Jereb Samo, Berce Jure, Lovšin Robert, Zupančič Matevž, Može Matic, Golobič Iztok
Faculty of Mechanical Engineering, University of Ljubljana, Aškerčeva cesta 6, SI-1000 Ljubljana, Slovenia.
Biomimetics (Basel). 2025 Jun 1;10(6):357. doi: 10.3390/biomimetics10060357.
The spreading and rebound of impacting droplets on superhydrophobic interfaces is a complex phenomenon governed by the interconnected contributions of surface, fluid and environmental factors. In this work, we employed a collection of 1498 water-glycerin droplet impact experiments on monolayer-functionalized laser-structured aluminum samples to train, validate and optimize a machine learning regression model. To elucidate the role of each influential parameter, we analyzed the model-predicted individual parameter contributions on key descriptors of the phenomenon, such as contact time, maximum spreading coefficient and rebound efficiency. Our results confirm the dominant contribution of droplet impact velocity while highlighting that the droplet spreading phase appears to be independent of surface microtopography, i.e., the depth and width of laser-made features. Interestingly, once the rebound transitions to the retraction stage, the importance of the unwetted area fraction is heightened, manifesting in higher rebound efficiency on samples with smaller distances between laser-fabricated microchannels. Finally, we exploited the trained models to develop empirical correlations for predicting the maximum spreading coefficient and rebound efficiency, both of which strongly outperform the currently published models. This work can aid future studies that aim to bridge the gap between the observed macroscale surface-droplet interactions and the microscale properties of the interface or the thermophysical properties of the fluid.
撞击液滴在超疏水界面上的铺展和反弹是一种复杂现象，受表面、流体和环境因素的相互作用影响。在这项工作中，我们对单层功能化激光结构化铝样品进行了1498次水 - 甘油液滴撞击实验，以训练、验证和优化机器学习回归模型。为了阐明每个影响参数的作用，我们分析了模型预测的各个参数对该现象关键描述符的贡献，如接触时间、最大铺展系数和反弹效率。我们的结果证实了液滴撞击速度的主要贡献，同时突出表明液滴铺展阶段似乎与表面微观形貌无关，即激光制造特征的深度和宽度。有趣的是，一旦反弹过渡到回缩阶段，未湿润面积分数的重要性就会增加，表现为在激光制造微通道间距较小的样品上具有更高的反弹效率。最后，我们利用训练好的模型开发了用于预测最大铺展系数和反弹效率的经验关联式，两者均明显优于目前已发表的模型。这项工作有助于未来旨在弥合观察到的宏观表面 - 液滴相互作用与界面微观性质或流体热物理性质之间差距的研究。
