The control of microdroplet impact on superhydrophobic surfaces (SHSs) is becoming imperative owing to its effect on several industrial applications, such as corrosion protection, self-cleaning, ice resisting, and de-icing. While most of the experimental studies on the impact dynamics of droplets are based on macrodroplets, it is unclear how the obtained results can be applied to microdroplet impact on SHSs. In this work, a comprehensive experimental analysis ranging from millimeter- to micrometer-sized droplets using a novel drop on demand microdispensing system is performed. Several SHSs were synthesized to control droplet impact by enforcing bouncing on the surface during the impingement process. The current analysis focuses on experimentally capturing and analyzing the impact behavior of cloud-sized microdroplets and macrodroplets (D₀ = 10 μm–2500 μm) upon SHS impact, with hysteresis, under controlled environmental conditions. Different droplet impact parameters, such as droplet contact time, maximum spreading diameter, and restitution coefficient, were experimentally obtained. Interestingly, this investigation highlighted a contrast in the behavior of microdroplets and macrodroplets upon impact on rough SHSs. It was found that critical parameters controlling droplet dynamics, such as the maximum spreading diameter and coefficient of restitution, cannot be described by current models in the literature. A preliminary theoretical model based on energy balance and accounting for the substrate hysteresis is proposed to explain some of these findings. Finally, the effect of SHS roughness on the bouncing of cloud-sized microdroplets (D₀ = 10 μm–100 μm) was examined in the context of synthesizing SHSs.

中文翻译：

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在超疏水表面上弹起云朵大小的微滴

由于微滴对多种工业应用（例如腐蚀防护，自清洁，抗冰和除冰）的影响，因此控制微滴对超疏水表面（SHS）的影响变得势在必行。尽管大多数有关液滴冲击动力学的实验研究都是基于大液滴，但尚不清楚如何将所得结果应用于微液滴对SHS​​的影响。在这项工作中，使用新颖的按需滴液微分配系统进行了从毫米级到微米级液滴的全面实验分析。合成了几种SHS，通过在撞击过程中在表面上弹跳来控制液滴的撞击。当前的分析着重于实验性地捕获和分析云大小的微滴和大滴的影响行为（d ₀ = 10 μ M-2500 μm）在受控的环境条件下，受到SHS的影响并具有滞后性。通过实验获得了不同的液滴冲击参数，例如液滴接触时间，最大散布直径和恢复系数。有趣的是，这项研究突出了微滴和大滴在对粗糙的SHS产生影响时的行为差异。已经发现，控制液滴动态的关键参数，例如最大散布直径和恢复系数，不能用文献中的当前模型来描述。提出了一个基于能量平衡和考虑基底滞后的初步理论模型来解释这些发现。最后，SHS粗糙度对云状微滴弹跳的影响（D ₀ = 10μ M-100 μ M）在合成松石的上下文中进行了研究。