Liquid marbles from soot films

Soot films are the most easily available superhydrophobic surfaces. However, their cohesive forces are very weak such that they have been considered not suitable for direct use. Here we show that the seemingly undesirable mechanical weakness is actually an important property which allows a soot film to work as a superhydrophobic platform and tool, producing liquid marbles with fascinating properties and performances. A soot film is weak enough to lose component carbon nanoparticles (CNPs) on contact with water, but can adhere to a substrate stably on overturning or shaking the substrate. On this basis, we demonstrate that a liquid marble consisting of a liquid core and a CNP shell can be obtained by either rolling or an imprinting process. In addition, it is found that large-volume liquid puddles are easy to produce and manipulate with soot films by arbitrary shaking and pouring operations, without worrying about particles flying off that would occur in conventional powder-based liquid puddle production. The multifunctionality of CNPs endows soot liquid marbles/puddles with great potential in light shielding, electrical conduction, etc. This study reveals a direct application of soot films' superhydrophobicity, provides an alternative route for liquid marble production, and highlights the concept of disadvantage reversion.