The interplay between thin film hydrodynamics and solidification produces formidably intricate geophysical structures, such as stalactites and icicles, whose shape is a testimony of their long growth. In simpler settings, liquid films can also produce regular patterns. When coated on the underside of a flat plate, these films are unstable and yield lattices of drops following the Rayleigh-Taylor instability. While this interfacial instability is well-studied in Newtonian fluids, much less is known about what happens when the thin film solidifies. Here, we coat the underside of a surface with liquid elastomer, allowing the film to destabilize and flow while it cures into an elastic solid. Once the first coating yields an array of solid droplets, this iterative coat-flow-cure process is repeated and gives rise to corrugated slender structures, which we name “flexicles” for their resemblance to icicles. We study the subtle combination of chaos and order that confers our flexicles their structure, shape, arrangement, and, ultimately, deformability.

中文翻译：

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堆叠的 Rayleigh-Taylor 不稳定性使液滴生长成柔软的钟乳石状结构


薄膜流体动力学和凝固作用之间的相互作用产生了极其复杂的地球物理结构，例如钟乳石和冰柱，其形状证明了它们的长期生长。在更简单的设置中，液体薄膜也可以产生规则的图案。当涂覆在平板的底面时，这些薄膜不稳定，并在 Rayleigh-Taylor 不稳定性后产生液滴晶格。虽然这种界面不稳定性在牛顿流体中得到了很好的研究，但人们对薄膜凝固时会发生什么知之甚少。在这里，我们在表面的底面涂上液体弹性体，使薄膜在固化成弹性固体时不稳定和流动。一旦第一涂层产生一系列固体液滴，就会重复这种迭代的涂层-流动-固化过程，并产生波纹状的细长结构，我们将其命名为“弹性柱”，因为它们与冰柱相似。我们研究混乱与秩序的微妙结合，这些结合赋予了我们的 Flexicles 的结构、形状、排列，并最终赋予了可变形性。