A Comparative Study of Wicking Flow on Micro-Engineered Surfaces Using Micro-PTV and Phase-Field Lattice Boltzmann Method*

Wicking in micro-engineered surfaces has gained significant attention owing to its broad applications in thermal management, bioengineering, microfluidics, textile industries, and oil recovery. The underlying advantages of these pillar structures lie in maximizing surface area to volume ratio and passive pumping mechanism. The passive pumping mechanism supplies fluid via capillary wicking which eliminates the need for external pumping. The wicking performance in these applications could be improved by understanding the flow dynamics and its variation with the pillar structure of these surfaces. This study explores the effect of pillar structure on wicking enhancement via a combination of numerical and experimental studies. The numerical approach is based on the phase-field Lattice Boltzmann method, whereas the experimental validation takes advantage of the microfabrication technique and 3D micro-PTV to track the wicking flow and 3D velocity profile. The results analyze the leading film flows with different pillar shapes and illustrate the importance of 3-phase contact lines to model the capillary wicking in micro-engineered structures accurately. In addition, the effects of pitch-to-diameter ratios of the micropillar are delineated, and analytical correlations based on the underlying physics are developed, which shows good agreement with the numerical and experimental study.