Extremely Uniform Graphene Oxide Thin Film as a Universal Platform for One-Step Biomaterial Patterning

Graphene oxide (GO) has proven to be a highly promising material across various biomedical research avenues, including cancer therapy and stem cell-based regenerative medicine. However, creating a uniform GO coating as a thin layer on desired substrates has been considered challenging owing to the intrinsic variability of the size and shape of GO. Herein, a new method is introduced that enables highly uniform GO thin film (UGTF) fabrication on various biocompatible substrates. By optimizing the composition of the GO suspension and preheating process to the substrates, the "coffee-ring effect" is significantly suppressed. After applying a special postsmoothing process referred to as the low-oxygen concentration and low electrical energy plasma (LOLP) treatment, GO is converted to small fragments with a film thickness of up to several nanometers (≈5.1 nm) and a height variation of only 0.6 nm, based on atomic force microscopy images. The uniform GO thin film can also be generated as periodic micropatterns on glass and polymer substrates, which are effective in one-step micropatterning of both antibodies and mouse melanoma cells (B16-F10). Therefore, it can be concluded that the developed UGTF is useful for various graphene-based biological applications.