Controlling Directional Liquid Transport on Dual Cylindrical Fibers with Oriented Open‐Wedges

Abstract Directional liquid transport (DLT) on fibrous systems has been widely used in both natural organisms and practical applications as an important mass transfer strategy. So far, DLTs on fibers are heavily dependent on the conical structure that enables generating the Laplace pressure difference. For the cylindrical fibers, liquid can only transport evenly along both directions of the axis driven by the capillary forces between fibers, which however hardly proceeds directionally in a controllable way. Here, the authors revealed that the dual cylindrical hairs bear the ability of DLT, which is attributable to the wet‐rebuilt open‐wedged scales. Capillary forces along wedge corners facilitate the liquid transport in the against‐scale direction, while the pinning effect at the sharp edges of open‐wedges works cooperatively with the anisotropic retention force imparted by the ratchet structures to inhibit liquid spreading in the with‐scale direction. Consequently, liquid prefers to transport in the against‐scale direction on dual cylindrical hairs. Drawing inspirations, the authors develop the conceptual‐model of dual cylindrical fibers that is capable of DLT, and moreover the DLT with different rectification ratios can be well‐controlled depending on the opening angle of wedges. The result offers new insights for manipulating liquid using cylindrical fibrous systems.