The spreading and splashing of graphene oxide dispersions

The impact of Newtonian fluid droplets on a solid surface has been extensively studied but much remains to be understood for the splashing and spreading of non-Newtonian fluids. We experimentally study the splashing and spreading behavior of non-Newtonian colloidal suspensions of graphene oxide, a high aspect ratio 2D nanoparticle, in an ethanol-water mixture. Graphene oxide suspensions are shear thinning and exhibit yield stress behavior at higher concentrations. Recent studies on some weakly shear thinning fluids have shown that the existing Newtonian models can predict whether these fluids will splash or spread on a solid surface for a given impact velocity. For higher concentrations of graphene oxide suspensions, we have observed deviations from the predicted splashing behavior. We also examine the spreading behavior of the suspensions on a solid surface, exploring how the maximum spreading ratio of 2D nanoparticle suspension droplets changes with impact velocity and particle concentration.