Anti-condensation is important in various fields, e.g., transportation, power transmission, internal drying of precision instruments. Vapor sink is an important manner to suppress the happening of water vapor condensation, and shows potentials in some special scenarios. However, the mechanism of anti-condensation by vapor sink is not well understood up until now. In this article, the effect of substrate temperature on the dry zone generated by vapor sink were systematically studied with experiments and theoretical analysis. First, the effect of hygroscopic solutions on the local humidity were measured. The results indicated that the local humidity level near the hygroscopic solutions was effectively suppressed, reducing the water vapor condensation. Second, the variation of the dry zone with the cooling substrate temperature was systematically studied. The results indicated that the dry zone exhibits a hyperbolic relationship with the substrate temperature. The dry zone changing under different humidity conditions and cooling time were also studied. The dry zone remained approximately unchanged over time in a short period. Finally, a simple yet effective model between the dry zone and substrate temperature was deduced. The theoretical results are in good agreement with the experimental data. Our study may deeper the understanding of condensation suppression via vapor sink and offer guidance to the design of anti-condensation or anti-icing surfaces.
Efficient removal of condensation droplets from cooled superhydrophobic surfaces is pivotal for practical applications such as anti-icing, water collection, and condensation heat transfer. However, these surfaces often lose their superhydrophobicity as microdroplets become trapped within their structures during condensation, particularly under high supercooling conditions. Here, a fluorine-free superhydrophobic surface, fabricated via a facile one-step vapor deposition method, is introduced, featuring a hierarchical cauliflower-like structure. This design restricts condensation droplet size to a maximum diameter of ≈50 µm and a coverage rate of ≈16%, markedly enhancing droplet shedding efficiency, due to a hierarchical cauliflower-like structure enhances the larger Laplace force and smaller adhesion. Notably, the surface maintains stable superhydrophobicity even after 720 min of exposure to 100 °C vapor (supercooling of ≈99 °C), surpassing the durability of traditional superhydrophobic surfaces by two orders of magnitude, highlighting its efficacy in anti-condensation under extreme supercooling conditions. Beyond anti-condensation, this design demonstrates enhanced self-cleaning even via condensation droplets or for high-adhesive nanoparticles, eco-friendliness, and demonstrates robust durability, including thermal stability above 500 °C and anti-ultraviolet radiation, thereby broadening its potential for industrial applications in various harsh environments.
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