Multifunctional Ionic Conductive Double-Network Hydrogel as a Long-Term Flexible Strain Sensor

Hydrogel-based sensors have attracted a lot of attention owing to their promising applications in human–machine interfaces, personal health monitoring, and soft robotics. However, there is still a great challenge in the fabrication of conductive hydrogel sensors with good mechanical strength, self-healing property, transparency, self-adhesiveness, antibacterial performance, high conductivity, and sensitivity. To meet these requirements, a multifunctional ionic conductive double-network (DN) hydrogel was prepared via in situ free-radical polymerization using a simple one-pot method based on AlCl3, acrylic acid, oxide sodium alginate, and aminated gelatin. The hydrogel network was constructed via metal coordination and Schiff base. The resultant DN hydrogel showed self-healing behavior in an ambient environment and underwater with high healing efficiency. Notably, the water environment can effectually accelerate the self-healing process of the hydrogel. Moreover, the corresponding hydrogel displayed good self-adhesiveness, transparency (over 90%), stretchability, antibacterial ability, and high conductivity and sensitivity. This hydrogel was further utilized as a sensor to monitor various human movements and object deformations in daily life. Significantly, the hydrogel that was placed in a closed environment for 10 days still possessed those performances mentioned above. Additionally, the healed hydrogel also maintained the sensing behavior. This work may enlighten future research to design fully functional hydrogel-based sensors to adapt to the environment.