发表机构
Kogakuin University; University of Stuttgart; Leibniz Institute for Materials Engineering（工学馆大学; 斯图加特大学; 莱布尼茨材料工程研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过高速成像实验，发现聚合物浓度不影响液滴铺展但显著减缓回缩，并提出了标度模型统一描述不同韦伯数和浓度下的回缩动力学。
AI 中文摘要
假设：液滴中存在聚合物对液滴撞击固体基底后的接触线动力学起着重要作用。我们假设聚合物浓度会改变撞击后的润湿行为。实验：在我们的实验中，我们观察了含聚合物液滴撞击平坦蓝宝石基底时的接触线动力学。利用高速侧面和底部成像，我们在广泛的韦伯数（10-700）和聚环氧乙烷（PEO）浓度（0-400 ppm）范围内分析了液滴的铺展和回缩。为了系统地表征接触线动力学，我们使用图像处理来量化最大铺展因子、回缩速度和回缩接触角。发现：聚合物对铺展阶段的影响可忽略不计，因为最大铺展因子遵循经典的惯性-毛细标度，表明在当前条件下添加聚合物对最大铺展没有产生可测量的变化。相反，回缩阶段表现出对聚合物浓度的强烈依赖性：增加PEO含量导致回缩速度和动态接触角显著降低，而铺展动力学仍保持与水相似。这些结果与回缩接触线区域相关的额外阻力一致，而该阻力的微观起源仍未解决。为了捕捉这种行为，我们提出了一个标度模型，将归一化回缩速度与回缩接触角和撞击条件联系起来。该模型有效地将所有研究浓度和韦伯数下的实验数据进行了归一化。
英文摘要
Hypothesis: The presence of a polymer in a droplet plays a significant role in contact line dynamics following droplet impact onto a solid substrate. We hypothesize that the polymer concentration modifies the post-impact wetting behavior. Experiments: In our experiments, we visualize the contact line dynamics of polymer-laden droplets impacting onto a flat sapphire substrate. Using high-speed side and bottom-view imaging, we analyze droplet spreading and retraction over a broad range of Weber numbers (10-700) and polyethylene oxide (PEO) concentrations (0-400 ppm). To systematically characterize the contact line dynamics, we used image processing to quantify the maximum spreading factor, receding velocity, and receding contact angle. Findings: The effect of the polymer on the spreading phase is negligible, as the maximum spreading factor follows classical inertial-capillary scaling, showing that polymer addition produces no measurable change in the maximum spreading under the present conditions. In contrast, the receding phase exhibits a strong dependence on the polymer concentration: increasing the PEO content leads to a significant reduction in the receding velocity and dynamic contact angle, while the spreading dynamics remain water-like. These results are consistent with an additional resistance associated with the receding contact-line region, while the microscopic origin of this resistance remains unresolved. To capture this behavior, we propose a scaling model that relates the normalized retraction velocity to the receding contact angle and impact conditions. The model effectively collapses the experimental data across all investigated concentrations and Weber numbers.
