Although surfaces can be made to attract or repel liquids using coatings, surface textures with specific curvature can also be used to achieve the same effect. However, fluid transport is usually limited by the specific pattern that only drives flow at the surface itself. Feng et al. created a dual-reentrant surface that has an asymmetric profile so that fluids spread out at the surface and subsurface layers. Furthermore, these surfaces can be designed so that different liquids will naturally steer in opposing directions simply because of their specific interactions with the surface.
The full article Three-dimensional capillary ratchet-induced liquid directional steering can be read online at in Science 17 September 2021: https://www.science.org/doi/abs/10.1126/science.abg7552
