Efficient removal of particulate matter (PM) is the major goal for various air cleaning technologies due to its huge impact on human health. Here, a washable high-efficiency triboelectric air filter (TAF) that can be used multiple times is presented. The TAF consists of five layers of the polytetrafluoroethylene (PTFE) and nylon fabrics. Compared with traditional electrostatic precipitator, which requires a high-voltage power supply, the TAF can be charged by simply rubbing the PTFE and nylon fabrics against each other. The electrical properties of the TAF are evaluated through the periodic contacting-separating of the PTFE and nylon fabrics using a linear motor, and an open-circuit voltage of 190 V is achieved. After charging, the TAF has a removal efficiency of 84.7% for PM 0.5 , 96.0% for PM 2.5 , which are 3.22 and 1.39 times as large as the uncharged one. Most importantly, after washing several times, the removal efficiency of the TAF maintains almost the same, while the commercial face mask drops to 70% of its original efficiency. Furthermore, the removal efficiency of the PM 2.5 is very stable under high relative humidity. Therefore, the TAF is promising for fabricating a reusable and high-efficiency face mask.

It has been demonstrated that substantial electric power can be produced by a liquid-based triboelectric nanogenerator (TENG). However, the mechanisms regarding the electrification between a liquid and a solid surface remain to be extensively investigated. Here, the working mechanism of a droplet-TENG was proposed based on the study of its dynamic saturation process. Moreover, the charge-transfer mechanism at the liquid−solid interface was verified as the hybrid effects of electron transfer and ion adsorption by a simple but valid method. Thus, we proposed a model for the charge distribution at the liquid−solid interface, named Wang's hybrid layer, which involves the electron transfer, the ionization reaction, and the van der Waals force. Our work not only proves that TENG is a probe for investigating charge transfer at interface of all phases, such as solid−solid and liquid−solid, but also may have great significance to water energy harvesting and may revolutionize the traditional understanding of the liquid−solid interface used in many fields such as electrochemistry, catalysis, colloidal science, and even cell biology.

Water wave energy is a promising clean energy source, which is abundant but hard to scavenge economically. Triboelectric nanogenerator (TENG) networks provide an effective approach toward massive harvesting of water wave energy in oceans. In this work, a coupling design in TENG networks for such purposes is reported. The charge output of the rationally linked units is over 10 times of that without linkage. TENG networks of three different connecting methods are fabricated and show better performance for the ones with flexible connections. The network is based on an optimized ball-shell structured TENG unit with high responsivity to small agitations. The dynamic behavior of single and multiple TENG units is also investigated comprehensively to fully understand their performance in water. The study shows that a rational design on the linkage among the units could be an effective strategy for TENG clusters to operate collaboratively for reaching a higher performance.

As one of their major goals, researchers attempting to harvest mechanical energy efficiently have continuously sought ways to integrate mature technologies with cutting-edge designs to enhance the performances of triboelectric nanogenerators (TENGs). In this research, we introduced monolayer molybdenum-disulfide (MoS) into the friction layer of a TENG as the triboelectric electron-acceptor layer in an attempt to dramatically enhance its output performance. As a proof of the concept, we fabricated a vertical contact-separation mode TENG containing monolayer MoS as an electron-acceptor layer and found that the TENG exhibited a peak power density as large as 25.7 W/m, which is 120 times larger than that of the device without monolayer MoS. The mechanisms behind the performance enhancement, which are related to the highly efficient capture of triboelectric electrons in monolayer MoS, are discussed in detail. This study indicates that monolayer MoS can be used as a functional material for efficient energy harvesting.

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Electrowetting technique is an actuation method for manipulating position and velocity of fluids in the microchannels. By combining electrowetting technique and a freestanding mode triboelectric nanogenerator (TENG), we have designed a self-powered microfluidic transport system. In this system, a mini vehicle is fabricated by using four droplets to carry a pallet (6 mm × 8 mm), and it can transport some tiny object on the track electrodes under the drive of TENG. The motion of TENG can provide both driving power and control signal for the mini vehicle. The maximum load for this mini vehicle is 500 mg, and its highest controllable velocity can reach 1 m/s. Freestanding TENG has shown excellent capability to manipulate microfluid. Under the drive of TENG, the minimum volume of the droplet can reach 70-80 nL, while the tiny droplet can freely move on both horizontal and vertical planes. Finally, another strategy for delivering nanoparticles to the designated position has also been demonstrated. This proposed self-powered transport technique may have great applications in the field of microsolid/liquid manipulators, drug delivery systems, microrobotics, and human-machine interactions.

Making use of water wave energy at large is one of the most attractive, low-carbon, and renewable ways to generate electric power. The emergence of triboelectric nanogenerator (TENG) provides a new approach for effectively harvesting such low-frequency, irregular, and "random" energy. In this work, a TENG array consisting of spherical TENG units based on springassisted multilayered structure is devised to scavenge water wave energy. The introduction of spring structure enhances the output performance of the spherical TENG by transforming low-frequency water wave motions into high-frequency vibrations, while the multilayered structure increases the space utilization, leading to a higher output of a spherical unit. Owing to its unique structure, the output current of one spherical TENG unit could reach 120 µA, which is two orders of magnitude larger than that of previous rolling spherical TENG, and a maximum output power up to 7.96 mW is realized as triggered by the water waves. The TENG array fabricated by integrating four units is demonstrated to successfully drive dozens of light-emitting diodes and power an electronic thermometer. This study provides a new type of TENG device with improved performance toward large-scale blue energy harvesting from the water waves.

As the dominant component for precise motion measurement, angle sensors play a vital role in robotics, machine control, and personalized rehabilitation. Various forms of angle sensors have been developed and optimized over the past decades, but none of them would function without an electric power. Here, a highly sensitive triboelectric self‐powered angle sensor (SPAS) exhibiting the highest resolution (2.03 nano‐radian) after a comprehensive optimization is reported. In addition, the SPAS holds merits of light weight and thin thickness, which enables its extensive integrated applications with minimized energy consumption: a palletizing robotic arm equipped with the SPAS can precisely reproduce traditional Chinese calligraphy via angular data it collects. In addition, the SPAS can be assembled in a medicare brace to record the flexion/extension of joints, which may benefit personalized orthopedic recuperation. The SPAS paves a new approach for applications in the emerging fields of robotics, sensing, personalized medicare, and artificial intelligence.