ABSTRACT
Hydrogels with their cross-linked network structures can absorb large amounts of water and release water molecules during the drying process. This water uptake is associated with considerable changes in their volumes, which results in changes in optical properties like the refractive index, mechanical properties, or electrical properties. Tailoring the composition of the hydrogel or via its functionalization can tune the sensitivity of the properties of hydrogels to environmental changes. The sensitivity of these physicochemical properties to environmental changes and the volume of hydrogel has been used to design a wide range of sensors including physical and bio-chemical sensors for application in different disciplines. In this chapter, we first explain the principle of designing sensors and biosensors. Then, we explain different strategies for surface functionalization or modification of hydrogels to tailor their properties. Next, we discuss different strategies for designing sensors using the properties of hydrogels, and finally, the challenges and perspectives of hydrogel-based sensors will be presented.
