Emerging DC-Generating TENG Mechanisms and Their IoT Applications

Direct-current triboelectric nanogenerator (DC-TENG) has emerged as a promising solution to power the rapidly expanding Internet of Things (IoT), by converting ambient mechanical energy directly into direct current (DC) output that is easier to store and manage than the alternating current (AC) signals of conventional TENGs. This review first introduces contact-electrification-based TENG fundamentals and maps how combinations with electrostatic induction, combined with various factors, lead to whether the output is AC, pulsed DC, or constant DC. Building on this foundation, emerging DC-generation mechanisms are organized into six classes: air-discharge dielectric breakdown, delay-switch and mechanical rectification, iontronic rectification, tribovoltaic junction, conductive dielectric, and ionic-dynamics/electrode-polarization effects. Their structural mechanism and their output relationships are clarified. Representative IoT applications domains of DC-TENGs are then highlighted, including human motion monitoring and wearable, smart agriculture and environmental monitoring, corrosion and cathodic protection, and electrochemical hydrogen generation, with emphasis on how DC characteristics simplify power management and enable self-powered sensing and communication. Finally, key challenges in materials, interfaces, device architecture, system integration, and standardization are summarized, and an outlook is provided on hybrid DC harvesters and co-designed electronics that could push DC-TENGs towards practical, large-scale IoT development.