Hollow-structured MXene-PDMS composites as flexible, wearable and highly bendable sensors with wide working range

Although versatile piezoresistive pressure sensors show a great potential as human motion detection and wearable smart devices, it is still an issue to widen their working range and enhance their sensitivity. Herein, hollow-structured MXene-polydimethylsiloxane composites (MPCs) are fabricated by utilizing nickel foam as the three-dimensional substrate for dip-coating of MXene sheets followed by infiltrating of polydimethylsiloxane and etching of the nickel foam substrate. The resultant MPC performs a wide working range with bending angles of 0° to 180°, an excellent long-term reliability up to 1000 cycles under the bending angles of 15°, 30° and 150°, and a stable durability with a bending angle of 30° in a frequency range from 0.05 to 2 Hz as a bendable piezoresistive pressure sensor, which is attributed to the formation of dense conduction paths due to the interconnection of MXene sheets during the deformation of MPC. The sensor also exhibits an extremely low detection limit of 10 mg for pressure detection. Interestingly, the slippage of adjacent MXene sheets is beneficial for monitoring slight vibration of equipments and detecting subtle human motions. Thus, the MPC sensor could be applied for stereo sound and ultrasonic vibration monitoring, swallowing, facial muscle movement, and various intense motion detections, demonstrating its great potential as wearable smart devices.