Robust Swing‐Structured Triboelectric Nanogenerator for Efficient Blue Energy Harvesting

Ocean wave energy is a promising renewable energy source, but harvesting such irregular, “random,” and mostly ultra‐low frequency energies is rather challenging due to technological limitations. Triboelectric nanogenerators (TENGs) provide a potential efficient technology for scavenging ocean wave energy. Here, a robust swing‐structured triboelectric nanogenerator (SS‐TENG) with high energy conversion efficiency for ultra‐low frequency water wave energy harvesting is reported. The swing structure inside the cylindrical TENG greatly elongates its operation time, accompanied with multiplied output frequency. The design of the air gap and flexible dielectric brushes enable mininized frictional resistance and sustainable triboelectric charges, leading to enhanced robustness and durability. The TENG performance is controlled by external triggering conditions, with a long swing time of 88 s and a high energy conversion efficiency, as well as undiminished performance after continuous triggering for 4 00 000 cycles. Furthermore, the SS‐TENG is demonstrated to effectively harvest water wave energy. Portable electronic devices are successfully powered for self‐powered sensing and environment monitoring. Due to the excellent performance of the distinctive mechanism and structure, the SS‐TENG in this work provides a good candidate for harvesting blue energy on a large scale.     

A Nonencapsulative Pendulum‐Like Paper–Based Hybrid Nanogenerator for Energy Harvesting

The newly invented triboelectric nanogenerator (TENG) is deemed to be a more efficient strategy than an electromagnetic generator (EMG) in harvesting low‐frequency (<2 Hz) water wave energy. Various TENGs with different structures and functions for blue energy have been developed, which can be roughly divided into two types: liquid–solid contact electrification TENGs and fully enclosed solid–solid contact electrification TENGs. Robustness and packaging are critical factors in the development of TENGs toward practical applications. Furthermore, for fully enclosed TENGs, the requirements and costs of packaging are very high, and they can difficult to disassemble after enclosed, if there is something wrong with the devices. Herein, a nonencapsulative pendulum‐like paper based hybrid nanogenerator for energy harvesting is designed, which mainly consists of three parts, one solar panel, two paper based zigzag multilayered TENGs, and three EMG units. This unique structure reveals the superior robustness and a maximum peak power of zigzag multilayered TENGs up to 22.5 mW is realized. Moreover, the device can be used to collect the mechanical energy of human motion in hand shaking. This work presents a new platform of hybrid generators toward energy harvesting as a portable practical power source, which has potential applications in navigation and lighting.     

Multiple‐Frequency High‐Output Triboelectric Nanogenerator Based on a Water Balloon for All‐Weather Water Wave Energy Harvesting

Energy and the environment are two of the main issues facing the world today. As a consequence abundant renewable green energy sources such as wave energy, have become hot topics. Here, a multiple‐frequency triboelectric nanogenerator based on the water balloon (WB‐TENG) is proposed for harvesting water wave energy in any direction. Owing to the high elasticity of the water balloon, the WB‐TENG can realize a multiple‐frequency response to low‐frequency external mechanical simulations to generate high‐frequency electrical output. In addition, the water balloon can achieve self‐support without any additional supporting structure because of its tension, to make WB‐TENG still produce electrical output under slight vibration, which can also bring high energy conversion efficiency. Moreover, the fabricated WB‐TENG generates a maximum instantaneous short‐circuit current and an open‐circuit voltage of 147 µA and 1221 V, respectively. Most noteworthy, under the same conditions, the total transferred charge of WB‐TENG is 28 times than that of traditional TENG based on double plate structure during one working cycle. Therefore, this design can provide an effective way to promote the development of TENGs in blue energy.     

