The development of the Internet of Things (IoT) and artificial intelligence has accompanied the evolution of energy demand and structure in the new era, and the power sources for billions of distributed electronics and sensors have aroused worldwide interest. As an alternative energy harvesting technology, triboelectric nanogenerators (TENGs) have received remarkable attention and have shown attractive potential applications for use in micro/nano power sources, self-powered sensors, high-voltage power sources and blue energy due to their advantages of small size, light weight, flexibility, low cost, and high efficiency at low frequency. In this review, we discuss high-performance TENGs from the perspectives of triboelectric charge density, output voltage, energy density and corresponding quantification methods. Among these topics, the limitations, optimization methods and techniques, and potential directions to challenge these limits are comprehensively discussed and reviewed. Finally, we discuss the emerging challenges, strategies and opportunities for research and development of high-performance TENGs.

As a widely used security device, the electronic passworded locker is designed to protect personal property and space. However, once the password is leaked to an unauthorized person, its security is lost. Here, with the assistance of triboelectric nanogenerators (TENGs), we present an intelligent electronic passworded locker (IEPL) based on unique and personalized security barriers, which can accurately extract users’ habits of entering passwords through integrated deep learning. The key of the IEPL adopts the single electrode mode of TENG that accurately recognizes the input behavior of a person based on machine learning, which serves as a reliable, unique, and unreproducible gate, with advantages of thin thickness, diversified structure, and simple preparation method. Finally, the proposed IEPL offers a reliable solution for improving the overall security of passworded lockers and extending the application of TENG-based sensors in the smart home.

The environmental micro-energy harvested by the triboelectric–electromagnetic hybrid generator (TEHG) can power sensors and Internet of Things (IoT) nodes in smart agriculture. However, the separation structure of traditional TEHG raises the complexity of form and material, which is harmful to the miniaturization of the device. Herein, a single-material-substrated triboelectric–electromagnetic hybrid generator (SMS-TEHG) based on the flexible magnets is designed to achieve the structural integration of triboelectric nanogenerator (TENG) and electromagnetic generator (EMG). The flexible magnets serve as the electropositive triboelectric materials for TENG and the magnetic materials for EMG, simplifying the structural complexity of TEHG. The open-circuit voltage (V_OC) of the TENG and EMG are 187.2 and 9.0 V at 300 rpm, respectively. After 30,000 cycles of stability testing, the V_OC of the TENG and EMG retain about 95.6% and 99.3%, respectively. Additionally, the self-powered applications driven by SMS-TEHG in intelligent greenhouse have been successfully demonstrated, such as crop light supplementation, rain monitoring, and wireless temperature and humidity sensing. This work provides a new design for TEHG and possibilities for applying TEHG and IoT in smart agriculture.

Electrochemical system with electro-Fenton reaction is an effective pathway for oxidative degradation of refractory organic pollutants for water treatment. However, the method is limited by the low catalytic efficiency and high electrical cost in practical applications. This work presents a self-powered and high-efficient electrochemical system for water treatment including pollutant degradation and bacterial inactivation, which is composed of a self-powered triboelectric nanogenerator (TENG) converting mechanical energy into electrical energy, a power management circuit integrated with a supercapacitor to store the harvesting electrical energy temporarily, and an electrochemical setup integrated with two-dimentional Co(OH)₂/Pt nanosheet as electrocatalyst. The nanocatalyst, ultrafine Pt nanoparticles (Pt NPs) loaded on Co(OH)₂ nanosheet (Co(OH)₂/Pt), is synthesized by a facile one step hydrothermal reaction without any surfactant, which can improve H₂O₂ and hydroxyl radical production via redox reaction. This self-powered electrocatalytic system is able to degrade nearly 100% of organic pollutant within 100 min, and efficiently kill bacteria. This work shows great potential to develop high-efficient and self-powered electrochemical water treatment system through integrating TENG and nanocatalyst.

To adapt to the low-velocity water flow closely related to human life, the natural energy can be efficiently harvested and used to power monitoring devices. Herein, a triboelectric soft fishtail (TE-SFT) driven by flow-induced vibration (FIV) effect is proposed based on the soft material synthesis technology. Specifically, inspired by the fishtail fin, a bluff body with the cross-section of fishtail-shaped is designed, and has a preferable vortex effect by fluid simulation. In power generation part, the triboelectric nanogenerator (TENG) is designed to act as an inertial pendulum structure by geometric method. Under the FIV effect, the TE-SFT driven by fishtail-shaped bluff body swings like a fish in the water and then brings the inertial pendulum to acquire the oscillation for harvesting energy from low-velocity water flow. The TE-SFT attains an open-circuit voltage (V_OC) of 200 V to 313 V at the flow velocities of 0.24 to 0.89 m/s. Additionally, after 30 days of water immersion, the V_OC of TE-SFT retains 96.81%. In demonstration, the TE-SFT is applied to power the temperature and humidity sensor through harvesting water flow energy. This work also provides a way for self-powered system based on the TENG and soft bionic fish in water environment.

