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/Ti3C2T
x
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.