Triboelectric Nanogenerator Based on Fully Enclosed Rolling Spherical Structure for Harvesting Low‐Frequency Water Wave Energy

Water waves are increasingly regarded as a promising source for large‐scale energy applications. Triboelectric nanogenerators (TENGs) have been recognized as one of the most promising approaches for harvesting wave energy. This work examines a freestanding, fully enclosed TENG that encloses a rolling ball inside a rocking spherical shell. Through the optimization of materials and structural parameters, a spherical TENG of 6 cm in diameter actuated by water waves can provide a peak current of 1 μA over a wide load range from a short‐circuit condition to 10 GΩ, with an instantaneous output power of up to 10 mW. A multielectrode arrangement is also studied to improve the output of the TENG under random wave motions from all directions. Moreover, at a frequency of 1.43 Hz, the wave‐driven TENG can directly drive tens of LEDs and charge a series of supercapacitors to rated voltage within several hours. The stored energy can power an electronic thermometer for 20 min. This rolling‐structured TENG is extremely lightweight, has a simple structure, and is capable of rocking on or in water to harvest wave energy; it provides an innovative and effective approach toward large‐scale blue energy harvesting of oceans and lakes.     

Self‐Powered Wireless Sensor Node Enabled by a Duck‐Shaped Triboelectric Nanogenerator for Harvesting Water Wave Energy

This paper presents a fully enclosed duck‐shaped triboelectric nanogenerator (TENG) for effectively scavenging energy from random and low‐frequency water waves. The design of the TENG incorporates the freestanding rolling mode and the pitch motion of a duck‐shaped structure generated by incident waves. By investigating the material and structural features, a unit of the TENG device is successfully designed. Furthermore, a hybrid system is constructed using three units of the TENG device. The hybrid system achieves an instantaneous peak current of 65.5 µA with an instantaneous output power density of up to 1.366 W m^?2. Following the design, a fluid–solid interaction analysis is carried out on one duck‐shaped TENG to understand the dynamic behavior, mechanical efficiency, and stability of the device under various water wave conditions. In addition, the hybrid system is experimentally tested to enable a commercial wireless temperature sensor node. In summary, the unique duck‐shaped TENG shows a simple, cost‐effective, environmentally friendly, light‐weight, and highly stable system. The newly designed TENG is promising for building a network of generators to harvest existing blue energy in oceans, lakes, and rivers.     

A Water‐Proof Triboelectric–Electromagnetic Hybrid Generator for Energy Harvesting in Harsh Environments

Packaging is a critical aspect of triboelectric nanogenerators (TENG) toward practical applications, since the performance of TENG is greatly affected by environmental conditions such as humidity. A waterproof triboelectric–electromagnetic hybrid generator (WPHG) for harvesting mechanical energy in harsh environments is reported. Since the mechanical transmission from the external mechanical source to the TENG is through a noncontact force between the paired magnets, a fully isolated packaging of TENG part can be easily achieved. At the same time, combining with metal coils, these magnets can be fabricated to be electromagnetic generators (EMG). The characteristics and advantages of outputs from both TENG and EMG are systematically studied and compared to each other. By using transformers and full‐wave rectifiers, 2.3 mA for total short‐circuit current and 5 V for open‐circuit voltage are obtained for WPHG under a rotation speed of 1600 rpm, and it can charge a supercapacitor (20 mF) to 1 V in 22s. Finally, the WPHG is demonstrated to harvest wind energy in the rainy condition and water‐flow energy under water. The reported WPHG renders an effective and sustainable technology for ambient mechanical energy harvesting in harsh environments. Solid progress in both the packaging of TENG and the practical applications of the hybrid generator toward practical power source and self‐powered systems is presented.     

