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ERI: Incipient contact dynamics of viscoelastic drops

ERI：粘弹性液滴的初始接触动力学

基本信息

批准号：
2137341
负责人：
Min Pack
金额：
$ 20万
依托单位：
Baylor University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2022
资助国家：
美国
起止时间：
2022-07-01 至 2025-06-30
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2137341&HistoricalAwards=false
关键词：
ERI Incipient contact dynamics viscoelastic

项目摘要

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). Before a droplet moving through a gas can contact a solid surface, the gas between the droplet and surface must be displaced. If the displacement is incomplete, some of the gas may be entrained as small bubbles inside the drop. This process has been studied extensively for common systems such as water droplets moving through air that impact various kinds of solid surfaces. This ERI award focuses on how the contact dynamics change when the liquid drop contains polymer additives. The impact of polymer-laden drops on solid surfaces is relevant to many applications including bioprinting, pesticide formulation, and the deposition of pathogen-laden respiratory droplets on surfaces. The influence of polymer additives on air displacement underneath droplets will be examined using a combination of experiments and theory. A state-of-the-art rheometer and a high-speed optical technique that can track the approach of droplets nanometers from contact will be used to assess the air entrainment in droplets containing commercially-relevant polymers such as polyethylene oxide. Results from the project will provide useful information to engineering practioners who must control air entrainment to ensure product quality in various applications. Graduate and undergraduate students will participate in the research, and research results will be incorporated into undergraduate and graduate courses. The project will partner with the Mayborn Musuem on the Baylor campus to enhance existing outreach efforts aimed at communicating science to students of all ages and the general public.Air entrainment is a common industrial problem in inkjet printing and various coating processes. Although the fundamental hydrodynamics underlying air entrainment has generated broad interest, the problem remains challenging because it spans orders of magnitude in spatiotemporal dynamics. Efforts to uncover the incipient contact of droplets have focused mainly on droplets composed of Newtonian liquids even though important applications involve polymeric drops. In order to fill this knowledge gap, this ERI project will analyze nanometer- to millimeter-scale dynamics using experiments and theory to uncover the contact routes for polymer-laden drops. The research comprises three tasks: (1) investigate the influence of polymer additives on air entrainment phenomena; (2) characterize the energy loss caused by the entrained air film during droplet spreading; and (3) analyze strategies to control the air entrainment mechanism. The influence of polymer concentration on air entrainment and the roles of shear thinning and elasticity will be investigated using a combination of high-speed total internal reflection microscopy and rheometric measurements. The project will develop new experimental tools for assessing the viscoelasticity of polymer-laden droplets, which will benefit researchers studying interfacial phenomena and multiphase 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.

该奖项的全部或部分资金根据《2021 年美国救援计划法案》（公法 117-2）提供。在穿过气体的液滴接触固体表面之前，必须置换液滴和表面之间的气体。如果置换不完全，一些气体可能会以小气泡的形式夹带在液滴内。这一过程已针对常见系统进行了广泛研究，例如水滴在空气中移动，影响各种固体表面。该 ERI 奖项重点关注当液滴含有聚合物添加剂时接触动力学如何变化。载有聚合物的液滴对固体表面的影响与许多应用相关，包括生物打印、农药配方以及载有病原体的呼吸道飞沫在表面上的沉积。将结合实验和理论来研究聚合物添加剂对液滴下方空气置换的影响。最先进的流变仪和高速光学技术可以跟踪纳米级液滴接触的接近，将用于评估含有商业相关聚合物（例如聚环氧乙烷）的液滴中的空气夹带情况。该项目的结果将为必须控制空气夹带以确保各种应用中的产品质量的工程实践者提供有用的信息。研究生和本科生将参与研究，研究成果将纳入本科生和研究生课程。该项目将与贝勒校区的 Mayborn Musuem 合作，加强现有的宣传工作，旨在向所有年龄段的学生和公众传播科学知识。夹气是喷墨印刷和各种涂层工艺中常见的工业问题。尽管夹带空气的基本流体动力学引起了广泛的兴趣，但该问题仍然具有挑战性，因为它跨越了时空动力学的数量级。尽管重要的应用涉及聚合物液滴，但揭示液滴初始接触的努力主要集中在由牛顿液体组成的液滴上。为了填补这一知识空白，该 ERI 项目将利用实验和理论分析纳米到毫米级的动力学，以揭示载有聚合物的液滴的接触路径。该研究包括三项任务：（1）研究聚合物添加剂对夹气现象的影响； (2)表征液滴铺展过程中夹带气膜引起的能量损失； (3)分析夹气机制的控制策略。将结合高速全内反射显微镜和流变测量来研究聚合物浓度对空气夹带的影响以及剪切稀化和弹性的作用。该项目将开发新的实验工具来评估聚合物液滴的粘弹性，这将有利于研究界面现象和多相流体力学的研究人员。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。