Department of Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA.
Soft Matter. 2018 Mar 14;14(11):2131-2141. doi: 10.1039/c7sm02454a.
Wetting, meniscus structure, and capillary interactions for polystyrene microspheres deposited on constant curvature cylindrical liquid interfaces, constructed from nonvolatile ionic or oligomeric liquids, were studied by optical interferometry and optical microscopy. The liquid interface curvature resulted from the preferential wetting of finite width lines patterned onto planar silicon substrates. Key variables included sphere diameter, nominal (or average) contact angle, and deviatoric interfacial curvature. Menisci adopted the quadrupolar symmetry anticipated by theory, with interfacial deformation closely following predicted dependences on sphere diameter and nominal contact angle. Unexpectedly, the contact angle was not constant locally around the contact line, the nominal contact angle varied among seemingly identical spheres, and the maximum interface deviation did not follow the predicted dependence on deviatoric interfacial curvature. Instead, this deviation was up to an order-of-magnitude larger than predicted. Trajectories of neighboring microspheres visually manifested quadrupole-quadrupole interactions, eventually producing square sphere packings that foreshadow interfacial assembly as a potential route to hierarchical 2D particle structures.
通过光学干涉法和光学显微镜研究了沉积在由非挥发性离子或低聚物液体构成的恒曲率圆柱状液体界面上的聚苯乙烯微球的润湿、弯月面结构和毛细相互作用。液体界面曲率是通过优先润湿图案化在平面硅衬底上的有限宽度线产生的。关键变量包括球直径、标称（或平均）接触角和偏界面曲率。弯月面采用了理论预期的四极对称，界面变形紧密遵循预测的与球直径和标称接触角的关系。出乎意料的是，接触角在接触线周围不是局部恒定的，标称接触角在看似相同的球体之间有所不同，最大界面偏差也不遵循预测的与偏界面曲率的关系。相反，这种偏差比预测的要大一个数量级。相邻微球的轨迹直观地显示了四极-四极相互作用，最终产生了方球堆积，预示着界面组装可能是一种制备分层 2D 粒子结构的途径。
