Qiao Yiming, Ma Xiaolei, Liu Zhengyang, Manno Michael A, Keim Nathan C, Cheng Xiang
Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA.
Department of Physics, Pennsylvania State University, University Park, PA 16802, USA.
J Colloid Interface Sci. 2022 Jul 15;618:241-247. doi: 10.1016/j.jcis.2022.03.041. Epub 2022 Mar 14.
Particle-laden fluid interfaces are the central component of many natural and engineering systems. Understanding the mechanical properties and improving the stability of such interfaces are of great practical importance. Janus particles, a special class of heterogeneous colloids, might be used as an effective surface-active agent to control the assembly and interfacial rheology of particle-laden fluid interfaces.
Using a custom-built interfacial stress rheometer, we explore the effect of Janus particle additives on the interfacial rheology and microscopic structure of particle-laden fluid interfaces.
We find that the addition of a small amount of platinum-polystyrene (Pt-PS) Janus particles within a monolayer of PS colloids (1:40 number ratio) can lead to more than an order-of-magnitude increase in surface moduli with enhanced elasticity, which improves the stability of the interface. This drastic change in interfacial rheology is associated with the formation of local particle clusters surrounding each Janus particle. We further explain the origin of local particle clusters by considering the interparticle interactions at the interface. Our experiments reveal the effect of local particle structures on the macroscopic rheological behaviors of particle monolayers and demonstrate a new way to tune the microstructure and mechanical properties of particle-laden fluid interfaces.
含颗粒流体界面是许多自然和工程系统的核心组成部分。理解此类界面的力学性质并提高其稳定性具有重大的实际意义。Janus颗粒是一类特殊的非均相胶体，可用作有效的表面活性剂来控制含颗粒流体界面的组装和界面流变学。
我们使用定制的界面应力流变仪，探究了Janus颗粒添加剂对含颗粒流体界面的界面流变学和微观结构的影响。
我们发现，在单层PS胶体（数量比为1:40）中添加少量铂-聚苯乙烯（Pt-PS）Janus颗粒，可使表面模量增大一个多数量级，同时弹性增强，从而提高了界面的稳定性。界面流变学的这种剧烈变化与每个Janus颗粒周围形成的局部颗粒簇有关。我们通过考虑界面处的颗粒间相互作用，进一步解释了局部颗粒簇的成因。我们的实验揭示了局部颗粒结构对颗粒单层宏观流变行为的影响，并展示了一种调节含颗粒流体界面微观结构和力学性质的新方法。
