Suitably Patterned Thin Stiff Films as General Platforms for Flexible Electronics

We propose a general principle to make thin films of stiff materials compliant by suitably patterning. Such a principle is demonstrated by three patterns: a film in serpentine shape, a film with distributed branched cracks, and a film with distributed parallel cracks. We show that such a patterned film elongates by deflecting and twisting out of plane, accommodated by the compliance of the substrate and the pattern of the film. Consequently, large elongations of the substrate induce small strains in the film. We further propose that such a patterned film with large area can serve as a platform, on which entire electronic circuits can be fabricated using the planar microfabrication technology. Such circuits will function without appreciable fatigue when the substrate is repeatedly bent, twisted, and stretched.