Spontaneous Uphill Movement and Self-Removal of Condensates on Hierarchical Tower-like Arrays.

Fast removal of condensates from surfaces is of great significance due to the enhanced thermal transfer coefficient and continuous condensation. However, the lost superhydrophobicity of lotus leaves intrigues us to determine what kind of surface morphologies meets the self-removal of condensates? The uphill movement of condensates in textured surfaces is vital to avoid flooding and facilitating self-removal. Here, superhydrophobic microtower arrays were designed to explore the spontaneous uphill movement and Wenzel to Cassie transition as well as the self-removal of condensates. The tower-like arrays enable spontaneous uphill movement of tiny condensates entrapped in microstructures due to the large upward Laplace pressure, which is ∼30 times larger than that on cone-like arrays. The sharp tips decrease the adhesion to suspending droplets and promote their fast self-removal. These results are important for designing desirable textured surfaces by enlarging upward Laplace pressure to facilitate condensate self-removal, which is widely applied in self-cleaning, antifogging, anti-icing, water harvesting, and thermal management systems.