Colloidal assembly as a tool for adaptive and switchable interfaces

这个项目将有助于通过格子Boltzmann模拟和简单的分析模型来基本理解柔性、自适应甚至可切换衬底上的动态润湿和去湿过程。我们的目标是提出一种策略，利用流体界面上的胶体组装来生成具有复杂几何和润湿性质的“基质”。我们将基于胶体合成和控制方面的最新进展，这些进展导致了具有高度特定特征的粒子的可用性，例如定义明确的形状和表面属性，以及通过外力和场操纵它们的能力。这类粒子的一个例子是片状粒子或Janus粒子，它们描绘了它们的表面属性随位置的变化。它们甚至可以对外部磁场和电场、光或周围流体性质的变化做出刺激反应或反应。附着在流体界面上的这些能力使它们成为有趣的候选者，可以创建与周围液体物种相适应的界面，或者可以通过外部磁场的方式进行切换。例如，由于外力的作用，具有疏水和亲水半球的微尺度Janus粒子的集合可能在界面上旋转，从而动态地改变界面的宏观润湿性质。或者，可以让这些颗粒在界面上自由旋转，这样它们就可以通过简单地最小化其表面能量来优化润湿性能。我们将通过模拟液滴在不同界面上的扩散和润湿动力学来系统地研究这类系统：纯液体界面，具有定义的均匀润湿性和几何形状的颗粒覆盖的界面，以及具有各向异性形状和润湿性质的颗粒。最后，我们将研究如何通过外场来“切换”粒子界面。

This project will contribute to the fundamental understanding of dynamic wetting and dewetting processes on flexible, adaptive and even switchable substrates by means of lattice Boltzmann simulations and simple analytical models. Our aim is to propose strategies utilizing colloidal assembly at fluid interfaces to generate “substrates” with complex geometrical and wetting properties. We will base on recent advances in the synthesis and control of colloids which led to the availability of particles with highly specific features such as well-defined shapes and surface properties together with the ability to manipulate them by external forces and fields. An example for such particles are patchy particles or Janus particles which depict a variation of their surface properties in dependence on the position. They can even be stimuli responsive or react to external magnetic and electric fields, light or changes in the properties of the surrounding fluids. Attached to a fluid interface, these abilities render them interesting candidates to create interfaces which adopt to the surrounding liquid species or can be switched by means of external fields. For example, due to external forces, a collection of microscale Janus particles with hydrophobic and hydrophilic hemispheres might rotate at the interface and thus dynamically change the macroscale wetting properties of the interface. Alternatively, these particles might be let rotate freely at the interface so that they can optimize the wetting properties by simply minimizing their surface energy. We will investigate such systems systematically by simulating the spreading and wetting dynamics of droplets on various interfaces: A pure liquid interface, an interface covered with particles with defined homogeneous wettability and geometry, and particles with anisotropic shape and wetting properties. At last, we will investigate how to “switch” particle-laden interfaces by means of external fields.