Career Program: A Theoretical and Experimental Investigation of Novel Interfacial Instabilities in Thin Spreading Films

小行星9624776 与工艺和仪器小型化的技术推动相平行，人们对受限几何形状中的薄流体膜的行为产生了新的兴趣。 人们特别关注的问题是，在超小几何形状中的传输如何导致系统的行为方式与其在大体积中的行为明显不同。 在化学工程中，这一重点已经直接转化为对界面处液体结构和动力学的研究。 即使对于简单的牛顿液体，最近也发现了与表面张力、表面张力梯度、蒸发和货车德瓦尔斯力之间的相互作用有关的新的输运行为--这些力已经被研究了世纪，但是它们的耦合可以在非常薄的薄膜中导致有趣的和意想不到的不稳定性。 本研究的总体目标是对一种液体在支持液体表面上的扩散动力学有一个完整和基本的理解，特别关注稳定性问题。 第一个项目涉及的流体动力指进不稳定性的表征过程中发生的表面活性剂溶液沿着潮湿的支持。鉴于这个简单的实验室标记的影响，区分表面活性剂溶液提供稳定的均匀覆盖，从那些产生不稳定，树枝状，和不均匀的覆盖。 第二个不稳定性涉及Marangoni应力耦合蒸发效应。 一种新的指进不稳定性发展展向沿着增厚的后退边缘的挥发性烃类液体膜后退从散装水支持后，自发的空穴成核和增长。 了解如何防止这种不稳定性，可以导致一种新的技术，涉及马兰戈尼应力的烃类分离。 四年的实验和理论计划将表征这些不稳定性，这些不稳定性可以显着影响系统中的输运行为，从肺流中的表面活性剂输运，到光学微器件中使用的有机膜的制造，再到膜中碳氢化合物混合物的分离。 这两种类型的不稳定性和它们的特征图案形成在涂覆液体载体表面的薄液体膜的前进或后退前部处发展。 面临的挑战是充分表征的流动从液体力学的角度来看，更重要的是利用这方面的知识来开发实用的计划，以提高传输性能和减少不均匀的表面覆盖在薄的铺展膜。 这些计划的建议。 ***

9624776 Troian In parallel with the technological push toward miniaturization of processing and instrumentation, there has developed renewed interest in the behavior of thin fluid films in confined geometries. Particular attention is being drawn to the question of how transport in ultrasmall geometries can cause a system to behave in ways significantly different than its behavior in bulk. In chemical engineering this focus has translated directly into investigations of the structure and dynamics of liquids at interfaces. Even for the case of simple Newtonian liquids, novel transport behavior has been recently uncovered related to the interplay between surface tension, surface tension gradients, evaporation, and Van derWaals forces - forces which have been studied for over a century but whose coupling can lead to interesting and unexpected instabilities in very thin films. The general objective of this research is to develop a complete and fundamental understanding of the spreading kinetics of one liquid on the surface of a supporting liquid higher surface tension with particular focus on issues of stability. The first project involves the characterization of a hydrodynamic fingering instability which occurs during the advance of spreading surfactant solutions along a moist support. Given the implications of this simple laboratory marker to differentiate surfactant solutions providing stable homogeneous coverage from those yielding unstable, dendritic, and inhomogeneous coverage. The second instability involves Marangoni stresses coupled to evaporative effects. A novel fingering instability develops spanwise along the thickened receding edge of a volatile hydrocarbon liquid film receding from a bulk water support after spontaneous hole nucleation and growth. Understanding how to prevent such an instability can lead to a new technique for hydrocarbon separation involving Marangoni stresses. The four year experimental and theoretical program will characterize these instabilities wh ich can significantly affect transport behavior in system ranging from surfactant transport in pulmonary flow, to the fabrication of organic films used in optical microdevices, to the separation of hydrocarbon mixtures in the films. These two types of instabilities and their characteristics pattern formations develop at the advancing or receding front of a thin liquid film coating the surface of a liquid support. The challenge is to fully characterize the flows from a liquid mechanical point of view and more importantly to use this knowledge to develop practical schemes with which to enhance transport properties and reduce inhomogeneous surface coverage in thin spreading films. Suggestions for such schemes are described. ***