a foldable polymer - based coil structure and a method for fabricating the same are disclosed . the coil structure has metal wirings and interconnections between the wirings . the wirings and connections are embedded by a polymer . the coil structure is foldable in two or more layers . in the folded condition , coils of one layer overlap the coils of another layer . a stackable structure and jigs for aligning the foldable and stackable structures are also disclosed .