A Wearable Strain Sensor Based on Electroconductive Hydrogel Composites for Human Motion Detection

Abstract Hydrogels are becoming the default platform for flexible electronic applications—specifically, strain sensors. But the simultaneous realization of compliance, robustness, and strain sensitivity required, using environmentally friendly materials, remains challenging. Here a series of poly(vinyl alcohol) (PVA)‐based biocomposite hydrogels, comprising variable quantities of nanocellulose and sodium alginate formed by freeze/thaw cycling, is reported. The results indicate that a hybrid hydrogel is prepared via the incorporation of conductive polypyrrole/bacterial nanocellulose composite material into the optimized PVA‐based hydrogel matrix (yield strength = 6.0 MPa, elastic modulus = 2.4 MPa, stretchability >384%). The resulting hybrid material exhibits remarkable toughness, nonlinear conformability, and piezoresistivity and demonstrates good strain sensitivity over a considerable range of deformation (<≈200% elongation, maximum gauge factor = 0.96). Moreover, the hybrid hydrogel is assembled into a wearable piezoresistive sensor capable of detecting large‐range human motion with high sensitivity, stability, and repeatability over a few repeated loading cycles. Thus, there is potential for the application of the conductive hybrid hydrogel in flexible electronics, such as wearable devices for health monitoring, soft robotics, and biomedical implants. Furthermore, the implementation of biocompatible polymers and renewable materials, amongst other green design principles, provides scope for the design of sustainable high performance materials.