title: Dynamic self-assembly of rings of charged metallic spheres.
abstract: This Letter describes dynamic self-assembly in a system of stainless steel spheres ( approximately 1 mm in diameter) rolling on a flat dielectric surface under the influence of an external magnetic field that rotates parallel to the plane of the surface. As the spheres move, they charge triboelectrically. Self-assembly is mediated by two types of electrostatic interactions among these charges: (i) attraction between negatively charged regions of the surface and positively charged spheres and (ii) repulsion between the like-charged spheres. The spheres organize into highly ordered rings as a result of these electrostatic interactions.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, USA.
authors.forename: Bartosz A
authors.initials: BA
authors.lastname: Grzybowski
authors.forename: Jason A
authors.initials: JA
authors.lastname: Wiles
authors.forename: George M
authors.initials: GM
authors.lastname: Whitesides