Stretchable conductors: Thin gold films on silicone elastomer

Thin stripes of gold deposited onto elastomeric substrates can be stretched reversibly by more than 20% while remaining electrically conducting. We are developing such stripes to serve as electrical interconnects on stretchable electronic skins. The gold layers are 25-nm to 500-nm thick. We observe two different film morphologies: the stripe is either buckled and continuous, or flat and contains micrometer-long cracks. Stretchability is correlated with the thickness and initial topography of the gold layer. Stripes thicker than 100-nm fail electrically at tensile strain of ∼1%, while thinner stripes remain conducting up to much larger strain. Upon stretching the buckled stripes flatten and break into islands of 1 to 100 micrometers on a side, while the initially microcracked stripes retain their micrometer scale structure. The electrical resistance of the buckled stripes is the lowest but the micro-textured stripes can be stretched more.