CNT@Ag-MXene/EG multi-layered sensing composite with long cyclic stability and corrosion resistance over a wide tensile strain range

Abstract This study addresses key challenges of long-term stability, wide range, and high sensitivity in piezoresistive strain sensors by developing a multilayer composite. A parallel circuit is constructed using carbon nanotube@silver nanoparticles-MXene (CNT@AgNPs-MXene) and expanded graphite (EG) double sensing layers, exploiting EG’s interlayer sliding and recovery capability derived from its wide layer spacing, and is integrated with a thermoplastic polyurethane (TPU) support layer. This design provides complementary current pathways, where a redundant path is offered by the other layer when one layer breaks. The resulting CNT@AgNPs-MXene/EG/TPU trilayer (double sensing layers with a TPU support) achieves stable operation over 150,000 cycles, a working range of 630% (709% mechanically), and a maximum GF of 4091.74. In comparison, the EG/TPU bilayer (single EG layer with a TPU support) is also stable for 150,000 cycles and exhibits a higher maximum GF (16083.30) but a narrower working range (245%). Consequently, each sensor holds a distinct performance edge. The bilayer excels at detecting ultra-fine motions, while the trilayer is advantageous for large-strain scenarios. Both sensors reliably monitor diverse human motions and maintain long-term stability in harsh environments (fresh water, sweat, alkaline/acidic conditions). This work provides a new strategy for high-performance, durable sensors for harsh environments.