Abstract: Stretchable electronic devices are widely used in applications in biomedical devices and conformal antennas that require intimate integration with complicated surfaces of elastomers.The island-bridge layout improves the stretchability in practical flexible electronic devices,among which U-patterned interconnects have been designed to enable devices' repeatable stretchability up to 40%.While the island-bridge-substrate structure is stretched,complex deformation is observed by use of FEM.These structures suffer unilateral tension and compression,global tension and plastic deformation.The width and length\spacing ratio significantly influent the stretchability.The results demonstrate that reduction of width enhances the stretchability,while degrades it when width becomes too small.When width is large,out-plane buckling appears before cracks occur.Spacing always increases the stretchability while the dimensions would become large.When the length/spacing ratio is smaller than 1.4,the stretchability increases as it grows.Therefore,study for the deformation mechanism of U-patterned interconnects could optimize its geometry parameters and improve the stretchability of flexible electronic devices.

Key words: buckling, flexible electronics, film-on-substrate structures, U-patterned interconnects