Waterproof Flexible Pressure Sensors Based on Electrostatic Self-Assembled MXene/NH2-CNTs for Motion Monitoring and Electronic Skin

Flexible wearable sensors to monitor human movement and for electronic skins must exhibit high sensitivity, a wide detection range, and waterproof characteristics. This work reports a flexible, highly sensitive, and waterproof sponge pressure sensor (SMCM). The sensor is made by assembling SiO₂ (S), MXene (M), and NH₂-CNTs (C) on the backbone of melamine sponge (M). The SMCM sensor exhibits excellent sensitivity (10.8 kPa^-1), an ultra-short response/recovery time (40 ms/60 ms), a wide detection range (30 kPa), and an extremely low detection limit (4.6 Pa). Benefiting from layer-by-layer self-assembly, the sensor still exhibits excellent stability after 5000 cycles. In addition, the SMCM sensor also has excellent waterproof performance (a water contact angle of 142°), enabling it to operate unaffectedly under wet conditions. The SMCM sensor can accurately detect small body movements such as pulse and swallowing while also accurately detecting finger and elbow movements. In addition, the sensor can be designed as an array to construct an electronic skin for detecting the magnitude and distribution of external pressure. This work holds great application potential in next-generation electronic skin, fitness detection, and flexible pressure sensors.