Hydrogels are three-dimensional networks of hydrophilic polymer chains that can absorb and retain large amounts of water. This property makes them highly suitable for controlled drug delivery systems, where they can encapsulate drugs and release them gradually over time. Their high water content also allows them to be used in some cooling applications, like portable coolers, by evaporating water. However, they are generally not used for preparing industrial lubricants, which typically require different properties like high viscosity and oil-based formulations.