"There are no conductive, transparent and stretchable materials in nature, so we had to create one," said researcher Abhijeet Bagal. "Our technique, which uses geometry to stretch brittle materials, is inspired by springs that we see in everyday life. The only thing different is that we made it much smaller."
The researchers began by creating a 3D polymer template on a silicon substrate. The template, shaped like a series of identical, evenly spaced rectangles, was coated with a layer of aluminum doped zinc oxide, followed by an elastic polymer. The team then flipped the composite and removed the silicon and the template.
The result is a series of symmetrical zinc oxide ridges on an elastic substrate. Because the zinc oxide and polymer layers are clear, the structure is transparent. It can also be stretched because the ZnO ridges allow the structure to expand and contract, like the bellows of an accordion.
Fellow researcher Erinn Dandley added: "We can control the thickness of the ZnO layer and have done extensive testing with layers ranging from 30 to 70nm thick. This is important because ZnO thickness affects the structure's optical, electrical and mechanical properties."
The structure is said to be capable of being stretched repeatedly without breaking. While there is some loss of conductivity the first time it is stretched, further stretching has no effect.
The team is now experimenting with other conductive materials to determine their usefulness in creating non-transparent, elastic conductors.
