The evaporation of a sessile droplet spontaneously induces an internal capillary liquid flow. The surface-tension driven minimisation of surface area and/or surface-tension differences at the liquid-gas interface caused by evaporation-induced temperature or chemical gradients set the liquid into motion. This flow drags along suspended material and is one of the keys to control the material deposition in the stain that is left behind by a drying droplet. Applications of this principle range from the control of stain formation in the printing and coating industry, to the analysis of DNA, to forensic and medical research on blood stains, and to the use of evaporation-driven self-assembly for nanotechnology. Therefore, the evaporation of sessile droplets attracts an enormous interest from not only the fluid dynamics, but also the soft matter, chemistry, biology, engineering, nanotechnology and mathematics communities. As a consequence of this broad interest, knowledge on evaporation-driven flows in drying droplets has remained scattered among the different fields, leading to various misconceptions and misinterpretations. In this review we aim to unify these views, and reflect on the current understanding of evaporation-driven liquid flows in sessile droplets in the light of the most recent experimental and theoretical advances. In addition, we outline open questions and indicate promising directions for future research.

中文翻译：

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固着液滴中蒸发驱动的液体流动

固着液滴的蒸发自发地引起内部毛细液体流动。由蒸发引起的温度或化学梯度引起的液体-气体界面处表面积和/或表面张力差异的表面张力驱动最小化使液体开始运动。这种流动会拖曳悬浮材料，是控制干燥液滴留下的污渍中材料沉积的关键之一。这一原理的应用范围从控制印刷和涂料工业中的污渍形成，到 DNA 分析，到血渍的法医和医学研究，以及在纳米技术中使用蒸发驱动的自组装。因此，固着液滴的蒸发引起了流体动力学和软物质的极大兴趣，化学、生物学、工程、纳米技术和数学社区。由于这种广泛的兴趣，关于干燥液滴中蒸发驱动流动的知识仍然分散在不同的领域，导致各种误解和误解。在这篇综述中，我们旨在统一这些观点，并根据最新的实验和理论进展反思目前对固着液滴中蒸发驱动的液体流动的理解。此外，我们概述了未解决的问题并指出了未来研究的有希望的方向。导致各种误解和误解。在这篇综述中，我们旨在统一这些观点，并根据最新的实验和理论进展反思目前对固着液滴中蒸发驱动的液体流动的理解。此外，我们概述了未解决的问题并指出了未来研究的有希望的方向。导致各种误解和误解。在这篇综述中，我们旨在统一这些观点，并根据最新的实验和理论进展反思目前对固着液滴中蒸发驱动的液体流动的理解。此外，我们概述了未解决的问题并指出了未来研究的有希望的方向。