Surface structure repels water droplets at room temperature, ice at colder temperatures
DOI: 10.1063/10.0005139
Surface structure repels water droplets at room temperature, ice at colder temperatures lead image
Anti-icing research in various industrial contexts has grown rapidly for economic reasons, because ice can down power lines, reduce the working efficiency of wind-turbine blades and impacts the safety of aircrafts. Liao et al. invented a surface structure that can successfully repel water droplets at room temperature and with a high Weber number under surface temperature at -20C.
To create the surface, the researchers improved the fabrication process by reducing the cell size from over 100 micrometers to only 15 micrometers. They found the ratio of pitch distance and microstructure height is the most important parameter to control droplet dynamics and heat transfer.
To design a proper doubly reentrant cavity structure that would achieve promising hydrophobicity and icephobicity, the researchers tested a set of samples with different structure parameters to find the best structure size and revealed the mechanism behind the repelling ability. Theoretical analysis showed air inside the microcavity, a type of “air spring,” not only provided extra repelling force but also increased the local temperature when the droplet impacted the sample and helped achieve icephobicity.
“It was surprising that the transient air temperature change in the air cavity during the droplet impact can be over 100 degrees Cesius,” said coauthor Huihe Qiu.
“This temperature change may significantly affect the performance in dynamic icephobicity,” said coauthor Dong Liao.
In addition to anti-icing surfaces, another potential application of this research is for flow drag reduction utilizing air plastron of the surface. Since the doubly reentrant cavity has been approved to demonstrate excellent droplet repelling conditions, it might be possible to utilize the new surface for underwater vehicles.
Source: “Droplet impact dynamics and heat transfer on nanostructured doubly reentrant cavity under freezing temperature,” by Dong Liao, Yinchuang Yang, and Huihe Qiu, Physics of Fluids (2021). The article can be accessed at https://doi.org/10.1063/5.0050400 .
