Abstract

Hydrogels are crosslinked polymer networks with a three-dimensional structure that can retain significant quantity of water because of their hydrophilic (water loving) groups, which makes them highly useful in fields such as medicine, drug delivery, and environmental science. They can be classified by source, crosslinking method, structure, or responsiveness, ranging from conventional to smart systems. Recent progress in nanocomposite hydrogels, achieved by incorporating nanoparticles such as silica, graphene oxide, carbon nanotubes, and magnetic or metallic nanofillers, has enhanced their mechanical strength, stability, and multifunctionality. These advanced systems enable applications in wound healing, drug delivery, wastewater treatment, biosensing, and energy storage, positioning them as next-generation multifunctional materials.