High-Sensitivity and Wide-Range Pressure Sensing Enabled by Polyaniline-Regulated Natural Rubber Foam via In Situ Polymerization

Despite the inherent advantages of natural rubber (NR) as an ecofriendly and renewable elastomer, NR-based sensors face critical challenges, including interfacial incompatibility, discontinuous conductive networks, and sensitivity degradation under cyclic loading. Herein, we present a rational design of flexible sensing composites through in situ polymerization of polyaniline (PANI) within NR matrices combined with an impregnation strategy. Systematic characterization (FTIR, XPS, SEM-EDS, and dynamic mechanical analysis) reveals that hydrogen bonding between PANI and NR facilitates interfacial electron transfer while increasing the protonation ratio of nitrogen-containing groups by 7.2%. The optimized composite demonstrates exceptional sensing performance: ultrafast response (70 ms), broad detection range (0–60 kPa), and remarkable durability (98.7% sensitivity retention after 2,000 cycles). Mechanistic studies through in situ resistance monitoring and crack propagation analysis unveil that the pressure-responsive behavior originates from dynamic reconstruction of conductive pathways via microcrack evolution in PANI layers under compression, achieving wide-range linearity (ΔR/R0 = 0.5–89.5% corresponding to 0.1–80% strain). Practical applicability is demonstrated through real-time monitoring of human joint movements. The interfacial engineering strategy and mechanistic understanding provide universal guidelines for designing next-generation green sensor materials.