Highly-sensitive, broad-range, and highly-dynamic MXene pressure sensors with multi-level nano-microstructures for healthcare and soft robots applications

Flexible pressure sensors are urgently needed in the fast-growing field of intelligent robots and human healthcare. However, most current pressure sensors can rarely achieve high sensitivity and dynamic behavior within a broad detection range, which greatly hinders their practical application. Herein, we develop a highly-sensitive, wide-range, and highly-dynamic MXene piezoresistive pressure sensor by constructing a multi-level nano-micro (MLNM) sensing structure. The unique structure was formed by combining the accordion-like layered nano-structures of MXene nanosheets and the abundant micro-protrusions transferred from sandpapers. It can dramatically increase the structure compressibility, the interlayer contact area, and thus resistance variations during compression, resulting in a synergistic enhancement in sensitivity, detection range, and dynamic performance. A fully solution-processable process based on sandpaper casting and oxygen plasma treatment enabled tough interface bonding was developed for low-cost and large-area fabrication. As a result, a high sensitivity of 3.94 kPa−1, a broad range of 0–117.5 kPa, rapid response and relaxation times of 70 ms and 84 ms, and long-term stability of > 7500 cyclic compression were obtained, which exhibited significant enhancement in comprehensive performance compared to previous reports. Successful monitoring of diverse human physiological signals and robot movements underscores the considerable practical utility of our MXene-based sensors.