High stability PAM/glycerol hydrogels and its applications in lenses and actuators

Hydrogels are characterized by high water content and are typically used in water environments. However, when used in air environments, hydrogels face limitations due to instability caused by water loss. This study reports the development of PAM/glycerol hydrogels with improved stability. By using water–glycerol bi-solvents to lock in water internally, a closed environment was established to reduce water exchange with the outside world. The hydrogel was made by forming a single PAM crosslinking network using UV crosslinked acrylamide (AM) monomer. The weight of the hydrogel varied by no more than 2% within 6 days, and the visible light transmittance was higher than 90%. In addition, the hydrogel had adjustable refractive index and mechanical properties. The hydrogels with stable performance could be used to fabricate optical lens with practical function in air environment. Meanwhile, the gels also have certain advantages in making a fluid-driven hydrogel actuator with stable performance.