under common operations and the high acceleration under the collision conditions of vehicles. MSAS adopts magnetic repulsion adjustment system, which has good stability and high signal-to-noise ratio of output signal within its detection range. Simultaneous monitoring of the value and direction of the acceleration can be achieved by analyzing the frequency and trend of the electrical signals. The linear motor and pendulum impact experiment bench were established, and the results depicted that the fitting linear coefficients of the MSAS under low and high acceleration reached 0.993 and 0.991, respectively. In the durability experiment of continuous operation for 6 h, even if the amplitude of the MSAS electrical signal changes slightly, the frequency remains unchanged. Finally, the application of MSAS in real-time monitoring of remote-control car operation and collision acceleration is verified, as well as the comparison with a commercial acceleration sensor. It further illustrates the potential utility of MSAS in vehicle electronic systems. [Display omitted] • A magnetic-assisted self-powered acceleration sensor (MSAS) for monitoring vehicle operation and collision is proposed. • The MSAS uses a magnetic repulsion adjustment system to increase its linear bandwidth and stability. • Simultaneous monitoring of acceleration value and orientation through electrodes arrangement and signal processing. [ABSTRACT FROM AUTHOR]

In the field of energy harvesting and self-powered sensing, the universal equivalent circuit model of triboelectric nanogenerators (TENGs) is an important development tool for research and applications. Such a universal model of the current source is established to first order for the basic operating modes of a TENG, which provide the related theoretical models and electrical models used in simulation. The universal first-order equivalent circuit model demonstrates that the carrying capacity of a TENG separates into three regions of distinct output characteristics, namely, constant current, maximum power, and constant voltage. Moreover, employing electrometers, an electrometer and multimeters, and TENGs in series and parallel in successive experiments, we verify that the TENG can be considered a current source with a resistance of mega-ohms and a capacitance of nano-farads. Overall, our first-order model sets electrical standards for the internal circuit of the TENG and therefore provides theoretical guidance that lays the foundation for applications in high-performance supply and grid-connected power generation. [Display omitted] • The first-order equivalent circuit model (FO-ECM) of the current source is established for TENG. • The universal FO-ECM presents three different output characteristic regions both in theory and experiment. • The FO-ECM is verified by employing electrometers, an electrometer and multimeters, and TENGs in series and parallel. [ABSTRACT FROM AUTHOR]

In the development of smart cities, accurate liquid flow monitoring is essential for the efficient operation of water supply systems. Current flow sensors often face limitations in sensitivity and environmental adaptability, affecting measurement accuracy, and restricting their application in smart city infrastructure. To address these challenges, this study proposes a high‐accuracy flow monitoring method. Specifically, by combining the bionic design with advanced signal processing techniques, the sensitivity and anti‐interference ability are improved, respectively, to enhance the measurement accuracy. Based on this method, a self‐powered flow sensor (SPFS) is developed using noncontact triboelectric nanogenerators (NC‐TENGs) as the sensing unit. The SPFS achieves a sensitivity of 2.07 Hz L−1 min−1 and improves the signal‐to‐noise ratio by more than 13 times over the initial sensing signal. In addition, an intelligent system is developed to accurately measure water resources. The maximum flow rate error rate is less than 0.97% compared to commercial flow sensors. The SPFS demonstrates higher sensitivity and accuracy compared to the existing TENG flow sensors. This study addresses the limitations of existing flow sensors and pioneers a novel solution for enhanced water resource management in smart cities. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerator (TENG), as a new technique for energy capture, has unique advantages in harvesting high‐entropy energy. In view of the wind‐induced vibration characteristics of power transmission lines, the symmetric elastic bistable triboelectric nanogenerator (EB‐TENG) is introduced in this work. The core component of the EB‐TENG is the elastic bistable cantilever beam structure, which is designed by introducing an elastic perturbation structure to the conventional cantilever beam. This beam results in several sub‐resonance frequencies in addition to the natural frequencies, which broadens the frequency band of the EB‐TENG. In addition, the EB‐TENG adopts a symmetrical cantilever beam to ensure effective harvesting of vibration energy, even in situations of self‐tilting and external tilting vibration. The experimental outcomes confirm that the EB‐TENG can significantly harvest vibration energy in the 7–60 Hz frequency range and delivers the maximum peak power of 2.846 mW, which meets the major vibration frequency range of power transmission lines under the action of breeze. Finally, self‐powered strategy based on EB‐TENG online monitoring devices (such as tower obstruction lights, temperature and humidity sensors, and line high temperature wireless alarms) is constructed. This work helps promote the application of in‐situ self‐powered monitoring based on TENG in smart transmission lines. [ABSTRACT FROM AUTHOR]

