Graphene Synthesized in Atmospheric Plasmas is Inherently Superhydrophobic

Graphene produced in the gas phase using atmospheric-pressure microwave plasma technology exhibits a remarkable lotus-like water repellency. The ability of lotus leaves to repel water is desired in a wide range of applications, such as self-cleaning surfaces, waterproof textiles, anti-icing coatings, and biomedical devices. Creating artificial materials that exhibit the nonwettability of natural lotus leaves has been challenging. Superhydrophobic surfaces have been fabricated by mimicking the structure and chemistry of lotus leaves. Additionally, water-repellent coatings have been created by modifying graphene obtained through the exfoliation of graphite or substrate-based processes. However, the large-scale manufacturing of a broad range of nonwettable applications through biomimicry or modified graphene is neither sustainable nor practical. In this presentation, we reveal that gas-phase-synthesized graphene (GSG) is inherently superhydrophobic. The comparable static contact angles and roll-off angles of water droplets in direct contact with lotus leaves and as-synthesized GSG will be shown. Fascinating high-speed camera videos of water droplets impacting and rebounding from lotus leaves and GSG will be discussed. Furthermore, we demonstrate that hydrophilic materials instantly become superhydrophobic when coated with GSG. These results indicate that graphene sheets created through substrate-free plasma-based techniques have unique water-repelling mechanisms. This presentation highlights how plasmas can greatly contribute to the development of highly water-repellent surfaces.