Heterogeneous nucleation and microstructure formation in binary colloidal systems

我们实验研究了二元二维超顺磁胶体体系的非均相成核和随后的微观结构形成。原子核成核是由旋转的外磁场引起的，这使得粒子相互作用和相应的成核势垒发生了系统的变化。结合由声光偏转系统控制的扫描光镊，我们可以配置大粒子的任何初始位置，作为小粒子的成核种子。此外，可以创建任意形状和大小的成核中心。由于成核是由外部场引发的，因此在一个明确定义的瞬间开始，这使我们能够探索从均匀初始状态到奥斯特瓦尔德成熟和微观结构形成的非常晚阶段的非均质成核的完整时间发展。

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.