Dynamic loads are inevitably generated during the operation of rotating machinery. In situ monitoring the dynamic loads is of great significance for assessing shafting health. Triboelectric nanogenerator (TENG) is sensitive to motion but not suitable for load monitoring, while piezoelectric nanogenerator (PENG) is just the opposite. Therefore, the combination of the two can complement each other. From this, a dynamic load monitoring smart bearing (DLMSB) integrated with TENG and PENG is proposed. The specially designed TENG can produce an “M‐waveform”, which can be used to extract rotation frequency and distinguish the quadrant of the rotor. Meanwhile, applying PENG to capture the load condition of the bearing, and referring to the main frequency of M‐waveform, it is convenient to obtain the dynamic loads of shafting. Furthermore, a real‐time monitoring system is developed, which can realize not only real‐time monitoring of the rotation speed and dynamic loads magnitude but also the quadrant discriminating of dynamic loads. The results have shown that the monitoring error for dynamic loads is 3 N or 5.5%, and the accuracy rate for determining the quadrant of the dynamic loads can reach 93%. This study provides a novel approach for the in situ monitoring of mechanical operating status via nanogenerators. [ABSTRACT FROM AUTHOR]

From the extensive research on wind energy harvesting, the triboelectric nanogenerator (TENG) has proven to be effective in converting mechanical energy into electric energy. To supply continuous and regular electric energy above the critical speed, we developed a magnetic switch structured triboelectric nanogenerator (MS-TENG) consisting of transmission gears, energy modulation modules, and a generation unit. When wind falls intermittently on the wind scoop, the energy stored and released by the energy modulation modules at any time does not depend on wind speed but on the magnetic force of the magnets, enabling the wind energy to be converted into continuous and regular electric energy. The experimental results demonstrate that the MS-TENG can operate as a power supply, producing output characteristics of 410 V, 18 μA, 155 nC, and a peak power of 4.82 mW, sufficient to power 500 LEDs in series or a thermometer. Its prospects in the field of wind energy harvesting appear excellent. [Display omitted] • Magnetic switch structured triboelectric nanogenerator for continuous and regular harvesting of wind energy. • When the input speed exceeds the critical speed, the MS-TENG outputs a continuous and regular supply of electric energy. • The MS-TENG powered 500 LEDs in series and a thermometer, proving its excellent application prospects. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerator (TENG), as a renewable energy harvesting technology, has been verified as an effective approach for converting mechanical energy into electric energy. In a natural environment, the unsteadiness of TENG energy harvesting restricts the application and development of TENG. From this perspective, a gravity triboelectric nanogenerator (G-TENG) is developed for the first time to convert natural wind energy into steady electric energy, achieving the steady harvesting of natural wind energy. The G-TENG mainly comprises an energy input module, energy storage module, and energy output module. Random wind energy is transmitted from the input module to the storage module and converted into gravitational potential energy. Steady electric energy is ultimately obtained from the output module. The standard deviation (I SD) of the short-circuit current peaks is under 0.31 μA. Additionally, the fluctuation degree (I FD) of the short-circuit current peaks is defined to describe the steady output capability of TENG. I FD of the G-TENG can reach 2.3%. A steady current is thus achieved by the G-TENG in a natural environment. This research provides essential guidance for the steady harvesting of natural energy by the TENG. [Display omitted] • Gravity triboelectric nanogenerator (G-TENG) is proposed for the steady harvesting of natural wind energy. • The fluctuation degree (I FD) of short-circuit current peaks is defined to describe the steady output capability of TENG. • A commercial thermometer is powered by the G-TENG with the assistance of a bridge rectifier in a natural wind environment. [ABSTRACT FROM AUTHOR]

