While flexibility and transparency have already been achieved in electronics, the expansion of wearable electronics is driving the need for fully transparent circuits on a rollable substrate. Now, a research team in Korea has successfully produced rollable and transparent electronics that are lightweight and damage-resistant.
The team, led by Jin Jang, Ph.D., director of the Department of Information Display at Kyung Hee University, has overcome two major challenges associated with the manufacture of flexible electronics: The temperature restriction of plastic substrates (less than 100 C) and the difficulty of handling flexible electronics during the fabrication process.
“To overcome the temperature restriction we chose our plastic substrate to be polyimide (PI), which is a polymer of imide monomers,” Jang explains. The researchers also chose an amorphous oxide semiconductor – amorphous-indium-gallium-zinc-oxide (a-IGZO) – which assures good device performance even when sputter-deposited at low temperatures. The dielectrics are transparent and the substrate PI is colorless and very thin, making the final product transparent and rollable.
To address the second major challenge – the difficulty of handling flexible electronics during the fabrication process – the researchers used a carrier glass substrate on which the colorless PI (CPI) is first spin-coated from solution and then detached from after device fabrication. Jang’s team spin-coated a mixture of carbon nanotubes (CNT) and graphene oxide (GO) to a thickness of 1 nm from solution onto of the carrier glass before spin coating the CPI.
After fabrication, only a small amount of mechanical force is required to detach the CPI from the glass. The researchers say the beauty of having the CNT/GO layer is that it bonds stronger with the CPI compared to the glass, such that it remains embedded to the backside of the CPI after detachment, providing mechanical support to the flexible electronics and making the rollable electronics wrinkle-free.