Particles floating at interfaces are commonly observed in nature, as well as in industrial processes. When the particles are non-Brownian particles, large deformations of the interface are created that induce long-ranged capillary interactions and lead to the formation of particle rafts with unique characteristics. In this review we discuss recent efforts in investigating particle raft formation and the role of the rafts’ own weight during dynamic clustering. Under specific conditions, these rafts can ultimately collapse and sink. When subjected to external or internal forces, the raft undergoes large deformations that test the mechanical characteristics of this interfacial composite material. It can behave as a continuous elastic sheet under compression, although its discrete nature can also trigger its fragmentation via interparticle interactions. Finally, armored droplets, drops covered by a protective shell of particles, can lose their integrity when submitted to dynamic deformations, resulting in the ejection of particles or the fracturing of the armor. Open questions to understand the properties of this material are highlighted and future research to understand the fundamental physics of particle rafts, the customization of the cluster formation, or the disassembly of this collective material is suggested.

中文翻译：

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粒子筏和装甲液滴

漂浮在界面上的颗粒在自然界以及工业过程中很常见。当颗粒是非布朗颗粒时，会产生界面的大变形，从而引起长程毛细管相互作用，并导致形成具有独特特征的颗粒筏。在这篇综述中，我们讨论了最近在研究粒子筏形成以及动态聚类过程中筏自身重量的作用方面所做的努力。在特定条件下，这些筏最终可能会倒塌并下沉。当受到外力或内力时，筏会发生较大的变形，从而测试这种界面复合材料的机械特性。它在压缩下可以表现为连续的弹性片，尽管其离散性质也可以通过颗粒间相互作用触发其破碎。最后，装甲液滴（被粒子保护壳覆盖的液滴）在受到动态变形时可能会失去完整性，导致粒子喷射或装甲破裂。强调了了解这种材料特性的开放性问题，并建议未来研究了解粒子筏的基础物理、簇形成的定制或这种集体材料的分解。