Sensor networks are essential for the development of the Internet of Things and the smart city. A general sensor, especially a mobile sensor, has to be driven by a power unit. When considering the high mobility, wide distribution and wireless operation of the sensors, their sustainable operation remains a critical challenge owing to the limited lifetime of an energy storage unit. In 2006, Wang proposed the concept of self-powered sensors/system, which harvests ambient energy to continuously drive a sensor without the use of an external power source. Based on the piezoelectric nanogenerator (PENG) and triboelectric nanogenerator (TENG), extensive studies have focused on self-powered sensors. TENG and PENG, as effective mechanical-to-electricity energy conversion technologies, have been used not only as power sources but also as active sensing devices in many application fields, including physical sensors, wearable devices, biomedical and health care, human–machine interface, chemical and environmental monitoring, smart traffic, smart cities, robotics, and fiber and fabric sensors. In this review, we systematically summarize the progress made by TENG and PENG in those application fields. A perspective will be given about the future of self-powered sensors. [ABSTRACT FROM AUTHOR]

A driver training assistance system (DTAS) is proposed for driver training and behavior monitoring. The DTAS utilizes three driving operation sensors that based on the principle of triboelectric nanogenerators. The gear position sensor can monitor the gear that the driver has switched, the steering angle sensor captures the direction and angle of the driver's rotation of the steering wheel, and the pedal sensor can monitor which pedal the driver is pressing or releasing. In addition, the DTAS can monitor driver behavior and provide feedback on each driver's operation process in real-time. Combined with deep learning (DL) technology, the DTAS can identify and evaluate the results of the driving operation of drivers in specific training scenarios, with an accuracy rate of 97.5%. This work can provide new ideas for the innovative exploration of new driving training modes without coaching and effectively promote the application of triboelectric nanogenerators in the field of intelligent transportation. [Display omitted] • Proposed a driving operation monitoring method that integrates three triboelectric sensors. • The deep learning technology is explored to analyse the driver training electrical signal data. • The developed driving training assistance system can be used to monitor driving behavior and evaluate training results. Improving the driving skills of drivers, particularly during the training stage, is crucial in reducing the likelihood of road traffic accidents. In this work, a driver training assistance system (DTAS) is developed for driver training and behavior monitoring. The DTAS integrates three triboelectric driving operation sensors, including gear shift sensor, steering angle sensor, and pedal sensors. Through the ingenious structural design of contact-separation and freestanding-triboelectric-layer mode, these triboelectric sensors have the characteristics of simple structure, easy manufacture and installation, and self-powered, which avoids the complex wiring problem in the limited space of the vehicle. The basic electrical performance test of triboelectric sensors and driving simulation experiment show that the developed DTAS can monitor the driver behavior and provide the feedback on each driver's operation process in real-time. Combined with deep learning (DL) technology, the DTAS can identify whether the driving operation of drivers in specific training scenarios is correct or not, with an accuracy rate of 97.5%. This work is aimed at assisting the novice or learner drivers in driving training, which helps to improve their driving skills and form good driving habits. The proposed scheme can provide new ideas for the innovative exploration of driving training modes without coaching. [ABSTRACT FROM AUTHOR]

[Display omitted] Selecting suitable triboelectric materials for triboelectric nanogenerators (TENGs) with excellent integrated performance at ambient environment remains a challenge. Here, we propose a set of universal material's selection rules for TENGs with comprehensive material's properties, including surface charge density in low and high relative humidity, moisture resistance rate, and friction coefficient. The influence mechanisms of environmental factors on the output performance of TENG are first revealed. Based on the selection rules, comprehensive selection series are ranked for all types of TENGs with fifteen triboelectric material pairs (cumulative sixty sets of samples). Additionally, two TENG integrated devices are also presented to confirm the generality and feasibility of the selection rules. The moisture resistance rate reaches up to 124% after working in ambient conditions with 95% relative humidity for 36, 000 s. This work provides a significant guideline for triboelectric material's selection and promotes the practical applications of TENG. [ABSTRACT FROM AUTHOR]

