Oriented assembly of anisotropic particles by capillary interactions

Partially wet anisotropic particles at an otherwise planar fluid interface create distortions as the interface bends to satisfy boundary conditions at the three phase contact line. Overlapping distortions create capillary interactions that depend strongly on the particle shape. Since the excess surface area associated with the distortions can be locally elevated at certain regions near the particle, the resulting capillary interactions drive assembly in preferred orientations. In this work, arguments relating particle aspect ratio to the preferred orientation for assembly are developed for particles of constant cross section. End-to-end registry of particle faces is achieved by exploiting short-range capillary interactions between particles with complex end faces. Finally, insoluble surfactant monolayers are used to arrest the assembly process.