Self‐Assembled Magnetic Nanoparticles on Ag Nanowires and Polyurethane Composites for Sensitive and Flexible Piezo‐Resistive Sensors

ABSTRACT Flexible strain sensors face persistent challenges, including achieving high sensitivity, mechanical durability, and reliable performance under low pressures. To address these issues, we developed a conductive polymer nanocomposite composed of magnetic (Fe 3 O 4 ) nanoparticles assembled on silver nanowires (Fe 3 O 4 @Ag NWs) embedded in a thermoplastic polyurethane (TPU) matrix. TPU provides mechanical flexibility, while polyvinylpyrrolidone (PVP) assists the magnetic self‐assembly of Fe 3 O 4 nanoparticles onto Ag NWs, forming a highly interconnected network. When used as a piezoresistive sensor, the material shows a ∼60% resistance change at 8 kPa, six times higher than its non‐aligned counterpart, and excellent sensing response even at low pressures (0.2 kPa). This enhanced sensitivity is attributed to nanoparticle alignment and improved interfacial interactions, which increase conductive pathway density and enable efficient stress transfer. These results demonstrate the potential of this nanocomposite for next‐generation flexible, wearable, and ultrasensitive electronic and biomedical sensing applications.