[Display omitted] • A gas-assisted method is proposed for improving the output performance of TENG. • The charge transfer ability of GA-TENG is improved by 13.86 times via the method. • GA-TENG can provide power to wireless sensors and water level detection modules. Triboelectric nanogenerators (TENGs) have unparalleled performance advantages in the low-frequency range and become an emerging technology for efficient wave energy harvesting. There are various methods to improve the output performance of triboelectric nanogenerators, but the output effect and manufacturing convenience of the TENGs cannot be balanced, which limits their promotion and application in a wider field. Here, a gas-assisted triboelectric nanogenerator (GA-TENG) for harvesting wave energy is reported, which has high performance through a gas-assisted method. The gas-assisted device is mainly composed of two airbags and a flexible substrate to increase the actual contact area between the triboelectric layers, which increases the open-circuit voltage (V oc) and transferred charge (Q sc) by 7.99 and 13.86 times, respectively, compared to the rigid substrate. The power density of GA-TENG can reach 20.4 W/m3 under the wave frequency of 1 Hz. In addition, the applications of GA-TENG are successfully demonstrated, including powering three lamps of 3 W, a wireless temperature and humidity sensor, and a water level monitoring module. This work provides a design scheme for wave energy harvesting and a universal method for TENG to harvest renewable energy efficiently. [ABSTRACT FROM AUTHOR]

• An EC-TENG is proposed to achieve a unified conversion of wind and water energy. • Using coupling strategy to unite savonius and pelton turbine with the charge pump. • Coupled power is 442.1% higher than the sum of powers of the main and pump units. • EC-TENG can power wireless sensors at wind and water speeds of 3.5 and 1.3 m/s. As a promising technology, triboelectric nanogenerators (TENGs) can efficiently capture low-frequency energy to power distributed sensors. Wind and water are renewable energy sources that commonly co-exist in the environment, and their simultaneous harvesting has been a hot research topic for TENGs. However, existing researches are essentially the superposition of electrical energy converted from the single energy source, which lack the consideration of the unified conversion of the two energies. Here, we propose an energy-coupled triboelectric nanogenerator (EC-TENG) based on charge pump, which employs a savonius turbine and pelton wheel in conjunction with a system consisting of the main and pump unit to realize the coupling and unified conversion of wind and water energy. The effects on performance of EC-TENG are analyzed theoretically and experimentally. Compared with the sum of the outputs of the main and pump units, the peak power after coupling of the two units is significantly increased by 442.1%. EC-TENG can reach output performances of 7.5 mW and 412.2 mW/m2, and can stably supply power for the wireless temperature and humidity sensor at wind and water speeds of 3.5 m/s and 1.3 m/s, respectively. This work provides a reference for the research of TENGs with multi-energy collection. [ABSTRACT FROM AUTHOR]

[Display omitted] • Morphological transformation strategy is proposed to harvest irregular wave. • The output performance rises by 114.136 times as the wave changes. • Random wave motion is transfigured into bidirectional continuous rotation. • Wave-based TENG can output 39.67 mA and a peak power density of 30.62 W/m3. • The output achieves 0 % attenuation rate after operating for 7 h or within 90 %RH. Wave is inherently characterized by disorder and randomness, which is a great challenge for the conventional wave-based triboelectric nanogenerator (W-TENG) and necessitates conducting adaptability research on the device. Therefore, we proposed a morphological transformation strategy, that is, W-TENG can actively transform the motion patterns of self-structure to accommodate the variations in waves and achieve power improvement. And a morphological transformation TENG (MT-TENG) with multi-mode operation is developed for harvesting irregular wave energy. Furthermore, the disorder wave motion is transformed into a bidirectional continuous rotation of power generation units, which realizes the continuous waveform output. Experimental results demonstrate that the wave power grows by 9.22 times with frequency increase, and the device's performance increases by 114.136 times utilizing this strategy. MT-TENG can output 39.67 mA through the energy management circuit (EMC) and a peak power density of 30.62 W/m3 under the wave excitation of 1.1 Hz. Finally, the self-powered environmental monitoring system is constructed, which can illuminate ten 30 W LEDs in series and provide a continuous energy supply to the wireless sensor module. This work presents a research paradigm for the design of wave-environment adaptability, holding significant implications for improving performance and constructing self-powered sensing systems. [ABSTRACT FROM AUTHOR]

