Hydrogel Based Chemical Sensors

Hydrogels are crosslinked 3D polymeric network that can imbibe a large amount of water. The swelling ability of the hydrogel depends the hydrophilic functional groups present to the polymer backbone. These functional group may be either acidic or basic characteristics. Water uptake of hydrogel is related to a significant volume change. The sensitivity of hydrogel depends upon a number of physical factors like temperature, electrical voltage, pH, concentration of organic compounds in water, and salt concentration or via its functionalization. If the interaction between hydrogel and analytes is reversible in nature, then such hydrogels are becoming a promising candidate for being used as cost-effective, miniatured in-lined capable sensors. In broad range of application in chemical sensors, smart cross-linked gels are generally based on the external excitations by a phase transition method. In this chapter, we have included contributions of the different functional hydrogels in the chemical sensing application.