Segregation in Drying Binary Colloidal Droplets
Segregation in Drying Binary Colloidal Droplets
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DOI：
10.1021/acsnano.9b00459
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发表时间：
2019-05-01
期刊：
影响因子：
17.1
通讯作者：
Nikoubashman, Arash
中科院分区：
文献类型：
--
作者：
Liu, Wendong;Midya, Jiarul;Nikoubashman, Arash
当胶体悬浮液滴从固体表面蒸发时，它会在接触区域留下特征沉积物。这些沉积物对于印刷、涂层或洗涤等许多应用来说是常见且重要的。通过使用超双疏表面作为基底，可以减少接触面积，使得蒸发几乎是径向对称的。干燥时，液滴保持近乎完美的球形。在这里，我们利用这种现象从双分散胶体水悬浮液中制造超颗粒。超粒子具有核壳形态。外部区域主要被小胶体占据，形成密堆积的晶体结构。朝中心方向，大胶体的数量增加，并且它们呈无定形堆积。这种分层的程度随着蒸发速率的降低而降低。补充模拟表明，蒸发导致密度局部增加，进而对较大的胶体施加更强的向内力。实验和模拟之间的比较表明，悬浮胶体之间的流体动力相互作用减少了分层程度。我们的研究结果与超颗粒的制造相关，这些超颗粒可用于色谱、催化、药物输送、光子学以及更好地理解喷雾干燥领域。
When a colloidal suspension droplet evaporates from a solid surface, it leaves a characteristic deposit in the contact region. These deposits are common and important for many applications in printing, coating, or washing. By the use of superamphiphobic surfaces as a substrate, the contact area can be reduced so that evaporation is almost radially symmetric. While drying, the droplets maintain a nearly perfect spherical shape. Here, we exploit this phenomenon to fabricate supra particles from bidisperse colloidal aqueous suspensions. The supraparticles have a core shell morphology. The outer region is predominantly occupied by small colloids, forming a close-packed crystalline structure. Toward the center, the number of large colloids increases and they are packed amorphously. The extent of this stratification decreases with decreasing the evaporation rate. Complementary simulations indicate that evaporation leads to a local increase in density, which, in turn, exerts stronger inward forces on the larger colloids. A comparison between experiments and simulations suggest that hydrodynamic interactions between the suspended colloids reduce the extent of stratification. Our findings are relevant for the fabrication of supraparticles for applications in the fields of chromatography, catalysis, drug delivery, photonics, and a better understanding of spray-drying.