Low-velocity water flow exists generally in open channel environments, and harvesting energy from these water flows remains a challenge. Herein, a savonius flapping wing triboelectric–electromagnetic hybrid generator (SFW-TEHG) is proposed to harvest the low-velocity water flow energy by the reciprocating flapping of the savonius flapping wing. Whereafter, the reciprocating flapping is converted into the high-frequency rotating of the energy conversion part by the symmetrical distributed ratchet-gear-rack compound transmission mechanism, thus realizing the conversion of hydrokinetic energy into electricity. Under the water flow velocity of 0.21 m/s, the open-circuit voltage peak and the short-circuit current peak of the TENG reach 1.57 kV and 30.94 μA, and that of the EMG reach 6.24 V and 3.76 mA, respectively. In application demonstration, the SFW-TEHG can drive wireless sensors to monitor the environment. The SFW-TEHG furnishes a solution for the difficulty of harvesting low-velocity water flow energy and powering microsensors installed widely. [Display omitted] • A triboelectric-electromagnetic hybrid generator based on savonius flapping wing is proposed to harvest water flow energy. • A pitching mechanism is designed to decouple the pitching and flapping of SFW, which can harvest the low-velocity water flow energy. • A ratchet-gear-rack mechanism is used to convert the low-frequency flapping of SFW into the high-frequency rotation of TEHG. • A power supply system based on the SFW-TEHG is built to power wireless sensors for realizing self-powered monitoring. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel TENGs-based self-powered siphon rain gauge is proposed. • A multi-tube synergistic sensing strategy with TENG is presented for rain measurement. • A potential collection-based generation strategy is utilized for rain energy harvesting. Rainfall measurement is of great significance to agriculture, weather forecasting and water resource management, while rain energy harvesting is a desirable solution to energy demand of wireless sensor networks of rainfall information. In this work, a novel self-powered siphon rain gauge (SR) integrating with a siphon unit, a sensing unit and an energy harvesting unit is proposed, which can simultaneously measure rainfall information and capture rain energy. In the siphon unit, a siphon structure is used to periodically automatically trigger and stop siphon events. In the sensing unit, a liquid–solid multi-tube triboelectric nanogenerator (TENG) is proposed for the first time to detect rainfall information by a multi-tube synergistic sensing strategy. In the energy harvesting unit, a rotary TENG excited by the siphon emptying event is utilized to generate electricity by a rainwater potential energy collection-based generation strategy. After optimization design, the water level resolution of the multi-tube TENG is around 2.5 times higher than that of traditional single-tube TENG, resulting in a rainfall resolution of 20.45 μm of SR. Besides, the rotary TENG successfully converts random, disordered, high-entropy raindrops energy into regular, ordered, low-entropy fluid mechanical energy. It can finally help the SR achieve a power density of 97.2 µW/m2, which is nearly 2.5 times higher than that of liquid–solid contact TENG using the traditional instantaneous impact-based generation strategy. The proposed self-powered SR not only obtains an excellent real-time rainfall sensing capability, but also has remarkable rain energy harvesting ability. Therefore, this SR has great potential for extensive applications in the hydrology and meteorology fields. [ABSTRACT FROM AUTHOR]

