Advances in Directional Wetting Surfaces for Enhanced Fluid Control: A Comprehensive Review

Abstract

Controlling surface wettability and directing the flow of working fluids have crucial implications in various natural and engineering contexts. Understanding the fundamental principles of wettability and directional wetting is essential for effectively leveraging these phenomena to enhance the performance of engineering systems, such as microfluidics or heat exchangers. This comprehensive review summarizes of previous research, emphasizing recent advances by categorizing the structures and working principles associated with directional wetting surfaces. The efforts of researchers who have employed diverse strategies to manipulate the wetting behavior of liquids through both passive and active control mechanisms are highlighted. Passive directional transport surfaces require no additional energy while enabling large‐scale and continuous fluid control. Conversely, active directional wetting surfaces offer enhanced flexibility and precise control of liquid movement. Furthermore, insights into recent studies that focused on practical applications are provided and the current challenges that need to be addressed are discussed. This study serves as a guide for future research directions on the development of directional wetting surfaces and offers valuable recommendations for practical implementation.

White Roman Goose Feather-Inspired Unidirectionally Inclined Conical Structure Arrays for Switchable Anisotropic Self-Cleaning

“…The anisotropic spreading further guides the water droplets to slip off butterfly wings in the direction away from its body even in a highly humid environment . Similar directional liquid transports from higher liquid-pinning regions to lower liquid-pinning regions are evidenced by various asymmetric architectures such as hairy forests or ratchets. , Unfortunately, challenges are encountered in driving low-surface-tension organic liquids. The structures are easily contaminated by oleophilic materials on contact, which severely impedes their controllable wetting ability and the corresponding directional self-cleaning functionality.…”