High-efficiency preparation of large-sized MXene nanosheets for flexible piezoresistive sensors with high sensitivity and wide strain range

The concurrent attainment of high sensitivity and broad response range in piezoresistive sensors remains a critical challenge. While single-layer MXene characterized by large interlayer spacing, high specific surface area, flexibility, and superior electrical conductivity—holds promise for enhancing sensor performance, conventional synthesis methods suffer from inefficient exfoliation and low yield, hindering practical applications. Herein, we propose a novel strategy to synthesize single-layer MXene nanosheets via a mixed-acid (HF/HCl) etching system with lithium chloride (LiCl) as an intercalation agent. This approach achieved remarkable exfoliation efficiency (up to 70 %) while endowing MXene with a wrinkled morphology and an expanded specific surface area. Subsequently, MXene/polyimide (MXene/PI) composite aerogels were fabricated by integrating MXene nanosheets into a PI flexible substrate, serving as pressure-sensitive materials. The composite aerogels exhibited a highly aligned lamellar microstructure, synergizing MXene’s conductivity with PI’s flexibility, thereby significantly improving both sensitivity and response range. At an optimal MXene content of 14 %, the sensor demonstrated exceptional performance: a wide response range (0–27.1 kPa) and a high sensitivity of 2.65 kPa −1 under a large applied stress of 27.1 kPa, surpassing existing counterparts. Further applications revealed the sensor’s capability in precisely detecting physiological signals (e.g, finger, wrist, and elbow movements). Additionally, the composite aerogel showcased multifunctionality, including superior thermal insulation (>90 % heat retention), efficient electromagnetic interference (EMI) shielding (45 dB at 10 GHz), and oil–water separation efficacy (>98 % for non-polar solvents). These findings highlight the material’s potential in wearable electronics, environmental remediation, and EMI shielding technologies, paving the way for next-generation multifunctional sensors.