Engineering reversible elasticity in ductile or brittle thin films and products resulting from said engineering

The present invention relates to how to engineer reversible elasticity in thin films and/or layers and/or substrates, using a repeated Y-shaped motif, which is cut out throughout the film and/or layer and/or substrate. As an example, using a 75 μm thick polyimide (PI) foil, macroscopic dog-bone shaped structures with a range of geometrical parameters of the Y shape have been prepared according to an embodiment of the present invention. The tensile strain response of the film at its point of fracture was then recorded. The structures were also confirmed using Finite Element Modeling. Upon stretching, the PI ligaments locally deflect out of plane, allowing the foil to macroscopically stretch.