[Display omitted] • An automatic-mode-transition (AMT) strategy is proposed for breeze exploitation. • The maglev-enabled AMT strategy achieves significantly reduced material abrasion. • An AMT triboelectric-electromagnetic hybrid nanogenerator (AMT-TEHG) is developed. • The AMT-TEHG can work under a low wind speed of 2.4 m/s. • The AMT-TEHG achieves very high mechanical durability and electrical stability. Exploiting the pervasive breeze energy is normally difficult due to the high start-up wind speed of the conventional electromagnetic generator (EMG) and the material abrasion of the emerging triboelectric nanogenerator (TENG). We report herein an automatic-mode-transition (AMT) strategy, which enables the TENG to work in intermittent-contact (IC) mode under a low wind speed of 2.4 m/s and automatically transition to noncontact (NC) mode with the increasing wind speed. Realized with a rationally designed maglev mechanism, the AMT-TENG can replenish the dissipated charges with very small friction drag and minute material abrasion, contributing to a low start-up speed, high mechanical durability, and enhanced electrical stability. During a 10-day durability test, the AMT-TENG can maintain 82 % of its incipient voltage; by contrast, the NC-TENG and C-TENG only retain 36 % and 10 % output voltage, respectively. The AMT-TENG can be upgraded easily to an AMT triboelectric-electromagnetic hybrid nanogenerator (AMT-TEHG) by simply adding pick-up coils, allowing the device to generate complementary electric outputs. By exploiting the breeze energy, the AMT-TEHG can serve not only as a self-sufficient wind speed sensor but also as a green energy source for some electronics. This work demonstrates a promising strategy for realizing robust TEHGs, which has great potential in breeze energy exploitation and self-sufficient sensing. [ABSTRACT FROM AUTHOR]

[Display omitted] • A bioinspired butterfly wings triboelectric nanogenerator is designed. • Low-frequency wave energy is efficiently harvested by drag amplification. • The prototype can harvest multidirectional underwater-wave energy. • The prototype immersed in water has excellent durability. Underwater-wave energy, as a kind of abundant but neglected renewable energy, is challenging to be efficiently harvested due to the low frequency and random moving direction. In this work, a bioinspired butterfly wings triboelectric nanogenerator (BBW-TENG) is proposed for multidirectional wave energy harvesting from the underwater environment, which is composed of a shell with bionic blades and the generation units. The parameters for the shape and number of blades are analyzed by computational fluid dynamics (CFD) to determine the optimal structural parameters and verify that the bionic blades have the characteristic of drag amplification. What's more, the BBW-TENG responds sensitively to the multidirectional underwater-wave excitation, which demonstrates the ability to harvest multidirectional and low-frequency underwater-wave energy. The output performance of 400 V, 2.9 µA, and 0.31 µC can be generated with the frequency of 1.25 Hz. In practical applications, it is verified that the BBW-TENG can provide power supply for the electronic devices. And the BBW-TENG immersed in water for 45 days indicates excellent durability without diminished electrical performance. Therefore, this work gives a new approach of harvesting underwater-wave energy to long-term power supply for the distributed sensors. [ABSTRACT FROM AUTHOR]

A charge handling triboelectric nanogenerator (CH-TENG) with synchronous mechanism is proposed to effectively improve the output performance. The charges are injected into the main-TENG through the pump-TENG and charge handling module, therefore the rapid accumulation of charges is achieved. The experimental results depict that CH-TENG obtains open-circuit voltage 1200 V, short-circuit current 75 μA, instantaneous output power 27 mW, and the transferred charge reaches 0.8 μC at a frequency of 1.5 Hz. [Display omitted] • A charge handling mechanism is proposed to improve the charge density of triboelectric nanogenerators. • Using synchronization mechanism to make pump-TENG and main-TENG operate in phase and at unique frequency. • After the main-TENG undergoes charge processing, the transferred charge in one cycle increases from 12 nC to 800 nC. • The final stable output power of CH-TENG reaches 27 mW at a frequency of 1.5 Hz. • CH-TENG stably captures wind energy and stably and continuously supplies power to hygrothermograph. Triboelectric nanogenerator (TENG), as an effective environmental energy harvesting device, provides a promising method for powering electronic devices with low power consumption. However, the low surface charge density of the triboelectric layer limits its practical application. In this paper, a charge handling triboelectric nanogenerator (CH-TENG) with synchronous mechanism is proposed to effectively improve the output performance. It consists of the pump-TENG, the main-TENG, and charge handling circuit. Through the cooperation of the pump-TENG and charge handling module, the extra charges are injected into the main-TENG, rapid charge accumulation is achieved. The experimental results depict that CH-TENG obtains open-circuit voltage 1200 V, short-circuit current 75 μA, instantaneous output power 27 mW, and the transferred charge reaches 0.8 μC at a frequency of 1.5 Hz. Under the wind speed of 6 m/s, CH-TENG spent 39 s to charge the 220 μF capacitor to 3.0 V, and finally stabilized at 1.26 V to keep the hygrothermograph working stably. The CH-TENG provides a significant reference for improving the high-performance output harvest wind energy in the environment. [ABSTRACT FROM AUTHOR]