Broadband Vibrational Energy Harvesting Based on a Triboelectric Nanogenerator

Vibrations in living environments are generally distributed over a wide frequency spectrum and exhibit multiple motion directions over time, which renders most of the current vibration energy harvesters unpractical for their harvesting purposes. Here, a 3D triboelectric nanogenerator (3D‐TENG) is designed based on the coupling of the triboelectrification effect and the electrostatic induction effect. The 3D‐TENG operates in a hybridization mode of conjuntioning the vertical contact‐separation mode and the in‐plane sliding mode. The innovative design facilitates harvesting random vibrational energy in multiple directions over a wide bandwidth. An analytical model is established to investigate the mechano‐triboelectric transduction of 3D‐TENG and the results agree well with experimental data. The 3D‐TENG is able to harvest ambient vibrations with an extremely wide working bandwidth. Maximum power densities of 1.35 W m^‐2 and 1.45 W m^‐2 are achieved under out‐of‐plane and in‐plane excitation, respectively. The 3D TENG is designed for harvesting ambient vibration energy, especially at low frequencies, under a range of conditions in daily life and has potential applications in environmental/infrastructure monitoring and charging portable electronics.     

Networks of High Performance Triboelectric Nanogenerators Based on Liquid–Solid Interface Contact Electrification for Harvesting Low‐Frequency Blue Energy

Blue energy harvested from the ocean is an important and promising renewable energy for the sustainable development of society. Triboelectric nanogenerators (TENGs) are considered one of the most promising approaches for harvesting blue energy. In this work, a liquid–solid‐contact triboelectric nanogenerator (LS TENG) is fabricated to enhance the friction and magnify energy output by 48.7 times, when compared with the solid–solid‐contact TENG with the same area. The buoy‐like LS TENG can harvest energy from different types of low‐frequency vibration (including up–down, shaking, and rotation movements). Moreover, the outputs of the LS TENGs network can reach 290 µA, 16 725 nC, and 300 V, and the LS TENGs network can directly power hundreds of LEDs and drive a radio frequency emitter to form a self‐powered wireless save our souls (SOS) system for ocean emergencies. This work renders an innovative and effective approach toward large‐scale blue energy harvesting and applications.     

Energy Harvesting from Breeze Wind (0.7–6 m s−1) Using Ultra‐Stretchable Triboelectric Nanogenerator

Wind is one of the most important sources of green energy, but the current technology for harvesting wind energy is only effective when the wind speed is beyond 3.5–4.0 m s^?1. This is mainly due to the limitation that the electromagnetic generator works best at high frequency. This means that light breezes cannot reach the wind velocity threshold of current wind turbines. Here, a high‐performance triboelectric nanogenerator (TENG) for efficiently harvesting energy from an ambient gentle wind, especially for speeds below 3 m s^?1 is reported, by taking advantage of the relative high efficiency of TENGs at low‐frequency. Attributed to the multiplied‐frequency vibration of ultra‐stretchable and perforated electrodes, an average output of 20 mW m^?3 can be achieved with inlet wind speed of 0.7 m s^?1, while an average energy conversion efficiency of 7.8% at wind speed of 2.5 m s^?1 is reached. A self‐charging power package is developed and the applicability of the TENG in various light breezes is demonstrated. This work demonstrates the advantages of TENG technology for breeze energy exploitation and proposes an effective supplementary approach for current employed wind turbines and micro energy structure.     

Oblate Spheroidal Triboelectric Nanogenerator for All‐Weather Blue Energy Harvesting

Triboelectric nanogenerators (TENGs) provide one of the most promising techniques for large‐scale blue energy harvesting. However, lack of reasonable designs has largely hindered TENG from harvesting energy from both rough and tranquil seas. In this paper, an oblate spheroidal TENG assembled by two novel TENG parts is elaborately designed for both situations. The TENG in the upper part is based on spring steel plates without other substrate materials, which makes it possible to output considerable power in rough seas and occupy small space. The TENG in the lower part consists of two copper‐coated polymer films and a rolling ball which can capture small wave energy from tranquil seas. The working mechanism and output performance are systematically studied. A maximum open‐circuit voltage of 281 V and a short‐circuit current of 76 µA can be achieved by one upper part, enough to charge a commercial capacitor for potential applications. More important, the proposed oblate spheroidal shell not only guarantees high sensitivity of the TENG in the lower part, but also qualifies the TENG with unique self‐stabilization and low consumables for the next generation of TENGs with new structural design toward all‐weather blue energy harvesting.     

