Ian Wark Research Institute, University of South Australia, Mawson Lakes, South Australia 5095, Australia.
J Colloid Interface Sci. 2011 Nov 1;363(1):301-6. doi: 10.1016/j.jcis.2011.07.060. Epub 2011 Jul 27.
The formation and stability of drops in the presence of nanoparticles was studied in a microfluidic device to directly observe the early stages of Pickering emulsification (low interfacial coverage). We observed several key differences between oil droplet necking and rupture in aqueous phases of nanoparticles (methylated silica) and well-characterised surfactant systems. The presence of particles did not influence drop formation dynamics and thus the size of the drops generated. In addition, observations of in-channel drop stability shortly after formation (several milliseconds) indicated that particles in the aqueous phase slow film thinning processes, but do not prevent coalescence. In contrast, downstream collection and densification (at the microchannel outlet), showed that particle-stabilised drops do not coalesce for several weeks, above a critical particle concentration. The implications of our results for droplet microfluidics and our understanding of conventional emulsification systems are discussed.
在微流控装置中研究了纳米颗粒存在下液滴的形成和稳定性，以直接观察皮克林乳液（低界面覆盖）的早期阶段。我们观察到油滴颈缩和破裂与纳米颗粒（甲基化二氧化硅）和经过充分表征的表面活性剂体系的水相之间存在几个关键差异。颗粒的存在并不影响液滴形成动力学，因此生成的液滴大小也不受影响。此外，在形成后几毫秒（几毫秒）对通道内液滴稳定性的观察表明，水相中的颗粒会减缓成膜变薄过程，但不能阻止聚结。相比之下，下游的收集和浓缩（在微通道出口处）表明，在临界颗粒浓度以上，颗粒稳定的液滴在数周内不会聚结。我们的结果对液滴微流控技术和我们对传统乳化系统的理解具有重要意义。
