Niu Ran, Oğuz Erdal C, Müller Hannah, Reinmüller Alexander, Botin Denis, Löwen Hartmut, Palberg Thomas
Institute of Physics, exp. Soft Matter Group KOMET336, Johannes Gutenberg University, D-55099 Mainz, Germany.
Institute for Theoretical Physics II: Soft Matter, Heinrich-Heine-University, D-40225 Düsseldorf, Germany.
Phys Chem Chem Phys. 2017 Jan 25;19(4):3104-3114. doi: 10.1039/c6cp07231c.
We assemble charged colloidal spheres at deliberately chosen locations on a charged unstructured glass substrate utilizing ion exchange based electro-osmotic micro-pumps. Using microscopy, a simple scaling theory and Brownian dynamics computer simulations, we systematically explore the control parameters of crystal assembly and the mechanisms through which they depend on the experimental boundary conditions. We demonstrate that crystal quality depends crucially on the assembly distance of the colloids. This is understood as resulting from the competition between inward transport by the electro-osmotic pump flow and the electro-phoretic outward motion of the colloids. Optimized conditions include substrates of low and colloids of large electro-kinetic mobility. Then a sorting of colloids by size is observed in binary mixtures with larger particles assembling closer to the ion exchanger beads. Moreover, mono-sized colloids form defect free single domain crystals which grow outside a colloid-free void with facetted inner crystal boundaries centered on the ion exchange particle. This works remarkably well, even with irregularly formed ion exchange resin splinters.
我们利用基于离子交换的电渗微泵，在带电的无结构玻璃基板上特意选择的位置组装带电胶体球。通过显微镜、简单的标度理论和布朗动力学计算机模拟，我们系统地探索了晶体组装的控制参数以及它们依赖于实验边界条件的机制。我们证明晶体质量关键取决于胶体的组装距离。这被理解为是由电渗泵流的向内传输与胶体的电泳向外运动之间的竞争导致的。优化条件包括低电动力学迁移率的基板和高电动力学迁移率的胶体。然后在二元混合物中观察到按尺寸对胶体进行分类，较大的颗粒组装得更靠近离子交换珠。此外，单尺寸胶体形成无缺陷的单畴晶体，这些晶体在无胶体的空隙外生长，其内部晶体边界呈多面形，以离子交换颗粒为中心。即使使用不规则形成的离子交换树脂碎片，这一方法也能显著地发挥作用。
