Membranes of poly dimethyl siloxane, a silicone polymer, are used as substrates for electronic skin. These are large-area circuits that can be stretched over surfaces of arbitrary shape. Much of e-skin technology requires making thin-film devices atop poly dimethyl siloxane. This silicone is quite soft, while most device materials are hard. When hard films are put on the silicone membrane, their surface easily forms wrinkles.