Melting expectations of ice droplet geometry
DOI: 10.1063/10.0043022
Melting expectations of ice droplet geometry lead image
Taking a winter flight out of Chicago or Boston often involves a time-consuming de-icing procedure. Designing better aircraft, along with other structures like wind turbines, to resist ice accumulation first requires an understanding of how ice droplets melt.
Cui et al. took high-speed recordings of ice droplets melting on different substrates to study the droplets’ geometries. While the ice layer typically rose to the droplet’s top in an expected pathway dubbed “floating mode,” the unmelted ice layer occasionally stayed at the bottom in a surprising “deposited mode.”
“Many people study experimental droplet freezing,” said author Zhizhao Che. “Not many people study the melting process, but we know it’s very important.”
The researchers first froze water droplets to -10 C on a substrate of either copper or a superhydrophobic material. Then, they slowly heated the substrate to 30 C, taking real-time photographs with a high-speed camera. To study fluid flow within the droplet, the team added a polystyrene particle with a similar density to water that fluoresced under a specific wavelength from an overhead laser lens.
The researchers accurately hypothesized that the droplets would melt most often in the floating mode because of ice’s lower density than water. But on superhydrophobic surfaces, they discovered the infrequent deposited mode. Here, they hypothesize that a thin layer of liquid forms between the droplet and the heated substrate, then flows upward to melt the droplet from the top down.
“This [is] counterintuitive,” said Che. “If you don’t see it, you don’t believe it.”
The researchers hope their findings can lead to better hydrophobic surfaces that encourage the deposited mode, which melts faster than the floating mode.
Source: “A melting mode of frozen sessile droplets with unmelted ice layer deposited at the bottom,” by Jiawang Cui, Yugang Zhao, Tianyou Wang, and Zhizhao Che, Applied Physics Letters (2026). The article can be accessed at https://doi.org/10.1063/5.0290513 .