Mechanical Regulation Triboelectric Nanogenerator with Controllable Output Performance for Random Energy Harvesting

Recycling of random mechanical energy in the environment has become an important research hotspot. The triboelectric nanogenerators (TENGs) were invented to harvest energy, and have been widely applied due to their simple structure, small size, and low cost. This paper reports a mechanical regulation triboelectric nanogenerator (MR‐TENG) for the first time with controllable output performance used to harvest random or irregular energy in the environment. It comprises a transmission unit, switch structure, generator unit, flywheel, and shell. Random linear motion or rocking motion is transferred via the transmission unit to the flywheel. The rotor of the generator unit fixed on the flywheel and the stator of the generator unit fixed on the shell combine. By controlling the storage and release of energy in the flywheel, the switch structure assists the flywheel to convert random or irregular energy into a controllable and stable energy output. The MR‐TENG can generate an open‐circuit voltage of 350 V, a short‐circuit current of 12 μA, a transfer charge of 130 nC, and a peak power of 2.52 mW. Furthermore, a thermometer and more than 300 light emitting diodes (LEDs) are separately powered by this MR‐TENG in simulated water waves, demonstrating its potential application in water wave energy harvesting.     

Honeycomb Structure Inspired Triboelectric Nanogenerator for Highly Effective Vibration Energy Harvesting and Self‐Powered Engine Condition Monitoring

Vibration in mechanical equipment can serve as a sustainable energy source to power sensors and devices if it can be effectively collected. In this work, a honeycomb structure inspired triboelectric nanogenerator (HSI‐TENG) consisting of two copper electrode layers with sponge bases and one honeycomb frame filled with polytetrafluoroethylene (PTFE) balls is proposed to harvest vibration energy. The application of a compact honeycomb structure increases the maximum power density of HSI‐TENG by 43.2% compared to the square grid structure and provides superior advantages in large‐scale manufacturing. More importantly, the nonspring‐assisted HSI‐TENG can generate electricity once the PTFE balls obtain sufficient kinetic energy to separate from the bottom electrode layer regardless of the vibration frequency and direction. This is fundamentally different from the spring‐assisted harvesters that can only work around their natural frequencies. The vibration model and working criteria of the HSI‐TENG are established. Furthermore, the HSI‐TENG is successfully used to serve as a self‐powered sensor to monitor engine conditions by analyzing the electrical output of the HSI‐TENG installed on a diesel engine. Therefore, the nonspring‐assisted HSI‐TENG provides a novel strategy for highly effective vibration energy harvesting and self‐powered machinery monitoring.     

Long‐Lifetime Triboelectric Nanogenerator Operated in Conjunction Modes and Low Crest Factor

The high‐output triboelectric nanogenerator (TENG) is indispensable for its practical applications toward industrial products. However, the electricity loss in simple parallel connection among all units and the typically high crest factor output seriously hamper the practical applications of TENG. Here, a rectified TENG is reported in parallel structure to solve the problem of electricity loss in simple parallel connection. The rotational contact–separation structure with phase difference between rectified TENGs addresses high crest factor output and extends service life of rotational TENG simultaneously. The current crest factor is dramatically decreased to 1.31 in multiple rectifier multiple TENG in parallel (MRM‐TENG), while that of TENG in simple parallel is higher than 6. Meanwhile, the current output can retain up to ≈93% of its initial performance after 7 200 000 rotations under 2.00 r s^?1 of 1000 h. Furthermore, the equivalent current can be in linear growth with low crest factor by making MRM‐TENG in parallel for distributed energy supply without electricity loss. This work may provide a new strategy for TENG in parallel to achieve a low crest factor output and long‐term cycling stability power generation in distributed energy harvesting for large‐scale power application.     

