Gradient Hydrogels—The State of the Art in Preparation Methods

Gradient hydrogels refer to hydrogel materials with a gradual or abrupt change in one or some of their properties. They represent examples of more sophisticated gel materials in comparison to simple, native gel networks. Here, we review techniques used to prepare gradient hydrogels which have been reported in literature over the last few years. A variety of simple preparation methods are available, most of which can be relatively easily utilized in standard laboratories.