Fig. 3: Mechanism of preparation and sensing of MPP sensors.

a Schematic diagram of the preparation process of MXene/PPy in the MPP sponge sensor. b Schematic diagram of the piezoresistive sensing mechanism of the MPP sponge. SEM images of the MPP sensor at pressures of 0 kPa (c, f), 20 kPa (d, g), and 100 kPa (e, h)