Experimental investigation on the impacting and freezing characteristics of water droplets on a PDMS-decorated superhydrophobic aluminum alloy surface

Abstract

Due to the potential applications of superhydrophobic surfaces in water-repelling and anti-icing, it is of great interest to study the impacting and freezing processes of water droplets on superhydrophobic surfaces. In this study, the process of a water droplet impacting the PDMS-decorated superhydrophobic aluminum alloy (denoted as Al-PDMS) surface was studied, and the influences of a water droplet falling height and volume were systemically investigated with a high-speed camera. The results indicate that the impacting process can be categorized into four states, which are mainly affected by the dropping height. The bouncing processes of water droplets on horizontal superhydrophobic surfaces are studied by defining spreading factor α and rebounding factor β. Furthermore, the effect of the inclination angle φ of the superhydrophobic plate on the impacting behavior was investigated. The freezing processes of water droplets on superhydrophobic surfaces were also studied. The results showed that the delayed-icing time decreases with decreasing test plate temperature. Additionally, the volume and height of the frozen portion of the water droplets during freezing were investigated, and the movement characteristic of the freezing front was analyzed.

Numerical investigation of the freezing property of impinging water droplets on inclined cold superhydrophobic surfaces

“…The contact point position on the front side is maintained for a while after reaching the maximum spreading state and then increases continuously and slowly. This indicates that the impinging water droplet is sliding on the inclined surface, which is in agreement with what was reported in the previous study [36]. The variation trend in contact point position on the receding side at γ = 45°i s the same as that for the first two cases, and only the maximum continues to decrease.…”

“…Ding et al [34,35] experimentally discovered that the rebound of water droplets can be facilitated by increasing the surface inclination angle. Peng et al [36] discovered that on superhydrophobic surfaces with inclination angles of 30°a nd 45°, water droplets are less likely to break up after impingement and instead slide down the surface before bouncing off. Zhang et al [37] discovered that the freezing time of impinging water droplets was longest on a hydrophilic titanium surface with an inclination angle of 45°.…”

Correlation between the optical and microstructural characteristics and surface wettability transition of In2O3:Sn/ZnO nanostructured bilayer system for self-cleaning application

“…If the contact angle exceeds 90°, this signifies low wettability and hydrophobic behavior. On the other hand, when the contact angle is equal to or greater than 150°, the solid surface is called superhydrophobic [57,58]. Figures 12(S1)-(S5), left indicates a notable increase in surface hydrophobicity upon increasing the annealing temperature from 400 to 500 °C.…”