Flexible and highly-sensitive pressure sensor based on controllably oxidized MXene

Conductive Ti₃C₂T_x MXenes have been widely investigated for the construction of flexible and highly-sensitive pressure sensors. Although the inevitable oxidation of solution-processed MXene has been recognized, the effect of the irreversible oxidation of MXene on its electrical conductivity and sensing properties is yet to be understood. Herein, we construct a highly-sensitive and degradable piezoresistive pressure sensor by coating Ti₃C₂T_x MXene flakes with different degrees of in situ oxidation onto paper substrates using the dipping-drying method. In situ oxidation can tune the intrinsic resistance and expand the interlayer distance of MXene nanosheets. The partially oxidized MXene-based piezoresistive pressure sensor exhibits a high sensitivity of 28.43 kPa⁻¹, which is greater than those of pristine MXene, over-oxidized MXene, and state-of-the-art paper-based pressure sensors. Additionally, these sensors exhibit a short response time of 98.3 ms, good durability over 5000 measurement cycles, and a low force detection limit of 0.8 Pa. Moreover, MXene-based sensing elements are easily degraded and environmentally friendly. The MXene-based pressure sensor shows promise for practical applications in tracking body movements, sports coaching, remote health monitoring, and human–computer interactions.