Anti-swelling hydrogel with three-dimensional print for underwater communication

With the extensive development and application of hydrogel strain sensors, people have begun to pay attention to hydrogel strain sensors with water-resistant properties and multi-dimensional complex shapes, such as underwater sensors and printable sensors. Here, we successfully designed a novel multifunctional hydrogel, which was not only an anti-swelling hydrogel by double hydrophobic crosslinking for underwater strain sensor, but also carbomer-modified printable hydrogels for multi-dimensional complex strain sensors. The structure, mechanical, anti-swelling and sensing properties of the modified polyacrylamide hydrogel were also systematically analyzed. The experimental results demonstrated that the hydrogel exhibited excellent anti-swelling properties, with a maximum stress of up to 570 kPa after swelling for 48 h. Meanwhile, by introducing carbomer, the hydrogel was imbued with Bingham fluid characteristics, allowing it to be printed into various strain sensors and still exhibited high deformation sensitivity even after swelling for 48 h. Notably, the aforementioned hydrogel was also successfully applied to underwater signal transmission, where it not only monitored the swimming movements of a small wooden figure, as swinging arms and bending knees, but also measured Morse code through finger movements and sent out emergency signals. Collectively, the study would hopefully provide a novel strategy for underwater signal transmission and sensing rescue.