Laser induced graphene printing of spatially controlled super-hydrophobic/hydrophilic surfaces

Spatial control over the wetting properties of graphene surfaces is a desired feature in numerous applications. Traditionally, this is achieved using time consuming chemical treatment processes that lack spatial tuning. Here, we demonstrate the use of laser induced graphene for the direct, spatial printing of surfaces with either superhydrophilic or superhydrophobic character through simple and convenient control over graphene array morphology, and without the need for chemical surface modification. The wetting properties of the graphene surfaces range from superhydrophilic (0°) for sheet-like structures, to superhydrophobic (>150°) for micro-pillar and hemispherical structures. By varying the induction parameters of the CO2 laser, we demonstrate the ability to write patterns with spatially tailored wettability to enable liquid micro-patterning and channeling of flow. Furthermore, we study solid-liquid interactions for such surfaces using viscosity measurements, where a "petal effect" is observed in the graphene material, thus revealing the parahydrophobicity of the surface.