Natural organisms have evolved highly sophisticated mechanisms for managing water across a broad range of environmental conditions, from arid to highly humid regions. Among these mechanisms, directional liquid transport (DLT) is particularly noteworthy, as it relies on structural designs that facilitate the spontaneous movement of liquids along predefined pathways without the need for external energy sources. The increasing interest in DLT systems is primarily driven by their potential applications in fields such as microfluidics, water harvesting, and biomedical engineering. The focus on DLT is motivated by its ability to inspire efficient, energy-independent liquid transport technologies, which hold significant promise for both fundamental research and practical applications. Notably, wedge-shaped DLT systems have emerged as a particularly promising area of study due to their advantages in terms of manufacturability, liquid collection efficiency, and scalability—attributes that are essential for industrial deployment. This review seeks to explore natural wedge-based DLT systems, providing an in-depth analysis of their underlying principles and their potential for engineering replication. The discussion includes examples from nature, such as desert beetles and spider silk, and explores the theoretical mechanisms governing these systems, including the role of surface energy gradients and Laplace pressure. Additionally, the review highlights advanced fabrication techniques, such as photolithography and laser micromachining, which are crucial for the development of these systems in practical applications.

The development of efficient directional liquid transport systems has become a central focus in numerous research and engineering fields. Natural organisms have evolved intricate structures that facilitate the controlled movement of liquids on planar surfaces. These natural mechanisms offer insights into creating sustainable, energy-efficient technologies that mimic these natural adaptations. The purpose of biomimetic directional liquid transport is to harness the principles found in nature to design systems that can autonomously manage the flow of liquids. One of the core objectives is to achieve efficient liquid directional movement without the need for external energy sources or mechanical pumps. In this article, we review the typical models of natural systems with directional liquid transport on planar surfaces. Next, we reveal the physical mechanism by which surface chemical gradients, wettability gradients, and geometric gradients synergically drive liquid directional motion. Then, we introduce the breakthroughs of bionic surface engineering strategies in water harvesting, directional liquid transport and recent advancements in engineering applications. Finally, we give a conclusion and future perspectives on the development of directional liquid transport.

Directed transfer of liquids is widely used as an important mass transfer strategy in the nature biology, industry, agriculture, and medical fields. Based on the bionic concept, researchers have constructed various forms of surface structures to realize controlled transport of liquids. However, current methods for preparing surfaces with directional liquid transport often suffer from cumbersome preparation processes, complexity of the prepared structures, and high costs. In this paper, we prepared a topological structure surface capable of precisely controlling liquid transport by a facile method. By utilizing 3D printing technology, we designed and fabricated a wedge-shaped surface with a periodic tilting scale arrangement. We accomplished the precise regulation of liquid transport on the surface of the structure, which not only realized the bi-directional transport of liquid anisotropically to the uni-directional transport on the surface but also achieved the precise regulation of the distance and speed of liquid transport through adjusting the opening angle formed by the open-wedges. We expect that the as-prepared wedge-shaped surface will provide a facile and efficient strategy for directional liquid transport.