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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.

This study introduces the Tympanic Membrane Metamaterial inspired acoustic Triboelectric Nanogenerator (TMM-TENG), which exhibits subwavelength structural dimensions and effective sound absorption within low-frequency ranges. The performance of acoustic energy harvesting is increased by replacing rigid bottom of the acoustic cavity with an elastic part and introducing a point-surface mechanism. Experimental tests employing the proposed mechanism are then conducted. The obtained results show a remarkable 2220 % increase in the output voltage of the TMM-TENG compared with the traditional approach. As for the acoustic energy harvesting performance, for a sound pressure level (SPL) of 95 dB, the peak-to-peak value of the output voltage reaches 500 V, with a measured current of 40 μA and a maximum output power of 3.05 mW. Moreover, the incorporation of an elastic part into the TMM-TENG proves advantageous in the manipulation of low-frequency sound waves. The acoustic performance of the device can also be regulated by adjusting the thickness of the elastic part. In addition, multiple TMM-TENGs with varying elastic part thicknesses are placed on a duct, and band-limited white noise is generated to evaluate the sound reduction ability without limiting the air ventilation. Furthermore, the mounted TMM-TENG allows to perform of self-powered wireless temperature sensing and acoustic telecommunication functionalities. [Display omitted] • A deep-subwavelength tympanic membrane metamaterial inspired TENG is proposed. • Simultaneous realization of acoustic energy harvesting and noise control is achieved. • Self-powered low-frequency acoustic telecommunication is demonstrated. [ABSTRACT FROM AUTHOR]

In this study, we present a new device designed to manipulate low-frequency sound waves. The device utilizes the principles of acoustic metamaterials to achieve high-performance sound insulation, while also possessing the capability to convert sound energy into electrical energy. Unlike previous studies on membrane acoustic metamaterials, this device incorporates a membrane component but eliminates the need for precise tension force. The structural parameters of the device are frequency-dependent, allowing for a lightweight design while maintaining satisfactory low-frequency sound insulation performance. At the sound insulation peak frequency, the IAM-TENG exhibits an impressive sound insulation capability of over 30 dB. Moreover, when subjected to bandlimited white noise excitation in the frequency range of 50 Hz-500 Hz, the IAM-TENG showcases a substantial enhancement of nearly 10 dB in sound insulation performance in comparison to a sample of the same weight and size. Additionally, the device achieves a uniform displacement distribution, with large amplitude displacement occurring around the sound transmission dip frequency. Exploiting this property, we have designed a triboelectric nanogenerator (TENG) that can convert incident acoustic energy into electrical energy. This nanogenerator structure utilizes multi-walled carbon nanotubes (MWCNTs) and FEP (Fluorinated Ethylene Propylene) membrane as the triboelectric layers. With an acoustic excitation level of 100 dB at the optimal frequency, the harvested electrical power reaches 0.93 mW. The device has a surface mass density of only 2 kg / m 2 , yet it provides remarkable acoustic insulation performance and can power small-scale electronic devices. These innovative properties have the potential to accelerate the development of self-powered, smart, and multifunctional structures in the Internet of Things era. [Display omitted] • A novel metamaterial-inspired TENG is proposed, which can realize high-performance acoustic-electrical conversion. • Tensioned force is omitted while the membrane component is still retained, which can help the structure to be lightweight. • The dynamic performance of the device can be regulated and the device can achieve desired noise insulation. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs) have high potential in self-powered sensing and energy harvesting applications. In general, TENGs' internal source resistance is high, and their output power varies under different load resistance values. Therefore, a resistance box is required to evaluate their energy harvesting performance and obtain the power curve under different load values. The load tuning process is usually performed by hand. This repetitive process is time-consuming and error-prone. Consequently, an Automated Power Evaluation Workbench (APEW) is developed, making the resistance switching and power measuring process program-controlled. The resistance value is resolved using the Octal decomposition principle. In addition, a resistance synthesis algorithm is proposed to alter the resistance value with a minimum step of 1 Ohm. The target resistance value is physically synthesized by relay switching, while digital lines control the relays. The proposed APEW is then evaluated experimentally, and the obtained results are compared with those of the traditional manual switching approach. It is deduced that the two power curves are almost identical. Therefore, it is believed that the proposed APEW will play a crucial role in TENG's further development. [ABSTRACT FROM AUTHOR]

