Polyimide Nanofiber-Reinforced Ti₃C₂T_x Aerogel with “Lamella-Pillar” Microporosity for High-Performance Piezoresistive Strain Sensing and Electromagnetic Wave Absorption

Assembling two-dimensional MXenes into 3D macroscopic structures is an applicable method to give full play to its excellent electrical and mechanical properties toward multi-functionality. Considering the weak interfacial interaction and poor gelation ability of MXenes, short polyimide nanofibers (PINFs) are utilized as cross-linking and supporting building blocks in this work to construct a lightweight, robust, and elastic PINF/Ti3C2Tx MXene composite aerogel (PINF/MA) via a simple synergistic assembly strategy. Taking advantage of its unique 3D “lamella-pillar” microporous architecture, the designed PINF/MA composite aerogel exhibits excellent piezoresistive sensing performance in terms of a wide pressure range of 0–8 kPa (50% strain), a high piezoresistive sensitivity of 22.32 kPa–1, an ultra-low detection limit of 0.1% strain, and great compression/rebound stability (signal remained stable after 1500 cycles). These remarkable piezoresistive sensing properties enable the PINF/MA with intriguing capability to detect small and large human activities in real time (wrist and finger bending, pulse, and vocal cord vibration). More interestingly, the parallelly aligned leaf vein-like lamellae also empower the PINF/MA with prominent wave absorption performance [RLmin is −40.45 dB at 15.19 GHz, with an effective absorption bandwidth of 5.66 GHz (12.34–18 GHz)], making the multi-functional PINF/MA composite aerogels promising candidates for wearable strain sensors and microwave absorbers.