Electrical Breakdown-Induced Tunable Piezoresistivity in Graphene/Polyimide Nanocomposites for Flexible Force Sensor Applications

Flexible force sensors based on graphene/polymer nanocomposites have attracted tremendous attention owing to their remarkable sensitivity and ease of fabrication. In the present study, nanocomposites consisting of graphene as conducting fillers in a polyimide matrix are prepared, and an electrical breakdown method is used to endow the nanocomposite with a high piezoresistivity. Electromechanical tests and theoretical models confirm that the piezoresistivity of the nanocomposite originates from the cracks in the carbonized polymers induced by electrical breakdown. The fabricated force sensor exhibits a broad working range of 0–495 kPa, ultrafast response (2.12 ms), and excellent stability (>2000 compression–release cycles). In addition, the sensitivities of the force sensor can be tuned by varying the applied current in the electrical breakdown process. Thus, the electrical breakdown method allows highly facile fabrication of piezoresistive force sensors with tunable sensitivities.