Enhanced Sensing Behavior of Polyimide‐Based Flexible Piezoresistive Sensor via Synergistic Effect of Binary Carbon Materials

Foam‐based flexible pressure sensors have garnered considerable interest due to their low cost, light weight, high sensitivity, and flexibility. However, conventional foams tend to soften or become brittle under extreme temperatures, and their single‐system conductive networks limit pressure‐sensitive performance enhancement. Herein, reduced graphene oxide‐carbon black (rGO‐CB)‐coated polyimide (PI) composite sponges were prepared via hydrothermal self‐assembly and freeze‐drying using thermally stable PI sponges. The zero‐dimensional CB nanoparticles function as conductive bridges embedded in two‐dimensional rGO interlayers, constructing a point‐to‐plane coupled binary carbon structure that forms a three‐dimensional conductive network with a significant synergistic effect. The maximum conductivity reaches 2.55 × 10 −3 S m −1 , which is 4.17 and 1.8 × 10 5 times those of the pure rGO/PI and CB/PI composite sponges, respectively. The sensor exhibits a sensitivity of 0.875 kPa −1 within the 0–1 kPa range, which is 2.13 times that of the single rGO/PI sponge, and shows good cycle stability after 1000 compressions. Furthermore, the sensor effectively retains its functionality at room temperature after 6 h treatments at 450 and −196 °C, with its sensitivity in the 0–2 kPa range reaching 135.6% and preserving 88.7% of the initial value, respectively. This provides a reference for flexible sensors in extreme environments.