Can superhydrophobic surfaces repel hot water?

作者：Yuyang Liu, Xianqiong Chen, John Haozhong Xin · 发表于：Journal of Materials Chemistry · 年份：2009 · DOI：10.1039/b822168e · 被引用次数：239 · 研究领域：Surface Modification and Superhydrophobicity、Advanced Sensor and Energy Harvesting Materials、Aerosol Filtration and Electrostatic Precipitation

Superhydrophobic surfaces that can repel hot liquids stand for a new generation of self-cleaning surfaces with broad applications. However, can current existing superhydrophobic surfaces repel hot water? In this paper, the repellent characteristics of current existing superhydrophobic surfaces to hot water (50–80 °C) were investigated. Representative superhydrophobic surfaces from lotus leaves, Teflon, silica–fluoropolymer composites and sol–gel processes were fabricated on silicon wafers and their repellency to hot water was evaluated based on water-contact angle (WCA) measurements and water uptake. These so-called superhydrophobic surfaces, which usually exhibit high repellency to cool water (around 25 °C), however, show remarkably decreased repellency to hot water. This may be attributed to a decrease of surface tension when the temperature of water increases and the lower surface tension of hot water makes it a better “wetting agent” to get into the pores and fissures of rough surfaces rather than bridging them with surface tension. According to the theories of surface wettability, the wetting state of water droplets on superhydrophobic surfaces can be described as Cassie–Baxter and Wenzel states, respectively. Superhydrophobic surfaces lose their high repellency to hot water due to the transition of the wetting state from Cassie–Baxter state to Wenzel state. Surface roughness, which is usually used for improving surface hydrophobicity, however, is found to improve the we...