Ionic conductive hydrogel strain sensor with high linearity and low hysteresis for human-computer interaction and intelligent infusion monitoring

Developing flexible strain sensors that simultaneously exhibit high linearity, low hysteresis, and a wide sensing range remains challenging because these properties are often mutually constrained. A simple freeze–thaw method was employed in this work to prepare an ionic conductive hydrogel from poly(vinyl alcohol) (PVA), cellulose nanofibers (CNFs), chitosan (CS), and phytic acid (PA). The hydrogel network integrates multiple noncovalent interactions, including hydrogen bonding and dynamic ionic crosslinking. CNFs serve as reinforcing nanofillers to improve stress transfer efficiency, while PA not only supplies mobile ions for ionic conduction but also interacts with protonated CS to establish reversible ionic associations. The resulting hydrogel combines good mechanical robustness with rapid structural recovery during deformation. Owing to the continuous ion-transport pathways and the homogeneous stress distribution enabled by the multicomponent network, resistance variation is primarily determined by geometric deformation rather than by the repeated disruption and reconstruction of conductive pathways. Therefore, the hydrogel sensor achieves a broad-range linear sensing behavior together with suppressed hysteresis and robust cyclic stability. The sensing capability of the hydrogel was further evaluated in an infusion-monitoring system. Variations in infusion-bag weight, tube blockage, and external disturbances could be accurately distinguished through characteristic electrical signals, enabling real-time monitoring of infusion status. This study provides a practical strategy for developing ionic conductive hydrogels that combine mechanical robustness with reliable sensing capability, while also demonstrating their promise for intelligent medical monitoring.