Confinement-induced columnar crystals of shape-anisotropic particles: A route to new architecture in the scientific world

Identical spheres in cylindrical confinement exhibit a complex variety of densest-packed columnar structures [1]. Such densest-packed structures can serve as theoretical models for the structures of a variety of quasi-one-dimensional physical systems, such as nanotube-confined fullerenes, nanochannel-confined copolymers, colloidal crystal wires, capillary-tube confined thermoresponsive microspheres, capillary-tube confined microbubbles, and fluid-driven self-assemblies of polymer beads. On the other hand, there have been comparatively few studies of this kind for shape anisotropic particles. Thanks to their rotational degrees of freedom, shape-anisotropic particles in cylindrical confinement exhibit densest-packed structures with non trivial orientational order, and therefore they demonstrate a greater variety of densest-packed crystal structures than their spherical counterparts. In this talk, I will present a variety of densest-packed columnar crystals as discovered recently for identical spheroids in cylindrical confinement [2] and for identical ellipses within a parallel strip [3]. For the case of spheroids, I will explain how the corresponding densest-packed structures arise from a competition between confinement-induced chiral ordering and shape anisotropy-induced orientational ordering. For the case of ellipses, I will explain why the corresponding densest packed structures are all affine transformations of particular densest-packed structures of circular disks. It is believed that the confinement-induced crystal structures presented in this talk could constitute a basis for the development of novel low-dimensional materials with tailored translational or orientational order.