An Ultrathin Flexible Single‐Electrode Triboelectric‐Nanogenerator for Mechanical Energy Harvesting and Instantaneous Force Sensing

The trends in miniaturization of electronic devices give rise to the attention of energy harvesting technologies that gathers tiny wattages of power. Here this study demonstrates an ultrathin flexible single electrode triboelectric nanogenerator (S‐TENG) which not only could harvest mechanical energy from human movements and ambient sources, but also could sense instantaneous force without extra energy. The S‐TENG, which features an extremely simple structure, has an average output current of 78 μA, lightening up at least 70 LEDs (light‐emitting diode). Even tapped by bare finger, it exhibits an output current of 1 μA. The detection sensitivity for instantaneous force sensing is about 0.947 μA MPa^?1. Performances of the device are also systematically investigated under various motion types, press force, and triboelectric materials. The S‐TENG has great application prospects in sustainable wearable devices, sustainable medical devices, and smart wireless sensor networks owning to its thinness, light weight, energy harvesting, and sensing capacities.     

Charge Pumping Strategy for Rotation and Sliding Type Triboelectric Nanogenerators

Triboelectric nanogenerator (TENG) is an emerging approach for harvesting energy from the living environment. But its performance is limited by the maximum density of surface charges created by contact electrification. Here, by rationally designing a synchronous rotation structure, a charge pumping strategy is realized for the first time in a rotary sliding TENGs, which is demonstrated to enhance the charge density by a factor of 9, setting up a record for rotary TENGs. The average power is boosted by more than 15 times compared with normal TENGs, achieving an ultrahigh average power density of 1.66 kW m^?3, under a low drive frequency of 2 Hz. Moreover, the charge pumping mechanism enables decoupling of bound charge generation and the severity of interfacial friction in the main TENG, allowing surface lubricants to be applied for suppressing abrasion and lowering heat generation. The adaptability of the strategy to rotation and sliding type TENGs in low‐frequency agitations provides a breakthrough to the bottleneck of power output for mechanical energy harvesting, and should have a great impact on high‐power TENG design and practical applications in various fields.     

A Wireless Triboelectric Nanogenerator

A new “wireless” paradigm for harvesting mechanical energy via a 3D‐printed wireless triboelectric nanogenerator (W‐TENG) comprised of an ecofriendly graphene polylactic acid (gPLA) nanocomposite and Teflon is demonstrated. The W‐TENG generates very high output voltages >2 kV with a strong electric field that enables the wireless transmission of harvested energy over a distance of 3 m. The W‐TENG exhibited an instantaneous peak power up to 70 mW that could be wirelessly transmitted for storage into a capacitor obviating the need for hard‐wiring or additional circuitry. Furthermore, the use of W‐TENG for wireless and secure actuation of smart‐home applications such as smart tint windows, temperature sensors, liquid crystal displays, and security alarms either with a single or a specific user‐defined passcode of mechanical pulses (e.g., Fibonacci sequence) is demonstrated. The scalable additive manufacturing approach for gPLA‐based W‐TENGs, along with their high electrical output and unprecedented wireless applications, is poised for revolutionizing the present mechanical energy harvesting technologies.     

Dual‐Tube Helmholtz Resonator‐Based Triboelectric Nanogenerator for Highly Efficient Harvesting of Acoustic Energy

An acoustic wave is a type of energy that is clean and abundant but almost totally unused because of its very low density. This study investigates a novel dual‐tube Helmholtz resonator‐based triboelectric nanogenerator (HR‐TENG) for highly efficient harvesting of acoustic energy. This HR‐TENG is composed of a Helmholtz resonant cavity, a metal film with evenly distributed acoustic holes, and a dielectric soft film with one side ink‐printed for electrode. Effects of resonant cavity structure, acoustic conditions, and film tension on the HR‐TENG performance are investigated systematically. By coupling the mechanisms of triboelectric nanogenerator and acoustic propagation, a theoretical guideline is provided for improving energy output and broadening the frequency band. Specifically, the present HR‐TENG generates the maximum acoustic sensitivity per unit area of 1.23 VPa^?1 cm^?2 and the maximum power density per unit sound pressure of 1.82 WPa^?1 m^?2, which are higher than the best results from the literature by 60 and 20%, respectively. In addition, the HR‐TENG may also serve as a self‐powered acoustic sensor.     

