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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.

For new renewable clean energy, triboelectric nanogenerators (TENGs) have shown great potential in response to the world energy crisis. Nevertheless, the alternating-current signal generated by a TENG needs to be converted into a direct-current signal to be effective in applications. Therefore, a power management circuit, comprising a clamp rectifier circuit and a mechanical switch, is proposed for the conversion and produces a signal having a low ripple coefficient. The power management circuit adopts a clamp circuit as the rectifier circuit to increase the rectified voltage, and reduces the loss resulted from the components by reducing the use of discrete components; the electronic switch in the buck regulator circuit is replaced with a mechanical switch to reduce cost and complexity. In a series of experiments, this power management circuit displayed a stable output voltage with a ripple voltage of 0.07 V, crest factor of 1.01, and ripple coefficient of 2.2%. The TENG provides a feasible method to generate stable electric energy and to supply power to low-consumption electronic devices.

Mechanical motion sensing and monitoring is an important component in the field of industrial automation. Rotary motion is one of the most basic forms of mechanical motion, so it is of great significance for the development of the entire industry to realize rotary motion state monitoring. In this paper, a triboelectric rotary motion sensor (TRMS) with variable amplitude differential hybrid electrodes is proposed, and an integrated monitoring system (IMS) is designed to realize real-time monitoring of industrial-grade rotary motion state. First, the operating principle and monitoring characteristics are studied. The experiment results indicate that the TRMS can achieve rotation speed measurement in the range of 10–1000 rpm with good linearity, and the error rate of rotation speed is less than 0.8%. Besides, the TRMS has an angle monitoring range of 360° and its resolution is 1.5° in bidirectional rotation. Finally, the applications of the designed TRMS and IMS prove the feasibility of self-powered rotary motion monitoring. This work further promotes the development of triboelectric sensors (TESs) in industrial application.

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.

Air velocity of coal mine ventilation is an important consideration that may cause serious damage. This paper proposes a simple, low cost and effective air velocity monitor (AVM) for coal mine ventilation. The AVM uses the lock-in characteristic of vortex-induced vibration (VIV) to sense the air velocity. Amplitude of the VIV is converted into frequency signal of a vortex-induced triboelectric nanogenerator (VI-TENG) to improve the durability. Structure of the AVM are designed, and parameters of the AVM are optimized with experiments. For the upper and lower air velocity thresholds of 3.1 and 3.6 m/s, the optimized flexible beam length, slider weight, electrode space and electrode width are 42.5 mm, 0.4 g, 0.2 mm and 0.5 mm, respectively. Experiments also show that the output frequency of the VI-TENG could represent the amplitude of VIV well with the correlation coefficient of 0.93. Durability test demonstrates that the AVM generates stable output frequency in 120,000 cycles. A prototype and its controller are fabricated. Wind tunnel tests of this prototype show that it can give alarm when the gas velocity goes above the upper threshold or below the lower threshold. The proposed AVM could be a good solution for simple and effective coal mine ventilation alarm.

Synthetic jets, generated through the periodic suction and ejection of fluid without net mass addition, offer distinct benefits, such as compactness, ease of integration, and independence from external fluid sources. These characteristics make them well-suited for flow control and convective heat transfer applications. However, conventional single-actuator configurations are constrained by limited jet formation, narrow surface coverage, and diminished effectiveness in the far field. This review critically evaluates the key limitations and explores four advanced configurations developed to mitigate them: dual-cavity synthetic jets, single-actuator multi-orifice jets, coaxial synthetic jets, and synthetic jet arrays. Dual-cavity synthetic jets enhance volume flow rate and surface coverage by generating multiple vortices and enabling jet vectoring, though they remain constrained by downstream vortex diffusion. Single-actuator multi-orifice designs enhance near-field heat transfer through multiple interacting vortices, yet far-field performance remains an issue. Coaxial synthetic jets improve vortex dynamics and overall performance but face challenges at high Reynolds numbers. Synthetic jet arrays with independently controlled actuators offer the greatest potential, enabling jet vectoring and focusing to enhance entrainment, expand spanwise coverage, and improve far-field performance. By examining key limitations and technological advances, this review lays the foundation for expanded use of synthetic jets in practical engineering applications.

