Spontaneous removal of liquid, solidifying liquid and solid forms of matter from surfaces, is of significant importance in nature and technology, where it finds applications ranging from self-cleaning to icephobicity and to condensation systems. However, it is a great challenge to understand fundamentally the complex interaction of rapidly solidifying, typically supercooled, droplets with surfaces, and to harvest benefit from it for the design of intrinsically icephobic materials. Here we report and explain an ice removal mechanism that manifests itself simultaneously with freezing, driving gradual self-dislodging of droplets cooled via evaporation and sublimation (low environmental pressure) or convection (atmospheric pressure) from substrates. The key to successful self-dislodging is that the freezing at the droplet free surface and the droplet contact area with the substrate do not occur simultaneously: The frozen phase boundary moves inward from the droplet free surface toward the droplet–substrate interface, which remains liquid throughout most of the process and freezes last. We observe experimentally, and validate theoretically, that the inward motion of the phase boundary near the substrate drives a gradual reduction in droplet–substrate contact. Concurrently, the droplet lifts from the substrate due to its incompressibility, density differences, and the asymmetric freezing dynamics with inward solidification causing not fully frozen mass to be displaced toward the unsolidified droplet–substrate interface. Depending on surface topography and wetting conditions, we find that this can lead to full dislodging of the ice droplet from a variety of engineered substrates, rendering the latter ice-free.

中文翻译：

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冻结水滴的自发自流性和润湿性的作用

自发地从表面去除液体，固化液体和固体形式的物质，在自然和技术中具有重要意义，在自然和技术中，其应用范围从自清洁到憎冰性以及冷凝系统。然而，从根本上理解快速凝固的，通常是过冷的液滴与表面之间的复杂相互作用，并从中收获本质上用于疏冰材料的设计，这是一个巨大的挑战。在这里，我们报告并解释了一种除冰机制，该机制与冻结同时显现，并通过从基板蒸发和升华（低环境压力）或对流（大气压）来驱动冷却的液滴逐渐自移。成功实现自溶的关键在于，液滴自由表面和液滴与基材的接触区域不会同时发生冻结：冻结的相界从液滴自由表面向内移向液滴-基质界面，该界面保持液态在整个过程的大部分时间内都冻结了。我们通过实验观察，并在理论上进行验证，即基板附近的相界向内运动会导致液滴与基板之间的接触逐渐减少。同时，由于其不可压缩性，密度差异以及向内凝固的不对称冻结动力学，液滴从基底上升起，导致未完全凝固的团块移向未凝固的液滴-基底界面。根据表面形貌和润湿条件，