Enhanced Liquid Propagation and Wicking Along Nanostructured Porous Surfaces

The crucial role of capillary pumping has motivated recent innovations in porous wicking materials for many energy and environment applications. Herein, the wick-based liquid propagation along with a porous surface, including both macroscopic water transport behavior and microscopic wicking dynamics, with a group of nanostructured porous surfaces, is investigated. These hybrid wicking surfaces are fabricated in a scalable way by bonding copper micromeshes on flat surfaces and chemical etching. These nanostructured porous surfaces exhibit outstanding wickability by simultaneously improving surface hydrophilicity and minimizing viscous dissipation of water flow. Notably, the as-fabricated surfaces also have good thermal conductivity and high solar absorptance, which are desired properties for various solar thermal applications. To directly observe water propagation processes, infrared thermal imaging in locating the propagation front and evaluating water film thickness along the propagation direction is also demonstrated. The dynamic water vapor meniscus in a representative pore unit is captured and characterized through environmental scanning electron microscopy. A capillary pressure model and permeability model to predict the liquid propagation and wicking characteristics is then developed, resulting in good agreement with experimental results for a large variety of nanostructured porous surfaces.