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

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.