Holzner Gregor, Binder Claudia, Kriel Frederik H, Priest Craig
Future Industries Institute, University of South Australia , Mawson Lakes 5095, South Australia, Australia.
Institute of Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich , Vladimir-Prelog-Weg 1, CH-8093 Zurich, Switzerland.
Langmuir. 2017 Feb 14;33(6):1547-1551. doi: 10.1021/acs.langmuir.6b04026. Epub 2017 Feb 1.
We report directed growth of orthorhombic crystals of potassium permanganate in spatial confinement of a micropillar array. The solution is introduced by spontaneous wicking to give a well-defined film (thickness 10-15 μm; volume ∼600 nL) and is connected to a reservoir (several microliters) that continuously "feeds" the evaporating film. When the film is supersaturated, crystals nucleate and preferentially grow in specific directions guided by one of several possible linear paths through the pillar lattice. Crystals that do not initially conform are stopped at an obstructing pillar, branch into another permitted direction, or spontaneously rotate to align with a path and continue to grow. Microspectroscopy is able to track the concentration of solute in a small region of interest (70 × 100 μm) near to growing crystals, revealing that the solute concentration initially increases linearly beyond the solubility limit. Crystal growth near the region of interest resulted in a sharp decrease in the local solute concentration (which rapidly returns the concentration to the solubility limit), consistent with estimated diffusion time scales (<1 s for a 50 μm length scale). The ability to simultaneously track solute concentration and control crystal orientation in nanoliter samples will provide new insight into microscale dynamics of microscale crystallization.
我们报道了在微柱阵列的空间限制内高锰酸钾正交晶体的定向生长。溶液通过自发毛细作用引入，形成定义明确的薄膜（厚度10 - 15μm；体积约600 nL），并连接到一个储液器（几微升），该储液器持续“供应”正在蒸发的薄膜。当薄膜达到过饱和时，晶体会成核，并在由穿过柱晶格的几种可能线性路径之一引导的特定方向上优先生长。最初不符合的晶体在阻碍柱处停止，分支到另一个允许的方向，或自发旋转以与路径对齐并继续生长。显微光谱能够追踪靠近生长晶体的小感兴趣区域（70×100μm）内溶质的浓度，揭示溶质浓度最初在超过溶解度极限后呈线性增加。感兴趣区域附近的晶体生长导致局部溶质浓度急剧下降（迅速将浓度恢复到溶解度极限），这与估计的扩散时间尺度（50μm长度尺度下<1 s）一致。在纳升样品中同时追踪溶质浓度和控制晶体取向的能力将为微观尺度结晶的微观动力学提供新的见解。
