Piezoelectric materials were studied to fabricate NGs. (a) The e-skin based on ZnO nanowire could be driven by body motion. (b) The flexible pressure sensor is composed of ultrathin adhesive layer, flexible substrate, and PZT thin film. (c) The fabrication process of BaTiO3/PDMS-based PENG. (d) Se-PENG device could be stretched or twisted. NWs: nanowires. (e) The artificial cutaneous sensor is made from PVDF. MB: membrane; PANI: polyaniline; AL/C: aluminum foil coated with conductive carbon. (f) The flexible piezoelectric device is composed of PEDOT:PSS.