An experimental study of columnar crystals using monodisperse microbubbles

We investigate the ordered arrangements of monodisperse microbubbles confined within narrow cylinders. These foams were imaged using X-ray tomography, allowing the 3D positions of the bubbles of the foam to be accurately determined. The structure of these foams closely resemble the minimum energy configuration of hard spheres in cylindrical confinement as found in simulations. For larger ratios, lambda, of cylinder to bubble diameter two- and three-layered crystals were formed. Each layer of these structures is found to be ordered, with each internal layer resembling structures found at lower lambda values. The average number of contacts per bubble is seen to increase with lambda. (C) 2015 Elsevier B.V. All rights reserved.