(353a) Anisotropic Particle Migration and Assembly At Fluid Interfaces

As a community, our ability to create particles with well-defined shapes and surface energies is now well established, driving the need for assembly schemes to create new materials.   In my group, we have focused on the role of shape anisotropy in capillary-driven assembly.  On planar interfaces, far from contact, particles of arbitrary shape interact as capillary quadrupoles.  Near contact, rod-like particles interact and assemble in a manner that depends strongly on particle shape.  We demonstrate this dependence by comparing right circular cylinders, ellipsoids, and super-ellipsoids in terms of their preferred orientations and the mechanics of the microstructures formed when they assemble.  On curved interfaces, rod-like particles migrate to highly curved sites to form hierarchical assemblies influenced by both particle-particle interactions and the energy owing to the interfacial curvature field.  At the microscale, all of these capillary interactions are remarkably strong, and the structures that they form are often kinetically trapped. Strategies to impart near field repulsion between particles are described.