Tough, conductive hydrogels based on gelatin and oxidized sodium carboxymethyl cellulose as flexible sensors

Natural polymer-based hydrogels have been wildly used in electronic skin, health monitoring and human motion sensing. However, the construction of hydrogel with excellent mechanical strength and electrical conductivity totally using natural polymers still faces many challenges. In this paper, gelatin and oxidized sodium carboxymethylcellulose were used to synthesize a double-network hydrogel through the dynamic Schiff base bonds. Then, the mechanical strength of the hydrogel was further enhanced by immersing in ammonium sulfate solution based on Hofmeister effect between gelatin and salt. Finally, the gelatin/oxidized sodium carboxymethylcellulose hydrogel exhibited high tensile properties (614 %), tensile fracture strength (2.6 MPa), excellent compressive fracture strength (64 MPa) and compressive toughness (4.28 MJ/m3). Also, the electrical conductivity reached 3.94 S/m. The hydrogel after salt soaked was fabricated as strain sensors, which could accurately monitor the movement of many joints in the human body, such as fingers, wrists, elbows, neck and throat. Therefore, the designed hydrogel fully originated from natural polymers has great application potentials in motion detection and information recording.