Hydrodynamische Instabilitäten und Strukturbildung bei der Entnetzung

去湿过程中的水动力不稳定性和结构形成

• 批准号: 5108104
• 负责人: Professorin Dr. Karin Jacobs
• 金额: --
• 依托单位: Arbeitsgruppe Jacobs - Experimentalphysik
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 1998
• 资助国家: 德国
• 起止时间: 1997-12-31 至 2006-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/5108104?language=en
• 关键词: Hydrodynamische; Instabilit; ten; und; Strukturbildung

Under what circumstances and in which morphology is a substance at the surface of a given material thermodynamically stable? This question defines the field of research of our project. We will study thin (some nm to some hundreds of nm) liquid films which have been prepared by some special experimental techniques on top of solid substrates. To name an example out of industry, the plastic resist of a CD-ROM disk, prepared by spincoating, must wet the whole disk completely in order to protect safely the stored information. In practice, a lot of effort is put into the achievement of such thermodynamically stable surfaces, for instance roughening the surface and/or applying an adhesive paint. From the scientific point of view, especially the non-equilibrium state is challenging: The way the liquid film reaches its equilibrium state depends on many, mostly yet unknown parameters. The film beads off the surface by a spontaneous symmetry-breaking process and the emerging structures (holes, grooves, etc.), their temporal and spatial development as well as their morphologies lie in the center of our interest.That breaking of the symmetry of the flat, fluid film can proceed via nucleation or via hydrodynamical instabilities. The morphology of the final state is characteristic for the mechanism dominating the breakup. The aim of the project is to find out conditions for the dominance of one of the mechanisms over the other by comparing different systems of variable material classes.Dewetting by hydrodynamical instabilities could be observed in the case of thin metal and thin crystal films. First results demonstrate that liquid crystal films exhibit a complex variety of dewetting patterns, most of them yet of unknown origin. For some cases, we can meanwhile understand their formation and development. For the polymer films dewetting because of nucleation, our studies concentrate on the search for the nuclei and on the investigation of the dynamics of the flow of the nonnewtonian fluid during dewetting. Here, we get strong theoretical support from two groups within the priority program.

在什么情况下以及在哪种形态下，给定材料表面的物质是热力学稳定的？这个问题定义了我们项目的研究领域。我们将研究通过一些特殊的实验技术在固体基底上制备的薄（几纳米到几百纳米）液体薄膜。举一个工业界的例子，通过旋涂法制备的CD-ROM盘的塑料抗蚀剂必须完全润湿整个盘，才能安全地保护存储的信息。在实践中，为了实现这种热力学稳定的表面付出了很多努力，例如使表面粗糙和/或施加粘合涂料。从科学的角度来看，特别是非平衡状态是具有挑战性的：液膜达到平衡状态的方式取决于许多参数，大部分是未知的参数。薄膜通过自发的对称破缺过程从表面脱落，新兴的结构（孔、凹槽等）、它们的时间和空间发展以及它们的形态是我们感兴趣的中心。平面流体薄膜对称性的破坏可以通过成核或通过流体动力学不稳定性来进行。最终状态的形态是主导破裂机制的特征。该项目的目的是通过比较不同材料类别的不同系统，找出其中一种机制相对于另一种机制占主导地位的条件。在薄金属和薄晶体薄膜的情况下，可以观察到流体动力学不稳定性引起的反润湿。初步结果表明，液晶薄膜表现出多种复杂的去湿模式，其中大多数的来源尚不清楚。对于某些事例，我们可以同时了解它们的形成和发展。对于因成核而反润湿的聚合物薄膜，我们的研究集中在寻找核以及研究反润湿过程中非牛顿流体流动的动力学。在这里，我们得到了优先计划内两个小组的强有力的理论支持。