Blowing up Ti₃C₂T_XMXene membrane for robust sound detection

Flexible pressure sensors have attracted great attention in health monitoring, human-machine interface, and soft robotics because of their simple device structure and easy to read signals. Two-dimensional (2D) materials (e.g., MXene) are promising candidates for constructing flexible pressure sensors due to their high conductivity and solution-based processability. Typically, during filtration, micrometer-sized MXene nanosheets are assembled into a thin membrane with plenty of wrinkles and folds in order to minimize the total energy. Herein, by taking advantage of this phenomenon, hydrazine hydrate is employed as a foaming agent to blow up the wrinkles and folds of MXene nanosheets in the membrane by gas species generated from the redox reactions, forming a porous foam. The as-prepared pressure sensor shows high sensitivity for a wide linear range (102.89 kPa-1 for 0-0.5 kPa and 2.86 kPa-1 for 2-10 kPa), low detection limit (1 Pa), fast response time (132 ms), and excellent durability (over 5000 cycles). As a detector, the MXene sensor can not only identify different sound signals and sound attributes by monitoring the vocal cord vibration but also distinguish various natural sounds transmitted through the air pressure waves caused by the sound transmission.