Printed flexible/stretchable piezoresistive pressure sensor. (a) Schematic illustration of the piezoresistive transduction principle. (b) Printed stretchable tactile sensor with the multimaterial fabrication: (A) schematic of different layers of a tactile sensor; (B) 8 sequential steps of the 3D printing process [231
]. Reproduced with permission. Copyright John Wiley and Sons, 2017. (c) Direct printing of nanocomposite printable inks for piezoresistive sensor applications [232
]. Reproduced with permission. Copyright John Wiley and Sons, 2018.