By combining the effects of contact electrification and electrostatic induction, triboelectric nanogenerators (TENGs) can effectively convert mechanical energy into electric power or signals. Over the past decade, TENG development has progressed rapidly, from fundamental scientific understanding to advanced technologies and applications. This Primer gives a brief overview of TENGs, including the mechanisms of contact electrification and electrodynamics, applications, future opportunities and limitations. As an interdisciplinary field, advances are expected in both theoretical and experimental aspects of TENGs. For example, technologies based on Maxwell’s equations for a mechano-driven, slow-moving system can be coupled with a theoretical understanding of physical laws and concepts. From this, general simulation models can be established and corresponding experiments designed to optimize TENGs for a range of applications.Triboelectric nanogenerators (TENGs) convert mechanical energy into electric power by combining contact electrification and electrostatic induction. This Primer introduces the theoretical background of TENGs, gives an overview of fabrication methods and discusses how they can be applied as energy harvesting devices and self-powered systems.

Iontronics presents a transformative paradigm for energy and information processing via ions as active charge carriers. Here, triboiontronics is introduced, a novel strategy leveraging contact electrification to achieve dynamic regulation of electrical double layers. Inspired by signaling mechanisms of biological neural systems, triboiontronics enables enhanced ionic-electronic coupling without external power input, offering a material-independent and self-powered pathway for programmable interfacial behavior, underscoring its promise for post-Moore, energy-autonomous information technologies.

Soft, low‐cost, high‐performance generators are highly desirable for harvesting ambient low frequency mechanical energy. Here, a dielectric elastomer nanogenerator (DENG) is reported, which consists of a dielectric elastomer capacitor, an electret electrostatic voltage source, and a charge pump circuit. Under biaxial stretching, DENG can convert tensile mechanical energy into electrical power without any external power supply. Different from traditional DEG with the charge outward transfer in direct current (DC), the DENG works based on shuttle movement of internal charges in an alternating current (AC). Through alternating current (AC) method, the charge density of the DENG can reach 26 mC m−2 per mechanical cycle, as well as energy density of up to 140 mJ g−1. Due to the all‐solid‐state structure without air gap, the DENG is capable of working stably under different ambient humidity (20 RH%–100 RH%). To demonstrate the applications, a water wave harvester based on the DENG is constructed. The integrated device powers a sensing communication module for self‐powered remote weather monitoring, showing the potential application in ocean wave energy harvesting. An optimized approach toward high output performance for the dielectric elastomer generator without the need for external power supply. Based on the alternating model, the maximum charge density and the maximum energy density can reach 26 mC m−2 and 140 mJ g−1 per mechanical cycle. Due to all‐solid‐state structure, the generator is capable of working stably under high ambient humidity.

Droplet microfluidics is a rapidly evolving technology enabling precise control and manipulation of small-volume droplets, typically ranging from picoliters to nanoliters, offering important potential for biomedical applications. By generating highly uniform droplets with size variation below 5% and at high frequencies exceeding 10,000 droplets per second using techniques such as flow focusing, this approach facilitates high-throughput experimentation with minimal reagent consumption. These features make droplet microfluidics invaluable for single-cell analysis, drug screening, and disease diagnostics. Recent advancements in integrating droplet microfluidics with biological and clinical workflows have expanded possibilities for personalized medicine, early disease detection, and high-resolution cellular assays. This review provides an overview of recent progress in droplet microfluidics, focusing on key techniques for droplet generation, manipulation, and detection. It explores their applications in cutting-edge biomedical research, including single-cell analysis, 3-dimensional cell culture, drug development, and cancer research. Additionally, we discuss current challenges, such as improving reproducibility, scalability, and system integration, and outline promising future directions to fully realize the potential of droplet microfluidics in biomedicine.