Triboelectric nanogenerators for mechanical energy harvesting: principles, structures and applications

Triboelectric nanogenerators (TENGs) represent a breakthrough mechanical energy harvesting technology, leveraging contact electrification and electrostatic induction to efficiently convert ambient low-frequency mechanical energy into electricity. This review systematically outlines the fundamental principles, structural configurations, and performance-influencing factors of TENGs. Four primary working modes, namely contact-separation, lateral sliding, single-electrode, and freestanding triboelectric-layer modes are comprehensively discussed, along with advanced structural designs such as single-layer, double-layer, and multi-layer architectures for enhanced power output and adaptability. Critical factors affecting TENG performance, including material surface properties, charge transfer mechanisms, and environmental conditions (humidity, temperature, and pressure), are analyzed in detail. In addition, various applications in energy collection, self-powered sensing and biomedical equipment are listed. Finally, current challenges and future research directions are presented to guide the development of robust, high-efficiency TENGs systems toward sustainable energy solutions and widespread adoption in intelligent networks.