ABSTRACT
Hydrogels are three-dimensional networks of hydrophilic polymer chains which do not dissolve but can absorb a large amount of water, usually more than 20% of the total weight [1-7]. The hydrophilic properties enable hydrogels to hold a large amount of water within their structure. The high water content together with soft-surface properties can offer good biocompatibility of the hydrogels [8]. Moreover, synthetic or processing methods using various functional polymers can be manipulated to possess various properties including physicochemical, mechanical, and biological properties, as well as new functional properties. For example, hydrogels can be made to respond to environmental stimuli, such as temperature, pH, light, and specic molecules like glucose by employing the functional components. These properties have drawn great attention from academia as well as pharmaceutical and biomedical industries.
