Hydrogel
Hydrogels are three-dimensional polymeric networks filled with water. The water content can reach as high as 90-99% depending on the polymer concentration. It contains polymers that are attracted to water, they swell and hold large amounts of water while maintaining their structure due to chemical or physical cross-linking of individual polymer chains. The physical cross-linked hydrogels are easily pulled and relaxed, like a rubber band. The chemically cross-linked hydrogels avoid deformation. The behaviour of hydrogels is typically viscoelastic which is associated with the water and the movement of polymer networks in fluids. Similar to other polymers, there are natural and man-made hydrogels. The man-made hydrogels are also known as synthetic, this allows the hydrogels to have a longer service life, hold more water, and have greater strength.