Department of Chemical Engineering, Tennessee Tech University, Cookeville, Tennessee 38501, United States.
Langmuir. 2012 Oct 23;28(42):14860-6. doi: 10.1021/la303133y. Epub 2012 Oct 8.
Liquid marbles have opened up several potential applications including biochemical batch reaction engineering and gas sensing. To be successful candidates in these applications, the ability to prepare liquid marbles of controlled sizes and in a continuous process is crucial. This has been the missing link in the science leading to these applications. In the current study, we present a remarkably simple process driven by condensation on a nanoparticulate matrix to continuously produce liquid marbles whose mean size can be controlled in the range of diameters from 3 to 1000 μm, while the distribution width is also controllable independently. We experimentally demonstrate the physics involved in this condensation-driven marble formation process using two fluids-glycerol and ethylene glycol-which span an order of magnitude in viscosity. Hydrophobic fumed silica nanoparticulate material is used as the encapsulating medium owing to its intertwined agglomerate nature. We show that the primary mechanism causing the formation of liquid marbles is droplet nucleation followed by growth driven by condensation. Drop coalescence in dense droplet ensembles is the secondary mechanism, which attempts to destroy the distribution width controllability. From a physics perspective, it will be demonstrated that strong coalescence dominated growth gives rise to a hitherto unreported, significantly higher rate of growth.
液体大理石开辟了多种潜在的应用，包括生化批量反应工程和气体传感。为了在这些应用中成功，能够制备具有受控尺寸的连续过程的液体大理石是至关重要的。这是导致这些应用的科学中的缺失环节。在目前的研究中，我们提出了一种由纳米颗粒基质上的冷凝驱动的非凡简单的过程，以连续生产液体大理石，其平均尺寸可以在 3 到 1000μm 的直径范围内控制，同时分布宽度也可以独立控制。我们使用两种粘度相差一个数量级的流体-甘油和乙二醇-实验性地证明了这种冷凝驱动的大理石形成过程中的物理现象。疏水性烟硅纳米颗粒材料由于其交织的团聚性质而被用作封装介质。我们表明，导致液体大理石形成的主要机制是液滴成核，然后是由冷凝驱动的生长。在密集的液滴聚集体中，液滴聚结是次要机制，它试图破坏分布宽度的可控性。从物理角度来看，将证明强聚结主导的生长导致了迄今未报道的、显著更高的生长速率。
