Anti-swelling Zwitterionic Nanocomposite Hydrogels with Biocompatibility as Flexible Sensor for Underwater Application

The increase in underwater activities has driven the demand for underwater flexible sensors, which can detect various signals from both humans and the environment in real time to improve work efficiency and ensure safety. However, the fabrication of underwater sensors remains challenging due to the swelling of hydrogels in water and the non-eco-friendliness of the sensors, which poses significant risks to users and the application environment. Here, a hydrogel-based sensor composed of poly [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide and bacterial cellulose nanofibers, featuring self-adhesion, biocompatibility, and anti-swelling behavior, is fabricated using an environmentally friendly method. The electrostatic interaction between zwitterionic functional groups (positively charged -R3N⁺ groups and negatively charged - SO^3- groups) endows the hydrogel with excellent anti-swelling behavior in aquatic environment. Owing to these characteristics, the hydrogel sensor is capable of monitoring movements in both air and underwater environment. Based on the hydrogel sensor, an intelligent communication system is developed to facilitate information transmission in water. Moreover, the excellent biocompatibility of the hydrogel sensor highlights its safety for users and the environment, demonstrating its great promise for electronic skin. As such, the biocompatible hydrogel sensor with anti-swelling capabilities provides a promising route to promote the development of wearable devices.