![]() Bubble freezing under isothermal conditionsįigure 2 shows the remarkable multistep freezing process that occurs under isothermal conditions, over a timescale of \( \sim 1\) μm 8, t d~10 3 s being the drainage timescale of a centimetric bubble, which was experimentally observed (Supplementary Fig. Given that the soap solution is 80% water, we approximate the density (and all other thermophysical properties besides T m) as that of pure water: ρ ≈ 1000 kg m −3. Where γ = 24.2 mN m −1 is the solution’s surface tension measured by using the pendant drop method and waiting until the surfactant had reached a steady-state packing density at the free interface (Supplementary Fig. Conversely, when bubbles are deposited on a chilled icy substrate in room-temperature conditions, the bottom-up freeze front comes to a halt midway up the bubble due to poor conduction. For bubbles freezing in an isothermal environment, the bottom-up freeze front produces a Marangoni flow that detaches ice crystals, resulting in accelerated freezing from multiple fronts growing in tandem. Two different types of freezing dynamics were observed, depending on the experimental conditions. Inspired by these informal observations of freezing bubbles, here we characterize the heat transfer phenomena governing the dynamics of freezing bubbles over a wide range of conditions. Therefore, the extensive studies of how droplets 18, 19, 20, 21, 22, 23, 24, 25 or films 26, 27, 28 freeze cannot capture the physics of bubble freezing. These dynamics are nontrivial owing to the unique geometry of a bubble: unlike droplets, puddles, or surface-bound liquid films, bubbles do not have a thermally conductive bulk volume. In the field of visual arts, on the other hand, there is an emerging trend of photographers capturing beautiful videos of the complex freezing dynamics of bubbles deposited on snow (e.g., see ). Washington and commented on the number and shape of ice crystals contained therein 17. In 1949, Shaefer observed bubbles freezing atop Mt. This has culminated in the practical use of bubbles for a myriad of applications such as energy harvesting 12, drug delivery 13, and cleaning devices 14, 15, 16.ĭespite this prolonged attention lavished on bubbles, there exists only a brief scientific report of freezing. Building on this foundation, in modern times, the behavior of bubbles from their birth 5, 6, wetting 7, drainage and evaporation 8, 9, to their fatal bursting 10, 11 has been comprehensively studied. ![]() Their influence can be traced in a historical arc that includes Babylonian divination rituals (lecanomancy) to Impressionist paintings to the works of physicists such as Newton, Plateau, and de Gennes 1, 2, 3, 4. Soap bubbles and films have been a source of intrigue for millennia.
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