Hydrogels: Definition, History, Classifications, Formation, Constitutive Characteristics, and Applications

Hydrogels are some of the most fascinating soft materials that have been widely explored and employed in the biomedical field due to their distinctive characteristics like high water content, softness, biocompatibility, low cost, and general ability to mimic soft human tissues. The extent of hydrogel research is currently growing rapidly and creating more paths in different fields of advanced biomedical research like drug release systems, tissue engineering/regeneration, wound healing, sensor technologies and pharmacological applications. Although there is much knowledge of hydrogel research in the literature, a compilation and overview of the status of scientific research, which could help to improve the preparation, characterization, and application of hydrogels in these disciplines is considered useful. This chapter thus gives a general overview of hydrogels, their classification, characterization methods, and targeted biomedical fields where they are currently being utilized. Furthermore, it also provides a synopsis of the historical and advanced development in hydrogel technology.