Effect of Rib Angle on Capillary Flow in Closed Hierarchical Microchannels

Biomimetic-inspired surfaces have the potential to enhance water transport efficiency, as channels with hierarchical micro/nanoscale structures demonstrate improved capillary flow characteristics. The applicability of the classical Lucas-Washburn equation for capillary-driven flow in open rectangular microchannels has been debated, and its validity for hierarchical microchannels remains uncertain. In this study, numerical simulations using Volume-of-fluid- based OpenFOAM were used to examine the effect of rib angle in hierarchical microchannels, focusing on the impact of fabrication errors on capillary performance. The results indicate that if the rib is not perpendicular to the bottom surface/wall of the channel, capillary performance reduces. With the change in the type of rib inclination, the capillary performance also changes. This study underscores the importance of precise fabrication in optimizing the efficiency of hierarchical microchannels.