Strong and conductive gelatin hydrogels enhanced by Hofmeister effect and genipin crosslinking for sensing applications

Abstract

There is a growing interest in the development of conductive hydrogels based on natural polymers for sensing applications due to their flexibility, versatility and environmental friendliness. However, achieving strong hydrogels capable of withstanding mechanical stress while maintaining their desirable characteristics remains a challenge. This study proposed a strategy to tailor the mechanical and electrical conductivity of gelatin hydrogels by combining genipin crosslinking with the modulation of aggregation states of gelatin chains through Hofmeister effect. The obtained conductive gelatin hydrogels exhibit high tensile strength (5.48 MPa) and compressive stress at 80 % strain (5.66 MPa), excellent stretchability (>500 %), remarkable freezing-resistant performance, and good strain sensitivity. By virtue of these outstanding properties, the hydrogels were used as strain sensors for human motion detection, demonstrating a gauge factor of 0.6 at 110–200 % tensile strain. Additionally, the hydrogel sensors demonstrate a rapid response time (<0.32 s) and can withstand cyclic tensile/compressive loads at both room temperature and −20 °C, owing to their compact and stable network structure formed by the synergistic action of Hofmeister effect and chemical crosslinking. The strain sensors based on gelatin hydrogels can detect and track human movements, indicating promising applications in the field of wearable technology.