Hydrophilic coatings exhibit water-loving characteristics. Chemically, this means they participate in dynamic hydrogen bonding with surrounding water. In most cases, hydrophilic coatings are also ionic and usually negatively charged, which further facilitates aqueous interactions. Physically, these chemical interactions with water give rise to hydrogel materials that may exhibit extremely low coefficients of friction. Taken together, such chemical and physical characteristics describe a class of materials that are wettable, lubricious, and suitable for tailored biological interactions.