Xu Hui, Lask Mauricio, Kirkwood John, Fuller Gerald
Department of Chemical Engineering, Stanford University, Stanford, California 94305-5025, USA.
Langmuir. 2007 Apr 24;23(9):4837-41. doi: 10.1021/la063593l. Epub 2007 Mar 23.
Particle bridging between a water drop and a flat oil-water interface has been observed when the drop is brought into contact with the interface, leading to the formation of a dense particle monolayer of disc shape (namely, particle disc) that prevents the drop from coalescing into the bulk water phase. Unlike previous observations where particles from opposite interfaces appear to register with each other before bridging, the present experiment demonstrates that the particle registry is not a necessity for bridging. In many cases, the particles from one of the interfaces were repelled away from the contact region, leaving behind the particles from the other interface to bridge the two interfaces. This is confirmed by particle bridging experiments between two interfaces covered with different sized particles, and between a particle-covered interface and a clean interface. The dynamics associated with the growth of the particle disc due to particle bridging follows a power law relationship between the radius of the disc and time: r proportional, variant t0.32+/-0.03. A scaling analysis assuming capillary attraction as the driving force and a hydrodynamic resistance leads to the power law r proportional, variant t1/3, in good agreement with the experiment. In addition, we found that binary mixtures of two different sized particles can undergo phase segregation driven by the particle bridging process.
当水滴与平坦的油水界面接触时，已观察到水滴与该界面之间存在颗粒桥连现象，这导致形成了一个致密的盘状颗粒单层（即颗粒盘），从而阻止水滴聚并到本体水相中。与之前观察到的来自相对界面的颗粒在桥连之前似乎相互对齐的情况不同，本实验表明颗粒对齐并非桥连的必要条件。在许多情况下，来自其中一个界面的颗粒被排斥出接触区域，只留下来自另一个界面的颗粒来桥连两个界面。这在覆盖有不同尺寸颗粒的两个界面之间以及颗粒覆盖界面与干净界面之间的颗粒桥连实验中得到了证实。由于颗粒桥连导致颗粒盘生长的动力学遵循盘半径与时间之间的幂律关系：r 与 t 的 0.32±0.03 次方成正比。假设毛细吸引力为驱动力并考虑流体动力学阻力的标度分析得出幂律 r 与 t 的 1/3 次方成正比，这与实验结果吻合良好。此外，我们发现两种不同尺寸颗粒的二元混合物可在颗粒桥连过程的驱动下发生相分离。
