Fig. 7

Manufacturing processes that involve various sequences of forming networks. a A preformed hydrogel network on a preformed elastomer network. A PAAm hydrogel and a PDMS elastomer are separately molded, and then placed in contact with a thin film of paraffin sandwiched in between. After curing, the contact region between the hydrogel and the elastomer forms bonds while the paraffin region does not. The bonding remains intact as a nozzle inflates the hydrogel into a balloon. b Forming an elastomer network on a preformed hydrogel network. A PAAm G-clef is molded, and then dip-coated with a thin layer of PDMS. The PDMS-coated PAAm is dyed in a bath. The color is readily washed away in clean water. By comparison, if a naked hydrogel is dyed in the bath, the color cannot be washed away. c Forming a hydrogel network on a preformed elastomer network. A PDMS film is cast first. On the PDMS film, a hydrogel ionic circuit with the shape of an anglerfish is written using a syringe. A light-emitting diode (LED) is switched on. The circuit remains adherent when the elastomer is stretched. d Forming a hydrogel network and an elastomer network together. A silane-modified PAAm hydrogel resin is colored with a blue dye and extruded on a Petri dish. Partially cured PDMS resin is then extruded into lines perpendicular to the hydrogel lines. After curing, the mesh withstands stretching. The scale bars represent 10 mm