Manipulating overflow separation directions by wettability boundary positions

Facile strategies to realize controllable overflow separation are urgently needed for advances in liquid-directional transportation systems and liquid delivery devices. Here, we present a wettability boundary based destabilization mechanism for direct separation of liquid flow from the solid edge at the (super) hydrophilic-superhydrophobic dividing line. Macroscale fluid dynamics is precisely controlled by modifying micro- and nanoscale surface structures and chemical compositions. Coupling surface wettability boundaries with flow inertia, flow separation angles are finely adjusted. These findings not only provide physicochemical insight into the understanding of the mechanisms on the dynamics of fluid at solid edges, but also promote the development of nanoscience in hydrodynamic applications.