Direct insight into the three-dimensional internal morphology of solid-liquid-vapor interfaces at microscale.

Solid-liquid-vapor interfaces dominated by the three-phase contact line, usually performing as the active center in reactions, are important in biological and industrial processes. In this contribution, we provide direct three-dimensional (3D) experimental evidence for the inside morphology of interfaces with either Cassie or Wenzel states at micron level using X-ray micro-computed tomography, which allows us to accurately "see inside" the morphological structures and quantitatively visualize their internal 3D fine structures and phases in intact samples. Furthermore, the in-depth measurements revealed that the liquid randomly and partly located on the top of protrusions on the natural and artificial superhydrophobic surfaces in Cassie regime, resulting from thermodynamically optimal minimization of the surface energy. These new findings are useful for the optimization of classical wetting theories and models, which should promote the surface scientific and technological developments.