To harvest wind energy effectively, this paper proposes an optimization strategy of wind energy harvesting via triboelectric-electromagnetic flexible cooperation. It flexibly and reasonably combines the advantages of the triboelectric nanogenerator (TENG) and electromagnetic generator (EMG) in different wind speed environments. Based on the optimization strategy, the flexible cooperation triboelectric-electromagnetic harvester (FC-TEH) is designed, which can flexibly adjust energy harvesting capacity according to variants in wind speed and better adapt to the instability of natural wind. [Display omitted] • An optimization strategy of wind energy harvesting is proposed. • The optimization strategy combines complementary advantages of the TENG and EMG. • A flexible cooperation triboelectric-electromagnetic harvester is designed. • The FC-TEH can flexibly adjust energy harvesting capacity. • The FC-TEH could adapt well to the instability of natural wind. As a favorable renewable energy source, wind energy has the advantages of large reserves and wide distribution. To harvest wind energy effectively, an optimization strategy of wind energy harvesting is proposed in this paper, which flexibly combines the complementary advantages of the triboelectric nanogenerator (TENG) and electromagnetic generator (EMG) in different energy harvesting environments. Specifically, in weak wind environments, the TENG operates independently to harvest energy. While, once the wind speed increases to the critical wind speed, the EMG starts and operates coordinately with the TENG, which will effectively increase the energy harvesting capacity of the wind energy harvester. Based on this optimization strategy, the flexible cooperation triboelectric-electromagnetic harvester (FC-TEH) is designed. The FC-TEH could flexibly adjust energy harvesting capability according to variants of wind speed and adapt to the instability of natural wind. Experiments demonstrate that at the critical wind speed of 6 m/s, the FC-TEH reaches the critical speed (108 rpm). At natural wind speeds of about 8 m/s, the FC-TEH can successfully power a Bluetooth thermometer with a rated power of 20 mW. The optimization strategy will provide important guidance and reference for wind energy harvesting. [ABSTRACT FROM AUTHOR]

[Display omitted] • The breeze-driven triboelectric nanogenerator is proposed. • The prototype can harvest the breeze energy efficiently. • The start-up wind speed of the prototype is as low as 3.3 m/s. • The energy conversion efficiency of the prototype can reach 12.06%. Smart agriculture is becoming an inevitable trend with the wide application of sensor networks. To supply energy for agricultural sensors, the wind energy harvester supports a possible solution. However, the average wind speed on the earth surface is only 3.28 m/s, which cannot easily be harvested by traditional generators efficiently. To efficiently harvest breeze energy in the farmland environment, a breeze-driven triboelectric nanogenerator (BD-TENG) was proposed. By selecting lightweight rotor materials and designing suitable wind scoops structures, the start-up wind speed of BD-TENG is as low as 3.3 m/s, and when the wind speed is 4 m/s, the energy conversion efficiency of the BD-TENG can reach 12.06%. Moreover, under 4 m/s wind speed, the output performance of the BD-TENG is 330 V, 7 μA, 137 nC, and the peak power is 2.81 mW. So, the BD-TENG is easier to operate normally even in low wind speed environments and can harvest natural breeze energy efficiently. Experiments prove that in natural environments, the BD-TENG successfully lights up 300 red and blue light-emitting diodes in series, which can be applied to increase lighting time for plants at night. Moreover, the BD-TENG can power a soil thermometer by harvesting natural breeze energy. Therefore, the BD-TENG can be widely used in farmland environments to provide energy for agricultural sensor networks. The BD-TENG has bright prospects in smart agriculture and can promote its sustainable development. [ABSTRACT FROM AUTHOR]