Enhanced polyvinyl alcohol ionic conductive hydrogel with feather keratin extracted via deep eutectic solvent for wearable strain sensor

The extraction of keratin from discarded feathers for the preparation of poly (vinyl alcohol) (PVA) ionic conductive hydrogels with enhanced mechanical properties shows promise for applications in green flexible electronics. Here, we first extracted feather keratin (FK) from duck feather fibers using the lactic acid/l-cysteine deep eutectic solvents. Subsequently, the composite ionic conductive hydrogel composed of FK, PVA, and CaCl2 was constructed by a one-pot freeze-thawing strategy. The introduction of FK resulted in a denser structure of the fabricated hydrogel, which significantly enhanced its mechanical properties, including high elongation at break of 639.3%, high breaking strength of 270 kPa, and durable fatigue resistance. Impressively, the hydrogel-based wearable strain sensor demonstrated high strain sensing sensitivity (GF = 1.26), wide strain detection range (5%–200%), fast response, and stable reliability, enabling it to accurately monitor and distinguish the difference in electrical signals generated by large and tiny human motions. This work provides a reliable method for the green extraction of FK and the design of high-performance PVA hydrogel-based flexible electrical devices.