A Comprehensive Review on Hydrogels: Classification, Synthesis and Smart Hydrogels

Hydrogels are three-dimensional, hydrophilic polymeric networks that can absorb large quantities of water or biological fluids without compromising their structural integrity. They can be used in environmental research, biotechnology, agriculture, and medicine as they offer specific characteristics like significant porosity, tunable mechanical strength. This review provides an overview of types of hydrogels, their synthesis methods, and smart hydrogels. Hydrogels can be classified as natural, synthetic, or hybrid depending on their origin, and cross-linking can happen as a result of chemical or physical interactions. The physical cross-linking method, chemical cross-linking method, and irradiation-based cross-linking method are the common methods used in the synthesis of hydrogels. A significant development in the field is the use of smart hydrogels, which react to environmental stimuli including temperature, pH, light, and biomolecular interactions. These adaptable systems have great potential for biosensing, tissue engineering, wound care, and controlled medication administration.