Dynamics of Interfaces Between Drops With Miscible Liquids

在本研究中，我们将借由实验、理论及电脑模拟来探讨可混溶液体液滴间界面的动力学。本申请的动机是申请人之一最近的实验观察，其显示完全可混溶的液体的固着液滴在外周接触后（如果它们的接触角足够小的话）意外地不会立即聚结。相反，在横向接触之后，微观上薄的液体桥连接液滴并延迟液滴融合。液滴通过该膜交换液体，但它们保持分离。有时候，这层薄膜会不稳定，变成脉动波。只有在一段时间后（最多几分钟），液滴才最终合并成一个液滴，液体才能静止。聚结动力学明显受到表面（Marangoni效应）和整体流动过程（由液体混合引起）的影响。具有高接触角的液滴瞬间聚结。这表明，在第一液滴接触的时刻的颈部拓扑结构也是一个重要的参数。在我们的应用程序的框架中，我们希望研究液滴在定义条件下的聚结行为，用于不同的流体对，不同的基质，不同的粘度，以深入了解控制暂时不聚结的机制。实验将通过基于润滑和相场理论的模型计算和模拟来补充。理解不同液体的混合行为，特别是少量（液滴）的混合行为具有很大的技术重要性（例如在微流体中）。

In the proposed research we will investigate the dynamics of interfaces between droplets of miscible liquids by experiment, theory and Computer simulations. This application is motivated by the recent experiment al observation of one of the applicants showing that sessile droplets of completely miscible liquids do unexpectedly not instantaneously coalesce after peripheral contact (if their contact angles are sufficiently small). Instead, after lateral contact, a microscopically thin liquid bridge connects the droplets and delays the droplet fusion. The droplets exchange liquid through this film, but they remain separated. Occasionally this film can destabilize into pulsating waves. Only after some time (up to minutes) the droplets finally merge into a single droplet and the fluid comes to rest. The coalescence dynamics is obviously influenced by surface (Marangoni effect) and bulk flow processes (which are induced by the liquid mixing). Droplets with high contact angles coalesce instantaneously. This shows that the neck topology in the moment of the first droplet contact is also an important parameter. In the framework of our application we want to investigate the coalescence behavior of droplets under defined conditions for different pairs of ifluids, different Substrates, different viscosities, to gain insight into the mechanisms, which govern the temporary non-coalescence. The experiments will be complemented by model calculations and simulations based on the lubrication and phase field theory. The understanding of the mixing behavior of different liquids, in particular that of small quantities (droplets) is of great technical importance (e.g. in micro-fluidics).