Boosting Piezoresistive Sensitivity of MXene/rGO Foam-Based Pressure Sensors by Flash Instantaneous Radiation

For pressure sensors, high sensitivity and broad effective sensing range are often incompatible. To balance the relationship between them, herein, a flexible pressure sensor employing 3-D porous MXene/reduced graphene oxide (MXene/rGO) hybrid foam as piezoresistive sensing material is developed by an efficient hydrothermal synthesis and a novel reduction method of flash instantaneous irradiation. Compared with conventional reduction methods, this instantaneous reduction process can effectively maintain MXene nanoflakes in tightly interconnected rGO sheets, resulting in robust mechanical elasticity and high conductivity of the proposed MXene/rGO hybrid foam. On account of the 3-D porous skeleton structure of MXene/rGO hybrid foam, the proposed pressure sensor presents a high sensitivity up to 3.75 kPa−1, a broad sensing range from 0 to 28 kPa, an ultralow detectable limit down to 1.5 Pa, rapid dynamic response/recovery times with 20/40 ms, a low hysteresis of 2.95%, as well as a strong stability for over 2000 Hz. Notably, the flexible pressure sensor possesses the superior function of precisely detecting some subtle human activities (pulse, vocalization, breathing, etc.) and large joints (knee, finger, elbow, wrist, etc.) movements in real time. Besides, a matrix pressure array of $4\times $ 4 pixels has been exploited for multipoint recognition.