Research into evaporating droplets on patterned surfaces has grown exponentially, since the capacity to control droplet morphology has proven to have significant technological utility in emerging areas of fundamental research and industrial applications. Here, we incorporate two interest domains — complex wetting patterns of droplets on structured surfaces and the ubiquitous coffee-ring phenomenon of nanofluids containing dispersed aluminium oxide particles. We lay out the surface design criteria by quantifying the effect of pillar density and shape on the wetting footprint of droplets, yielding complex polygon droplet geometries. Our work is not constrained to pure liquids only, as we delve into the shape selection of particle-laden droplets of different concentrations. We visualise the deposition patterns through microscopy on surfaces exhibiting different features and further establish the ordering of particles on microscale surface asperities. At a high nanofluid concentration, we observe intriguing self-assembly of particles into highly ordered intricate structures. The collective findings of this work have the potential to enhance many industrial technologies, particularly attractive for high performance optical and electrical devices.

中文翻译：

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微结构表面上的几何沉积

由于已证明控制液滴形态的能力在基础研究和工业应用的新兴领域中具有重要的技术实用性，因此对图案化表面上的液滴蒸发的研究呈指数增长。在这里，我们结合了两个关注域-结构化表面上的液滴的复杂润湿模式以及包含分散的氧化铝颗粒的纳米流体的普遍存在的咖啡环现象。我们通过量化柱密度和形状对液滴的润湿足迹的影响来设计表面设计标准，从而产生复杂的多边形液滴几何形状。我们的工作不仅限于纯液体，因为我们研究了不同浓度的颗粒状液滴的形状选择。我们通过显微镜观察显示出不同特征的表面上的沉积图案，并进一步建立了微米级表面凹凸不平的颗粒排列。在高纳米流体浓度下，我们观察到有趣的粒子自组装成高度有序的复杂结构。这项工作的共同发现有潜力增强许多工业技术，特别是对高性能光学和电气设备具有吸引力。