Dynamics of Interfaces Between Drops With Miscible Liquids

在拟议的研究中，我们将通过实验、理论和计算机模拟来研究可混溶液体液滴之间的界面动力学。这项申请的动机是最近对其中一位申请者的实验观察表明，完全可混溶的液体的固着液滴在外围接触后出人意料地不会立即结合(如果它们的接触角足够小)。相反，在横向接触后，一个微观上很薄的液桥连接液滴，推迟液滴的融合。液滴通过这层膜交换液体，但它们仍然是分开的。有时，这部电影可能会变得不稳定，变成脉动的波浪。只有在一段时间后(长达几分钟)，液滴才最终融合为单一液滴，液体才会静止。聚结动力学受表面过程(Marangoni效应)和体流过程(由液体混合引起)的明显影响。具有高接触角的液滴瞬间合并。这表明，颈部拓扑在第一次液滴接触的时刻也是一个重要的参数。在我们的应用程序框架中，我们想要研究不同流体对、不同基质、不同粘度的液滴在特定条件下的聚结行为，以深入了解支配暂时不聚结的机制。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。了解不同液体的混合行为，特别是少量(液滴)的混合行为具有重要的技术意义(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).