Continuous Directional Water Transport on Hydrophobic Slippery Ventral Skin ofLampropeltis pyromelana

Natural systems contain surfaces with unique wettability that enable functionalities such as directional liquid transport. Such systems typically rely on nano/microscale structural anisotropy and/or chemical structures, which induce a directional friction at solid-liquid interfaces. Here, the origin of the solid-liquid interfacial tribo-dynamics of the skin ofLampropeltis pyromelana(Arizona Mountain Kingsnake) is examined. Continuous and directional water transport phenomenon is found on its hydrophobic slippery ventral skin. Liquid is continuously supplied and spread on its skin in a rear to front direction although the surface is slippery. X-ray tomography and spectroscopy reveal that the skin surface is composed of an asymmetric wrinkle structure and a homogeneous hydrophobic lipid layer. Owing to this surface feature, the rear directional water spreading is restricted by slant reentrant pinning, whereas the front directional water spreading is promoted by liquid bridging, which continued as long as water is supplied. Because this system type relies on a superhydrophilic sticky surface, it is expected that related biological design principles can be used to develop artificial mass fluid transport systems without undesirable adhesion losses.