Liquid directional steering on Nepenthes-inspired surfaces with inclined perforated arch-cavity structure

Directional liquid transport holds tremendous potential in water harvesting, microfluidics and thermal management. Despite great progress, engineering a surface with fixed structural design that enables liquid directional steering based on its intrinsic properties, such as surface tension, remains a pressing challenge. Here, inspired by the unique arched microcavities of Nepenthes, we fabricated an asymmetric surface composed of an array of inclined perforated arch-cavity structure. The designed surface demonstrates remarkable surface-tension responsiveness with high- and low-surface-tension liquids transporting along entirely distinct pathways, separated by a critical transition contact angle of 49° ± 5°. Below this threshold, low-surface-tension liquids wick through the bottom porous channels and spread along the structural incline. Above it, high-surface-tension liquids are pinned at the bottom and transport across the top of the structures with direction opposite to the incline. Further flexible design of structured surface allows efficient directional liquid transport across complex terrains, coupled with direction steering by tensile forces, manifesting an outstanding multi-scenario suitability. This structural design paves the way for advanced applications in flexible electronics, lab-on-a-chip systems, and self-driven fluidic devices.