UV-assisted coaxial DIW 3D printing: a strategy for fabricating environmentally adaptive ionic hydrogel sensors

Ionic conductive hydrogels have gained extensive attention in the field of intelligent sensing due to their good flexibility, tunable electrical conductivity, and multi-stimuli responsiveness. However, hydrogels easily freeze, dehydrate, or swell in external environments, thus losing their original structure and functions. Therefore, improving the environmental adaptability of conductive hydrogels remains a challenge. Herein, ionic hydrogels were encapsulated in real time via UV-assisted multi-material coaxial direct ink writing (DIW) 3D printing, and ionic conductive hydrogel sensors with array structures were prepared. The core ionic conductive hydrogel is isolated from the external environment by the hydrophobic photocurable polydimethylsiloxane (PDMS) shell resin. The sensor exhibits excellent environmental adaptability with stable sensing performance after 60 days in dry environments or underwater, accurate temperature monitoring across a wide range of −20–120 °C, reliable sensing capabilities at both high and low temperatures, and stable application in acid, alkali, and organic solvents. This work proposes a simple strategy for fabricating a new type of ionically conductive hydrogel sensor, which overcomes the environmental application limitations of traditional hydrogel sensors.