Understanding the anti-icing behavior of superhydrophobic surfaces

Superhydrophobic surfaces (SHS) are promising nature-inspired materials in low-temperature-condition applications to resist frost, ice, snow and water drop freezing. However, other observations bring into question the advantage of using SHS. In particular, the water supercooling phenomenon and the lack of characterization methods make it difficult to understand icing phenomena on SHS. Here, the authors bring about clarity by measuring water kinetic freezing points on surfaces of various wettabilites through differential scanning calorimetry technique. It is shown that under relatively dry environment, the freezing delay on cold surfaces is attributed to the water-freezing-point depression, which is determined by the combined effect of surface chemistry and roughness. In addition, drop-freezing tests using a thermoelectric cooler under humid atmosphere showed that the freezing delay is dependent on the frosting, as well. Frost crystals growing on the cold surface will act as nucleus initiating drop freezing. The results of this study provide new insights into the mechanism responsible for the drop-freezing delay on SHS. This article contains supporting information that is available online.