Chemically Engineered Hydroxyl-terminated Polybutadiene Yields Stable and High-strain Intrinsically Conductive Polyurethane Piezoresistive Sensors

The development of intrinsically conductive piezoresistive sensors with high strain tolerance has garnered significant interest. While elastomeric polymers exhibit excellent strain capabilities, their utility in sensing applications has been limited by inherent challenges such as high electrical resistivity, poor aging resistance, and interfacial incompatibility. To address these limitations, hydroxyl-terminated polybutadiene (HTPB)-based polyurethane was chemically modified with acetylferrocene-polyaniline conductive moieties to enhance charge transport properties. Remarkably, this covalent functionalization endowed the resulting ferrocene-polyaniline hybrid polyurethane (FPHP) with a conductivity of 2.33 nA at 1 V bias while preserving piezoresistive functionality. The FPHP demonstrated exceptional mechanical-electrical performance, achieving 254% elongation at break with strain-dependent gauge factors of 7.28 (0%–12.5% strain, R²=0.9504) and 19.66 (12.5%–35.0% strain, R²=0.9929). Further characterization revealed a rapid 0.60 s response time and stability over 3500 strain-release cycles at compression strain, underscoring its durability under repetitive loading. The FPHP sensor was capable of monitoring various human movements and recognizing writing signals. These advances establish a materials design paradigm for fabricating flexible sensors that synergistically integrate high deformability, tunable sensitivity, and robust operational stability, positioning FPHP as a promising candidate for next-generation wearable electronics and soft robotics.