Nanoengineered surfaces offer new possibilities to manipulate fluid transport and enhance heat dissipation characteristics for the development of efficient energy systems. In particular, nanostructures on these surfaces can be harnessed to achieve superhydrophilicity and superhydrophobicity, and to control liquid behavior and phase-change processes. In this work, we will describe recent developments focused on using superhydrophilic nanostructure design to manipulate liquid spreading behavior and directionalities. In the presence of asymmetric nanopillars, uni-directional spreading of water droplets can be achieved where the liquid spreads only in the direction of the pillar deflection and becomes pinned on the opposite interface. In the presence of fine features on the pillars, we observed a multi-layer spreading effect due to their associated energy barriers. For both cases, we have developed energy-based models to accurately predict the liquid behavior as functions of pertinent parameters. Furthermore, we developed a semi-analytical model to predict liquid propagation rates in pillar arrays driven by capillarity. The results offer design guidelines to optimize propagation rates for fluidic wicks. These investigations offer insights and significant potential for the development and integration of advanced nanostructures to achieve efficient energy conversion systems.

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