A narrow resonance bandwidth of an energy harvesters limits its response to the wide frequency spectrum in ambient environments. This work proposes an addition of a nonlinear restoring force applied to a triboelectric nanogenerator (TENG) to tune and broaden the resonance bandwidth. This restoring force is applied by permanent magnets at both sides of the slider and two external magnets. The noncontact strategy is adopted between the slider and the grating electrodes to avoid the wear of electrodes and energy loss caused by friction. The results show that compared with the linear system, the nonlinear noncontact TENG (NN-TENG) can increase the peak current from 6.3 μA to 7.89 μA, with an increment of about 25%, increase the peak power from 650 μW to 977 μW, increasing by about 50%, and increase the bandwidth from 0.5 Hz to 7.75 Hz, increasing by about1400%. This work may enable a new strategy to boost the bandwidth and output power of TENG through nonlinear oscillators.

The theft prevention for cultural relics in museums, field excavation sites, and temporary exhibition events is of extreme importance. However, traditional anti-theft technologies such as infrared monitoring and radio frequency identification are highly costly, power-consuming, and easy to break. Here, a transparent, ultrathin, and flexible triboelectric sensor (TUFS) with a simple and low-cost method is proposed. With a thickness, weight, and transmittance of 92 μm, 0.12 g, and 89.4%, the TUFS manifests superb concealment. Benefiting from the characteristic of triboelectric nanogenerators, the TUFS responds effectively to common cultural-relic materials. Moreover, distinguished electrical responses can be obtained even for very small weights (10 g) and areas (1 cm²), proving the sensitivity and wide range of use of the TUFS. Finally, we construct a concealed cultural-relic anti-theft system that enables real-time alarming and accurate positioning of cultural relics, which is expected to strengthen the security level of the existing museum anti-theft systems.

In the era of big data and the Internet of Things, the digital information of athletes is particularly significant in sports competitions. Here, an intelligent self-powered take-off board sensor (TBS) based on triboelectric nanogenerator (TENG) with a solid-wooden substrate is provided for precise detection of athletes’ take-off status in the sport of triple-jumping, which is sufficient for triple-jumping training judgment with a high accuracy of 1 mm. Meanwhile, a foul alarm system and a distance between the athlete’s foot and take-off line (GAP) measurement system are further developed to provide take-off data for athletes and referees. The induced charges are formed by the TBS during taking-off, and then the real-time exercise data is acquired and processed via the test program. This work presents a self-powered sports sensor for intelligent sports monitoring and promotes the application of TENG-based sensors in intelligent sports.

The hydrokinetic energy of river current, as one of the essential and widespread renewable energies, is difficult to be harvested in low flow velocity and shallow water areas. In this work, a three-dimensional (3D) fully-enclosed triboelectric nanogenerator (FE-TENG) with bionic fish-like structure for harvesting hydrokinetic energy is reported, which is comprised of the triboelectric power-generation unit, bionic fish-like structure and connection unit. Through the bionic structure, the FE-TENG realizes zero head power generation in shallow water with low flow velocity. What’s more, the effect of external excitations and bionic structures on the electrical performance are systematically studied in this work. The FE-TENG can generate peak power density of 7 and 0.36 W/m³ respectively under the simulated swing state with frequency of 1.25 Hz and simulated river current with flow velocity of 0.81 m/s. In practical applications, due to the 3D fully-enclosed design, the FE-TENG immersed in water for 35 days demonstrates excellent immersion durability with undiminished electrical performance. Therefore, the work proposes an efficient method realizing zero head power generation, and provides a good candidate for long-term service in the river current.

The high-voltage power source is one of the important research directions of triboelectric nanogenerator (TENG). In this paper, a high-voltage output TENG (HVO-TENG) is proposed with direct current/alternating current (DC/AC) optimal combination method for wind energy harvesting. Through the optimal design of a direct current generation unit (DCGU) and an alternating current generation unit (ACGU), the HVO-TENG can produce DC voltage of 21.5 kV and AC voltage of 200 V, simultaneously. The HVO-TENG can continuously illuminate more than 6,000 light emitting diodes (LEDs), which is enough to drive more possible applications of TENG. Besides, this paper explored application experiments on HVO-TENG. Demonstrative experiments indicate that the high-voltage DC output is used for producing ozone, while the AC output can light up ultraviolet (UV) LEDs. The HVO-TENG can increase the ozone concentration (C) in an airtight container to 3 parts per million (ppm) after 7 h and continuously light up UV LEDs. All these demonstrations verify that the HVO-TENG has important guiding significance for designing high performance TENG.