Biomimetic Liquid Diodes Across Materials and Scales for Directional Liquid Transfer

The last decade has witnessed remarkable advancements in liquid diode, evolving from fundamental research to cutting-edge applications such as microfluidics, thermal management, and wearable electronics. However, how material characteristics and structural scales mediate liquid transport on liquid diodes has yet to be fully clarified to date. In this study, we develop a Crassula muscosa inspired liquid diode (CMLD) with superior material adaptability and structural scale adaptability spanning three orders of magnitude. Such a liquid diode endows a cross-material, and cross-scale unidirectional liquid transfer from microscale to macroscale. The mechanisms underlying the role of the wettability, viscosity and structure scale in regulating the liquid transfer kinetics including transfer distance, transfer velocity and liquid rectification, are clearly demonstrated. By combining experimental observation, numerical simulation, and building a theoretical retention force model, the liquid transfer and pinning mechanisms governed by asymmetric reentrant structures are systematically elucidated, which enables superior robustness for unidirectional liquid transfer of continuous flows with various flow rates. These results provide a robust framework for coupling material characteristics and structural scales to achieve controllable unidirectional liquid transfer, laying a solid foundation for the practical implementation of liquid diode-based technologies.