CAREER: Drop impact dynamics and fingering on thin liquid films

工程师、物理学家和普通大众都被水滴撞击坚硬表面时形成的美丽的王冠图像所吸引。除了令人着迷的图像外，跌落的冲击、扩散、收缩和破裂在农业、喷墨和微电子印刷、喷涂、燃烧、能源生产和法医科学等领域具有广泛的技术意义。尽管有许多应用，但由于(a)表面张力、粘度、惯性和重力之间复杂的相互作用，以及(b)用精确控制的亚微米液体层涂覆表面的挑战，迄今为止，液滴对薄液体膜的冲击动力学尚未完全了解。微/纳米制造的最新进展通过操纵流固相互作用实现了这一点。该研究计划的主要目的是对液滴对液体薄膜的影响提供基本的理解。该项目将包括紧密结合的教育和推广项目，包括在本科和研究生阶段的多年学生指导，以及通过两个主要公共场所（密歇根大学自然历史博物馆和探索工程）激励、启发和丰富K-12学生的教育经验的社区推广。该研究计划的目标是利用实验和理论建模来全面了解液滴对液体薄膜的冲击动力学，其中液体层厚度小于1微米。使用最先进的微/纳米工程表面涂有已知厚度的润滑膜，研究项目研究跌落冲击动力学有三个主要目标：1)了解液滴撞击光滑、可变形的液膜时空气夹持的作用，液滴与润滑剂涂层液液接触，2)确定环形润湿脊对指指和液滴破裂的作用，3)了解撞击引起的流体动力不稳定性的根本原因以及从径向膨胀的液层中分叉的卫星液滴的数量。该研究旨在捕捉液滴与润滑层之间的密度和粘度不匹配对破裂机理的影响。结合高速可视化、荧光显微镜、白光干涉法、反射干涉对比显微镜、平面激光诱导荧光等方法，本研究有望在软物质物理和流体力学领域产生新的知识，并指导未来的研究。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。

Engineers, physicists, and the general public have been fascinated by the beautiful images of the crown that forms when a drop impacts a rigid surface. Besides the mesmerizing images, drop impact, spreading, retraction, and breakup has broad technological implications in agriculture, inkjet and microelectronics printing, spray coating, combustion, energy generation, and forensic science. Despite the many utilities, drop impact dynamics on thin liquid films is not fully understood to date due to (a) the complex interplay between surface tension, viscosity, inertia, and gravity and (b) the challenge of coating surfaces with precisely controlled sub micrometer liquid layers. Recent advances in micro/nanofabrication have enabled this by manipulating fluid-structure interaction. The principal aim of the research program is to provide fundamental understanding of drop impact on thin liquid films. The project will encompass closely integrated education and outreach programs including multi-year student mentoring at the undergraduate and graduate levels and a community outreach to motivate, inspire, and enrich the educational experience of K-12 students through two major public venues: University of Michigan Museum of Natural History and Xplore Engineering.The goal of the research program is to use experiments and theoretical modeling to develop a comprehensive understanding of drop impact dynamics on thin liquid films where the liquid layer thickness is less than one micron. Using state-of-the-art micro/nanoengineered surfaces coated with a lubricant film of known thickness, the research program investigates drop impact dynamics with three principal objectives: 1) understanding the role of air entrapment when a drop impacts a smooth and deformable liquid film featuring liquid-liquid contact between the drop and the lubricant coating, 2) identifying the role of the annular wetting ridge on fingering and drop breakup, and 3) understanding the root cause of the hydrodynamic instability that ensues impact and the number of satellite drops that bifurcate from the radially expanding liquid lamella. The research aims to capture the effects of density and viscosity mismatch between the drop and the lubricant layer on the breakup mechanism. By combining high-speed visualization, fluorescence microscopy, white light interferometry, reflection interference contrast microscopy, and planar laser-induced fluorescence, the proposed research is expected to produce new knowledge and guide future research in soft matter physics and fluid mechanics.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.