Lightweight and Mechanically Robust MXene/Polyimide/Silver Nanowire Composite Aerogels for Flexible Piezoresistive Sensors

Two-dimensional transition-metal carbides and nitrides (MXenes) show great potential in aerogel flexible piezoresistive sensors owing to their versatile surface chemistry, high carrier mobility, outstanding metallic conductivity, and adjustable interlayer spacing under applied stress. However, the pure MXene aerogel exhibits significant plastic deformation or brittle mechanical performance due to the weak interactions between the nanosheets. Herein, a series of MXene/polyimide/silver nanowire composite aerogels with aligned lamellar microstructure are fabricated by bidirectional freezing and annealing strategies. The introduction of polyimide (PI) and silver nanowires (AgNWs) significantly improves the mechanical properties of the MXene-based aerogel. The obtained lightweight composite aerogel shows superelasticity with large reversible compressibility, excellent stability, and outstanding fatigue resistance. Moreover, owing to the highly aligned lamellar microstructure of the composite aerogel and the excellent conductivity of MXene and AgNWs, the composite aerogel exhibits great sensing performance with high sensitivity (gauge factor similar to 27.8) and ultralow detection limit (<0.6 Pa). Based on the MXene/PI/AgNW composite aerogels, a series of wearable sensor applications are demonstrated.