Highly compressible and thermal insulative conductive MXene/PEDOT:PSS@melamine foam for promising wearable piezoresistive sensor

With the rapid development of intelligent wearable electronic devices, highly compressible porous piezoresistive sensors are in imperative demand. However, the robustness of conductive coating that affects the stability and durability of porous piezoresistive sensors still needs to be solved urgently. In this work, a flexible conductive MXene/PEDOT:PSS@Melamine foam (MPMF) piezoresistive sensor was designed and prepared by simply dip-coating it in MXene and PEDOT:PSS mixed solution. Here, foam skeleton was first treated with PDA to improve its hydrophilicity and enhance the interfacial interaction with the functional groups of MXene nanosheets. More importantly, the usage of PEDOT:PSS can fix the MXene nanosheets tightly and construct synergistic conductive network between them, obtaining stable, robust, and highly conductive coating. Based on the contact effect between the adjacent conductive skeleton, the prepared MPMF sensor displays excellent piezoresistive sensing performances, which includes a wide working range (up to 80% compression strain, 60 kPa pressure), high sensitivity (0.30 kPa−1 in the pressure range of 12–60 kPa), and stable sensing pattern over 1000 compression cycles. All these merits make the sensor capable of detecting various human motions and pressure/location distribution of different items when assembled into an electronic skin. In addition, excellent thermal insulation property under different temperature conditions was also observed for MPMF due to the existence of special porous structures, providing necessary thermal protection when served as a wearable sensor. This research provides a convenient, simple, and cost-effective method for the manufacture of high-performance porous piezoresistive sensor.