Abstract Recently, flutter-driven triboelectric nanogenerator (TENG) has shown huge potential in wind energy harvesting from ambient environments. However, almost all the reported devices are based on parallel structure which suffers from a critical problem of insufficient contact between triboelectric surfaces. In this work, we propose an angle-shaped TENG (AS-TENG) with the above issue resolved. The device is based on two Al layers stacked to form an angle shape and a FEP film positioned in between by sharing a common side. Thanks to this design, the FEP film can contact fully and intimately with the Al layers to facilitate the effect of contact electrification and electrostatic induction. Compared with the existing parallel-structured TENG, the AS-TENG shows an overwhelming output performance because of the enhanced contact area. Furthermore, the AS-TENG is introduced a wedge-shaped wind guide channel which can provide a driving force for the flutter and hence lower the start-up wind speed largely. To further enhance the electric output, the AS-TENGs can be facilely integrated into a 360° radial array, showing an enlarged windward area and a high level of integration. The AS-TENG array can be applied to harvest outdoor weak wind and act as a direct power source to charge a capacitor or drive electronic devices. This work provides a design strategy for natural weak wind scavenging which may push forward the practical applications of TENG for wind power. Graphical abstract fx1 Highlights • An AS-TENG has been demonstrated and shows enhanced performance in comparison with the reported parallel-structured devices. • A wedge-shaped wind guide channel is introduced to facilitate the flutter and hence lower the start-up wind speed largely. • The AS-TENG can be facilely integrated into a 360° radial array for efficiently harvesting natural weak wind outdoors. [ABSTRACT FROM AUTHOR]

A metamaterial-inspired triboelectric nanogenerator (META-TENG) is proposed in this work to simultaneously realize vibration suppression and energy harvesting. The compact META-TENG can generate low frequency local resonant phenomenon and significantly reduce the incident vibration at the low-frequency band. A planar spring is created, which guarantees low-frequency resonance and a sufficient triboelectric contact surface within a small-scale device. The bandgap property of the proposed metamaterial is then calculated using the finite element method and corresponds well with the experimental measurement results. To fabricate the TENG, fluorinated ethylene propylene (FEP) film and Ecoflex are employed as the negative and positive triboelectric materials, respectively. It is found that the introduction of multi-walled carbon nanotubes (MWCNTs) into Ecoflex is favorable for enhancing the META-TENG's output performance, increasing the output voltage by almost three times. The charge density of the TENG can reach up to 453.1 μ C / m 2 under 5 N sinuous excitation. The periodic META-TENG configuration also exhibits satisfying vibration suppression performance, where the vibration amplitude of an aluminum plate integrating four META-TENGs is minimized by up to 87 %. The harvested energy from the META-TENG array enables an accelerometer and Bluetooth module to work in wireless mode, making the whole system achieve self-powered vibration monitoring. [Display omitted] • A metamaterial-inspired triboelectric nanogenerator (META-TENG) is proposed with a compact and simple structure. • The META-TENG can simultaneously achieve low-frequency vibration suppression and energy harvesting. • The META-TENG can suppress nearly 90% of vibrations and harvest energy for wireless self-powered structure monitoring. [ABSTRACT FROM AUTHOR]

With the advantages of low power consumption, low cost and miniaturization, self-powered sensors have a wide range of applications in the human-machine interface, Internet of Things (IoTs), sports monitoring and versatile fields. Here, a novel and easy-processing self-powered triboelectric multi-information motion monitoring sensor (TM3S) is proposed and systemically investigated under the conditions of rolling and sliding motion. The relationships between electrical signals (charge, rate of charge change, current, rate of current change, voltage, etc.) and kinetic parameters (displacement, direction, velocity, acceleration, etc.) are established and verified with various motion states. The results show that TM3S can precisely detect the displacement, direction, velocity, and acceleration of the moving object, demonstrating excellent performance in motion monitoring. Furthermore, a wireless self-powered motion monitoring system based on TM3S is developed, which can detect the movement of a sliding mouse in real time, wirelessly transmit sensing data instantaneously, and achieve real-time control in human-machine interface. The real-time motion monitoring system exhibits two significant advantages of high sensitivity and self-powered nature, showing huge potential in low power consumption IoTs and intelligent human-machine interaction. [Display omitted] • An easy-processing self-powered triboelectric multi-information motion monitoring sensor (TM3S) is proposed. • The TM3S can detect the displacement, direction, velocity, and acceleration of the moving object with superb performance. • A wireless self-powered motion monitoring system based on TM3S is applied for remote control in human-machine interface. [ABSTRACT FROM AUTHOR]

The wind vector sensor is a significant category of Internet of Things (IoTs) based sensors due to its irreplaceable role in weather monitoring, traffic detection, and mine safety. However, searching new power supply approaches, apart from batteries, for this type of sensor is a critical issue hindering its widespread application because of the vast number of sensor nodes. Self-powered technology based on nanogenerator offers great promise for resolving the dilemma. Herein, we propose a novel wind vector sensor system for synchronously perceiving wind speed and direction based on the coupling of self-powered triboelectric sensor and photoelectric technology. For wind speed detection, an angle-shaped triboelectric sensor (ASTS) is well designed and systemically investigated. The ASTS after structure optimization exhibits a low start-up wind speed and considerable outputs. A wide wind speed sensing range is achieved from 2.9 m/s to 24.0 m/s, within which the current frequency of ASTS shows a good proportional relationship with wind speed. Furthermore, a wind direction sensor (WDS) based on photoelectric detection is carefully fabricated to integrate with the ASTS for wind vector monitoring. Specific algorithms and programs are developed through the LabVIEW platform to process the electric signals from the system and visually display the results on the screen. The practical application demonstrates that the proposed wind vector sensing system is capable of accurately identifying wind speed from eight directions. This work would pave the way to achieve the ultra-low power consumption for IoTs-based environmental sensors. [Display omitted] • The wind vector system is proposed by the integration of triboelectric and photoelectric technology. • The fluid dynamic and triboelectric characteristics are investigated for low start-up wind speed and considerable output. • The wind vector system realizes accurate sensing with a wide range from 2.9 m/s to 24.0 m/s for eight wind directions. [ABSTRACT FROM AUTHOR]

