Fire-retardant and self-extinguishing TENG under the sole. (a) The fabrication process of a hybrid carbon aerogel with functionalized nanofibers/nanosheets. (b) Schematic diagram of a single-electrode mode of FRTENG. (c) Short circuit current density comparison before and after burning. Inset: shows the flammability test of the FRTENG in 90 s. (d) The image showing FRTENG integrated onto the firefighter’s sole. (e) Temporal changes of the vector sum during the various movements of the firefighter. Reproduced with permission from [174
]. Copyright Elsevier, 2019.