Department of Mechanical Engineering, University of Hong Kong, Pokfulam Road, Hong Kong, China.
Department of Biomedical Engineering, Shenzhen University, Shenzhen 518000, China.
J Colloid Interface Sci. 2022 Feb 15;608(Pt 1):1094-1104. doi: 10.1016/j.jcis.2021.09.187. Epub 2021 Oct 12.
The coalescence of bare droplets when surface tension dominates always results in one larger spherical droplet. In contrast, droplets coated with particles may be stabilized into non-spherical structures after arrested coalescence, which can be achieved by different approaches, such as changing the particle surface coverage. The size of particles coating the initial liquid marbles can be used to control the coalescence dynamics and the resulting morphology of arrested droplets.
We characterized the electrocoalescence of liquid marbles coated with particles ranging from hundred nanometers to hundred micrometers. The electrocoalescence was recorded using high-speed imaging.
When the electrocoalescence initiates, particles jam and halt the relaxation of the marbles at different stages, resulting in four possible final morphologies that are characterized using the Gaussian curvature at the neck region. The four regimes are total coalescence, arrested puddle coalescence, arrested saddle coalescence, and non-coalescence. The coalescence is initiated at the center of the contact zone, independent of the particle size. Small particles show little resistance to the coalescence, while marbles coated by large particles demonstrate a viscous-like behavior, indicated by the growth of the liquid bridge and the damping. The present study provides guidelines for applications that involve the formulation of liquid marbles with complex morphologies.
当表面张力占主导地位时，裸露液滴的聚并总是导致一个更大的球形液滴。相比之下，涂覆有颗粒的液滴在聚并后可能会由于颗粒的存在而被稳定成非球形结构，这可以通过改变颗粒表面覆盖率等不同方法来实现。涂覆初始液滴的颗粒的大小可以用来控制聚并动力学和被截留液滴的最终形态。
我们对涂覆有从几百纳米到几百微米的颗粒的液滴的电聚并进行了表征。使用高速成像记录了电聚并。
当电聚并开始时，颗粒在不同阶段阻碍和阻止了液滴的松弛，导致在颈部区域的高斯曲率的特征下，存在四种可能的最终形态。这四个区域是完全聚并、截留液池聚并、截留鞍状聚并和不聚并。聚并在接触区域的中心开始，与颗粒大小无关。小颗粒对聚并几乎没有抵抗力，而大颗粒涂覆的液滴表现出粘性行为，这表现为液桥的增长和阻尼。本研究为涉及具有复杂形态的液滴制剂的应用提供了指导。