Low-frequency acoustic energy harvesting is of great significance in the academic field and industry. In this work, we propose a 3D-printed acoustic triboelectric nanogenerator (A-TENG) with the properties of structural controllability, one-time molding, easy fabrication, and low cost. A quarter-wavelength acoustic resonator system based on the A-TENG is demonstrated and systemically investigated for high-performance acoustic energy scavenging. The system is capable of generating a power output of 4.33 mW under 100 dB sound pressure level excitation. Up to 72 LEDs and a commercial calculator can be directly and continuously driven by the acoustic resonator system, indicating its application as a power source for electronic devices. Furthermore, we develop a self-powered edge sensing system consisting of the A-TENG, an AI speech recognition chip, and control circuits. The speech signals can be firstly converted into electrical signals through the A-TENG, and then recognized and processed by the AI chip with a built-in and pre-trained neural network to control the follow-up circuits. The self-powered edge sensing system is capable of real-time speech recognition without cloud computing, exhibiting great potential in the field of low-power and cost-effective intelligent Internet of Things. [Display omitted] • A 3D-printed A-TENG is proposed with the properties of structural controllability, one-time molding, and easy fabrication. • The A-TENG is demonstrated for high-performance acoustic energy scavenging. • A self-powered AI edge sensing system is developed for real-time speech recognition without cloud computing. [ABSTRACT FROM AUTHOR]

As the world entering the era of internet of things (IoTs), billions of sensor nodes call for the energy for the new era, which is important application of entropy in energy science. Energy harvesting and self-powered technology based on triboelectric nanogenerator (TENG) have been widely recognized as effective solution to providing "random" energy for the "random" units in IoTs. Contact-separation mode, which is one of the most fundamental working mode of TENG, has shown promising potential in mechanical energy harvester and self-powered sensors. In this work, a seesaw structured triboelectric nanogenerator (SS-TENG) is proposed based on contact-separation mode. This structure can largely enhance the relative motion velocity between two tribo-surfaces, and hence improve the output performance of the device. Furthermore, the electric signals of the SS-TENG can be tuned by structure modification to be asymmetric, which can be utilized to monitor the motion direction and velocity of passing objects as well as movement of human foot. After employing C programming, the output signals can be identified and logically analyzed through electric circuits or computers, enabling visual display of sensing results for practical applications. Therefore, this work not only provides a new way of performance enhancement for TENG but also proposes a novel strategy for self-powered motion sensing, showing great potential in the fields of mechanical energy scavenging, traffic monitoring, healthcare sensing, sports rehabilitation, and corrective exercise. Image 1 • Design a seesaw structured TENG with enhenced performance due to the fast changing rate of contact-separation process. • The electric signals of the device can be tuned by asymmetric design structure for application in sensing motion direction, velocity, and human foot motion. • Through C programming, the signals can be identified by circuit, enabling visual display of sensing results for applications. [ABSTRACT FROM AUTHOR]

This study introduces a novel self-powered metamaterial augmented nanogenerator for low-frequency acoustic telecommunication (MANLAT), which is designed to enhance acoustic communication capabilities by utilizing the local resonance mechanism to selectively amplify specific frequency bands of incident sound and generate large amplitude signals in a self-powered manner. The MANLAT device consists of a flexible bottom that responds to pressure differences by generating strong vibrations. Additionally, a lightweight cone-shaped component is attached to the central part of the flexible plate, thus increasing the surface area in that region. Through contact electrification and electrostatic induction mechanisms, a substantial electrical signal is generated, allowing the device to serve as a self-powered acoustic telecommunication receiver. To assess its performance in real-world scenarios, environmental interference was simulated by generating white noise added to the modulated waveform containing information, which was then transmitted through a loudspeaker. At the receiving end, a high-precision microphone sensor was used alongside the MANLAT device to capture the sound wave. The experimental results demonstrate that the MANLAT device surpassed the microphone sensor in mitigating noise interference and enabled the effective decoding of information even in the presence of high levels of white noise or background music. Consequently, the device simplifies communication systems, facilitates reliable and environmentally friendly communication, and enhances information security. [Display omitted] • A self-powered low frequency acoustic telecommunication device is proposed. • The device shows strong anti-interference capability. • Covert communication is demonstrated with background music. [ABSTRACT FROM AUTHOR]