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Rationally Designed Nanostructure Features on Superhydrophobic Surfaces for Enhancing Self-Propelling Dynamics of Condensed Droplets

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posted on 31.12.2018, 00:00 by Yizhou Shen, Yuehan Xie, Jie Tao, Haifeng Chen, Chunling Zhu, Mingming Jin, Yang Lu
The self-propelling ability toward achieving more efficient dropwise condensation intensively appeals to researchers due to its academic significance to explain some basic wetting phenomena. Herein we designed and fabricated the two types of microstructure superhydrophobic surfaces, i.e., sealed layered nanoporous structures (SLP-surface) and open nanocone structures (OC-surface). As a consequence, the resultant surfaces exhibit the robust water repellency, and the water droplet nearly suspends on the superhydrophobic surfaces (CA = 158.8° ± 0.5°, SA = 4° ± 0.5° for the SLP-surface and CA = 160.2° ± 0.4°, SA = 1° ± 0.5° for the OC-surface, respectively). Meanwhile, the impacting droplets can be rapidly rebounded off with a shorter contact time of 11.2 and 10.4 ms (impact velocity V0 = 1 m/s). The excellent static-dynamic superhydrophobicity is mainly attributed to the air pockets captured by both microscopic rough structures. Regarding the self-propelling ability of condensed droplets, it is found that the droplet microscopic pinning effect of the SLP-surface severely weakens the dynamic self-propelling ability of condensed droplets. The capillary adhesive force induced by the sealed layered nanoporous structures is up to 16.0 μN. However, the open nanocone structures cause lower water adhesive force (∼4.1 μN) under the action of flowing air pockets, producing a higher dynamic self-propelling ability of condensed droplets. As a consequence, the open nanocone structure superhydrophobic surface displays a huge potential of inhibiting attachment of condensed droplets.