Heterogeneous nucleation and microstructure formation in binary colloidal systems

我们实验研究了二元二维超顺磁性胶体体系中的异质成核和随后的微结构形成。核化是由旋转的外部磁场引起的，它允许粒子相互作用和相应的成核势垒的系统变化。结合由声光偏转系统控制的扫描光镊，我们可以配置较大颗粒的任何初始位置，这些较大颗粒充当较小颗粒的成核种子。此外，可以产生具有任意形状和尺寸的成核中心。由于成核是由一个外部的字段，从而在一个明确的瞬间设置，这使我们能够探索从一个均匀的初始状态开始，直到奥斯特瓦尔德成熟和微观结构形成的非常后期阶段的非均质成核的全时间发展。

We experimentally investigate heterogeneous nucleation and subsequent microstruc-ture formation in binary two-dimensional super paramagnetic colloidal systems. Nu-cleation is induced by rotating external magnetic fields which allows the systematic variation of the particle interactions and the corresponding nucleation barriers. In combination with scanning optical tweezers being controlled by acoustic-optical de-flection systems we can configure any initial position of the bigger particles which act as nucleation seeds for the smaller ones. In addition, nucleation centers with arbitrary shapes and sizes can be created. Because nucleation is initiated by an external field and thus sets in at a well-defined instant, this allows us to explore the full temporal development of heterogeneous nucleation starting from a homogeneous initial state until the very late stages of Ostwald ripening and microstructure formation.