CAREER: Drop impact dynamics and fingering on thin liquid films

工程师、物理学家和公众都对水滴撞击刚性表面时形成的皇冠的美丽图像着迷。除了令人着迷的图像，液滴撞击、扩散、收缩和破裂在农业、喷墨和微电子印刷、喷涂、燃烧、能源产生和法医科学中具有广泛的技术意义。尽管有许多用途，但由于（a）表面张力、粘度、惯性和重力之间的复杂相互作用和（B）用精确控制的亚微米液体层涂覆表面的挑战，迄今为止对薄液体膜上的液滴冲击动力学还没有完全理解。微/纳米纤维的最新进展通过操纵流体-结构相互作用实现了这一点。该研究计划的主要目的是提供液滴对薄液膜的冲击的基本理解。该项目将包括紧密结合的教育和推广计划，包括在本科和研究生水平的多年学生辅导和社区推广，以激励，激励和丰富K-12学生的教育经验，通过两个主要的公共场所：密歇根大学自然历史博物馆和Xplore工程。研究计划的目标是使用实验和理论建模来开发一种全面了解液层厚度小于1微米的薄液膜上的液滴冲击动力学。使用最先进的微/纳米工程表面涂有已知厚度的润滑膜，研究计划研究跌落冲击动力学，主要目标有三个：1）理解当液滴冲击光滑且可变形的液膜时空气滞留的作用，该液膜的特征在于液滴和润滑剂涂层之间的液-液接触，2）识别环形润湿脊对指进和液滴破裂的作用，以及3）理解包围冲击的流体动力学不稳定性的根本原因以及从径向膨胀的液体薄层分叉的卫星液滴的数量。研究的目的是捕捉的密度和粘度之间的不匹配的液滴和润滑剂层的破碎机制的影响。通过结合高速可视化、荧光显微镜、白色光干涉测量法、反射干涉对比显微镜和平面激光诱导荧光，该奖项反映了美国国家科学基金会的法定使命，并被认为是值得通过使用基金会的智力价值和更广泛的影响评审进行评估来支持的的搜索.

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.