Superspreading\nWetting of Nanofluid Droplet Laden\nwith Highly Dispersed Nanoparticles

Wetting of nanofluids containing highly dispersed nanoparticles\nof single-nanometer size was investigated, as these nanoparticles\ncan persist within a nanometer-scale liquid film near contact line,\npotentially causing significant changes in wetting characteristics.\nWe discerned distinctive superspreading wetting, featured by temporal\nindices (0.29 to 0.46) in the relationship between contact radius\nand time. We employed a phase-shifting imaging ellipsometer to measure\ndroplet shape, including the nanometer-scale liquid film and nanoparticle\nlayer after drying. The liquid film shapes differed from pure liquids\nat micrometer-scale but not at nanometer-scale. Furthermore, surface\ntension measurements and substrate surface energy control contributed\nto unraveling these characteristics. These findings differentiated\nthe observed superspreading wetting from the mechanisms proposed in\nexisting studies of aqueous surfactant solutions.