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arXiv · 2511.20571

X-ray Microscopy Study of Freezing Sessile Droplets

Jae Kwan Im·Hyeonjun An·Seob-Gu Kim·Jae-Hong Lim·Joonwoo Jeong
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Abstract

A sessile water droplet on a cold substrate freezes into a shape with a sharp apex because of water's expansion upon freezing, yielding a universal tip angle across various conditions. Using \textit{in situ} X-ray imaging, we report that this angle changes with substrate temperature, and the deviation originates from bubble formation during freezing. Three-dimensional tomography enables direct quantification of the effective ice-water density ratio, accounting for trapped bubbles. Incorporating this effective density ratio reconciles the temperature-dependent tip angles. We also confirm that a bubble-free frozen droplet in a vacuum chamber exhibits the universal tip angle. Furthermore, X-ray imaging allows us to measure the three-phase boundary angles \textit{in situ}, thereby validating the geometric theory behind tip formation. These findings advance our understanding of the freezing dynamics associated with multiphase systems and highlight the capabilities of high-resolution X-ray imaging in ice research.

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Jae Kwan Im, Hyeonjun An, Seob-Gu Kim, Jae-Hong Lim, Joonwoo Jeong. 2025-11-25. X-ray Microscopy Study of Freezing Sessile Droplets. https://arxiv.org/abs/2511.20571

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