FIGURE 4.

Filtration and gas sensing by respiration‐driven TENGs. A, Schematic of a TENG‐based smart mask filtering particles and its working mechanism. Inset is an SEM image of PVDF‐ESNF. B, Removal efficiencies of PVDF‐ESNF and TENG masks. C, Durability test on removal efficiency of the smart mask integrated with TENG after 30 days. Reproduced with permission: Copyright 2018, the American Chemical Society. ⁹⁷ D, Schematic illustration of a respiration‐driven TENG sensor. E, Response‐NH₃ concentrations fitting curve of the TENG. Inset is the selectivity of TENG to NH₃ and other interference gases. Reproduced with permission: Copyright 2019, Elsevier. ⁹⁸ F, A digital image of a gas‐sensing TENG. Inset is the schematic of the Alveolus‐inspired TENG. G, Selectivity of the TENG to NO₂ and other interference gases. H, Response‐NO₂ concentrations fitting curve of the TENG. Reproduced with permission: Copyright 2020, the American Chemical Society. ⁹⁹ ESNF, electrospun nanofiber film; PVDF, polyvinylidene fluoride; TENG, triboelectric nanogenerator