Zhong Lin Wang’s research while affiliated with Beijing Jiaotong University and other places

Triboelectric nanogenerators (TENGs) efficiently convert mechanical energy into electricity, offering unique advantages for powering wearable electronics. Key objectives for wearable TENGs include flexibility, and high power density output. Liquid metals (LMs) are emerging as a category of functional materials with both metallic and liquid properties at room temperature, which opens up broader opportunities for TENG applications. Herein, a concept is proposed for constructing a fully flexible triboelectric nanogenerator array for mechanical energy harvesting by using LMs. The LMs layers are embedded in a porous polytetrafluoroethylene (p‐PTFE) film, resulting in a series of parallel friction interface arrays. The strong electronegativity of PTFE and the high electronic activity of liquid metals are explored, and the interface at the solid‐liquid‐gas three‐phase junction is constructed to facilitate the energy conversion. Using mechanical triggering, the direct current pulse is generated and amplified at the solid‐liquid interface, resulting in an open‐circuit voltage (Voc) of 1080 V and a power density (Pmax) of 12.44 W m⁻². Furthermore, Voc generated by the device in the contact‐separation mode amounted to 1690 V under ultrasonic (40 kHz) excitation. Consequently, this finding is anticipated to offer new opportunities in applications such as flexible electronics, mechanical energy conversion, and human‐machine interaction interfaces.

Roadbed tribological energy (RTE) is a promising recoverable resource with an estimated potential on the terawatt scale, generated annually by the interaction between tires and road surfaces. However, RTE remains underutilized due to the lack of effective energy harvesting technologies that can address its high-entropy characteristics. Here, we present a revolutionary harvester formed by a freestanding layer triboelectric nanogenerator array embedded in the road. The harvester effectively converts low-grade vibratory RTE into electrical energy. It demonstrates the potential to achieve a peak power of 16.409 milliwatts and an average power of 2.2 milliwatts from a compact 78–square centimeter road area under a single tire impact, with a triboelectric conversion efficiency of 11.723%. In addition, we developed a self-powered intelligent and connected transportation system (SP-ICTS), integrating a five-in-one harvesting array. Experimental findings show that the system can meet the SP-ICTS’s electricity requirements along a 1-kilometer segment with a 50-meter harvester.

Ulnar nerve injuries often lead to muscle atrophy and reduced hand function, necessitating precise monitoring and effective rehabilitation strategies. Current grip strength measurement tools rely on rigid mechanical equipment, which is inconvenient and requires frequent calibration. To address this, a muscle atrophy evaluation and rehabilitation system (MUERS) is presented, featuring a highly sensitive rare earth oxide‐enhanced triboelectric sensor (RETS). Utilizing the unique electrochemical properties of rare earth oxides, RETS demonstrates a linear voltage‐force response in the range of 8–80 kPa, with a maximum linear error of 1.5%. Integrated with a multi‐channel STM32 signal collector, RETS enables real‐time grip strength monitoring across all five fingers. Combining sensor output with an SVM algorithm, the system achieves 98.61% accuracy in identifying finger grip strength injuries and classifies damage into three levels with an average accuracy of 96.67%. MUERS evaluates rehabilitation progress by scoring grip strength and providing feedback to clinicians. Over a four‐week cycle, it consistently captures improvements in muscle recovery, aiding individualized rehabilitation plans. This system offers fine‐grained assessment capabilities for diagnosing and monitoring nerve injury‐induced muscle atrophy, paving the way for advanced biomedical sensing and personalized rehabilitation.

Hydrogel-based iontronics have emerged as key enablers for sustainable energy harvesting and bio-inspired sensing, with applications spanning human–machine interfaces, brain–computer interfaces, and neuromorphic computing. Central to their operation is precise modulation of the electrical double layer (EDL) at hydrogel interfaces, which governs ionic rectification, a critical function for efficient iontronic performance. This review systematically examines EDL modulation strategies for achieving ionic rectification in hydrogel systems, classifying them into four fundamental mechanisms: (1) EDL formation on charged polymer chains in polyelectrolyte hydrogels; (2) nanopore-confined EDL enhanced by hydrogel modification; (3) EDL at hydrogel-based p–n junctions; and (4) asymmetric EDL at hydrogel/electrode interfaces. Representative studies highlighting breakthrough applications of these mechanisms are discussed, alongside an outlook on the future of EDL engineering in hydrogel-based iontronics, emphasizing both opportunities and challenges in optimizing performance.

Using water droplets to generate electricity is an attractive approach for addressing the energy crisis. However, achieving high charge transfer and power output in such systems remains a major challenge. Here, a tribovoltaic nanogenerator (TVNG) is developed based on a specially designed Schottky metal‐semiconductor‐metal (MSM) structure. This device is capable of efficiently converting the kinetic energy of water droplets into electricity. To improve performance, a patterned interface layer between the metal and semiconductor is introduced, which helps guide charge flow and control surface conductivity. Upon droplet impact, the mechanical friction between the liquid and the surface generates a potential that activates charge transport across the Schottky barrier. This breaks the equilibrium state and enhances carrier movement. As a result, the device achieves a record‐high charge output of 25500 nC from a single droplet, along with an output energy of 5.8 × 10⁻⁶ J. To showcase scalability, a TVNG module with 60 cells on a 3‐inch wafer delivers milliamp‐level current and charges a 220 µF capacitor to 0.6 V within 2 s. The effects of processing, materials, structure, and droplet properties are studied to guide the future design of high‐efficiency Schottky MSM‐based TVNG.

Real‐time monitoring of water level and flow velocity is essential for reflecting hydrodynamic properties, serving as a core component of intelligent hydrological monitoring systems. However, the measurement accuracy and anti‐interference capabilities of existing sensing methods limit their practical applications. Here, a flapping‐wing water level‐velocity method (FWVM)is proposed, which combines the flapping‐wing motion with the triboelectric nanogenerator (TENG). Through the decoupling analysis of the TENG characteristic signal reflected by the flapping wing motion, the information of water level and flow velocity is extracted. Based on this method, a self‐sustaining flapping wing TENG (FW‐TENG) with a water level resolution of 1 mm is established. The accuracy and stability of FW‐TENG are improved through optimization of the wing shape and the magnetic drive design. Furthermore, a dual‐function monitoring system has been developed for real‐time in situ monitoring and early warning of water level and flow velocity. Compared with a commercial sensor, the error rates of maximum water level and flow velocity are below 0.45% and 2%, respectively. This research provides an approach for the development of underwater sensors and holds great potential for widespread application in hydrological monitoring.

The well-known and celebrated first-primer classical analysis of a one-dimensional inversion-asymmetric assembly of electric point charges interconnected by mechanical springs shows that the system is piezoelectric and characterized by a parameter-dependent but constant piezoelectric coefficient d defined as the ratio between the change in system length and the change in electric field. The former system is the simplest system displaying the phenomenon of piezoelectricity. We demonstrate that a quantum-mechanical analysis of the Hamiltonian for the same system of electric point charges and mechanical springs leads to a piezoelectric constant that depends not only on the system parameters but also on the eigenstate. Hence, the piezoelectric constant, determined as the ratio between the change in the expectation value of the system length and the change in the applied electric field, is quantized. It is demonstrated analytically and numerically, which is a necessary condition, that the quantized piezoelectric constant vanishes if the system Hamiltonian is inversion symmetric. Published by the American Physical Society 2025