Robust Triboelectric Nanogenerator Achieved by Centrifugal Force Induced Automatic Working Mode Transition

Material abrasion in contact‐based freestanding mode‐triboelectric nanogenerators (FS‐TENGs) seriously deteriorates device mechanical durability and electrical stability, which causes TENGs to be only applicable in the harvesting of mechanical energy at low‐frequency. Here, a wide‐frequency and ultra‐robust rotational TENG is reported that is composed of a built‐in traction rope structure and capable of transforming from contact mode to non‐contact mode automatically as driven by the centrifugal force. With optimizing the fixed x and y position on slider and center shaft, respectively, the mode transition threshold speed can be reduced to 225 rpm. Additionally, the automatic working mode transition TENG exhibits excellent electrical stability, which can maintain 90% electric output after over 24 h of continuous operation, while the contact and non‐contact mode TENGs only retain 30% and 2% output, respectively. The high stability and large output density ensure its usage in the fast and effective charging of commercial capacitors or electronics. This work provides a prospective strategy for rotational TENGs to extend the frequency operation region and mechanical durability for practical applications.     

A Soft and Robust Spring Based Triboelectric Nanogenerator for Harvesting Arbitrary Directional Vibration Energy and Self‐Powered Vibration Sensing

Vibration is a common mechanical phenomenon and possesses mechanical energy in ambient environment, which can serve as a sustainable source of power for equipment and devices if it can be effectively collected. In the present work, a novel soft and robust triboelectric nanogenerator (TENG) made of a silicone rubber‐spring helical structure with nanocomposite‐based elastomeric electrodes is proposed. Such a spring based TENG (S‐TENG) structure operates in the contact‐separation mode upon vibrating and can effectively convert mechanical energy from ambient excitation into electrical energy. The two fundamental vibration modes resulting from the vertical and horizontal excitation are analyzed theoretically, numerically, and experimentally. Under the resonant states of the S‐TENG, its peak power density is found to be 240 and 45 mW m^?2 with an external load of 10 MΩ and an acceleration amplitude of 23 m s^?2. Additionally, the dependence of the S‐TENG's output signal on the ambient excitation can be used as a prime self‐powered active vibration sensor that can be applied to monitor the acceleration and frequency of the ambient excitation. Therefore, the newly designed S‐TENG has a great potential in harvesting arbitrary directional vibration energy and serving as a self‐powered vibration sensor.     

Environmentally Friendly Hydrogel‐Based Triboelectric Nanogenerators for Versatile Energy Harvesting and Self‐Powered Sensors

Triboelectric nanogenerators (TENGs), as a promising energy harvesting technology, have been rapidly developed in recent years. However, the research based on fully flexible and environmentally friendly TENGs is still limited. Herein, for the first time, a hydrogel‐based triboelectric nanogenerator (Hydrogel‐TENG) with high flexibility, recyclability, and environmental friendliness simultaneously has been demonstrated. The standard Hydrogel‐TENG can generate a maximum output power of 2 mW at a load resistance of 10 MΩ. The tube‐shaped Hydrogel‐TENG can harvest mechanical energy from various human motions, including bending, twisting, and stretching. Furthermore, the system can serve as self‐powered sensors to detect the human motions. Additionally, the utilized Polyvinyl Alcohol hydrogel employed in this study is recyclable to benefit for fabricating the renewable TENG. The open‐circuit voltage of renewed hydrogel‐TENG can reach up to 92% of the pristine output voltage. This research will pave a potential approach for the development of flexible energy sources and self‐powered motion sensors in environmentally friendly way.