Ramified fractal-patterns formed by droplet evaporation of a solution containing single-walled carbon nanotubes

Single-walled carbon nanotubes (SWNTs) in aqueous and ethanol solutions can be self-assembled into ramified fractal-patterns, ring-patterns or fingering-patterns on silicon wafers over a large area under controlled evaporation conditions by the droplet evaporation method. The formation of these regular patterns can be attributed to the Marangoni effect and diffusion-limited aggregation (DLA) in the liquid film during droplet evaporation at different conditions. This simple method to assemble SWNTs will provide potential applications for advanced devices and sensors.