Wetting and Evaporative Aggregation of Nanofluid Droplets on CVD-Synthesized Hydrophobic Graphene Surfaces

The wetting and evaporative aggregation of alumina nanofluids (Al2O3) are examined for CVD-synthesized graphene-coated (GC) surfaces that are known as strongly hydrophobic (θcontact ≈ 90°). Our findings are compared to those associated with a hydrophilic cover glass (CG) substrate (θcontact ≈ 45°). The nanofluidic self-assemblies on the GC substrate are elaborately characterized in terms of the droplet wetting/crack formation, the particle migration time over the evaporative time (CR), the Derjaguin–Landau–Verwey–Overbeek forces (FDLVO), and the relative thermal conductivity (KR). The GC substrate forms relatively thicker and larger cracks and requires a longer evaporation time. Both the GC and CG substrates share approximately the same time constant CR, which suggests the formation of coffee-ring patterns for both substrates. The GC shows negative FDLVO, which implies a repulsive force between the nanoparticles and the substrate, and the CG shows a positive FDLVO of attraction. Furthermore, a more than 3...