Hydrogels, chemically responsive methods

This section looks at three examples of actuation for bio-responsive chemical hydrogels and describes how these methods have been used in the development of biosensor, drug delivery and tissue scaffold systems. These three actuation examples are classified in Table 2.1 as follows changes in cross-finking density (1—8), electrostatic interactions (9—13) and molecular conformation (14, 15). 

Hydrogels have been synthesized based on both chemical (covalent bonds between polymer chains) and physical crosslinking (e.g., polymer chain entanglements, ionic interactions, and hydrogen bonds) methods (Hoffman, 2002) (Figure 1.5). Covalently crosslinked thermo-responsive hydrogels exhibit reversible swelling of the crosslinked... 

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