EAGER: Unravelling the Spatiotemporal Dynamics of Three-Phase Contact Line on Soft Surfaces by Transmission X-Ray Microscopy

一个多世纪以来，理解和控制影响和扩散在固体表面上的液滴的复杂动力学一直吸引着科学家，因为这些现象在广泛的技术领域有潜在的应用，包括燃料燃烧、喷涂、农药沉积和喷墨打印。然而，大多数研究都考虑了在具有均匀纹理的刚性合成表面上的冲击和扩散，例如，在大多数生物系统中，情况并非如此。因此，预测液滴撞击软表面的行为和结果仍然具有挑战性，这主要是由于发生在液滴边缘和三相（固体-液体-空气）接触区的动态过程的复杂性。这个EAGER项目的目标是揭示控制软基板上接触线动力学的基本机制。为了检查接触线运动的细节，研究人员将使用超快透射x射线显微镜（TXM）。作为一种强大的非破坏性工具，TXM将通过成像多相地形和不透明介质中的传输来提供前所未有的空间和时间分辨率。这个项目的成果将对各个领域产生广泛的影响。来自这个项目的新研究机会将与西维吉尼亚州代表性不足的大学生和高中生的教育努力相结合。软表面上三相接触线动力学是一个普遍存在的过程，其机理具有重要的科学和技术意义。TXM提供了前所未有的时间和空间分辨率，具有边缘增强能力的相衬，以及超高的无损穿透性，可以检测软材料的三相接触线动力学。将制造具有良好柔韧性和弹性的软基板。液滴撞击动力学将用TXM进行检测。通过可视化接触线拓扑结构并跟踪其动态演变，揭示了复杂、流动、多相和软液固界面的液滴界面动力学，包括弹粘效应、接触线摩擦和耗散。通过对可能被困在推进接触线下的空气纳米泡的成像，揭示了接触线滑移的机理。所提出的努力不仅可以促进我们对软表面多相界面传输的潜在物理特性的理解，而且还为开发新型仿生界面材料开辟了新的途径，并为控制液滴撞击行为改变弹粘特性提供了指导。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Understanding and controlling the complex dynamics of liquid droplets that impact and spread over solid surfaces has intrigued scientists for more than a century because of the potential applications these phenomena have in broad areas of technology, including fuel combustion, spray coating, pesticide deposition, and inkjet printing. However, most research has considered impact and spreading over rigid synthetic surfaces with uniform textures, which is not the case, for example, in most biological systems. As a result, it remains challenging to predict the behaviors and outcomes of droplet impact on soft surfaces, mainly due to the complexity of the dynamic processes that occur at the droplet rim and the three-phase (solid-liquid-air) contact zone. The goal of this EAGER project is to uncover the fundamental mechanisms that govern contact line dynamics on soft substrates. To examine the details of contact line motion, the researchers will use ultrafast transmission X-ray microscopy (TXM). As a powerful and non-destructive tool, TXM will provide unprecedented spatial and temporal resolutions by imaging multiphase topography and transport in otherwise opaque media. The outcome of this project will have a broad impact on a variety of fields. New research opportunities from this project will be integrated with educational endeavours involving underrepresented college students and high school students in western Virginia. Three-phase contact line dynamics on soft surfaces is a ubiquitous process, and its underlying mechanism is of significant scientific and technological importance. TXM offers unprecedented temporal and spatial resolutions, phase-contrast with the edge-enhancement capability, and ultrahigh and nondestructive penetrability to examine three-phase contact line dynamics on soft materials. Soft substrates with well-characterized flexibility and elasticity will be fabricated. Liquid droplet impact dynamics will be examined with TXM. By visualizing contact line topology and tracking its dynamic evolution, droplet interfacial dynamics including elasto-viscous effects, contact line friction and dissipation on soft surfaces will be revealed for complex, mobile, multiphase and soft liquid-solid interfaces. By imaging the air nanobubbles that may be trapped under an advancing contact line, the mechanism of contact line slip may be revealed. The proposed efforts could not only advance our understanding of the underlying physics governing multiphase interfacial transport on soft surfaces, but also open a new avenue to developing novel bio-inspired interfacial materials and provide guidelines on modifying elasto-viscous properties for controlling droplet impact behaviors.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.