What is Hydrogel?
'''Hydrogels''' are three-dimensional [[Polymer|polymeric]] networks filled with water. The water content can reach as high as 90-99% depending on the polymer concentration. It contains [[Polymer|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 [[Viscosity|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. There are many types of hydrogels. The most common ones are [[pH]]-sensitive hydrogels, which respond to [[pH]] changes in the environment. [[Temperature]]-sensitive hydrogels, which are affected by how hot or cold the environment is. [[Electricity|Electro]]-sensitive hydrogels, which either shrink or expand when an [[electric field]] is applied. Lastly, the [[Light|light-]]<nowiki/>responsive hydrogels respond to light. In many ways hydrogels are similar to our bodies because the human body is made out of mainly water and [[matrix]] materials that are surrounded by [[Cell|cells]]. This is why hydrogels can be used in [[tissue engineering]]. Hydrogels are filled with water so they mimic tissue environments, this means they are optimal to deliver cells and repair damaged [[tissue]]. [[Category:Polymers]]