Made mostly of water, hydrogels are stretchy and absorbent until they inevitably dry out. Now engineers at MIT have found a way to prevent hydrogels from dehydrating, with a technique that could lead to longer-lasting contact lenses, stretchy microfluidic devices, flexible bioelectronics, and artificial skin. The engineers devised a method to robustly bind hydrogels to elastomers - elastic polymers such as rubber and silicone that are stretchy like hydrogels yet impervious to water. They found that coating hydrogels with a thin elastomer layer provided a water-trapping barrier that kept the hydrogel moist, flexible, and robust. The group took inspiration for its design from human skin, which is composed of an outer epidermis layer bonded to an underlying dermis layer. The epidermis acts as a shield, protecting the dermis and its network of nerves and capillaries, as well as the rest of the body’s muscles and organs, from drying out.