Anti-Swelling Zwitterionic Hydrogels as Multi-Modal Underwater Sensors and All-in-One Supercapacitors

Although hydrogel-based electronic devices have received a lot of interest for good flexibility, biocompatibility, and multifunctionality over the past decades, underwater instability (especially in saline solutions) still limits their practical applications to a wide range. Herein, a class of tough, conductive, and anti-swelling double-network hydrogel is developed by combining the zwitterionic poly(acrylamide-co-(3-(1-(4-vinylbenzyl)-1H-benzo[d]imidazole-3-ium-3-yl) propane-1-sulfonate)) chemical network and water-resistant polyvinyl alcohol physical network with conducting polypyrrole. The resultant gel exhibits considerable mechanical strength (0.65 MPa), stable swelling dynamics in water and seawater, as well as excellent ionic conductivity (3.96 S/m). Furthermore, the assembled gel-based sensor shows distinct strain/temperature bi-modal detection. Moreover, by controlling the dimension of conductive networks, an all-in-one supercapacitor can be obtained, with ultra-high capacitance (299.79 mF/cm2) and power density (2.49 mW/cm2). We believe that this strategy will inspire researchers to develop more reliable underwater, self-powered multi-modal sensing devices in the future.