Conductive hydrogel as stress‐strain sensor for human motion monitoring

Abstract Hydrogel‐based stress‐strain sensors have attracted immense attention recently for developing wearable electronic devices and health‐monitoring systems owing to their intrinsic soft characteristics and flexible nature. Developing hydrogel that has high conductivity, better mechanical performance, and elasticity is necessary for better analysis or getting accurate measurement data. Hence, this study focuses on the development of novel conductive hydrogels with enhanced mechanical, swelling, and sensing properties targeting the advancement of stress‐strain sensitive hydrogel sensors. Polyvinyl alcohol (PVA) and citric acid (CA) have been used to prepare esterified PVA/CA hydrogels while using a simple one‐pot method followed by doping with a conductive polymer (polyaniline, PANI). The resultant PVA/CA/PANI hydrogel displayed a high water uptake capacity of ∼4200%, a high mechanical strain of 700%, high puncture resistance, large durability, and a fast response time when applied as soft human‐motion sensors in real‐time measurement of large‐scale and subtle human physiological stress activities (i.e., joint motions in the forefinger, elbow, wrist, and neck). The high strain sensitivity and ultrahigh stretchability of hydrogel sensors allow them to detect small mechanical changes caused by human movement showing their great potential for hydrogel‐based sensor device fabrication.