Triboelectric nanogenerators across length scales: linking materials, multiscale modelling and applications
Triboelectric nanogenerators (TENGs) convert low-frequency mechanical energy into electricity and enable self-powered sensing. Their performance depends on interactions among material properties, surface morphology, contact mechanics, charge generation and external circuits. This review examines these interactions across length scales to assess how material and interface descriptions support predictive device design. Polymeric, inorganic, composite and natural materials are discussed in relation to charge generation and retention, mechanical compliance, durability and application requirements. Modelling approaches span molecular dynamics and first-principles calculations, rough-surface contact mechanics, device-scale electrostatics and equivalent circuits. Their capabilities are assessed through the inputs they require, the quantities they predict and the experimental evidence used for validation. Particular attention is given to prescribed surface charge density, idealised geometries and nominal contact-area assumptions, which constrain predictions under realistic loading conditions. Applications are organised by macroscale, milliscale and microscale device dimensions to examine requirements for materials, architecture and integration. The review identifies evolving real contact area and contact-dependent charge generation and decay as critical links between interfacial behaviour and electrical output. A staged validation strategy is proposed for contact mechanics, electrostatics and circuit response, with independent testing beyond calibration conditions. These priorities guide the development of multiscale models and reliable TENG systems.