Thin-film stretchable electronics technology based on meandering interconnections: fabrication and mechanical performance

A new fabrication technology for stretchable electrical interconnections is presented. This technology can be used to connect various non-stretchable polyimide islands hosting conventional electronic components. The interconnections are realized by patterning a 200 nm thick sputter-deposited gold film into meandering horseshoe shapes, functioning as 'two-dimensional springs' when embedded in a silicone elastomer. Polyimide support is introduced around the meandering conductors as a means to improve the mechanical performance. Processing is done on a temporary carrier; the islands and interconnections are embedded in polydimethylsiloxane in a final stage. To this end, a release technique compatible with high temperatures up to 350 degrees C based on the evaporation of a 400 nm thick layer of potassium chloride is developed. Test structures consisting of stretchable interconnections with a varying polyimide support width were fabricated. These were strained up to twice their original length without compromising their functionality. Also cyclic mechanical loading at various strains was performed, indicating the influence of the polyimide support width on the lifetime. At strains of 10%, a minimum lifetime of 500 000 cycles is demonstrated. The presented technology thus provides a promising route towards the fabrication of stretchable electronic circuits with enhanced reliability.