Elucidating on the drop impact dynamics of water-in-oil microemulsions via advanced rheometry

Microemulsions are promising for diverse applications, but their complex rheology, especially at high shear rates, poses characterization challenges. This study investigates the impact of water-in-oil microemulsion drops on flat and curved surfaces, focusing on the critical role of high-shear rheology. We assessed rheological properties across a wide range of shear rates by combining conventional methods, high-frequency rheometry, and a recently developed drop-impact viscometry (DIV) technique. DIV captures a substantial apparent viscosity increase (up to 12-fold) at high shear rates, enabling the prediction of maximum spreading and splashing thresholds. We observed complete splash suppression at high-impact velocities, where splashing is typically severe. These insights into high-shear rheological properties are crucial for optimizing microemulsion formulation and performance in applications such as spray and fuel injection. • Splashing is suppressed in high-velocity impacts of microemulsion drops. • Nanodroplets thicken the lamella and decrease maximum spreading. • Drop Impact Viscometry reveals apparent viscosity rise at high shear rates. • Drop Impact Viscometry enables predictions of spreading and splashing.