Direct three-dimensional imaging of polymer-water interfaces by nanoscale hard X-ray phase tomography

We report three-dimensional (3D) direct imaging of complex surface-liquid interfaces by hard X-ray phase contrast tomography as a non-destructive approach for the morphological characterization of surfaces at the micro- and nanoscale in contact with water. Specifically{,} we apply this method to study the solid-air-water interface in hydrophobic macroporous polymethacrylate surfaces{,} and the solid-oil-water interface in slippery liquid-infused porous surfaces (SLIPS). Varying the isotropic spatial resolution allows the 3D quantitative characterization of individual polymer globules{,} globular clusters (porosity) as well as the infused lubricant layer on SLIPS. Surface defects were resolved at the globular level. We show the first application of X-ray nanotomography to hydrated surface characterizations and we anticipate that X-ray nanoscale imaging will open new ways for various surface/interface studies.